Ultralong and Color-Tunable Room-Temperature Phosphorescence Based on Commercial Melamine for Anticounterfeiting and Information Recognition

Abstract

Advances have been made in the research on color-tunable organic ultralong room-temperature phosphorescence (OURTP) materials. Due to the high cost of raw materials, complex and strict synthesis conditions, and low yields, it is hard to obtain cheap commercial OURTP materials within a short time. Therefore, it is of practical significance to research and develop new OURTP functions based on commercialized organic materials. In this study, the OURTP characteristics of melamine (MEL), a kind of commercially available, cheap, and pure organic material, were investigated and explored. MEL was found with color-tunable and excellent OURTP, the average lifetime can reach 0.74 s, and the phosphorescence quantum yield can reach 17%. Since the ratio of molecular phosphorescence of MEL to the ultralong phosphorescence mediated by H-aggregation differs with the excitation wavelength and their luminescence life spans are also different, the color of OURTP materials is dependent on both excitation wavelength and time. Moreover, the OURTP characteristics of MEL can be utilized in anticounterfeiting and information identification.

Time-resolved color-changing long-afterglow for security systems based on metal–organic hybrids

“…Even after 2.0 s, the afterglow emission was still discernible. To the best of our knowledge, such time-resolved color change from yellow to green light is greatly different from a published pure organic material melamine (MEL), 72 which shows dual emission afterglow 55 that dynamically transforms from blue into green as time progresses. Furthermore, similar to Cd-impc, Znimpc also performs similar time-dependent photoluminescence (PL) from blue-white to yellow and then green emission before and after turning off the excitation source.…”

“…52,71 In addition, Lv et al definitely pointed out that the existence of H-aggregation was responsible for MEL green OURTP (organic ultralong room-temperature phosphorescence). 72 The role of π⋯π stacking interactions was highlighted in both reports. Inspired by the above theory, we measured the orientation and distance of π⋯π stacking in the Himpc dimer.…”

Poly(arylene piperidine) Quaternary Ammonium Salts Promoting Stable Long‐Lived Room‐Temperature Phosphorescence in Aqueous Environment

“…Compared to numerous previously reported RTP of quaternary ammonium systems, the phosphor-doped PMMA matrix, RTP in water, and PBHDB@ PMMA film in air or soaked in water exhibits a longer phosphorescence lifetime (Figure 1c). [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] Interestingly, the PBHDB@PMMA film still exhibited extraordinary turquoise phosphorescent emission with a duration of 10 s, as observed by naked eyes in water (Video S1, Supporting Information). As depicted in Figure S15, Supporting Information, the UV absorption intensity of the film slightly decreased after soaking it in water.…”

“…In addition, a stable turquoise afterglow emission was achieved in water, which is rarely observed in Images of three doped polymer matrix films (HDBP@PMMA, PBN@PMMA, and PBHDB@PMMA) after 254 nm UV irradiation for 30 s. b) Proposed mechanism of long-lived polymeric RTP. c) Comparison of phosphorescence lifetime between film PBHDB@PMMA and existing research [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] on quaternary ammonium salt systems, phosphors-doped PMMA matrix systems, and RTP in water. organic polymeric systems, especially for those without complex cross-linking structures.…”

Selective Ligand Sensitization of Lanthanide Nanoparticles for Multilevel Information Encryption with Excellent Durability

“…Alternatively, luminophores displaying multiple emissions at a single excitation wavelength were adopted, affording different colors . In addition, luminophores with long lifetime were also utilized to allow for information storage and security in both spatial and temporal domains. ,, Yet, with these materials, information encryption was achieved through manipulation of excitation and/or emission wavelength, which can be potentially deciphered with the variation of irradiation wavelength. Thus, multilevel information encryption was more desirable, where external stimuli other than illumination were required for the information decryption process.…”