Synergistic biomimetic enzyme catalysis and photoluminescence enhancement-based ratiometric technique for trace-level detection of phosphate.

The accurate determination of phosphate (Pi) content in dairy products is essential for safeguarding consumer health and maintaining product quality standards. Herein, a sensing platform that integrates synergistic biomimetic enzyme catalysis with photoluminescence (PL) enhancement was developed for ratiometric detection of trace Pi in dairy products. First, a novel Ce-doped ZnO nanoflower (CeZnO) integrating hydrolase (HYD)-like nanozyme activity with a PL confinement effect was designed. Through facile self-assembly, gold nanocluster (AuNC) was confined onto CeZnO to form a composite (ACZO) to enhance the PL of AuNC. The ACZO material retained the phosphatase-like activity of CeZnO, enabling the hydrolysis of 4-methylumbelliferyl phosphate to yield a blue emission at 456 nm. The introduction of Pi resulted in the suppression of the fluorescence generated by ACZO's catalytic activity. Therefore, by leveraging the differential response between the enzymatic hydrolysis product (456 nm) and the stable internal reference signal from AuNC (600 nm), ratiometric Pi detection was achieved. Besides, successful application in determining total Pi in dairy products demonstrated high sensitivity and reliability. By integrating both catalytic and PL enhancement functions into a single platform, this work pioneers a novel strategy for the ratiometric PL detection of Pi with a low LOD of 129.7 nM. It thereby breaks from conventional single-function paradigms, establishing a versatile platform for food safety monitoring and a new pathway for designing multifunctional nanozyme composites.