Multiple Response Colors of Invisible Hollow Silica Photonic Crystals Patterns for Information Encoding

Abstract Combining responsive and invisible patterns into photonic crystals is an accepted encryption strategy for watermarking and information security. In order to fabricate an invisible pattern with excellent decrypted performance, environmental stability, full reversibility, and multiple responsive color, hollow silica photonic crystals (HSPCs) with selective wettability are fabricated by functional modification and photoinitiated Michael addition reaction. The patterned HSPCs show an identical purple color under a static environment, while they can reveal the hidden image with blue color and green color in response to water vapor flow and ethanol/water solutions, respectively. A large photonic bandgap shift (62 nm) is realized by glycerin wiping due to the large refractive index of glycerin. The prepared invisible PCs patterns show well reversibility in 100 cycles tests and maintain their excellent performances for more than 1 year. Such a multiple response invisible HSPCs patterns can play a crucial role in vapor sensing, information encoding, and anticounterfeiting application.