Tungsten oxide quantum dot-based supramolecular assembly with tunable photochromic kinetics towards time-encoded anti-counterfeiting

The development of advanced anti-counterfeiting technology using photochromic inorganic materials with dynamic optical signals has garnered significant interest, but the limited color response and un-controlled photochromic kinetics largely restrict their practical application. In this work, we report the design of photochromic supramolecular assembly based on host-guest chemistry, enabling kinetics-tunable time-encoded anti-counterfeiting. By co-assembling of photochromic tungsten oxide quantum dots (WO₃ QDs) with cucurbit[7]uril (CB[7]), we developed a kinetics-tunable photochromic supramolecular assembly (WO_3-CB[7]). The WO_3-CB[7] assembly exhibits distinct photochromic kinetics compared to free WO₃ QDs due to efficient suppression of photogenerated decomposition of water adsorbed on WO₃ QDs, as verified by spectral and photophysical analysis. The photochromic kinetics can be readily modulated by adjusting the WO₃ QDs to CB[7] ratio. The kinetics-tunable photochromic WO_3-CB[7] assembly has been successfully applied as innovative anti-counterfeiting materials for fabricating time-encoded anti-counterfeiting arrays and information encryption system. The irradiation time serves as a key parameter for decrypting the final information, thereby enhancing the complexity of replication and counterfeiting. This approach offers a simple, scalable and generalizable strategy for designing advanced optical anti-counterfeiting materials by integrating inorganic photochromic materials with the supramolecular strategy.