Direct measurement of excitation energy relaxation processes in small domains by near field microspectroscopy

将扫描近场显微镜和单光子计数技术相结合，研制了皮秒时间分辨近场荧光显微光谱分析系统。该系统同时满足了100 nm的空间分辨率、50ps的时间分辨率和nm的光谱分辨率，是目前国内最先进的系统，目前只有少数几个实验室有类似的系统。该系统已应用于以下3种有机分子微晶。1.研究了沉积的四苯微晶的荧光光谱随晶体厚度的变化关系，发现晶体厚度为几十nm亚微米，晶体厚度越薄，缺陷浓度越低，荧光光谱越纯。2.通过测量表面形貌和荧光光谱，考察了菲-四氯苯酸酐电荷转移微晶的荧光不均匀性。从电子给体和受体分子的分离、给体-受体柱的取向、非发光缺陷的形成和杂质污染等方面讨论了与形貌有关或不相关的非荧光区。3.在-100 nm分辨率下，菲-四氯苯酸酐和均苯四甲酸酐的混合CT微晶呈现纤维状结构，其取向各向异性和空间不均匀性被考虑在内。

By combining a scanning near field microscope and a single photon counting technique, we have developed a picosecond time-resolved near field fluorescence microspectroscopy system. Spatial resolution of 100 nm, temporal resolution of 50 ps, and spectral resolution of nm are simultaneously satisfeied, which is the most advanced system in our country and only a few laboratories have comparable systems as far as we know. The system has been applied to the following 3 organic molecular microcrystals. 1.Fluorescence spectra of deposited tetracene microcrystals were examined as a function of the crystal thickness of a few tens nm - submum, and it was found that the thinner is purer with the lower defect concentration. 2.fluorescence inhomogeneity of anthracene-tetrachlorophthalic anhydride charge transfer microcrystals were examined by measuring topography and fluorescence spectrum. Nonfluorescence domains, which are related or not related to topography, were discussed in terms of segregation of electron donor and acceptor molecules, orientation of donor-acceptor column, nonluminescent defect formation, and impurity contamination. 3.Mixed CT microcrystals of anthracene-tetrachlorophthalic anhydride and -pyromelitic anhydride show fiber-like structures whose orientation anisotropy and spatial inhomogeneity were considered with -100 nm resolution.