TiO2 nanoparticles reach visible spectrum with simple doping technique

Nontoxic, chemically stable, and relatively inexpensive-to-fabricate titanium dioxide (TiO₂) semiconductor nanoparticles are of broad interest as photocatalysts, and, when doped with vanadium (V), become active in the visible spectrum for applications in dye-sensitized solar cells and possible illumination/sensing applications. Unlike existing immersion, solgel, and hydrolysis-based V-doping processes that are expensive and complex, researchers at the University of Puerto Rico (San Juan, Puerto Rico) have developed a simple doping technique that reduces the bandgap and increases the photo-quantum yield of TiO₂ nanoparticles, allowing them to cost-effectively achieve visible-spectrum operation.

In the synthesis method, commercially available TiO₂ nanoparticles were added to varying molar solutions of vanadium oxalate (VOC₂O₄) created in a simple chemical reaction between low-cost vanadium oxide (V₂O₅) microparticles and readily available oxalic acid (H₂C₂O₄). Several samples were prepared by varying the Ti:V ratio (1:1, 2:1, and 8:1 corresponding to samples TV11, TV21, and TV81, respectively). The V-doped nanoparticles were examined using transmission electron microscopy; from electron-energy loss spectra (EELS), a reduction in the bandgap of 0.5 eV (about 20% less than the nominal 3.03–3.2 eV) was measured for sample TV21 compared to undoped pure TiO₂ nanoparticles (sample P25)—a 2.5X improvement over other doping methods. This bandgap reduction enables increased ultraviolet/visible absorption. Contact Maxime Guinel at[email protected].