Time-resolved encryption from a spiropyran derivative: High-contrasted and multi-state mechanochromism, photochromism and thermochromism

Developing organic multi-stimuli responsive luminescent (OMSRL) materials in solid state has always been an arduous task. In this work, a simple spiropyran derivative (XG) is constructed, which exhibits excellent photochromism, thermochromism with exceptional reversible absorption/luminescence modulation ability after grinding. This new compound shows different photochromic and thermochromic characteristics under different grinding conditions. Furthermore, this new compound shows tunable dynamic photochromic and thermochromic characteristics due to the reversible isomerization of spiropyran molecule with excellent reversible absorption/luminescence modulation ability. More importantly, the color or emission can be modulated just by changing the time of external stimulation (ultraviolet stimulation, heating or grinding). This can be used not only to encrypt more rich information, but also to develop time-resolved multi-dimensional encryption or dynamic anti-counterfeiting advanced materials. This paper presents a new time-resolved encryption strategy based on this new compound, which provides important guidance for developing advanced information security materials.