Browsing by Author "Hazra, Arnab"

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1-D TiO2 Nanorods Array-Based Parallel Electrode Sensor for Selective and Stable Detection of Organic Vapors
(IEEE, 2020-01) Hazra, Arnab; Gangopadhyay, Subhashis
A solid-state vapor sensor in parallel electrode configuration was fabricated by employing 1-D TiO 2 nanorods as a sensing layer. Highly ordered and oriented TiO 2 nanorods were synthesized on a Ti substrate by using hydrothermal method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to characterize the TiO 2 nanorods/Ti samples. The developed Au/TiO 2 nanorods/Ti type parallel electrodes sensor demonstrated the potential of integrated operations of both resistive and capacitive changes towards various concentrations (50-300 ppm) of volatile organic compounds (VOCs) like methanol, ethanol, 2-propanol, acetone and benzene at 50 °C. The resistive response magnitude of the sensor was found to be increased from 13 % to 87% while the capacitive response magnitude of the sensor was increased from 32 % to 200%, as methanol concentration was increased from 50 ppm to 300 ppm. However, the use of both modes enhances the selectivity performance of the sensor as the resistive mode exhibited better selectivity for a lower concentration of VOCs and the capacitive mode for higher concentration of VOCs. Moreover, the sensor showed a very good stability because of low operating temperature (50°C) as well as rutile (major) phase of TiO 2 nanorods.
Amplified Methanol Sensitivity in Reduced Graphene Oxide FET Using Appropriate Gate Electrostatic
(IEEE, 2020-10) Hazra, Arnab
The current study concerns a technique to amplify the gas sensitivity of reduced graphene oxide (rGO)-field-effect transistor (FET) sensor for the detection of very low concentration gaseous species. rGO channel exhibits tunable carrier density with ambipolar transport in FET structure by the change of electrostatic potential through the gate terminal. At low carrier density of channel, the exchange of carriers due to surface adsorption and desorption is significant that eventually enhances the sensitivity of the rGO-FET sensor at a typical gate voltage (VGS). The back-gated rGO-FET sensor was fabricated on p-Si substrate with 90-nm-thick SiO2 layer. The defects, disorders, and morphology of single-layer (major) rGO were characterized with the spectroscopic and microscopic study. The modulation of ambient sensitivity of rGO film was tested in the exposure of different ambient like dry air, argon, oxygen, and a test vapor methanol. 1.95% methanol (at 150 ppm) sensitivity at VGS = 0 V was amplified up to 127.93% at VGS = 5 V and 82.38% at VGS = 13 V where the temperature and drain-to-source voltage (VDS) were 100 °C and 1.4 mV, respectively.
ANN based approach for selective detection of breath acetone by using hybrid GO-FET sensor array
(IOP, 2022-04) Ajmera, Pawan K.; Hazra, Arnab
This research used hybrid graphene oxide (GO) field effect transistors (FETs) based sensor array to design an electronic nose (e-nose) for identifying exhaled breath acetone to diagnose diabetes mellitus through noninvasive route. Six back gated FET sensors were fabricated with hybrid channel of GO, WO3 and noble metals (Au, Pd and Pt) nanoparticles. The experiment was carried out by using four distinct forms of synthetic breath, each with a different level of interference. Linear discriminant analysis (LDA) and artificial neural networks (ANN) were utilized to classify and analyze the sensor response vector. In contrast, partial least square (PLS) and multiple linear regression (MLR) were used to evaluate the exact acetone concentration in synthetic breath. First, LDA was used to lower the dimensionality of the response vector, which was then provided as an input to the ANN model. ANN was performed with ten perceptrons model in the hidden layer and highest accuracy of 99.1% was achieved. Additionally, by using the loading plot of PLS, three sensors (Pt/WO3/GO, Pd/WO3/GO, and WO3/GO) had the ample use to predict the concentration of breath acetone. Moreover, the MLR approach with correlation coefficient (R2) of 0.9572 and root mean square error (RMSE) of 5.63% were used for obtaining the exact concentration of acetone. Consequently, e-nose with matrix of hybrid GO-FET sensors and pattern recognition algorithms (LDA, ANN, PLS and MLR) exhibited considerable ability in selective detection of acetone in synthetic breath.
