光波导分光光谱技术研究染料分子在玻璃表面的吸附特性

Adsorption of Dye Molecules onto a Glass Surface Studied by Optical Waveguide Spectroscopy

光波导分光光谱技术利用光波导表面的消逝场敏感地测定有色物质亚单分子吸附层的偏振吸收光谱,非常适合于研究染料、颜料、荧光分子、量子点、金属纳米粒子、带色基的蛋白质等在固/液界面的吸附行为.本文使用宽频带卤钨灯、棱镜耦合的薄膜玻璃光波导和基于电荷耦合器件(CCD)的光谱分析仪设计制作了具有时间分辨本领的光波导分光光谱装置,并利用该装置实时监测了罗丹明6G(R6G)和亚甲基蓝(MB)在玻璃表面的吸附特性.通过比较在横电(TE)和横磁(TM)偏振模式下的吸收光谱,发现R6G主要以二聚体和单体的形式吸附在玻璃表面,而MB主要以多聚体的形式吸附在玻璃表面,并分别估算了它们的平均取向角.

Optical waveguide（OWG） absorption spectroscopy makes use of an evanescent field to detect the polarized absorption spectra of sub-monomolecular adlayers.This technique is suitable for the investigation of adsorption kinetics at the solid/liquid interface of dyes,pigments,fluorescent molecules,quantum dots,metallic nanoparticles,and proteins with chromophores.In this work,a time-resolved optical waveguide spectrometer was constructed using a tungsten-halogen lamp,a prism-coupled thin-film glass waveguide,and a charge-coupled device（CCD） spectral analyzer.The adsorption properties of rhodamine 6G（R6G） and methylene blue（MB） were investigated using this apparatus.By comparing the transverse electric（TE） and transverse magnetic（TM） polarized absorption spectra,the R6G molecules were found to adsorb onto the glass surface as monomers and dimers while MB adsorbed mostly as high-order aggregates.The average orientation angles of the adsorbed dye molecules were also estimated.