Now showing 1 - 10 of 41
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    Ultrasensitive Organic Humidity Sensor with High Specificity for Healthcare Applications
    (2020-01-01)
    Bahuguna, Gaurav
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    Adhikary, Vinod S.
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    Humidity sensors have gained immense importance as non-invasive, wearable healthcare devices for personal care as well as disease diagnostics. However, non-specificity, poor stability at extreme conditions, and low sensitivity of the humidity sensor inhibit its usage as a health monitoring device. In the present study, N−F containing organic molecule, SelectfluorTM (F-TEDA) based humidity sensors with ∼1–2 mm long needle-shaped crystals is fabricated on interdigitated electrodes resulting in excellent performance. The unidirectional growth of crystals led to the formation of a conduction pathway for water molecules across the crystal, which otherwise are non-conducting. The as-fabricated humidity sensor at an operational voltage of 0.8 V displays a sensitivity of six orders in magnitude, best reported so far. The sensor does not exhibit any response upon exposure to various volatile organic compounds and reactive gases, indicating remarkable specificity. The sensor is tolerant to high moisture of 95 % for prolonged hours followed by monitoring over several days and degrades to 50 % of its original sensitivity only after continuous exposure for several days. Electrochemical impedance spectroscopy (EIS) shows reversal from resistive to capacitive behavior with increasing humidity levels. The fabricated humidity sensor acts as a healthcare device for breath rate monitoring and touch-free examination of skin moisture.
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    SnO2-MWCNT and SnO2-rGO Nanocomposites for Selective Electrochemical Detection in a Mixture of Heavy Metal Ions
    (2024-04-26)
    Verma, Mohit
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    Kumari, Ankita
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    Bahuguna, Gaurav
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    Singh, Vikas
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    Pareek, Vishakha
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    Dhamija, Anandita
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    Shukla, Shubhendra
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    Ghosh, Dibyajyoti
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    Metal oxide-carbon nanocomposites offer an interesting platform for electrochemical sensing due to the synergistic effect of a highly active semiconducting surface and conducting carbon as the supporting backbone. In this work, the in situ synthesis of SnO2 with reduced graphene oxide (rGO) led to the formation of small, uniform SnO2 nanoparticles, measuring 10-20 nm in size, whereas the inclusion of multiwalled carbon nanotubes (MWCNT) resulted in the formation of (200) oriented SnO2 nanoplatelets of ∼200 nm. X-ray photoelectron spectroscopy (XPS) demonstrates a chemical interaction between Sn and C rather than physical adherence. The cyclic voltammograms (CVs) of SnO2-rGO and SnO2-MWCNT display high peak current density and small ΔE in comparison to SnO2, signifying fast electron transfer, reversibility, and enhanced electrochemically active sites. Under optimized experimental conditions of square wave anodic stripping voltammetry (SWASV), the nanocomposites demonstrate high sensitivity (3.9, 9.9, 45.5, and 25.4 mA cm-1 ppb-1) and a low detection limit (in ppb) toward Cd2+, Pb2+, Cu2+, and Hg2+, respectively. The high selectivity of SnO2-rGO for Cd2+ and Pb2+ ions and SnO2-MWCNT for Hg2+ and Cu2+ in a complex metal ion environment is encouraging and is probed by using density functional theory (DFT). Additionally, an artificial neural network (ANN)-based model justifies the sensor’s accuracy and precision for real-time, on-site detection of heavy metal ions directly in tap water.
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    Deciphering the influence of fluorine on the electrochemical performance of MAX and derived MXene by selective electrophilic fluorination
    (2024-01-01)
    Bahuguna, Gaurav
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    Gaur, Snehraj
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    Patel, Avit
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    Verma, Mohit
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    Kiruthika, S.
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    The emerging class of MAX phases and corresponding MXenes offers a unique advantage of tunable surface functionalities, such as -O, -OH, and -F, which endow them with excellent electrochemical activity. This study focuses on the fluorination of the MAX phases and corresponding MXenes using an electrophilic fluorinating agent, Selectfluor (SF). The fluorination process was carried out to selectively fluorinate the MAX phase while minimizing etching effects, showcasing the distinct role of the electrophilic fluorine precursor over the conventional nucleophilic fluorinating agents. Intriguingly, the fluorinated MAX phase, with a fluorine content of 3.21 at%, demonstrated significantly enhanced electrochemical performance, exhibiting a two-fold increase in the specific capacitance compared to pristine MAX. Moreover, selective fluorination is further extended to MXene derivatives prepared through the conventional route. Using SF, we facilitated electrolyte-ion transport through the functionalized surface, resulting in an enhancement of ∼1400% in energy storage capacity after the fluorination of MXene. The observed improvement in the electrochemical performance can be attributed to the formation of electrochemically active Ti-F and C-F moieties at the surface as opposed to surface hydroxyls and oxidized MXene. The high electronegativity of fluorine atoms contributes to fast ion diffusion at the electrode surface, enhancing wettability and leading to superior electrochemical performance. As a result, our work introduces a novel and simple solution-based methodology for selectively fluorinating MAX phases and their MXene derivatives, unlocking their potential for enhanced electrochemical applications. This methodology can be extended to various MAX phases and their derivatives, offering precise control over the surface moieties in electrochemical systems where fine-tuning is essential for optimal performance. Overall, this study significantly contributes to advancing the understanding and utilization of fluorinated MAX and MXene materials in electrochemical energy storage and beyond.
