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Toxicity of nanoparticles
Abstract
This chapter summarizes the most important applications of nanotechnology in the construction industry together with aspects of nanoparticles toxicity. Nanotechnology is currently applied in the construction industry predominantly in cement, coatings, paints and insulating materials. Nanoparticles incorporated into existing construction materials confer them novel and extraordinary properties, such as increased strength, self-sensing, self-cleaning, antimicrobial, or pollution remediation capabilities. On the other hand, nanoparticles from construction materials that are released into the environment can be extremely detrimental to health. Nanoparticles can enter the human body via inhalation, ingestion, or skin contact. The range of pathologies related to exposure to nanoparticles encompasses respiratory, cardiovascular, lymphatic, autoimmune, neurodegenerative diseases, and a variety of cancers that can manifest immediately following exposure or many years later.
... [12,13] However, it is noticed that nanoparticles (transition metals and their compounds) have inherent toxicity which causes substantial hazardous impact on flora and fauna. [21] Due to small-size and large surface area of nanoparticles, these can be effortlessly migrated into the living system and deposited into various parts of the body of organism(s). [21] Thereby important issues like stability, biocompatibility and long-term toxicity should be tackled and checked in cases of both in vivo and in vitro applications.Normally the cell lines provide an excellent reduced live system to assess the toxicity of nanoparticles as most of the assay systems like cell viability, counting and fluorescence measurements can be easily performed on them. ...
... [21] Due to small-size and large surface area of nanoparticles, these can be effortlessly migrated into the living system and deposited into various parts of the body of organism(s). [21] Thereby important issues like stability, biocompatibility and long-term toxicity should be tackled and checked in cases of both in vivo and in vitro applications.Normally the cell lines provide an excellent reduced live system to assess the toxicity of nanoparticles as most of the assay systems like cell viability, counting and fluorescence measurements can be easily performed on them. Therefore, most studies have employed cell line-based methods for the toxicity assessment of nanoparticles. ...
... Both morphological and anatomical structures are studied for the assessment of the toxic impact of RE 3 + -doped nanoparticles. [21] The morphological assessment was made using bright-field optical imaging of pericardial area, yolk sac, yolk tube, air-bladder, tail etc. For the anatomical assessment, skeletal muscle integrity is imaged. ...
An ionic liquid (IL)‐based solvothermal method is employed to prepare single‐phase, luminescent, cubic rare‐earth doped and silica‐coated BaF2 nanomaterials. High energy transfer efficiency (∼60%) from Ce³⁺ to Tb³⁺ for BaF2:Ce³⁺/Tb³⁺ nanoparticles dispersed in DMSO solution is observed. Furthermore, for the first time to the best of our knowledge, as‐prepared RE ion/s doped and silica‐coated BaF2 nanoparticles are used for the toxicological assessment on live zebrafish larvae. Interestingly, static exposure of these nanoparticles from 6 hpf till 96 hpf period at high concentration (70 mg/L) do not show any developmental anomalies as judged by bright‐field and birefringence optical imaging method which promises its large‐scale applications in imaging and other biological purposes.However, as a positive control, cypermethrin‐based pesticide could induce developmental defects at 0.1 mg/L concentration. It is worth mentioning that the concentration of BaF2 nanoparticles chosen in present study is much higher than the other nanoparticles reported so far.
... Nanoparticles are also used in the construction industry (Pacheco-Blandino et al., 2012). Nanoparticles can be incorporated as nanocomposites in concrete. ...
... Iron oxide nanoparticles incorporated in construction materials can offer self-sensing capabilities as well. Coating with different nanoparticles can greatly improve the properties of the covered material (Pacheco-Blandino et al., 2012). For example, photocatalytic TiO 2 and ZnO nanoparticles are used for pollution remediation, for their antifog, anticorrosion and antimicrobial properties. ...
... Cu and Zn nanoparticles in coatings are anticorrosive, Ag, Cu are antimicrobial. Silica nanoparticle coatings are scratch resistant, fireproof, and antireflective, while W 2 O 3 can be used in coatings to adjust light transmittance (Pacheco-Blandino et al., 2012). ...
This chapter gives information on nanoparticle classification and their origin. The two main classes of nanoparticles are from natural and anthropogenic sources. Natural nanoparticles existed on earth since millennia from wind erosion and dust storms, volcanic activity and from biogenic sources. Recently large amounts of anthropogenic nanoparticles are being intentionally and unintentionally released into the environment. Nanoparticles are being used today as pesticides and fertilizers, for water and soil remediation. Due to their special properties compared to bulk counterparts, nanoparticles are used in today in many products. Accidental release of nanoparticles occurs from an increasing number of products that contain nanoparticles as well as a by-product of incomplete combustion as a result of automobiles and industry. Many studies show that nanoparticles are toxic to humans and animals; however, there is a lack of regulations regarding the use of nanoparticles, many being researched and patented for use in agriculture, food industry, and various consumer products.
... The main phenomena of NSMs occur at the surface, meaning that the total surface should be considered in terms of toxicology [14]. The aspect ratio determines the internalization rate of a particle, and as the aspect ratio increases, toxicity increases as well [15]. Nanoparticles defined as having a high aspect ratio include nanotubes and nanowires, varying in shape and length. ...
... High-aspect ratio: nanotubes and nanowires. Morphology [1,4,14,15] Flatness, sphericity and aspect ratio Low-aspect ratio: spherical, oval, cubic, prism, helical or pillar morphologies. ...
Nanoparticles (NPs) have unique physicochemical properties that are useful for a broad range of biomedical and industrial applications; nevertheless, increasing concern exists about their biosafety. This review aims to focus on the implications of nanoparticles in cellular metabolism and their outcomes. In particular, some NPs have the ability to modify glucose and lipid metabolism, and this feature is especially interesting to treat diabetes and obesity and to target cancer cells. However, the lack of specificity to reach target cells and the toxicological evaluation of nontargeted cells can potentially induce detrimental side effects, closely related to inflammation and oxidative stress. Therefore, identifying the metabolic alterations caused by NPs, independent of their application, is highly needed. To our knowledge, this increase would lead to the improvement and safer use with a reduced toxicity, increasing the number of available NPs for diagnosis and treatment of human diseases.
... Currently, nanoparticle toxicity is a major concern, as many studies have reported its negative effects on health and the environment [39]. Antimony (Sb) [40] is a toxic trace element. ...
Biofilms are responsible for persistent or recurring microbial infections. Polymicrobial biofilms are prevalent in environmental and medical niches. Dual-species biofilms formed by Gram-negative uropathogenic Escherichia coli (UPEC) and Gram-positive Staphylococcus aureus are commonly found in urinary tract infection sites. Metal oxide nanoparticles (NPs) are widely studied for their antimicrobial and antibiofilm properties. We hypothesized that antimony-doped tin (IV) oxide (ATO) NPs, which contain a combination of antimony (Sb) and tin (Sn) oxides, are good antimicrobial candidates due to their large surface area. Thus, we investigated the antibiofilm and antivirulence properties of ATO NPs against single- and dual-species biofilms formed by UPEC and S. aureus. ATO NPs at 1 mg/mL significantly inhibited biofilm formation by UPEC, S. aureus, and dual-species biofilms and reduced their main virulence attributes, such as the cell surface hydrophobicity of UPEC and hemolysis of S. aureus and dual-species biofilms. Gene expression studies showed ATO NPs downregulated the hla gene in S. aureus, which is essential for hemolysin production and biofilm formation. Furthermore, toxicity assays with seed germination and Caenorhabditis elegans models confirmed the non-toxic nature of ATO NPs. These results suggest that ATO nanoparticles and their composites could be used to control persistent UPEC and S. aureus infections.
... Advantages in the field of nanoscience and nanotechnology have led to the synthesis of wide range of nanoparticles and nanostructured materials. Particles with at least one dimension in 1À1000 nm are known as nanoparticles, where the properties drastically change when the particles are in the size of 1À100 nm [20]. In another study, the nanoparticles are defined as the nanosized objects with external three dimensions, where the nanoobjects with distinct longest and the shortest lengths in the axes are known as nanorods and nanoplates [18]. ...
Bionanomaterials are identified as a perfect replacement, in the quest for the search of an alternative to toxic conventional nanomaterials for biomedical applications. Bionanomaterials are the nanomaterials that are fabricated via biomolecules or encapsulate or immobilize a conventional nanomaterial with a biomolecule. The biomolecules extracted from the microbes, plants, agricultural wastes, insects, marine organisms, and certain animals are used for the formation of bionanomaterials. These bionanomaterials exhibited low or negligible toxicity toward humans, other organisms, and the environment with enhanced biocompatibility, bioavailability, and bioreactivity. Thus the aim of this chapter is to provide an extensive overview of bionanomaterials, their definitions, sources, types, and their properties. In addition, the toxicity of bionanomaterials and their regulations implied in recent times are also discussed.
... The presence of NMs in the air can damage soil fertility, marine life, and uncontaminated water bodies and contribute to increasing environmental issues such as dust cloud formation and the stratospheric temperature. The physiochemical properties of NMs, such as size, surface area, shape, charge, aggregation, and so on, have an impact on their toxicity [1,3,4]. NMs can veer toward agricultural and water resources when exposed to the environment. ...
The most active research area is nanotechnology in cementitious composites, which has a wide range of applications and has achieved popularity over the last three decades. Nanoparticles (NPs) have emerged as possible materials to be used in the field of civil engineering. Previous research has concentrated on evaluating the effect of different NPs in cementitious materials to alter material characteristics. In order to provide a broad understanding of how nanomaterials (NMs) can be used, this paper critically evaluates previous research on the influence of rheology, mechanical properties, durability, 3D printing, and microstructural performance on cementitious materials. The flow properties of fresh cementitious composites can be measured using rheology and slump. Mechanical properties such as compressive, flexural, and split tensile strength reveal hardened properties. The necessary tests for determining a NM’s durability in concrete are shrinkage, pore structure and porosity, and permeability. The advent of modern 3D printing technologies is suitable for structural printing, such as contour crafting and binder jetting. Three-dimensional (3D) printing has opened up new avenues for the building and construction industry to become more digital. Regardless of the material science, a range of problems must be tackled, including developing smart cementitious composites suitable for 3D structural printing. According to the scanning electron microscopy results, the addition of NMs to cementitious materials results in a denser and improved microstructure with more hydration products. This paper provides valuable information and details about the rheology, mechanical properties, durability, 3D printing, and microstructural performance of cementitious materials with NMs and encourages further research.
