pH响应性双荧光聚合物纳米材料的制备和光学研究

Preparation and Optical Research of pH-responsive Dual Fluorescent Polymer Nanomaterials

本文采用四羟基四苯乙烯和4,4’-偶氮(4-氰基戊酸)酯化反应制得四苯乙烯偶氮引发剂,引发丙烯酸单体进行原位聚合,制备具有AIE特性的p H敏感聚合物TPE-tetraPAA,并进一步和稀土元素Eu(Ⅲ)配合制备具有AIE特性和双荧光的配合物TPE-tetraPAA-Eu(Ⅲ),该配合物通过共沉淀法可自组装形成尺寸为50nm左右的Pdots。该Pdots具有p H敏感性,在过酸或过碱时荧光强度都会降低,在弱碱性(pH=8)时荧光强度最高。通过XPS测试了各元素配位前后结合能的变化,结果表明Eu(Ⅲ)和羧基的O发生了配位,进一步通过FT-IR的测试结果证明了结构。通过分别测试浓度和不良溶剂对荧光强度的影响,该Pdots蓝色荧光强度随聚集程度增加而增强,表明该配合物的蓝色荧光发色团具有AIE性质。通过调节激发波长可以显著地观察到TPE-tetraPAA-Eu(Ⅲ)Pdots的双荧光性质,在标准色板上可以看出不同激发下的复合光的颜色从蓝光逐渐向红光移动。

Four-arm TPE-AZO initiators were prepared by the esterification of tetrahydroxytetraphenylethylene(TPE-tetraOH) and 4,4’-azo(4-cyanovaleric acid), then acrylic acid monomer was initiated in-situ polymerization to prepare pH-sensitive polymer TPE-tetraPAA with AIE characteristics, and further complexed with rare earth element Eu(Ⅲ) to prepare TPE-tetraPAA-Eu(Ⅲ) complex with dual-emission properties. The complex can be self-assembled to a size of about 50 nm Pdots by co-precipitation;the Pdots are p H-sensitive, the fluorescence intensity decreases when they are over-acidic or over-alkaline, the fluorescence intensity achieved highest when weak alkaline(pH=8) environments. The change of the binding energy before and after coordination of each element was tested by XPS, the results showed that the Eu(Ⅲ) and the carboxyl group were coordinated and the structure was further verified by the test results of FT-IR;the AIE characteristics of Pdots is measured by the fluorenscent effect of the concentration and the degree of aggregation on the fluorescence intensity, respectively. The intensity increases with aggregation and concentration increased, which indicates that the blue fluorescent chromophore of the complex has AIE characteristics;the dual emission properties of the Pdots can be observed significantly by adjusting the excitation wavelength, and the color of the composite under different excitations can be seen on a standard color plate, moving from blue to red emission.