Abstract：
The microscopic structures of two amorphous molecular solids with extremely nonlinear optical properties have been studied. They consist of organotetrel chalcogenide clusters with the chemical formula [(RSn)4S6]. The basic molecular building blocks are adamantane-like {Sn4S6} cores with organic ligands R attached to the Sn atoms. While the material equipped with R=naphthyl generates frequency doubling upon irradiation with a simple infrared laser diode, the material decorated with R=phenyl responds by emitting brilliant white light. The structural differences were investigated using x-ray scattering and extended x-ray absorption fine structure combined with molecular Reverse Monte Carlo. Transmission electron microscopy and scanning precession electron diffraction were used to examine structural differences from mesoscopic down to microscopic scales. Characteristic differences were found on all scales. While close core-to-core distances between {Sn4S6} cluster cores and molecular distortions are found in the white light emitting material, undistorted molecules and significantly larger core distances characterize the material showing frequency doubling. Here however, results of scanning precession electron diffraction reveal the formation of nanocrystalline structures in the amorphous matrix, which we identify as cause for the suppression of white light emission.
摘要：
研究了两种具有极非线性光学性质的无定形分子固体的微观结构。它们由化学式为[(RSn)4S6]的有机etrel硫属化物簇组成。基本的分子结构单元是金刚烷状{Sn4S6}核，有机配体R连接到Sn原子上。虽然装有R=萘基的材料在用简单的红外激光二极管照射时会产生倍频，用R=苯基装饰的材料通过发出明亮的白光来响应。使用X射线散射和扩展X射线吸收精细结构结合分子反向蒙特卡罗研究了结构差异。透射电子显微镜和扫描进动电子衍射用于检查从介观到微观尺度的结构差异。在所有尺度上都发现了特征差异。虽然在白光发射材料中发现{Sn4S6}团簇核之间的核到核距离和分子畸变,未畸变的分子和明显更大的核心距离表征材料显示倍频。然而，在这里，扫描进动电子衍射的结果揭示了非晶基体中纳米晶体结构的形成，我们认为这是抑制白光发射的原因。
