Tailored Assembly of Electronically Engineered Gold Nanoclusters for On-Chip Visual Detection of Nitrogen-Rich Heterocyclic Explosives

Rapid and reliable detection of emerging nitrogen-rich heterocyclic explosives is essential for security and environmental protection; however, their structural diversity hampers efficient detection. Here, we report a molecularly engineered optical platform that integrates donor-substituted terpyridine (D-TPY) fluorophores with red-emissive gold nanoclusters (AuNCs) through Zn²⁺ coordination, enabling precise modulation of electronic coupling and their recognition behavior. A series of D-TPY fluorophores with tunable electron-donating properties is assembled with Zn²⁺-bridged AuNCs to afford probes with adjustable photophysical properties. Among them, Probe 1 exhibits highly distinct optical responses toward two nitrogen-rich heterocyclic explosives, 3-nitro-1,2,4-triazol-5-one (NTO) and 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX). Upon exposure to NTO, Zn²⁺ is competitively displaced from the TPY coordination site, leading to a characteristic ratiometric fluorescence response. In contrast, interaction with PYX results in the formation of a ternary complex that effectively quenches fluorescence and induces an obvious colorimetric change visible to the naked eye. Further incorporation of Probe 1 into poly(vinyl alcohol) sponge yielded robust sensing chips capable of highly selective, interference-resistant visual discrimination of NTO and PYX. This study provides a versatile design framework for precisely tailoring nanoprobe-based assemblies to achieve controllable optical response, offering new opportunities for on-chip detection of explosives and other analytes.