Stimuli‐responsive photofunctional materials for green and security printing

Abstract Information recording on paper has always been the most important approach to keep records of human activity and to spread civilization. With the progress of science and technology, paper with different functions should be exploited to conform to the increasing demands in various scenarios. In one aspect, traditional paper can only be used once, and using large amounts of paper causes deforestation, additional solid waste treatment, environmental pollution, and high energy consumption. Consequently, the development of rewritable paper that is environment‐friendly, low cost, and can save resources is significant for green printing. In the other aspect, information leakage brings security issues, which may lead to severe consequences, such as war outbreak, economic loss, social problems, and so on. Therefore, the development of security printing has also attracted wide interests. Stimuli‐responsive photofunctional materials that have reversible variations in absorption or emission in response to changes in the external environmental have a great potential for the achievement of green and security printing. To date, much progress has been made in these research areas. This paper lists different smart materials that respond to various external stimuli, such as light, water, pH, heat, and metal ions, and summarizes the recent advances towards green and security printing. Also, we discuss the current challenges and future directions in this rapidly growing research field. It is expected that this review article will stimulate and guide future studies for the advanced green and security printing. image