... Therefore, on the basis of available experimental models, it may be inaccurate to list some of the more valuable NPs as being toxic to biological systems and vice versa. Considering the potential applications of NPs in many fields and to address the knowledge gap, the relevant toxic effects of NPs should be assessed by utilizing internationally agreed and unbiased in vivo toxicological models, targeting the vital systems (Pacheco-Blandino et al., 2012). However, we are of the opinion that designing, adapting, and validating such new models in the future for toxicity testing, route of exposure, coating material and sterility of NPs, and type of cell cultures need to be carefully examined (Crisponi et al., 2017). ...
Currently, the significance of fungi as human pathogens is not medically concealed in the world. Consequently, suitable recognition and treatment of such infections are of great importance and necessitate the need for comprehensive information in this regard. The introduction of new antifungals and their use today, especially in the last two decades, have revolutionized the treatment of fungal infections. On the other hand, increasing drug resistance in the world has overshadowed such developments. The use of NPs results in the treatment of fungal infections and owing to their specific properties, these particles, unlike the pure antibiotics, can exert a greater inhibitory power although with less concentration compared with conventional drugs. Important reasons that have led to the use of antifungal drugs in delivery systems include reduced drug efficacy, limited penetration through tissue, poor aqueous solubility, decreased bioavailability, and poor drug pharmacokinetics. It is therefore hoped that unfavorable properties of antifungal drugs be mitigated via their incorporation into different types of NPs. This review summarizes the different types of NPs as delivery systems of antifungal as well as their advantages over pure drugs.
... Inhaling PM 0.1 inflicts severe risks to a given population, where the lung is the primary target organ [5]. Pollution from PM at this aerodynamic diameter can easily pass through the throat and into the deeper cavities of the lung [6]. ...
... Furthermore, we must emphasize that carbon nanotubes are not materials capable of delivering volatile substances into the environment, although they are still nano-materials. They must always be used with caution avoiding any dispersion [37][38][39]. Another important objective was to find a sustainable solvent that would allow the preparation of a glue based on a resin that can be applied when cold, unlike procedure for resin based glues that must be first heated and then put into action function quickly before cooling and solidification. ...
The main purpose of this work was to prepare and optimize glues consisting primarily of natural components. The fundamental component was the laricio pine resin to which different additives were added, varying their nature and quantity. The additives used were: charcoal, activated carbon and carbon nanotubes (MWCNTs). The optimization of the systems continued to identify and select suitable solvents, in order to improve dispersion and solubilization of the phases and to obtain glues in the fluid phase at room temperature. The best results were obtained with ethyl alcohol which, moreover, represents a solvent with a limited environmental impact. The evaluation of the adhesive capacity of the glues was carried out by cutting, tensile and flexural tests on prepared wooden specimens. Furthermore, the specimens and the same glue were subjected to thermal cycles and observed by Scanning Electron Microscope (SEM). The carbon nanotubes, used in very low percentages (1%, in a system consisting mainly of natural origin products) in the presence of an adequate solvent, such as ethyl alcohol, make it possible to obtain a glue that is easy to apply, with an excellent adhesive capacity.
... Unfortunately, these obvious differences in physical properties come together with differences in impacts on human health. Researchers on microparticles have already remarked that nanoparticles are likely to impact the human body similarly to microparticles, such as asbestos (Donaldson and Poland, 2012;Sanchez et al., 2009;Pacheco Blandino et al., 2012). If learning from the experiences with asbestos, the problem would seem to be the shape and size of particles and their biopersistency within the human body. ...
Systematic literature reviews originated in biomedical science. They are methods to systematically identify, select and critically appraise evidence. They form the foundation of the process reported here which has investigated whether there is any evidence in the literature showing that biomimicry might be a generalizable principle that could assist designers to improve the thermal performance of buildings. In its defining papers biomimetic design is argued to be an applied science that derives inspiration from the natural world and opens avenues for technological/sustainable design and innovation. It suggests that study of nature can reveal more sustainable solutions in terms of efficient processes, functions, systems and materials. For example, thermal adaptation of natural organisms to extreme conditions takes place through behavioural, morphological and physiological mechanisms. However, the literature review has revealed that there is no publication outlining a systematised procedure to attribute thermal issues to corresponding natural adaptation strategies applied by specific organisms. Biomimetic design concepts often seem to be written about with very specific examples which seem more to be about the metaphorical use of one-off examples of nature-inspired design than about a general approach to the mining of biological information systems for design inspiration.
... Although the use of nanoparticles is very recent, it has already raised issues concerning its potential toxicity. Some investigations showed that nanoparticles can cause symptoms like the ones caused by asbestos fibres [14,15]. Therefore, during the mortar mixing masks and gloves were used to avoid contact with the nano-TiO 2 powder. ...
The self-cleaning ability of photocatalytic cement-based materials has the potential to preserve the esthetic appearance of building facades over time thus reducing cleaning costs. In the present work , the joint effect of several factors on the mechanical strength and self-cleaning ability of photocatalytic mortars was studied. For this purpose, four different mortar mixes containing two binder/sand ratios (1:3 and 1:4) were analyzed. Two mixes containing only Portland cement and the other two possessing 50% Portland cement and 50% aerial lime. For each mix, four different compositions were manufactured, each one with a different titanium dioxide-TiO2 content (0%, 2%, 4% and 6%). The results show that w/b increases with TiO2 which, in turn, leads to lower mechanical strength. Results also show that the mixes with 2% TiO2 had the highest self-cleaning effect.
... Unfortunately, there are already warnings about nanoparticles. Researchers have remarked that nanoparticles are likely to impact the human body similarly to microparticles, the best known of these being the asbestos family Pacheco-Blandino et al., 2012). If learning from the experiences with asbestos, the problem would seem to be the shape and size of particles and their biopersistency within the human body. ...
Principles for Evaluating Building Materials in Sustainable Construction: Healthy and Sustainable Materials for the Built Environment provides a comprehensive overview of the issues associated with the selection of materials for sustainable construction, proposing a holistic and integrated approach.
The book evaluates the issues involved in choosing materials from an ecosystem services perspective, from the design stage to the impact of materials on the health of building users.
The three main sections of the book discuss building materials in relation to ecosystem services, the implications of materials choice at the design stage, and the impact of materials on building users and their health. The final section focuses on specific case studies that illustrate the richness of solutions that existed before the rise of contemporary construction and that are consistent with a sustainable approach to creating built environments. These are followed by modern examples which apply some, if not all, of the principles discussed in the first three sections of the book.
... There are numerous applications of nanoparticles, among which are industrial applications (Stark et al., 2015), in the construction industry in cement, coatings, paints and insulating materials (Pacheco Blandino et al., 2012), as electrocatalysts (Anderson et al., 2015b), for advanced energy conversion and storage (Dai et al., 2012), , in functionalized textiles (Anghel et al., 2012), in food contact material (Hannon et al., 2015), in cosmeceutical treatments for conditions such as photoaging, hyperpigmentation, wrinkles (Lohani et al., 2014). ...
In this chapter, we present a general classification of nanomaterials based on their dimensionality, shape, and composition. According to their dimensionality, nanomaterials include nanoparticles, nanotubes, and nanofilms. Nanomaterials can be made of single elements, such as metals or carbon, or multiple elements, such as metal oxides or composites. We review the most used types of nanomaterials up to date showing examples of their morphologies. The physicochemical properties of a material in nanoform can be very different from its bulk counterpart, depending not only on the type of materials, but on its size, shape, and functionalization. We discuss the most important physicochemical properties of nanomaterials, among which are morphology, dispersability, crystalline phase, melting temperature, and magnetic properties.
... However, these facts also bring some doubts concerning their safety, thus being a demand to assess their health effects before proceeding with incorporation in food products or industrial production ( Smolkova et al., 2015). Some nanostructures, depending on their composition and size, showed irreversible damage to cells by oxidative stress or/and organelle injury ( Buzea et al., 2007), showing the need of understanding the toxicological hazards associated with the nanostructured systems, and possible toxic effects in human health when used in food products ( Pacheco-Torgal et al., 2012). Human skin, lungs, and GIT are in constant contact with the environment. ...
Nanotechnology is pointed to as one of the hot topics in food science and technology where the use of nanostructured systems for compounds delivery using biobased materials appears as one of the most interesting matters in the field. Due to their advantages when compared with micro- and macroscale systems, nanostructured biobased systems have attracted a great interest from academia and industry where they can be used as a delivery system of nutrients and bioactive compounds.
This chapter focuses on the design and production of nanostructured systems (eg, nanoparticles, nanohydrogels, and nanoemulsions), where the ingredients used in production techniques and predominant forces for their development are explored. The use of these systems for the delivery of nutrients and bioactive compounds are discussed regarding their affinity and interaction with the systems and the influence on their final properties (eg, retention and controled release).
Finally an insight of the systems behavior in human gastrointestinal tract and their possible toxity are presented.
The problem of ultrafine particles (UFPs; PM0.1) has been prevalent since the past decades. In addition to become easily inhaled by human respiratory system due to their ultrafine diameter (<100 nm), ambient UFPs possess various physicochemical properties which make it more toxic. These properties vary based on the emission source profile. The current development of UFPs studies is hindered by the problem of expensive instruments and the inexistence of standardized measurement method. This review provides detailed insights on ambient UFPs sources, physicochemical properties, measurements, and estimation models development. Implications on health impacts due to short-term and long-term exposure of ambient UFPs are also presented alongside the development progress of potentially low-cost UFPs sensors which can be used for future UFPs studies references. Current challenge and future outlook of ambient UFPs research are also discussed in this review. Based on the review results, ambient UFPs may originate from primary and secondary sources which include anthropogenic and natural activities. In addition to that, it is confirmed from various chemical content analysis that UFPs carry heavy metals, PAHs, BCs which are toxic in its nature. Measurement of ambient UFPs may be performed through stationary and mobile methods for environmental profiling and exposure assessment purposes. UFPs PNC esti- mation model (LUR) developed from measurement data could be deployed to support future epidemiological study of ambient UFPs. Low-cost sensors such as bipolar ion and ionization sensor from common smoke detector device may be further developed as affordable instrument to monitor ambient UFPs. Recent studies indicate that short-term exposure of UFPs can be associated with HRV change and increased cardiopulmonary effects. On the other hand, long-term UFPs exposure have positive association with COPD, CVD, CHF, pre-term birth, asthma, and also acute myocardial infarction cases.
