Nonlinear Optical Response of Chloroaluminiumphthalocyanine Encapsulated by Silica Core−Shell Particles

We report for the first time on the synthesis of core-shell particles containing chloroaluminiumphthalocyanine (ClAlPc) prepared using a sol-gel technique. These particles have the dye molecules at the core, encapsulated by silica shell. The mean size of the particle is determined from HRTEM studies and is found to be approximately 0.08 microm. The surface and bulk compositions of the core-shell particles are studied by XPS and EDAX measurements, respectively. Time-resolved fluorescent measurements indicate a decrease in fluorescence lifetime for the core-shell particles as compared to that of bare dye dissolved in ethanol. This is analyzed on the basis of available theoretical models. Third-order nonlinear optical effects are investigated by the Z-scan technique using 8 ns pulses at a wavelength of 532 nm from a frequency-doubled Nd:YAG laser. The analysis indicates that both singlet and triplet excited-state absorption contribute to nonlinear absorption.