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We report a room-temperature strategy for the synthesis of single-crystalline fluorescent graphene quantum dots (GQDs) via electron-beam irradiation. The precursor contained high-activity nitro groups is easy to fusion GQDs with the method. Under optimized conditions (0.02 g 1,3,6-trinitropyrene, radiation dose of 400 kGy and 10 ml 0.5 mol/L hydrazine hydrate), the GQDs exhibit highly efficient fluorescence at 475 nm with a quantum yield of 32%. The PL maximum is well corresponded with the excitation wavelength. Moreover, the single-exponential fluorescence lifetime (4.86 ns) exhibited the intrinsic PL characteristic. The pH stability in neutral and alkaline solution, solid solubility and storage time stability of GQDs are satisfactory. Their application as a safety fluorescent probe for cell imaging is demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fluorescent NTR probe NFP-NTR based on the benzo[ cd ]indol fluorophore was designed for nitroreductase imaging in living cells under hypoxia conditions. • The probe NFP-NTR showed excellent sensitive capability with calculated limit detection of 17 ng/mL. • The probe NFP-NTR displayed high selectivity towards NTR over other analytes. • The probe NFP-NTR was successfully employed as a desirable tool for cellular imaging of endogenous NTR in Hela cells at the condition of hypoxia. Nitroreductase (NTR) plays a vital part in the activation of drugs and the biodegradation of nitroaromatic compounds. With the enhanced expression level of NTR in hypoxic solid tumors, it has been widely used as one of the biomarkers to evaluate the degree of tumor hypoxia. In this work, we reported a benzoindole-based fluorescent probe NFP-NTR for nitroreductase detection. NFP-NTR can react with NTR specifically to cleave the p-nitrobenzyl ether bond when nicotinamide adenine dinucleotide (NADH) is present, showing significant fluorescence augment characteristics. Encouragingly, NFP-NTR exhibited excellent selectivity and satisfactory sensitivity, with a detection limit of 17 ng/mL. In addition, this probe has been successfully used to image live Hela cells under hypoxic conditions with low cytotoxicity, indicating that probe NFP-NTR has great potential to further elucidate more biological applications of NTR. [ABSTRACT FROM AUTHOR]

• A novel bifunctional fluorescent probe CBTA was developed. • CBTA showed high sensitivity and selectivity to HSO 3 − and N 2 H 4 in ultrafast time. • CBTA has low detection limits for bisulfite and hydrazine. • CBTA could visualize endogenous HSO 3 − in living cells. The probe CBTA is a novel bifunctional fluorescent probe that can detect bisulfite and hydrazine hydrate in a rational manner. And probe CBTA could specifically detect bisulfite and hydrazine hydrate among different analytes. Moreover, the response time of probe CBTA to SO 2 derivatives and hydrazine is extremely short, and the detection limits for bisulfite and hydrazine are as low as 5.6 nmol and 39 nmol. Cellular experiments also indicated that the probe CBTA was low in cytotoxicity and could be applied to cellular fluorescence imaging. Therefore, the probe CBTA could provide an efficient means for detecting SO 2 derivatives and hydrazine in vitro. [ABSTRACT FROM AUTHOR]