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Author: search.filters.author.Hazra, ArnabSubject: search.filters.subject.Ethanol

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    Synthesis of Highly Ordered TiO2 Nanorods on a Titanium Substrate Using an Optimized Hydrothermal Method
    (Springer, 2022-02) Sarkar, Bibhas R.; Hazra, Arnab
    In this study, highly stable and well-oriented one-dimensional (1D) TiO2 nanorods were grown over a conductive titanium (Ti) substrate by optimizing various physical and chemical parameters involved in the hydrothermal method. Previous works have reported extensively on the synthesis of 1D TiO2 nanorods on fluorine-doped tin oxide-coated glass substrates using the hydrothermal method. However, glass substrates suffer from poor integration, compatibility, and stability issues when implemented in device applications. To overcome the challenges with glass substrates, in the current study, we propose an optimized hydrothermal route to synthesize highly ordered 1D TiO2 nanorods on a metal (Ti) substrate. The structural and morphological parameters of the nanostructures, including crystal phase, length, diameter, and density of nanorods, were studied with the help of field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction spectroscopy, and photoluminescence spectroscopy. The morphology of the nanostructures was varied by changing the chemical composition of the mother solution and physical parameters of time and temperature of the reactions involved during hydrothermal synthesis. It was shown that by optimizing the reaction parameters, multi-crystalline three-dimensional TiO2 nanoflowers could be transformed to single-crystalline 1D TiO2 nanorods. One-dimensional TiO2 nanorods on the Ti substrate were then implemented in a metal–insulator–metal (MIM) type of device (Au/TiO2 nanorods/Ti) and used for ethanol sensing. At 100°C, the sensor showed the maximum response magnitude of 61% towards 300 ppm of ethanol.
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    Nanostructural evolution of hydrothermally grown SrTiO3 perovskite and its implementation in gaseous phase detection of ethanol
    (IOP, 2023-07) Ghosh, Sarbani; Hazra, Arnab
    A group of SrTiO3 nanostructures with unique nano-architecture have been synthesized in the current study. Sol–gel derived TiO2 nanoparticles along with Sr(OH)2 solution was processed with facial hydrothermal reaction at 180 °C and highly stable and distinct morphologies of SrTiO3 were developed after different reaction time. Nanobush, nanograss, nanorod and nanosphere morphologies were created after 10, 14, 18 and 24 h of hydrothermal reaction. SrTiO3 nanosphere was transformed into nano-hollow sphere morphology after thermal annealing at 600 °C. Detailed morphological, structural and chemical characterizations were carried out for all the distinct nanoforms of SrTiO3 where they exhibited high crystallinity, and chemical stability along with excellent surface properties like high porosity, roughness, and large effective surface area. Due to having rich surface properties, all the SrTiO3 morphologies were then implemented for gaseous phase detection of multiple volatile organic compounds (VOCs). However, all the SrTiO3 nanoforms showed ethanol selective behavior among all the VOCs. Nanograss and nano-hollow spheres exhibited excellent ethanol sensing with 69 and 78 response values (Rv/Ra) in 50 ppm ethanol at 150 °C with appreciably fast response/recovery times of 36 s/34 s and 150 s/ 58 s, respectively. Additionally, all the SrTiO3 nanostructures exhibited anti-humidity characteristics and potential sensing in humid ambient (up to 80% RH). Later, the ethanol selective behavior of SrTiO3 was established by density functional theory simulations which envisaged the highest negative adsorption energy and smallest distance (r) for ethanol molecule, implying stable adsorption with SrTiO3 (110) system.
