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Nanourchin VO2 nanostructures have been effectively synthesized by hydrothermal method. The synthesized hierarchical nanostructure has been characterized by various characterization techniques and electrochemical behaviour has been studied. X-ray diffraction analysis revealed the monoclinic phase and morphological analysis (FESEM) of VO2 showed nanourchin-like structure with arrangement of various nanorods in radial fashion. Over these nanorods, formation of secondary growth of asterisk-shape structure was observed. The width and length of nanorods were ~ 50 and ~ 75 nm, respectively. For the electrochemical measurements, 2032 type coin cells were fabricated using VO2 as electrode material. The electrochemical study of VO2 exhibited the pseudocapacitive behaviour with specific capacitance of 44 F g−1 in organic electrolyte with symmetric capacitor of two electrode system. The maximum energy density and power density were 44 and 8635 Wh kg−1, respectively. Cycling performance exhibited symmetric charge–discharge curves, and also specific capacitance was maintained up to 82% of initial value. [ABSTRACT FROM AUTHOR]

A simple chemical reduction method was employed to synthesize Cu–Ag and Ag-Cu core–shell nanostructures inside polyvinyl alcohol (PVA) matrix at room temperature. The core–shell nanostructures have been synthesized by varying the two different concentrations (i.e. 0.1 and 0.01 M) of the respective metal ions in equimolar ratios using successive reduction with hydrazine hydrate (HH) as a reducing agent. The core–shell nanostructures have been further characterized by different characterization techniques. The UV–visible spectroscopy exhibit the respective shift in the band positions suggesting the formation of core–shell nanostructures, which was further confirmed by field emission transmission electron microscopy–high-angle-annular dark field elemental mapping. The effect of metal ion concentration of the core–shell nanostructure on various Gram positive and Gram negative bacteria like Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and one fungal species Aspergillus fumigatus was observed by performing MIC and MBC/MFC study. Cu-Ag core–shell nanostructures were found to be effective antibacterial agent against all tested Gram-positive and Gram-negative bacteria, whereas Ag-Cu core–shell nanostructures were more efficient against a particular fungal species known as A. fumigatus. The highest value of MIC (75 µg ml−1) for Ag-Cu 0.1M core shell nanostructures (D1) was noted against S. aureus and E. coli whereas the lowest value (20 µg ml−1) was observed with P. aeruginosa. While in case of Cu-Ag 0.1M core shell nanostructures (E1) the highest value of MIC (100 µg ml−1) was noted against S. aureus and P. aeruginosa whereas the lowest value (15 µg ml−1) was observed with A. fumigatus. Also, field effect scanning electron microscope (FESEM) images of untreated and core–shell nanoparticles treated micro-organisms showed that 0.1 M Ag-Cu and 0.1 M Cu-Ag core–shell nanostructure can successfully break the cell wall of the fungi A. fumigatus and bacteria P. aeruginosa, respectively. Thus the present study concludes that, Cu-Ag & Ag-Cu core–shell nanostructures damage the cell structure of micro-organisms and inhibits their growth. Hence, the present Cu-Ag & Ag-Cu core–shell nanostructure acts as good antimicrobial agent against the bacteria and fungi, respectively. [ABSTRACT FROM AUTHOR]

SnO2@C nanocomposites were synthesized using a citrate gel method in one step. Carbon has been used to increase the conductivity of pristine SnO2. The SnO2@C nanocomposites show nanoparticles sized in the range of 30–50 nm. A structural study by XRD shows the tetragonal rutile structure of SnO2. Furthermore, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirm the existence of SnO2 along with carbon. The electrochemical performance was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge measurements. The nanocomposite has been used as an anode material for lithium-ion batteries. Pristine SnO2 exhibited a discharge capacity of 1854 mA h g−1 and a corresponding charge capacity of 1038 mA h g−1 for the first cycle. The SnO2@C nanocomposite showed a discharge capacity of 2574 mA h g−1 and charge capacity of 1481 mA h g−1 for the first cycle. These results clearly show the effect of carbon incorporation in SnO2. Furthermore, the nanocomposite shows a discharge capacity as high as 725 mA h g−1 after 200 cycles at a current density of 50 mA g−1. Thus, the obtained capacity for the nanocomposites is much higher as compared to that for pristine SnO2, i.e., 119 mA h g−1 at 50 mA g−1 after 200 cycles. The higher capacity in the nanocomposites is due to the fast transport of electrons and easy transport of lithium ions due to the carbon in the nanocomposites. The SnO2@C nanocomposite anode exhibits superior cycling stability and rate capability due to its stable electrode structure. [ABSTRACT FROM AUTHOR]

