The Preparation and Characterization of Functional Nanocomposite Films by Laser Ablation
EMSL Project ID
1640
Abstract
An important aspect this project is the investigation of ultraviolet laser ablation techniques in the deposition process. At these shorter wavelengths the absorptivity of the raw composite materials is high. This facilitates the use of lower laser fluences to reach the ablation threshold which, in turn, allows greater control over the overall ablation process. TiO2 in the anatase form has photoactivities which have been used previously for photocatalyst and photoelectrode applications. In one study, nanoparticles of Pt in TiO2 matrix have been prepared by the co-sputtering method. At low concentrations of Pt, it was found that the Pt metal is bound-up as PtO2 or in a Pt-Ti-O complex. After annealing, metallic Pt in the form of nanoparticles was observed. Photoemission in the visible light wavelength range was observed when Pt/TiO2 nanocomposites were excited by the light (350nm) at 77K, indicating the existence of some energy levels deep within the TiO2 band gap. However, only TiO2 in the rutile form was observed with Pt nanoparticles created by co-sputtering. Usually, if a surface state is formed it only appears at or near the surface. However, the results from Pt/TiO2 nanocomposites indicate that some surface or excitonic states may be formed in the bulk of matrices by the embedded nanoparticles, and that their preparation procedure (co-sputtering vs. laser ablation) may determine the nature of the final crystal form of the matrix. The formed energy levels may depend on the composition of the nanoparticles, as well as, the matrix. Thus, this project has become a preliminary investigation into a new technique for producing nanoparticles from metals (Pt, Au, Ag) and wide-band gap materials.
Project Details
Project type
Exploratory Research
Start Date
1999-07-28
End Date
2002-09-09
Status
Closed
Released Data Link
Team
Principal Investigator