Molecular valves for colloidal growth of nanocrystal quantum dots: effect of precursor decomposition and intermediate sp
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Prospective Article
Molecular valves for colloidal growth of nanocrystal quantum dots: effect of precursor decomposition and intermediate species Sungjun Koh and Doh C. Lee, Department of Chemical and Biomolecular Engineering, KAIST Institute for the Nanocentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea Address all correspondence to Doh C. Lee at [email protected] (Received 31 May 2018; accepted 3 July 2018)
Abstract The ability to manipulate matter on the nanometer length scale is an important scientific goal, and the progress in the field of colloidal nanocrystal (NC) growth in the past decades has opened avenue for controlled synthesis of nanoscale materials with many unique physical properties that could enhance existing technologies or give rise to entirely new technologic applications. At the center of the progress is ever-increasing understanding on molecular interactions within colloidal synthesis, in which nucleation and growth each plays a critical role in the control of size, shape, morphology, and structure of NCs. Semiconductor NCs in quantum confinement regime, referred to as quantum dots (QDs), highlight the importance of such control over geometric parameters, since QDs exhibit size- and shape-dependent optical properties. In this paper, we demonstrate important aspects that govern QDs growth in the context of (i) precursor conversion chemistry, and (ii) intermediate species including molecular complex and clusters. Advances in understanding the growth chemistry of QDs have proved the significance of how precursors decompose and produce intermediate species. We review recent progress in regards to the synthetic chemistry of colloidal QDs and discuss our perspective on challenges and promises in the controlled large-scale synthesis of QDs.
Introduction Technologic breakthroughs across multiple fields are envisioned with nanocrystals (NCs), owing to the novel physicochemical properties of NCs uniquely suited for several existing or new technologies.[1–4] In particular, size-dependent optical properties of colloidal semiconductor NCs in quantum confinement regime, especially referred as quantum dots (QDs), show much promise in areas such as bio-imaging,[5,6] solar energy conversion,[7–10] photocatalysis,[11–14] laser, and display devices.[15–19] Wet chemical synthesis has become a mainstream protocol for the growth of QDs, because colloidal growth gives rise to relative ease in terms of scalability. At the core of wet chemical synthesis of QDs is arrested precipitation, where reactive molecular precursors decompose to form QDs in an organic solvent assisted by organic ligands bound at surface that effectively control the size of QDs.[18] A big breakthrough in this approach came in 1993 when Murray et al. reported the synthesis of CdE (E = S, Se, or Te) QDs by injecting dimethylcadmium and trioctylphosphine chalcogenides as precursors into a hot trioctylphosphine oxide.[20] Injection of the reactive precursors into the coordinating solvent at an elevated tem
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