A. Nirmala Grace

Electrocatalytic oxidation of formic acid and formaldehyde on nanoparticle decorated single walled carbon nanotubes

A potent catalyst has been prepared consisting of platinum (Pt), and platinum-palladium (Pt-Pd) nanoparticles supported on purified single-walled carbon nanotubes (Pt/CNT and Pt-Pd/CNT). Electrochemical characteristics of formic acid and formaldehyde oxidation on these catalysts are investigated via cyclic voltammetric analysis in mixed 0.5 M HCOOH (or 0.5 M HCHO) and 0.5 M H(2)SO(4) solutions. The results imply that the Pt-Pd/CNT electrodes exhibit a better activity than the corresponding Pt nanoparticles modified SWCNT electrodes. The modified electrode exhibits significant electrocatalytic activity towards formic acid and formaldehyde oxidation, which may be attributed due to the uniform dispersion of nanoparticles on SWCNTs and the efficacy of Pd species in Pt-Pd system. Such nanoparticles modified CNT electrodes exhibit better catalytic behavior towards formic acid and formaldehyde than the corresponding carbon electrodes, indicating that the system studied in the present work is the more promising system for use in fuel cells.

Fabrication of CeO2/Fe2O3 composite nanospindles for enhanced visible light driven photocatalysts and supercapacitor electrodes

Hybrid CeO2/Fe2O3 composite nanospindles (CNSs) are synthesized by a simple and cost effective co-precipitation method. CeO2/Fe2O3 CNSs used as an efficient recyclable photocatalyst for degrading Eosin Yellow (EY) dye under visible light irradiation possess a high degradation rate of 98% after 25 min. The estimated electrical energy efficiency of CeO2/Fe2O3 CNSs shows the consumption of less energy (6.588 kW h m−3 per order) in degrading EY. Besides, the CeO2/Fe2O3 CNS exhibits a specific capacitance of 142.6 F g−1 at a scan rate of 5 mV s−1. Moreover, the composite displays an excellent capacitance retention of 94.8% after 1000 cycles. This newly designed CeO2/Fe2O3 CNS with enhanced visible light-driven photocatalytic activity and good supercapacitive cycling stability has great potential for use in wastewater treatment and energy storage applications.

Development of hexa (aminophenyl)cyclotriphosphazene-modified cyanate ester composites for high-temperature applications

The organic–inorganic hybrid of hexa(aminophenyl)cyclotriphosphazene (CPA) was synthesized by reacting hexachlorocyclotriphosphazene with 4-acetamidophenol followed by hydrolysis. The resulting product CPA was then allowed to react with 2,2-bis(4-cyanatophenyl)propane (cyanate ester) in different ratios (5, 10, and 15%) to form six-membered oxygen-linked triazine ring with formation of highly cross-linked network structure. Thermal curing behavior was confirmed using Fourier transform infrared spectroscopy analysis and thermal properties were studied using thermogravimetric analysis and differential scanning calorimetry analyses. Dielectric constant and dielectric loss were measured using impedance analyzer. Data resulted from different studies indicate that these hybrid composites can be used for high-performance thermal applications in the place of conventional cyanate esters for better performance.

Fabrication and characterization of Ag doped hydroxyapatite-polyvinyl alcohol composite nanofibers and its in vitro biological evaluations for bone tissue engineering applications

Electrospinning is one of the promising techniques to fabricate the nanofiber based scaffold for bone regeneration applications. In this study, firstly sol–gel method was employed to synthesize 5 % of Ag doped hydroxyapatite and also 10 wt% of polyvinyl alcohol solution was prepared for the electrospun process. For the first time, we have successfully fabricated the composite nanofibers in the combination of various concentration of Ag doped hydroxyapatite such as 1, 2, 3, and 5 wt% with polyvinyl alcohol solution. The developed Ag doped hydroxyapatite-polyvinyl alcohol composites were further characterized by Fourier transform infrared spectroscopy and powder-X-ray diffraction analysis to examine the characteristic functional groups and phase composition of Ag doped hydroxyapatite embedded into polyvinyl alcohol matrix. The uniform distribution of Ag doped hydroxyapatite in polyvinyl alcohol polymer with nanofiber diameter of 188–242 nm range was confirmed by high resolution transmission electron microscope and dynamic light scattering analysis, also the chemical/elemental composition was observed by scanning electron microscopy-energy dispersive spectroscopy analysis. The antibacterial activity was evaluated for the fabricated Ag doped hydroxyapatite polyvinyl alcohol composite nanofibers by using Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) pathogens and the results demonstrated that E. coli exhibits excellent zone of inhibition than S. aureus due to its lesser cell wall thickness. The hemocompatibility study proves that the developed composite nanofibers are blood compatible and showed the hemolytic ratio of less than 5 %. In addition to this, in vitro bioactivity assessment was carried out for 7 days by immersing in simulated body fluid solution to generate the dense apatite layer on their surfaces which was further examined by X-ray diffraction and scanning electron microscopy-energy dispersive spectroscopy analysis. Hence, these electrospun fabricated Ag doped hydroxyapatite-polyvinyl alcohol composite nanofibers will acts as a potential scaffold material for tissue engineering applications.Graphical AbstractGraphical abstract of electrospun fabrication of Ag@HAP-PVA composite nanofibers and its in vitro biological evaluations.

