Faculty Publications
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Item Colorimetric chemosensors for the detection of environment-polluting arsenite and cyanide(wiley, 2023) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.Due to the biotic and ecological implications of extremely deadly cyanide and arsenite ions, the design, manufacturing, and development of cyanide and arsenite chemosensors has been a particularly active study subject in recent decades. The main works on colorimetric/fluorimetric chemosensor sensing mechanisms and their application in cyanide and arsenite detection are summarized and highlighted. This book chapter categorizes cyanide sensors based on their structure, while arsenite sensors are segregated based on their detecting mechanism strategies. This chapter provides a detailed summary of current research in this field and will be valuable in creating and synthesizing novel cyanide and arsenite chemosensors. © 2024 WILEY-VCH GmbH. Published 2024 by WILEY-VCH GmbH. All rights reserved.Item Solar active ZnO–Eu2O3 for energy and environmental applications(Elsevier Ltd, 2020) Subramanian, S.; Kumaravel, K.; K, K.; Bhat, D.K.; Iyer Sathiyanarayanan, K.; Swaminathan, M.ZnO–Eu2O3 nanocomposite was fabricated by a simple hydrothermal route. This material forms a potential class of photocatalysts in which the increased absorption behaviour in ZnO–Eu2O3 is expected to couple with the existing characteristics of Eu2O3 and ZnO materials. ZnO–Eu2O3 was characterized using surface analytical (SEM, EDS, HR-TEM, AFM, XRD) and spectroscopic techniques (XPS, DRS,PL). From the XRD patterns, formation of well-crystallized cubic Eu2O3 and hexagonal wurtzite phase of ZnO were inferred. Presence of nanoflake like structure with hexagonal ZnO and cubical Eu2O3 is shown by SEM pictures. ZnO–Eu2O3 possesses higher UV and visible absorption than Eu2O3 and ZnO. ZnO–Eu2O3 produces larger methanol oxidation current indicating its anodic catalytic efficiency in direct methanol fuel cells (DMFCs). This reveals higher electrocatalytic activity of ZnO–Eu2O3 than ZnO. It is observed that at ?1.6 V, cathodic current density (ipc) of ZnO–Eu2O3 (?103.17 mA cm?2) for Hydrogen evolution reaction (HER) is more than five times of ZnO (?18.19 mA cm?2) and the hydrogen evolved with ZnO–Eu2O3is 15.6 mL, which is higher than that of ZnO (6.8 mL). This indicates the superior catalytic property of ZnO–Eu2O3 in water splitting. This catalyst exhibited higher catalytic activity of 99.2% in the photodegradation of Rhodamine B (Rh-B) with natural sunlight in 75 min under neutral pH, whereas Eu2O3 and ZnO produced 60 and 82% degradations in the same time. Degradation quantum efficiency by ZnO–Eu2O3 is larger than ZnO and Eu2O3. ZnO–Eu2O3 was stable and reusable. The multifunctionality of this catalyst makes it suitable for energy and environmental applications. © 2020 Elsevier B.V.Item Synergistic effects of iron and hexagonal-Boron Nitride additions in copper-based composites for braking application(SAGE Publications Ltd, 2022) Cadambi, S.; K, K.; Lamture, N.; Kale, S.S.; Prabhu, T.This paper explores the addition of h-BN and iron to Cu-based brake pads on the performance benefits. It also investigates the effect of graded layering by synthesizing three and four-layer brake pads by powder compaction and sintering route. The top one or two layers are made of Cu-based composite containing Fe, h-BN, and W, while the middle layer is pure Cu and, bottom steel plate. Two different compositions were explored for the composites by varying Fe content. From the two composite compositions, brake pads with single-layer composite or two-layer composite were synthesized. Characterization of brake pad specimens was carried out using density measurements, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy. The brake pads were subjected to simulated braking tests at braking energy/cycle of 60, 96, and 136 K Joules. Wear rate, coefficient of friction, stopping distance, stopping time, and hardness were measured and compared among other brake pads. The brake pad containing single-layer Fe rich Cu composite showed the best performance in the simulated braking tests. EDS analysis of wear debris shows the formation of iron (boride, nitride, oxide) complex which is indicative of a surface with superior dry lubricating properties. This surface is a result of synergetic interaction between h-BN and Fe particles. The iron particles which are scattered in the Cu matrix composite act as low friction regions on the brake pad surface that interrupt the high friction regions on the Cu matrix, thus reducing the local and bulk temperature rise. The two-layer composite brake-pad showed performance intermediate to the two single-layer brake pads. No advantage due to higher thermal conductivities in Fe deficient composite was observed as the two composite layers, showed similar Fe contents in their matrix phases. © IMechE 2021.Item Colorimetric