Enhancing electrochemical properties of TiO2 nanotube by incorporation of CdSe quantum dots

The present study describes the synthesis of CdSe-incorporated TiO₂ nanotubes (CdSe@TNT) via a modified hydrothermal method from CdSe-incorporated spherical TiO₂ (CdSe@sTiO₂). The structural and photocatalytic activities of both composites are then compared with spherical TiO₂ (sTiO₂). Quantum dots of CdSe are synthesized by varying Cd:Se precursor ratios and were incorporated into the TiO₂ nanotubes (CdSe@TNT) hydrothermally. It is observed that the ratio of Cd:Se used for forming CdSe quantum dots is directly related to the band gap of CdSe@TNT. Reduction in the band gap of TiO₂ was confirmed using UV–Vis DRS spectroscopy, and the band gap energy was evaluated to be 3.02 eV, 2.94 eV and 2.89 eV for sTiO₂, CdSe@sTiO₂ and CdSe@TNT, respectively. XPS peaks reveal elemental peaks of Cd and Se in the TiO₂ nanostructure, confirming the formation of the composite. The micro Raman spectroscopy and XRD analysis revealed that structure of TiO₂ becomes strained due to incorporation of CdSe in TiO₂. The average crystalline sizes of sTiO₂, CdSe@sTiO₂ and CdSe@TNT are 5.28 nm, 4.36 nm and 2.43 nm, respectively. The morphology of the CdSe@TNT was investigated by HR-TEM. The redesigned interface of heterostructures is further investigated by carrying out the electrochemical properties, and it was observed that the CdSe@TNT heterostructures had a better electrical conductivity. Photocurrent response (I-t) curves for sTiO₂, CdSe@sTiO₂ and CdSe@TNT reveal that after five cycles, a maximum photocurrent value of 0.0363, 0.0970 and 0.1144 mA cm⁻² for sTiO₂, CdSe@sTiO₂ and CdSe@TNT, respectively, was observed. The photocatalytic efficiency of the synthesized nanomaterial was further investigated using methylene blue dye as a model compound.