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Thermochromic phase change materials have been widely studied for their importance in energy-efficient buildings, thermal control clothing, and low-temperature energy storage. Herein, we successfully designed and synthesized a spiropyran compound with negative photochromic properties in a solid matrix, 3-(3′,3′-dimethyl-6,8-dinitrospiro[chromene-2,2′-indolin]−1′-yl) propyl methacrylate (SPMA), as a thermochromic dye. The synthesized spiropyran was copolymerized with methyl methacrylate (MMA) using photoinitiation, and then n-octadecane was encapsulated by the copolymer to prepare reversible thermochromic phase change microcapsules (TC-microPCMs) through the solvent evaporation technique. The encapsulation efficiency of n-octadecane by copolymers prepared with different photoinitiator concentrations was also investigated. According to the results of SEM, particle size analysis (DLS), and DSC, the copolymer prepared at 3% concentration possessed the best encapsulation effect on n-octadecane, and the melting enthalpy of the microcapsules reached 168.7 J/g and the encapsulation ratio was 89.5%, which was not significantly different from that of microcapsules without the addition of thermochromic dyes. This di-functionalization process effectively avoids the "impurity effect" of dye addition. In addition, the homogeneous spherical structure and stable chemical composition of the microcapsules are the key factors to achieve a fully reversible thermochromic behavior. What's more, the functionalized film based on TC-microPCMs, TC-microPCMs@PVA, was used to explore the potential for applications in thermal storage and temperature sensing. The results demonstrated that the composite film has excellent reversible thermochromic performance, high latent heat storage performance, and good cycling durability, which make the bifunctional microcapsules highly promising candidates for thermal sensors, solar energy storage, and smart textiles. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A photochromic sponge for light-induced removal of Pb2+ from aqueous solution was developed by Steglich esterification. • The adsorption capacity of sponge to Pb2+ is 5.78 mg g−1. • The adsorption capacity and stripping efficiency of sponge can maintain over 85% and 94% after ten cycles. • The regeneration of exhausted sponge can be realized by simple rinsing under visible light conditions. Lead (Pb2+) is notorious for its negative effects on humans and the environment. Herein, a photochromic polyvinyl alcohol sponge (PVA-g-SPC) for light-induced removal of Pb2+ from aqueous solution was developed using 1′-(4′-carboxybutyl) −3′, 3′-dimethyl-6-nitro-spiro [chromene-2, 2′-indoline] (SPC) and polyvinyl alcohol sponge (PVA) by Steglich esterification. Evidence from experiments shows that the maximum adsorption capacity of PVA-g-MCC (formed by PVA-g-SPC under UV irradiation) was calculated to be 5.78 mg g−1 and the PVA-g-MCC has excellent selectivity to Pb2+ in the simulated lead–zinc mine leachate, ascribed to the complexation of MCC and Pb2+. Importantly, Pb2+ can be repelled from the sponge effectively by simple rinsing with water under visible light conditions to achieve the regeneration of the PVA-g-SPC with significant change of the colour in whole process, providing a facile method to determining the separation endpoints of Pb2+ by naked eyes and fully avoiding the secondary contamination caused by chemical desorbent. The adsorption capacity of PVA-g-SPC can maintain over 85% after ten cycles, indicating that the novel light-responsive sponge is a valuable material for Pb2+ removal. [ABSTRACT FROM AUTHOR]

The safe and efficient delivery of drugs is regarded as a fundamental strategy for enhancing the low effectiveness of cancer treatments. Herein, a simple preparation approach for a multifunctional drug delivery system was reported. The novel structure of spiropyran (SP), 1-(6 ´-bromo-hexyl)−3,3-dimethyl indoline-6 ´ -methoxy benzopyran, was used to modify sodium carboxymethyl cellulose (NaCMC) for controlling drug release. SP has a heightened sensitivity to variations in pH, with a linear response range of.2–5.5. The elevated drug loading (31.68 %) can be attributed to the hydrophobic interaction of SP and the adsorption of NaCMC. Porous materials composed of zinc ions and dimethylimidazole (ZIF-8) as an embedded shell, which serves as a barrier that effectively