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Subject: search.filters.subject.Field-emission scanning electron microscopy (FESEM)

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    Synthesis of graphene-type materials from agricultural residues
    (Springer, 2023-06) Roy, Banasri
    Preparation of graphene oxides (GO) from sugarcane bagasse and wheat straw is reported in this paper. Both of the crop residues are converted to graphite using low-temperature ferrocene method and high-temperature catalytic graphitization using iron and nickel nitrate powder. Iron nitrate was found out to be the superior catalyst compared to nickel nitrate at carbonization temperatures of 900 and 1200 °C. Improved Hummer’s method is applied for the synthesis of graphene oxide from graphite powders. The GO powders synthesized from wheat straw along with iron nitrate at 900 °C and sugarcane bagasse along with iron nitrate at 1200 °C were observed to be the best, while the graphite prepared using ferrocene method could not be converted to GO as confirmed by XRD, FTIR, RAMAN results, and the presence of oxygen in graphene oxide is determined by morphological studies using FESEM and TEM techniques
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    Highly selective formaldehyde sensing using ZnO nano-rods
    (AIP, 2023-03) Choudhary, Sumita; Hazra, Arnab; Gangopadhyay, Subhashis
    Early detection of formaldehyde emission from any household materials is technologically very demanding as it can be a serious human health hazard. Even indirect inhaling of formaldehyde may cause significant harm to our eyes, skin, mouth or any other organs. Hence, fabrication of a simple and sensitive formaldehyde sensor would be of high practical importance. Within this work, formation of ZnO nano-rods by controlled thermal oxidation of vacuum deposited thin Zn films in air ambient, followed by fabrication of formaldehyde sensor operating at relatively lower operating temperature are reported. The crystal structure, surface morphology and optical properties of the as grown ZnO nano-rods have been investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Raman spectroscopy, respectively. The XRD patterns of ZnO suggested the formation of highly crystalline oxide films whereas FESEM images have revealed its nano-rods surface morphology with significantly high (length to diameter) aspect ratio. Raman spectroscopy confirms the thermal oxidation of the Zn thin films. As-grown ZnO nano-rods were then subsequently used to fabricate the chemi-resistive formaldehyde sensors. These sensors showed an extremely high formaldehyde sensing performance at a relatively lower operating temperature of 200°C. In a static measurement mode, the sensor exhibited a gas response of about 53% toward 100 ppm of formaldehyde, with a reasonable fast response and recovery time. Moreover, these ZnO nano-rod based sensors have also been tested with similar type of VOCs such as benzene, xylene, alcohols and acetone and appeared with an excellent selectivity towards formaldehyde over the other VOCs.
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    Room-Temperature Au/TiO2Nanorods/Ti TFT Butanone Sensor: Role of Surface States
    (Springer, 2023-03) Hazra, Arnab
    A one-dimensional TiO2 nanorod-based thin film transistor (TFT) for butanone sensing is presented here. A low-cost hydrothermal process was used to deposit TiO2 nanorods on a Si/SiO2 substrate. X-ray diffraction, field-emission scanning electron microscopy (FESEM), photoluminescence spectroscopy, and Raman spectroscopy were used to examine the structural, morphological, and optical features of the nanostructure. Formation of aligned nanorods as the carrier transport channels in FET structure were confirmed through FESEM. Electrical characterization revealed the threshold voltage (VT), mobility (µ), transconductance (gm), Ion/Ioff ratio, and sub-threshold swing (SS) as 0.77 V, 12.2 cm2/V-s, 5.37 mS, 0.6 × 104, and 64.63 mV/dec, respectively. Sensor study exhibited an increase in the drain current (Id) and shifts in the threshold voltage (VT) upon exposure to different concentrations of butanone with respect to those in air. These two effects were correlated with the de-trapping of charge carriers at surface sites in association with resistance variation in the sensing layer. However, the room- temperature response towards butanone (82%) at Vgs of 3 V were found to be 16 times greater than the response under a no biasing (5%) condition. The repeatability of the as-fabricated and aged TFT indicates the potentiality of the device over conventional device structures even in harsh environments