We report a relative humidity sensor based on manganese-nanoparticle-loaded mesoporous silica SBA-15 using a facile hydrothermal route. The as-developed nanocomposite material (Mn/SBA-15) possesses a high surface area and a high pore volume. The obtained samples were characterized by using low-angle X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N2 adsorption--desorption, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy techniques. The Mn/SBA-15 exhibited, improved humidity response and recovery time as compared to pure SBA-15 in the 11%-92% RH range. Optimal results were obtained for the 5 wt% Mn-loaded SBA-15 sample, which displayed excellent linearity, low hysteresis, and high humidity response. A change in ~5 orders of magnitude in resistance was observed over 11%-92% RH range. The investigation of humidity sensing properties of Mn/SBA-15 nanocomposite shows that this material has good prospects as humidity sensor. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sr0.2Ca0.8Fe2O4 with highest surface area is found to be the best catalyst. [•] Synergistic effect of Sr2+ and Ca2+ ions enhance the epoxidation of styrene. [•] The site preference energy of Sr2+ ion is greater than Fe3+ ion. [•] Important role of NaOH towards the enhancement of epoxide selectivity. [ABSTRACT FROM AUTHOR]

Abstract: Li doped and undoped γ-Fe2O3 nanopowders have been synthesized at room temperature via simple method by using ethylene diamine as a precipitating agent. The influence of Li doping on the humidity sensing behavior was investigated by varying the doping concentration of Li (0.15, 0.30, 0.45 and 0.75mol%). The results revealed that the Li doping was advantageous for tuning the response curves in the lower humidity region. The optimal content for Li doping was found to be 0.45mol% for which the sensor showed more linear behavior with its potential for device application in comparison with the other samples. [Copyright &y& Elsevier]

In this study, we report template and surfactant-free, low temperature (70°C) synthesis of needle-like α-FeOOH and its conversion at 400°C into α-Fe2 O3 nanorods using Fe(+2) and Fe(+3) chlorides and urea as a hydrolysis-controlling agent. The isolated needle-like α-FeOOH indicates asparagus-type growth pattern having length ca. 600 nm with 80 nm diameter at base and apex diameter of around 10 nm. The sample on heating (α-Fe2 O3) shows nanorod-like morphology. The samples were characterized using various physicochemical characterization techniques such as XRD, Raman spectroscopy, UV-Vis spectroscopy, particle size distribution analysis, Field Emission Scanning Electron Microscopy ( FE- SEM), and humidity sensing performance. The humidity sensing behavior of both α-FeOOH and α-Fe2 O3 was studied. The α-FeOOH shows quicker (10 s) and higher response toward change in humidity from 20% RH to 90% RH as compared with α-Fe2 O3 (60 s). Their typical morphology and crystalline structure plays an important role in humidity sensing behavior. [ABSTRACT FROM AUTHOR]

Nanourchin VO2 nanostructures have been effectively synthesized by hydrothermal method. The synthesized hierarchical nanostructure has been characterized by various characterization techniques and electrochemical behaviour has been studied. X-ray diffraction analysis revealed the monoclinic phase and morphological analysis (FESEM) of VO2 showed nanourchin-like structure with arrangement of various nanorods in radial fashion. Over these nanorods, formation of secondary growth of asterisk-shape structure was observed. The width and length of nanorods were ~ 50 and ~ 75 nm, respectively. For the electrochemical measurements, 2032 type coin cells were fabricated using VO2 as electrode material. The electrochemical study of VO2 exhibited the pseudocapacitive behaviour with specific capacitance of 44 F g−1 in organic electrolyte with symmetric capacitor of two electrode system. The maximum energy density and power density were 44 and 8635 Wh kg−1, respectively. Cycling performance exhibited symmetric charge–discharge curves, and also specific capacitance was maintained up to 82% of initial value. [ABSTRACT FROM AUTHOR]