Confinement of gold nanoclusters on hydroxy double salt for versatile fluorescent sensing of bio-enzymes

Abstract

Fluorescent gold nanoclusters (AuNCs) have generated significant research interest because of their fascinating physicochemical properties. However, their biosensing applications are limited by the relatively low quantum yield (QY). Herein, a simple confinement effect based on AuNCs as guest molecules and Zn-containing hydroxy double salt (HDS) as host material (AuNCs@HDS) was used to significantly improve the fluorescence properties of AuNCs. The QY increased from 1.24 % to 22.80 %, and the time-tedious preparation or purification procedures were avoided. Further, the validated excellent fluorescence properties of AuNCs enabled the construction of a versatile fluorescent sensing strategy for bio-enzymes for the first time. The p-nitrophenol (pNP), a product of many bio-enzymes-catalyzed hydrolyzes of pNP-substrate, can effectively quench the fluorescence of AuNCs@HDS through an inner filter effect (IFE) process. Therefore, the AuNCs@HDS successfully detected several enzymatic disease biomarkers with robust analysis capabilities by varying the pNP-substrate, including alkaline phosphatase (ALP), β-glucosidase (β-GLU) and β-galactosidase (β-GAL). This study will inspire the design of highly fluorescent AuNCs as tools for biosensing.