Identification of the Mechanisms of a Localized Surface Plasmon Resonance Peak Blue Shift in Magnetic Field Pretreated ZnO/Ag Nanocomposites.

Zinc oxide-based nanocomposites are of great scientific interest due to their unique optical properties, making them promising materials for applications in plasmonic and sensor systems. In this study, we pay special attention to the analysis of the magnetic field-induced blue shift of the localized surface plasmon resonance (LSPR) peak in ZnO/Ag nanocomposites. This phenomenon was investigated because of its unexpected manifestation in nonmagnetic semiconductor-based systems that may have a potential for developing magnetically tunable plasmonic devices. ZnO/Ag nanocomposites were synthesized via photochemical reduction under ultraviolet irradiation. The LSPR spectral response was analyzed after ZnO NPs were exposed under an external magnetic field. The blue shift of the LSPR peak of ZnO/Ag nanocomposites observed in the magnetic field pretreated samples was thoroughly studied, and its possible physical mechanisms were critically discussed. Among the proposed explanations, one of the most probable mechanisms is the magnetic field-induced change in the refractive index of the ZnO nanoparticle (NP) surface, caused by magnetization effects. This surface feature is attributed to a high concentration of single-charged oxygen vacancies ( ), which generate unpaired electron spins and impart ferromagnetic-like properties to the ZnO nanoparticles. The findings contribute to the understanding of magnetoplasmonic interactions in hybrid semiconductor-metal nanostructures and may inspire future studies focusing on magnetic field-induced LSPR phenomena for advanced sensing and photonic applications.