Gan Mengke, Xiao Tianliang, Liu Zhaoyue, Wang Yao
Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University Beijing 100191 P. R. China
Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University Guangzhou 510006 P. R. China
RSC Adv. 2019 Apr 23;9(22):12325-12330. doi: 10.1039/c9ra01480b. eCollection 2019 Apr 17.
Two-dimensional (2D) nanosheets are a class of fascinating host material that demonstrates a high specific surface area for the immobilization of functional molecules. Herein, we describe a layered photochromic film using montmorillonite 2D nanosheets immobilized with spiropyran units, which demonstrates a remarkable and reversible photochromic behavior. The synthesis of the layered photochromic film includes the intercalation and exfoliation of montmorillonite powders into 2D nanosheets using a spiropyran-modified surfactant and a subsequent vacuum filtration. The photochromic units of spiropyran-modified quaternary ammonium groups are immobilized on the surface of montmorillonite 2D nanosheets through an electrostatic interaction after exchanging with the native cations in montmorillonite during the intercalation and exfoliation. The photoisomerization of the spiropyran units between closed-ring spiropyran and open-ring merocyanine upon visible/UV irradiation contributes to the photochromic behavior of the layered film. The color contrast between the coloration and decoloration states of photochromic film is optimized by increasing the amount of spiropyran-modified cationic surfactant during the intercalation and exfoliation process. Our layered films with a visual photochromic behavior may promote their applications for optical data storage, optical switching and chemical sensing.
二维（2D）纳米片是一类引人入胜的主体材料，具有高比表面积，可用于固定功能分子。在此，我们描述了一种使用固定有螺吡喃单元的蒙脱石2D纳米片制成的层状光致变色薄膜，该薄膜表现出显著且可逆的光致变色行为。层状光致变色薄膜的合成包括使用螺吡喃改性表面活性剂将蒙脱石粉末插层和剥离成2D纳米片，以及随后的真空过滤。在插层和剥离过程中，螺吡喃改性季铵基团的光致变色单元在与蒙脱石中的天然阳离子交换后，通过静电相互作用固定在蒙脱石2D纳米片的表面。螺吡喃单元在可见光/紫外线照射下在闭环螺吡喃和开环部花青之间的光异构化导致了层状薄膜的光致变色行为。通过在插层和剥离过程中增加螺吡喃改性阳离子表面活性剂的用量，可以优化光致变色薄膜着色和褪色状态之间的颜色对比度。我们具有视觉光致变色行为的层状薄膜可能会促进其在光学数据存储、光开关和化学传感方面的应用。
