Photoswitchable WO₃₋ₓ QDs/Cu NCs Composite Films for Efficient UV Detection and Dual-Mode Anticounterfeiting

Photoswitchable fluorescent materials (PFMs) have attracted considerable attention due to the intrinsic advantages of non-contact operation, cleanliness, and non-invasiveness. Conventional PFMs always require complicated preparation processes with poor fluorescence switching properties, which are affected by the mechanisms of Föster resonance energy transfer (FRET) or photoinduced electron transfer (PET). The WO3-x QDs/Cu NCs composite films are prepared on different substrates by a solution casting method and displays outstanding fluorescence switching properties owing to the super photochromic performance of WO3-x QDs and aggregation-induced fluorescence of Cu NCs. The composite film exhibits reversible on/off switchable fluorescence under UV light irradiation and heat treatment based on the inner filter effect (IFE) mechanism. The composite film shows dynamic variations of the dual-mode signals, and the applications of UV sensing and anti-counterfeiting are analyzed. Sensitive dual-mode detection is realized in UV sensing, especially for UVB. The composite film has a dual-modal imaging capability with good reproducibility and high resolution for security information encryption and anti-counterfeiting. This work provides a novel strategy for fabricating advanced PFMs for multiple optical applications.