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A multi-walled carbon nanotube (MWCNT)/hexamethylene diisocyanate (HDI) composite coating with excellent
microstructural homogeneity was produced on copper substrate from aqueous suspensions using
electrophoretic deposition (EPD). The concentrations of different additives were optimized to obtain stable
suspensions of MWCNT. At the optimum EPD cond...
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... and polymer as thin fi lm from its colloidal suspensions, by electrophoretic deposition (EPD). EPD is a colloidal forming technique where charged, colloidal particles in a stable suspension are deposited onto an oppositely charged substrate by the application of electric fi eld [16]. It is commonly employed in processing of ceramics, coating, and composite [17 – 20]. EPD is very versatile, fast, and cost effective to produce coating of controlled micro- structure on a wide range of substrates. The process can be applied, in general to any solid in particulate form with small particles ( b 30 μ m) and to colloidal suspensions [21]. EPD is a very powerful tool for the ordered deposition of CNT and CNT-based nanostructures for a variety of applications, including (i) catalyst supports (ii) structural composites and coating (iii) gas sensor (iv) capacitor (v) biomedical scaffold (vi) electrode for fuel cells (vii) actuators and (viii) fi eld emission devices, [19,21 – 24]. Most of the above research used organic solvents or mixture of organic solvent and resin to prepare composite [23,24]. Re- cently, Thomas et.al, [20] used aqueous EPD to obtain MWCNT coating of about 10 micron thickness at 40 V and 4 min deposition time. In ma- jority of cases, EPD is reported to use organic/mixture of organic solvent as vehicle, which is not only hazardous but also polluting the environment and dangerous for sea species, when it is used in seawater. Research effort is being made to develop aqueous based EPD [20,25,26] to minimize the uses of organic solvent. Present investigation is an attempt in that direction, it not only involved aqueous processing but also used dispersant which is a natural polysaccharide of plant origin. A major part of metallic constructions exposed to seawater and marine atmospheres are destroyed, due to the corrosion phenomena. Copper is one of the essential structural engineering materials widely used in chemical industry, pipelines for domestic and industrial utili- ties, heat conductors, heat exchangers, electronic industry, communi- cation industry including seawater (marine environment) owning to its mechanical workability and other properties [27]. Under intense seawater/marine environment, the copper form thin layers of corrosion products, generally dark-brown to green-bluish colour, chemi- cally known as copper hydroxide and copper carbonate, copper sulphate etc. depending upon exposure time, and presence of pollut- ants in the surrounding environment, which is technically also known as patina [28]. Copper ions being very sensitive to chloride ions, even presence of trace amount can cause corrosion at very signi fi cant rate in sea water and form unstable fi lms of CuCl and soluble chloride complexes [27]. The conventional treatment approach is based on hydrophobic polymer paints coating or self assembled monolayer [27]; however, they have their own limitations, fi rst and foremost is very short life span of coating and therefore, one has to go for coating very often, multistep, and tedious. Sometimes polymeric resin paints contains toxic substances like (chromium etc) which is very harmful to the environment. Nanostructure materials engineering extends the possibility of designing environmentally friendly anti-corrosion engineering ‘ smart ’ coatings which can last much longer compared to traditional coatings. CNT-reinforced polymer nanocomposite based protective coatings are attractive options for marine environment applications due to their excellent properties and unlimited possibilities of tailoring their chemical, physical and processing behavior to meet the requirement. CNT-reinforced nanocomposite coatings guard the substrate by providing a tough protective shield that can lock out de- structive elements and keeping it resilient and durable for very longer period of time, which cannot be met by the traditional micrometer hydrophobic polymer/self-assembled monolayer coatings. The speci fi c aim of the present work is to fabricate MWCNT/ hexamethylene diisocyanate (HDI) composite coating by EPD from aqueous suspensions for possible potential application in stringent marine environment to protect copper based structure from oxida- tion and further corrosion. In this study HDI has been reported as polymeric matrix for the fi rst time. The in fl uence of dispersant and polymeric resin on improving the adhesive strength of the MWCNT/HDI composite coating on copper substrate will be examined. The most plausible mechanism of coatings by combination of MWCNT and polymeric resin (HDI) on copper substrate has been proposed. MWCNT was purchased from Sigma-Aldrich Chemie, GmbH, Stein- heim, Germany, with diameter range of 110 – 170 nm and average length 5 – 9 μ m