In this study, the generation-specific, lobar, regional, and total deposition of Particulate matter (PM) in the human respiratory tract (HRT) and its clearance was quantified using the Multiple Path Particle Dosimetry Model (MPPD-V3.04). The visualizations of the deposited PM are also shown. The study area was a technical institute of national importance, highly affected by PM pollution. Ambient PM particles (PM1, PM2.5 and PM10) were measured in three seasons (i.e., monsoon, winter and summer). Different age groups, viz. adults (18 and 21 years), adolescents (14 years), children (8 years), toddlers (28 months) and Infants (3 months) were considered. Deposited mass (Dm) in the winter season was significantly higher than the monsoon for all 3 p.m. sizes (PM10 (60%), PM2.5 (45%) and PM1 (43%)), mainly due to the greater PM levels witnessed in the winters. The deposition of PM10 was maximum in the head region (81%), and it increases with the age of individuals. The fine fraction (PM1 and PM2.5) was predominantly deposited in the pulmonary region. The maximum pulmonary deposition of fine fraction lies in children (49.5%). The variation in deposition percentage was mainly because of airway geometries, PM sizes, and deposition mechanisms. In lobar region, maximum deposition occurred in the lower lobes (65.9%). Concerning clearance, about 54.5% and 1.8% of the submicron particles deposited in the pulmonary and TB region, respectively, were retained even at the end of one year. Present study results may help analyze potential health risks in different age groups and targeted drug delivery.
Nanomaterials, that is, materials made up of individual units between 1 and 100 nanometers, have lately involved a lot of attention since they offer a lot of potential in many fields, including pharmacy and biomedicine, owed to their exceptional physicochemical properties arising from their high surface area and nanoscale size. Smart engineering of nanostructures through appropriate surface or bulk functionalization endows them with multifunctional capabilities, opening up new possibilities in the biomedical field such as biosensing, drug delivery, imaging, medical implants, cancer treatment and tissue engineering. This article highlights up‐to‐date research in nanomaterials functionalization for biomedical applications. A summary of the different types of nanomaterials and the surface functionalization strategies is provided. Besides, the use of nanomaterials in diagnostic imaging, drug/gene delivery, regenerative medicine, cancer treatment and medical implants is reviewed. Finally, conclusions and future perspectives are provided.
Nanotechnology plays an important role in biological research, especially in the development of delivery systems with lower toxicity and greater efficiency. These include not only metallic nanoparticles, but also biopolymeric nanoparticles. Biopolymeric nanoparticles (BPNs) are mainly developed for their provision of several advantages, such as biocompatibility, biodegradability, and minimal toxicity, in addition to the general advantages of nanoparticles. Therefore, given that biopolymers are biodegradable, natural, and environmentally friendly, they have attracted great attention due to their multiple applications in biomedicine, such as drug delivery, antibacterial activity, etc. This review on biopolymeric nanoparticles highlights their various synthesis methods, such as the ionic gelation method, nanoprecipitation method, and microemulsion method. In addition, the review also covers the applications of biodegradable polymeric nanoparticles in different areas—especially in the pharmaceutical, biomedical, and agricultural domains. In conclusion, the present review highlights recent advances in the synthesis and applications of biopolymeric nanoparticles and presents both fundamental and applied aspects that can be used for further development in the field of biopolymeric nanoparticles.
Particulate matter (PM) poses a severe health threat to the public, and fibrous filtration is a powerful method for efficient PM removal. Arming the fibers with electrostatic effect is a gold rush to promote PM-fiber interaction, thus reaching high PM removal efficiency, decreasing airflow resistance, and achieving multifunctional applications simultaneously. In this study, we are to provide a comprehensive overview of electrostatic fibrous filters, including the principles, fabrication process, electrical properties, and applications. Firstly, PM-fiber adhesion forces during the filtration were analyzed according to the electrified principle for the filters. Furthermore, electrostatic filters were classified into monopolar-charged and dipolar-induced filters in the dimension of charging characteristics. Compared with other PM removal techniques, the electrical properties, comprehensive performance, and applications for various electrostatic filters are systematically stated and discussed. In the end, we highlighted that the electrostatic fibrous filters would be a competitive candidate for PM removal owing to their durability, versatility, and plasticity. We also discussed the importance of conducting rigorous filtration tests to report accurate performance for electrostatic filters. In an interdisciplinary view between environmental engineering and material engineering, we hope this work could provide a better understanding of the PM-fiber electrostatic interactions and practical insights for designing next-generation air filters.
Water-soluble formulations of the pyrazole derivative 3-(4-chlorophenyl)-5-(4-nitrophenylamino)-1H-pyrazole-4-carbonitrile (CR232), which were proven to have in vitro antiproliferative effects on different cancer cell lines, were prepared by two diverse nanotechnological approaches. Importantly, without using harmful organic solvents or additives potentially toxic to humans, CR232 was firstly entrapped in a biodegradable fifth-generation dendrimer containing lysine (G5K). CR232-G5K nanoparticles (CR232-G5K NPs) were obtained with high loading (DL%) and encapsulation efficiency (EE%), which showed a complex but quantitative release profile governed by Weibull kinetics. Secondly, starting from hydrogenated soy phosphatidylcholine and cholesterol, we prepared biocompatible CR232-loaded liposomes (CR232-SUVs), which displayed DL% and EE% values increasing with the increase in the lipids/CR232 ratio initially adopted and showed a constant prolonged release profile ruled by zero-order kinetics. When relevant, attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS) experiments, as well as potentiometric titrations completed the characterization of the prepared NPs. CR232-G5K NPs were 2311-fold more water-soluble than the pristine CR232, and the CR232-SUVs with the highest DL% were 1764-fold more soluble than the untreated CR232, thus establishing the success of both our strategies.
Protein corona adsorption layers on nanoparticle surfaces, dispersed in biological fluids, can significantly change the interfacial interactions, reactivity, and mobility of the original nanoparticles designed as a drug carrier or existing as bioaerosols, bacteria, or viruses. The evaluation of the level of interactions (hard/soft corona), dispersion stability, and the ratio of the attached proteins per nanoparticle are essential parameters for the characterization of the protein corona formation on nanoparticle (PCN). In spite of development of several experimental techniques for this purpose, still more powerful, economical and fast measuring techniques are needed to work in-situ at original solution samples (near the physiological conditions), without requirement of additional sample preparation which can change the quality/quantity of the original interactions. In this study, a novel experimental protocol based on the analysis of dynamic interfacial properties (ADIP) is developed for in-situ evaluation of the protein–nanoparticle interactions under original conditions. For this purpose, dynamic surface tension and interfacial elasticity values of the bovine serum albumin (BSA) solutions alone and in mixed solutions with silica nanofluids are measured using drop profile analysis tensiometry. A considerable difference between the dynamic surface tension of BSA and protein corona solutions (BSA+SiO2 NPs complexes) demonstrates significant adsorption of the protein molecules at nanoparticles, confirmed by Fourier Transform Infrared Spectroscopy (FTIR) analysis. PCN complexes illustrate much slower kinetics of adsorption due to a smaller diffusion coefficient according to their larger size. The free proteins available in the solution were estimated considering early-time values of the dynamic surface tension, used for estimation of the adsorbed proteins per unit area of the silica surface (mol/cm²), considering the initial protein concentration in the bulk. The results show very good agreement with others’ results provided by AFM, DLS, UV–vis Spectroscopy, Multi-Parametric Surface Plasmon Resonance (MP-SPR), and Quartz Crystal Microbalance (QCM). Our novel experimental protocols and data analysis, demonstrates promising results for differentiation of the hard and soft corona layers, and unique for soft corona layer recognition, which is difficult by other available techniques, due to quick disturbances of weak protein-protein interaction in soft corona. The measured interfacial elasticity values confirm PCN formation and provides additional information for better differentiations of the corona layers.
Cracks that occur over time are difficult to detect and repair, and they threaten the safety and durability of buildings and limit sustainable building design. This study investigates the feasibility of using hydroxyapatite (HAp) with graphene oxide and silver nanoparticles to self-heal narrow cracks that are difficult to detect. Ultrasonic pulse velocity, compressive strength, portlandite content, the percentage of water absorption and porosity recovery was observed with increases of 77.5%, 259.6%, 406.28%, 35.1% and 22.0% respectively for the 0.1 wt% of HAp content. Healing efficiency of micro-crack width on surface of cement pastes was reached 62.52%, by incorporating with HAp and silver nanoparticles. The healing property was found to be associated with the hydrogen bonds, electrostatic interactions with negatively charged PO4⁻³ and OH– ions groups and development of portlandite formed by the reaction between Ca²⁺ and OH– ions.
The transport of drug to the brain is mainly restricted owing to the existence of a strong defense mechanism, the blood–brain barrier (BBB). The entrance of any substances inside the brain is regulated by the BBB. Numerous brain diseases remain undertreated due to the incapability of conventional dosage form to surpass the BBB. Because of the lipophilic nature of the BBB, an inadequate amount of the drug reaches the brain. Nanotechnology is a novel, one of the rapidly growing technology that can help to intensify the drug passage across the BBB. The potential of different carriers such as microspheres, liposomes, and nanoparticles has been investigated to ameliorate the accumulation of drug inside the brain. Among the different nanocarriers, lipid‐based nanoparticles have received great attention in the treatment of brain disorders. They facilitate drug retention at the target site due to biocompatibility, non‐toxicity, and biodegradable nature. Furthermore, they have immense potential to bypass the BBB because of small particle size, lipophilic nature, and evade the reticular endothelial system. Besides these tremendous advantages of lipid nanoparticles, they are likely to induce the toxic response. Hence, it is obligatory to find out the toxicity lipid nanoparticles possess. This chapter focuses on various barriers to brain delivery, the role of lipid nanoparticles for brain delivery, types of lipid nanoparticles, transport mechanisms, strategies for brain delivery, toxicity, and safety of lipid nanoparticles.
