A STUDY ON PHOTOCONVERSION BY THE USE OF ULTRATHIN ORGANIC FILMS WITH ASYMMETRIC SURFACES

以光合作用和视觉为代表的光生物学过程在生物膜中进行。生物膜的一个奇妙特性是在极薄的膜（约10 nm厚）上存在非对称表面.本研究通过将有机聚合物溶液浇铸在水表面上制备了极薄（25-60 nm）的聚合物膜，并发现了以下新的光化学性质. (1)在非对称表面的二次谐波产生（SHG）：供体-受体相互作用被成功地用于薄膜表面和石英衬底上的SHG。两亲性卟啉和紫罗碱可用于此目的。利用二次谐波研究阐明了吸附分子在表面的动力学行为。(2)有机薄膜的光化学电子传输：将含有给受体对的单层膜固定在电极表面，产生光电流。无论是金属卟啉或钌三联吡啶配合物是有用的供体，而紫精作为优良的受体。在三乙醇胺存在下，在金电极或ITO电极上观察到阳极光电流。(3)光声响应的超锡聚合物薄膜：超锡聚合物薄膜浸渍有有机染料，和斩波单色光从氙灯照射在无基板的聚合物薄膜。卟啉或偶氮化合物被用作染料。一个单一的膜是足够好的检测光声信号。对于一个给定的厚度的ultratin聚合物膜的相对灵敏度显着超过相同的聚合物的旋涂膜。

Photobiological processes, as represented by photosynthesis and vision, proceed in biological membranes. One of the marvelous properties of the biological membranes is the presence of asymmetric surfaces on extremely thin membranes (ca 10 nm in thickness).In the present study, extremely thin (25-60 nm) polymer membranes have been prepared by casting organic polymer solutions on water surface and the following new optochemical properties were discovered. (1) Second harmonic generation (SHG) at the asymmetric surface : Donor-acceptor interactions were successfully used for SHG at the thin membrane surfaces and also on quartz substrates. Amphiphilic porphyrins and viologens were useful for this purpose. Dynamic behaviors of adsorbed moleccules on the surface were elucidated by the SHG studies. (2) Photochemical electron-transport across thin organic films : Monolayr films, which contained donor-accceptor pairs, were fixed on electrode surface to generate photocurrents. Either metal porphyrin or ruthenium tris-bipyridine complex was useful as the donor, while viologen served as the excellent acceptor. Anodic photocurrents were observed on gold or ITO electrode in the pressence of triethanol amine in the aqueous solutions. (3) Photoacustic responses of ultrathin popymer films : The ultratin polymer films were impregnated with organic dyes, and chopped monochromatic light from a Xenon lamp was irradiated on the substrate-free polymer films. Either porphyrin or azo-compound was used as the dye. A single film was good enough to detect the photoacoustic signals. Relative sensitivity for a given thickness of the ultratin polymer film markedly exceeded that of spin coated film of the same polymer.