S.  Muduli, Game, O. S., Dhas, V. V., Yengantiwar, A., and Ogale, S. B., ?Shape preserving chemical transformation of ZnO mesostructures into anatase TiO2 mesostructures for optoelectronic applications?, Energy & Environmental Science, vol. 4, no. 8, pp. 2835-2839, 2011.