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A novel type of sandwich MOF was successfully synthesized on reduced graphene oxide (denoted as M@Pt@M-rGO) by an in situ synthesis method. The obtained M@Pt@M-rGO possesses excellent electrochemical properties. The surface morphology and structure of M@Pt@M-rGO were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), etc. By using M@Pt@M-rGO, a novel electrochemical sensor was constructed and successfully used for the simultaneous and sensitive detection of three isomers: hydroquinone (HQ), catechol (CT) and resorcinol (RS), with wider linear ranges of concentrations of 0.05–200 μM, 0.1–160 μM and 0.4–300 μM and lower detection limits of 0.015 μM, 0.032 μM and 0.133 μM (S/N = 3) for HQ, CT and RS, respectively. Besides, the proposed electrochemical sensor showed excellent anti-interference capability, high stability, good reproducibility, and satisfactory recovery for determination of isomers in river and lake water. [ABSTRACT FROM AUTHOR]

In this work, we propose a strategy for the fluorescence assay of histidine (His) and cysteine (Cys) by using lanthanide coordination polymer nanoparticles (Ln-CPN) as a fluorescent probe. The Ln-CPN were prepared by self-assembly of adenosine monophosphate (AMP) with Tb3+, i.e. AMP-Tb. The nonluminescent AMP-Tb could be efficiently sensitized by 5-sulfosalicylic acid (SSA). The fluorescence of AMP-Tb-SSA can be remarkably quenched by Cu2+, and that of the resulting Cu/SSA/AMP-Tb can be significantly enhanced by His and Cys. Thus, a specific fluorescence “turn-on” assay for His and Cys was developed by using Cu/SSA/AMP-Tb as a sensing platform. The enhanced fluorescence intensity was proportional to the His and Cys concentration in the range from 0.2 to 150 μM and 0.5 to 200 μM, respectively, with the detection limits of 70 nM and 100 nM. Additionally, taking advantage of a masking agent for His, the differentiation of His from Cys was achieved in our system. Furthermore, the protocol can also work well for analyzing His and Cys in practical plasma samples with recovery in the range of 100.3–104.1%. [ABSTRACT FROM AUTHOR]

A new and sensitive voltammetric sensor for palmatine, based on an electrochemically reduced l-methionine functionalized graphene oxide modified glassy carbon electrode (l-Met-ERGO/GCE), is reported. The electrochemical characteristics of palmatine at the proposed sensor were studied systematically and some dynamic parameters were calculated for the first time. A reasonable reaction mechanism for palmatine on the l-Met-ERGO/GCE electrode was proposed and discussed, and this could be a reference for the pharmacological action of palmatine in clinical study. Under optimized conditions, the peak current had a linear relationship with palmatine concentration in the range of 1 × 10−7 to 5 × 10−5 mol L−1 with a detection limit of 6 × 10−8 mol L−1. Additionally, the proposed method was also used to detect palmatine in human urine samples, medicinal tablets and the Chinese herb Fibraurea recisa Pierre with satisfactory results. [ABSTRACT FROM AUTHOR]