Browsing by Author "Ashish Kumar Kushwaha"

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A dual epitope-imprinted polymer@AuNP-MoS2 nanosheets-EQCM sensor for antibody free detection of SipD protein of Salmonella typhi bacteria with high selectivity
(Elsevier B.V., 2025) Akriti Srivastava; Ashish Kumar Kushwaha; Pinky Sagar; Anirban Parida; Roop Shikha Singh; Sanjay Kumar Srivastava; Richa Raghuwanshi; Gopal Nath; Meenakshi K. Singh
Dual-epitope imprinted EQCM sensor for selective and sensitive detection of Salmonella typhi bacterial protein is fabricated on gold nanoparticle decorated MoS2 nanosheets (AuNPs-MoS2NSs). Salmonella invasive protein D (SipD) binds to the needle protein and appears capable of interacting with the translocon complex to infect the host. Potential B cell antigenic epitope sequences from bacterial tip protein, SipD were intentionally tagged with cysteine and are used as dual templates to fabricate MIP sensor using methacryloyloxyethyl phosphorylcholine (MPC), benzyl methacrylate (BMA) and methacrylic acid (MAA) as monomers and N , N ′-methylene- bis -acrylamide as a crosslinker. The monomers chosen through docking produced a DEIP-EQCM sensor. The sensor was able to show specific binding towards the blood samples of infected patients, even in the presence of ‘matrix’ of ‘real’ samples and other plasma proteins. It has shown excellent specificity, sensitivity and selectivity in sensing range of 100–1000 nM with detection limit 1.65 nM (Epitope I) and 0.025 nM (Epitope II) and limit of quantification as 5.03 nM (Epitope I) and 0.075 nM (Epitope II) for the two epitope sequences imprinted. Sip D protein binding was substantiated by SDS-PAGE analysis. The repetitive experimental runs could not mutilate the specific geometries of respective imprinted cavities and the DEIP-EQCM sensor can be proposed for antibody free detection of Sip D protein. © 2025 The Authors.
Achieving flexibility/rigidity balance through asymmetric Donor−Acceptor scaffolds in pursuit of dual state emission with application in acidochromism
(Elsevier Ltd, 2021) Vishwa Deepak Singh; Ashish Kumar Kushwaha; Roop Shikha Singh
Three novel chalcone based asymmetrical D–A–D′–A'chromophores (C1–C3) have been designed and synthesized with intent to achieve dual state emission. It has been contemplated that introducing both flexible and rigid moieties to the D–A core will suffice for the emission in solution as well as solid state. In this regard flexible piperazine unit has been introduced along with rigid polyaromatic hydrocarbons anthracene, C1; pyrene, C2 and phenothiazine, C3 to afford an asymmetric D–A construct. The compounds have been thoroughly characterized by spectroscopic studies (1H, 13C, ESI–MS, UV/Vis and fluorescence). The compounds C1–C3 display varying degree of dual state emission as envisaged by photo-physical investigation in solution, aggregated and solid state along with quantum yield assessment. Notably the aggregation has been instigated in these compounds by taking advantage of relative hydrophilicity/hydrophobicity of different solvent systems. The revered intramolecular charge transfer (ICT) imparts substantial solvatochromism to these D−A constructs. The prudence of incorporation of heteroatomic phenothiazine unit to the designed chromophores is reflected in superior dual state emission and solvatochromism of C3. In addition, these compounds revealed remarkable acid–induced fluorescence quenching effect in solution and solid state as the emission of C1–C3 could be quenched by trifluoroacetic acid (TFA) significantly. © 2020 Elsevier Ltd
AIE−Active BODIHYs Based on Benzothiazole–Hydrazone Chelates and Their Artificial Light Harvesting and Reversible Mechanochromic Behavior
(John Wiley and Sons Ltd, 2025) Nikhil Kumar Singh; Ashish Kumar Kushwaha; Daya Shankar Pandey
Efficient artificial light-harvesting systems (ALH) involving energy transfer via FRET in an aqueous environment has been reported. Hydrazone ligands L1−L3 and -BF2 complexes (BODIHYs; B1−B3) derived from these have been synthesized and meticulously characterized by various techniques like1H, 13C, 11B, 19F NMR, ESI–MS, UV–vis, fluorescence spectroscopy, and structures of B1 and B2 unequivocally determined by X−ray single crystal analyses. Applicability of the B1−B3 have been examined as a LHS platform and categorically shown that these in combination with rhodamine B (RhB) display efficient light harvesting activity under aqueous conditions via aggregation−induced emission (AIE). Calculated energy transfer efficiency and antenna effect for the BODIHYs are significantly high (B1 = 22%, 5.04; B2 = 18%, 4.07) at a donor/acceptor ratio of 23:1. Furthermore, hypsochromic shift shown by B1 and B2 after grinding completely reverses upon exposure to dichloromethane vapors. Powder X−ray diffraction (PXRD) analyses before and after grinding revealed that the external forces modify crystal packing by disrupting weak intra− and intermolecular interactions within the molecules. © 2025 The Author(s). Chemistry - An Asian Journal published by Wiley-VCH GmbH.