recognition of water-polluting inorganic arsenic anions using near-infrared chemosensors in organic and semi-aqueous medium(Springer Science and Business Media Deutschland GmbH, 2023) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.Highly sensitive and selective chemosensors N2R1–N2R3 for detecting water-polluting inorganic arsenic anions, arsenite, and arsenate were synthesized and characterized. The selectivity of anions was studied in the pure organic media as well as the organo-aqueous media. Receptors N2R1 and N2R3 exhibited selectivity toward arsenite ion over arsenate ion in the acetonitrile media with a Limit of Detection (LOD) of 0.119 ppm and 0.323 ppm, respectively. In 30% aq. DMSO, receptors N2R1–N2R3 displayed selectivity toward arsenite and arsenate with a better LOD of 0.044 ppm. The anion binding to the receptor achieved a spectral absorption shift toward the near-infrared region in both organic and aqueous media, making the receptors better colorimetric sensors. The cyclic voltammetric investigations, 1H–NMR titration, UV–Vis titration, and DFT experiments provided strong evidence for the initial H-bonding upon interaction with the anions and the subsequent deprotonation pathway for the detection of inorganic arsenic anions. © 2023, King Abdulaziz City for Science and Technology.Item Colorimetric chemosensors for the selective detection of arsenite over arsenate anions in aqueous medium: Application in environmental water samples and DFT studies(Elsevier B.V., 2023) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.Novel organic receptors N3R1- N3R3 were developed for the selective colorimetric recognition of arsenite ions in the organo-aqueous media. In the 50% aq. acetonitrile media and 70% aq. DMSO media, receptors N3R2 and N3R3 showed specific sensitivity and selectivity towards arsenite anions over arsenate anions. Receptor N3R1 showed discriminating recognition of arsenite in the 40% aq. DMSO medium. All three receptors formed a 1:1 complex with arsenite and stable for a pH range of 6–12. The receptors N3R2 and N3R3 achieved a detection limit of 0.008 ppm (8 ppb) and 0.0246 ppm, respectively, for arsenite. Initial hydrogen bonding on binding with the arsenite followed by the deprotonation mechanism was well supported by the UV–Vis titration, 1H- NMR titration, electrochemical studies, and the DFT studies. Colorimetric test strips were fabricated using N3R1- N3R3 for the on-site detection of arsenite anion. The receptors are also employed for sensing arsenite ions in various environmental water samples with high accuracy. © 2023 Elsevier B.V.Item Development of multi-analyte responsive sensors: optical discrimination of arsenite and arsenate ions, ratiometric detection of arsenite, and application in food and water samples(Royal Society of Chemistry, 2023) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.5-Nitro-2-furaldehyde based Schiff base chemosensors, N4R1-N4R3 with varying strengths of electron-withdrawing groups were developed for the discriminatory sensing of arsenite and arsenate ions in semi-aqueous media. Receptor N4R1 distinguished arsenite (AsO2−) and arsenate (AsO43−) anions colorimetrically in 30% aq. acetonitrile (MeCN) with a detection limit of 18 ppb for arsenite. N4R1-N4R3 also detected phosphate, arsenite and arsenate in 30% aq. dimethyl sulfoxide (Me2SO) solution and the selectivity for arsenite over arsenate was achieved at 50% aq. Me2SO solution with a noticeable bathochromic shift near 200 nm. All three receptors exhibited ratiometric detection for arsenite and were identified as stable over the 6-12 pH range. The computed high binding constants of the receptors N4R1-N4R3 for inorganic arsenic anions and phosphate in the range of 106 M−1 exposed the receptor's higher potential in the sensing process. Hydrogen bonding interaction followed by deprotonation and the ICT mechanism on binding with arsenite/arsenate/phosphate was confirmed by UV-vis and 1H-NMR titration, electrochemical studies, density functional theory studies, and mass spectral analysis. Fabrication of disposable paper strips and solid state sensing using silica gel were employed to conveniently detect arsenite and phosphate anions in real-life samples. The potential application of the receptors for detection in environmental and real-life samples was evaluated by analyzing food and water samples spiked with arsenite and phosphate anions. © 2024 RSC.Item Colorimetric differentiation of arsenite and arsenate anions using a bithiophene sensor with two binding sites: DFT studies and application in food and water samples(Royal Society of Chemistry, 2024) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.Chemosensor N7R1 with two acidic binding sites was synthesized, and the ability of the sensor to differentiate arsenite and arsenate in the organo-aqueous medium was evaluated using colorimetric sensing methods. N7R1 distinguished arsenite with a peacock blue color