as reported by the supplier (Fig. 1). The Scanning electron microscopy (SEM) image of pristine MWCNT showed large number of cross-linking and entanglements. The entanglement could be broken to large extent by addition of dispersant. Fig. 2 shows well dispersed MWCNT in presence of dispersant Gum Arabic (GA). GA used as dispersant is a highly branched polysaccharide and is known for its dispersion property. HDI is an organic polymeric resin generally used in special applications such as enamel coating which are resistant to abrasion and degradation from UV light. The as received MWCNT was further characterized by the Raman spectroscopy (Fig. 2). The D-band (1353 cm − 1 ), G-band (1575 cm − 1 ) and D ’ -band, the second order overtone of D-band (2696 cm − 1 ), con fi rms the typical characteristics of multiwall carbon nanotube. Preparation of well dispersed suspension, free from agglomerates, is a prerequisite for obtaining uniform, homogeneous and crack free deposit by EPD. 0.1 wt.% of MWCNT suspension was prepared in aqueous solution by adding pre-optimized quantities of GA and HDI, combination (600 mg/g) and (0.27 mg/g) respectively. Dispersant is selected in such a manner so that there should be synergy between dispersant and polymeric resin. The suspension was ultrasonicated at 160 kW for 30 min to break the agglomerates. Sedimentation of the particles was prevented by mild stirring by using a magnetic stirrer. Electrophoretic deposition of MWCNT/HDI on the copper substrate was carried out using the deposition set up as shown in Fig. 3. Two par- allel copper plates (9 mm× 30 mm) separated by 10 mm gap were used as the electrodes. One of them works as depositing substrate (cathode) and other as the counter electrode. The suspension was ultrasonicated for about 20 min just before the EPD experiments. EPD was carried out at constant voltage mode at DC voltage between 10 and 30 V, using a source meter (Model: 2410, Keithley Instruments, Inc, USA) for deposition time of 0.5 – 5 min. Once deposition is over, the deposit was taken out carefully vertically along with the substrate. The sample was then allowed to dry upright position overnight at room temperature and weighed to determine the deposit yield and the products are ready for characterization. The electrochemical experiments were carried out using potentiostat (Model: Versastat-3, Prinston Applied Research, USA) with a three electrode electrochemical cell. The Cu-electrode embedded in the epoxy resin served as the working electrode, Pt as counter electrode and standard Ag/AgCl as reference electrode. The working electrode with exposed area 1 cm 2 was stabilized in 3.5% NaCl solution at room temperature (35 °C). The open circuit potential (OCP) was monitored continuously till the steady state was reached. The polarization plot was recorded at a scan rate of 1 mV/s within a scan range of +1 V to − 1 V. The corrosion potential (E corr ) and corrosion current density (I corr ) was computed by Tafel extrapolaration technique from polarization plot. The microstructural and morphological characterization of MWCNT and composite samples were carried out using Scanning Electron Microscope (Model: Hitachi, S-3400 N,Tokyo, Japan). The Raman scattering experiments were carried out using a Renishaw Im- aging Microscope WiRE spectroscopy (Model: Invia Re fl ex-H33197, Incoterm, UK) equipped with air cooled CCD detector. The spectra of powder samples of MWCNT were measured over a scanning range of 0 – 3250 cm − 1 with incident argon laser excitation wavelength of 514 nm. The speci fi c surface charge of MWCNT suspension measurements were carried out with Particle Charge Detector (PCD), Model: PCD-04-pH from Herrsching, Muteck, Germany. The anti-corrosion property of MWCNT reinforced polymer coating fi lms were investigated using potentiostat (Model: Versastat-3, Prinston Applied Research, USA). Fig. 4.(a, b and c) shows the optimization of concentration of dispersant GA, polymeric resin, HDI and combination thereof using Particle Charge Detector (PCD), the details of which described elsewhere [29,30]. The variation of PCD potential as function of different concentration is plotted and the in fl ection point in the graph gives the optimum concentration required for stable dispersion. The initial increase in PCD potential occurs due to increase in speci fi c charge due to adsorbed additives on MWCNT surface with increasing concentration of dispersant. Once the surface is covered completely (monolayer coverage), that quantity gives the overall maximum stability and optimized chemical additives dosages. The unadsorbed excess remains in the solution and may affect viscosity of the solution without affect- ing PCD potential. The measured optimum dosages of GA, HDI and GA and HDI combination were 600 mg/g (Fig. 4.a), 0.2 mg/g (Fig. 4.b) and 0.27 mg/g (Fig. 4.c), respectively. This technique is very easy, accurate and useful for the assessment of stability of nanoparticles suspensions and determination of optimum dispersant concentration for nano- ceramics and polyelectrolyte systems. [31 – 33]. The quantum of surface charge density on any particulate matter in aqueous suspension is an important ...
