Regulating The Response Behavior Of Stimuli-responsive Photofunctional Materials By Counterions And Its Application In Secure Printing

Recording information on paper has always been the most important method for keeping records of human activities and spreading civilization.However,the traditional information recording method suffers from security issue of information leakage.With the rapid development of information science,how to achieve information security and protection on paper has become significant.Therefore,the development of security printing has attracted wide interest for researchers.The stimulus-responsive functional material with reversible changes in absorption or emission in response to variations in the external environment has great potential for achieving security printing.The information printed using such materials prepared"security ink"or"security paper"can only display by correct encrypted method,which greatly guarantees the safety of the information on the paper.Therefore,the development of stimuli-responsive materials with dynamically controllable response behaviors can effectively expand its application in the field of photonics,especially in the field of security printing.At present,examples on the regulation of response behavior by modifying the molecular structure of materials have been reported.However,these approaches often require complex synthesis and purification processes and cannot be dynamically controlled.In this thesis,based on dynamic ionic bonds,CVLSH-Zn-X complexes with different counter ions and CBTP-X with different halide anions were synthesized,respectively,and their application in secure printing has been realized.1.Regulation of photochromic response behavior of crystal violet lactone derivatives by counterions and its application in secure printingWe have designed and synthesized crystal violet lactone salicylaldehyde hydrazide?CVLSH?,and the CVLSH-Zn-X complex for controlling their reponse behavior on demand.As the basicity of the counter ion of the zinc salt increases,the inductive effect between the counter ion and Zn²⁺increases,causing the positive charge density around Zn²⁺to decrease,thereby reducing the inductive effect between the metal ion and the N atom.As the density increases,the energy required to stabilize the open-loop form also increases,and the slower the photochromic rate,thereby obtaining photochromic molecules with different coloring properties and coloring rates.Using the controllable photochromic properties of these zinc complexes,smart photochromic films,ASCII binary encryption were prepared and multi-level secure printing was successfully achieved.By changing the counter ion of the zinc salt,the dynamic control of the photochromic molecular behavior can be achieved.The process is simple,and the control strategy is convenient and efficient.2.Adjusting the photophysical properties of room temperature phosphorescent materials by counterions and its application in secure printingWe have designed and synthesized a series of?4-?9H-carbazol-9-yl?butyl?triphenylphosphine?CBTP?combined with different halide anions?Cl^-,Br^-and I^-?.Through regulating the counter ions of room-temperature phosphorescent materials,using the external heavy atom effect?EHE?,causes a significant increase in spin-orbit coupling?SOC?,thereby increasing the intersystem crossing?ISC?rate and realizing RTP with different luminescent properties.With the controllable luminescence properties of the complexes,security printing and doped white light emission applications have been realized.This project realizes the dynamic control of the luminescence behavior of room-temperature phosphorescent molecules by regulating the external heavy atoms of the ligand,the process is simple and efficient.