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Journal Articles Journal of Chemical Physics Year : 2023

Magnetic functionalization of ZnO nanoparticles surfaces via optically generated methyl radicals

Fonctionnalisation magnétique de surface de nanoparticules de ZnO par génération optique de radicaux méthyles.

Abstract

The combination of nuclear and electron magnetic resonance techniques, in pulse and continuous wave regimes, are used to unravel the nature and features of the light-induced magnetic state arising at the surface of chemically prepared zinc oxide nanoparticles (NPs) occurring under 120 K when subjected to a sub band gap (405 nm) laser excitation. It is shown that the four-line structure observed around g ∼ 2.00 in the as-grown samples (beside the usual core-defect signal at g ∼ 1.96) arises from surface-located methyl radicals (• CH 3), originating from the acetate capped ZnO molecules. By functionalizing the as-grown zinc oxide NPs with deuterated sodium-acetate, the • CH 3 EPR signal is replaced by trideuteromethyl (• CD 3). For • CH 3 , • CD 3 and core-defect signals, an electron spin echo is detected below ∼100 K, allowing for the spin-lattice and spinspin relaxation-time measurements for each of them. Advanced pulse-EPR techniques reveal the protons or deuterons spin-echo modulation for both radicals, and give access to small unresolved superhyperfine couplings between adjacent • CH 3. In addition, electron double resonance techniques show that some correlations exist between the different EPR transitions of • CH 3. These correlations are discussed as possibly arising from cross-relaxation phenomena between different rotational states of radicals.
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Dates and versions

hal-04115234 , version 1 (02-06-2023)

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D. Marin, G. Gerbaud, O. Margeat, F. Ziarelli, F. Ferrer, et al.. Magnetic functionalization of ZnO nanoparticles surfaces via optically generated methyl radicals. Journal of Chemical Physics, 2023, 158 (18), pp.184704. ⟨10.1063/5.0152015⟩. ⟨hal-04115234⟩
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