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... effective to produce coating of controlled micro- structure on a wide range of substrates. The process can be applied, in general to any solid in particulate form with small particles ( b 30 μ m) and to colloidal suspensions [21]. EPD is a very powerful tool for the ordered deposition of CNT and CNT-based nanostructures for a variety of applications, including (i) catalyst supports (ii) structural composites and coating (iii) gas sensor (iv) capacitor (v) biomedical scaffold (vi) electrode for fuel cells (vii) actuators and (viii) fi eld emission devices, [19,21 – 24]. Most of the above research used organic solvents or mixture of organic solvent and resin to prepare composite [23,24]. Re- cently, Thomas et.al, [20] used aqueous EPD to obtain MWCNT coating of about 10 micron thickness at 40 V and 4 min deposition time. In ma- jority of cases, EPD is reported to use organic/mixture of organic solvent as vehicle, which is not only hazardous but also polluting the environment and dangerous for sea species, when it is used in seawater. Research effort is being made to develop aqueous based EPD [20,25,26] to minimize the uses of organic solvent. Present investigation is an attempt in that direction, it not only involved aqueous processing but also used dispersant which is a natural polysaccharide of plant origin. A major part of metallic constructions exposed to seawater and marine atmospheres are destroyed, due to the corrosion phenomena. Copper is one of the essential structural engineering materials widely used in chemical industry, pipelines for domestic and industrial utili- ties, heat conductors, heat exchangers, electronic industry, communi- cation industry including seawater (marine environment) owning to its mechanical workability and other properties [27]. Under intense seawater/marine environment, the copper form thin layers of corrosion products, generally dark-brown to green-bluish colour, chemi- cally known as copper hydroxide and copper carbonate, copper sulphate etc. depending upon exposure time, and presence of pollut- ants in the surrounding environment, which is technically also known as patina [28]. Copper ions being very sensitive to chloride ions, even presence of trace amount can cause corrosion at very signi fi cant rate in sea water and form unstable fi lms of CuCl and soluble chloride complexes [27]. The conventional treatment approach is based on hydrophobic polymer paints coating or self assembled monolayer [27]; however, they have their own limitations, fi rst and foremost is very short life span of coating and therefore, one has to go for coating very often, multistep, and tedious. Sometimes polymeric resin paints contains toxic substances like (chromium etc) which is very harmful to the environment. Nanostructure materials engineering extends the possibility of designing environmentally friendly anti-corrosion engineering ‘ smart ’ coatings which can last much longer compared to traditional coatings. CNT-reinforced polymer nanocomposite based protective coatings are attractive options for marine environment applications due to their excellent properties and unlimited possibilities of tailoring their chemical, physical and processing behavior to meet the requirement. CNT-reinforced nanocomposite coatings guard the substrate by providing a tough protective shield that can lock out de- structive elements and keeping it resilient and durable for very longer period of time, which cannot be met by the traditional micrometer hydrophobic polymer/self-assembled monolayer coatings. The speci fi c aim of the present work is to fabricate MWCNT/ hexamethylene diisocyanate (HDI) composite coating by EPD from aqueous suspensions for possible potential application in stringent marine environment to protect copper based structure from oxida- tion and further corrosion. In this study HDI has been reported as polymeric matrix for the fi rst time. The in fl uence of dispersant and polymeric resin on improving the adhesive strength of the MWCNT/HDI composite coating on copper substrate will be examined. The most plausible mechanism of coatings by combination of MWCNT and polymeric resin (HDI) on copper substrate has been proposed. MWCNT was purchased from Sigma-Aldrich Chemie, GmbH, Stein- heim, Germany, with diameter range of 110 – 170 nm and average length 5 – 9 μ m as reported by the supplier (Fig. 1). The Scanning electron microscopy (SEM) image of pristine MWCNT showed large number of cross-linking and entanglements. The entanglement could be broken to large extent by addition of dispersant. Fig. 2 shows well dispersed MWCNT in presence of dispersant Gum Arabic (GA). GA used as dispersant is a highly branched polysaccharide and is known for its dispersion property. HDI is an organic polymeric resin generally used in special applications such as enamel coating which are resistant to abrasion and degradation from UV light. The as received MWCNT was further characterized by the Raman spectroscopy (Fig. 2). The D-band (1353 cm − 1 ), G-band (1575 cm − 1 ) and D ’ -band, the second order overtone of D-band (2696 cm − 1 ), con fi rms the typical characteristics of multiwall carbon nanotube. Preparation of well dispersed suspension, free from agglomerates, is a prerequisite for obtaining uniform, homogeneous and crack free deposit by EPD. 0.1 wt.