Figure 1

(a) Two-photon photothermal image of the 70 nm BaTiO₃ nanoparticles spin coated on a coverslip at 4000 rpm for 30 s. The images are taken with 6 mW pump power and 0.8 mW probe power at the sample. The inset shows the pseudo 3D image of single BaTiO₃ corresponding to the thermal profile generated. The SNR in the images shown is 47 (b) Scanning electron microscopy image of BaTiO₃ having an average size of 70 nm prepared same as above. The figure shows single isolated BaTiO₃ nanoparticles on the coverslip. (c) Particle size distribution histogram of BaTiO₃ nanoparticle measured from the SEM images. The dotted line shows a Gaussian curve fit and the average particle size is found to be 70 nm and size distribution is (13 ± 2)%. (d) Two-photon photothermal intensity distribution histogram of BaTiO₃ nanoparticles. The percentage distribution in intensity is (41 ± 5)%. Since the two-photon photothermal intensity scale with volume of the particle the intensity distribution is expected to be three times that of the particle size distribution.