Anodically grown nanocrystalline titania thin film for hydrogen gas sensors – a comparative study of planar and MAIM configuration
(Elsevier, 2013-11) Hazra, Arnab
Nanocrystalline titanium dioxide (TiO2) thin film was grown by UV assisted anodization of 0.25 mm thick titanium foil (99.7% pure). Room temperature electrochemical oxidation and photo etching were carried out in 0.1 M dilute H2SO4 electrolyte and at 10 V potentiostatic bias without and with 400 W UV light illumination respectively. While 2D-XRD confirmed the anatase crystalline feature AFM study revealed a rough morphology. A band gap of 3.35 eV was determined by optical study. Palladium (Pd) contacts were deposited laterally on the oxide surface as catalytic metal electrodes to fabricate a planar sensor configuration and a vertical metal-active insulator-metal (MAIM) structure was configured using palladium and titanium-silver alloy as top and bottom electrode respectively. The hydrogen sensor study was carried out at different temperatures (100–175 °C) and with different gas concentrations (0.1–1%) for both planar and MAIM structures in nitrogen as well as in air. A detailed hydrogen gas response characteristic was studied for these two types of sensor structures. Both the sensor structures were found suitable to sense 1% hydrogen in nitrogen ambient and at the optimum temperature of 150 °C with a pretty fast response time of 1.1 s for planar sensor and 1.4 s for MAIM sensor. However, the corresponding recovery time of 102.5 s and 92.3 s were quite long. The subsequent studies in air in the identical conditions recorded the response time and recovery time of 0.49 s and 28.8 s for planar and 1.5 s and 44.6 s for MAIM configurations respectively. The selectivity and the long term stability were investigated. A comparative sensor study with the two devices was performed and the results have been explained.
Au/TiO2 Nanotubes/Ti-Based Solid-State Vapor Sensor: Efficient Sensing in Resistive and Capacitive Modes
(IEEE, 2018-05) Hazra, Arnab; Gangopadhyay, Subhashis
Fabrication of TiO 2 nanotubes-based solid-state vapor sensor (Au/TiO 2 nanotubes/Ti) and its performance analysis for both resistive- and capacitive-mode sensing mechanisms are discussed here. Highly ordered TiO 2 nanotubes array has been synthesized by the electrochemical anodization technique. Structure and morphology of the as-grown TiO 2 nanotubes have been characterized using X-ray diffraction and field-emission scanning electron microscopy. X-ray photoelectron spectroscopy has been used to study the chemical states of the TiO 2 nanotubes. The sensor device has successfully been tested for ethanol vapor. The effect of temperature, pressure, and reducing ambient (i.e., partial pressure of ethanol vapor) has been studied using the impedance analysis method. The resistive and capacitive components of the impedance were measured individually. The sensor resistance decreased by 93.38%, whereas the capacitance increased by 28789.95% after an exposure to 1000 ppm of ethanol. Both the resistive and capacitive sensing performance of Au/TiO 2 nanotubes/Ti device have been correlated with the proposed circuit model to achieve an improvised vapor sensing.
