We report on the development of a nonlinear optical microscopic technique based on two-photon absorption induced photothermal effect capable of detecting individual nonfluorescent nanoparticles with high sensitivity. The method which is inherently confocal makes use of near infrared excitation at high repetition rates and would be of interest in deep tissue imaging. We demonstrate the applicability of the technique by imaging single BaTiO3 nanoparticles, a potential biomolecular label having high photostability, in a scattering environment at fast time scales with a pixel dwell time of 80 μs.

We report on the design and construction of a laser scanning photothermal microscope and present images of gold nanoparticles of size as small as 5 nm. Laser scanning method allows fast image acquisition at 80 μs pixel dwell time so that a 500 × 500 pixel image is acquired in 20 s. Photothermal imaging at fast time scales can have potential applications in variety of fields including tracking of biomolecular transport processes.

The confocal fluorescence microscope is an essential live cell imaging tool in bioscience research. Several experimental investigations in the field of biomedical research require a dedicated confocal fluorescence microscope. However, commercial confocal microscopes are prohibitively expensive for many individual laboratories and they often have an inflexible design not amenable to user desired modifications. Here we report on the design, development, and calibration of a cost-effective dual channel confocal fluorescence microscope that can capture two biological events simultaneously. The microscope is successfully employed to image and study the simultaneously occurring active and passive transport of molecules across the nuclear membrane. Passive diffusion of FITC labelled dextran molecules are monitored along with the active transport of gold nanoparticles of diameter 20 nm in the time-lapse imaging mode. The experiments carried out in digitonin permeabilized HeLa cells indicate that both active and passive nuclear transport pathways coexist together.

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We report on the development of a photothermal microscope capable of detecting and characterizing nonfluorescent metallic nanoparticles in a nanocomposite film. The distribution and number density of gold nanoparticles in Au/BaTiO3 nanocomposite films synthesized with different Au/Ba molar ratio is studied by the microscope.