Synthesis of In 2 O 3 /SnO 2 Nanocomposites and Their Trimethylamine Sensing Performance at Low Temperature

Abstract In this study, In 2 O 3 /SnO 2 nanocomposites demonstrating high sensitivity to trimethylamine (TMA) were successfully synthesized via a hydrothermal method using SnO 2 micron‐sized blocks and In 2 O 3 nanospheres. Compared with pure SnO 2 , the optimal operating temperature of the composite decreased by 40 °C. Notably, the response value increased from 200% (pure SnO 2 ) to 450% at 180 °C under 50 ppm TMA exposure. An in‐depth analysis of its performance and mechanism can be found. The enhanced TMA sensing performance originates from the synergistic effects of hierarchical structure and interfacial engineering. Specifically, the anchored In 2 O 3 nanospheres on SnO 2 microblocks significantly increase the specific surface area, thereby providing abundant active sites for oxygen chemisorption (O 2 − , O − , or O 2− ), which subsequently enhances surface interactions with TMA molecules. Moreover, the formation of n‐n heterojunctions between these semiconductors not only extends the electron depletion layer but also strengthens the local electric field, resulting in two complementary effects: elevated baseline resistance in ambient air due to electron depletion, and markedly reduced resistance during TMA exposure owing to surface redox reactions. Furthermore, this configuration simultaneously accelerates reaction kinetics at the gas‐solid interface. Consequently, the combined effects of improved charge transfer, modulated resistance behavior, and faster surface reactions collectively amplify both the sensitivity and response dynamics of the composite toward TMA detection.