TEM and SEM analysis
Fig. 1 illustrates the morphological properties of GO, TNT and GO/TNT through TEM and SEM analysis. As shown in Fig. 1(a) and (b), GO appeared with layer structure and each dimensional size about 2-4 micrometer. Fig. 1(c) and (e) indicate that TiO2 nanotubes were successfully fabricated with several hundred nanometers in length and 8 nm in diameter. In the GO/TNT composite, as shown in Fig. 1(d) and (f), the heterojunction between GO and TNT would be generated thanks to the chemical bonding including Ti-C or Ti-O-C. Hence, when irradiation arrived, the easier photoelectrons transferred from TNT to GO, the longer lifetime of excited carriers was prolonged. As a consequence, the photocatalytic performance for degradation of organic pollutants was enhanced [5, 6]. As mentioned in many previous works [7-9], the curling and scrolling process of TiO2 nanosheets during the hydrothermal treatment played a crucial role in the formation of TiO2 nanotubes. Additionally, when in situ composting TNT with GO, TiO2 and GO sheets have a tendency to aggregate and unequally disperse in water due to the hydrogen bond (H-bond) and van der Waals attraction [10, 11]. Therefore, on one hand, the TNT's length in GO/TNT composite was slightly reduced. On the other hand, the specific surface area of GO/TNT was also decreased, as shown in table 1.