DFT-guided design and electrospinning construction of photochromic-fluorescent membrane for spatiotemporally resolved...

Spatiotemporally photoswitchable materials are urgently needed for high-security encryption, as conventional static systems are increasingly vulnerable. However, multifunctional photoresponsive materials often suffer from severe performance degradation due to inter-component crosstalk and restricted molecular isomerization in solid states. Herein, we develop a [SPO/PS]//[EuTp/PS] [(SPO = spirooxazine, PS = polystyrene, EuTp = tris(2-thenoyltrifluoroacetonato)(1,10-phenanthroline) europium (III)] Janus-nanofiber membrane via parallel electrospinning, which spatially segregates photochromic SPO and luminescent EuTp to enable synergia dual-mode responses without mutual interference. Density functional theory (DFT) calculations not only clarify the fundamental photochromic mechanism of SPO but also guide the material design. Photoinduced HOMO→LUMO transitions and closed-to-open ring isomerization drive reversible color switching, with the open-ring state exhibiting a narrowed bandgap (1.58 eV) and enhanced charge transfer. Fukui function analysis further identifies reactive sites that dictate stimuli-responsive reactivity of SPO, providing a theoretical basis for optimizing photoelectronic activity. The Janus heterostructure addresses two long-standing challenges: (1) eliminates competitive UV absorption between SPO and EuTp via spatial isolation, resolving the key issue of function quenching in mixed systems; (2) relieves solid-state stacking-induced suppression of SPO isomerization, restoring its intrinsic dynamic responsiveness. Based on these features, we demonstrate a spatiotemporally resolved multilevel encryption platform with independently controllable color and fluorescence signals. The membrane also exhibits linear temperature-dependent fluorescence for high-precision contactless thermometry. This work not only establishes a versatile material platform for optical encryption grounded in mechanistic DFT insights but also advances intelligent security systems toward higher safety thresholds and environmental adaptability.