| Abstract | Secure information retrieval technology aims at status identification and documentation authentication. Ideally, materials or devices used in these technologies should be hard to find, difficult to counterfeit, and as simple as possible. This manuscript addresses a novel information retrieval technology, with photoluminescent (PL) semiconductor quantum dots (QDs) synthesized via wet chemistry approaches used as its coding materials. Conceptually, these QDs are designed to exhibit emission at Fraunhofer line positions, namely, black lines in the solar spectrum; thus, the retrieval system can extract useful information under sunshine covering areas. Furthermore, multiphoton excitation (MPE) technology enables the retrieval system to be multilayer information extraction, with thin films consisting of QDs applied to various substrates, such as military helmets and vehicle and fingernails. Anticipated applications include security, military, and law enforcement. QD-based security information can be easily destroyed by preset expiration in the presence of timing agents. |
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