TiO2 nanotubes/g-C3N4 quantum dots/rGO Schottky heterojunction nanocomposites as sensors for ppb-level detection of NO2

As a strong oxidizing pollutant, NO 2 can cause fire or even explosion. People living in atmosphere containing NO 2 for a long time will significantly affects human health. In this work, we developed a Schottky heterojunction sensor modified by g-C 3 N 4 quantum dots (g-C 3 N 4 QDs) and rGO deposited on TiO 2 nanotubes (TNTs) arrays. This sensor showed high response and extremely fast response/recovery time as well as excellent detection of ppb level of NO 2 at room temperature. TNTs were obtained using a one-step anodic oxidation process. TNTs were modified with g-C 3 N 4 QDs and rGO using quasi -CVD method and cyclic voltammetry during in situ electrodeposition, respectively. TNTs/g-C 3 N 4 QDs/rGO Schottky heterojunction sensor exhibited high sensitivity to 10 ppm of NO 2 (response equal to 15982) at room temperature. Below 15 ppb, sensing response also can reach 127. Sensor response was very fast and increased to 15982 in just 2 s when exposed to 10 ppm of NO 2 after which it recovers 90% within 1.16 s. This work clarified the influence of abundant oxygen vacancies (VO · ) in TNTs and photogenerated electrons on TNTs/g-C 3 N 4 QDs/rGO nanostructures as well as their sensing performances. Our experimental details demonstrated that Schottky barrier was established between TNTs and rGO, which was very beneficial for ppb-level NO 2 detection at room temperature.