Engineering Mesoporous Composite Nanospheres With Metal Core and Metal Oxide Shell for Plasmonic Promoted Gas Sensing

Nanoengineering of core-shell nanostructures integrating plasmonic metal cores and mesoporous semiconducting metal oxide (SMO) shells hold significant promise across catalysis, chemical sensing, diagnosis, micro-nano robots, and smart optics. However, their practical implementation is hindered by synthetic challenges such as poorly controlled hydrolysis kinetics of shell precursors and excessively high surface energy of core seeds. Herein, a versatile sequential active colloidal interfacial assembly strategy is developed to construct a library of uniform and core-shell nanospheres featuring mesoporous SMO (e.g., SnO₂) shells precisely coated on functional nanocores (e.g., Au NPs). As a representative core-shell material, the as-synthesized Au@mSnO₂ nanospheres combine localized surface plasmon resonance (LSPR) with a mesoporous catalytic matrix, thereby enabling excellent photoresponsive properties that are particularly favorable for catalysis and chemical sensing. The Au@mSnO₂ nanospheres are used as a catalytic sensing layer matrix for fabricating custom MEMS-based sensing nanodevices that can couple with micro-LED to serve as chemiresistive sensors for gas detection. The as-fabricated sensors exhibit 6-fold enhancement of sensitivity toward low concentration NO₂ at room temperature under low-power green light illumination. Mechanistic investigations systematically elucidate the LSPR-induced charge carrier dynamics, revealing that the superior sensitivity originates from ultrafast hot-electron injection, which accelerates surface catalytic activation and target gas redox conversion. This work presents a rational paradigm for precisely engineering multifunctional core-shell structures with spatially separated components tailored heterogeneous interfaces, opening new avenues for intelligent sensing and nanophotocatalysis, and so forth.