% of MWCNT suspension was prepared in aqueous solution by adding pre-optimized quantities of GA and HDI, combination (600 mg/g) and (0.27 mg/g) respectively. Dispersant is selected in such a manner so that there should be synergy between dispersant and polymeric resin. The suspension was ultrasonicated at 160 kW for 30 min to break the agglomerates. Sedimentation of the particles was prevented by mild stirring by using a magnetic stirrer. Electrophoretic deposition of MWCNT/HDI on the copper substrate was carried out using the deposition set up as shown in Fig. 3. Two par- allel copper plates (9 mm× 30 mm) separated by 10 mm gap were used as the electrodes. One of them works as depositing substrate (cathode) and other as the counter electrode. The suspension was ultrasonicated for about 20 min just before the EPD experiments. EPD was carried out at constant voltage mode at DC voltage between 10 and 30 V, using a source meter (Model: 2410, Keithley Instruments, Inc, USA) for deposition time of 0.5 – 5 min. Once deposition is over, the deposit was taken out carefully vertically along with the substrate. The sample was then allowed to dry upright position overnight at room temperature and weighed to determine the deposit yield and the products are ready for characterization. The electrochemical experiments were carried out using potentiostat (Model: Versastat-3, Prinston Applied Research, USA) with a three electrode electrochemical cell. The Cu-electrode embedded in the epoxy resin served as the working electrode, Pt as counter electrode and standard Ag/AgCl as reference electrode. The working electrode with exposed area 1 cm 2 was stabilized in 3.5% NaCl solution at room temperature (35 °C). The open circuit potential (OCP) was monitored continuously till the steady state was reached. The polarization plot was recorded at a scan rate of 1 mV/s within a scan range of +1 V to − 1 V. The corrosion potential (E corr ) and corrosion current density (I corr ) was computed by Tafel extrapolaration technique from polarization plot. The microstructural and morphological characterization of MWCNT and composite samples were carried out using Scanning Electron Microscope (Model: Hitachi, S-3400 N,Tokyo, Japan). The Raman scattering experiments were carried out using a Renishaw Im- aging Microscope WiRE spectroscopy (Model: Invia Re fl ex-H33197, Incoterm, UK) equipped with air cooled CCD detector. The spectra of powder samples of MWCNT were measured over a scanning range of 0 – 3250 cm − 1 with incident argon laser excitation wavelength of 514 nm. The speci fi c surface charge of MWCNT suspension measurements were carried out with Particle Charge Detector (PCD), Model: PCD-04-pH from Herrsching, Muteck, Germany. The anti-corrosion property of MWCNT reinforced polymer coating fi lms were investigated using potentiostat (Model: Versastat-3, Prinston Applied Research, USA). Fig. 4.(a, b and c) shows the optimization of concentration of dispersant GA, polymeric resin, HDI and combination thereof using Particle Charge Detector (PCD), the details of which described elsewhere [29,30]. The variation of PCD potential as function of different concentration is plotted and the in fl ection point in the graph gives the optimum concentration required for stable dispersion. The initial increase in PCD potential occurs due to increase in speci fi c charge due to adsorbed additives on MWCNT surface with increasing concentration of dispersant. Once the surface is covered completely (monolayer coverage), that quantity gives the overall maximum stability and optimized chemical additives dosages. The unadsorbed excess remains in the solution and may affect viscosity of the solution without affect- ing PCD potential. The measured optimum dosages of GA, HDI and GA and HDI combination were 600 mg/g (Fig. 4.a), 0.2 mg/g (Fig. 4.b) and 0.27 mg/g (Fig. 4.c), respectively. This technique is very easy, accurate and useful for the assessment of stability of nanoparticles suspensions and determination of optimum dispersant concentration for nano- ceramics and polyelectrolyte systems. [31 – 33]. The quantum of surface charge density on any particulate matter in aqueous suspension is an important particle characteristic and helpful for knowing dispersability of suspension. A very high surface charge density is an indicative of strong repulsive forces between the particles and results in good dispersion. Fig. 5 shows the results of surface charge measurement of pristine MWCNT, treated MWCNT with dispersant GA and MWCNT in presence of dispersant GA and polymeric resin HDI in aqueous suspension at ...
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... Sigma-Aldrich Chemie, GmbH, Stein- heim, Germany, with diameter range of 110-170 nm and average length 5-9 μm as reported by the supplier (Fig. 1). The Scanning elec- tron microscopy (SEM) image of pristine MWCNT showed large num- ber of cross-linking and entanglements. The entanglement could be broken to large extent by addition of dispersant. Fig. 2 shows well dis- persed MWCNT in presence of dispersant Gum Arabic (GA). GA used as dispersant is a highly branched polysaccharide and is known for its dispersion property. HDI is an organic polymeric resin generally used in special applications such as enamel coating which are resis- tant to abrasion and degradation from UV light. The ...
