Department of Electrical Engineering

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IIT Jodhpur

The present study aims to characterize the molecular interaction and photo-degradation behaviour of halogen (–F and –Cl) containing novel insecticide, flupyradifurone, (FPD) in the presence of humic acid (KHA), isolated from Karwar, western Rajasthan, India. Time-dependent photo-degradation kinetics of UV-exposed FPD is quantified in the absence and presence of KHA employing one dimensional 1H and 19F solution-state NMR. The pseudo first-order photo-degradation rate constant quantified for FPD showed a significant decrease in the presence of KHA. Interestingly, variable degradation rates are found from 1H and 19F NMR spectral changes indicating chemical moiety wise degradation of FPD. Further, NMR saturation transfer difference (STD), relaxation, and diffusion experiments have been employed for the complete evaluation of binding interactions of KHA with FPD and its major degradation product difluoroacetic acid (DFA). STD experiments revealed that FPD binds to KHA through the chlorinated pyridine ring while the –F containing moiety of FPD does not show any detectable interaction. Relevant kinetic parameters, namely association constants and Gibbs free energy of interaction are quantified at neutral pH conditions by diffusion experiments depicting a stronger and more spontaneous association of FPD with KHA (KA = 55.55 M−1) compared to that of DFA-KHA (KA = 10.90 M−1). Both FPD and DFA bind with KHA through weak non-covalent interaction indicating the encapsulation of these molecules within KHA hindering the photo-degradation process of FPD. Concomitantly, it is also envisaged that FPD will be more persistent in soil compared to DFA that may leach out to groundwater. © 2020

World University root node

Department of Chemistry

Journal of Photochemistry and Photobiology A: Chemistry

Aqueous photo-degradation of Flupyradifurone (FPD) in presence of a natural Humic Acid (HA): A quantitative solution state NMR analysis

In this work, solution-processed low voltage organic field-effect transistors (OFETs) are demonstrated using P(VDF-TrFE) as the primary gate dielectric with TIPS-Pentacene: Polystyrene (PS) blend on top, providing an active layer. Maximum field-effect mobility of 0.6 cm2 V-1s-1 with an average of 0.4 (±0.1) cm2 V-1s-1 in saturation region and high Ion/Ioff value of 104 were achieved from these devices at an operating voltage of -5V. Moreover, these devices exhibited excellent electrical stability upon multiple scans of transfer characteristics and under bias-stress. A deterioration in the performance of OFETs was observed upon annealing at temperatures over 50 °C. © 2021 IEEE.

FLEPS 2021 - IEEE International Conference on Flexible and Printable Sensors and Systems

Effect of Annealing on Low-Voltage Organic Field-Effect Transistors with P(VDF-TrFE) Gate Dielectric

In this report, we have demonstrated the optical non-volatile memory characteristics using CuPc OFET. The memory operation was comprehensively demonstrated with different programming conditions. It was found that the programming of CuPc OFET with an electric pulse at the gate terminal under UV-light photo-illumination compared to other programming conditions, could substantially increase the memory window due to massive charge trapping in the polymer electret layer, which causes shift in the device transfer characteristics from low-conduction state (“OFF state”, or logic 0) to high conduction state (“ON state”, or logic 1) at VGS = 0V. From device operation at −50V, a memory window of greater than 45V could be achieved by applying a programming voltage of +70 V at the gate terminal under UV-light photo-illumination. Moreover, it was completely erased by applying −100 V at the gate terminal in dark. © 2021 Elsevier B.V.

Organic Electronics

UV assisted non-volatile memory behaviour using Copper (II) phthalocyanine based organic field-effect transistors

This article reported about the ultraviolet (UV) radiation effect on the resonance frequency response of a AT-cut piezoelectric quartz crystal. A large resonance frequency upshift was observed when the quartz crystal was irradiated by UV light of 355-nm wavelength using a Q-switched pulsed Nd:YVO4 UV laser. The dynamic frequency response behavior was systematically investigated by illuminating the quartz crystal with UV light in which the UV intensity was varied with time in staircase- and linear pulse-shaped patterns. From the experimental analysis, we measured the limit of detection and the sensitivity of the quartz crystal, which are about 0.5 mW/cm2 and 0.706 Hz/(mW/cm2), respectively. For a constant UV irradiation, a moderate response (<10 s) and recovery (<10 s) times were achieved during the on and off cycles of the UV light. The short-term repeatability and maximum operating limit of AT-cut quartz crystal were also further studied upon exposure to UV light with different intensities. In this work, we not only demonstrate the impact of UV irradiation on quartz crystal but also discuss the mechanism of upshift in resonance frequency upon exposure to UV light. This study shows the applicability of quartz crystal for the detection of UV light. © 1963-2012 IEEE.

IEEE Transactions on Electron Devices

UV Light Detection Using Resonance Frequency of Piezoelectric Quartz Crystal

Pristine ZnO based hydrogen sensors pose low sensitivity ( 43%) at the operating temperature of 150°. Herein, we explore the decoration of Phosphorene oxide quantum dots (POQDs) on RF sputtered grown ZnO nanostructures for hydrogen gas sensing application. A simplistic approach such as drop cast method is employed to decorate electrosynthesized POQDs (2- 8μ L) onto interdigitated electrodes over ZnO nanostructures. The suggested hydrogen sensor based on POQDs (6μ L)/ZnO nanostructures exhibits an outstanding sensing response (70.6%) as compared to all the sensors for 100 ppm at 150°C. Enhanced sensing response from the POQDs(6μ L)/ZnO nanostructure might be due to the enormous active surface area of POQDs (provides more active sites for hydrogen gas) and modulation of depletion region at the interface of POQDs and ZnO. The proposed sensor can be operated at mild temperature and consume low power which is the need of the hour for the hydrogen sensors for industrial applications. © 2001-2012 IEEE.

