Methods for making disinfecting compositions based on phototherapy, systems for use in disinfecting with a combination of photosensitizers, and the disinfecting compositions themselves, are described. Concentrations of the photosensitizers can be based on the particular light source and the wavebands or fluence rates emitted by the light source for maximum singlet oxygen generation. Concentrations of the photosensitizers can also be based on the quantum yield of the photosensitizers.