Within the frame of the nanostructures surface functionalization, this project aims to generate, to manipulate, and to detect magnetic states localized at the surface of semiconducting and polar zinc oxide nanoparticles (NPs), by electron paramagnetic resonance (EPR). The monitoring of such surface spin states in stable, robust and safe NPs allows for the realization of optically-controlled spin switch, paving the way to future information storage and processing nanotechnologies. After the recent demonstration of the possibility to generate these surface spin state by visible light irradiation (violet laser, 405 nm) in ZnO NPs, we now want to precise the conditions for the generation and the extinction of these excited states by different optical wavelength, but also to study the growth-parameters influence, that of the post-growth gaseous environment, and that of NPs size and morphology.The basic properties study of these excited magnetic states is done by continuous wave EPR (X band) at liquid nitrogen temperature and with optical excitation. The dynamical properties of the spin-spin and spin-lattice interactions are probed by pulse-EPR measurements, preformed on the excited states. Besides, we plan to modulate the statical and dynamical features of the excited magnetic states by applying static and alternative (up to radiofrequency) electric field onto layers of ZnO NPs. These surface spin-states arise from the dissociation of some photo-generated electron-hole pairs (excitons), and are directly related to the greatness of the surface-to-volume ratio, and to the chemical and physical passivation of the polar interfaces between polar NPs and environment. The exacte nature of these spin states is in all probability a complexe of intrinsic and extrinsic point defects, namely some hydrogen ions bound to a zinc vacancy. The appropriate spin Hamiltonian implies a hyperfine interaction between an electronic spin 1/2 and three equivalent protons.