Context 4
... Arabic (GA). GA used as dispersant is a highly branched polysaccharide and is known for its dispersion property. HDI is an organic polymeric resin generally used in special applications such as enamel coating which are resis- tant to abrasion and degradation from UV light. The as received MWCNT was further characterized by the Raman spectroscopy (Fig. 2). The D-band (1353 cm − 1 ), G-band (1575 cm − 1 ) and D'-band, the second order overtone of D-band (2696 cm − 1 ), confirms the typical characteristics of multiwall carbon ...
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Citations
... Two peaks at 2714 cm −1 and 2952 cm −1 also appear which are represented by 2D and 2D′ respectively. These peaks depend upon the strain or stress applied to the nanotube by the surrounding material[38][39][40][41].3.5. Functional groups analysisFunctional groups of MgAl 2 O 4 and MgAl 2 O 4 /MWCNT nanocomposite are studied by FTIR spectroscopy (figure 5). ...
This work reports the synthesis and characterization of Magnesium Aluminate (MgAl2O4) and Magnesium Aluminate/Multi Walled Carbon Nanotube (MgAl2O4/MWCNT) nanocomposite by facile chemical co-precipitation method for the dye degradation application. MgAl2O4 and MgAl2O4/MWCNT nanocomposite are characterized by Scanning Electron Microscopy (SEM), x-ray Diffractometry (XRD), Raman Spectrometry, UV–vis Spectrophotometry (UV–vis), Fourier Transform Infrared Spectroscopy(FTIR), and x-ray Photoelectron Spectroscopy (XPS). Surface morphology of MgAl2O4/MWCNT nanocomposite exhibits entangled needle-like structures while MgAl2O4 spinel comprises agglomerated nanoparticles of different sizes. XRD confirms the formation of MgAl2O4. XPS identifies the chemical states and binding energies of constituent elements present in the sample. Optical properties reveal that addition of MWCNTs in MgAl2O4 decreases the optical bandgap energy from 3.02 eV to 2.78 eV. MgAl2O4/MWCNT nanocomposite shows reduced bandgap compared to pristine MgAl2O4 due to increased chemical defects or vacancies in intergranular regions and chemical interaction between MgAl2O4 and MWCNT, leading to the formation of new energy levels in MgAl2O4/MWCNT nanocomposite. Addition of MWCNTs provides a large surface area, more active sites, and enhances electron mobility between energy levels. MgAl2O4/MWCNT nanocomposite proves itself a better photocatalyst due to the fast degradation of Methyl Blue (MB) in 65 min as compared to MgAl2O4 which degrades the dye in 90 min. MgAl2O4/MWCNT nanocomposite also shows good stability and reusability even after performing the six cycles of dye degradation.
... The Raman fingerprints of PEDOT, CNTs and GRO have been previously investigated [55][56][57] . The vibrational modes of PEDOT are located at 1514 cm −1 , 1390 cm −1 , and 1272 cm −1 , and assigned to the Cα = Cβ asymmetrical, Cα = Cβ symmetrical stretching, and Cα -Cα inter-ring stretching vibrations, respectively, Supplement 3A. ...
Hydroquinone (HQ), catechol (CC) and nitrite (NT) are considered aquatic environmental pollutants. They are highly toxic, harm humans’ health, and damage the environment. Thus, in the present work we introduce a simple and efficient electrochemical sensor for determination of HQ, CC, and NT simultaneously in wastewater sample. The sensor is fabricated by modifying the surface of a glassy carbon electrode (GCE) by two successive thin films from poly(3,4-ethylenedioxythiophene) (PEDOT) and a mixture of carbon nanotubes-graphene oxide (CNT-GRO). Under optimized conditions the HQ, CC, and NT are successfully detected simultaneously in wastewater sample with changing their concentrations in the ranges (0.04 → 100 µM), (0.01 → 100 µM) and (0.05 → 120 µM), the detection limits are 8.5 nM, 3.8 nM and 6.1 nM, respectively. Good potential peak separations: 117 mV and 585 mV are obtained between the HQ-CC, and CC-NT. The sensor has an excellent catalytic capability toward the oxidation of HQ, CC, and NT due to good synergism between its composite components: PEDOT, GRO and CNTs. The features of the sensor are large active surface area, good electrical conductivity, perfect storage stability, good reproducibility, anti-interference capability and accepted recovery rate for HQ, CC, and NT determination in wastewater sample.
... It is known that Raman spectroscopy is a highly sensitive analyzing tool used to study the ordered/disordered crystal structure of carbon nano-materials [38]. ...
