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Nanoparticle research disciplines - chemical synthesis, applied physics and devices based on their physical-chemical properties, and computational physics - have been very active fields for the last 15 years or so, because of the potential and current applications in medicine, catalysis, energy storage, environment and electronics applications. Thi...
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Nanoparticle research is currently an area of intense scientific interest, due to a wide variety of potential applications in biomedical, optical, and electronic fields. A nanoparticle (or nanopowder or nanocluster or nanocrystal) is a microscopic particle with at least one dimension less than 100 nm. Metallic nanoparticles have fascinated scientis...
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... In our MD experiments [35], it has been shown that, as temperature is elevated, nanowires become unstable and are transformed into globular nanoparticles. At the same time, as has been noted in [37], the shape and structure of polyhedral metal nanoclusters are closely interrelated. ...
After briefly discussing the problem of stability/instability of dispersed systems in colloid chemistry, including ideas and concepts dating back to P.A. Rehbinder, the following classification has been proposed for instabilities of individual (free) nanoparticles: (1) instability with respect to the spontaneous disintegration into individual molecules (atoms) or smaller nanoclusters; (2) instability of shape; (3) instability of the integral structure of nanoparticles; (4) instability of the mesoscopic structure; (5) instability of physicochemical characteristics of nanoparticles; and (6) instability with respect to an external environment, including chemical instability, e.g., instability to oxidation. The problems concerning the stability of isomers of metal nanoclusters and of bimetallic core-shell nanostructures are considered as examples. The theoretical concepts of stability and instability have been illustrated by our molecular dynamics data on isomers of Au nanoclusters and mutually inverse (alternative) bimetallic Co@Au and Au@Co core-shell nanostructures, where the first element (before symbol @) corresponds to the central region (core) of a particle, while the second one refers to its shell.
... The zeta potential manifests the stability factor and is considered viable in both the positive and the negative modes of measurement within the median values of 40-60 mV. Smaller sized, spherical particles and nano-preparations are considered to be stable, and the zeta potential, a dispersion stability indicator, together with the other parameters of pH, ionic strength, concentration of the medium [112][113][114][115], and polydispersity contribute to the stability of nano-systems composed of metallic NPs and their conjugates. Lower sizes of the nano-preparations have been favored; nonetheless, a median size under or around 100-150 nm has been considered better for loading larger drug quantities for effective and dose-maneuvered delivery. ...
Considerable efforts have been directed towards development of nano-structured carriers to overcome the limitations of anticancer drug, doxorubicin's, delivery to various cancer sites. The drug's severe toxicity to cardio and hepatic systems, low therapeutic outcomes, inappropriate dose-demands, metastatic and general resistance, together with non-selectivity of the drug have led to the development of superparamagnetic iron oxide nanoparticles (SPIONs)-based drug delivery modules. Nano-scale polymeric co-encapsulation of the drug, doxorubicin, with SPIONs, the SPI-ONs surface end-groups' cappings with small molecular entities, as well as structural modifications of the SPIONs' surface-located functional end-groups, to attach the doxorubicin, have been achieved through chemical bonding by conjugation and cross-linking of natural and synthetic polymers , attachments of SPIONs made directly to the non-polymeric entities, and attachments made through mediation of molecular-spacer as well as non-spacer mediated attachments of several types of chemical entities, together with the physico-chemical bondings of the moieties, e.g., peptides, proteins, antibodies, antigens, aptamers, glycoproteins, and enzymes, etc. to the SPIONs which are capable of targeting multiple kinds of cancerous sites, have provided stable and functional SPIONs-based nano-carriers suitable for the systemic, and in vitro deliveries, together with being suitable for other biomedical/biotechnical applications. Together with the SPIONs inherent properties, and ability to respond to magnetic resonance, fluorescence-directed, dual-module, and molecular-level tumor imaging; as well as