Copper oxide nanoparticles (CuO-NPs) are used in various industrial and commercial products due to their enhanced physicochemical properties. The vast consumption increases their exposure in the environment, thereby affecting the ecosystem. Even with the rise in research towards understanding their toxicity, the major signaling cascades and hub genes involved in CuO-NPs remain elusive due to the various attributes involved (size, shape, charge, coating in terms of nanoparticles, and dose, duration, and species used in the experiment). The focus of the study is to identify the key signaling cascades and genes involved in CuO-NPs toxicity irrespective of these attributes. CuO-NPs related microarray expression profiles were screened from GEO database and were subjected to toxicogenomic analysis to elucidate the toxicity mechanism. In silico tools were used to obtain the DEGs, followed by GO and KEGG functional enrichment analysis. The identified DEGs were then analyzed to determine major signaling pathways and hub genes. Module and centrality parameter analysis was performed to identify the hub genes. Further, the miRNAs and transcription factors involved in regulating the genes were predicted, and their interactive pathways were constructed. A total of 44 DEGs were commonly present in all the analysed datasets and all of them were downregulated. GO analysis reveals that most of the genes were enriched in functions related to cell division and chemotaxis. Cell-cycle, chemokine, cytokine-cytokine receptor interaction, and p53 signaling pathways were the key pathways with Cdk1 as the major biomarker altered irrespective of the variables (dosage, duration, species used, and surface coating). Overall, our integrated toxicogenomic analysis reveal that Cdk1 regulated cell cycle and cytokine-cytokine signaling cascades might be responsible for CuO-NPs toxicity. These findings will help us in understanding the mechanisms involved in NPs toxicity.
The unique chemical and physical properties of halloysite nanotube (HNT) have aroused the interests of researchers in various fields to fabricate new high-performance composites. In this research project rheological, mechanical, and microstructural properties of HNT reinforced cementitious composites with varied ultrasonication energies were investigated. Based on the mini-slump and flow table tests, it was found that the workability of fresh HNT containing cement mortars reduced by increasing the ultrasonication energy owing to conversion of HNT agglomerations into smaller ones. Obtained results of mechanical tests revealed that HNT-reinforced samples have generally shown higher strength compared to the control sample. Moreover, the incorporation of 1, 2 and 3 wt% HNT in the samples at the level of ultrasonication energy equal to 0.8 Joule/mL per unit HNT percentage by weight of cement resulted in the maximum mechanical improvement by 25.83, 41.25 and 47.98% for compressive strength and 12.52, 20.71 and 22.47% for flexural strength, respectively. Helium porosity and mercury intrusion porosimetry tests showed that increasing the ultrasonication energy diminishes the porosity of the sample. Not only do the results of the current study show the effect of ultrasonication energy on the engineering properties of HNT cementitious composites, but it also helps researchers find the HNT concentration–independent optimum ultrasonication energy.
The COVID-19 outbreak is creating severe impressions on all facets of the global community. Despite strong measures worldwide to try and re-achieve normalcy, the ability of SARS-Cov-2 to survive sturdy ecological settings may contribute to its rapid spread. Scientists from different aspects of life are working together to develop effective treatment strategies against SARS-Cov-2. Apart from using clinical devices for patient recovery, the key focus is on the development of antiviral drugs and vaccines. Given the physical size of the SARS-CoV-2 pathogen and with the vaccine delivery platform currently undergoing clinical trials, the link between nanotechnology is clear, and previous antiviral research using nanomaterials confirms this link. Nanotechnology-based products can effectively suppress various pathogens, including viruses, regardless of drug resistance, biological structure, or physiology. Thus, nanotechnology is opening up new dimensions for developing new strategies regarding diagnosis, prevention, and treatment of COVID-19 and other viral ailments. This article describes the application of nanotechnology against the COVID-19 virus in terms of therapeutic purposes and vaccine development through the invention of nanomaterial-based substances such as sanitizers (hand washing agents and surface disinfectants), masks and gowns, amongst other personal protective equipment (PPE), diagnostic tools, and nanocarrier systems, as well as the drawbacks and challenges of nanotechnology that need to be addressed.
Preparation of the biological samples is one of the most critical steps in sample analysis. In past decades, the liquid–liquid extraction technique has been used to extract the desired analytes from complex biological matrices. However, solid-phase extraction (SPE) gained popularity due to versatility, simplicity, selectivity, reproducibility, high sample recovery %, solvent economy, and time-saving nature. The superior extraction efficiency of SPE can be attributed to the development of advanced techniques, including the nanosorbents technology. The nanosorbent technology significantly simplified the sample preparation, improved the selectivity, diversified the application, and accelerated the sample analysis. This review critically expands on the to-date advancements reported in SPE with particular regards to the nanosorbent technology.
The first Covid-19 patient in India was reported on January 30, 2020 at the state of Kerela. The patient number rose to three by February 3, 2020. In the month of March 2020, the transmissions started to increase when the people started to return back to India from the Covid-19 affected countries. On March 12, a 76-year-old man having a travel history to Saudi Arabia was the first reported fatality in India due to Covid 19. Then for the prevention of the propagation of Covid, the Indian government declared a state of health emergency and strict counter measures were taken, including locking down of cities, prohibiting almost all avoidable activities and restricting population's mobility. From March 24, 2020 due to the complete lockdown in the country, human activities were heavily restricted in the whole geographical regions of India. This pandemic lockdown eventually serves as an opportunity to observe the background concentrations of pollutants in the atmosphere. The PM 2.5 distribution can affect human health and to overcome this problem, setting up of regulation for PM is necessary. In the present study Probability density functions (PDF) method have been utilised for the investigation of PM 2.5 pollutant data distribution of five countries namely, India, China, France, Brazil and United States of America (USA) for their respective lockdown period of 2020 and corresponding same period of 2019. A detailed study has been done for India, and for that purpose India has been divided into three regions (Central India, Coastal India and Indo-Gangetic Plain (IGP)) on the basis of different meteorological conditions. PM 2.5 concentration for hourly basis has been analysed for the lockdown period 24th March to 15th June 2020 and compared with the PM 2.5 concentration of previous year 2019 for the same time period. To understand the effect of lockdown in PM 2.5 emission in India, which will give us an idea about the background concentration, PDFs (Probability Density Function) has also been generated for the whole year from 2015 to 2019. The “goodness-of-fit” of the probability density functions, to the data, was assessed, using various statistical indices (Chi-square test). Results show that the PM 2.5 reduction during the lockdown period of 2020 as compared to the same period of 2019 is sufficiently large. This study will give a certain degree of idea to the regulatory bodies on planning and implementation of strict air quality control plans.
Air pollution by particulate matter (PM) is one of the main threats to human health, particularly in large cities where pollution levels are continually exceeded. According to their source of emission, geography, and local meteorology, the pollutant particles vary in size and composition. These particles are conditioned to the aerodynamic diameter and thus classified as coarse (2.5–10 μm), fine (0.1–2.5 μm), and ultrafine (<0.1 μm), where the degree of toxicity becomes greater for smaller particles. These particles can get into the lungs and translocate into vital organs due to their size, causing significant human health consequences. Besides, PM pollutants have been linked to respiratory conditions, genotoxic, mutagenic, and carcinogenic activity in human beings. This document presents an overview of emission sources, physicochemical characteristics, collection and measurement methodologies, toxicity, and existing control mechanisms for ultrafine particles (UFPs) in the last fifteen years.
The fast growth of industrialization combined with the increasing population has led to an unparalleled demand for providing water in a safe, reliable, and cost-effective way, which has become one of the biggest challenges of the twenty-first century faced by global society. The application of nanotechnology in water treatment and pollution cleanup is a promising alternative in order to overcome the current limitations. In particular, the application of magnetic iron oxide nanoparticles (MIONs) for environmental remediation has currently received remarkable attention due to its unique combination of physicochemical and magnetic properties. Given the broadening use of these functional engineered nanomaterials, there is a growing concern about the adverse effects upon exposure of products and by-products to the environment. This makes vitally relevant the development of green chemistry in the synthesis processes combined with a trustworthy risk assessment of the nanotoxicity of MIONs as the scientific knowledge of the potential hazard of nanomaterials remains limited. This work provides comprehensive coverage of the recent progress on designing and developing iron oxide-based nanomaterials through a green synthesis strategy, including the use of benign solvents and ligands. Despite the limitations of nanotoxicity and environmental risks of iron oxide-based nanoparticles for the ecosystem, this critical review presents a contribution to the emerging knowledge concerning the theoretical and experimental studies on the toxicity of MIONs. Potential improvement of applications of advanced iron oxide-based hybrid nanostructures in water treatment and pollution control is also addressed in this review.
There is a growing use of nano-functionalized construction materials, which contain nanoparticles embedded in their bulk or deposited on their surfaces. In the case of photocatalytic materials, nano-TiO2 is usually added to provide it's functionality. One concern about these materials, in addition to release of nanoparticles as airborne, is that they can be leached into the aquatic environment. Moreover, water eutrophication could be caused due to the increase in NO3⁻ as a product of the photocatalytic oxidation of NOx in runoff. In this paper, a systematic long term campaign assessing these potential side effects in the real outdoor environment has been carried out. Rainwater leachates from 4 m² slabs of 7 different photocatalytic materials exposed outdoors in two different locations (platforms) were collected and analysed over more than 800 days. Ti, NO3⁻, pH and conductivity were analysed. Ti was found in the leachates of almost every material, without a clear relation with the type of application (percolated cementitious slurry, suspension/emulsion or TiO2 built-in). The highest concentration found was of 60 μg/L, which seems to be rather small when comparing with some threshold values for drinking water. In all the cases, the detected TiO2 nanoparticles from water leachates were embedded in large microparticle agglomerates coming from the construction material matrix, which are less dangerous than nanoparticles. Nitrates were leached in clear relation with the NOx oxidation photocatalytic performance, and the observed concentrations were not higher than those in the recycled water used by the Madrid City Council to clean the streets.
The civil engineering area has long been known for not being associated with high tech startup creation. This is a sign of the low innovation which is confirmed by its low patenting level thus contributing to undermine the prestige of this area. Still this area has an important role to play given the environmental impacts of the construction industry that will be exacerbated in the next decades due to the growth in world population, each day there are about 220,000 new inhabitants which means more than 9,7 billion people by 2050 and 11,2 billion by 2100. A direct consequence of such growth relates to a steady increase of energy consumption which is the source of two-thirds of global greenhouse-gas emissions. The building sector is responsible for high energy consumption and its global demand is expected to grow in the next decades. Between 2010 and 2050 the global heating and cooling needs are expected to increase 70% in residential buildings and 90% in commercial buildings. Major energy efficiency measures are therefore crucial to reduce energy consumption and greenhouse-gas emissions of the building sector. This includes development of new technologies and materials to improve greatly energy efficiency. Since information derived from knowledge is critical for individuals to transform innovative ideas into commercial products and services, this paper reviews recent developments on nano and bio based innovations important for an energy efficient built environment. This review may contribute to enhance the innovation and patenting activity in civil engineering. This may help to foster the creation of high tech startups for an energy efficient built environment.
