Collections of particles comprising multiple a metal oxide can be formed with average particle sizes less than about 500 nm. In some embodiments, the particle collections have particle size distributions such that at least about 95 percent of the particles have a diameter greater than about 40 percent of the average diameter and less than about 160 percent of the average diameter. Also, in further embodiments, the particle collections have particle size distribution such that effectively no particles have a diameter greater than about four times the average diameter of the collection of particles.