Hashimoto Shuichi, Uehara Ken, Sogawa Kazuhiro, Takada Mamiko, Fukumura Hiroshi
Department of Ecosystem Engineering, Graduate School of Engineering, The University of Tokushima, Tokushima-shi, Tokushima, 770-8506, Japan.
Phys Chem Chem Phys. 2006 Mar 28;8(12):1451-8. doi: 10.1039/b513832a. Epub 2006 Feb 23.
We measured the fluorescence decays and spectra of perylene adsorbed from solution into zeolite X crystals of 2-3 microm in diameter at the level of individual crystals by the application of a microscopy method coupled with a single photon counting apparatus and a multichannel spectrophotometer. We found that both decays and spectra are particle-dependent, i.e. a particle-to-particle difference was observed for the fluorescence decay curves at a fixed loading level along with a particle-dependent spectral change due to the various contribution of excimer emission band relative to those of three monomers. These findings are due to a non-homogeneous distribution which is confirmed by the various emission intensities of perylene-loaded zeolite crystals observed by fluorescence microscopy. Previously, a homogeneous distribution of the guest between zeolite crystals has been just taken for granted and not justified by experiment. The present result suggests that commonly employed collective measurements such as UV-VIS absorption and emission spectroscopies, IR and Raman spectroscopies, and NMR of bulk zeolite powders provide only averaged results and may sometimes suffer from acquiring precise molecular level pictures.
我们通过将显微镜方法与单光子计数装置和多通道分光光度计相结合，在单个晶体水平上测量了从溶液吸附到直径为2 - 3微米的X型沸石晶体中的苝的荧光衰减和光谱。我们发现衰减和光谱都与颗粒有关，即在固定负载水平下，荧光衰减曲线存在颗粒间差异，并且由于准分子发射带相对于三种单体发射带的不同贡献，光谱也存在颗粒依赖性变化。这些发现归因于非均匀分布，荧光显微镜观察到的负载苝的沸石晶体的不同发射强度证实了这一点。以前，人们一直理所当然地认为客体在沸石晶体之间是均匀分布的，且没有实验依据。目前的结果表明，常用的集体测量方法，如块状沸石粉末的紫外 - 可见吸收和发射光谱、红外和拉曼光谱以及核磁共振，只能提供平均结果，有时可能难以获得精确的分子水平图像。