The unceasing efforts and improvement of drug delivery systems (DDSs) have been broadly researched to maximize therapeutic efficacy while curtailing undesirable side effects. Nanoparticle technology was recently shown to hold great promise for drug delivery applications in nanomedicine due to its favorable properties, such as better encapsulation, bioavailability, control release, and lower toxic effects. Regardless of the great progress in nanomedicine, there remain many limitations prior to widely being accepted for medical application. To overcome these limitations, advanced nanoparticles for drug delivery have been developed to enable the spatially and temporally controlled release of drugs in response to specific stimuli at disease sites. An ideal drug delivery system should be able to localize a drug specifically and directly to its target. This is particularly important when drugs made by traditional manufacturing methods are hydrophobic and their solvents are toxic. Nanotechnology promises to improve drug delivery system design and targeting. Nanostructured drugs or delivery carriers allow the continuous and controlled release of therapeutic drugs to maintain drug levels to a desired extent. The size of nanoparticles ranges from 10 to 200 nm, about the size of a protein. Because of their small size, nanoparticles can readily interact with biomolecules on the cell surface or inside cell allowing these nanoparticles to penetrate tissues in depth with a high level of specificity. This chapter discusses an overview of nanoparticulate systems that can be used as a potential drug delivery carriers and focuses on the potential applications of nanoparticles in various biomedical fields for improving human health care.
This review is written with the goal of informing public health concerns related to nanoscience, while raising awareness of nanomaterials toxicity among scientists and manufacturers handling them. We show that humans have always been exposed to nanoparticles and dust from natural sources and human activities, the recent development of industry and combustion-based engine transportation profoundly increasing anthropogenic nanoparticulate pollution. The key to understanding the toxicity of nanoparticles is that their minute size, smaller than cells and cellular organelles, allows them to penetrate these basic biological structures, disrupting their normal function. Among diseases associated with nanoparticles are asthma, bronchitis, lung cancer, neurodegenerative diseases (such as Parkinson`s and Alzheimer`s diseases), Crohn`s disease, colon cancer. Nanoparticles that enter the circulatory system are related to occurrence of arteriosclerosis, and blood clots, arrhythmia, heart diseases, and ultimately cardiac death. We show that possible adverse effects of nanoparticles on human health depend on individual factors such as genetics and existing disease, as well as exposure, and nanoparticle chemistry, size, shape, and agglomeration state. The faster we will understand their causes and mechanisms, the more likely we are to find cures for diseases associated with nanoparticle exposure. We foresee a future with better-informed, and hopefully more cautious manipulation of engineered nanomaterials, as well as the development of laws and policies for safely managing all aspects of nanomaterial manufacturing, industrial and commercial use, and recycling.
Objectives—This report presents final 2004 data on the 10 leading causes of death in the United States by age, race, sex, and Hispanic origin. Leading causes of infant, neonatal, and postneonatal death are also presented. This report supplements the annual report of final mortality statistics.
Methods—Data in this report are based on information from all death certificates filed in the 50 states and the District of Columbia in 2004. Causes of death classified by the International Classification of Diseases, Tenth Revision (ICD–10) are ranked according to the number of deaths assigned to rankable causes.
Results—In 2004, the 10 leading causes of death were (in rank order) Diseases of heart; Malignant neoplasms; Cerebrovascular diseases; Chronic lower respiratory diseases; Accidents (unintentional injuries); Diabetes mellitus; Alzheimer’s disease; Influenza and pneumonia; Nephritis, nephrotic syndrome and nephrosis; and Septicemia and accounted for about 78 percent of all deaths occurring in the United States. Differences in the ranking are evident by age, sex, race, and Hispanic origin. Leading causes of infant death for 2004 were (in rank order) Congenital malformations, deformations and chromosomal abnormalities; Disorders related to short gestation and low birth weight, not elsewhere classified; Sudden infant death syndrome; Newborn affected by maternal complications of pregnancy; Accidents (unintentional injuries); Newborn affected by complications of placenta, cord and membranes; Respiratory distress of newborn; Bacterial sepsis of newborn; Neonatal hemorrhage; and Diseases of the circulatory system. Important variation in the leading causes of infant death is noted for the neonatal and postneonatal periods.
On April 15 and 19, 1998, two intense dust storms were generated over the Gobi desert by springtime low-pressure systems descending from the northwest. The windblown dust was detected and its evolution followed by its yellow color on SeaWiFS satellite images, routine surface-based monitoring, and through serendipitous observations. The April 15 dust cloud was recirculating, and it was removed by a precipitating weather system over east Asia. The April 19 dust cloud crossed the Pacific Ocean in 5 days, subsided to the surface along the mountain ranges between British Columbia and California, and impacted severely the optical and the concentration environments of the region. In east Asia the dust clouds increased the albedo over the cloudless ocean and land by up to 10–20%, but it reduced the near-UV cloud reflectance, causing a yellow coloration of all surfaces. The yellow colored backscattering by the dust eludes a plausible explanation using simple Mie theory with constant refractive index. Over the West Coast the dust layer has increased the spectrally uniform optical depth to about 0.4, reduced the direct solar radiation by 30–40%, doubled the diffuse radiation, and caused a whitish discoloration of the blue sky. On April 29 the average excess surface-level dust aerosol concentration over the valleys of the West Coast was about 20–50 μg/m3 with local peaks >100 μg/m3. The dust mass mean diameter was 2–3 μm, and the dust chemical fingerprints were evident throughout the West Coast and extended to Minnesota. The April 1998 dust event has impacted the surface aerosol concentration 2–4 times more than any other dust event since 1988. The dust events were observed and interpreted by an ad hoc international web-based virtual community. It would be useful to set up a community-supported web-based infrastructure to monitor the global aerosol pattern for such extreme aerosol events, to alert and to inform the interested communities, and to facilitate collaborative analysis for improved air quality and disaster management.
Experimental observations of various deformation and fracture modes under compression of single multiwalled carbon nanotubes, obtained as a result of embedment within a polymeric film, are reported. Based on a combination of experimental measurements and the theory of elastic stability, the compressive strengths of thin- and thick-walled nanotubes are found to be about 2 orders of magnitude higher than the compressive strength of any known fiber.
Sunlight can have deleterious effects on humans: causes sunburns and is the principal cause of skin cancers. Usage of TiO2 (and ZnO) in sunscreen lotions, widely used as UVA/UVB blockers, and intended to prevent sunburns and to protect consumers from skin cancers (carcinomas and melanomas) is examined. Although used to mineralize many undesired organic pollutants, TiO2 is considered to be a safe physical sunscreen agent because it reflects and scatters both UVB (290-320 nm) and UVA (320-400 nm) sunlight; however, it also absorbs substantial UV radiation which, in aqueous media, yields hydroxyl radial ((DOT)OH) species. These species cause substantial damage to DNA (J. Photochem.Photobio.A:Chem.,111(1997)205). Most importantly, sunlight-illuminated sunscreen TiO2 particles catalyze DNA damage both in vitro and in human cells (FEBS Letters, 418 (1997)87). These results raise concerns on the overall effects of sunscreens and raise the question on the suitability of photoactive TiO2 as a sunscreen component without further studies. The photocatalytically active nature of these metal oxides necessitates some changes since even the TiO2 specimens currently used in suncreams cause significant DNA strand breaks.
For the first time, long-range transport of ``Kosa'' mineral aerosol from western China to southwestern British Columbia is documented. This late April 1998 event coincided with an episode of photochemical smog and reduced dispersion in the Lower Fraser Valley (LFV). Filter samples in the region show a massive injection of crustal elements (Si, Fe, Al, and Ca) with concentrations of Si approximately double those previously recorded. Ratios of these elements to Fe are shown to be statistically similar to ratios observed in mineral aerosol events in Hawaii and China. On the basis of the difference between observed and expected elemental concentrations and reconstructed soil mass in the episode, it is estimated that Asian dust contributed 38-55% to observed PM10 in the LFV, the remainder being attributed to local sources. Comparison of the April 1998 event with two spring meteorological analogs is consistent with this estimate. Mesoscale model simulations suggest that mineral dust was incorporated into the planetary boundary layer as a result of strong subsidence over the interior of southern British Columbia and Washington State which permitted interception of lower tropospheric elevated aerosol layers by surface-based mixing processes over mountainous terrain. Surface easterly (``outflow'') winds then transported this material into the Lower Fraser Valley where it contributed significantly to total particulate loadings and an intense haze. This mechanism is consistent with the observed spatial and temporal distribution of PM10.
Photocatalytic paint was prepared by adding Fe-doped TiO2 nanocrystalline powders into self-engineered oxidation-resistant latex paint system. The UV-Vis diffuse reflectance spectroscopy was used to characterize the light absorption properties of the paint. The colony counting method was used to study photocatalytic sterilization ratio of E. coli under visible light irradiation. Effects of the kinds and amounts of TiO2 powders added in the paint on the sterilization ratio under visible light irradiation with fixed relative humidity were systematically investigated. The UV-Vis diffuse reflectance spectroscopy indicates that the absorption thresholds of the Fe-doped TiO2 paint have red-shifted into visible light region. The antibacterial experiment results show that the sterilization ratio of E. coli can exceed more than 99% in less than 4 hours under 400-lux-visible light irradiation under RH of 55%.
A new functional photocatalytic paint was prepared by adding N-doped nanocrystallinc anatasc TiO2 powders into self-engineered oxidation resistance latex paint system. The property of the UV-Vis light absorbance of the paint was characterized. The effects of the amount, types, and the introducing methods of the TiO2 in the paints on the behavior of the UV absorption, photocatalytic properties of the paint were systematically investigated. UV-Vis absorption spectra reveal that the ultraviolet light can strongly be absorbed by the paints. The absorption edge of the N-doped nanocrystalline anatase powders modified paint has red-shifted to visible light region. The colony counting method is used to study its sterilization performance under visible light irradiation. The sterilization experiments show that the rate of sterilizing staphylococcal bacteria by the N-doped TiO 2 modified paint can exceed more than 99% after the paint has been irradiated by the visible light for 2 to 4 hours.