... It is evident that there are three distinct peaks appeared for all samples. The one with the signal detection at the wavelength ranges of 2600-2700 cm −1 can be attributed to the G′ peak, which is used to assure the typical characteristics of multiwall carbon nanotubes 63 . The other two absorption bands appearing at around 1345 cm −1 and 1586 cm −1 were identified as the D peak and G peak, respectively. ...
Biogas has been widely regarded as a promising source of renewable energy. Recently, the direct conversion of biogas over heterogeneous catalysts for the simultaneous production of syngas and carbon nanotubes exhibits a high potential for full utilization of biogas with great benefits. Involving the combined dry reforming of methane and catalytic decomposition of methane, the efficiency of process is strongly depended on the catalyst activity/stability, mainly caused by carbon deposition. In this study, Ni–Mo catalyst is engineered to provide a life-long performance and perform high activity in the combined process. The surface modification of catalysts by a controlled carburization pretreatment is proposed for the first time to produce a carbide catalyst along with improving the catalyst stability as well as the reactivity for direct conversion of biogas. The performance of as-prepared carbide catalysts is investigated with comparison to the oxide and metallic ones. As a result, the Ni–Mo2C catalyst exhibited superior activity and stability over its counterparts, even though the condensed nanocarbon was largely grown and covered on the surface. In addition, up to 82% of CH4 conversion and 93% of CO2 conversion could remain almost constant at 800 °C throughout the entire test period of 3 h under a high flowrate inlet stream of pure biogas at 48,000 cm³ g⁻¹ h⁻¹. The XPS spectra of catalysts confirmed that the presence of Mo2C species on the catalyst surface could promote the stability and reactivity of the catalyst, resulting in higher productivity of carbon nanotubes over a longer time.
... Two sharp peaks at 1350 and 1585 cm −1 were observed in both CNT/CNC and PANI@CNT/CNC SPME MNs (Figure 3), corresponding to the D-and G-bands of the CNTs, respectively. The D band is generally attributed to the disordered carbon structure of the CNTs, while the G band corresponds to its C-C bond stretching [25,26,28]. The Raman spectra for the PANI@CNT/CNC SPME MN exhibited a small, sharp peak around 1032 cm −1 (Figure 3), which was attributed to both the C-H bending of the benzenoid structure, and the C=N stretching in quinoid structure of PANI [29]. ...
A mechanically robust in-tube stainless steel microneedle solid phase microextraction (SPME) platform for dual electrochemical and chromatographic detection has been demonstrated. The SPME microneedle was fabricated by layer-by-layer (LbL) in-tube coating, consisting of carbon nanotube (CNT)/cellulose nanocrystal (CNC) film layered with an electrically conductive polyaniline (PANI) hydrogel layer (PANI@CNT/CNC SPME microneedle (MN)). The PANI@CNT/CNC SPME MN showed effective analysis of caffeine by GC-MS with an LOD of 26 mg/L and excellent precision across the dynamic range. Additionally, the PANI@CNT/CNC SPME MN demonstrated a 67% increase in sensitivity compared to a commercial SPME fiber, while being highly robust for repeated use without loss in performance. For electrochemical detection, the PANI@CNT/CNC SPME MN showed excellent performance for the detection of 3-caffeoylquinic acid (3-CQA). The dynamic range and limits of detection (LOD) for 3-CQA analysis were 75–448 mg/L and 11 mg/L, respectively. The PANI@CNT/CNC SPME MN was demonstrated to accurately determine the caffeine content and 3-CQA in tea samples and dark roast coffee, respectively. The PANI@CNT/CNC SPME MN was used for semiquantitative antioxidant determination and composition analysis in kiwi fruit using electrochemistry and SPME-coupled GC-MS, respectively.
... The growing request for the use of implants has led to the need for implant modification and improvement [1]. At the same time, magnesium (Mg) and its alloys have been considered for use in the field of biomaterials due to their biocompatibility and biodegradable properties [1][2][3]. Mg has a density close to that of bone and is absorbed by the body [3]. Mg is of interest for orthopedic applications due to its relatively low cost, high specific strength, and near-bone elastic modulus, which provides stress shielding and allows uniform distribution of tissue stress [4][5][6]. ...
... At the same time, magnesium (Mg) and its alloys have been considered for use in the field of biomaterials due to their biocompatibility and biodegradable properties [1][2][3]. Mg has a density close to that of bone and is absorbed by the body [3]. Mg is of interest for orthopedic applications due to its relatively low cost, high specific strength, and near-bone elastic modulus, which provides stress shielding and allows uniform distribution of tissue stress [4][5][6]. ...
