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A hydrothermal synthetic approach is developed for the preparation of graphitic carbon nitride quantum dots (g-C 3 N 4 QDs) from human urine. The reported synthetic method is green, simple, low-cost, less time-consuming, and can be used for the large-scale production of the g-C 3 N 4 QDs. The as-prepared g-C 3 N 4 QDs possess a high quantum yield of 15.7% by using quinine sulfate as a reference, and display excitation-wavelength dependent fluorescent emission. In addition, the g-C 3 N 4 QDs exhibit high photostability, low cytotoxicity. and are successfully used as fluorescent probes for cell multicolor imaging. It is believed that the valuable nanomaterials, g-C 3 N 4 QDs, which are transformed from the human bodily wastes, are promising in diverse chemical applications. [ABSTRACT FROM AUTHOR]

Development of thiol-specific fluorescent probes with selectivity in different thiol compounds is more practical and significant than those without that capacity. In this work, a new quinoline-derived fluorophore, hydroxyl-substituted quinoline-benzo[ d ]oxazole 6 with high fluorescence quantum yield is synthesized and esterified with acrylic acid to afford two fluorescent probes, BQA-1 and BQA-2 for selectively discriminating Cys from Hcys/GSH based on conjugate addition-cyclization mechanism. BQA-1 exhibits a large ratiometric fluorescence response toward Cys in aqueous pH 7.4 solution with big emission peak-shifting from 383 nm to 518 nm, over 130 nm. The detection limit is determined to be as low as 0.59 μM. In contrast to BQA-1 , BQA-2 whose acrylic ester moiety is further modified with pyridine group, displays a turn-on fluorescence response to Cys with detection limit of 0.98 μM. Both BQA-1 and BQA-2 have relatively weak response to another two biothiols, Hcys and GSH and nearly no response to other nucleophiles. Furthermore, the potential application for the detection of biothiols in living cells has been demonstrated by cell imaging experiment. [ABSTRACT FROM AUTHOR]

In this paper, silver nanoclusters (AgNCs) were synthesized by one facile, low-cost and green method with histidine acting as the stabilizer and ascorbic acid performing as reducing agent. AgNCs displayed excellent fluorescence property and good biocompatibility and were further functionalized by β-cyclodextrin (CD-AgNCs) for the highly sensitive detection of alkaline phosphatase (ALP) activity. ALP catalyzed the dephosphorylation of p -nitrophenylphosphate (NPP) to produce p -nitrophenol (NP), and NP can effectively quench the fluorescence of CD-AgNCs via the inner filter effect (IFE) due to the UV–vis absorption spectrum of NP had considerable overlap with the excitation spectrum of CD-AgNCs. Benefiting from the IFE and the host-guest interaction between CD and NP, this CD-AgNCs based system for ALP activity analysis displayed a good linear range of 0.02–10.0 U L−1 and the detection limit as low as 0.0046 U L−1. In addition, this proposed strategy also showed satisfactory performance for ALP analysis in human serum samples and bioimaging of intracellular ALP in living cells, indicating the great application prospect of this system for ALP activity analysis in medical related researches. AgNCs were facilely synthesized and further functionalized by β-cyclodextrin and performed as excellent fluorescent probes for ultrasensitive analysis of ALP and bioimaging intracellular ALP in living cells. Image 1 • AgNCs were synthesized by a one-step method and further modified with β-cyclodextrin. • Results indicated AgNCs displayed good fluorescence property and biocompatibility. • CD-AgNCs were applied as excellent fluorescent probes for ALP analysis. • Integrating IFE and host-guest recognition, ultrasensitive ALP sensing was conducted. • The approach was applied for ALP sensing in human serum and bioimaging in cells. [ABSTRACT FROM AUTHOR]