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Hollow cross-linked fluorescent carbon nitride nanoparticles (CNNPs) were fabricated via a facile one-pot solvothermal process. The obtained CNNPs were characterized by multiple analytical techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The excitation-dependent fluorescence emission spectra showed significant differences for the CNNPs derived from various proportions of citric acid monohydrate and urea. The fluorescence quantum yield of the obtained CNNPs could reach 31%. The CNNPs exhibited good fluorescence quenching selectivity to mercuric ions. Concentration experiments showed that there existed two parts of linear relationship between fluorescence intensity and concentration of Hg(2+) ions in the range of 0.1-8 and 8-32 μM. The limit of detection (LOD) was estimated to be 0.094 μM. This method can be applied to the detection of Hg(2+) ions in tap water samples., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The electrochemical behaviors of acetaminophen (ACOP) on a graphene-chitosan (GR-CS) nanocomposite modified glassy carbon electrode (GCE) were investigated by cyclic voltammetry (CV), chronocoulometry (CC) and differential pulse voltammetry (DPV). Electrochemical characterization showed that the GR-CS nanocomposite had excellent electrocatalytic activity and surface area effect. As compared with bare GCE, the redox signal of ACOP on GR-CS/GCE was greatly enhanced. The values of electron transfer rate constant (ks), diffusion coefficient (D) and the surface adsorption amount (Γ(*)) of ACOP on GR-CS/GCE were determined to be 0.25s(-1), 3.61×10(-5) cm(2) s(-1) and 1.09×10(-9) mol cm(-2), respectively. Additionally, a 2e(-)/2H(+) electrochemical reaction mechanism of ACOP was deduced based on the acidity experiment. Under the optimized conditions, the ACOP could be quantified in the range from 1.0×10(-6) to 1.0×10(-4) M with a low detection limit of 3.0×10(-7) M based on 3S/N. The interference and recovery experiments further showed that the proposed method is acceptable for the determination of ACOP in real pharmaceutical preparations., (Copyright © 2012 Elsevier B.V. All rights reserved.)