Bimetals (Au-Pd, Au-Pt) loaded WO3 hybridized graphene oxide FET sensors for selective detection of acetone
(IEEE, 2022) Hazra, Arnab
Efficient detection of acetone is important for a variety of applications in pharmaceutical, automotive industries, medical diagnosis etc. Surface modification is one of the potential method to enhance the sensitivity as well as selectivity of any sensors. In recent days, surface functionalization with bimetallic nanoparticles become attractive because of its enhanced catalytic properties and the possibility to form discrete heterojunctions. In this study, WO 3 flowered morphology was prepared by one step acid precipitation method and bimetallic nanoparticles of Au-Pd and Au-Pt were deposited on WO 3 /GO hybrid layer by one-step dip-coating process and fabricated a back gated field effect transistor (FET) structured sensor. Various morphological and structural characterizations were performed to study the various properties of the hybrid sensing layer. I D -V GS characteristics and the acetone sensing performance were measured for both the sensors i.e., Au-Pd/WO 3 /GO and Au-Pt/WO 3 /GO at room temperature. Among the two sensors, Au-Pt/WO 3 /GO FET sensor exhibited an appreciably high sensitivity of 56% towards 80 ppm acetone at room temperature under applied gate voltage (V GS ) of 1.2V. The lower detection limit of the Au-Pt/WO 3 /GO FET sensor was 400 ppb of acetone where it showed a 3 % response. The sensing mechanism envisages that the bimetallic loading in the ternary form of the nanocomposite enhanced sensitivity significantly by the spill-over effect. Also, the application of an optimized gate voltage amplified the sensitivity of the FET structured sensors.
A Bumpy Ride of Mycobacterial Phagosome Maturation: Roleplay of Coronin1 Through Cofilin1 and cAMP
(Frontiers, 2021-09) Hazra, Arnab
Phagosome-lysosome fusion in innate immune cells like macrophages and neutrophils marshal an essential role in eliminating intracellular microorganisms. In microbe-challenged macrophages, phagosome-lysosome fusion occurs 4 to 6 h after the phagocytic uptake of the microbe. However, live pathogenic mycobacteria hinder the transfer of phagosomes to lysosomes, up to 20 h post-phagocytic uptake. This period is required to evade pro-inflammatory response and upregulate the acid-stress tolerant proteins. The exact sequence of events through which mycobacteria retards phagolysosome formation remains an enigma. The macrophage coat protein Coronin1(Cor1) is recruited and retained by mycobacteria on the phagosome membrane to retard its maturation by hindering the access of phagosome maturation factors. Mycobacteria-infected macrophages exhibit an increased cAMP level, and based on receptor stimulus, Cor1 expressing cells show a higher level of cAMP than non-Cor1 expressing cells. Here we have shown that infection of bone marrow-derived macrophages with H37Rv causes a Cor1 dependent rise of intracellular cAMP levels at the vicinity of the phagosomes. This increased cAMP fuels cytoskeletal protein Cofilin1 to depolymerize F-actin around the mycobacteria-containing phagosome. Owing to reduced F-actin levels, the movement of the phagosome toward the lysosomes is hindered, thus contributing to the retarded phagosome maturation process. Additionally, Cor1 mediated upregulation of Cofilin1 also contributes to the prevention of phagosomal acidification, which further aids in the retardation of phagosome maturation. Overall, our study provides first-hand information on Cor1 mediated retardation of phagosome maturation, which can be utilized in developing novel peptidomimetics as part of host-directed therapeutics against tuberculosis.
C60-encapsulated TiO2 nanoparticles for selective and ultrahigh sensitive detection of formaldehyde
(IOP, 2021-09) Hazra, Arnab
The current study concerns development of fullerene-C60-encapsulated TiO2 nanoparticles hybrid for an efficient detection of volatile organic compounds (VOCs). The nanocomposite was synthesized via chemical route by using hydrated fullerene-C60 and sol-gel derived undoped p-type TiO2 nanoparticles. The nanocomposite was characterized morphologically and structurally comparing with pure C60 clusters and pure TiO2 nanoparticles as the reference materials. The average diameter of the C60-encapsulated TiO2 nanoparticles was 150 nm whereas the average diameters of C60 clusters and pure TiO2 nanoparticles were 161 nm and 18 nm respectively. Therefore, all the materials were implemented in interdigitated electrode based planner structured sensors and tested towards multiple VOCs. However, C60–TiO2 composite exhibited its natural selectivity towards formaldehyde with a very high sensitivity for the concentration range of 1–1000 ppm. C60-encapsulated TiO2 nanoparticles depicted more than double response magnitude (117%) than the pure TiO2 nanoparticle (48%) and pure C60 particles (40%) and appreciably fast response/recovery (12 s/331 s) towards 100 ppm of formaldehyde at 150 °C. However, the efficient VOC sensing was achieved in C60-encapsulated TiO2 sensors possibly due to the extreme reactive surface provided by the oxygen functionalized C60 and easy electronic exchange between ambient and the TiO2 nanoparticles through C60 layers. The combined properties of both C60 and TiO2 lead to the formation of a promising nanocomposite which provided better sensing characteristics than that of the pure materials.
