A Straightforward Solvent-Pair-Enabled Multicomponent Coassembly Approach toward Noble-Metal-Nanoparticle-Decorated Mesoporous Tungsten Oxide for Trace Ammonia Sensing
The straightforward synthesis of noble-metal-nanoparticle-decorated ordered mesoporous transition metal oxides remains a great challenge due to the difficulty of balancing the interactions between precursors and templates. Herein, a solvent-pair-enabled multicomponent coassembly (SPEMC) strategy is developed for straightforward synthesis of noble-metal-nanoparticle-decorated nitrogen-doped ordered mesoporous tungsten oxide (abbreviated as NM/N-mWO 3 , NM = Pt, Rh, Pd). The amphiphilic poly(ethylene oxide)- block -polystyrene (PEO- b -PS) copolymers coassemble with ammonium metatungstate (AMT) clusters and different kinds of hydrophilic noble metal precursors without phase separation. SPEMC synthesis requires no direct interaction between PEO- b -PS and AMT, thus the assembly equilibriums between noble metal precursors and PEO- b -PS can be readily controlled. The obtained NM/N-mWO 3 nanocomposites possess ordered mesopores, abundant oxygen vacancies, and metal–metal oxide interfaces. As a result, the Pt/N-mWO 3 sensors exhibit superior ammonia sensing performances with high sensitivity, an ultralow limit of detection (51.2 ppb), good selectivity, and long-term stability. Spectroscopic analysis reveals that ammonia is oxidized stepwise to NO, NO 2 − , and NO 3 − during the sensing process. Moreover, a portable wireless module based on Pt/N-mWO 3 sensor can recognize ppm-level concentration of ammonia, which lays a solid foundation for its application in various fields.
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