Dynamic Fluorescence Microprobe for Surface Analysis of Polymeric Materials

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We developed a time-resolved total internal reflection (TIR) fluorescence spectroscopy for surface analysis studies. Organic materials were contacted firmly to a sapphire plate whose refractive index is larger than that of the formers. A laser veam was lead to the sapphire under TIR condition and its evanescent wave penetrating into the material was used as an excitation light. The effective thickness of the interface layer excited is in the order of the excitation wavelength and even an information on the thickness of 100 <ang> was available under a specially selected condition. Monitoring fluorescence of these surface areas, we could elucidate their photophysical processes and molecular motions in the nanosecond picosecond time domains. Furthermore, we performed the present TIR fluorescence measurement under a fluorescence microscope, which enables us to obtain time- and space-resolved data on fluorescence characteristics. We call this methodology dynamic fluorescence microprobe and its characteristics are summarized as follows; (1) depth-resolution, 0.1 <micro> m, (2) two-dimensional resolution, 5 <micro> m, (3) time-resolution, 10 ps, and (4) wavelength resolution, 10 nm by using an interference filter.We applied this methodology to various polymeric and related materials. An information of the surface layer (15 nm) was extracted from the triple-layered organic films (265 nm), <pi> -electronic dopants have a lower concentration near the surface compared to the bulk, and dye in silk fabrics has a concentration gradient. These results indicate that structure and functional properties of organic materials should be elucidated as a function of the depth from the surface. The present dynamic fluorescence microprobe is the most a useful tool in this subject.