Chitosan/SiO

Metal nanoclusters have emerged as promising fluorescence nanomaterials, yet their practical sensing applications remain constrained by limited stability and suboptimal luminescence efficiency. We report a strategically designed nanocomposite, chitosan/silica-encapsulated gold nanoclusters (Au NCs/CSNPs), which integrates three functional components into the fluorescence sensing platform. Unlike conventional encapsulation strategies that merely serve as protective shells, our chitosan-functionalized silica matrix achieves multiple synergistic functions, where rigid confinement enhances quantum yield and photostability, chitosan-induced improvement analyte accessibility, and the tailored composite microenvironment enables analyte-specific response modulation. Remarkably, Au NCs/CSNPs exhibit opposite fluorescence responses toward two distinct contaminants, with enhancement for 2-nitroaniline (2-NA) and quenching for fluazinam (Flu), enabling selective detection with low limits of detection of 52.2 nM for 2-NA and 45.7 nM for Flu. Mechanistic studies reveal that this dual-response behavior originates from distinct pathways including excited-state rigidification for 2-NA versus static quenching coupled with the inner filter effect for Flu. The sensor demonstrates excellent selectivity and practical applicability in environmental and food matrices. This work establishes a new paradigm for nanocluster-based sensors where the encapsulating matrix is not merely protective but functionally integrated to achieve tunable multi-analyte sensing capabilities.