Electron Paramagnetic Resonance (EPR) study of efficient and tunable photoluminescent bohemite (γ-AlOOH ) hybrid nanoplates

Valeria Yarmiayev, Chemistry, Bar Ilan University, Nanomaterials Research Center, BINA, Ramat Gan, Israel

White LEDs (WLEDs) are candidates to revolutionize the lighting industry towards energy-efficient and environmental friendly lighting and displays. The current challenges in WLEDs encompass high luminous efficiency, chromatic stability, high color-rending index, and price competitiveness. Here, we report a route to design high-efficient WLED by combining UV-LED chip and bohemite (γ-AlOOH ) hybrid nanoparticles. The synthesis of the nanoparticles relies on the aqueous or non-aqueous sol-gel process involving the reaction of aluminum isopropoxide in water or benzyl alcohol.

The bohemite nanoparticles were characterized by Electron Paramagnetic Resonance (EPR) analysis under UV irradiation, in order to capture the presence of light-induced paramagnetic centers in the nanoparticles. The series of samples synthesized in benzyl alcohol show benzoate species on the surface. Herein, we used EPR spin traps – species that catch unstable radicals following two approaches: i) either the spin trap reacts with the bohemite surface species to yield stable molecular radical species, ii) or a stable radical reacts with radical species to yield diamagnetic species.

The results of EPR analysis demonstrate a different behavior for bohemite nanoparticles synthesized by water or benzyl alcohol routes.