报告题目：Novel properties of metal halide perovskite nanostructures: from quantum dots to chiral nanoclusters and carrier spin dynamics

报告嘉宾：张金中 加州大学圣克鲁斯分校 教授

报告时间：2025年7月21日 9:00

报告地点：williamhill中国官网中心校区唐敖庆楼B区521报告厅

主持人：邹勃

报告摘要

　　Size is a critical factor in determining properties of materials, both quantitatively and qualitatively. In our study of metal halide perovskite nanostructures, we found some interesting fundamental changes in properties when the size is varied from >4 nm for perovskite quantum dots (PQDs) to <2 nm for perovskite magic sized clusters (PMSCs) and even slightly smaller ligand-assisted metal halide molecular clusters (MHMCs) with much stronger quantum confinement effect (QCE), as exemplified by cesium lead bromide (CsPbBr3) and methylammonium lead bromide (CH3NH3PbBr3). Besides the expected blue shift in absorption and emission with decreasing size due to QCE, the photoluminescence quantum yield and excited state lifetime decrease generally with decreasing size, attributed 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 origin of the chirality include asymmetry induced by liquid-liquid or liquid-solid interfaces. Chiral nanoclusters are potentially useful for emerging technologies including spintronics and spin-optronics. Furthermore, we compare carrier spin dynamics of these nanostructures determined using ultrafast laser techniques and found major effects of size, phonon, nuclear spin, and surface in their lifetimes attributed to different spin relaxation mechanisms.

嘉宾简介

　　张金中，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和系主任。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450篇，出版专著4部。目前担任美国化学会(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高级编辑，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。

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