Positive and negative photochromic and fluorescent color-changing cotton fabrics for information switching and encryption

Cotton-based photochromic materials receive lots of attention due to their distinctive photoresponsivity and novel applications. Although many contributions have been devoted to this field, the color-changing effect and diversity still need to be improved. Herein, synchronous positive and negative photochromic and fluorescent color-changing smart textiles have been developed by applying spiropyran (SPOH) with a hydroxyl linking group to cotton fabrics through one-bath and coating methods, respectively. The negative photochromic cotton fabrics (NPCF) can promptly reach color saturation within 12 s and the photochromic property retention is 80 % after 15 color-changing cycles; the positive photochromic cotton fabrics (PPCF) will return to original color after 11 h under darkness and quickly fade under heating or green light. On this basis, we precisely designed positive and negative photochromic cotton fabrics (PNPCF) that can respond to both visible and ultraviolet (UV) light, and they also have fluorescent color-changing properties. In addition, photochromic cotton fabrics have potential applications in UV protection, pattern switching, information encryption and decryption. This research not only raises the value of cotton but also greatly enriches and expands the diversity of color-changing effects of photochromic cotton fabrics.