Artificial light harvesting gel based on saponification-triggered gelation of aggregation-induced emissive BODIHYs
(Royal Society of Chemistry, 2024) Durgendra Yadav; Vishwa Deepak Singh; Ashish Kumar Kushwaha; Anjani Kumar; Roop Shikha Singh
The present work provides a detailed study on saponification-triggered gelation of ester-based BODIHYs (B1 and B2) derived from ethyl 4-(2-(benzo[d]thiazol-2-yl(cyano)methylene)-hydrazinyl)-benzoate (L1) and diethyl 5-(2-(benzo[d]thiazol-2-yl(cyano)methylene)hydrazinyl)-isophthalate (L2). The ligands and BODIHYs display good emission in the solution and solid states. This study describes the gelation of BODIHYs for the first time, wherein stable gels GL2 and GB2 were prepared via saponification-triggered gelation of L2 and B2, respectively. The gelation and optical properties of the ligands and BODIHYs were compared through single-crystal X-ray diffraction studies. This work further explores the prospect of artificial light harvesting (ALH) via fabrication of ALHSs in the solution {B1/rhodamine B (RhB) and B2/RhB} and gel states (GB2/RhB). It was observed that in the presence of RhB, the emission intensities of BODIHYs and the gel decreased but those of RhB increased. The significant overlapping between the absorption spectrum of RhB and emission spectra of aggregates/gel suggests the possibility of energy transfer via noncovalent interactions. In these systems, B1, B2 and GB2 served as donors, whereas RhB served as an acceptor. © 2024 The Royal Society of Chemistry.
Competitive ICT in asymmetric D−A Scaffolds showing visible solvatochromism, temperature-induced emission enhancement and AIE based acidochromism
(Elsevier B.V., 2022) Ashish Kumar Kushwaha; Yogesh Kumar; Surendra Kumar; Roop Shikha Singh
Meticulous attention to details of intramolecular charge transfer (ICT) has proved to be an effective strategy to design donor-acceptor fluorophores equipped with multichromic behaviour. Herein, we report three asymmetric donor-acceptor fluorophores bearing A′−D−A−D−A′ and D′−D−A−D−D′ scaffolds. The D−A−D core has been modified by appending pyridine/pyrimidine as additional acceptor and phenyl as additional donor and piperazine as flexible spacers. The asymmetric scaffold has equipped them with naked-eye solvatochromism even under daylight which further authenticated the effective charge separation in ground as well as excited state. The comparative account of photophysical behaviour displays the varying extent of twisted intramolecular charge transfer (TICT) owing to asymmetry. The interplay of restricted intramolecular rotation (RIR) and TICT leads to AIE induced H+ sensing and reversible acidochromism in PC1 which can be visualized by a comparatively uncommon acid induced emission enhancement. The activation of vibrational bands at higher temperature leads to a rare temperature induced emission enhancement in PC1−PC3. PC1 has been developed as the very first ‘turn-on’ thermochromic sensor based on β-diketone-boron difluoride (BF2bdk) complexes. © 2022 Elsevier B.V.
Lysosome-targeting solid state NIR emissive donor-acceptor molecules: a study on photophysical modulation through architectural distinction
(Royal Society of Chemistry, 2024) Ashish Kumar Kushwaha; Ankit Kumar Srivastava; Pradeep Kumar; Anjani Kumar; Saripella Srikrishna; Roop Shikha Singh
The prevalence of the D-A strategy in achieving red-shifted emission has been established through designing D-A molecules of D-A-D and A-D-A constructs. Architectural control over such D-A systems integrates solid state NIR emission with lysosome tracking and sets a multifarious goal of photophysical modulation in a comprehensive way. In particular, two compounds, CPM-1 (D-A-D) and CPM-2 (A-D-A), have been synthesized by introducing carbazole-based donors and difluoroboron acceptors. Lysosome targeting and imaging have been achieved through incorporation of a morpholine unit, which ultimately imparts viscosity sensitivity to the construct. The fluorophores exhibited significant emission in solution along with distinctive solvatochromism, viscochromism and TICT. A comparative account of these competitive photophysical properties revealed the superior charge transfer properties of the A-D-A construct (CPM-2), while the D-A-D molecule (CPM-1) was found to be a better molecular rotor with marked viscochromism. The solid state NIR emission has been found to be much more intense in CPM-1 relative to CPM-2, which further highlights the influence of structural aspects on photophysical behvaiour. Theoretical studies further established the distinctive characteristics of ground and excited states in these compounds. Owing to its excellent viscochromic behvaiour, CPM-1 has been successfully utilized in lysosome targeting in wild-type Drosophila fly gut tissues through co-localization studies. © 2024 The Royal Society of Chemistry.
