¹National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”
37, prosp. Peremohy, 03056 Kyiv, Ukraine
²Institute of Physics of the CAS,
2, Na Slovance, 18221 Prague, Czech Republic
³V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine
41, prosp. Nauky, 03680 Kyiv, Ukraine
*E-mail: dariyasavchenko@gmail.com

Abstract. Silica-carbon with zinc (SiO₂:C:Zn) nanocomposites obtained via infiltration with aged luminescent zinc acetylacetonate (Zn(acac)₂) ethanol solution of two concentrations (1 or 4%) into the fumed silica (SiO₂) matrix have been studied using EPR within the temperature range 6…296 K before and after thermal annealing. The EPR spectrum of SiO₂:C:Zn nanocomposites consists of three signals with the Lorentzian lineshape corresponding to paramagnetic centers with S = 1/2, which are related to carbon dangling bonds (CDB) (g = 2.0029(3)), silicon dangling bonds (g = 2.0062(3)) and oxygen-centered carbon-related radicals (CRR) (g = 2.0042(3)). A small EPR linewidth (<1 mT) observed for CDB and oxygen-centered CRR allows us to conclude that they are in the sp3-hybridized state. It was found that the temperature dependence of the EPR signal integrated intensity of the CDB and oxygen-centered CRR follows the Curie–Weiss law with a small positive value of the Curie–Weiss constant, which indicates that the weak ferromagnetic exchange interaction takes place in the spin system of CDB and oxygen-centered CRR. It was supposed that the carbon-related centers are clustered in SiO₂:C:Zn nanocomposites. We assume that the oxygen-centered CRR in the sp3-hybridized state are associated with luminescent centers in previously reported aged Zn(acac)₂/C₂H₅OH solution.

Keywords: silica-carbon nanocomposites, carbon-related centers, dangling bonds, exchange interaction, electron paramagnetic resonance.

Full Text (PDF)

References

Back to Volume 24 N2