Nonlinear and saturable absorption characteristics of TiO2/carbon nanocomposites in PMMA

Karatay A.1, Donar Y. O.2, Sınağ A.2, Elmali A.1

 1Ankara University, Department of Engineering Physics, Faculty of Engineering, 06100 Beşevler Ankara,Turkey

 2 Ankara University, Department of Chemistry 06100 Beşevler Ankara TURKEY
E-mail: sinag@science.ankara.edu.tr

Organic–inorganic nanocomposites have attracted extensive attention in recent years in the open literature. Novel electronic and optical materials based on these composite materials have found applications in technologically demanding areas such as optical switches, optical waveguides and nonlinear optical devices. Carbon supporting transformed the wide band-gap semiconductor oxide into a highly conductive material. The high electrical conductivity of carbon doped TiO2 was attributed to suboxide formation with substitutional and interstitial carbon, as revealed by XPS and XANES studies [1].

In this study, nonlinear and saturable absorption behaviors of nanocomposite TiO2/carbon based materials in PMMA were investigated. Transparent thin films of TiO2, HC/TiO2, CNT/TiO2, CNT/TiO2-Pt nanocomposites were synthesized by spin coating. The observed blue shift in energy from linear absorption measurements is related to a quantum confinement effect. The nonlinear optical saturation/absorption behavior was investigated by OA Z-scan experiment for nanosecond and femtosecond pulse durations. Nonlinear absorption coefficients and saturation intensity thresholds were found from the fitting of the experimental results for both pulse durations and attributed to change in localized defect state density. The biggest nonlinear absorption coefficients and saturation intensity thresholds of CNT/TiO2-Pt film is attributed to increase localize defect states and strong charge interaction between Pt and TiO2 nanoparticles with addition of Pt. Experimental results show that the nonlinear absorption properties of the TiO2/carbon nanocomposite thin films can be controlled by not only making composite.

1 Kuo C.Y. Prevenient dye-degradation mechanisms using UV/TiO2/carbon nanotubes process // J. Hazard. Mater.-2009. -163. –P. 239-244.