ИСТИНА

Zinc oxide and titania are important photocatalysts for photodegradation of organic wastes under UV-light illumination. There are different approaches to expand their scope of applicability by photosensibilisation, and one of them is the decoration of common catalysts with noble metal nanoparticles. In our work we used three methods of the decoration of initial matrices by silver and gold nanoparticles: the Turkevich method, the reduction by borohydride and the one-step hydrothermal synthesis. These methods result in different contacts between metallic and semiconducting nanoparticles. Obtained nanocomposites were studied with UV-vis spectroscopy, XRD, SEM, TEM with local EELS and EDX-analysis. The photocatalytical activity was measured by photodegradation reaction of methyl orange. The EEL spectra were collected using high resolution transmission electron microscope (Zeiss Libra 200FE) with monochromator and omega-filter. High energy resolution allows us to measure SPR peak position in visible range. Moreover, it is possible to collect simultaneously plasmonic peaks and zero-loss peak, which allows one to calculate the relative thickness of the sample. Therefore, it is possible to collect low-energy EEL spectra from individual nanoparticles with respect to their thickness. The obtained composites demonstrate different photocatalytic activities. It may be caused by the different contacts in the composites. In the case of slow reduction, it results in heterogeneous nucleation at the matrix surface. Hence, the formed contact is better. According to the results of UV-Vis and EEL spectroscopy, the contact between metallic and semiconducting nanoparticles results in the shift of the SPR peak position. The data on the photocatalytic activity and absorbance spectra of silver-contained composites demonstrate that the sample with lower photocatalytic activity has better contact because of Ohmic contacts between silver and matrices. This work was supported by RFBR and M.V.Lomonosov Moscow State University Program of Development.