BITS Faculty Publications
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Item SrTiO3-TiO2 heterostructured nanotubes array for selective acetone sensing(IEEE, 2023) Hazra, ArnabEfficient detection of acetone is essential for medical applications. In this context, we are reporting acetone selective SrTiO 3 -TiO 2 sensor. Initially, TiO 2 nanotube array was synthesized by the electrochemical anodization and then treated with Sr(OH)2 solution through the hydrothermal reaction. The morphology and crystallinity of the SrTiO 3 -TiO 2 nanotubes were investigated. The Au/SrTiO 3 -TiO 2 /Ti sensor exhibited its natural selectivity towards acetone and showed a high response (99.5%/50 ppm) at 150°C under 80% relative humidity. The sensor exhibited a remarkable 51.2% response even for 0.5 ppm acetone. The stability and hydrophobicity of SrTiO 3 result in consistency during repeated cycle study of the sensor.Item Highly Reproducible and Reliable Methanol Sensor Based on Hydrothermally Grown TiO2 Nanoparticles(IEEE, 2023-10) Hazra, ArnabIn the present paper, TiO2 nanoparticles were synthesized through low cost hydrothermal method at 150°C. Structural, morphological and optical properties of the grown materials were characterized through X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Raman Spectroscopy, and Photoluminescence spectroscopy, respectively. X-ray diffraction confirms the anatase phase with average crystalline size of 6.8 nm. Non-uniform particles having numerous pores with large number of active sites offered superior capability to detect methanol even at lower concentrations. Band gap of the material were found to be 3.4 eV. TiO2 nanoparticles in planner structure were investigated towards methanol (1-100 ppm) at the temperature ranging from (25-150°C). Sensor was found to be maximum responsive with response magnitude of 85% at 100°C and 47% at room temperature towards 100 ppm of methanol. At 1 ppm of methanol, sensor response was found to be 20%. Sensor response towards methanol was correlated with the surface state of nanoparticles with HOMO-LUMO energy.Item SrTiO3 passivated MXene (Ti3C2Tx) for efficient VOC detection in hazardous humid ambient(Elsevier, 2024-02) Hazra, ArnabHumidity interference is a crucial consideration in gas sensing technology for real-time applications. MXenes are new-age two-dimensional (2D) materials with unique properties making them promising candidates for gas sensors. However, the MXene surface with the hydrophilic functional groups (e.g., =O, –OH) is susceptible to water vapor. The passivation by a hydrophobic layer on MXene could be the best option to overcome humidity intrusion. We are introducing super hydrophobic SrTiO3 passivation on the MXene layer for humidity-tolerant volatile organic compound (VOC) sensing. Herein, 2D MXene (Ti3C2Tx) was physically oxidized at 350 °C for 24 h to create a TiO2 layer and subsequent coating of moisture-blocking SrTiO3 (STO) overlayer was achieved by hydrothermal route. Sensors were tested in different VOCs and showed the optimum results towards the acetone. The TiO2 formation in MXene enhanced the acetone sensing response (217%/50 ppm) compared to the pure Ti3C2TX MXene sensor (175%/50 ppm) in air at 150 °C. However, the MX and TiO2/MX sensors were lacking in the acetone sensing performance in a humid atmosphere (80% RH). STO/MX-12 h sensor showed outstanding moisture-resistant sensing behavior in humid atmospheres (0–80% RH). Apart from this, the STO/MX-12 h sensor showed a high response of 68% for 100 ppb of acetone with adequate repeatability, and excellent stability in 80%RH and 150 °C operating temperature. The hydrophilicity change in MXene after SrTiO3 passivation was optimized by contact angle study.Item Studies on a resistive gas sensor based on sol–gel grown nanocrystalline p-TiO2 thin film for fast hydrogen detection(Elsevier, 2013-07) Hazra, ArnabA thin layer (~1 μm) of sol–gel grown nanocrystalline p-type TiO2 was deposited on a thermally oxidized p-Si (2–5 Ω cm resistivity and (1 0 0) orientation) substrate. The surface was characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), which also confirmed the nanocrystallinity of the material. Optical absorption spectroscopy was carried out to calculate the band gap of the material. Two lateral Pd contacts were used as the catalytic metal electrodes on TiO2 to fabricate the resistive gas sensor for hydrogen sensing. Detail gas response characteristics, selectivity and the stability of the sensor structure were studied. The sensors showed high response (~55%) to hydrogen with an appreciable short response time of 2 s at the optimized temperature, 175 °C and biasing voltage, 0.1 V in a steady dynamic atmosphere of 1% H2 with N2 as carrier gas. For practical applications, similar set of sensor experiments was also performed in air ambient. At 100 °C and 1.0 V bias the response magnitude was reduced to 49% but the response time came down to 1.3 s. The recovery time was lowest (~34 s) at 150 °C. The reduction in the recovery time in air is possibly due to quick removal of residual hydrogen from the surface of the sensor by interaction with oxygen present in air. The sensors showed selectivity to hydrogen and good stability. There was no degradation after working for 42 h in a discrete mode (6 h/day) in nitrogen and also in air. A possible gas sensing mechanism was suggested with a qualitative energy band diagram.