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Article

A Metal Ion-Responsive Spiropyran-Based Fluorescent Color-Changing Hydrogel

Key Laboratory of Synthetic and Biotechnology Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Materials 2025, 18(11), 2573; https://doi.org/10.3390/ma18112573 (registering DOI)
Submission received: 27 April 2025 / Revised: 21 May 2025 / Accepted: 22 May 2025 / Published: 30 May 2025
(This article belongs to the Special Issue Construction and Applications in Functional Polymers)

Abstract

The low fluorescence quantum efficiency of hydrophilic modified spiropyran in hydrogel matrices cannot be naturally improved during photoresponsive operation, which significantly limits their practical applications.In this study, a hybrid hydrogel system integrating metal plasmon resonance-enhanced fluorescence effects is designed through copolymerization of N,N'-bis(acryloyl)cystamine-modified Au nanoparticles (Au NPs), hydrophilic graft-modified spiropyran molecules, and N-isopropylacrylamide. This approach successfully achieves a spiropyran-based fluorescent hydrogel sensor with enhanced fluorescence intensity. Furthermore, an inverted pyramid-structured surface is engineered on the hydrogel using a template-assisted strategy, combining anti-reflection optical effects with plasmonic enhancement mechanisms. Molecular modification facilitated the integration of spiropyran and Au NPs into the hydrogel molecular chains, enhancing the dispersion of Au NPs within the hydrogel matrix and preventing fluorescence quenching from direct contact between Au NPs and spiropyran. Additionally, the anti-reflection effect of the hydrogel surface microstructure and the plasmon resonance effect of Au NPs were crucial in boosting the sensor’s fluorescence. Finally, the fluorescence intensity of the hydrogel increased by 10.2 times. In addition, under the action of excitation light, this sensor exhibited dual responsiveness of colorimetry and fluorescence, allowing for the sensing of heavy metal ions. The limit of detection for Zn2+ is as low as 0.803 μM, and the hydrogel exhibited more than 10 cycles of photo-isomerization and ion responsiveness.
Keywords: spiropyran; hydrogel; plasmon resonance; fluorescence enhancement; metal ions responsiveness spiropyran; hydrogel; plasmon resonance; fluorescence enhancement; metal ions responsiveness

Share and Cite

MDPI and ACS Style

Yin, Y.; Li, X.; Li, Y.; Miao, H.; Shi, G. A Metal Ion-Responsive Spiropyran-Based Fluorescent Color-Changing Hydrogel. Materials 2025, 18, 2573. https://doi.org/10.3390/ma18112573

AMA Style

Yin Y, Li X, Li Y, Miao H, Shi G. A Metal Ion-Responsive Spiropyran-Based Fluorescent Color-Changing Hydrogel. Materials. 2025; 18(11):2573. https://doi.org/10.3390/ma18112573

Chicago/Turabian Style

Yin, Yuxiu, Xin Li, Ying Li, Hongyan Miao, and Gang Shi. 2025. "A Metal Ion-Responsive Spiropyran-Based Fluorescent Color-Changing Hydrogel" Materials 18, no. 11: 2573. https://doi.org/10.3390/ma18112573

APA Style

Yin, Y., Li, X., Li, Y., Miao, H., & Shi, G. (2025). A Metal Ion-Responsive Spiropyran-Based Fluorescent Color-Changing Hydrogel. Materials, 18(11), 2573. https://doi.org/10.3390/ma18112573

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