... The Raman spectrum for MWCNTs (Figure 5d) shows the existence of D band (1353 cm −1 ), G band (1575 cm −1 ) and D' band, the second-order new D band (2696 cm −1 ), which is a distinctive feature. This confirms that CNTs are multi-walled [3]. ...
Magnesium (Mg) and its compounds have been investigated as biodegradable metals for bone implants. However, high corrosion rates and low bioactivity that cause loss of mechanical properties are factors that have limited their biomedical applications. The purpose of this work is to remedy the weaknesses of the Mg–Zn (MZ) alloy matrix. For this purpose, we have synthesized Mg-based composites with different concentrations of bredigite (Br; Ca7MgSi4O16)–carbon nanotubes (CNTs) using mechanical alloying and semi-powder metallurgy processes with spark plasma sintering. Then, we studied the effect of the simultaneous addition of Br-CNTs on in vitro degradation, as well as its effect on the composites’ mechanical and antibacterial properties. Increases of 57% and 72% respectively were observed in the microhardness and compressive strength of the MZ/Br-CNTs composite in comparison to the MZ alloy. In addition, the rate of degradation of Mg-based composites in simulated body fluids (SBF) was almost 2 times lower. An assessment of antibacterial behavior disclosed that the simultaneous adding of Br-CNTs to Mg can meaningfully prevent the growth and invasion of E. coli and S. aureus. These research findings demonstrate the potential application of MZ/Br-CNTs composites to implants and the treatment of bone infections.
... The peak at 2904 cm − 1 was much higher than the peak at 2605 cm − 1 , indicating that the strain or stress by PS occurred only on the flat sheet. The 2D peaks of graphene shifted to a higher wavenumber since CNT could be the hydrophobic interaction between graphene sheet and polymer, which caused higher energy demand for strain or stress to occur (Bagotia et al., 2019;Chipara et al., 2013;Singh et al., 2011). Figure S4 shows the FTIR spectra of PS-MWCNT-SiF and PS-G-SiF, where the spectrum of PS is given as reference. ...
Mechanically-robust nanocomposite membranes have been developed via crosslinking chemistry and electrospinning technique based on the rational selection of dispersed phase materials with high Young's modulus (i.e., graphene and multiwalled carbon nanotubes) and Cassie-Baxter design and used for oil and water separation. Proper selection of dispersed phase materials can enhance the stiffness of nanocomposite fiber membranes while their length has to be larger than their critical length. Chemical modification of the dispersed phase materials with fluorochemcials and their induced roughness were critical to achieve superhydrophobocity. Surface analytic tools including goniometer, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and scanning electron microscope (SEM) were applied to characterize the superhydrophobic nanocomposite membranes. An AFM-based nanoindentation technique was used to measure quantitativly the stiffness of the nanocomposite membranes for local region and whole composites, compared with the results by a tensile test technique. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques were used to confirm composition and formation of nanocomposite membranes. These membranes demonstrated excellent oil/water separation. This work has potential application in the field of water purification and remediation.
... Figure 3b shows the overlapped Raman spectra for the MN redox sensor during its stages of development. The CNT/CNC microneedle shows two distinct peaks at 1350 cm −1 and 1585 cm −1 (Figure 3b), which correspond to the D and G band of the CNTs, respectively [20][21][22][23]. The D band is attributed to disordered carbon structures, while the G band is due to the vibration of C-C bond stretching [20][21][22][23]. ...
... The CNT/CNC microneedle shows two distinct peaks at 1350 cm −1 and 1585 cm −1 (Figure 3b), which correspond to the D and G band of the CNTs, respectively [20][21][22][23]. The D band is attributed to disordered carbon structures, while the G band is due to the vibration of C-C bond stretching [20][21][22][23]. The PANI@CNT/CNC microneedle shows a peak at 1032 cm −1 (Figure 3b), ascribed to the C-H bending in benzenoid structure, and the C = N stretching in the quinoid structure of the PANI [24]. ...