Capacitive gas and vapor sensors using nanomaterials
(Springer, 2018-01) Hazra, Arnab
An immense number of sensors has been reported in the literature employing various methods for the detection of different gases and vapors. This article summarizes those sensors whose sensing layer is made up of nanostructured materials and a change in capacitance value of device is the key parameter for detecting a gas or vapor. Now-a-days, capacitive sensors are emerging as they consume less power, operate well at room temperature and show decent response and recovery time. The sensing principles, configurations, mechanisms and performances of capacitive sensors based on different nanostructures are summarized and discussed in the current article. Emerging carbon based nanomaterials like carbon nanotube and graphene are also highlighted for capacitive mode detection of gases and vapors. Finally, an outlook of primary challenges in this field are identified and discussed at the end of the review.
Carbon Nanomaterial Electronics: Devices and Applications
(Springer, 2021) Hazra, Arnab
Presents novel research work written by expert professionals. Covers diverse aspects of carbon nanomaterial research. Includes specific chapters on graphene, carbon nanotubes, and carbon composites
Carbon-metal oxide nanocomposites for selective detection of toxic and hazardous volatile organic compounds (VOC) – A review
(Elsevier, 2022-04) Hazra, Arnab
Recently carbon nanostructures i.e. graphene and its derivatives, carbon nanotubes (CNT) and fullerene combined with different metal oxides have provided researchers a lot of opportunities for the sensing of volatile organic compounds (VOCs). The synergistic effect of both nanocarbon and metal oxide assuredly makes the nanocomposite suitable for reliable and stable sensors. Studies on hybrid structures by many researchers had shown improved sensing parameters in terms of high sensitivity, selectivity, fast response and recovery time at room temperature. In the present review we have reported the nanocomposites of carbon nanostructures and metal oxides for efficient and selective detection of toxic and hazardous VOCs.
CO Gas-Sensing at Low Temperature using CuO Thin Films
(IEEE, 2019) Hazra, Arnab
Carbon monoxide (CO) is known as a silent killer, as breathing in CO gas ambient for long periods with a concentration above the tolerance limit can cause severe health hazards and even death. CO concentration as low as 30 ppm (parts per million) inhaling for few hours can significantly affects the human health. This work focuses on CO gas sensing behaviors of cupric oxide (CuO) nanostructures at relatively lower operating temperature (150°C). The sensors show significant sensitivity for 25 ppm CO gas with fast response and recovery times as well as good reproducibility. Firstly, thin copper films are vacuum deposited on glass substrates at room temperature. Afterwards, these films are thermally oxidized in air, using simple thermal oxidation technique. CO sensing properties of CuO thin film are evaluated for different operating temperatures (150-250°C) and concentrations. The CuO nanostructure shows the maximum CO sensitivity for an operating temperature of 230°C. However, CO response increases with the CO concentration, which is finally saturates for a particular operating temperature.
