Visible-light-activated TiO2–NiFe2O4 heterojunction for detecting sub-ppm trimethylamine

Trimethylamine (TMA), which mainly emanates from decaying fish, is an important freshness indicator of seafood. In this work, a TiO2–NiFe2O4 heterojunction was successfully synthesized for TMA detection using a simple and efficient hydrothermal method. The materials were characterized using X-ray diffraction, scanning electron microscopy, photoluminescence spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy. The TiO2–NiFe2O4-based sensor exhibited the largest response (12) to 10 ppm of TMA at 307 ℃. The response was further improved under white-light irradiation, increasing from 2.5 to 4.5 as the TMA concentration approached 3 ppm. The enhanced gas-sensing performance of the TiO2–NiFe2O4 sensor under light irradiation was then explored by density functional theory (DFT) with an optical carrier. We believe that the developed strategy improves the gas-sensing ability for TMA detection and can potentially be used in gas sensors.