Synthesis of Visible Light Excitable Carbon Dot Phosphor‐Al₂O₃Hybrids for Anti‐Counterfeiting and Information Encryption

Abstract

The preparation of room temperature phosphorescent carbon dots still faces great challenges, especially in the case of carbon dots endowed of visible‐light excitable room temperature phosphorescence (RTP). To date, a limited number of substrates have been exploited to synthesize room temperature phosphorescent carbon dots, and most of them can emit RTP only in solid state. Here, the synthesis of a composite obtained from the calcination of green carbon dots (g‐CDs) blended with aluminum hydroxide (Al(OH)3) is reported. The resultant hybrid material g‐CDs@Al2O3 exhibits blue fluorescence and green RTP emissions in an on/off switch process at 365 nm. Notably, this composite manifests strong resistance to extreme acid and basic conditions up to 30 days of treatment. The dense structure of Al2O3 formed by calcination contributes to the phosphorescent emission of g‐CDs. Surprisingly, g‐CDs@Al2O3 can also emit yellow RTP under irradiation with white light. The multicolor emissions can be employed for anti‐counterfeiting and information encryption. This work provides a straightforward approach to produce room temperature phosphorescent carbon dots for a wide range of applications.

Endowing Carbon Dots with Long‐Lived Phosphorescence Emission in Aqueous Solutions

“…Remarkably, g‐CDs@Al 2 O 3 also emitted phosphorescence in aqueous media and manifested persistent resistance to harsh acid and base conditions. [ 20 ] Zeolites are crystalline solids composed of aluminosilicates or aluminum phosphates with distinct structures and consistent pores, which are competitive as a host matrix for encapsulating CDs and activating RTP emission. CDs are produced by the dehydration‐carbonation of organic precursors during the crystallization of the zeolite skeleton, and they are confined as guests in the zeolite host matrix.…”

“…Reproduced with permission. [ 20 ] Copyright 2023, Wiley‐VCH. d) Schematic illustration of the synthesis and chemical structure of the F‐C‐dots, Py‐C‐dots, and Pw‐C‐dots.…”

“…[ 19 ] Furthermore, Zhang's group synthesized RTP CDs materials that exhibited durable resistance in aqueous media, as well as to harsh acid and alkaline conditions, by calcining g‐CDs@Al 2 O 3 composites which can be excited under visible light and UV lamps. [ 20 ]…”

Visible-Light-Excited Room-Temperature Phosphorescent Carbon Dots via Surface Amination in a Microreactor for Multimode Anticounterfeiting

“…Different precursors were used to replace 2,4diaminobenzenesulfonic acid, resulting in various optical properties, proving that the regulation highly depends on the choice of the precursors. 9 Cao et al tested several complex compounds to build visible-light-excited RTP CDs. 29 In this report, CDs from safranine T and fluorescein isothiocyanate isomer exhibited excitation in visible light, while others behaved undesirable.…”

Carbon Dots@Allophane Core–Shell Nanoparticles with Long-Lifetime Room-Temperature Phosphorescence for Anti-Counterfeiting Applications

“…This is because the formation of hydrogen bonds, covalent bonds, or spatial structure constraints in the hybrid systems of CDs can effectively suppress the intramolecular vibration consumption and nonradiative transition of triplet excitons and isolate environmental quenching. However, current construction strategies mainly involve multistep synthesis routes, which increase the complexity of reactions and the periodicity of experiments. − To embed the carbon source in situ into the matrix, it is necessary to carefully consider the assembly relationship between the carbon source and matrix precursor and provide a strong driving force for coassembly. , However, designing in situ fabrication strategies to achieve the double constraints of strong covalent bonds and spatial structures is a significant challenge.…”