Distance-Dependent Energy Transfer between Ga2O3 Nanocrystal Defect States and Conjugated Organic Fluorophores in Hybrid White-Light-Emitting Nanophosphors

Abstract

We report a quantitative analysis and development of hybrid white-light-emitting nanoconjugates, prepared by functionalizing colloidal γ-Ga2O3 nanocrystals with selected organic fluorophores. Using the Forster resonance energy transfer (FRET) formalism, we studied the coupling of native defect states in Ga2O3 nanocrystals, as energy donors, with different orange-red-emitting fluorophores bound to nanocrystal surfaces, as energy acceptors. Variations in the average nanocrystal size and dye surface coverage were used to characterize the efficiency of the energy transfer process and the corresponding donor–acceptor separations. The results show that for approximately three rhodamine B molecules per nanocrystal the energy transfer efficiency increases from 23% to 49% by decreasing the NC size from 5.3 to 3.6 nm. These FRET efficiencies correspond to the estimated donor–acceptor distances of 3.55 ± 0.02 and 2.99 ± 0.03 nm, respectively. Similar trends were observed for ATTO 590-conjugated Ga2O3 nanocrystals, a...