multi-modular cancer cell targeting; magnetic-field-inducible drug-elu-tion capacity, and the SPIONs' magnetometry-led feasibility to reach cancer action sites have made sensing, imaging, and drug and other payloads deliveries to cancerous sites for cancer treatment a viable option. Innovations in the preparation of SPIONs-based delivery modules, as biocompatible carriers; development of delivery route modalities; approaches to enhancing their drug delivery-cum-bioavailability have explicitly established the SPIONs' versatility for oncological theranostics and imaging. The current review outlines the development of various SPIONs-based nano-carriers for targeted doxorubicin delivery to different cancer sites through multiple methods, modalities, and materials, wherein high-potential nano-structured platforms have been conceptualized, developed , and tested for, both, in vivo and in vitro conditions. The current state of the knowledge in this arena have provided definite dose-control, site-specificity, stability, transport feasibility, and effective onsite drug de-loading, however, with certain limitations, and these shortcomings have opened the field for further advancements by identifying the bottlenecks, suggestive and plausible remedi-ation, as well as more clear directions for future development. Citation: Akhtar, N.; Mohammed, H.A.; Yusuf, M.; Al-Subaiyel, A.; Sulaiman, G.M.; Khan, R.A. SPIONs
... Synthesis methods play a huge role in designing well-defined nanomaterials with uniform and monodisperse morphology [19]. Recently it was found that the size of nanoparticles (NPs) plays an important role in dictating their stability and various biological and physicochemical properties [20][21][22][23]. Particularly, in the area of luminescent NPs, their size is of utmost importance as they control defect density, amount of aggregation, surface texture, surface roughness, etc. [23], which indirectly influence their luminescence properties. ...
Size tunable nanoaprticles (NPs) have played an important role in areas of optoelctronics, drug delivery, magnetism and many others. Moreover, designing size-tunable NPs without exposing them to high temperature and long time thermal tratement is highly desirable to make agglomerate-and defect-free NPs. In this work, we have designed Gd 2 Hf 2 O 7 :Eu 3+ (GHOE) NPs using the molten-salt synthesis (MSS) method with the precursors made from varying precipitant concentrations (correspondingly the pH of the precipitating solution). The obtained NPs have a decreasing size as the pH of the precipitating solution rises and a defect fluorite structure with a large fraction of Eu 3+ ions localized at GdO 8 distorted scalenohedra, a small fraction residing at Hf 4+ site, and the presence of oxygen vacacnies in the vicinity of. Maximum photoluminescence and radioluminescence outputs and internal quantam yield have been observed from the GHOE NPs made from 5.0% NH 4 OH as precipitant due to optimum balance of surface defects and particle clustering. Judd-Ofelt analysis has confirmed that these GHOE NPs have lowest non-radiative transition probability, brightest red emission, largest branching ratio, and highest radiative transition rate. With increasing pH of the precipitating solution, the group symmetry of Eu 3+ ions in the GHOE host decreases systematically from D 4 → C 4v → C 3v and then saturates, consistent with the pH dependent asymmetry ratio value. Also, the extent of polarizability enhances and the Eu-O bond becomes more covalent as confirmed by the monotonic increase of Ω 2 /Ω 4 ratio. Our work on these optical materials will assist the scientific community to make size-tunable nanoparticles at low synthesis temperature for efficient luminescent devices.
... The main limitation related to the synthesis and application of various types of nanopowders, obviously including nano ZnO, is the problem of repeatability of parameters of nanopowders. Most "wet methods" [73,76,86,111] used for producing metal oxide nanoparticles lead to obtaining powders with The properties of nanostructures depend strongly on their size and shape [40][41][42][43][44][45][46][47][48][49][50]. The sizedependent effect of ZnO NPs has been observed on the: photocatalytic activity [337][338][339][340][341][342], catalyst activity [343], dielectric properties [344], piezoelectric property [345,346], breakdown voltage varistors [347], visible emission property of quantum dots displays [348], equilibrium constant of chemical reactions [349], gas sensing properties [350][351][352], thermal diffusivity of water nanofluid [353], photoluminescence [354], UV absorption [355,356], biomedical potential [357], toxicity [312,328,[357][358][359][360][361][362], bioavailability [363], and interactions with biomatrices [364]. ...
