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Deoxyribonucleic acid (DNA) stabilized silver nanoclusters were synthesized and showed strong excitation at 724 nm and fluorescence emission at 768 nm. Upon the addition of mercury(II), the fluorescence of the DNA silver nanoclusters was quenched. The use of DNA silver nanoclusters as fluorescent sensors for mercury(II) was investigated in buffered media. A linear dynamic range from 1.90 × 10−9 M to 2.4 × 10−8 M was observed for mercury (II) with a correlation coefficient of 0.9977 and a limit of detection of 1.90 × 10−9 M. Excellent selectivity toward mercury(II) was observed against a variety of metal ions. The results demonstrate that silver nanoclusters have potential application for the determination of mercury (II). [ABSTRACT FROM AUTHOR]

CoS 2 nanoparticles (NPs) have shown promise as potential peroxidase (POD)-like catalysts, but the catalytic molecular mechanisms are largely unknown. Moreover, no study has adequately explored the influence of O-doping induced by the inevitable oxidation of CoS 2 on their POD-like activity. Here, O-doped CoS 2 NPs were prepared by a one-step method, and their intrinsic POD-like catalytic mechanism was investigated with a combined experimental and theoretical approach. The hydroxyl radical (˙OH) and the superoxide radical (O 2 ˙ - ) have been found to play significant roles in the POD-like activity, and ˙OH is the major radical. The O-doping could reduce the transition-state energy barrier of H 2 O 2 dissociation, thus promoting the decomposition of H 2 O 2 to ˙OH and inducing the formation of O 2 ˙ - . Therefore, O-doping is an effective method for enhancing the catalytic activity of CoS 2 NPs. Furthermore, due to the excellent oxidation property of ˙OH and O 2 ˙ - , this nanozyme exhibited efficient catalytic activity towards the degradation of organic dyes with H 2 O 2 . This manuscript provides a new inspiration for designing more promising anion-defective transition-metal sulfide nanozymes for different applications.

Objective: To isolate and characterize bacteria that can be used todevelop microbial biosensor for methanol (MeOH) determination., Methods: We used selective medium and streak plate to isolate bacteria. Morphological, physiological characteristics and 16S rDNA sequence analysis were used to identify the strain. An MeOH biosensor was then developed by immobilizing M211 along with dissolved oxygen (O2) sensor., Result: An MeOH utilizing bacterium was isolated from biogas-producing tank using methanol as the sole carbon source, and identified as Methylobacteriumorganophilium. Decrease of O2 concentration is linearly related to the MeOH concentration in the range from 0.02% to 1%, with the MeOH detection limit of 0.27 mg/L. The response time of the biosensor is within 20 min. Furthermore, the result of interference test and the detection of methanol sample are both satisfactory., Conclusion: Good results are obtained in interference test and the detection of methanol sample. The proposed method seems very attractive in monitoring methanol.