S Chakraborty

Vanadium doped tin dioxide as a novel sulfur dioxide sensor

Considering the short-term exposure limit of SO2 to be 5 ppm, we first time report that semiconductor sensors based on vanadium doped SnO2 can be used for SO2 leak detection because of their good sensitivity towards SO2 at concentrations down to 5 ppm. Such sensors are quite selective in presence of other gases like carbon monoxide, methane and butane. The high sensitivity of vanadium doped tin dioxide towards SO2 may be understood by considering the oxidation of sulfur dioxide to sulfur trioxide on SnO2 surface through redox cycles of vanadium-sulfur-oxygen adsorbed species.

In vitro characterisation and microstructure of B2O3/P2O5 doped bioactive spodumene glass–ceramics

Abstract Glasses with compositions of (100−X−Y)Li2O.Al2O3.4SiO2+XB2O3+YP2O5 where X=0–2.5 and Y=0–10 (wt-%) were melted in a platinum crucible at 1500°C with air as the furnace atmosphere. The green compact pellets were prepared and fired at 500°C. The samples were sintered in air atmosphere at selected temperatures in the range of 750–900°C for up to 20 h. It has been found that the addition of B2O3 and P2O5 has a remarkable effect on the amount of β spodumene (β-S), relative to high quartz solid solution (h-QSS). The glass ceramics that contain appropriate amounts of B2O3 and P2O5 promise good sinterability at temperature as low as 850°C. There were two major types of phase transformation in the present investigation: crystallisation of the present glass to a metastable h-QSS and subsequent transformation from h-QSS to a stable β-S. In vitro test revealed that the spodumene glass ceramic is much more durable in human body fluid. It is further observed that the addition of B2O3 and P2O5 enhanced the chemical durability of glass ceramics.

Highly efficient novel carbon monoxide gas sensor based on bismuth ferrite nanoparticles for environmental monitoring

Creation of novel functionality in materials is always fascinating for researchers/scientists. Bismuth ferrite (BFO), a well known multiferroics material with simultaneous magnetic and electric order, is promising for spintronics and memory devices. Herein, we were able to demonstrate for the first time very good carbon monoxide (CO) sensing capability of bismuth ferrite (BFO) nanoparticles prepared through a simple sol–gel technique. Morphological/structural characterization was performed using various standard sophisticated modern probes, which confirms the formation of single phase BFO nanoparticles. The sensing properties of BFO nanoparticles towards CO was tested for concentrations in the range of 5 ppm–30 ppm at different temperatures (between 270 °C to 450 °C). Very good response (Rg/Ra) of around 2.12 towards 30 ppm CO at an operating temperature of 350 °C was observed. The as-prepared sensors exhibited rapid response and recovery time of around 25 s and 13 s, respectively, for sensing 30 ppm CO. In addition, the sensors are selective, highly reproducible and remain quite stable for almost 150 days, which is required for device application. A plausible mechanism has been proposed to explain the CO sensing behaviour of the BFO nanoparticles. On the basis of the observed sensing properties we believe that a BFO nanoparticle-based sensor could be a suitable alternative to conventional oxide-based sensors having various difficulties.