Hydrothermal Synthesis of CuS Nanostructures with Different Morphology

Cus Nanostructures Have Been Successfully Prepared from Copper Chloride with Two Different Sulfur Sources Like Thiourea and Sodium Thiosulphate by Hydrothermal Route at 150oC. The Growth of Cus Nanostructures Were Investigated for Different Reaction Time Periods of 5 Hrs and 24 Hrs Respectively Using Water as Solvent. the as-Synthesized Cus Nanostructures Are Characterized by X-Ray Diffraction (XRD) and Field-Emission Scanning Electron Microscopy (FE-SEM). XRD Pattern Indicates that the Prepared Cus Nanomaterials Are in Pure Hexagonal Phase. Results Show that Cus Nanomaterials with Different Hierarchical Structures Like Urchins, Nanoplates Etc,. Were Obtained at Different Experimental Conditions. A Systematic Investigation of the Final End Products Has Been Done to Elucidate the Formation Mechanism at Different Experimental Parameters. The Optical Properties of the Cus Structures Were Studied by UV-Vis Absorption Analysis, which Showed Broad Absorption in the Visible Region. The Optical Band Gap of the Cus Nanomaterials Were Found as 2.2 Ev and 2.18 Ev for Different Sulfur Sources.

Microwave assisted synthesis of copper oxide and its application in electrochemical sensing

Copper oxide nanopowders were prepared using copper acetate as the precursor and polyethylene glycol (PEG) as stabilizer in ethanol medium. The mixture containing copper acetate, sodium hydroxide and PEG was irradiated with microwave and nanometric copper oxide particles were formed within 8 min. The prepared nanoparticles were characterized using x-ray diffraction, UV-vis spectroscopy and scanning electron microscopy. The average particle size was found to be ~ 4 nm. This was used to modify glassy carbon electrode with PVDF & DMF as binder and used for sensing of carbohydrates (glucose and sucrose) and H2O2. The copper oxide nanoparticles showed excellent sensitivity in the range of 0.1 mM to 1 mM when choronoamperometry was carried out at 0.6 V Vs. Ag/AgCl. The observed sensitivity is much higher when compared with conventional micron sized copper oxide particles.

Synthesis and characterisation of CuS nanomaterials using hydrothermal route

Copper sulphide (CuS) nanomaterials with interesting morphology were synthesised using copper nitrate trihydrate, thiourea and water as a solvent by a simple hydrothermal route. A systematic investigation was carried out to investigate the effect of reaction time (5, 16 and 24 h) at 150°C on the morphology of the materials. Without the use of any template or additives, shape controlled synthesis of CuS nanocrystallites were achieved. The possible mechanism for the formation of the various nanostructures of CuS in this system is discussed. The prepared materials were characterised by X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and DRS-UV–Vis absorption analysis. The UV–Vis spectrum shows that it is the promising material which can absorb in the visible region and hence could be used for photocatalytic applications. In addition, the electrochemical characteristic of the synthesised material was investigated by cyclic voltammetric analysis, which shows that CuS could be used for electrocatalytic applications.

Growth of Carbon Nanotubes Using MgO Supported Mo-Co Catalysts by Thermal Chemical Vapor Deposition Technique

A simple method is developed for the synthesis of carbon nanotubes (CNTs) using Mo-Co/MgO catalyst by a thermal chemical vapor deposition (CVD) technique. Acetylene was used as the source of carbon and nitrogen as carrier gas. A series of MgO supported Mo-Co catalysts were prepared by the combustion route using urea as the fuel at different stoichiometric ratios. It was found that a higher yield of carbon nanotubes was obtained by the developed catalysts. Also, the addition of molybdenum to Co/MgO catalysts could remarkably increase the yield and also improve the quality of CNTs from thermal CVD with acetylene as precursor gas. The morphology of the catalysts and CNTs obtained was studied by field emission scanning electron microscope (FE-SEM). Other techniques like Raman spectroscopy and XRD were also employed to know the physico-chemical properties of the samples.