主题:  From Impurities to Functionality-Controlled Dopant Migration Behavior in Nanocrystals主讲人:  郑伟威地点:  松江校区四号学院楼3083室时间:  2019-07-22 10:00:00组织单位:   化学化工与生物工程学院

报告人简介：

郑伟威博士，雪城大学（美国）化学系助理教授，博士生导师。郑伟威博士在复合纳米晶体为基础的多功能材料的合成，光电性质和催化上开展了系统地研究并做出了很多原创性成果。发表高质量SCI论文40余篇, 主要成果包括：在Mn掺杂的II-VI量子点中发现了表面载流子调制的铁磁耦合 (2011 JACS) 以及Cr掺杂的II-VI量子点中的相转化现象 (2012 JACS)；首次报道了Cr掺杂的ZnSe量子点，并发现了ZnSe量子点核中存在具有尖晶石结构的ZnCr2Se4包容物 (2012 JACS)；发展了一种灵敏的磁性探针，可用于检测量子点的表面、核及界面的微环境及晶格应力 (2012 Nano Lett.)。在水相体系获得了光学上最稳定的非核壳结构的量子点，并通过脂质体胶体模板实现了特定位置的选择性功能化 (2014 JACS)；首次报道了掺杂离子在纳米晶的可控迁移现象(2017 JACS)，并通过可控迁移精确控制材料的光学性能 (2017 ACS Nano)。开发了高效表面修饰路线以得到既有光电活性有在水相中超级稳定的无极钙钛矿量子点 (2018 Adv. Funct. Mater.)。 报告人的研究曾获得美国佛罗里达州立大学最佳博士学位论文奖(2012)，美国化学会ACS-PRF New Investigator Award (2019 - 2021)。

报告内容简介：

Semiconductor nanocrystals (NCs) with size-tunable luminescence are one of the most interesting materials capturing the interest of researchers over the past decades, and have broad applications in biological imaging, drug delivery, light-emitting devices, solar cells, photo-detectors, and quantum computing. Doping of transition metal ions into semiconductor NCs is a thriving area of nanomaterials because it can introduce new optical, electronic, and magnetic properties into host NCs. The physical properties of a doped NCs are strongly influenced by the dopant site inside the host lattice, which determines the host–dopant coupling from the overlap between the dopant and exciton wavefunctions of the host lattice.  

In our work, the effect of internal composition of the host NCs and temperature Mn(II) dopant behavior was studied. It was found that the dopant can migrate toward the local lattice sites with smaller cationic size mismatch between the dopant and host lattice, which is a thermodynamically driven process to minimize the lattice strain from the size mismatch. Controlling dopant site by migration offers a rigorous and rational approach to design functional NCs with unprecedented properties, and provides new fundamental understanding of dopant site-dependent properties of NCs.

撰写：陈娜