Fig. 2a shows that the TiO2 nanobelts have the width of 50-200 nm, the tAg2S QDs. The Ag2S QDs (Fig. 2c) agglomerate to form near spherically shaped Ag2S nanoparticles in 100-200 nm in diameter. As shown in Fig. 2d, a layer of ultra-small Ag2S QDs are assembled onto the surface of TiO2 nanobelts. The formed heterostructure not only possesses enhanced visible and NIR absorption due to the Ag2S on the surface of TiO2 nanobelts, but also has large specific area to facilitate close contact with pollutant molecules. Moreover, the SEM images of Ag2S QDs/TiO2 nanobelt heterostructures with mole ratios at 1:2 and 1:4 also demonstrate the formation of heterostructure (Fig. S2). EDS (Fig. S3) shows that Ag, S, Ti and O elements are found in the Ag2S QDs/TiO2 nanobelt heterostructures, and no other impurities are observed in the spectra.hickness of 20-40 nm, and the length of tens of micrometers [6]. After the acid etching process, the surface-coarsened TiO2 nanobelts are obtained (Fig. 2b), which have a large specific surface area and can offer abundant nucleation sites for the assembling of