A Regiospecific\nCo-Assembly Method to Functionalize\nOrdered Mesoporous Metal Oxides with Customizable Noble Metal Nanocrystals

An efficient regiospecific co-assembly (RSCA) strategy\nis developed\nfor general synthesis of mesoporous metal oxides with pore walls precisely\ndecorated by highly dispersed noble metal nanocrystals with customized\nparameters (diameter and composition). It features the rational utilization\nof the specific interactions between hydrophilic molecular precursors,\nhydrophobic noble metal nanocrystals, and amphiphilic block copolymers,\nto achieve regiospecific co-assembly as confirmed by molecular dynamics\nsimulations. Through this RSCA strategy, we achieved a controllable\nsynthesis of a variety of functional mesoporous metal oxide composites\n(e.g., WO<sub>3</sub>, ZrO<sub>2</sub>, TiO<sub>2</sub>) with in-pore\nwalls precisely decorated by various noble metal nanocrystals of tailored\ncomponents (Au, Ag, Pt, Pd and their nanoalloys) and sizes (3.0–8.5\nnm). As an example, the obtained mesoporous 0.5-Ag/WO<sub>3</sub> material\nhas a highly interconnected mesoporous structure and uniform 6.5 nm\nAg nanocrystals confined in the mesopores, showing superior NO sensing\nperformances with high sensitivity, good selectivity, and stability\nat low working temperature (127 °C). <i>In situ</i> spectroscopy study indicates that the NO sensing process involves\na unique gas–solid reaction, where NO molecules are converted\ninto chemisorbed NO<sub><i>x</i></sub> species over the\nsensitive materials, inducing a remarkable change of resistance and\noutputting a dramatic response signal.