Crohn’s disease is a modern Western disease characterised by transmural inflammation of the gastrointestinal tract. It is of unknown aetiology, but evidence suggests that it results from a combination of genetic predisposition and environmental factors. Bacterial-sized microparticles (0·1–1·0 µm) are potent adjuvants in model antigen-mediated immune responses and are increasingly associated with disease. Microparticles of TiO2 and aluminosilicate accumulate in macrophages of human gut-associated lymphoid tissue where the earliest signs of lesions in Crohn’s disease are observed. Dietary microparticles are of endogenous or exogenous origin. Endogenous microparticles dominate and are calcium phosphate (most probably hydroxyapatite), which precipitates in the lumen of the mid-distal gastrointestinal tract due to secretion of Ca and phosphate in the succus entericus. Exogenous dietary microparticles are contaminants (soil and/or dust) and food additives. TiO2, for example, is a food colourant, and aluminosilicates are anti-caking agents, although some aluminosilicates occur as natural contaminants. Food additives alone account for ingestion of approximately 1012 particles/person per d. Possible mechanisms for the role of exogenous and endogenous dietary microparticles in promoting toleragenic or immune responses of gastrointestinal mucosal phagocytosis are discussed. In a double-blind randomised pilot study we have shown that a diet low in Ca and exogenous microparticles appears to alleviate the symptoms of ileal Crohn’s disease, with a significant (P = 0·002) improvement in the Crohn’s disease activity index. A multi-centre trial and further mechanistic studies at the cellular level are underway.
Nanotechnology is the term used to cover the design, construction, and utilization of structures with at least one dimension measured in nanometers. Compared with typical civil engineering structures, the two fields operate on hugely divergent dimensional scales. Nanotechnology initially developed in the fields of physics and chemistry, and most fundamental developments still occur in these fields. However, for the technology to affect society at large, it needs to be applied in areas such as the engineering field. This paper focuses specifically on current and potential developments in pavement engineering where the unique properties of nanomaterials may be used to deliver a better environment to society, based on identified needs and challenges in the pavement engineering field. It is demonstrated that there are essentially two areas where nanotechnology can complement pavement engineering. These are in the development of improved materials and the use of characterization methods to improve the understanding of materials. Examples of current and planned research in these areas are cited and discussed. Finally, current challenges in exploiting the unique properties of nanomaterials in pavement engineering are indicated and discussed. The paper demonstrates that although the majority of the fundamental developments in nanoscale science and technology are occurring in the fundamental physics, chemistry, and typically electronic engineering fields, the potential for this technology to impact on the quality of life of society at large is huge.
Materials that contain a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. It
is the purpose of this study to investigate the photocatalytic activity of commercial paints containing TiO2 nanoparticles towards NO and NO2. Experiments were carried out in a stainless steel (30 m-3) walk-in type environmental chamber (Indoortron), under “real world setting” conditions of temperature, relative humidity,
irradiation and pollutant concentrations. Two types of nanoparticle TiO2-containing paints were tested for their depolluting properties: a mineral silicate paint and a water-based styrene acrylic
paint. The results showed a significant effect of TiO2-materials in reducing NOx. It was found that up to 74% of NO and 27% of NO2 were photo-catalytically degraded by the mineral silicate paint, while degradation percentage using the styrene acrylic paint
reached 91% and 71% for NO and NO2, respectively. The photo-catalytic rate of NO on the mineral and styrene acrylic paint was calculated to 0.11 μg m-2 s and 0.18 μg m-2 s, respectively, indicating higher photocatalytic performance of the organic based material. The effect of relative humidity
(RH) was also investigated. An increase of RH from 20% to 50% inhibited the NOx photocatalysis on the surface of the samples.
Environmental surfaces and their role in the epidemiology of hospital-acquired infections (HAIs) have become an area of great scientific interest, particularly in light of the much publicised cases of infections due to methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile in UK hospitals. This feature article sets out to examine the role of surfaces and the inanimate environment in the spread of HAIs, and looks at various antimicrobial techniques being researched to reduce microbial contamination of surfaces. Preventative measures such as coatings which reduce initial microbial adhesion to surfaces will be considered alongside actively antimicrobial measures which inactivate microorganisms already adherent to a surface. The principal focus of this feature article will be given to light-activated antimicrobial surfaces such as the photocatalyst TiO2 and surfaces with embedded photosensitisers. Surfaces which release antimicrobial compounds or metal ions such as silver and copper are also examined, alongside materials which kill microbes upon contact. The widespread research and development of these antimicrobial surfaces is of great importance in maintaining acceptable levels of hygiene in hospitals and will help to fight the spread of HAIs via the contamination of inanimate surfaces in the healthcare environment.
The type of lung disease caused by metal compounds depends on the nature of the offending agent, its physicochemical form, the dose, exposure conditions and host factors. The fumes or gaseous forms of several metals, e.g. cadmium (Cd), manganese (Mn), mercury (Hg), nickel carbonyl (Nl(CO)4, zinc chloride (ZnCl2), vanadium pentoxide (V2O5), may lead to acute chemical pneumonitis and pulmonary oedema or to acute tracheobronchitis. Metal fume fever, which may follow the inhalation of metal fumes e.g. zinc (Zn), copper (Cu) and many others, is a poorly understood influenza-like reaction, accompanied by an acute self-limiting neutrophil alveolitis. Chronic obstructive lung disease may result from occupational exposure to mineral dusts, including probably some metallic dusts, or from jobs involving the working of metal compounds, such as welding. Exposure to cadmium may lead to emphysema. Bronchial asthma may be caused by complex platinum salts, nickel, chromium or cobalt, presumably on the basis of allergic sensitization. The cause of asthma in aluminium workers is unknown. It is remarkable that asthma induced by nickel (Ni) or chromium (Cr) is apparently infrequent, considering their potency and frequent involvement as dermal sensitizers. Metallic dusts deposited in the lung may give rise to pulmonary fibrosis and functional impairment, depending on the fibrogenic potential of the agent and on poorly understood host factors. Inhalation of iron compounds causes siderosis, a pneumoconiosis with little or no fibrosis. Hard metal lung disease is a fibrosis characterized by desquamative and giant cell interstitial pneumonitis and is probably caused by cobalt, since a similar disease has been observed in workers exposed to cobalt in the absence of tungsten carbide. Chronic beryllium disease is a fibrosis with sarcoid-like epitheloid granulomas and is presumably due to a cell-mediated immune response to beryllium. Such a mechanism may be responsible for the pulmonary fibrosis occasionally found in subjects exposed to other metals e.g. aluminium (Al), titanium (Ti), rare earths. The proportion of lung cancer attributable to occupation is around 15%, with exposure to metals being frequently incriminated. Underground mining of e.g. uranium or iron is associated with a high incidence of lung cancer, as a result of exposure to radon. At least some forms of arsenic, chromium and nickel are well established lung carcinogens in humans. There is also evidence for increased lung cancer mortality in cadmium workers and in iron or steel workers.
The importance of nanotechnology related research and development has become recognised worldwide. Substantial public and private investment is now being ploughed into research and development in a number of industrial sectors, where nanotechnology has become established and has led to new commercial products. The construction industry, having major economic significance with nano-scale research and development which is only emerging, offers a wide scope for exploitation of nanotechnology. With international contributions from experts in the field, Nanotechnology in Construction amalgamates previously fragmented research and emerging trends. It reflects the inherent multi-disciplinary nature of nano-scale research in construction and contributions cover a wide spectrum, from highly scientific investigations to futuristic applications. The book is organised into four broad sections, the first reviews and analyses the prospects of exploitation of nanotechnology in construction, the second discusses novel tools and their capabilities, the final two sections show existing significant products where nanotechnology has been already been exploited or where product development is under-way. Nanotechnology in Construction will appeal to researchers already working in this field as well as those wishing to enter it. It will also inform governmental and other funding agencies of the most promising future directions and their related timescales. Practical applications are considered and explanations of the underlying basics are given, raising awareness and understanding of what nanotechnology can offer to construction professionals in general.
The mechanical properties of concrete containing ZnO2 nanoparticles which was cured in saturated limewater have been optimized. ZnO2 nanoparticles were added to concrete as nano-fillers. The specimens were cured in water and saturated limewater for 7, 28 and 90 days after casting and then their strength was evaluated by mechanical testing (compressive, split tensile and flexural strength tests). The results showed that replacement of Portland cement with ZnO2 nanoparticles up to 1.0 wt.% for the specimens cured in water and 2.0 wt.% for the specimens cured in saturated limewater produces concrete with the best strength. It has been shown that curing the specimens in saturated limewater for 28 days and then in water until 90 days, produces a stronger concrete than those cured only in saturated limewater for 90 days. Excess Ca(OH)(2) crystals which form after 28 days, when the specimens are cured in limewater, do not contribute to strength enhancement as much as strengthening gel and hence, the mechanical properties of the specimens do not reach the highest level. On the other hand, curing the specimens in water after 28 days produces more strengthening gel and results in a concrete with higher strength. The addition of nanoparticles improves the pore structure of concretes, thus, the refined extent of the pore structure increases with decreasing nanoparticle content. The pore structure of concrete cured in saturated limewater is better than that of concrete cured in water.
Effects of single-walled carbon nanotubes (SWNTs) on strengthening and toughening behaviors of aluminum-based composites with grain sizes ranging from nano- to micrometer have been investigated. The strength of composites is enhanced as an increase in SWNT volume and a decrease in grain size. Nanocrystalline composite containing 3.5 vol.% SWNTs exhibits good ductility of ∼5% tensile elongation to failure as well as superior yield stress of ∼600 MPa. However, the strengthening efficiency of SWNTs becomes half of the theoretical prediction for nanocrystalline composites due to the recovery process around the interface. Nanocrystalline composite containing 2.0 vol.% SWNTs shows the fracture toughness of ∼57 MPa mm1/2, which is five times higher than that of starting aluminum. SWNTs may effectively block the propagation of necks and cracks, providing much improved ductility and toughness.
