RESUMEN

Amorphous polymers with ultralong room-temperature phosphorescence (RTP) are highly promising for various applications. Particularly, polymer-based RTP materials with multiple functions such as color-tunability or stimulus-response are highly desirable for multilevel anti-counterfeiting but are rarely reported. Herein, a facile strategy is presented to achieve a series of polymer-based RTP materials with ultralong lifetime, multicolor afterglow, and reversible response to UV irradiation by simply embedding pyridine-substituted triphenylamine derivatives into the polymer matrix poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA), respectively. Notably, the pyridine group with the capabilities of promoting intersystem crossing and forming hydrogen-bonding interactions is essential for triggering ultralong RTP from the doping PVA system, among which the doping film TPA-2Py@PVA exhibits excellent RTP property with an ultralong lifetime of 798.4 ms and a high quantum yield of 15.2%. By further co-doping with the commercially available fluorescent dye, multicolor afterglow is obtained via phosphorescence energy transfer. Meanwhile, the doped PMMA system exhibits reversible photoactivated ultralong RTP properties under continuous UV irradiation. Finally, potential applications of these doped PVA and PMMA systems with ultralong lifetime, multicolor afterglow, and photoactivated ultralong RTP in multidimensional anti-counterfeiting are demonstrated.

Asunto(s)

Polimetil Metacrilato , Rayos Ultravioleta , Temperatura , Aminas , Piridinas , Polímeros

RESUMEN

For display applications, it is highly desirable to obtain tunable red/green/blue emission. However, lead-free perovskite nanocrystals (NCs) generally exhibit broadband emission with poor color purity. Herein, we developed a unique phase transition strategy to engineer the emission color of lead-free cesium manganese bromides NCs and we can achieve a tunable red/green/blue emission with high color purity in these NCs. Such phase transition can be triggered by isopropanol: from one dimensional (1D) CsMnBr3 NCs (red-color emission) to zero dimensional (0D) Cs3 MnBr5 NCs (green-color emission). Furthermore, in a humid environment both 1D CsMnBr3 NCs and 0D Cs3 MnBr5 NCs can be transformed into 0D Cs2 MnBr4 ⋅2 H2 O NCs (blue-color emission). Cs2 MnBr4 ⋅2 H2 O NCs could inversely transform into the mixture of CsMnBr3 and Cs3 MnBr5 phase during the thermal annealing dehydration step. Our work highlights the tunable optical properties in single component NCs via phase engineering and provides a new avenue for future endeavors in light-emitting devices.

RESUMEN

Efficient exfoliation of well-crystallized (Y0.96Tb x Eu0.04-x )2(OH)5NO3 · nH2O (0 ≤ x ≤ 0.04) layered rare-earth hydroxide (LRH) crystals into tens of micron-sized unilamellar nanosheets has been successfully achieved by inserting water insoluble oleate anions (C17H33COO(-)) into the interlayer of the LRH via hydrothermal anion exchange at 120°C, followed by delaminating in toluene. The intercalation of oleate anions led to extremely expanded interlayer distances (up to approximately 5.2 nm) of the LRH crystals and accordingly disordered stacking of the ab planes along the c-axis and also weakened interlayer interactions, without significantly damaging the ab plane. As a consequence, the thickness of the LRH crystals increased from approximately 1 to 10 µm, exhibiting a behavior similar to that observed from the smectite clay in water. Highly [111]-oriented and approximately 100-nm thick oxide films of (Y0.96Tb x Eu0.04-x ) 2O3 (0 ≤ x ≤ 0.04) have been obtained through spin-coating of the exfoliated colloidal nanosheets on quartz substrate, followed by annealing at 800°C. Upon UV excitation at 266 nm, the oxide transparent films exhibit bright luminescence, with the color-tunable emission from red to orange, yellow, and then green by increasing the Tb(3+) content from x = 0 to 0.04.