Topic：Formation of Colloidal Semiconductor Magic-Sized Clusters
报 告 人 ：四川大学 余睽教授
报告摘要：Colloidal semiconductor quantum dots (QDs) have been acknowledged for potential applications in the areas such as bio-imaging/bio-labeling, light emitting diodes (LEDs), and solar cells. Recently, our laboratories have been focusing on the induction period which takes place prior to nucleation and growth of conventional M2En QDs, with M = Cu, Cd, Zn, Ge, Pb, and In, as well as E = S, Se, and Te. With E=P(C8H17)3 as the E precursor and additive H-Y molecules (Y = PPh2, OOCR, OR, SR, and NRH), we have concluded a general pathway, which is proton-mediated ligand exchange has been demonstrated for the evolution of monomers M2En. In this presentation, I would like to address our latest fundamental understanding on the formation of magic-size clusters (MSCs), which involves two step nucleation.[2,3] The first step of the liquid to solid phase transformation, namely the formation of “liquid-like” intermediates takes place in the induction period. When cationic (such as Cd2+) and anionic (such as Te2-)precursors were mixed with each other, “micellar-like” aggregates of ~ 1 nm in size were formed firstly followed by M-E covalent bonds. The resulting aggregates were “liquid-like” without a crystalline structure but a similar size of ~ 1 nm. A first order reaction kinetics was found for the second step, the evolution of CdS MSC-311 (with a sharp absorption peak at 311 nm) from its “liquid-like”immediate precursor IP-311 which has Cd-S bonds. The first order reaction kinetics can be accelerated by a small amount of CH3OH. Our study bring insights into the fundamental understanding of the relation between MSC and QD products, in addition to the low reaction yield of small-size QD products.
K. Yu, X. Liu, T. Qi, H. Yang, D. M. Whitfield, and C. Hu “General low temperature reaction pathway from precursors to monomers before nucleation of compound semiconductor nanocrystals” Nat. Commun. 2016, 7, 12223.
M. Liu, K. Wang, L. Wang, S. Han, H. Fan, N. Rowell, J. A. Ripmeester, R. Renoud, F. Bian, J. Zeng, and K. Yu “Probing Intermediates of the Induction Period Prior to Nucleation and Growth of Semiconductor Quantum Dots” Nature Commun. 2017, 8, 15467.
T. Zhu, B. Zhang, J. Zhang, J. Lu, H. Fan, N. Rowell, J. A. Ripmeester, S. Han, and K. Yu “Two-Step Nucleation of CdS Magic-Size Nanocluster MSC-311”. Chem. Mater. 2017, 29, 5727–5735.
余睽教授是ACS Applied Materials & Interfaces 执行主编。余睽教授 1998年在McGill University获博士学位，随后美国Sandia National Laboratory进行博士后研究，于2002年加入加拿大国家研究委员会，随后晋升为高级研究员。2014年回国，加入四川大学，并入选教育部“长江学者奖励计划”特聘教授。她的主要研究方向为胶体荧光半导体量子点，尤其在传统量子点的成核与成长的前过程以及魔尺寸纳米簇与量子点之间的关系等方面的研究取得突出成就。