Nanocomposites and nanomaterials

Laser driven behavior of the nanosystem used for the photodynamic therapy 
Harahuts Yu.I., Pavlov V.A., Mokrinskaya E.V., Davidenko N.A., 
Naumenko A.P., Kutsevol N.V.
Taras Shevchenko National University of Kyiv, 62a Volodymyrska St., 01601 Kyiv, Ukraine; E-mail: garaguts.yulia.fox@gmail.com

The method of holographic interferometry in real time was proposed and experimentally applied for the investigation of photothermal and photochemical reactions in composite nanoscale systems. The method is tested using the equipment kit [1] to determine the refractive index (n) and its change (n) of liquid and gaseous media. The necessity of such research is determined by the problems existing in practical medicine [2]. Measurement of Δn of a model object during its illumination with light includes registration of the hologram of cuvettes with the investigated medium, reconstruction of the hologram, illumination of the medium with an exciting light with a certain wavelength (irr) and intensity. Then, using the camcorder, the obtained interference pattern was observed and recorded in the computer for further calculation of n by measuring the spatial frequency of the interference bands appearing in the cuvette image. 
Changes of the refractive index were analysed for the systems of Au sol synthesized into the solutions of Dextran-graft-Polyacrylamide (D-PAA) star-like copolymers in nonionic and anionic forms with photosensitizer Сhlorin e6 (Ce6). The polymer molecular characteristics were described in [3]. Au nanoparticles (AuNPs) were of 1.5 – 6 nm in size. The size of individual polymer molecule in solution was equal to 50–60 nm. D-PAA/AuNPs/Ce6 nanosystem was successfully used for the photodynamic anticancer therapy with laser illumination [4].
In our investigation the laser was used with irr = 650 nm which is close to the long-wavelength maximum absorption of Au nanoparticles. 
It was shown that over time (tirr) after the illumination begins, the number of interference bands increases testifying an increase of n. After ceasing the light, the interference pattern relaxes and the bands disappear. The interference bands are localized only in the volume limited by the laser beam and there is no observed diffusion of the heated solution into other parts of the cuvette. To explain the experimental results, a phenomenological model is proposed which takes into account the features of the molecular structure of the star-like D-PAA copolymer with incorporated Au nanoparticles and photosensitizer Сhlorin e6. 

1.	N. Davidenko et al. Appl. Optics.-2018.-57 (8).-P. 1832-1837.
2.	N. Davidenko et al. Proc. SPIE.-2018.-10612.-P.106120H.
3.	N. Kutsevol et al. Macromol. Symp.-2012.-317-318 (1).-P.82-90.
4.	N. Kutsevol et al. Applied Nanoscience.-2018.-2018.-P. 1-8.