In the present study, split tensile strength together with pore structure, thermal behavior and microstructure of concrete containing ground granulated blast furnace slag and SiO2 nanoparticles have been investigated. Portland cement was replaced by different amounts of ground granulated blast furnace slag and the properties of concrete specimens were measured. Although it negatively impacts the properties of concrete at early ages, ground granulated blast furnace slag was found to improve the physical and mechanical properties of concrete up to 45 wt% at later ages. SiO2 nanoparticles with the average particle size of 15 nm were partially added to concrete with the optimum content of ground granulated blast furnace slag and physical and mechanical properties of the specimens were studied. SiO2 nanoparticle as a partial replacement of cement up to 3 wt% could accelerate C–S–H gel formation as a result of increased crystalline Ca(OH)2 amount at the early age of hydration and hence increase split tensile strength of concrete specimens. The increased the SiO2 nanoparticles’ content more than 3 wt% causes the reduced the split tensile strength because of the decreased crystalline Ca(OH)2 content required for C–S–H gel formation. SiO2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.
The purpose of this study is to investigate the percentage of water absorption, velocity of water absorption, coefficient of water absorption, workability, and setting time of binary blended concrete with partial replacement of cement by 0.5, 1.0, 1.5, and 2.0 wt.% of Fe2O3 nanoparticles. The results showed that using Fe2O3 nanoparticles up to maximum replacement of 2.0% produces concrete with improved resistant to water permeability. Fe 2O3 nanoparticles can improve the filler effect and also the high pozzolanic action of fine particles increases substantially the quantity of C—F—H gel. If this phenomenon joints with low water-to-cement ratio, it can improve the microstructure in the interfacial transition zones and thus the value of C—F—H gel results in decreasing the water permeability. The results also show that the workability and setting time of fresh concrete were decreased by increasing the content of Fe2O 3 nanoparticles.
The purpose of this study is to investigate the percentage of water absorption, rate of water absorption, coefficient of water absorption, workability, and setting time of binary blended concrete with partial replacement of cement by 0.5, 1.0, 1.5, and 2.0 wt% of TiO2 nanoparticles with 15 nm. The results showed that the use of TiO2 nanoparticles up to maximum replacement level of 2.0 wt% produces concrete with improved resistant to water permeability. TiO2 nanoparticles can improve the filler effect and also the high pozzolanic action of fine nanoparticles increases substantially the quantity of strengthening gel. If this phenomenon joins with low water—cement ratio, it can improve the microstructure in the interfacial transition zones and thus the value of strengthening gel results in decreasing of the water permeability. Also, the workability and setting time of fresh concrete was decreased by increasing the content of TiO2 nanoparticles.
Research on the dispersion of pristine single-walled carbon nanotubes (SWCNTs) is mostly focused on measuring the dispersion limit in various organic solvents, yet little attention has been paid to the dispersion stability of SWCNTs in viable organic solvents. We have studied SWCNT dispersion stability for mixtures of the organic solvents N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidinone (NMP). Our results show that mixing DMF and NMP can yield dispersion stabilities that are 60–115% greater than the pure solvents with a 50/50 mixture (v/v). SWCNT aggregation is described by a physical model that combines the Maxwell–Boltzmann energy distribution function and DLVO theory for quantitative comparison between solvent systems.
Interplanetary dust particles accrete on the Earth at a rate of ~40 ktons yr-1. Some 90% of this material evaporates in the atmosphere, producing a bioavailable iron flux of 3x10-7 mol Fe m-2 yr-1. This extraterrestrial Fe flux is 30 - 300% of the eolian flux of bioavailable iron transported from terrestrial sources in remote marine regions and ~20% of the upwelled Fe flux in the Southern Ocean. Extraterrestrial Fe may play an important role in regulating the marine carbon cycle in these regions.
This review summarizes the most recent advances in multifunctional polymer nanocomposites reinforced by carbon nanotubes and aims to stimulate further research in this field. Experimental and theoretical investigations of the mechanical, thermal, and electrical properties of carbon nanotubes and their composite counterparts are presented. This review identifies the processing challenges associated with this class of materials and presents techniques that are currently being adopted to address these challenges and their relative merits. This review suggests possible future trends, opportunities, and challenges in the field and introduces the use of these multifunctional nanocomposites in structural health monitoring applications.
In the present study, the effect of limewater on strength and percentage of water absorption of Al2O3 nanoparticles blended concrete has been investigated. Portland cement was partially replaced by Al2O3 nanoparticles with the average particle size of 15nm with different amount and the specimens were cured in water and saturated limewater for specific ages. Utilizing up to 2.0wt% Al2O3 nanoparticles could produce concrete with improved strength and water permeability when the specimens cured in saturated limewater while this content is 1.0wt% for the specimens cured in tap water. The high action of fine nanoparticles substantially increases the quantity of C–S–H gel. Although the limewater reduces the strength of concrete without nanoparticles when compared with that cured in water, curing the specimens in saturated limewater results in more strengthening gel formation around Al2O3 nanoparticles and causes improved permeability together with high strength. In addition, Al2O3 nanoparticles are able to act as nanofillers and recover the pore structure of the specimens by decreasing harmful pores. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all indicate that Al2O3 nanoparticles could improve mechanical and physical properties of the specimens.
Using cement-based building materials as a matrix for nano-photocatalysts is an important development for the large scale application of photocatalytic technologies. Air pollution mitigation and self-cleaning surface are two major applications of photocatalytic building materials. In this study, a comparison was made to evaluate the performance of TiO2 modified concrete surface layers for NOx and VOC degradation. The self-cleaning performance of TiO2 modified self-compacting mortars (SCM) developed for decorative applications was also evaluated. The results show that the photocatalytic conversion of toluene by the TiO2 modified surface layer was not detected, although NOx could be effectively removed under the same conditions. The presence of toluene did not influence the NOx removal process. TiO2 modified SCM were found to be effective in the discoloration of rhodamine B under UV and strong halogen light irradiation. The level of adsorption of the air contaminants onto the active sites of the cement-TiO2 composite was identified to be the key factor determining the subsequent photocatalytic efficiency.
The influence of silica nanoparticles on the properties of systems of the cement-sand-water type was investigated experimentally.
Nanoparticles were separated from natural hydrothermal solutions according to the two-stage technological scheme including
membrane concentration and cryochemical vacuum sublimation drying of silica sols with the preparation of nanopowders. Silica
nanopowders with a particle size of 10–100 nm, a specific surface area of 100–400 m2/g, and an average pore diameter of 3–10 nm were introduced into the cement-sand-water system in amounts of 0.001–0.200 wt
% with respect to concrete. The nanopowders were mixed with water intended for tempering cement to obtain a stable suspension
with a uniform distribution of particles over the volume, which was introduced into the mixture of cement and sand. The characteristics
of the solid samples were measured at different ages from 3 to 28 days. It was established that the nanoadditive affects the
density, the rate of strength development, and the final compressive strength of cement samples.
Antireflection coatings with a low refractive index (1.18–1.23) have been prepared on silicate glass and optical quartz from
mesoporous silicon dioxide synthesized by the sol-gel method in the presence of oligoethers. The optimum concentration of
the oligoester in the sol is equal to 1.5–2.5 wt %. For the single-layer double-sided coating, the maximum transmission is
equal to 99.0% for the silicate glass and 99.9% for quartz.
We have investigated the effect of titanium dioxide as a durable finish on the flammability and photocatalytic self-cleaning
of cellulosic fabric. Nano-sized titanium dioxide particles were successfully synthesized and deposited onto cellulosic fibers
with good compatibility, significant photocatalytic self-cleaning activity, and flame-retardancy properties using the sol–gel
process at low temperature. The photocatalytic activity was tested by measuring the photodegradation of methylene blue under
ultraviolet–visible illumination, and also flame-retardancy effect was tested by flammability tester. The samples have been
characterized by several techniques such as scanning electron microscopy, transmission electron microscopy, diffuse reflectance
spectroscopy, X-ray diffraction, and thermogravimetric analysis. The titanium dioxide nanoparticles with 10–20 nm in size
have been found to form a homogeneous thin film on the fiber surface which shows efficient photocatalytic and flame-retardancy
properties. This preparation technique can also be applied to new fabrics to create self-cleaning and flame-retardancy properties
in them.
In the last 10 years Gesimat has developed a large-area electrochromic glazing with an advanced polymer electrolyte and tungsten oxide and Prussian Blue as complementary electrochromic layers. This electrochromic glass has a switching range between 75% and 8% visible transmittance and between 56% and 6% solar transmittance. The polymer electrolyte is based on polyvinyl butyral (PVB), a polymer in use as an interlayer for laminated safety glass since more than 60 years. The electrochromic films are deposited by a new large-area electrodeposition process. For lamination the standard methods of laminated safety glass production can be used.
This paper investigates the strain sensing properties of carbon black (CB)-filled cement-based composites which were prepared with 120nm CB. A linear relationship between the fractional change in resistivity and compressive strain was observed for cement-based composites containing a large amount of CB, suggesting that this kind of composite was a promising candidate for strain sensors used in concrete structures. Tunneling effect theory and percolation theory are employed to interpret the conductivity and electromechanical properties of CB-filled cement-based composites.
In this work, carbon nanotubes of 0.5 and 1% by weight were added for the first time in a fly ash cement system to produce carbon nanotubes–fly ash composites in the form of pastes and mortars. Compressive strengths of the composites were then investigated. It was found that the use of carbon nanotubes resulted in higher strength of fly ash mortars. The highest strength obtained for 20% fly ash cement mortars was found at 1% carbon nanotubes where the compressive strength at 28 days was 51.8MPa. This benefit can clearly be seen in fly ash cement with fly ash of 20% where the importance of the addition of carbon nanotubes means that the relative strength to that of Portland cement became almost 100% at 28 days. In addition, scanning electron micrographs also showed that good interaction between carbon nanotubes and the fly ash cement matrix is seen with carbon nanotubes acting as a filler resulting in a denser microstructure and higher strength when compared to the reference fly ash mix without CNTs.
The remarkable mechanical properties of carbon nanotubes (CNT) suggest that they are ideal candidates for high performance cementitious composites. The major challenge however, associated with the incorporation of CNTs in cement based materials is poor dispersion. In this study, effective dispersion of different length multiwall carbon nanotubes (MWCNTs) in water was achieved by applying ultrasonic energy and in combination with the use of a surfactant. The effects of ultrasonic energy and surfactant concentration on the dispersion of MWCNTs at an amount of 0.08wt.% of cement were investigated. It is shown that for proper dispersion the application of ultrasonic energy is absolutely required and for complete dispersion there exists an optimum weight ratio of surfactant to CNTs. For a constant ratio of surfactant to MWCNTs, the effects of MWCNT type (short and long) and concentration on the fracture properties, nanoscale properties and microstructure of nanocomposite materials were also studied. Results suggest that MWCNTs improve the nano- and macromechanical properties of cement paste.
