Multiplexed stimuli-responsive molecules for high-security anti-counterfeiting applications

In the context of society's increasing reliance on information, improving the level of data security is not only a key task but also a formidable challenge. As such it is necessary and urgent to develop advanced technologies for high-security information encryption. Herein, we efficiently synthesized a novel indole dimer, which displayed multiple stimuli-driven, chromotropic capabilities. When triggered by acid/base, the color changes rapidly, accompanied by reversible changes in fluorescence. Interestingly, the color changes of the indole dimer were orthogonal to those of the traditionally utilized stimuli-responsive spiropyran. In combination, this allowed the preparation of invisible inks for printing, with security of information encrypted based on their diametrically opposed response to thermal and acid/base stimulation. The newly synthesized stimuli-responsive indole-dimer and the novel strategy of its application, in combination with the traditional stimuli-responsive spiropyran, provides a new direction in allowing high-level information security against forgery.