The rational design of stable, earth-abundant quantum dots with tuneable electronic and optical properties is crucial for advancing sustainable optoelectronic and photocatalytic technologies. In this work, density functional theory (DFT) is employed to investigate pristine and 3d transition-metal (TM)-doped armchair hexagonal silicon carbide quantum dots (AH-SiC-QDs, Si₅₇C₅₇H₃₀). Structural analysis reveals that pristine AH-SiC-QDs exhibit high stability (5.612eV), surpassing previously reported SiC- and AlN-based QDs. Upon TM incorporation, stability remains robust, with Ni-doping providing the strongest binding and Sc-doping the weakest. Electronic structure calculations show significant dopant-induced modifications in HOMO-LUMO distributions and bandgaps, where Ti- and Sc-doped systems achieve remarkable bandgap narrowing (1.056 and 0.919eV), indicating strong hybridization between dopant and host states. Optical absorption studies demonstrate pronounced red-shifts into the visible and near-infrared regions, with Sc- and V-doped systems offering extended light-harvesting potential. Mulliken charge and natural bond orbital (NBO) analyses confirm strong donor-acceptor interactions, orbital rehybridization, and enhanced charge transfer, directly linking dopant chemistry to improved catalytic and optoelectronic behaviour. These findings establish TM-doped AH-SiC-QDs as versatile and highly tuneable platforms for next-generation photocatalysis and energy conversion applications.

Heavy metal ion pollutants pose serious threats to human health and the environment due to their toxicity. An intuitive and convenient technique for detecting heavy metal ions is vital for qualitative monitoring and food safety. In this work, carbon dots (L-CDs) are prepared from a green source (lemon leaves) using a hydrothermal process, yielding a quantum of approximately 12.4%. These L-CDs exhibited excellent selectivity and sensitivity towards Hg2+ ions, with a limit of detection (LOD) of 0.23 nM and a wide linear range of 0-8 nM. This detection system may follow a dynamic quenching mechanism, characterized by fluorescent lifetime decay and zeta potential analysis. In addition, it was applied to detect Hg2+ ions in real water samples (coal water and industrial water), with recovery rates ranging from 98 to 102%, and relative standard deviations were 0.2-0.6%. Furthermore, the low cytotoxicity and small particle size of the L-CDs also make them suitable for use in antioxidant activity as well as HeLa cell imaging. Overall, this research represents a promising candidate in the field of environmental monitoring, food safety, and biomedical research.

This study aimed to develop a time-resolved fluoroimmunoassay (TRFIA) for the quantitative detection of soluble terminal complement complex (sC5b-9) and to evaluate the clinical significance of urinary sC5b-9 in patients with lupus nephritis (LN). The sC5b-9-TRFIA was established using a 96-well microplate coated with anti-sC5b-9 monoclonal antibody, anti-sC5b-9 polyclonal antibody, and Eu³⁺-labeled goat anti-rabbit IgG. Urinary sC5b-9 levels were determined in 42 patients with LN and 18 healthy controls to further assess its diagnostic potential in LN. The assay demonstrated a detection limit of 1.38 ng/mL and a linear measurement range of 6.25-1000 ng/mL. The intra-assay and inter-assay coefficients of variation ranged from 4.84% to 7.91% and from 7.06% to 9.11%, respectively, indicating good precision. The sC5b-9-TRFIA showed strong agreement with commercially available enzyme-linked immunosorbent assay (ELISA) kits within the same detection range (P < 0.0001). Urinary sC5b-9 concentrations were significantly elevated in LN patients (157.45 ± 127 ng/mL) compared with healthy controls (38.87 ± 30.11 ng/mL, P < 0.0001). In summary, a wide-range sC5b-9 TRFIA based on europium (Eu³⁺) chelate labeling was successfully developed, providing a sensitive and reliable method for assessing the clinical condition of LN.

A turn-off naphthalene-based Schiff base probe (E)-2-((2-hydroxy-4-sulfonaphthalen-1-yl) imino) methyl) benzoic acid (HSMB) was synthesized and used for the selective detection of Fe3+ ions in aqueous media. FTIR, elemental analysis and NMR was used for the characterization of probe. Excitation and emission bands at 346nm and 478nm shown by the probe were correlated with theoretical values of 227nm and 493nm respectively calculated by computational analysis. Time-Dependent Density Function Theory calculations revealed that intramolecular charge transfer was responsible for selective turn-off fluorescence behavior of the probe towards Fe3+ metal ions in water at neutral pH with limit of detection of 2.5µM. Association constant of 4 × 103 M-1 was determined through Benesi-Hildebrand equation and binding stoichiometry of metal-ligand complex was 1:1 in the Job's plot analysis. The probe was very selective and efficient for the detection of Fe3+ ions in the presence of various metal ions in aqueous media without the bar of maintaining pH. In comparison to other methods like colorimetry, atomic absorption spectrometry, ion-pair chromatography etc. the synthesized Schiff base fluorimetric probe exhibited lower detection limit making it a potential candidate for practical applications.