Detection and discrimination of volatile organic compounds by noble metal nanoparticle functionalized MoS2 coated biodegradable paper sensors
(RSC, 2020) Hazra, Arnab
In the current study, noble metal nanoparticle functionalized MoS2 coated biodegradable low-cost paper sensors were fabricated for the selective detection of low concentrations of volatile organic compounds (VOCs). A MoS2 layer was grown on flexible cellulose paper by a two-step hydrothermal route and functionalized further by using noble metal nanoparticles like Au, Pd and Pt by a spray coating technique. MoS2 nanoflakes aggregating into a micro-flower morphology was confirmed by field emission scanning electron microscopy. X-ray photoelectron spectroscopy authenticated the existence of noble metal nanoparticles on the MoS2 surface. Sensors were then tested with seven different VOCs (≤100 ppm) of ketones, alcohols and aromatic hydrocarbon groups. Au–MoS2 and Pd–MoS2 showed inherent acetone and benzene selectivity with 50.5% and 45.7% responses, respectively, after exposure to 100 ppm concentrations at 50 °C. Paper sensors exhibited highly stable baseline resistances, less sensitivity towards humidity (∼75% RH) and an acceptable response/recovery time within 3–6 min at low temperature (50 °C). An additional effort was devoted to discriminating and recognizing different VOCs by using suitable classification algorithms utilizing four types of paper sensors, i.e. pure, Au, Pd and Pt MoS2. Principal component analysis and logistic regression schemes successfully classified five VOCs among the seven. Moreover, the sensing mechanism of the noble metal modified MoS2 paper sensor is discussed in light of the Schottky barrier model.
Development of CdS-doped TiO2 nanocomposite as acetone gas sensor
(Elsevier, 2021-09) Hazra, Arnab
In recent years, much interest has been shifted towards the design and development of gas sensing devices for use of detecting and identifying toxic gases. In this work, a CdS doped TiO2 nanocomposite, with 1–2 wt % CdS, is prepared in the form of films as a gas sensor. The results are described with X-ray diffraction (XRD) and atomic force microscopic (AFM) images. The response of the fabricated sensor is measured with exposure to acetone, propanol, and LPG of varied concentrations (0–5000 ppm) in ambient air at room temperature. It is found that an optimized 2 wt% CdS-doping extends the highest response, i.e. 71% for 5000 ppm acetone, which is more selective over propanol or LPG, and also superior than reported ever for TiO2 based sensors. The response and recovery times are improved from 85 s to 190 s for undoped TiO2 sensor to 55 s–115 s for acetone (5000 ppm). Possible mechanisms of finely tuned sensing properties are described in light of the microstructure.
Development of Graphene-Doped TiO2-Nanotube Array-Based MIM-Structured Sensors and Its Application for Methanol Sensing at Room Temperature
(MDPI, 2021-07) Hazra, Arnab
This work concerns the development of a good quality graphene doped TiO2 nanotube array sensor for efficient detection of methanol. A pure and graphene doped TiO2 nanotube array was synthesized by electrochemical anodization. Morphological, structural and optical characterizations were performed to study the samples. Both the nanotube samples were produced in Au/TiO2 nanotube/Ti type MIM-structured devices. Pure and graphene-doped TiO2 nanotubes offered a response magnitude of 20% and 28% to 100 ppm of methanol at room temperature, respectively. Response/Recovery time was fast for the graphene doped TiO2 nanotube array (34 s/40 s) compared to a pure TiO2 nanotube array (116 s/576 s) at room temperature. This study confirmed the notable enhancement in methanol sensing due to the formation of local heterojunctions between graphene and TiO2 in the hybrid sample.
Device Modeling of Double Layered TiO2 Nanotube Array Based Resistive Vapor Sensor
(IEEE, 2018) Hazra, Arnab
Single and double layered TiO 2 nanotube array were synthesized by anodic oxidation method. Anodization voltage was varied to develop double layered TiO 2 nanotube array. Developed materials were characterized structurally and morphologically by X-ray diffraction spectroscopy (XRD)and field emission scanning electron microscopy (FESEM)respectively. Sandwich structure devices with Au top electrode and Ti bottom electrode were fabricated by using both single and double layered TiO 2 nanotubes for vapor sensing application. A simplified device modeling was introduced to establish the sensing mechanism of both the TiO 2 nanotube arrays. Additional interlayer junctions in double layered TiO 2 nanotubes array, enhanced the vapor sensing performance significantly. Double layered TiO 2 nanotubes array was able to show 92.4% of response magnitude for ethanol concentration of 160 ppm at 300 K where 55.2% response was observed for mono-layered TiO 2 nanotube array.
