Optical Limiting Characteristics of Core-Shell Nanoparticles

TiO2 nanoparticles were synthesized by hydrothermal method at 180°C from TiOSO4 aqueous solution with 1 m/l concentration. The obtained products were coated with silica by means of a seeded polymerization technique for a coating time of 1440 minutes to obtain well-defined TiO2@SiO2 core-shell structure. The uncoated and coated nanoparticles were characterized by using X-Ray diffraction technique (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) to study their physico-chemical properties. Evidence from XRD and FTIR results show that SiO2 is homogenously coated on the surface of titania particles. FTIR spectra show that there exists an interaction between TiO2 and SiO2 and results in the formation of Ti-O-Si chemical bonds at the interface of TiO2 particles and SiO2 coating layer. The open aperture z-scan was carried out in both pulsed and CW laser. The RSA observed using CW laser and effective three-photon type absorption seen using pulsed laser at this wavelength, is of potential application in fabricating optical limiting devices. The non linear optical limiting properties of TiO2 and TiO2@SiO2 nanoparticles dispersed in ethylene glycol were studied at 532 nm using 5 ns Nd:YAG laser pulses and diode pumped Nd:YAG laser. Results indicate that these compounds are a potential candidate for low-power optical limiting applications and it is seen that the optical nonlinearity is enhanced in core-shell structures when compared with single counterparts.