ABSTRACT
Layer structured vanadium pentoxide (V2O5) microparticles were synthesized hydrothermally and successfully decorated by a facile wet chemical route, with â¼10-20 nm sized ruthenium nanoparticles. Both V2O5 and ruthenium nanoparticle decorated V2O5 (1%Ru@V2O5) were investigated for their suitability as resistive gas sensors. It was found that the 1%Ru@V2O5 sample showed very high selectivity and sensitivity towards ammonia vapors. The sensitivity measurements were carried out at 30 °C (room temperature), 50 °C and 100 °C. The best results were obtained at room temperature for 1%Ru@V2O5. Remarkably as short a response time as 0.52 s @ 130 ppm and as low as 9.39 s @ 10 ppm recovery time at room temperature along with high selectivity towards many gases and vapors have been noted in the 10 to 130 ppm ammonia concentration range. Short response and recovery time, high reproducibility, selectivity and room temperature operation are the main attributes of the 1%Ru@V2O5 sensor. Higher sensitivity of 1%Ru@V2O5 compared to V2O5 has been explained and is due to dissociation of atmospheric water molecules on 1%Ru@V2O5 as compared to bare V2O5 which makes hydrogen atoms available on Brønsted sites for ammonia adsorption and sensing. The presence of ruthenium with a thin layer of oxide is clear from X-ray photoelectron spectroscopy and that of water molecules from Fourier transform infrared spectroscopy.
ABSTRACT
Visible light sensitive Fe(3+) and Ce(4+) co-doped nano TiO(2) photocatalyst has been prepared by a modified aqueous sol-gel method and the activity has been measured in terms of degradation of MB dye. Both dopants shifted the absorption profile of TiO(2) to the visible region and improved activity. Fe(3+) ions trapped the charge carriers due to the stable electronic configuration and improved their separation. Ce(4+) ions, which were mainly located at the grain boundaries, cause dislocations by bending the valence and conduction bands of TiO(2) and prevent the recombination of photoexcited electrons and holes. The co-doped TiO(2) compositions exhibited higher photocatalytic activity than that of pure titania and commercially available Degussa P25 under visible light by utilising the individual and synergistic contributions of Fe(3+) and Ce(4+) dopants, respectively.
ABSTRACT
Synthesis of bi-functional silica particles by a simple wet chemical method is described where the mixture of ultra fine nanoparticles (1-3 nm) of titania and silver were attached on the silica particle surface in a controlled way to form a core-shell structure. The silica surface showed efficient bi-functional activity of photo-catalytically self cleaning and antibacterial activity due to nanotitania and nanosilver mutually benefiting each other's function. The optimum silver concentration was found where extremely small silver nanoparticles are formed and the total composite particle remains white in color. This is an important property in view of certain applications such as antibacterial textiles where the original fabric color has to be retained even after applying the nanosilver on it. The particles were characterized at each step of the synthesis by X-ray photoelectron spectroscopy, UV-visible spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and electron energy loss spectroscopy. Bi-functional silica particles showed accelerated photocatalytic degradation of methylene blue as well as enhanced antibacterial property when tested as such particles and textiles coated with these bi-functional silica particles even at lower silver concentration.