Dielectric Sensor System Using TiO2 Nanotubes for Real-Time Detection of Methanol Contamination in Alcoholic Beverages
(IEEE, 2020-09) Hazra, Arnab
In this article, a portable sensor system based on a TiO2 nanotube array is described for detecting methanol contamination in alcoholic beverages. TiO2 nanotubes were synthesized on a Ti substrate by using electrochemical anodization technique and Au contacts were deposited over TiO2 nanotubes by vacuum-assisted thermal evaporation technique. The TiO2 nanotube array was sandwiched in-between Ti and Au electrodes, which resulted in a capacitive-type structure of the sensor. The conductive and capacitive changes in the sensor operating at room temperature were then tested for pure ethanol, 10% and 25% methanol-contaminated ethanol, and pure methanol. The sensor exhibited a selective capacitive response toward all methanol-contaminated samples and recovered to its baseline capacitance value in less than 40 s. The dielectric sensor was then integrated with a 9-V, battery-driven, signal-processing circuit having a LED for notifying the information on methanol contamination in an alcoholic beverage. The integrated sensor system was able to detect 10%-100% methanol contamination in alcoholic beverages like whiskeys in less than 3 min.
Efficient acetone sensing by Pd nanoparticle loaded graphene Field Effect Transistor
(IEEE, 2021) Hazra, Arnab
In this work we have reported Pd/GO FET nanocomposite field effect transistor (FET) based acetone sensor. Pd nanoparticle loaded graphene oxide (GO) was prepared by one step spray coating technique at room temperature. The morphological and structural characterizations of developed pure GO and Pd/GO samples were performed with field emission scanning electron microscopy (FESEM), Raman spectroscopy and UV-Vis spectroscopy techniques. The effect of gate voltage on sensors at different temperature range (25- 75°C) was investigated by I DS -V GS characteristic. GO and Pd/GO FET sensors showed optimum response at 50 °C temperature with and without applied gate voltage. The response of Pd/GO FET sensor was around 8 % under zero gate voltage (V GS = 0 V) at operating temperature of 50 °C. Due to the application of gate voltage near Dirac point voltage (V GS =V dirac ), both the sensors showed a significant increment in the response magnitude where pure GO exhibited 22 % and Pd/GO exhibited 45 % response in the exposure of 80 ppm acetone at 50°C. The Pd/GO FET sensor showed ~6 times amplification in sensitivity as the consequence of applied gate voltage.
An efficient BTX sensor based on p-type nanoporous titania thin films
(Elsevier, 2015-03) Hazra, Arnab
Sensing 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.
Electrochemically grown nono-structured TiO2 based low power resistive random access memory
(IEEE, 2013) Hazra, Arnab
Nano TiO 2 thin film was grown on high purity Ti foil by electrochemical anodization techniques using 1 (M) as H 2 SO 4 electrolyte. Film was annealed at 600 0 C for 1 hour to prepare rutile crystalline TiO 2 . Au metal contact was used as a top electrode contact to fabricate Au/TiO 2 /Ti memory devices for RRAM application. XRD, SEM and optical studies of the the TiO 2 thin film were carried out to investigate the structural, morphological and optical characteristics of the prepared TiO 2 thin film respectively. Bipolar resistive switching characteristics was measured using five different Au/TiO 2 /Ti devices which showed very repeatable, reproducible and stable memory performance with very low set and reset voltage of +0.24 V and -0.25 V respectively without application of any electroforming voltage. Bipolar switching phenomenon was explained by Schottky emission theory as well as filamentary models.