Naphthopyran-Based Silica Nanoparticles as New High-Performance Photoresponsive Materials

详细信息    查看全文

• 作者：Tânia V. Pinto ; Paula Costa ; Céu M. Sousa ; Carlos A. D. Sousa ; Andreia Monteiro ; Clara Pereira ; Olívia Salomé G. P. Soares ; Carla S. M. Silva ; Manuel Fernando R. Pereira ; Paulo J. Coelho ; Cristina Freire
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：March 23, 2016
• 年：2016
• 卷：8
• 期：11
• 页码：7221-7231
• 全文大小：587K
• ISSN：1944-8252

文摘

Hybrid nanomaterials based on the covalent grafting of silylated naphthopyrans (NPTs) onto silica nanoparticles (SiO<sub>2sub> NPs) were successfully prepared and studied as new photochromic materials. They were prepared by a two-step protocol consisting of (i) NPTs (derivatives from 2H-naphtho[1,2-b]pyran (2H-NPT) and 3H-naphtho[2,1-b]pyran (3H-NPT)) silylation by a microwave-assisted reaction between hydroxyl-substituted NPTs and 3-(triethoxysilyl)propyl isocyanate, followed by (ii) covalent post-grafting onto SiO<sub>2sub> NPs. In order to study the role of the silylation step, the analogous non-silylated nanomaterials were also prepared by direct adsorption of NPTs. The characterization techniques confirmed the successful NPTs silylation and subsequent grafting to SiO<sub>2sub> NPs. All SiO<sub>2sub>-based nanomaterials revealed photoswitching behavior, following a biexponential decay. The SiO<sub>2sub> NPs functionalized with silylated 3H-NPTs (SiO<sub>2sub>@S3 and SiO<sub>2sub>@S4) presented the most promising photochromic properties, showing fast coloration/decoloration kinetics (coloring in 1 min under UV irradiation and fading in only 2 min) and high values of total color difference (ΔE*<sub>absub> = 30–50). Also, the 2H-NPTs-based SiO<sub>2sub> NPs (SiO<sub>2sub>@S1 and SiO<sub>2sub>@S2) presented fast coloration and good color contrasts (ΔE*<sub>absub> = 54), but slower fading kinetic rates, taking more than 2 h to return to their initial color. In contrast, the SiO<sub>2sub> NPs functionalized with non-silylated NPTs (SiO<sub>2sub>@1 and SiO<sub>2sub>@3) showed weaker color contrasts (ΔE*<sub>absub> = 6–10) and slower fading kinetics, proving that the NPT silylation step was crucial to enhance the photochromic behavior of SiO<sub>2sub> NPs based on NPTs. Furthermore, the silylated-based nanomaterials showed good photostability upon prolonged UV light exposure, keeping their photochromic performance unchanged for at least 12 successive UV/dark cycles, anticipating interesting technological applications in several areas.