Liaocheng University has Made progress in the Research of Flexible Rom-Temperature Phosphorescent Materials with Adjustable Luminous Color

Organic room temperature phosphorescence (RTP) has broad application prospects, but the development of flexible organic RTP materials, especially environmentally friendly organic RTP materials, is still a huge challenge. Natural polymer-based RTP materials have broad application prospects in the fields of information encryption, biological imaging, and anti-counterfeiting due to their advantages of good biocompatibility, non-toxicity, easy degradation, and rich content.

However, most natural polymer-based RTP materials emit a single color and are in a rigid or powder state, which is not conducive to their application in fields such as multi-color displays and flexible materials. Therefore, it is of great significance to develop flexible RTP materials that can be prepared in a large area and have adjustable luminous colors.

Recently, Professor Li Guang's research group from the School of Materials Science and Engineering of Liaocheng University published a paper titled Ultralong sodium alginate-based room temperature phosphorescence materials with advantages of An academic research paper on color tunability, flexibility and facility large-area fabrication. This is the third research paper published by this research group in this journal in the past two years.

In this paper, a sodium alginate (SA)-based room temperature phosphorescent material with dynamic response to external stimuli was prepared through a simple doping strategy. Under the alternating treatment of water vapor fumigation and heating, the afterglow color achieved good reversible changes. In addition, by adding a trace amount of glycerin for adjustment, a dynamically responsive large-area flexible color-tunable RTP film was successfully prepared.

SA has abundant hydroxyl and carboxyl groups, which can form hydrogen bonds with small molecules and enhance RTP emission through intra- and intermolecular hydrogen bonding. In this study, natural polymer SA-based RTP materials were prepared by doping phenylboronic acid (PBA) and its derivatives in the SA matrix. The 4-carboxyphenylboronic acid doped system SA-CPBA shows the best RTP performance, with a phosphorescence lifetime as high as 231?ms. Water molecules have a greater impact on organic RTP materials, especially water-soluble RTP materials, and can even cause phosphorescence quenching. Therefore, the effect of moisture on the luminescence properties of SA-CPBA was studied.

The results show that after SA-CPBA is steamed and heated, the afterglow shows excitation wavelength-dependent color tunability. As the excitation wavelength increases from 245 nm to 302 nm, the afterglow color changes from blue to green. In addition, under the alternating treatment of steam fumigation and heating, the afterglow color change has good reversibility.

In order to further expand the application fields of SA-based RTP materials, the research group obtained a flexible and transparent RTP film by adding a trace amount of glycerol (G) to the SA-CPBA matrix, and SA-CPBA-G also has excellent Excitation wavelength-dependent color tunability. In addition, the flexible SA-CPBA-G film can be prepared on a large area using a film coating machine. Based on the excellent characteristics of SA-based RTP materials, this research group successfully applied SA-based RTP materials in the fields of flexible display and information encryption.

This study provides guidance for the preparation of environmentally friendly, flexible and tunable polymer-based RTP materials, and helps expand the application scope of SA-based materials to the field of flexible displays.

Sun Shaochen, a 2022 graduate student of Liaocheng University, is the first author of the paper. Professor Li Guang, Professor Wang Liping and Teacher Tao Farong are the corresponding authors of the paper. Liaocheng University is the first signing unit. This research work was supported by the National Natural Science Foundation, the Shandong Provincial Natural Science Foundation and the Liaocheng University Scientific Research Fund.

In recent years, this research group has focused on the research of optically functional polymers and is well-known in Chemical Engineering Journal, Sensors and Actuators B: Chemical, Journal of Materials Chemistry C, European Polymer Journal, Analyst, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Dyes and Pigments, etc. The journal published many papers and actively promoted the research and development of optically functional polymer materials. (Source: School of Materials Science and Engineering, Liaocheng University)