Multifunctional Au-Ag NCs for luminescence and colorimetric double signal sensing of HS and catalytic reduction of nitrophenol.

In this study, the N-Acetyl-l-Cysteine (NAC)-capped gold and silver bimetallic nanoclusters (NAC@Au-Ag NCs) was synthesized by reflux method. Due to the silver effect, the NAC@Au-Ag NCs exhibited strong photoluminescence at far-red/near-infrared regions and better catalytic performance than Au or Ag NCs. Upon addition of HS, the Au-Ag NCs exhibited obvious fluorescence quench and color changes through the generation of metal sulfides and a static quenching process. The Au-Ag NCs displayed a wide linear luminescence response for HS (18.5-217 μmol/L) with a detection limit of 0.269 μmol/L. Moreover, the visible color of Au-Ag NCs changed from white to brown-yellow along with increased HS, the corresponding RGB values also displayed good linearity with the concentration of HS (90.1-678 μmol/L). Notably, the fabrication of test strips provided a convenient and intuitive tool to screen the freshness of eggs by the color change of test strips. Au-Ag NCs could be used for living HeLa cells bioimaging and recognition of HS abnormalities. Furthermore, it can be used as a catalyst to reduction of nitrophenols (NPhs), specific included 2NP, 3NP and 4NP. The reaction was regarded as a pseudo-first-order kinetic reaction due to the presence of excess NaBH. At 298K, the catalytic rate constants(k) of 2NP, 3NP and 4NP were 0.1754 min, 0.1734 min and 0.2782 min, respectively. The NAC@Au-Ag NCs catalyst still showed good catalytic activity and reusability after five cycles. Therefore, this study developed a HS sensor for food samples and biological systems. And this nanocatalyst had great application potential for removed the nitrophenol pollutants in water.