Magnetic functionalization of ZnO nanoparticles surfaces via optically generated methyl radicals.
D MarinGuillaume GerbaudOlivier MargeatFabio ZiarelliF FerrerOlivier OuariA CamposSylvain BertainaA SavoyantPublished in: The Journal of chemical physics (2023)
The combination of nuclear and electron magnetic resonance techniques, in pulse and continuous wave regimes, is 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-bandgap (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 (•CH3), originating from the acetate capped ZnO molecules. By functionalizing the as-grown zinc oxide NPs with deuterated sodium acetate, the •CH3 electron paramagnetic resonance (EPR) signal is replaced by trideuteromethyl (•CD3). For •CH3, •CD3, and core-defect signals, an electron spin echo is detected below ∼100 K, allowing for the spin-lattice and spin-spin relaxation-time measurements for each of them. Advanced pulse-EPR techniques reveal the proton or deuteron spin-echo modulation for both radicals and give access to small unresolved superhyperfine couplings between adjacent •CH3. In addition, electron double resonance techniques show that some correlations exist between the different EPR transitions of •CH3. These correlations are discussed as possibly arising from cross-relaxation phenomena between different rotational states of radicals.
Keyphrases
- room temperature
- oxide nanoparticles
- magnetic resonance
- ionic liquid
- energy transfer
- blood pressure
- electron transfer
- solar cells
- contrast enhanced
- single molecule
- electron microscopy
- molecularly imprinted
- magnetic resonance imaging
- genome wide
- escherichia coli
- photodynamic therapy
- diffusion weighted imaging
- mass spectrometry
- gene expression
- nk cells
- computed tomography
- gold nanoparticles
- cystic fibrosis
- rare case