报告题目 (Title)：Size truly matters: some fundamental changes from metal halide perovskite quantum dots to magic sized clusters and ligand-assisted molecular clusters
报告人 (Speaker)：Jin Zhong Zhang 教授（University of California, Santa Cruz, USA）
报告时间 (Time)：2023年10月27日(周五) 9:00-11:00
报告地点 (Place)：上海大学宝山校区Ha102
邀请人(Inviter)：孙丽宁 教授
主办部门：理学院化学系
报告摘要：
Size is a critical factor in properties of materials. With change in size, both quantitative and qualitative changes can occur. In our study of metal halide perovskite nanostructures, we found some interesting fundamental changes in properties when the size changes from >4 nm for perovskite quantum dots (PQDs) to about 1.5 nm for perovskite magic sized clusters (PMSCs) and yet slightly smaller ligand-assisted metal halide molecular clusters (MHMCs) with much stronger quantum confinement effect (QCE), as exemplified by cesium lead bromide (CsPbBr3). Besides the expected blue shift in absorption and emission with decreasing size due to quantum confinement effect, the photoluminescence quantum yield and excited state lifetime decrease generally with decreasing size, possibly due to increased surface defects as well as changes in the electronic band structure with size. In addition, both the PMSCs and MHMCs are found to exhibit intrinsic chiral property based on circular dichroism (CD) spectra while the corresponding PQDs do not. Possible explanations for the observed CD in the clusters include twisted chiral layered structure, chiral defects or chiral octahedra from distortion induced by the larger percentage of surface ligands due to large surface-to-volume ratio of the smaller clusters compared to PQDs. Chiral clusters are potentially useful for emerging technologies including spintronics and spin-optotronics.
报告人简介：
Jin Zhong Zhang教授, 美国加州大学圣克鲁兹分校杰出教授。
1983年获上海复旦大学化学专业学士学位，1989年获西雅图华盛顿大学物理化学专业博士学位，1989年至1992年获在加州大学伯克利分校从事博士后研究。1992年加入加州大学圣克鲁斯分校（University of California, Santa Cruz），目前是该校化学和生物化学系的杰出教授。张教授近年来的研究领域集中在半导体、金属和金属氧化物纳米材料等先进材料的设计、合成、表征和应用，特别是在太阳能转换、固态照明、传感器和生物医学检测及治疗领域。目前，已经发表学术论文417篇，出版专著4部。自2004年起担任美国化学会JPC系列杂志副主编，现担任美国化学会(The American Chemical Society, ACS)出版的物理化学快报（Journal of Physical Chemistry Letters，JPCL）行政编辑和ACS Physical Chemistry Au副主编，目前是美国科学促进会（American Association for the Advancement of Science，AAAS)、美国物理学会（The American Physical Society, APS）、英国皇家化学学会 (Royal Society of Chemistry, RSC)和ACS的会士，还是2014年ACS能源和燃料部Richard A.Glenn奖的获得者。