The present disclosure relates to microcapsules that include a shell material and a core material. The core material of the microcapsules contains an environmentally sensitive luminescent colorant which exhibits characteristics of an emitted wavelength bandwidth, a peak intensity for emission and a time for luminescence decay, one or more of the characteristics capable of changing upon exposure to a given environment, and a luminescent standard which exhibits characteristics of an emitted wavelength bandwidth, a peak intensity for emission and a time for luminescence decay, one or more of the characteristics do not change upon exposure to said given environment.
James D. Oxley; Jenny J. Finbiner; Nitin Nitin