Lignite-derived carbon quantum dot/TiO2 heterostructure nanocomposites: photoinduced charge transfer properties and enhanced visible light photocatalytic activity

Abstract

Here, we present a facile and green route to cleanly and efficiently utilize low-rank lignite to produce carbon quantum dots (CQDs) in high yields and in situ synthesize CQDs/TiO₂ heterostructure nanocomposites. Unlike other CQDs, the lignite-derived CQDs exhibit obvious concentration-dependent red-shifted absorption, unusual aggregation-induced different color emissions and strong orange-red solid-state fluorescence. Through the optimization of the CQD loading proportion, the 2 wt% CQDs/TiO₂ shows the optimal photocatalytic performance under visible light. We highlight the CQDs/TiO₂ heterostructure nanocomposites by focusing on their dynamic photoinduced charge transfer properties triggered by the heterostructure interface and their application as a photocatalyst under visible light. Our detailed work about the transfer behavior of photoinduced charges in coal-derived carbon quantum dot/TiO₂ heterostructure nanocomposites may shed light on the intrinsic reasons for CQD/semiconductor enhanced photocatalytic activity.