and arsenate with a pale green color in a DMSO/H2O (9 : 1, v/v) solvent mixture. The specific selectivity for arsenite was achieved in DMSO/H2O (7 : 3, v/v). The sensor demonstrated stability over a pH range of 5 to 12. The computed high binding constant of 9.3176 × 1011 M−2 and a lower detection limit of 11.48 ppb for arsenite exposed the chemosensor's higher potential for arsenite detection. The binding mechanism with a 1 : 2 binding process is confirmed using UV-Vis and 1H NMR titrations, electrochemical studies, mass spectral analysis and DFT calculations. Practical applications were demonstrated by utilizing test strips and molecular logic gates. Chemosensor N7R1 successfully detected arsenite in real water samples, as well as honey and milk samples. © 2024 The Royal Society of Chemistry.Item Colorimetric sensors for discriminatory detection of arsenite ions: Application in milk, honey and water samples and molecular logic gates(Elsevier Inc., 2024) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.Millions of people are exposed to dangerous arsenic levels in drinking water, highlighting the urgent need for affordable, continuous on-site arsenic monitoring methods. It is crucial to specifically detect arsenite among inorganic arsenic anions because it is more poisonous than arsenate. Addressing these concerns, the present study developed 5-(4-nitrophenyl)-2-furaldehyde based two colorimetric chemosensors, N5R3 and N5R4, with different signaling groups for the selective detection of arsenite anions over arsenate in DMSO/H2O (6:4, v/v). The red-shift in the UV–Vis absorption spectra supported the distinct color changes of sensors N5R3 and N5R4 displayed upon binding with arsenite. Sensors demonstrated stability over a pH range of 6 to 12 and exhibited stability over a considerable time period. Among the chemosensors, N5R3 exhibited the lowest detection limit of 7.41 ppb with a high binding constant of 2.9976 × 106 M?1 for arsenite. The 1:1 binding interactions between the chemosensors and arsenite were confirmed using B-H plot and Job's plot analysis. The intramolecular charge transfer (ICT) mechanism for detecting arsenite was proposed through UV and 1H NMR titrations, electrochemical studies, mass spectral analysis and DFT calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Both chemosensors efficiently recognized arsenite in real water, honey, and milk samples. © 2024 Elsevier B.V.Item Selective Chromogenic Chemosensors for Arsenite Anion: A Facile Approach to Analyzing Arsenite in Honey, Milk, and Water Samples(John Wiley and Sons Inc, 2024) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.In this study, two chemosensors, N5R1 and N5R2, based on 5-(4-nitrophenyl)-2-furaldehyde, with varying electron-withdrawing groups, were synthesized and effectively employed for the colorimetric selective detection of arsenite anions in a DMSO/H2O solvent mixture (8 : 2, v/v). Chemosensors N5R1 and N5R2 exhibited a distinct color change upon binding with arsenite, accompanied by a spectral shift toward the near-infrared region (??max exceeding 200 nm). These chemosensors established stability between a pH range 6–12. Among them, N5R2 displayed the lowest detection limit of 17.63 ppb with a high binding constant of 2.6163×105 M?1 for arsenite. The binding mechanism involved initial hydrogen bonding between the NH binding site and the arsenite anion, followed by deprotonation and an intramolecular charge transfer (ICT) mechanism. The mechanism was confirmed through UV and 1H NMR titrations, cyclic voltammetric studies, and theoretical calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Real water samples, honey, and milk samples were successfully analyzed by both chemosensors for the sensing of arsenite. © 2024 Wiley-VCH GmbH.Item Selective chromogenic nanomolar level sensing of arsenite anions in food samples using dual binding site probes(Elsevier Ltd, 2025) K, K.; Nityananda Shetty, A.N.; Trivedi, D.R.In the present study, two chromogenic probes, N7R2 and N7R3, each containing two binding sites, were designed and synthesized for the selective detection of arsenite in DMSO/H2O (1:1, v/v). The probes exhibited stability across a pH range spanning from 5 to 12. The lower detection limits of 2.01 ppb (18.86 nM) for N7R2 and 1.79 ppb (16.75 nM) for N7R3, which are much lower than the WHO recommended permissible limit of arsenite, confirmed the superior efficiency of the probes in detecting arsenite. The detection mechanism for arsenite was proposed through UV and 1H NMR titrations, electrochemical studies, and DFT calculations. Practical applications were demonstrated through the fabrication of test strips and molecular logic gates. The probes efficiently recognized arsenite in real water, honey, milk samples, and fruit/vegetable juices. Both N7R2 and N7R3 exhibited excellent recovery rates in the analysis of food samples, demonstrating the probes' usefulness in real sample analysis. © 2024