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Ferric ion (Fe3+) serves as an essential and indispensable inorganic element in various biological process. Excess Fe3+ is harmful for biological systems and human health. Herein, highly sensitive carbon quantum dots (Fe-CQDs) for ferric ions were synthesized by a high-efficiency, one-step hydrothermal route utilizing L-arginine and citric acid. The prepared Fe-CQDs exhibited good water solubility, high photostability, and bright blue florescence with relatively high quantum yields (QYs) over 21.33% and a Stokes shift exceeding 100 nm. The functionalized Fe-CQDs offer rapid, sensitive, and selective recognition of Fe3+ with a linear relationship from 0.6 to 80 μM and a low detection limit of 0.2 μM. Moreover, the synthesized Fe-CQDs illustrated strong anti-interference properties in samples and buffer solutions. The developed sensor demonstrated high biocompatibility and was successfully applied for intracellular Fe3+ determination in SHSY5Y and HT22 cells, illustrating excellent imaging application. The present work provides a promising platform for the early clinical diagnosis of Fe3+-associated diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe EDPH specializes in the detection of H 2 S with high selectivity, high sensitivity and good detection limits. • The probe EDPH has been shown to have applications in intracellular fluorescence imaging. • Purine-based fluorescent probes for the detection of H 2 S are a new direction. Hydrogen sulfide (H 2 S) is a gas with a toxic odor that plays an irreplaceable role in physiological activities within the mammalian body. Therefore, it is important to do the distribution and quantitative detection of H 2 S in mammalian cells. In this paper, a fluorescence probe (EDPH) based on purine scaffold was designed and synthesized with high sensitivity and good selectivity. H 2 S induced ether bond breakage in EDPH , resulting in a significant redshift of the absorption band (from 370 nm to 500 nm) with a Stokes shift of 130 nm. After the addition of H 2 S, the fluorescence intensity of EDPH showed a good linear correlation with the concentration of H 2 S, which enabled the quantitative detection of H 2 S with a low limit of detection (41 nM). Finally, the EDPH was applied to the cellular Hele, and the probe has good cellularity imaging capability for the detection of H 2 S in living systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • An "off–on" long-wavelength fluorescent probe is synthesized for Cys detection. • The probe has a large Stokes shift (211 nm) and reacted with Cys specifically. • The probe can monitor Cys fluctuations caused by redox imbalance in HepG2 cells. • The probe can be used for fluorescence imaging in cells and mice. In this research, an "off–on" long-wavelength fluorescent probe (DCMN-Cl) based on (E)-2-(3-(2-(6-hydroxynaphthalen-2-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (DCMN) is designed and synthesized for cysteine (Cys) detection. DCMN-Cl exhibits a large Stokes shift (211 nm) and shows rapid response and high specificity to Cys. The fluorescence initensity at 635 nm reveals a good linear relationship with Cys concentration in the 0 to 50 μM range, and the detection limit is as low as 159 nM. The probe is also used for fluorescence imaging of Cys in cells and mice. Moreover, the probe provided visual evidence of Cu2+ and curcumin-induced intracellular Cys fluctuations. [ABSTRACT FROM AUTHOR]