Sensors and/or taggants feature high optical gain materials which are disposed in a high scattering environment. These materials, when adequately excited, emit intense and spectrally narrow light that is dependent on the chemical environment in which high gain materials are dispersed. When two materials are placed in the same high scattering environment, the spectal emission properties of each emitter will depend on the chemical composition of the surrounding medium. The switching or transferring of energy from one emitter to the other when the chemical environment is changed in a specific manner is enabled and a shift in the spectral emissions can be detected and/or predicted.