Dual-Stimuli-Responsive Naphthalimide–Spiropyran Hybrids for Reversible Optical Printing and Multilevel Anticounterfeiting Applications

Abstract

Stimuli-responsive materials have attracted extensive attention in recent years due to their broad application prospects in data storage, drug release, sensing, and anticounterfeiting. In this study, a naphthalimide-conjugated spiropyran derivative (NSP) has been synthesized and characterized. NSP exhibits dual-stimuli-responsive properties of photochromism and mechanochromism. Due to its intramolecular charge transfer characteristics, the NSP solution demonstrates excellent photochromic behavior (a yellow-to-purple transition) and dual fluorescence switching characteristics (from yellow to orange-red emission). Under mechanical stimulation, the internal packing structure of the NSP powder is modified, endowing it with analogous reversible color-changing and fluorescence-switching capabilities. Furthermore, photochromic-functionalized cotton fabrics (PCF) capable of real-time dual optical signal output (color transition and fluorescence emission) have been fabricated using textile dyeing and finishing technology, demonstrating high color contrast/resolution, superior reversibility, and convenient multicolor patterning features. Leveraging this efficient and reversible photochromic behavior, we successfully demonstrate that PCF serves as an excellent material for rewritable optical printing and a multilevel anticounterfeiting material for dynamic information encryption.