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    Metal wire networks functionalized with nickel alkanethiolate for transparent and enzymeless glucose sensors
    (2018-10-26)
    Urgunde, Ajay B.
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    Kumar, Akshay R.
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    Shejale, Kiran P.
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    Futuristic healthcare technology including glucose sensors demands wearable components that ought to be transparent and flexible. Nickel nanostructures have proven to be highly efficient as electrocatalysts for glucose sensors. In this study, we explore single-source precursors of nickel alkylthiolate, Ni(SR)2, complexes as active electrode materials and coat them on a transparent gold (Au) mesh network to fabricate a transparent and highly efficient glucose sensor. The metal thiolate complex is electrooxidized in the alkaline medium by repeated cyclic voltammetry measurements to give rise to Ni redox-active centers with sharp anodic and cathodic peaks. Among different chain length metal alkylthiolates, nickel butanethiolate with the shortest carbon chain (C4) is found to be the most efficient in retaining sharp oxidation at low potential value and high current density. The electrochemical property of nickel butanethiolate toward glucose oxidation is examined on different electrode surfaces such as Au thin film, Au mesh, and fluorine-doped tin oxide (FTO). Interestingly, glucose oxidation takes place most efficiently on a Au mesh network compared to Au film and FTO substrates. The Ni(SC4H9)2/Au mesh exhibited two linear ranges of detection from 0.5-2 and 2-11 mM with a sensitivity value of 675.97 μA mM-1 cm-2 and a limit of detection of 2.2 μM along with excellent selectivity and reproducibility. The present study demonstrates that nickel butanethiolate on a Au mesh acts as a promising functional and transparent electrode material with the possibility of large-scale production for practical glucose detection.
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    Facile synthesis of nanostructured Ni/NiO/N-doped graphene electrocatalysts for enhanced oxygen evolution reaction
    (2024-01-01)
    Madampadi, Roshni
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    Patel, Avit Bhogilal
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    Vinod, C. P.
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    Jagadeesan, Dinesh
    Electrocatalysts containing a Ni/NiO/N-doped graphene interface have been synthesised using the ligand-assisted chemical vapor deposition technique. NiO nanoparticles were used as the substrate to grow N-doped graphene by decomposing vapours of benzene and N-containing ligands. The method was demonstrated with two nitrogen-containing ligands, namely dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (L) and melamine (M). The structure and composition of the as-synthesized composites were characterized by XRD, Raman spectroscopy, SEM, TEM and XPS. The composite prepared using the ligand L had NiO sandwiched between Ni and N-doped graphene and showed an overpotential of 292 mV at 10 mA cm−2 and a Tafel slope of 45.41 mV dec−1 for the OER, which is comparable to the existing noble metal catalysts. The composite prepared using the ligand M had Ni encapsulated by N-doped graphene without NiO. It showed an overpotential of 390 mV at 10 mA cm−2 and a Tafel slope of 78.9 mV dec−1. The ligand-assisted CVD route demonstrates a facile route to control the microstructure of the electrocatalysts.
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    Scalable Supercapacitors
    (2023-01-01)
    Gaur, Snehraj
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    Urgunde, Ajay B.
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    Bahuguna, Gaurav
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    Kiruthika, S.
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    In the past few decades, energy-storage technology has evolved rapidly as dependence on renewable energy sources have increased due to drastic changes in energy demands. A supercapacitor finds many applications that need high peak power and energy boosts, such as wireless sensor networks, regenerative braking in vehicles, IoT applications, RF transmissions, backup power supply, transport sector, energy harvesting systems, industrial and consumer electronics. Though the lab-scale supercapacitors perform well, there is considerable scope of improvement for commercially scalable supercapacitors. Low-cost, simple-processing, and high-performance material provides a possible solution for large-scale industrial efficient energy storage systems that can bridge the gap between lab-based energy storage technologies and large-scale commercial applications. The performance deteriorates with an increase in the size of devices due to the internal resistances from non-active materials such as binders and additives, and heating issues. To address these challenges, designer electrode structures such as self-standing architectures, mesh-type electrodes, and fractal design can be viable solutions to enhance the performance of large-scale energy storage devices. Industrial byproducts in the form of waste can be recycled and processed to synthesize cost-effective electrode materials. In addition, the fabrication of electrodes by printing techniques and additive nanomanufacturing has gained significant scientific attention as they are cost-effective and economical for the production of energy storage devices. Printing techniques such as inkjet, micro-gravure, and 3D printing possess the merit of easy manufacturing steps to produce scalable supercapacitors.
