Reversible Local Protonation-Deprotonation: Tuning Stimuli-Responsive Circularly Polarized Luminescence in Chiral Hybrid Zinc Halides for Anti-Counterfeiting and Encryption.

Precise control over the organic composition is crucial for tailoring the distinctive structures and properties of hybrid metal halides. However, this approach is seldom utilized to develop materials that exhibit stimuli-responsive circularly polarized luminescence (CPL). Herein, we present the synthesis and characterization of enantiomeric hybrid zinc bromides: biprotonated ((R/S)-C12H16N2)ZnBr4 ((R/S-LH2)ZnBr4) and monoprotonated ((R/S)-C12H15N2)2ZnBr4 ((R/S-LH1)2ZnBr4), derived from the chiral organic amine (R/S)-2,3,4,9-Tetrahydro-1H-carbazol-3-amine ((R/S)-C12H14N2). These compounds showcase luminescent properties; the zero-dimensional biprotonated form emits green light at 505 nm, while the monoprotonated form, with a pseudo-layered structure, displays red luminescence at 599 and 649 nm. Remarkably, the reversible local protonation-deprotonation behavior of the organic cations allows for exposure to polar solvents and heating to induce reversible structural and luminescent transformations between the two forms. Theoretical calculations reveal that the lower energy barrier associated with the deprotonation process within the pyrrole ring is responsible for the local protonation-deprotonation behavior observed. These enantiomorphic hybrid zinc bromides also exhibit switchable circular dichroism (CD) and CPL properties. Furthermore, their chloride counterparts were successfully obtained by adjusting the halogen ions. Importantly, the unique stimuli-responsive CPL characteristics position these hybrid zinc halides as promising candidates for applications in information storage, anti-counterfeiting, and information encryption.

Continuously Multiplexed Ultrastrong Raman Probes by Precise Isotopic Polymer Backbone Doping for Multidimensional Information Storage and Encryption.

Raman-based super multiplexing has attracted great interest in imaging, biological analysis, identity security, and information storage. It still remains a great challenge to synthesize a large number of different Raman-active molecules to fulfill the Raman color palette. Here, we report a facile and systematic strategy to construct continuously multiplexed ultrastrong Raman probes. By precisely incorporating different ratios of 13C isotope into the backbone of poly(deca-4,6-diynedioic acid) (PDDA), we can obtain a library of PDDAs with tunable double-bond Raman frequencies and adjustable intensity ratios of two triple-bond (13C≡13C and 12C≡12C) Raman peaks, while retaining the ultrastrong Raman signals and physicochemical properties of the polymer. We also demonstrate the successful application of 13C-doped PDDAs as security inks to generate a novel 3D matrix barcode system for information encryption and high-density data storage. The isotopically doped PDDA series herein pave a new way to advance Raman-based super multiplexing for diverse applications.

Circularly Polarized Room-Temperature Phosphorescence with an Ultrahigh Dissymmetry Factor from Carbonized Polymer Dots by Stacked Chiral Photonic Films.

Developing circularly polarized room-temperature phosphorescent (CPRTP) materials with a high dissymmetry factor (glum) and long afterglow is very attractive but highly challenging. Here, a CPRTP emission featuring ultrahigh glum value and desired visualization characteristic in a bilayer composite photonic film is achieved for the first time. In the constructed system, N and P co-doped carbonized polymer dots (NP-CPDs) are dispersed into polyvinyl alcohol (PVA) as the phosphorescent emitting layer, and helically structured cholesteric polymer films are used as selective reflective layers to convert the unpolarized emission of NP-CPDs into circularly polarized emission. On the basis of the modulation of the helical structure period of the cholesteric polymer, the bilayer composite film enables NP-CPDs to obtain a high glum value. Notably, the optimized photonic film emits CPRTP with glum as high as 1.09 and a green afterglow lasting above 8.0 s. Moreover, the composite photonic array films featuring information encryption characteristics are developed by modulating the liquid crystal phase of the cholesteric polymer film and the dot coating position of the NP-CPDs/PVA layer, thus expanding the application of CPRTP materials in cryptography and anti-counterfeiting.