Multilevel Data Encryption Using Thermal‐Treatment Controlled Room Temperature Phosphorescence of Carbon Dot/Polyvinylalcohol Composites

Abstract

Thermal‐treatment controlled room temperature phosphorescence is realized by embedding either originally synthesized carbon dots (CDs) or 200 °C thermal‐treated CDs into a polyvinylalcohol (PVA) matrix through post‐synthetic thermal annealing at 200 or 150 °C. The thermal‐treatment controlled phosphorescence is attributed to the transfer of photoexcitation from the excited singlet state to the triplet state through intersystem crossing, followed by radiative transition to the ground state, which is due to decrease of quenchers (oxygen) in the CDs and suppression of the vibrational dissipations through the chemical bonding of CDs in the PVA matrix. Multilevel fluorescence/phosphorescence data encryption is demonstrated based on the thermal‐treatment controlled phosphorescence from CD@PVA composites.

Carbon Dots‐in‐Matrix Boosting Intriguing Luminescence Properties and Applications

“…The PVA is found to be an ideal candidate for preparing composite film. CDs@PVA composite film can be easily fabricated by homogeneous dispersion of as‐prepared CDs into a PVA aqueous solution, followed by coating and drying/annealing . Such a method is very simple, in contrast to the abovementioned chemical methods for CDs‐based composites.…”

“…Later, two RTP composites with lifetimes of 450 and 8.7 ms were prepared by doping CDs and CDs in PVA and PU matrices, respectively . More recently, thermal‐treatment controlled RTP composites were discovered in which the green phosphorescence appeared in different CDs@PVA films after different thermal annealings (150 or 200 °C) . In addition to PVA, zeolites as the host matrix can also facilitate the production of the RTP property.…”

“…The multilevel fluorescence/phosphorescence data encryption is presented in the thermal‐treatment controlled RTP CDs@PVA composites because of the different luminescence responses of composites annealed at different temperatures . Such an encryption pattern is made using three types of composites ( Figure a).…”

“…b) Photographs of the combined patterns realized after annealing at 80, 150, and 200 °C (from top to bottom), under UV light excitation (left), and after switching UV light off (right). Reproduced with permission . Copyright 2018, Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim, Germany.…”

Photo-induced Afterglow of Carbon Dots for Dynamic Patterning

“…Particularly, CDs materials with room temperature long afterglow have recently become a new research hotspot 30-40 , showing superiority in applications compared to the traditional uorescent CDs. For example, timeresolved data encryption and anti-counterfeit patterns have been manufactured, taking advantage of their prolonged emission lifetime [35][36][37][38][39][40] . Despite the ever-growing interest in these novel materials, to the best of our knowledge, researchers have yet to nd a type of CDs-based long afterglow materials with photoinduced optical memory (PIOM) characteristics.…”