Dual‐Stimuli Chromogenic Membranes for Optical Security: Photochromic and Halochromic Anti‐Counterfeiting Applications

A dual‐stimuli chromogenic platform based on spiropyran‐functionalized anodic aluminum oxide (SP‐ t ‐AAO) membranes with reversible photochromic and halochromic switching is reported. Surface characterization by electronic images confirms the well‐preserved nanoporous morphology, while Energy‐disper...

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Published inSmall (Weinheim an der Bergstrasse, Germany) p. e07008
Main Authors Lee, Lin‐Ruei, Chen, Yi‐Fan, Fan, Po‐Xin, Lin, Yu‐Chun, Chang, Ming‐Hsuan, Liu, Yu‐Chun, Chang, Chun‐Chi, Chen, Jiun‐Tai
Format Journal Article
LanguageEnglish
Published Germany 04.08.2025
Subjects
spiropyran
anodic aluminum oxide (AAO)
anti‐counterfeiting
thiol‐yne chemistry
photochromism
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Summary:A dual‐stimuli chromogenic platform based on spiropyran‐functionalized anodic aluminum oxide (SP‐ t ‐AAO) membranes with reversible photochromic and halochromic switching is reported. Surface characterization by electronic images confirms the well‐preserved nanoporous morphology, while Energy‐dispersive X‐ray spectroscopy (EDS) scans reveal uniform grafting to micrometer depths. Grazing incidence X‐ray photoelectron spectroscopy (GIXPS) and time‐of‐flight secondary ion mass Spectrometry (TOF‐SIMS) further confirm successful surface chemical modification and pattern fidelity. Orthogonal functionalization is achieved via thiol‐yne chemistry and spatially controlled photopatterning using Chinese seasonal‐themed photomasks. Upon UV irradiation, the membrane exhibits a pale‐to‐magenta color change because of spiropyran‐merocyanine isomerization; acid exposure further switches the color from magenta to yellow. Both transitions are fully reversible under white light or base treatment. Video analysis reveals rapid halochromic switching kinetics (0.4–4 s), highlighting excellent optical responsiveness. The membrane also demonstrates the chelation toward heavy metal ions such as Cu 2+ and Fe 2+ . Moreover, thermal cycling test shows moderate durability, and a 20‐day ambient test confirms excellent chromogenic stability. This work offers high‐speed responsiveness, spatial precision, and long‐term stability for anti‐counterfeiting and sensing applications.
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ISSN:1613-6810
1613-6829
1613-6829
DOI:10.1002/smll.202507008