IEEE Sensors Journal

Phosphorene Oxide Quantum Dots Decorated ZnO Nanostructure-Based Hydrogen Gas Sensor

Reduced graphene oxide (rGO) has tunable properties and acts as an efficient low-cost alternative for graphene in many applications. It also has its own exciting electronic and optoelectronic characteristics. The properties of rGO can be altered by tuning the amount of reduction, types of defects, doping and functionalization. The reduction of graphene oxide (GO) by various methods and the large-scale production of rGO can be easily achieved. These properties led the research drive for low-cost and high-end applications of rGO-based devices. It has found applications in almost all branches of applied science and engineering. Recent research works show that rGO-based photodetectors achieved high responsivity and detectivity values with fast operation speed. Although there are many reviews on graphene-based photodetectors, there has been much less focus on rGO-based photodetectors. In this review, we focus on rGO-based photodetectors, photodetection mechanism and advancements in the field. Thus, in this review, we provide a much-needed timely update and future prospects to the scientific community. © The Royal Society of Chemistry 2021.

Journal of Materials Chemistry C

Recent advances and prospects in reduced graphene oxide-based photodetectors

In recent years, the utilization of gas sensors has increased tremendously in daily life and industry. Importantly, appropriate material selection should be made for gas sensors in order to achieve outstanding gas sensing performance, such as high sensitivity, good selectivity, a fast response/recovery time, and long-term stability. Numerous studies have shown that neither pure metal oxide semiconductor nor individual 2D nanomaterial (graphene, transition metal dichalcogenides, metal-organic frameworks, metal oxide nanosheets, MXenes, and phosphorene) based gas sensors are capable of showing excellent gas-sensing performance towards gas molecules. However, synergistic combinations of metal oxides and 2D nanomaterials have demonstrated enhanced gas-sensing performance in many studies. This review aims at providing a comprehensive summary of the current advancements in 2D/metal-oxide based heterostructures as gas sensors. Additionally, the underlying sensing mechanisms of various kinds of gas sensors are systematically described, and the device architectures and their corresponding sensing performances are summarized. Finally, the challenges and future prospects of 2D/metal-oxide nanocomposite-based gas sensors for sensing applications have been outlined.

JOURNAL OF MATERIALS CHEMISTRY C

Gas sensing performance of 2D nanomaterials/metal oxide nanocomposites: a review

Drop-casting is a simple deposition technique where a slurry-like solution of nanomaterial is coated on small substrates, which are then allowed to dry under controlled temperature and pressure ambience. The present work focuses on the tyrosine functionalized benzene-tri-carboxyamide (Tyr-BTC) and ZnO composite based sensor deposited using drop-cast method for sensing carbon monoxide (CO) at room temperature. The composition of the composite surface was varied by altering the molar concentration of the constituents. The performance of the mesoporous structures in room temperature gas sensing was studied for the CO concentration range of 5-300 ppm in synthetic air. The highly amplified gas sensing response of approximately 94% at 300 ppm of CO by Tyr-BTC-ZnO in molar concentration 2:3 of Tyr-BTC-ZnO was observed. The improvement in the capacitance change, quicker response time, good linearity and reversibility was attributed to the synergistic effect between ZnO and tyrosine functionalized BTC. © 2020 IEEE.

Mesoporous Tyrosine Functionalized BTC-ZnO Composite for Highly Selective Capacitive CO Sensor

A highly sensitive and robust polysilicon Field Effect transistor (SiFET) has been developed for the detection of an gold standard biomarker of myocardial infarction (AMI) Cardiac Troponin I (cTnI). This paper reports a polysilicon FET device integrated with a thin film of gold layer as a gate terminal which is biofunctionalized with specific cTnI binding single stranded DNA receptor aptamer to detect cTnI. The reported SiFET is fabricated using standard microfabrication unit processes. The detailed characterization of reported device is performed and thoroughly discussed at different stages of device development. The assessment of bio-interface is also studied using various surface characterization techniques such as Raman spectroscopy, Atomic force microscopy (AFM) and Contact angle measurements. The experimental results showed the significant response for cTnI concentration as low as 0.1 ng ml-1 for label free detection. © 2021 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

Journal of the Electrochemical Society

Polysilicon Field Effect Transistor Biosensor for the Detection of Cardiac Troponin-I (cTnI)

Controlled growth of ZnO-based nanostructures, starting from a vertical nanowall surface morphology to laterally grown highly anisotropic nanorods/wires formation has successfully been achieved by controlled thermal oxidation of thin Zn films for a temperature range of 100–700 °C. The as-grown ZnO nanorods were further used for carbon monoxide gas sensing at low temperatures (down to 150 °C) as well as ethanol vapour sensing at room temperatures. Thin films of Zn were deposited on glass and silicon substrate at room temperature, using a vacuum-assisted thermal evaporation technique. Structure, morphology and chemical property of ZnO layers were investigated using various surface characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS) and Raman spectroscopy. The XRD and SEM results are in very good correlation and showed vertical growth morphology of ZnO nanowall/sheet structures at a relatively lower oxidation temperature up to 400 °C. However, at higher oxidation temperature, lateral growths started to dominate over the vertical growth. Oxidation at 700 °C appeared with laterally grown one-dimensional (1D) ZnO nanowires/rods of high density. Raman spectroscopy and XPS results suggested that the vertical growth is mainly initiated by the metallic Zn film morphology, whereas the lateral growth is strongly dominated by the oxide (ZnO) formation. Finally, laterally grown ZnO nanorods could successfully sense CO gas and ethanol vapour. A drastic enhancement in CO gas sensitivity for a concentration of 230 ppm was clearly observed in dynamic gas flow mode even for a wide range of operating temperature. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.