Sub-10 nm S-Doped In₂O₃ Cubes Prepared via a Protein Hydrogel Space-Confined Strategy for ppb-Level Xylene Detection with Enhanced Electron Transfer Capability

The properties of xylene-sensing materials are currently limited by size effects and electronic orbital configurations. This work introduces a synthesis strategy utilizing the unique structural characteristics and physicochemical properties of protein hydrogels to create spatially confined domains. Uniformly dispersed sub-10 nm S-doped In₂O₃ cubes were successfully prepared, which are the smallest known In₂O₃ cubes. These materials boast an extensive specific surface area and a high concentration of oxygen vacancies, achieving an unprecedented xylene detection limit as low as 5 ppb. It was shown that the space-confined domain strategy can modulate the electronic orbitals of the material through size control and nonmetallic doping and enhance the adsorption capacity and electron transfer ability of the material. This work proposes a strategy to prepare homogeneous and highly active dispersed cubic quantum dot materials using hydrogel spatial confinement and enhances xylene sensing performance through electron orbital modulation, which provides a novel approach for the preparation of advanced sensing materials.