Zinc oxide (ZnO) is a multifunctional material due to its exceptional physicochemical properties and broad usefulness. The special properties resulting from the reduction of the material size from the macro scale to the nano scale has made the application of ZnO nanomaterials (ZnO NMs) more popular in numerous consumer products. In recent years, particular attention has been drawn to the development of various methods of ZnO NMs synthesis, which above all meet the requirements of the green chemistry approach. The application of the microwave heating technology when obtaining ZnO NMs enables the development of new methods of syntheses, which are characterised by, among others, the possibility to control the properties, repeatability, reproducibility, short synthesis duration, low price, purity, and fulfilment of the eco-friendly approach criterion. The dynamic development of materials engineering is the reason why it is necessary to obtain ZnO NMs with strictly defined properties. The present review aims to discuss the state of the art regarding the microwave synthesis of undoped and doped ZnO NMs. The first part of the review presents the properties of ZnO and new applications of ZnO NMs. Subsequently, the properties of microwave heating are discussed and compared with conventional heating and areas of application are presented. The final part of the paper presents reactants, parameters of processes, and the morphology of products, with a division of the microwave synthesis of ZnO NMs into three primary groups, namely hydrothermal, solvothermal, and hybrid methods.
... Therefore, they are quite distinct from their conventional counter-parts as far as their optical, electrical, magnetic, mechanical and catalytic behaviors are concerned. This makes them suitable for the development of biosensors [30][31][32][33]. Additionally, they are often used for signal amplification by serving as nanocarriers including electron transfer promoters, nanozymes, detector bioreceptors, electroactive labeling elements, and catalysts [34][35][36][37], hence offering novel strategies for biosensing platforms and their practical applicability. ...
Due to the proliferative cancer rates, cardiovascular diseases, neurodegenerative disorders, autoimmune diseases and a plethora of infections across the globe, it is essential to introduce strategies that can rapidly and specifically detect the ultralow concentrations of relevant biomarkers, pathogens, toxins and pharmaceuticals in biological matrices. Considering these pathophysiologies, various research works have become necessary to fabricate biosensors for their early diagnosis and treatment, using nanomaterials like quantum dots (QDs). These nanomaterials effectively ameliorate the sensor performance with respect to their reproducibility, selectivity as well as sensitivity. In particular, graphene quantum dots (GQDs), which are ideally graphene fragments of nanometer size, constitute discrete features such as acting as attractive fluorophores and excellent electro-catalysts owing to their photo-stability, water-solubility, biocompatibility, non-toxicity and lucrativeness that make them favorable candidates for a wide range of novel biomedical applications. Herein, we reviewed about 300 biomedical studies reported over the last five years which entail the state of art as well as some pioneering ideas with respect to the prominent role of GQDs, especially in the development of optical, electrochemical and photoelectrochemical biosensors. Additionally, we outline the ideal properties of GQDs, their eclectic methods of synthesis, and the general principle behind several biosensing techniques.
... Enduringly, these nanomaterials constitute discrete biological and physicochemical properties compared to their conventional counterparts, which bestow them favorable characteristics for the fabrication of biosensors. They exhibit surface effects, small size effects, and macroscopic quantum tunneling effects, hence they have unique mechanical, electrical, optical, magnetic, and catalytic properties as compared to the bulk materials [27][28][29][30]. Moreover, they have also been employed as nanocarriers for signaling elements (detector bioreceptors, enzymes, and/or electroactive label), as catalysts and electron transfer promoters for signal amplification [31][32][33][34], thus providing new approaches for the development and application of bioelectrochemical sensors. ...
