Surface-Confined Sequential Synthesis of Metal Oxide Nanoarrays with Tunable Constitution and Precise Doping for Chemiresistive Gas Sensing

Fine synthesis of oriented metal oxide nanoarrays with tailored chemical compositions is highly desirable for the development of high-performance sensing nanodevices. However, conventional methods normally struggle to diversify the composition of metal oxide nanoarrays. Herein, a micellar brush-directed surface-confined sequential synthesis method is presented for the controlled fabrication of well-aligned metal oxide nanoarrays with designable constitutions via orderly decoupling the nucleation and growth process. The micellar brush provides an orient-confined space for promoting the nucleation-like process of various metal precursors (e.g., polyoxometalates and organometallic alcoholates), followed by programmable calcination to in situ convert into upright metal oxide nanoarrays, including WO3, MoO3, TiO2, Ta2O5, Nb2O5, and ZrO2 nanoarrays. Furthermore, the pyridine-rich micellar brush shells also readily bond with desired metal ions to enable the uniform doping of metal atoms into the metal oxide nanoarrays during the pyrolysis process. This endows metal oxide nanoarrays with tailored single-atom doping and abundant oxygen vacancies. Notably, the as-fabricated Cu-WO3 nanoarray exhibits competent H2S detection ability with high response (Ra/Rg = 168 for 10 ppm of H2S) and fast response-recovery (2.2/143 s) dynamics. Theoretical calculations further identify the presence of synergistic effects between single-atom Cu and oxygen vacancies, in which single atom Cu sites dominate H2S adsorption and oxygen vacancies facilitate oxygen activation. This work offers guidelines for the rational design of advanced metal oxide nanoarrays toward high-performance gas-sensing devices.