reduces drug leakage from 20 % to 12 %, thus mitigating the side effects of camptothecin (CPT) in alkaline conditions. In acidic conditions, the collapse of ZIF-8 provides zinc ions that act as crosslinking agents for NaCMC, thereby improving the channel of drug release and enhancing the release amount from 51.9 % to 66.7 % compared with SP-grafted NaCMC micelles. The inherent biological adhesion of NaCMC ensures sustained drug release for a period of up to 40 h. These pH-responsive carriers hold great promise in the safe and effective treatment of cancer in the gastrointestinal tract, with CPT emerging as a highly promising candidate. [Display omitted] • Synthesis of a new structure of spiropyran with high sensitivity and a wide response range to hydrogen ions. • The resulting SP-CMC micelles exhibited a high grafting efficiency and drug-loading capacity. • The incorporation of ZIF-8 prevents the early leakage of camptothecin to reduce the associated side effects of the drug. • Zinc ions provided by ZIF-8 improve the drug release amount and maintain good drug release performance for over 40 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • The solvatochromism of SPC is attributed to intramolecular hydrogen bonds. • Mcc showed a visualized, sensitive and selective response to Pb2+. • The complex Mcc - Pb2+ can stably exist under visible light conditions. • The established test strips can be applied for detection of Pb2+ in real samples. 1′-(4′-carboxybutyl) −3′, 3′-dimethyl-6-nitro-8-hydroxylspiro [chromene-2, 2′-indoline] (SPC) is a visual, selective, and sensitive detector to lead (Pb2+) ions. The presence of 8 -hydroxyl in pyran ring makes SPC have a remarkable solvatochromism in polar solvents (SPC can isomerize to the ring-opening body (Mcc) spontaneously under visible light conditions), ascribed to the formation of intramolecular hydrogen bonds. The color and spectrum of the Mcc solution could be changed instantly and significantly by addition of Pb2+, and Mcc showed excellent selectivity to Pb2+ in the simulated lead–zinc ore leachate. The complex Mcc - Pb2+, with a stoichiometry ratio of 1:1, can stably exist under visible light conditions, which is attributed to the interaction between Pb2+ and the deprotonated carboxy (–COO—), phenolic oxygen atom and 8-hydroxyl of the Mcc, and the whole process does not need UV irradiation, avoiding the serious photo-degradation of spiropyran derivatives. The low limit of detection (0.61 μM) and the established test strips indicate that SPC has the potential to be applied in the quantitative detection of Pb2+ in real samples. [ABSTRACT FROM AUTHOR]

How to detect and recover Cr(III) (Cr3+) from contaminated water through an economical and environmental way is not negligible but significant to solve serious pollution of heavy metal ions. Herein, a spiropyran [1′-(n -butyl)-3′,3′-dimethyl-6-nitrospir[chromene-2,2′-indoline] (SPBU) with negative photochromism is exploited as a visual detector for Cr3+. In contrast to positive photochromism of spiropyran derivatives, the synthesized SPBU can isomerize from colorless form spiropyran (SP) to the corresponding colored merocyanine (MC) form and further complex with Cr3+ under darkness without essential UV irradiation, providing a facile strategy enable visual detection of Cr3+ in aqueous solution. Importantly, we have synthesized SPBU-Polyethylene glyol (SPBU-PEG) hydrogels with negative photochromism via physical blending. Evidence from practical performance confirms that Cr3+ can be captured from aqueous solution under darkness and repelled from the hydrogel effectively upon visible light irradiation to achieve the regeneration of the designed adsorbent with a save-energy manner, avoiding any desorbent and secondary contamination. Additionally, the SPBU-PEG hydrogels have excellent Cr3+ selectivity and reproducibility. This work provides a significant greener way to exploit visible light responsive materials for reversible recovery of heavy metal ions from contaminated water with preferable performance, broadening sustainable development for purification systems. [Display omitted] • The SPBU has a low limit of detection for Cr3+ ions in aqueous solutions (0.64 μM). • The SPBU-PEG hydrogels used for the reversible light-driven recovery of Cr3+ ions. • SPBU-PEG hydrogels can be regenerated by light control. • The whole process avoids secondary pollution caused by chemical desorbents. [ABSTRACT FROM AUTHOR]