Mechanochromism and aggregation-induced emission directed by donor strength in quinoxaline-based D-A molecules with application in latent fingerprinting and inkless writing
(Royal Society of Chemistry, 2025) S. Dasaratha Kumar; Ankit Kumar Srivastava; Ashish Kumar Kushwaha; Anjani Kumar; Roop Shikha Singh
The molecular structure influences essential properties such as photoluminescence, charge transfer, and mechanical responsiveness, directly impacting material performance in optoelectronics, sensing, and bioimaging. The present work is a systematic effort to develop three organic molecules (QPA1, QPA2 and QPA3) having a donor-acceptor construct, wherein the charge transfer (CT) states were augmented with an aggregation-induced emission (AIE) effect. The synthesized molecules feature an aminophenyl group as the donor and formylated quinoxaline core as the acceptor. The variations in the donor strength on the aminophenyl core, from -H (QPA1) and -Me (QPA2) to -Ph (QPA3), profoundly and intricately modulated the AIE attribute as well as the CT states. QPA1 turns out to be an aggregation-caused quenching (ACQ) fluorophore, while QPA2 and QPA3 behave as AIEgens, with QPA3 showing superior efficiency. Furthermore, the charge transfer properties are modulated by donor strength, with QPA3 demonstrating a more pronounced intramolecular charge transfer response. QPA1-QPA3 molecules have significant solid-state emission and have shown mechanofluorochromic (MFC) behaviour in response to mechanical stress. The MFC response varies with the change in substituents. The excellent AIE activity of QPA3 has enabled its exploration for latent fingerprinting with three levels of detailing. The good contrast and brightness in the solid-state emission of QPA1 and QPA3 were further utilized for inkless writing application. © 2025 The Royal Society of Chemistry.
Regioselective sulfenylation of indoles using sulfonyl hydrazides: In silico design, DFT calculation, hirshfeld surface analysis, ADMET study, molecular docking and anticancer activity
(Elsevier B.V., 2025) Ashvani Yadav; Vishal K. Singh; Rohit Kumar; Vikas G. Yadav; Ashish Kumar Kushwaha; Vikas Kumar Rana; Ajay Kumar; Virendra Prasad
We report the design, synthesis, and anticancer evaluation of some novel indole thioethers, constructed via an efficient and regioselective sulfenylation of indoles with sulfonyl hydrazides, facilitated by KSCN. This method offers a valuable tool for the synthesis of a variety of indole thioethers under mild reaction conditions with good to excellent yields. Initially, the drug like properties of all compounds were evaluated. Subsequently, six lead compounds were subjected to molecular docking studies targeting the active site of the B-RAF protein (PDB ID: 1UWH). These compounds demonstrated strong interactions with key amino acid residues, including Lys482 (3.47 Å), Gln529 (3.28 Å), Thr528 (2.85 Å), Phe467 (2.85 Å), Gly95 (2.86 Å), Thr598 (3.30 Å), His538 (3.37 Å), Ser535 (3.22 Å), and Asn579 (3.43 Å), suggesting their potential as anticancer agents. DFT calculations of the novel thioethers revealed their energy gaps and binding affinities, while Hirshfeld surface analysis highlighted significant intermolecular interactions within their crystal structures. In vitro cell-based assays were conducted on selected compounds to assess their cytotoxicity against human cancer cell lines. The results suggest that extending the exposure duration beyond 24 h may uncover significant cytotoxic effects. In conclusion, these compounds exhibit promising potential as anticancer agents against the tested human cancer cell lines. © 2025 Elsevier B.V.
Visible light-driven molecular oxygen activation for oxidative amidation of alcohols using lead-free metal halide perovskite
(Royal Society of Chemistry, 2024) Vishesh Kumar; Ved Vyas; Deepak Kumar; Ashish Kumar Kushwaha; Arindam Indra
Herein, we report the modulation of the band structures of halide perovskite Cs2CuBr4 by tuning the synthesis methods. The photocatalyst PC-1, synthesized by the hot injection method, has a more negative conduction band minima (CBM) than the photocatalyst PC-2, synthesized at room temperature. As a result, PC-1 can activate molecular O2 more efficiently to initiate the radical-mediated dehydrogenation of alcohols. The more positive valence band maxima (VBM) of PC-1 also facilitates amine oxidation to the corresponding radical. Further, improved charge separation and transport and a decrement in the photogenerated charge carrier recombination have been detected for PC-1 to enhance photocatalytic activity. PC-1 showed improved yields for a series of structurally diverse amides (highest yield = 98%) by oxidative amidation of alcohols under visible light irradiation. © 2024 The Royal Society of Chemistry.