Multiwall carbon nanotubes have been dispersed homogeneously throughout polystyrene matrices by a simple solution-evaporation method without destroying the integrity of the nanotubes. Tensile tests on composite films show that 1 wt % nanotube additions result in 36%-42% and ~25% increases in elastic modulus and break stress, respectively, indicating significant load transfer across the nanotube-matrix interface. In situ transmission electron microscopy studies provided information regarding composite deformation mechanisms and interfacial bonding between the multiwall nanotubes and polymer matrix.
The photocatalytic activities of cement pastes and mortars, containing various amounts of titanium dioxide (TiO2) in the anatase form, were evaluated and compared. The density, total porosity and pore size distribution of the materials were measured, and the amount of TiO2 being at their surfaces was estimated. The photocatalytic efficiency was evaluated by monitoring the discolouration of rhodamine B applied to the surface of the materials which were then exposed to artificial sun light; this evaluation was based on the use of a dimensionless specific activity coefficient. For TiO2 contents higher than 1wt% (up to 5wt%), cement pastes exhibited a photocatalytic activity higher than that of mortars because their activity was roughly proportional to the TiO2 content, whereas the activity of mortars levelled off. On the other hand, the type of cement used to prepare the materials had a low effect on the photocatalytic performances.
Heterogeneous photocatalysis has been intensively studied in recent decades because it only requires photonic energy to activate the chemical conversion contrasting with conventional catalysis which needs heat for thermo-activation. Over the years, the theories for photochemical activity of photocatalyst including photo-induced redox reaction and super-hydrophilic conversion of TiO2 itself have been established. The progress in academic research significantly promotes its practical applications, including the field of photocatalytic construction and building materials. TiO2 modified building materials are most popular because TiO2 has been traditionally used as a white pigment. The major applications of TiO2 based photocatalytic building materials include environmental pollution remediation, self-cleaning and self-disinfecting. The advantage of using solar light and rainwater as driving force has opened a new domain for environmentally friendly building materials. In this paper, the basic reaction mechanisms on photocatalyst surface under the irradiation of ultraviolet and their corresponding applications in building and construction materials are reviewed. The problems faced in practical applications and the trends for future development are also discussed.
Nickel powder-filled Portland cement-based composite was prepared by adding nickel powder as functional filler into conventional Portland cement-based materials, and piezoresistive sensors were fabricated by embedding four loop electrodes in the nickel powder-filled Portland cement-based composite. The relationship between the fractional change in electrical resistivity and the stress/strain of piezoresistive sensors was established for the compressive stress and was found to be in the range from 0 to 12.5MPa. Experimental results indicate that the electrical resistivity of nickel powder-filled Portland cement-based composite under uniaxial compression decreases by 62.6144% within elastic regime, which justifies the use of this composite in the fabrication of piezoresistive sensors with high sensitivity to stress and sensitivity to strain (gauge factor). The sensitivity of piezoresistive sensors to compressive stress is higher than 0.050092MPa−1 and goes up to 0.123648MPa−1. The gauge factor of piezoresistive sensors is higher than 895.450 and goes up to 1929.500. It is therefore concluded that the newly developed piezoresistive sensors have a high sensitivity to stress/strain, and they can be used for measurement of stress/strain or force/deformation.
THE continuity of the liquid permeating jellies is demonstrated by diffusion, syneresis, and ultrafiltration, and the fact that the liquid may be replaced by other liquids of very diverse character indicates clearly that the gel structure may be independent of the liquid in which it is bathed. Hitherto the attempt to remove the liquid by evaporation has resulted in shrinkage so great that the effect upon the structure may be profound.
Studies of dispersion and related properties, in carbon nanotube/epoxy composites, were conducted using electro-micromechanical and wettability tests. Specimens were prepared from neat epoxy as well as composites with untreated and acid-treated carbon nanotube (CNT). The degree of dispersion and its standard deviation were evaluated by turbidity of the dispersing solution, as well as by volumetric electrical resistivity. Acetone was a better dispersing solvent than purified water and various acid treatments of the CNT also enhanced dispersion. Contact resistivity responded differently with dispersion degree. The apparent Young's modulus was higher for composites with acid treated CNT. The interfacial shear strength between a single carbon fiber and CNT/epoxy was lower than that between a single carbon fiber and neat epoxy. This difference is attributed to increased viscosity and decreased bonding availability in the matrix due to the added CNT. The optimum CNT treatment, for maximizing interfacial adhesion while maintaining good electrical conductivity was the sulfuric acid treatment. The CNT composites can also sense micro-damage in terms of the stepwise increments of electrical resistivity combined with acoustic emission.
CBCC sensor, a kind of cement-based strain sensor, has been developed by utilizing the piezoresistivity of carbon black filled cement-based composite (CBCC11CBCC – Carbon black filled cement-based composite.) and the strain sensing property of a free CBCC sensor has been explored. In this paper, CBCC sensors are embedded at three different stress zones in a bending beam, i.e. uniaxial compression, combined compression and shear, and uniaxial tension to investigate the strain sensing properties of embedded CBCC sensors under these stress states. The experimental results show that the precision of embedded CBCC sensors for measuring compressive strain is as good as that of a free CBCC sensor, no matter shear stress exists or not, indicating the precision of embedded CBCC sensors is nearly insensitive to shear stress. The adverse influence of shear stress is reducing the sensing range of embedded CBCC sensors because existing of shear stress will decrease the maximum compressive strain. Embedded CBCC sensors under uniaxial tension show good tensile strain sensing properties before they are crushed.
In this work, strength assessments and percentage of water absorption of self compacting concrete containing different amounts of ground granulated blast furnace slag and TiO2 nanoparticles as binder have been investigated. Portland cement was replaced by 45wt% of ground granulated blast furnace slag and up to 4.0wt% TiO2 nanoparticles and the properties of concrete specimens were investigated. TiO2 nanoparticle as a partial replacement of cement up to 3.0wt% could accelerate C–S–H gel formation as a result of increased crystalline Ca(OH)2 amount at the early age of hydration and hence increase strength and improve the resistance to water permeability of concrete specimens. Several empirical relationships have been presented to predict flexural and split tensile strength of the specimens by means of the corresponding compressive strength at a certain age of curing.
Measurements of aerosol extinction at wavelengths of 0.525 and 1.02 μm, made by the Stratospheric Aerosol and Gas Experiment (SAGE) II solar occultation satellite experiment, have been used to study the global-scale characteristics of the upper tropospheric aerosol. Extinction measurements in which only aerosols occurred along the optical path, have been separated from those that included high-altitude cloud by examining the wave-length variation of the extinction. Data for the time period October 1984 to May 1991 show that the two main influences on the upper tropospheric aerosol were seasonal lifting of material from below and downward transfer of volcanic aerosol from the stratosphere. -from Authors
The flexural fatigue performance of concrete containing nano-particles for pavement is experimentally studied. Both nano-TiO2 and nano-SiO2 are respectively employed to be as the additives. For comparison, the flexural fatigue performance of plain concrete and the concrete containing polypropylene (PP) fibers is also experimentally studied in this article. The test results indicate that the fatigue lives of concretes containing nano-particles follow the double-parameter Weibull distribution. The flexural fatigue performance of concretes containing nano-particles is improved significantly and the sensitivity of their fatigue lives to the change of stress is also increased. The theoretic fatigue lives of concretes containing nano-particles are enhanced in different extent. With increasing stress level, the enhanced extent of theoretic fatigue number is increased. The concrete containing nano-TiO2 in the amount of 1% by weight of binder has the best flexural fatigue performance, which is much better than that of the concrete containing PP fibers, which has been extensively used to improve the fatigue performance of concrete in pavement. The theoretic stress level of the concrete containing nano-TiO2 in the amount of 1% by weight of binder is enhanced compared with plain concrete when the fatigue failure number is equal to 106.
Antifogging mirror or self-cleaning glass can be realized utilizing photoinduced hydrophilicity of titanium dioxide. Application fields of functional titanium dioxide coating is now expanding rapidly not only in applications for glass but also in applications for polymer, metal and ceramic materials. The high hydrophilic surface of TiO2 is interesting also on the standpoint of the basic photon related surface science of titanium dioxide. In order to understand the photoinduced hydrophilic conversion on titanium dioxide coating in details, it is inevitably necessary to understand the relationship between the photo reaction and the surface crystal structure. In this paper, photoinduced hydrophilic conversion was evaluated on the different crystal faces of rutile single crystal and also polycrystalline anatase titanium dioxide to clarify the dependence of the crystal structure on the photoinduced hydrophilic conversion.
Reductive energy generated at a TiO2 photocatalyst under UV light can be stored in WO3 by coupling them together, and the stored energy can be used after dark. However, the reduction of WO3 requires cation intercalation for charge neutralization. Thus, behavior of the TiO2−WO3 composite on an ITO electrode was examined in nonelectrolytic media. When the TiO2 and WO3 were close to each other (less than 1 mm), WO3 could be reduced even in pure water or humid air (relative humidity ≥25%), by irradiating the composite with UV light. In dry air, WO3 was not reduced efficiently, even if the TiO2 and WO3 nanoparticles were mixed well. These results suggest that protons generated at the TiO2 surface as a result of photocatalytic oxidation of water are intercalated into WO3, and therefore ionic conductivity of the medium or the composite film surface is important. The composite film charged in air exhibited almost the same electrode potential as that of the film charged in aqueous NaCl.
Fe-doped TiO2 films are prepared by pulse dc reactive magnetron sputtering. Iron concentration is controlled by varying the surface area of Fe pieces fixed on the pure titanium target. TiO2 films are in anatase phase when iron concentration is less than 10 at.%. Only Ti(IV) is found in the pure TiO2 film while Fe-doped TiO2 films show mixed titanium oxidation states. The absorption edges of Fe-doped TiO2 films show red shift. The films with low iron concentrations perform better photocatalytic activity than the pure TiO2 film and the best doped iron concentration is 0.58 at.%.