Nanocomposites and nanomaterials

Investigation of charge transfer process in «plasmon core-semiconductor shell»nanostructures 
Afanasyev D.A.1,2,  Ibrayev N.Kh.1
1Institute of Molecular Nanophotonics, Buketov Karaganda State University, Universitetskay st. 28A, Karaganda, 100028, Kazakhstan,
E-mail: a_d_afanasyev@mail.ru

2 Institute of Applied Mathematics, Universitetskay st. 28A, Karaganda, 100028, Kazakhstan 

The charge transfer process in the «plasmon core-semiconductor shell» system is studied. Nanoparticles (NPs) of Ag and Au were used as a plasmon core. TiO2 was used as a semiconductor shell. A method of synthesis of nanostructures (NSs) is described in [1]. Luminescence spectra of solutions of Ag-TiO2 NSs and Au-TiO2 NSs were measured. Luminescence spectra of ethanol solutions of TiO2 NPs and Ag-TiO2 NSs were compared. A new band with a maximum at 575 nm appears in luminescence spectra of Ag-TiO2 NSs. This band is associated with the transfer of an electron from TiO2 to the Fermi level of Ag NPs. The luminescence intensity of Ag-TiO2 is much lower than the intensity of TiO2. It is also connected by the charge transfer.
The luminescence of Ag NPs is registered for an aqueous solution of Ag NPs and Ag-TiO2 NSs. Also, an additional luminescence band (λMAX = 540 nm) appears in the luminescence spectrum for Ag-TiO2. A growth of the thickness of the TiO2 shell from 20 nm to 60 nm does not lead to a change in the luminescence intensity with λMAX = 540 nm. The luminescence at 540 nm is formed when the charge is transferred from a layer of titanium dioxide bordering with silver NP. The removed layer of TiO2 from silver does not participate in the charge transfer process.
Optical properties of Au NPs and Au-TiO2 NSs were studied. The luminescence spectrum is observed for NSs Au-TiO2. The luminescence of Au-TiO2 NSs is related to the luminescence of TiO2. An additional band associated with charge transfer from TiO2 to Au wasn’t observed.

1.	Afanasyev D.A., Ibrayev N.Kh., Serikov T.M., Zeinidenov A.K. Effect of the titanium dioxide shell on the plasmon properties of silver nanoparticles // Russian Journal of Phys Chem. A. – 2016. 90(4). – Р. 833–837.