Photoluminescence and photocatalytic properties of Eu3+-doped ZnO nanoparticles synthesized by the nitrate-citrate gel combustion methodC. Shivakumara, Anu K. John, Sukanti Behera, N. Dhananjaya and Rohit SarafEur. Phys. J. Plus, 132 1 (2017) 44DOI: https://doi.org/10.1140/epjp/i2017-11304-5