This work presents a multipurpose and multilayered stainless steel microneedle sensor for the in situ redox potential monitoring in food and drink samples, termed MN redox sensor. The MN redox sensor was fabricated by layer-by-layer (LbL) approach. The in-tube multilayer coating comprised carbon nanotubes (CNTs)/cellulose nanocrystals (CNCs) as the first layer, polyaniline (PANI) as the second layer, and the ferrocyanide redox couple as the third layer. Using cyclic voltammetry (CV) as a transduction method, the MN redox sensor showed facile electron transfer for probing both electrical capacitance and redox potential, useful for both analyte specific and bulk quantification of redox species in various food and drink samples. The bulk redox species were quantified based on the anodic/cathodic redox peak shifts (Ea/Ec) on the voltammograms resulting from the presence of redox-active species. The MN redox sensor was applied to detect selected redox species including ascorbic acid, H2O2, and putrescine, with capacitive limits of detection (LOD) of 49.9, 17.8, and 263 ng/mL for each species, respectively. For the bulk determination of redox species, the MN redox sensor displayed LOD of 5.27 × 103, 55.4, and 25.8 ng/mL in ascorbic acid, H2O2, and putrescine equivalents, respectively. The sensor exhibited reproducibility of ~ 1.8% relative standard deviation (%RSD). The MN redox sensor was successfully employed for the detection of fish spoilage and antioxidant quantification in king mushroom and brewed coffee samples, thereby justifying its potential for food quality and food safety applications. Lastly, the portability, reusability, rapid sampling time, and capability of in situ analysis of food and drink samples makes it amenable for real-time sensing applications.
... Shen et al. [46] have argued that CNTs could be conductive additives due to their optimal electrical conductivity and characteristic length-to-diameter (aspect) ratio. Although, a variety of filler inhibitors have been studied as self-healing amendments to provide endurable mild steel protection [47][48][49][50][51][52][53], literature revealed that so far very few studies have exploited the green nanotechnology route to synthesize self-healing filler as protective coatings of mild steel against aggressive corrosion medium. The green nanotechnology enrouted production of metal nanoparticles is an emergent area with applications in physics, chemistry, biology, material science and medicine [54][55][56][57][58]. Presently, green nanotechnology is preferred to surmount the detrimental effects of heavy metals on human health and ecosystem. ...
This paper reports the self-healing properties of novel epoxy coating comprised of multi-walled carbon nanotubes (MWCNTs) as nanocontainers loaded with 5% green inhibitor-Elaeis guineensis/silver nanoparticles (EG/AgNPs) that acted as robust corrosion inhibitor for mild steel against adverse seawater environment. The self-healing assisted anti-corrosion effectiveness of the inventive coating for mild steel under seawater exposure for 42 days was evaluated via polarisation resistance, electrochemical impedance spectroscopy, adhesion strength and visual inspections. Further, the coated mild steel surface was characterised using X-ray diffraction, atomic force microscope and scanning electron microscopy analysis. The microstructures of smart powder (MWCNTs-EG/AgNPs) were also screened by a variety of microstructures techniques. Results revealed an excellent self-healing functionality of the produced smart epoxy coating with satisfactory anticorrosion behaviour against seawater exposure. A maximum of 97.87% inhibition efficiency and a minimum of 0.0009 mm/year corrosion rate were recorded after 42 days of exposure. Furthermore, this smart coating disclosed superior corrosion inhibition abilities even after 42 days of submersion in seawater by weakened the lepidocrocite (γ-FeOOH), as a result of the release of Elaeis guineensis /AgNPs, which in turn acted as efficient corrosion inhibitors to repair or self-heal the damaged coatings on mild steel surface.
... The Raman spectra of MWCNT and functionalized MWCNT depicted two bands, D band between 1348.8 to 1353.4 cm −1 corresponding to the sp 3 hybridized carbon, also known as disorder band and G band between 1582.3 to 1599.6 cm −1 corresponding to the sp 2 hybridized carbon (Inyang et al., 2014;Singh et al., 2011). However, the intensity ratio of the D band to the G band (I D /I G ) was enhanced from 1.006 to 1.014, due to the introduction of carboxylic functional groups on the defective sites of MWCNT, as shown in Figure S2. ...
Herein, Saccharum munja (SM) plant biomass and its novel composites with 0.5%, 1% and 2% functionalized carbon nanotube (CNT) were innovatively proposed as a versatile biosorbent for the removal of safranine O (SO) and methylene blue (MB) dyes from the single and binary systems. The morphology, structure and physicochemical properties of the as-fabricated adsorbents were characterized using various techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscope (FESEM) and Differential Scanning Calorimetry (DSC). Batch adsorption studies revealed maximum removal of dyes at neutral pH and equilibrium was reached within 10 min of contact time for both the dyes. The adsorption process was modelled by the pseudo-second-order kinetics and Langmuir isotherm, where the maximum adsorption capacity of the 1%CNT+SM composite was enhanced by 336.29% and 35.49% as compared to raw SM, in the case of SO and MB dye respectively. Interestingly, the raw SM and its composites showed a higher affinity in the binary system towards the removal of SO (82.56-95.67%) as compared to MB (80.67-94.24%) dye. Regeneration studies depicted excellent reusability even after the tenth sequential adsorption–desorption cycle, which makes these adsorbents a promising material for wastewater remediation.
