Nanoparticles of ZnGa2O4 and Eu-doped ZnGa2O4 were hydrothermally synthesized varying the process parameters, such as the volume ratio of the cation precursor solutions, temperature and time of growth, and dopant concentration. The nanoparticles were structurally characterized by X-ray diffraction, high-resolution transmission electron microscopy, and selected-area electron diffraction. The studies confirmed the formation of spherically shaped ZnGa2O4 nanoparticles with the standard spinel structure. Photoluminescence (PL) studies show that Eu-doped ZnGa2O4 nanoparticles exhibits a sharp red luminescence due to the intra-4f transitions of Eu3+ ions at an excitation of 397 nm. Luminescence quenching is observed in the nanoparticles at higher Eu concentration. The room-temperature PL measurements of pure ZnGa2O4 nanocrystals monitored at an excitation wavelength of 254 nm gave a peak-shaped spectrum instead of the normally observed bell-shaped spectrum of bulk ZnGa2O4. The bandgap of the ZnGa2O4 nanoparticles is blueshifted compared to the bulk material due to quantum confinement effects. Incorporation of Eu in the nanoparticles was confirmed by inductively coupled plasma atomic emission spectroscopic studies. (c) 2009 The Electrochemical Society. [DOI: 10.1149/1.3070662] All rights reserved.