Recently, Professor Zhang Xia and her team from College of Sciences, NEU, have published an online research paper titled “Enabling controllable time-dependent phosphorescence in carbonized polymer dots based on chromophore excited triplet energy level modulation by ionic bonding” in the prestigious chemical journal Angewandte Chemie International Edition.
Materials with time-dependent phosphorescence color (TDPC) can offer additional channels in the time dimension to materials with room-temperature phosphorescence (RTP), under a single stimulus, enabling multi-level encryption patterns, three-dimensional displays, and multiplexing imaging. Thus, TDPC materials are highly attractive for realizing multi-tiered dynamic information encryption and anti-counterfeiting. However, the development of self-protected or matrix-free TDPC materials remains limited due to the risks of crystalline structure defects and phase separation issues. Additionally, for TDPC materials, the regulation of multiple luminescent centers and the understanding of their underlying mechanisms still remain challenging. Carbonized polymer dots (CPDs), with their unique cross-linked polymer hybrid nanostructures and intrinsic luminescent behavior, favor the formation of abundant surface states and the coexistence of multiple excited-state species, providing possibilities for the design and development of novel multi-mode TDPC materials.
This paper reported a high-contrast TDPC carbide polymer dot material with regulable lifetime. Simple pyrolysis of aspartic acid and alkali metal ions were conducted by a novel and synthetically friendly strategy, hence introducing ionic bonds into such self-protected CPDs. DFT calculations and structural characterization confirm the modulating role of high-density ionic bonding in the triplet state energy levels of the chromophores, to achieve the stable existence of green phosphorescent and red phosphorescent luminescent centers in CPDs. Moreover, the luminescence lifetimes of such materials (from tens of milliseconds to hundreds of milliseconds) can be precisely modulated according to the heavy-atom effect and cross-linking-enhanced emission (CEE) effect. Simultaneously, the effective radiative energy transfer can also be used to better understand the intrinsic mechanism of TDPC materials, further expanding the fundamentals of designing high-quality TDPC materials and enabling more flexible modulation of luminescent properties, and taking an important step to broaden the range of intelligent phosphorescence applications.
The first author of the paper is Sun Jie, a postgraduate student from NEU, and the corresponding author is Professor Zhang Xia of the College of Sciences. Professors Han Yide, Zhang Lin, Li Wenhao, and Senior Experimentalist Wang Nan of NEU, along with Professor Wang Dingsheng of the Tsinghua University, participated in the supervision of the paper. The Analysis and Testing Center of NEU provided the main testing services for this paper.