" Nanocomposites and nanomaterials"

Nonlinear optical response of ZnO-PMMA nanocomposites under picosecond laser excitation
Komarenko D.O.1, Ronkovych A.V.1, Ovdenko V.M.1,2, Ilchenko S.G.1, Multian V.V.1, Pokutnyi S.I.1, Lisnyak V.V.2, Gayvoronsky V.Ya.1
1 Advanced Materials Nonlinear Optical Diagnostics Lab., Institute of Physics of the NAS of Ukraine. pr. Nauki, 46, Kyiv 03028, Ukraine.
E-mail: vlad@iop.kiev.ua 
2Chemical Faculty, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., Kyiv 01033, Ukraine. E-mail: lisnyak@univ.kiev.ua

In recent times, a remarkable interest has arisen in the development of organic-inorganic hybrid materials [1]. They are based on a polymer matrix with inorganic nanoparticles (NPs) used as solar cells, field-effect transistors, and optoelectronic and nonlinear optical (NLO) devices. Polymers can exhibit pronounced NLO properties or be optically inert matrices, but a composite with an inorganic component will give new synergetic or complementary behavior arising from the interaction of the polymer and NPs at the molecular level. 
In the present study, we investigated the self-action effects in organic-inorganic PMMA–ZnO composites with 1 wt% of ZnO NPs embedded in PMMA films within the ps range of pulsed laser excitation at 1064 nm. We also examined their photoluminescence (PL) response in the UV-visible range. A set of small ZnO NPs with an efficient PL and quadratic NLO response was successfully prepared by the hydrolytic route in non-aqueous solvents [2]. A correlation was found between the Im(χ(3)) and the PL band area at about 2.34–2.41 eV related to the contribution of oxygen vacancies in ZnO was revealed.
The highest efficiency of the refractive NLO response |Re(χ(3))| ~10–10 esu was observed for the composite with PL obtained from CH3CN against 10–11 esu for that obtained from alcohol ethanol/isopropanol solutions on the background of the absorptive NLO response |Im(χ(3))| ~ 10–12 esu for the studied composites for the peak laser intensity excitation up to 1 GW/cm2. 
The results obtained are promising for developing organic-inorganic hybrid nanocomposite materials with effective NLO and PL responses.

1.	Gorbovyi, P., Uklein, A et al. Mater. Res. Express.-2014.- 1 (4).- 045039 
2.	Multian, V. V., Uklein, A.V. et al. Nanoscale Res. Lett. -2017.- 12(1) - 164