A fluorescent probe for the monitoring of H 2 S levels in living cells and organisms is highly desirable. In this regard, nearinfrared (NIR) fluorescent probes have emerged as a promising tool. NIR-I and NIR-II probes have many significant advantages; for instance, NIR light penetrates deeper into tissue than light at visible wavelengths, and it causes less photodamage during biosample analysis and less autofluorescence, enabling higher signal-to-background ratios. Therefore, it is expected that fluorescent probes having emission in the NIR region are more suitable for in vivo imaging. Consequently, a considerable increase in reports of new H 2 Sresponsive NIR fluorescent probes appeared in the literature. This review highlights the advances made in developing new NIR fluorescent probes aimed at the sensitive and selective detection of H 2 S in biological samples. Their applications in real-time monitoring of H 2 S in cells and in vivo for bioimaging of living cells/animals are emphasized. The selection of suitable dyes for designing NIR fluorescent probes, along with the principles and mechanisms involved for the sensing of H 2 S in the NIR region, are described. The discussions are focused on small-molecule and nanomaterialsbased NIR probes.

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A two-step viable synthetic approach for quick and energy-efficient acid-based charring is described here to fabricate self-passivated fluorescent water-soluble CD (wsCD) from sustainable microcrystalline cellulose (MCC) materials. The aqueous solution of wsCD exhibits blue emission under UV-light illumination and shows a fluorescence quantum yield of ∼6%. The wsCD are used here for the selective sensing of ofloxacin (OFLX) from among the four tested antibiotics of the fluoroquinolone class, namely, ciprofloxacin (CPLX), ofloxacin (OFLX), levofloxacin (LVLX), and moxifloxacin (MXLX) based on the simpler fluorescence quenching experiment with a detection limit of ∼0.025 ppm. The plausible mechanism for the selective sensing of OFLX has been proposed based on a detailed analysis of absorbance and time-resolved photoluminescence spectroscopy which indicates the involvement of the inner-filter effect (IFE). Antimicrobial studies of wsCD were conducted on two bacterial strains (Escherichia coli and Staphylococcus aureus) and two fungal strains (Aspergillus niger and Penicillium chrysogenum), where wsCD did not show any toxic effects up to the concentration of 1 mg/mL, hence supporting their biocompatible behavior. Further, an antibiosis study involving the combination of the antibiotic and antifungal agents with wsCD against the growth of the same bacterial and fungal strains was conducted, where wsCD showed mild antifungal activity.

Moisture detection in organic solvents and materials by using chemical sensors represent the latest research area in analytical chemistry. In this paper, we report a new fluorescent chemical sensor for the sensitive detection of trace amount of water in Tetrahydrofuran(THF), acetone and acetonitrile. The new probe L.Fe(III) complex consists of the fluorescent reporter dansyl dye attached with Fe(III) ion. Ligand L, and probe L.Fe(III) exhibits solvatochromism by intramolecular charge transfer (ICT) due to the donor‐acceptor properties of the dansyl compound. Probe L.Fe(III) is a non‐fluorescent compound and it becomes highly fluorescent in the presence of trace amount of water in THF, acetone and acetonitrile. The probe shows highly sensitive towards the water in THF with a limit of detection (LOD) as low as 0.0003 weight(wt) %. 1H‐NMR, ESI‐MS and fluorescence lifetime studies established that displacement of metal from the probe is responsible for fluorescent enhancement. Further, for the first time probe L.Fe(III) has been explored as a fluorescence indicator for the qualitative and quantitative detection of trace‐level of water content in various edible oilseeds such as groundnut, mustard, sunflower, sesame and almond.