Patent ID: 7547894

Claim:
A method of identifying or detecting an object comprising the steps of: (a) applying onto or into at least a portion of the object an effective amount of a photoluminescent composition comprising: (i) One or more photoluminescent phosphorescent materials, and (ii) One or more photoluminescent fluorescent materials; wherein the one or more photoluminescent phosphorescent materials selectively absorbs and emits electromagnetic energies when charged or activated by either electromagnetic radiation from an excitation source incident upon the composition, or by the emissions of another photoluminescent material, or both, wherein the one or more photoluminescent fluorescent materials selectively absorbs the emission from the one or more photoluminescent materials and emits the electromagnetic energies to give a selected emission signature, such that some or all of the emission signature lies in the infrared portion of the electromagnetic spectrum, the photoluminescent materials being selected so that the emission of one of the photoluminescent materials overlaps with the absorbance of another of the photoluminescent materials, and wherein the selected emission signature is the emission from one or more of the selected photoluminescent fluorescent materials, such emission being essentially unabsorbed by any of the other photoluminescent materials, (b) charging or activating the object, and (c) detecting the emission signature from the charged object.