A one-step microwave-assisted method was used for the synthesis of silver nanoparticles, and the corresponding nature and structure of silver nanoparticles were characterized by UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Raman scattering activities of silver nanoparticles with different reaction time were explored using rhodamine 6G (R6G) as a probe molecule. The results show that the intensity of surface enhancement Raman scattering (SERS) signals could be increased by silver nanoparticles. And then we made a comparison on SERS spectra of R6G studied silver nanoparticles to investigate the effect of surface enhancement Raman. Meanwhile, we studied the mechanism in the process of enhancement by silver nanoparticles.

Cu nanoclusters (CuNCs) capped by tannic acid (TA) (CuNCs@TA) can be used as a highly sensitive fluorescent probe for Cr(VI) detection. Therefore, a fluorescence detection method for Cr(VI) can be established according to the fluorescence quenching of CuNCs@TA that is caused immediately after the addition of Cr(VI). The fluorescence quenching efficiency of CuNCs@TA was linearly correlated with Cr(VI) concentration within the range 0.03–60 μM, and the detection limit for Cr(VI) was 5 nM. This method was demonstrated to be suitable for detecting Cr(VI) in actual water samples. We found that sodium thiosulfate (ST) can redox with Cr(VI) and therefore restore the fluorescence of CuNCs@TA. The mechanism of CuNCs@TA fluorescence quenching and enhancement by Cr(VI) and ST was investigated in detail. The ‘turn‐on’ fluorescent sensor is of practical significance and has broad application prospects.

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