Department of Electrical and Electronics Engineering
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1925
Browse
6 results
Search Results
Item Fullerene (C60) functionalized TiO2 nanotubes for conductometric sensing of formaldehyde(Elsevier, 2022-08) Hazra, ArnabIn the current study, fullerene-C60, functionalized with various oxygen-containing groups, was decorated on a highly oriented electrochemically grown TiO2 nanotubes array for efficient detection of volatile organic compounds (VOCs) like formaldehyde. Concentrations of C60 were varied to prepare different wt% (0.006, 0.01, 0.02 and 0.05) of fullerene water colloidal systems, which were then used to prepare composite with TiO2 nanotubes by hydrothermal route. Detailed characterizations were performed to assess the morphology, structure and chemical compositions of the developed nanocomposites. BET analysis was performed to estimate the increased effective surface area due to the inculcation of the fullerene clusters of different sizes to the TiO2 nanotube surface. C60-TiO2 nanotubes composite showed natural selectivity towards formaldehyde. Ultra-high sensitivity (99.6%) by 0.05 wt% C60-TiO2 nanotube and very fast response/recovery (4 s/7 s) by 0.02 wt% C60-TiO2 nanotube were recorded towards 100 ppm of formaldehyde at 150 °C. The sensors covered the maximum detection range was 100 ppm to 100 ppb. However, highly promising VOCs detection was possible due to the enhanced surface area and high reactive surface provided by the C60-TiO2 nanotube composites.Item Fast Response (7.6s) Acetone Sensing by InGaN/GaN on Si (111) at 373 K(IEEE, 2017-03) Kumar, RahulA new and exciting resistive gas sensor based on Ni/InGaN/GaN heterostructure, grown by plasma-assisted molecular beam epitaxy, has been developed to efficiently detect acetone very rapidly at low temperature. Non-rectifying I-V characteristics of epitaxially relaxed InGaN with Ni contact have been revealed at 373 K. An incremental current of 11.74 μA has been found at 373 K with the exposure of 100 ppm of acetone vapor at an operating bias of 0.4 V. Sensitivity has been obtained from transient response curves. Most importantly, very fast response/recovery characteristics with good baseline recovery have been witnessed. The response time and recovery time have been found to be ~7.6-8.4 s and ~4.5-19.1 s. A possible explanation, including Langmuir adsorption-desorption isotherm, has also been discussed.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.Item Tailoring of the Gas Sensing Performance of TiO2 Nanotubes by 1-D Vertical Electron Transport Technique(IEEE, 2014-10) Hazra, ArnabAligned TiO 2 nanotubes (NTs), having diameter of 75 ± 10 nm and length of 280 ± 20 nm were synthesized by electrochemical anodization technique. Two types of device configurations, viz., planar/lateral and metal-insulator-metal (MIM)/vertical sensor structures were fabricated with TiO 2 NTs as the sensing layer. Vertical 1-D electron transport technique of MIM configurations was found to be very effective over the random (across the connected tubes) electron transport kinetics of planar devices, in determining the vapor (ethanol) sensor characteristics like response time and operating temperature. The optimum operating temperature of ethanol sensing was found to be much lower (75 °C) in case of MIM compared with its planar counterpart (150 °C). In addition, MIM configuration offered four and six times faster response and recovery times, respectively, compared with the planar ones toward 100-ppm ethanol at 75 °C. Sensing performance of the device configuration was correlated with the corresponding grain boundary model and carrier transport time with the help of 1-D electron transport path constituted of TiO 2 NT array.Item An efficient BTX sensor based on p-type nanoporous titania thin films(Elsevier, 2015-03) Hazra, ArnabSensing performance of sol–gel synthesised p-titania based sensors towards detection of low concentrations (⩽1 ppm) of benzene, toluene and xylene (BTX) at low temperature range (50°–175 °C) is presented in this article. The sensing layer was grown by dip coating method using oxidized silicon wafer as the substrate. X ray diffraction (XRD) analysis confirmed the growth of anatase phase of TiO2 with 〈1 0 1〉 preferential orientation. Nanoporous nature of the film was observed from Field Emission Scanning Electron Microscope (FESEM). Through Hall measurement, p-type conductivity of the TiO2 layer was authenticated. Sensing performance of the sensing layer to BTX was investigated in resistive mode with two lateral titanium electrodes. At low concentration range (0.1–1 ppm) of individual vapor of BTX, the sensing performance of the sensor was investigated found to be very promising. The results indicated that the optimum operating temperature for BTX sensing is moderately low (75 °C), with appreciably fast response and recovery time. At the lowest concentration (0.1 ppm) the corresponding response/recovery time was found to be ∼24 s/12 s, ∼14 s/20 s and ∼20 s/14 s for benzene, toluene and xylene respectively, at 75 °C. The influence of relative humidity (20% and 75%) on the sensing parameters of the developed sensor device has also been investigated. Possible sensing mechanism of detection of these aromatic hydrocarbons on p-type nanoporous titania surface is also discussed elaborately.Item Micro-cantilever Sensors for Efficient Gas Sensing(STM Journals, 2019) Hazra, ArnabMicro-cantilever has been progressively used for the development of miniaturized sensors for gas sensing, biochemical analysis, medical applications and quality and process control. Micro-cantilevers are fabricated with rectangular silicon slabs having thickness below 1 µm. For gas sensing applications, Si cantilever surface is modified with appropriate sensing materials for selective adsorption of gas/vapor or biomolecules. The bending of the cantilever due to different surface conditions is measured with laser beam deflection to get the sensitivity of the sensor. The current article discusses the background, principle of operation and bending characteristics of micro-cantilever gas sensors. Various applications and applicability of the micro/nano cantilever gas sensors have also been covered in the present report. Finally, the article has been concluded with future prospects of microcantilever gas sensors for multiple potential applications.