In the area of biomedicine, research for designing electrochemical sensors has evolved over the past decade, since it is crucial to selectively quantify biomarkers or pathogens in clinical samples for the efficacious diagnosis and/or treatment of various diseases. To fulfil the demand of rapid, specific, economic, and easy detection of such biomolecules in ultralow amounts, numerous nanomaterials have been explored to effectively enhance the sensitivity, selectivity, and reproducibility of immunosensors. Graphene quantum dots (GQDs) have garnered tremendous attention in immunosensor development, owing to their special attributes such as large surface area, excellent biocompatibility, quantum confinement, edge effects, and abundant sites for chemical modification. Besides these distinct features, GQDs acquire peroxidase (POD)-mimicking electro-catalytic activity, and hence, they can replace horseradish peroxidase (HRP)-based systems to conduct facile, quick, and inexpensive label-free immunoassays. The chief motive of this review article is to summarize and focus on the recent advances in GQD-based electrochemical immunosensors for the early and rapid detection of cancer, cardiovascular disorders, and pathogenic diseases. Moreover, the underlying principles of electrochemical immunosensing techniques are also highlighted. These GQD immunosensors are ubiquitous in biomedical diagnosis and conducive for miniaturization, encouraging low-cost disease diagnostics in developing nations using point-of-care testing (POCT) and similar allusive techniques.
... Effect of size and surface chemistry of nanoparticle shapes was studied Albanese et al. [21] on biological systems. Geometrical description of metallic nanoparticles was presented by Rodriguez-Lopez et al. [22]. Jo et al. [23] investigated therapeutic effect of nanoparticles size, surface charge and shapes on brain and 42 retinal diseases. ...
... Therefore it is required to adopt either numerical or analytical methods to generate solutions to the system of coupled equation. Hence analytical and numerical methods have been utilized by researchers in solving nonlinear problems in science and engineering [19][20][21][22][23][24][25][26][27][28][29][30][31]. ...
In this paper the geometry effects of different nanoparticles such as cylindrical, spherical and lamina on heat transfer of fluid transported through contracting or expanding micro channel are considered. The nanofluid flow and heat transfer through the porous channel are described using mathematical models. Since the mathematical models are nonlinear in nature the homotopy perturbation method (HPM), an approximate analytical method is adopted to provide solution to the mathematical model. The fast convergence rate coupled with analytical procedural stability motivates the use of the HPM as the favored method in providing solutions to the system of coupled, higher order differentials.The obtained analytical solution is used to investigate the influence of particle shape of the nano sized materials on heat transfer of fluid flowing through a porous medium considering a uniform magnetic field. It is illustrated from results that lamina nanoparticle shape shows higher dimensionless temperature and thermal conductivity when compared with nano shaped particles of cylinder and sphere respectively due to variations in thermal boundary layers. Results obtained from this study prove useful in the advancement of science and technology including micro mixing, nanofluidics and energy conservation. Comparing obtained analytical solution with fourth order numerical solution, good agreement was established.
This Review examines parts per million (ppm) palladium concentrations in catalytic cross-coupling reactions and their relationship with mole percentage (mol %). Most studies in catalytic cross-coupling chemistry have historically focused on the concentration ratio between (pre)catalyst and the limiting reagent (substrate), expressed as mol %. Several recent papers have outlined the use of "ppm level" palladium as an alternative means of describing catalytic cross-coupling reaction systems. This led us to delve deeper into the literature to assess whether "ppm level" palladium is a practically useful descriptor of catalyst quantities in palladium-catalyzed cross-coupling reactions. Indeed, we conjectured that many reactions could, unknowingly, have employed low "ppm levels" of palladium (pre)catalyst, and generally, what would the spread of ppm palladium look like across a selection of studies reported across the vast array of the cross-coupling chemistry literature. In a few selected examples, we have examined other metal catalyst systems for comparison with palladium.
