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Author: search.filters.author.Lakshmi, V.Subject: search.filters.subject.Binding sites

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    Croconic acid-based zwitterionic conjugated porous polymer featuring nitrogen-rich triazine cores for enhanced iodine capture
    (Elsevier B.V., 2025) Ravikumar, M.V.; Lakshmi, V.
    Increased nuclear energy consumption leads to the enormous release of hazardous gases such as iodine into the environment. To address this concern, two zwitterionic Conjugated Porous Polymers (CPPs) CTTz and STTz have been synthesized by incorporating nitrogen-rich TTz with zwitterionic CA/SA under catalyst-free solvothermal conditions to achieve efficient multi-state iodine adsorption. The multiple active binding sites serve their dominance in trapping iodine species effectively. The polymers demonstrated exceptional iodine adsorption capabilities in both vapour phase and solution phases, with ?6.4 g/g and ?1.1 g/g iodine adsorption for CTTz and ?4.6 g/g and ?1.6 g/g for STTz, respectively. The zwitterionic backbones (CA/SA) in the polymer framework facilitated the formation of charge transfer complexes with iodine species, and the presence of triazine moieties enhances adsorption. The exceptional iodine capturing by CTTz and STTz lasted over a period of five cycles (?80 %). The iodine-loaded and recovered CPPs were analyzed using FTIR, FESEM, BET, XRD, and Raman spectroscopic studies, revealing the capture and release of different iodine species (I2, I3-, and I5-) by adsorbents. These findings offer valuable insights for designing and developing advanced zwitterionic adsorbent materials for effective dual-phase iodine capture and removal. Environmental implication: Uncontrolled release of radioactive iodine from nuclear energy sources poses a significant environmental and public health risk due to its volatility, mobility, and potential for bioaccumulation. Thus, it is essential to develop highly efficient, regenerable, and chemically stable adsorbents for removing iodine contamination in both vapour and solution phases. This study presents CTTz and STTz synthesised using Tris(4-aminophenyl)triazine and croconic/squaric acid building blocks, demonstrating exceptional iodine capture in both phases. Their robust structures, rich in nitrogen, oxygen and ionic binding sites, enable efficient charge-transfer complex formation with iodine species under ambient conditions. These results promote next-generation adsorbent development for nuclear waste management and provide a viable solution for preventing iodine radionuclide environmental contamination. © 2025 Elsevier B.V.
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    ortho-Halogen functionalized N-squaraines: structure–property relationship and dual-mode colorimetric and fluorometric sulfide ion detection
    (Royal Society of Chemistry, 2025) Fernandes, P.P.; Shenoy, A.M.; Grover, V.; Veeranagaiah, N.S.; Lakshmi, V.
    Symmetric ortho-halogen derivatives of anilinium N-squaraines were synthesized and characterized using 1H-NMR, mass, FT-IR, and single-crystal X-ray diffraction techniques. The effect of halogen substituents (–F, –Cl, –Br, –I) on the optoelectronic and electrochemical properties of N-squaraines has been thoroughly investigated. Additionally, the theoretical calculations demonstrated that the ortho functionalization slightly lowers the HOMO–LUMO energy band gap, which aligns with the optical band gap. Moreover, the solid-state photophysical characterization revealed that the photo-excited state remains a singlet, even in the presence of heavy atoms like bromine and iodine. The solid-state fluorescence emission was also significantly higher than in the solution state, with the quantum yields soaring up to 24%. Further, the two acidic binding sites in the synthesized compounds 2–5 were evaluated for anion sensing. The o-halo-derivatives act as selective dual-mode colorimetric and “Turn-On” fluorometric chemosensors for sulfide anions, with the solution changing from colorless to yellow and a four-fold enhanced emission intensity. Furthermore, adding acid makes the solution turn colorless again, as investigated in detail using the o-chloro-derivative. The chemosensor displayed good reversibility for up to seven cycles and demonstrated applications in molecular logic gates. This journal is © The Royal Society of Chemistry, 2025