Nanoparticles’ diffusivity studied by fluorescence recovery and holographic grating relaxation techniques
Lyubov’ N. Borodina, Tatiana O. Oskolkova, Irina A. Arefina, Aliaksei Dubavik, Andrei V. Veniaminov; ITMO University, St.Petersburg, Russia
Abstract
Multiple applications of nanophotonics, sensorics, and biomedicine provide a tremendously increasing demand for knowledge on various sophisticated properties of luminescent molecules and nanoparticles. The information about sizes of luminescent nanoparticles, their distribution, changes under the influence of light and other factors is of considerable interest, along with spectral characteristics.
We apply two approaches to study diffusion of nanoparticles and molecules, based on imprinting a photoinduced optical inhomogeneity and monitoring its evolution caused by diffusion. One of the approaches based on known fluorescence recovery technique comprises exposing a narrow strip of a sample with a focused laser beam, and tracking subsequent changes in the spatial distribution of luminescence intensity with the help of a confocal scanning microscope.
Another technique, referred to as the holographic grating relaxation method, or holographic relaxometry, involves recording a grating and observing the diffraction of light, the efficiency of which varies due to a decrease in concentration modulation, hence the refractive index, caused mainly by diffusion.
We have found that in some experiments using the florescence recovery technique its shape appears more complicated, which can be interpreted as manifestation of the diffusion of two forms of particles, by analogy with the complementary grating effect in holographic grating relaxation technique.
The method of fluorescence recovery after photobleaching provides valuable information about the optical and diffusion properties of both the initial and phototransformed species, similar to the holographic relaxation; a comparative diffusivity study by these two techniques proves the agreement between them.
Speaker
Lyubov’ Borodina
International Research and Education Centre for Physics of Nanostructures, ITMO University, St.Petersburg, Russia
Russia
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