Synthesis, characterization and optical properties of Ag-doped TiO2 nanoparticles by flame spray pyrolysis

Ag-doped TiO2 nanoparticles with varying dopant concentrations were successfully synthesized using flame spray pyrolysis (FSP) method. An annealing process was carried out for 2 h in air, at 550 degrees C to remove residual organics and increase crystallinity. The structural and chemical properties of the synthesized nanoparticles were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and dynamic light scattering (DLS) devices. In addition, the optical properties of the particles were examined using UV-Vis diffuse reflectance and photoluminescence (PL) spectroscopy. XRD results showed that the synthesized nanoparticles were detected to have major anatase and minor rutile phases. It was determined that the size of the crystallite increases with respect to the (101) plane of the nanoparticles as the amount of Ag additive increases. It was observed that the particles have a hemispherical shape and average particle size in the range of 40-60 nm. The intended dopant amounts and chemical bond structures of the nanoparticles were verified by XPS elemental analysis. It was found that the absorbency increased, shifted the absorption edge to a lower energy and the optical bandgap decreased with the increase of the Ag amount compared to the undoped TiO2. Once the nanoparticles were excited at 360 nm, they yielded emissions at 490 and 550 nm. Luminescence intensity decreased after metal doping as it decreased electron-hole recombination. However, the decay times increased as the incorporation of metal into the structure prevented the degree of overlapping of the charge carriers. Bi- and tri-exponential decay curves were determined and the average decay time was calculated as 80 mu s for the 5% Ag-doped sample.

Automated summary

The Ag-doped TiO2 nanoparticles were successfully synthesized using flame spray pyrolysis method, and their structural and optical properties were analyzed using various techniques. The addition of silver dopant was found to affect the crystallinity, particle size, absorbance, and luminescence characteristics of the nanoparticles. Metal doping decreased luminescence intensity but increased decay times due to prevented electron-hole recombination, with bi- and tri-exponential decay curves observed.