Girish M. Kale

Synthesis, characterisation and antibacterial activity of PVA/TEOS/Ag-Np hybrid thin films

Novel hybrid material thin films based on polyvinyl alcohol (PVA)/tetraethyl orthosilicate (TEOS) with embedded silver nanoparticles (AgNps) were synthesized using sol-gel method. Two different strategies for the synthesis of silver nanoparticles in PVA/TEOS matrix were applied based on reduction of the silver ions by thermal annealing of the films or by preliminary preparation of silver nanoparticles using PVA as a reducing agent. The successful incorporation of silver nanoparticles ranging from 5 to 7nm in PVA/TEOS matrix was confirmed by TEM and EDX analysis, UV-Vis spectroscopy and XRD analysis. The antibacterial activity of the synthesized hybrid materials against etalon strains of three different groups of bacteria -Staphylococcus aureus (gram-positive bacteria), Escherichia coli (gram-negative bacteria), Pseudomonas aeruginosa (non-ferment gram-negative bacteria) has been studied as they are commonly found in hospital environment. The hybrid materials showed a strong bactericidal effect against E. coli, S. aureus and P. aeruginosa and therefore have potential applications in biotechnology and biomedical science.

Electrochemical creatinine biosensors.

To measure creatinine, electrochemical techniques have been coupled with a range of biological recognition elements in a variety of sensor configurations. (To listen to a podcast about this feature, please go to the Analytical Chemistry website at pubs.acs.org/ac.

Investigation into an improved design of CO2 sensor

Abstract The open-circuit voltage (e.m.f.) of the solid-state potentiometric sensor for CO 2 , Pt, P co 2 (I)/Na 2 CO 3 //Nasicon(Na + )// P CO 2 (I)/Au-Pd, Pt has been measured at 650, 690 and 720 K as a function of the partial pressure of CO 2 between 150 and 10 000 ppm. Nasicon is used as a solid sodium ion conductor and pure Na 2 CO 3 is employed as an auxiliary electrode. The e.m.f. of the sensor is measured in dry and moist gas mixture containing water vapour at a partial pressure of 2.4 kPa. The measured e.m.f. of the sensor was found to be unaffected by the presence of water vapour in the gas mixture. The e.m.f. of the sensor was found to be Nernstian and was reproducible within ± 5 mV on cycling through the range of partial pressure of CO 2 employed in this study.

Novel Nanosized ITO Electrode for Mixed Potential Gas Sensor

The sensing properties of the planar scandia-stabilized zirconia based mixed potential gas sensor coupled with hydrothermally obtained nanosized ITO as an electrode material have been investigated. The planar sensor has shown good sensitivity to low-level of CO concentrations (16-500 ppm) in a lower oxygen ambient (4 vol %) in terms of the high magnitude of the signal and fast response (<5 s). The sensing properties of the planar sensor to CH 4 and other oxidizing gases such as O 2 and NO 2 have also been tested. The results indicate that the sensor could be used to potentially detect the reducing gases such as CO significantly rapidly compared to the oxidizing gases such as O 2 and NO 2 . A possible sensing mechanism of the planar sensor for rapidly detecting CO is also discussed.

Hydrothermal synthesis of titanium dioxide nanoparticles studied employing in situ energy dispersive X-ray diffraction

Hydrothermal synthesis of titanium dioxide (TiO2) nanoparticles has been studied in situ using synchrotron radiation energy dispersive X-ray diffraction (EDXRD). The nanoparticles were produced from an acid (HNO3) and an alkaline (tetrabutylammonium hydroxide; TBA) peptized gel by hydrothermal treatment at 210 °C and 270 °C. The in situ EDXRD spectra clearly showed that pure TiO2 rutile phase nanoparticles were crystallized from HNO3 peptized gel, whereas pure anatase phase nanoparticles were produced from the TBA peptized gel. The EDXRD data shows that the rate of the particle formation increases with an increase in the process temperature for both processes. The powder X-ray diffraction (XRD) and selected area electron diffraction (SAED) data confirms the in situ EDXRD results. The TEM images show that the anatase nanoparticles have relatively homogeneous particle size and morphology distribution whereas the rutile nanoparticles exhibit bimodal size and morphology distribution attributed to Ostwald ripening effect during the hydrothermal treatment.

Planar SOX sensor incorporating a bi-electrolyte couple

Abstract A solid-state electrochemical sensor for measuring SO X in a gas mixture has been designed by incorporating Na 3 Zr 2 Si 2 PO 12 (Nasicon) and (8 mol% Y 2 O 3 )-ZrO 2 (YSZ) as a solid electrolyte couple. The solid electrolyte couple consisted of 2-mm-thick sintered disk of Na 3 Zr 2 Si 2 PO 12 and a thin film of (8 mol% Y 2 O 3 ) ZrO 2 approximately 6 μm thick. YSZ thin film on Nasicon disk was prepared by multiple radio frequency (RF) magnetron sputtering technique. The sensor employs Na 2 SO 4 as an auxiliary or sensing electrode that is in contact with Nasicon. The SO 2 present in the gas mixture is converted to SO 3 by passing over heated Pt-catalyst. The sensor has been successfully tested in the laboratory environment. At a fixed concentration of 1000 ppm SO 2 , the electromotive force (emf) of the sensor was found to vary nonlinearly as a function of temperature between 823 and 1123 K. However, at a fixed temperature of 973 and 1023 K, the measured emf of the sensor was found to vary linearly as a function of the logarithm of concentration of SO X in the gas mixture between 100 and 3000 ppm. In the current sensor design, both electrodes are exposed to the same test gas eliminating the need for isolating the electrode compartments.