    Scopus© Citations 1
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    Fabrication of stretchable compliant electrodes on PDMS with Au nanoparticles
    (2018-10-01)
    A stretchable and compliant electrode surface of Au metal on polydimethylsiloxane (PDMS) is introduced in this study. A thin layer of Au nanoparticles is thus formed by a simple chemical reduction from aqueous Au salt solution with the AuPDMS gel surface itself acting as a reducing site. Employing the swelling behaviour of PDMS and Au nanoparticles affinity to bind with sulphur, an in-plane molecular device has been realized for measuring the conductance of thiol molecules. The device is capable of forming stable and robust linkages with Au. The molecules anchored between the Au islands are able to undergo reversible compression and tension, which shows the flexibility of the device.
    Scopus© Citations 3
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    Engineered ZnO-TiO2 Nanospheres for High Performing Membrane Assimilated Photocatalytic Water Remediation and Energy Harvesting
    (2018-07-06)
    Shejale, Kiran P.
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    Laishram, Devika
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    This paper is a study of ZnO doped TiO2 in various percentages ranging from 0% (undoped) up to 10%. The effect of doping was observed via the change in morphological, optical, electrical and physical properties of ZnO-TiO2 nanospheres. Hydrothermally grown nanospheres are used for removing contaminants photo-catalytically from waste water and also as photoanodes in dye-sensitized solar cells (DSSCs) with graphene as counter electrode. Of the many approaches that have been explored for purification of contaminated water, this work presents designing of an environmental friendly solution, based on easily available filter paper membrane and incorporating it with the synthesized catalyst for photodegradation of the harmful toxic substances. These reusable membranes assist in the photodegradation process by creating room for better light-catalyst-dye interaction via large surface sites. The spherically structured heterojunction of ZnO-TiO2 generates excitons that oxidize methyl orange (MO) and reduce harmful Cr(VI) to non-toxic Cr(III) with high efficacy. Additionally, the agile nanostructures were employed as efficient photoanode material by fabricating dye sensitized solar cells with graphene as counter electrode.
    Scopus© Citations 12
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    Visibly transparent supercapacitors
    (2023-01-25)
    Kiruthika, S.
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    Sneha, Namuni
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    Supercapacitors with novel functionalities such as transparency and flexibility are gaining attention to meet the increasing demand for intelligent and smart electronics. Transparent supercapacitors (TSCs) find application in modern appliances such as portable electronics and are especially inevitable for fully integrated transparent devices, thanks to their high-power density, fast charging and discharging ability, and longer life. Transparency is generally achieved by preparing thin films of active electrode material or by adopting lithographic methods for nanostructured electrodes that control the thickness and fill factor without significantly affecting intrinsic conductivity and capacitance. This review discusses all such approaches with a focus on the choice of electrode materials and their design and fabrication for achieving visible transparency in supercapacitors for advanced multifunctional devices. Additionally, it covers the basic concept, device structures, critical parameters, and figure of merit used specifically for transparent supercapacitors. An overview of recent experimental attempts to explore the potential applications of transparent supercapacitors is given, along with the challenges foreseen for the development.
    Scopus© Citations 19
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    Spin-Controlled Helical Quantum Sieve Chiral Spectrometer
    (2023-06-15)
    Maity, Arnab
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    Hershkovitz-Pollak, Yael
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    Wu, Weiwei
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    Haick, Hossam
    This article reports on a molecular-spin-sensitive-antenna (MSSA) that is based on stacked layers of organically functionalized graphene on a fibrous helical cellulose network for carrying out spatiotemporal identification of chiral enantiomers. The MSSA structures combine three complementary features: (i) chiral separation via a helical quantum sieve for chiral trapping, (ii) chiral recognition by a synthetically implanted spin-sensitive center in a graphitic lattice; and (iii) chiral selectivity by a chirality-induced-spin mechanism that polarizes the local electronic band-structure in graphene through chiral-activated Rashba spin–orbit interaction field. Combining the MSSA structures with decision-making principles based on neuromorphic artificial intelligence shows fast, portable, and wearable spectrometry for the detection and classification of pure and a mixture of chiral molecules, such as butanol (S and R), limonene (S and R), and xylene isomers, with 95–98% accuracy. These results can have a broad impact where the MSSA approach is central as a precautionary risk assessment against potential hazards impacting human health and the environment due to chiral molecules; furthermore, it acts as a dynamic monitoring tool of all parts of the chiral molecule life cycles.
    Scopus© Citations 2