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Depression is closely related to overactivation of N-methyl- D -aspartic acid (NMDA) receptors, and Zn2+ is a vital NMDA receptor modulator involved in the pathophysiological and physiological processes of depression. Therefore, quantitative and real-time detection of Zn2+ is very important for understanding the pathogenesis of depression. In this work, a near-infrared (NIR) fluorescent probe ISO-DPA was designed and synthesized for Zn2+ detection with a large Stokes shift (185 nm), high quantum yield (up to 44%), high sensitivity (LOD = 0.106 μM) and good pH stability. The probe showed rapid response within 10 s, accompanied by a distinct fluorescence change from faint to bright pink with the fluorescence intensity increasing 4.5-fold. Moreover, the sensing mechanism of ISO-DPA towards Zn2+ was supported by MALDI-TOF-MS and Job's plot. The probe ISO-DPA could detect instantaneous variation of exogenous and endogenous Zn2+ in PC12 cells. The bioimaging results reveal the increase of the endogenous Zn2+ concentration in PC12 cells under the oxidative stress induced by glutamate and confirm that overactivation of NMDA receptors results in an increase of the Zn2+ level. All the results proved that ISO-DPA is an excellent probe for detecting Zn2+ in solution and living cells and could help us better understand Zn2+ associated pathogenesis of depression. [ABSTRACT FROM AUTHOR]

Graphical abstract A novel near-infrared fluorescent probe for colorimetric and sequential detection of Cu2+/S2− was designed and developed. Highlights • A new near-infrared fluorescent probe for sequential and reversible detection of Cu2+ and S2− was constructed. • Probe exhibited good selectivity, lower detection limit, and a large Stokes shift of 234 nm. • The proposed sensing mechanism was confirmed by DFT calculations and contrastive compound research. • The probe was successfully applied to detect Cu2+ in real water samples and strip papers. Abstract Copper ions (Cu2+) and sulfide (S2−) are important markers in many physiologies and pathological processes. In this work, a new near-infrared fluorescent probe 1 for colorimetric and sequential detection of Cu2+/S2− was designed and developed. The probe showed a rapid (less than 1 min), highly selective and sensitive response toward copper ions. Notably, the probe could also be applied to detect S2− through reversible formation-separation of complex 1 -Cu2+ and CuS with a large Stokes shift of 234 nm. The detection limit for Cu2+ and S2− was found to be 1.8 × 10-8 M and 1.5 × 10-8 M, respectively. Furthermore, the binding stoichiometry between 1 and Cu2+ was found to be 1:1, the binding mode was also demonstrated using density functional theory (DFT) calculations and contrastive compound research. In addition, the probe was successfully applied in real water samples assay for the detection of Cu2+, and the strip papers experiments also showed that probe 1 can be used to detect Cu2+ and S2−. [ABSTRACT FROM AUTHOR]

The antibiotic amoxicillin (AMX) was detected sensitively by a novel fluorescence probes composed with boron-doped carbon quantum dots (B-CQDs). B-CQDs with a 5:1 molar ratio of C atom versus B atom can be synthesized first by mixing citric acid with boric acid as a B source on suitable hydropyrolysis condition. The AMX in an aqueous solution was detected via fluorometry. Results showed that the as-prepared B-CQDs had nattier blue fluorescence, a narrow diameter range, a mean particle size of 2.3 nm, a multigraphite phase structure, and a quantum yield of 30.85%. The B-CQDs as probes can sensitively detect AMX in aqueous solution, and the fluorescence signal of the B-CQDs-AMX system was strengthened linearly with the increase in AMX concentration when in the antibiotic concentration range of 1.43–429.12 μmol·L−1 with limit of detection of 0.825 μmol·L−1. B-CQDs detected AMX mechanism as follows: the probes can be combined with antibiotic via primary hydrogen bond between them, and their combining abilities were enhanced by increasing the temperature of this sensing system in the range of 288–313 K. Unlabelled Image • Boric acid were introduced to prepare boron doped CQDs. • The fluorescence property and quantum yield of B-CQDs were more preferable than CQDs. • AMX in aqueous solutions were detected by B-CQDs based on the fluorescence enhancement. • The mechanism of AMX detected by B-CQDs was discussed in detail. [ABSTRACT FROM AUTHOR]

• A novel N-CQDs were prepared by facile solid-heat method using glycine and urea. • The N-CQDs possessed a relatively high fluorescence QY (21.04 %). • The N-CQDs exhibited very high sensitivity and selectivity to dopamine. • This sensor successfully used for dopamine detection in human serum and rat serum. Herein, a novel nitrogen-doped carbon quantum dots (N-CQDs) with bright blue fluorescence were prepared using glycine and urea by a facile solid-heat method. The prepared N-CQDs had a relatively high quantum yield (QY = 21.04 %), excellent photobleaching resistance, acid and alkali resistance. Moreover, it was used as fluorescent probe for the detection of dopamine (DA) with high selectivity and a low limit of detection (LOD = 0.0972 μM). Additionally, this fluorescent probe was successfully used to the determination of DA in human serum and rat serum with satisfactory recoveries (98.24 %–107.86 %), indicating this probe is was a promising biomolecular sensor for quantitation of DA in serum. [ABSTRACT FROM AUTHOR]

Herein, a water soluble AgInS 2 quantum dots (AIS QDs) with high sensitive and selective for dopamine (DA) were prepared through a clean and facile reflux method with the mercapto propionic acid (MPA) and polyethyleneimine (PEI) used as the co-modifiers. The fluorescence quench of as-fabricated AIS QDs displayed an excellent selectivity and sensitivity to the DA and they showed a good linear relationship with the low detection limit (2.84 nm) in the range of 0.5–300 μmol/L. The mechanism of fluorescence quench may attributed to the photoinduced electrons migrated from AIS QDs to dopamine quinone, which originated from the oxidization of DA by ambient O 2. Our work shows a promising prospect of designing and preparing AIS QDs used as the fluorescence sensors for DA detection. Image 1 • Water soluble AIS QDs were prepared via a facile hydrothermal method. • MPA and PEI used as the co-modifiers to synthesize the AIS QDs. • AIS QDs displayed high sensitive and selective for dopamine (DA). • The detect limit of DA as low as 2.84 nM based on AIS QDs fluorescence probe. [ABSTRACT FROM AUTHOR]