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    Ultrathin Films of TiO2 Nanoparticles at Interfaces
    (ACS, 2015-01) Gupta, Raj Kumar; Manjuladevi, V.; Hazra, Arnab
    The properties of a material change remarkably as a result of the scaling dimensions. The Langmuir–Blodgett (LB) film deposition technique is known to offer precise control over the film thickness and the interparticle separation. To form a well-ordered LB film, it is essential to form a stable Langmuir film at the air–water interface. Here, we report our studies on ultrathin films of TiO2 nanoparticles at air–water and air–solid interfaces. The Langmuir film of TiO2 nanoparticles at the air–water interface was found to be very stable, and it exhibits loose-packing and close-packing phases. The LB films were transferred onto solid substrates for characterization and application. The surface morphology of the LB film was obtained by a field emission scanning electron microscope. The optical and electronic properties of the LB films of TiO2 nanoparticles were studied using UV–vis spectroscopy and current–voltage measurements, respectively. The LB film of TiO2 nanoparticles was employed for ethanol gas sensing, and the sensing performance was compared to that of bulk material. Because of the enormous gain in the surface to volume ratio and the increase in crystalline defect density in the ultrathin LB film of TiO2 nanoparticles, the LB film is found to be a potential functional layer for ethanol sensing as compared to the bulk material.
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    Highly Repeatable Low-ppm Ethanol Sensing Characteristics of p-TiO2-Based Resistive Devices
    (IEEE, 2015-01) Hazra, Arnab
    In this paper, we report on the development of a highly sensitive, relatively low-temperature ethanol sensor based on sol-gel derived p-TiO 2 thin film. The p-type anatase TiO 2 thin film was deposited by sol-gel technique on a thermally oxidized <;100> p-Si (resistivity 5 Ω cm) substrate. Anatase TiO 2 phase with <;101> nanocrystallinity was confirmed with an average particle size of ~11 nm from X-ray diffraction and field emission scanning electron microscopic study. Ethanol sensor study, in the resistive mode, was carried out at a relatively low operating temperature range (75 °C-175 °C) for sensing low concentrations of ethanol in air (5-100 ppm). Response magnitude of ~146% was observed at 150 °C toward 100-ppm ethanol (in air) with corresponding response time and recovery time of 39 and 15 s, respectively. The sensor showed appreciably high-response magnitude (129%) even at low ethanol concentration (5 ppm) with acceptable response and recovery time (54 and 22 s, respectively) at the same operating temperature (150 °C). At a particular temperature, for all the ethanol concentrations, sensor showed minimal base line resistance drift, thereby offering highly repeatable and stable sensing performance. Ethanol selectivity study against other volatile organic compounds, such as methanol, acetone, and 2-butanone, was also investigated and was found to be quite promising. Ethanol sensing mechanism for such p-type TiO 2 has also been discussed in the light of corresponding oxygen vacancy model.
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    Electroless deposition of Pd/Pt nanoparticles on electrochemically grown TiO2 nanotubes for ppb level sensing of ethanol at room temperature
    (RSC, 2021) Hazra, Arnab
    This work presents a comparative sensing study of three sensors based on pristine TiO2 nanotubes, Pd loaded TiO2 nanotubes, and Pt loaded TiO2 nanotubes. Pristine TiO2 nanotubes were synthesized using an electrochemical anodization method and an electroless plating method was used for the uniform deposition of noble metal nanoparticles of either Pd or Pt over the surface of TiO2 nanotubes. The samples were thoroughly characterized by XRD, FESEM, EDS, TEM, and XPS techniques. The sensitivity of all three sensors was investigated at room temperature (300 K) for different volatile organic compounds like ethanol, methanol, 2-propanol, acetone, and benzene. The results revealed that loading of Pd and Pt nanoparticles improved the response magnitude of the sensor remarkably as these noble metals possess better oxygen dissociation capability than pristine TiO2. The Pd–TiO2 nanotube sensor exhibited a maximum response magnitude of 20–98% towards 100–1000 ppb of ethanol at room temperature. Notably, the formation of Pd/Pt–TiO2 discrete heterojunctions on the surface of TiO2 nanotubes was found to be responsible for enhanced sensitivity of the sensors.