Maltose and pectin assisted sol–gel production of Ce0.8Gd0.2O1.9 solid electrolyte nanopowders for solid oxide fuel cells

A novel sol–gel method has been developed for the production of high purity nanopowders of cerium gadolinium oxide (CGO, Ce0.8Gd0.2O1.9) solid solution using maltose as an organic chelating agent and pectin for gelation. The results of this investigation indicate that the final particle size of approximately 10 nm can be obtained after calcination of the predried gel at 500 °C for 2 hours in ambient air. An insight into the calcination process has been obtained by using simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). Powder X-ray diffraction (XRD) confirms that all samples are single phase cubic CGO powders with no trace of impurity. The mean crystallite sizes calculated from XRD analysis using the Rietveld refinement method agree with the morphological features observed by transmission electron microscopy (TEM). The nanopowders produced in this study exhibit negligible strain as indicated by the Rietveld refinement procedure. The nominal composition of CGO has been found to be in excellent agreement with that determined by energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma-atomic emission spectrometry analysis (ICP-AES). The XRD and TEM analyses indicate that there is a significant influence of calcination temperature on the particle size which increases with increasing temperature for a fixed annealing time. This new sol–gel method is a cost effective, simple, environmentally friendly and non-toxic route for a large scale production of high purity single phase nanopowders of complex oxide functional ceramic materials at significantly low temperatures.

Formation of multifunctional nanocomposites with ultrathin layers of polyaniline (PANI) on silver vanadium oxide (SVO) nanospheres by in situ polymerization

We designed and successfully synthesized nanocomposites (NCs) of silver vanadium oxide nanospheres dispersed in different ultrathin layers of polyaniline (PANI–β-AgVO3) at different temperatures (60 and 80 °C) by in situ chemical oxidative polymerization for the first time. X-ray diffraction (XRD) shows a monoclinic crystallographic form of silver vanadium oxide (SVO) to be dispersed in ultrathin layers of PANI. Morphological studies were performed by field emission electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). The NCs synthesized at temperatures of 60 and 80 °C show approximately 4 and 2 nm ultrathin layers of PANI grown on SVO nanospheres, respectively. The sizes of the SVO nanospheres dispersed in the ultrathin PANI layers are in the range of 10–40 nm. Fourier transformed infrared (FTIR) spectroscopic and energy dispersive X-ray (EDAX) spectroscopic investigations indicate the existence of SVO in the PANI layer. The NCs are further characterized by ultra violet-visible (UV-vis) spectroscopy. The electrochemical study of (PANI–β-AgVO3) shows an enhancement in the capacitance (365.6 F g−1) compared to V2O5·nH2O–PANI NCs (217.5 F g−1) and PANI (33 F g−1). The SVO dispersed in a layer of PANI NC exhibits excellent humidity sensing characteristics. The response and recovery times are found to be 4 and 8 seconds, respectively. The NCs have good potential as supercapacitors as well as in fast responsive humidity sensors. Layers of PANI on SVO are for the first time studied and correlated by XRD, Raman spectroscopy, AFM and HRTEM studies.

Synthesis and characterizations of nanosized tin-doped indium oxide by different soft-chemical routes

Abstract Nanosized tin-doped indium oxide (ITO) with different phase formation and morphologies has been successfully synthesized by two different chemical methods: combustion synthesis from the aqueous tin and indium nitrate solution containing urea as the fuel and hydrothermal treatment of the solution with the urea as the mineralizer. The sub-micrometer ITO nanoclusters with stratified morphology were obtained by calcining the obtained precursor from combustion process at 600°C for one hour. However, by utilizing urea as the mineralizer during hydrothermal treatment, the obtained ITO powders exhibit a composite consisting of spheres and rods after calcining at 600°C for one hour. Both of the processing routes yield a two-phase mixture consisting of rhombohedral and cubic forms of ITO. Supported by ORS scholarship and Institute for Materials Research in Leeds University

Oxygen Potential in Molten Tin and Gibbs Energy of Formation of SnO 2 Employing an Oxygen Sensor

On-line monitoring of the dissolved impurities in molten metals is important for better process control during alloying and metal refining operations. Disposable-type oxygen sensors are commercially available and are used in the iron and steel industry worldwide. However, there is a need for developing low-cost, reliable, long-life oxygen sensors for continuous monitoring of dissolved oxygen in molten metals. In this paper we present the results of the physical and electrical characterization of the solid electrolyte material ZrO 2 (8 mol%Y 2 O 3 ). The experimental results of the application of long-life solid-state electrochemical sensors designed using yttria-stabilized zirconia solid electrolyte for the measurement of oxygen potential in molten tin between 823 to 1273 K and standard Gibbs energy of formation of SnO 2 from its elements are also reported.