Single-, dual-, and multi-heteroatoms such as N, S, and B-doped carbon quantum dots (CQ-dots) were prepared to determine their dopant effects on anti-pathogenic activities. The CQ-dots were prepared using maleic acid (MA), poly(vinyl amine) (PVAm), cysteine (Cys), and boric acid (BA) as carbon, nitrogen, sulfur, and boron sources, respectively. In 345-415nm emission wavelength range, 45.9 ± 2.4% quantum yield for dual heteroatom-doped (N/B-doped) CQ-dots were attained. Antimicrobial studies revealed that N-doped CQ-dots have significant antimicrobial susceptibility to both bacteria and fungi. The zeta potential value of N-doped CQDs had -4.9mV was changed to -9.2 and -11.5mV upon N/S- and N/B-doping, respectively. N/B-doped CQ-dots afforded the highest antibacterial activity providing a 1.56mg/mL minimum inhibitory concentration (MIC) value against Escherichia coli, whereas N/S-doped CQ-dots had the highest antimicrobial activity against Staphylococcus aureus and Candida albicans yeast, 0.37mg/mL MIC values. The photodynamic antimicrobial studies of N-, N/S-, N/B-, and N/S/B-doped CQ-dots significantly eradicated the bacteria and fungus colony upon UV-A light exposure for 30min, with > 50% microbial colonial inhibitions. Both N and N/S-doped CQ-dots exhibit higher biofilm eradication/inhibition efficacy on Candida albicans biofilm, and all CQ-dots are biocompatible according to blood compatibility and cytotoxicity analysis at 1000μg/mL.

This work evaluates using synchronous fluorescence spectroscopy with chemometric modeling techniques, Partial Least Squares (PLS), and Artificial Neural Network (ANN), to monitor key biochemical parameters during Zika virus-like particle (Zika-VLP) production. The study aimed to predict concentrations of lactate (Lac), glutamine (Gln), glutamate (Glu), ammonium (NH4+), total protein (Tp), viable cell density (Xv), cell viability (Cv), and viral titer (VT) from offline synchronous fluorescence spectra at various wavelength differences (Δλ) captured throughout bioreactor assays. Biochemical parameters were initially monitored using standard methods. Both PLS and ANN models demonstrated good predictive capabilities for several parameters, with ANN generally outperforming PLS in accuracy and lower error rates. The study found that Δλ = 80nm spectra, both processed and raw, yielded the best results, although the optimal preprocessing method varied by parameter. The model's predictive accuracy was assessed using Mean Relative Error (MRE) in percentage, showing promising results, especially for parameters like glutamate (1.1%), glutamine (1.6%), ammonium (4.0%), and viral titer (5.8%) when ANN was used as a modeling technique. Transmission electron microscopy confirmed the successful production of Zika-VLP, with sizes consistent with previous reports. Synchronous fluorescence spectroscopy, coupled with appropriate spectral preprocessing and chemometric modeling, is a viable technique for monitoring multiple parameters during Zika-VLP production.

Peroxynitrite (ONOO-), a highly reactive nitrogen species with potent oxidative capacity, plays dual roles in cellular signaling and disease pathogenesis. To address the limitations of existing ONOO- probes-particularly poor aqueous solubility and inadequate emission wavelengths-we developed P30, a novel water-soluble fluorescent probe based on a rigid molecular scaffolding. P30 selectively detects ONOO- through azo-bond oxygenolysis, triggering rapid (< 10s), sensitive (LOD = 0.38 µM), and long-wavelength fluorescence emission (λem = 612nm). Crucially, P30 enables real-time visualization of both exogenous and endogenous ONOO- in live cells, demonstrating its utility for interrogating ONOO- dynamics in biological systems. These attributes position P30 as a robust tool for studying ONOO--associated pathophysiological processes.

Pepsin is a key proteolytic enzyme involved in the gastric digestion. Graphene oxide (GO) despite the promising biomedical applications, lacks consensus for its use in medicines. One of the leading causes in this respect is the limited understanding of its interaction with model proteins. In this background, the present study investigates the biophysical interaction of GO with pepsin using UV-Vis, Fluorescence, FT-IR spectroscopy, and in-silico modelling. UV-Vis spectra of pepsin revealed slight hypsochromic and hyperchromic shift in the presence of GO indicating alteration in pepsin's structure corroborated by fluorescence quenching study. Further analysis of fluorescence data shows a decrease in Stern-Volmer quenching constant, Ksv (order of 105 L g-1) decreases with increasing temperature that indicates static quenching which is essentially due to complexation. The complexation was further characterized in terms of association constant (non-covalent interactions) and the equivalent number of binding sites (close to one). Thermodynamic analysis suggested the binding interaction is essentially entropy driven. Synchronous fluorescence spectra suggested microenvironment changes for both the tryptophan and tyrosine residues in the binding sites. Detailed secondary structure study of pepsin (native and in presence of GO) using ATR-FTIR confirmed significant changes in the protein conformation (α-sheet, random coil, and β-helix) upon interaction with GO. Molecular docking suggested the involvement of H-bonding and π- π interactions within the GO-pepsin system with a binding score of -11.47kcal/mol. DLS study indicated concentration dependent increase in hydrodynamic diameter of pepsin in presence of GO. Finally, physiological activity of pepsin was found decreased (up to 54%) upon incubation with GO suggested change in its activity. This work provides valuable insights into the binding mechanism and interaction of GO with pepsin with potential implications for the development of an oral GO based formulations in the near future.

A novel perimidine derivative: 2-(isoquinolin-1-yl)-1H-perimidine (sensor 1) was synthesized via a facile, one-step reaction between DAN (1,8 diaminonaphthalene) and 2- quinolinecarboxaldehyde. The as-synthesised sensor 1 was found to be stable under a wide pH range of 2-12, and it behaved as a colorimetric as well as fluorescence turn-on sensor for Fe3+ with a response range varying from 0 to 200 µM. The fluorescence titration profile was used to calculate the binding constant as 1.3 × 104 M-1 and the LOD was as low as 7.4 nM. Additionally, the interference studies revealed the capability of 1.Fe3+ complex to sense Cu2+, which was accompanied by the fluorescence turn-off response. The binding constant and detection limit of 1.Fe3+ complex for Cu2+ were calculated to be 1.44 × 103 M and 1.13 × 10-7 M, respectively. The Fe3+ induced fluorescence enhancement at different concentrations was also recognized via smartphone, which could benefit in resource-limited areas and could be used as an alternative for complex instrumentation.