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Ultrafast photoresponses of organized molecular assemblies

有组织的分子组装体的超快光响应

基本信息

批准号：
08044137
负责人：
NAGAMURA Toshihiko
金额：
$ 3.71万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

The development of ultrafast photoresponsive materials and devices is essential for the near future implementation of all-optical information processing technology. One of the more promising approaches with respect to the above is the subject of the present project. It deals primarily with the construction and examination of ultrafast photoresponses of several organized molecular assemblies.1) Size-quantized CdS nano-particles were prepared in Nafion films, self-assembled films of amphiphiles, and other systems by reacting H_2S gas with Cd^<2+> ions dispersed, by ion-exchange. The size and the surface state of the CdS nano-particles were controlled by various treatments.2) Transient bleaching, by exciton formation, was studied with a fs pump-probe method excited at 400 nm. All samples except the LB films showed a very fast bleaching response on a time scale of less than 1 ps. The bleached spectra and their recovery rate depended markedly on the particle size and size distribution, the surface states, or the microenvironments. In Nafion films, the bleached spectra for "large" nano-particles (5 nm) were broad and the peaks red-shifted during the recovery process. For "small" nano-particles (3.4 nm), the peak of the bleached spectrum was at shorter wave-lengths and showed no spectral shift during the recovery process.3) Transient absorptions in the visible and the near infrared (NIR) regions appeared in less than 1 ps upon excitation of p-substituted styrylpyridinium tetraphenylborates. The decay in the visible region was composed of a fast and a slow component, whereas it was single exponential in the NIR region. The lifetime of the fast component in the visible region corresponded with that of the NIR absorption. The reverse electron transfer reaction from dimer radical cations to oxidized tetraphenylborate was found to be faster than that from monomer radicals.

超快光响应材料和器件的发展对于在不久的将来实现全光信息处理技术至关重要。在上述方面，较有希望的办法之一是本项目的主题。1)在Nafion膜、两亲分子自组装膜等体系中，通过离子交换，使H_2S气体与分散的Cd~(2+)和Gt~(2+)离子反应，制备出尺寸量化的纳米硫化镉。2)利用400 nm激发的飞秒泵浦-探测法研究了激子形成过程中的瞬时漂白。除LB膜外，所有样品在小于1ps的时间尺度上都表现出非常快的漂白响应。漂白光谱及其回收率明显依赖于颗粒的大小和分布、表面状态或微环境。在Nafion薄膜中，“大”纳米粒子(5 Nm)的漂白光谱较宽，并且在恢复过程中峰发生红移。对于较小的纳米粒子(3.4 nm)，漂白光谱的峰值位于较短的波长，并且在恢复过程中没有出现光谱漂移。3)对取代的四苯基硼基苯并吡啶激发后，在可见光和近红外(NIR)区域出现了不到1ps的瞬时吸收。可见光区的衰减由快分量和慢分量组成，而近红外区的衰减为单指数衰减。可见光区快成分的寿命与近红外吸收的寿命相对应。二聚体自由基阳离子与氧化型四苯基硼酸根的反向电子转移反应比单体自由基快。