One-Pot Fabrication of High Coverage PbS Quantum Dot Nanocrystal-Sensitized Titania Nanotubes for Photoelectrochemical Processes

Lead sulfide quantum dot nanocrystal (QDNC) sensitized TiO 2 nanotubes have been fabricated using a simple, wet chemical method that is both time- and cost-effective. A single precursor source containing both Pb and S has been employed, with oleylamine as a linker molecule to synthesize the PbS under an ambient pressure based approach. This approach serves to assemble the QDNCs on a TiO 2 nanotube surface. Surface characterization was performed using electron microscopy, X-ray diffraction, and elemental analysis, indicating the formation of PbS quantum dots along the nanotube walls and intertubular spacing. The optoelectronic, photoelectrochemical, and photocatalytic properties of the composite heterostructure have been characterized using absorbance spectroscopy, electrochemical studies (including efficiency measurements), and methylene blue conversion as a probe. A 24-fold increase in the photocurrent of TiO 2 –PbS heterostructure over bare TiO 2 nanotube has been observed. Electrochemical impedance measurements of the TiO 2 nanotube sample indicate donor density of ∼4.5 × 10 19 cm –3 while TiO 2 /PbS heterostructure shows an n-n photoactive heterojunction with a donor density of ∼2.3 × 10 20 cm –3 . A 12% increase in photocatalytic activity and theoretical estimates suggesting almost 40-fold enhancement toward value-added product synthesis with PbS inclusion are presented.