TiO2 flower-like nanostructures decorated with CdS/PbS nanoparticles

• TiO2 flower-like nanostructures were prepared with the use of Ti foil and 30% H2O2.
• QDs of CdS and PbS were deposited using the SILAR method.
• The SILAR method makes it possible to control the size of QDs.
• Band gap energy of CdS was found to be 2.35 eV.
• Sensitization of TiO2 with CdS or PbS improves the photoelectrochemical properties.

Flower-like nanostructures of TiO2 were prepared by immersing Ti foil in 30% H2O2 at 80 °C for times varying from 15 to 240 min. Upon annealing at 450 °C in an Ar atmosphere, the received amorphous samples crystallized in an anatase structure with rutile as a minority phase. SEM images revealed that partially formed flowers were present at the surface of the prepared samples as early as after 15 min of immersion. The size of the individual flowers increased from 400–800 nm after 15 min of reaction to 2.5–6.0 μm after 240 min. It was also found that surface is very rough and surface development is considerable. After 45 min of immersion, the nanoflowers were sensitized with CdS and PbS quantum dots (QDs-CdS/QDs-PbS) deposited using the SILAR method from water- and methanol-based precursor solutions at different concentrations (0.001–0.1 M). QDs-CdS crystallized in the hawleyite structure, while QDs-PbS in the galena form. SEM analysis showed the tendency of quantum dots to agglomerate at high concentrations of the precursor in water-based solutions. QDs obtained from methanol-based solutions were uniformly distributed. The produced QDs-PbS were smaller than QDs-CdS. Based on the optical reflectance spectra, the band-gap energies of TiO2 nanostructures with and without QDs were calculated to be 3.32 eV for flower-like TiO2 nanostructures and 2.35 eV for QDs-CdS. The photoelectrochemical behaviour of nanoflowers was found to improve significantly after the deposition of QDs-CdS.

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