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Ondry JC, Gupta A, Zhou Z, Chang JH, Talapin DV. Synthesis of Ternary and Quaternary Group III-Arsenide Colloidal Quantum Dots via High-Temperature Cation Exchange in Molten Salts: The Importance of Molten Salt Speciation. ACS Nano 2024; 18:858-873. [PMID: 38108289 DOI: 10.1021/acsnano.3c09490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Colloidal semiconductor nanocrystals are an important class of materials which have many desirable optoelectronic properties. In their bulk phases, gallium- and aluminum-containing III-V materials such as GaAs, GaP, and Al1-xGaxAs represent some of the most technologically important semiconductors. However, their colloidal synthesis by traditional methods is difficult due to the high temperatures needed to crystallize these highly covalent materials and the extreme reactivity of Ga- and Al- precursors toward organic solvents at such high temperatures. A recently developed paradigm shift in the synthesis of these materials is to use molten inorganic salts as solvents to prepare Ga- containing III-V colloidal nanocrystals by cation exchange of the corresponding indium pnictide (InPn) colloidal nanocrystals. There have been several successful applications of molten salt solvents to prepare III-phosphide colloidal nanocrystals. However, little is known about the nature of these reaction environments at the relevant reaction conditions and synthesis of III-arsenide colloidal nanocrystals remains challenging. Herein we report a detailed study on cation exchange of InPn nanocrystals using nominally Lewis basic molten salt solvents with added gallium halides. Surprisingly, these salt systems phase separate into two immiscible phases, and the nanocrystals preferentially segregate to one of the phases. Using a suite of in situ spectroscopy tools, we identify the phase the nanocrystals segregate to as Lewis neutral alkali tetrahalogallate molten salts. We apply in situ high-temperature Raman spectroscopy to identify the chemical species present in several molten salt compositions at experimentally relevant reaction conditions to elucidate a molecular basis for the reactivity observed. We then employ Lewis neutral KGaI4 molten salts to prepare high-quality In1-xGaxAs and In1-xGaxP nanocrystals and demonstrate that deviation from Lewis neutral conditions accelerate nanocrystal decomposition in the case of III-arsenide materials. Further, we expand to KAlI4-based molten salts to prepare In1-x-yGaxAlyAs nanocrystals which represent an example of solution-synthesized quaternary III-V nanocrystals. These insights provide a molecular basis for the rational development of molten salt solvents, thus allowing the preparation of a diverse array of multicomponent III-V colloidal nanocrystals.
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Affiliation(s)
- Justin C Ondry
- Department of Chemistry, James Franck Institute, and Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Aritrajit Gupta
- Department of Chemistry, James Franck Institute, and Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Zirui Zhou
- Department of Chemistry, James Franck Institute, and Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Jun Hyuk Chang
- Department of Chemistry, James Franck Institute, and Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Dmitri V Talapin
- Department of Chemistry, James Franck Institute, and Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
- Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Cao W, Yakimov A, Qian X, Li J, Peng X, Kong X, Copéret C. Surface Sites and Ligation in Amine-capped CdSe Nanocrystals. Angew Chem Int Ed Engl 2023; 62:e202312713. [PMID: 37869935 DOI: 10.1002/anie.202312713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/20/2023] [Accepted: 10/23/2023] [Indexed: 10/24/2023]
Abstract
Converting colloidal nanocrystals (NCs) into devices for various applications is facilitated by designing and controlling their surface properties. One key strategy for tailoring surface properties is thus to choose tailored surface ligands. In that context, amines have been universally used, with the goal to improve NCs synthesis, processing and performances. However, understanding the nature of surface sites in amine-capped NCs remains challenging, due to the complex surface compositions as well as surface ligands dynamic. Here, we investigate both surface sites and amine ligation in CdSe NCs by combining advanced NMR spectroscopy and computational modelling. Notably, dynamic nuclear polarization (DNP) enhanced 113 Cd and 77 Se 1D NMR helps to identify both bulk and surface sites of NCs, while 113 Cd 2D NMR spectroscopy enables to resolve amines terminated sites on both Se-rich and nonpolar surfaces. In addition to directly bonding to surface sites, amines are shown to also interact through hydrogen-bonding with absorbed water as revealed by 15 N NMR, augmented with computations. The characterization methodology developed for this work provides unique molecular-level insight into the surface sites of a range of amine-capped CdSe NCs, and paves the way to identify structure-function relationships and rational approaches towards colloidal NCs with tailored properties.
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Affiliation(s)
- Weicheng Cao
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093, Zürich, Switzerland
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Alexander Yakimov
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093, Zürich, Switzerland
| | - Xudong Qian
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Jiongzhao Li
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Xiaogang Peng
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Xueqian Kong
- Institute of Translational Medicine, Shanghai Jiao Tong University, Shanghai, 200240, China
- Department of Chemistry, Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou, 310058, China
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, 8093, Zürich, Switzerland
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Ondry JC, Frechette LB, Geissler PL, Alivisatos AP. Trade-offs between Translational and Orientational Order in 2D Superlattices of Polygonal Nanocrystals with Differing Edge Count. Nano Lett 2022; 22:389-395. [PMID: 34935383 DOI: 10.1021/acs.nanolett.1c04058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The goal of this work is to identify factors which modulate structural order in 2D self-assembled superlattices of polygon-shaped colloidal nanocrystals. Using combined experimental and simulation techniques, we quantify order in superlattices of hexagonal prism-shaped CdSe/CdS nanocrystals and cube-shaped CsPbBr3 nanocrystals. Superlattices derived from cube-shaped nanocrystals display less translational order compared to hexagonal prism-shaped nanocrystals both experimentally and in simulations. This effect can be attributed to geometric considerations inherent to the combined rotational and translational symmetries of different polygonal shapes and their superlattices. Cubes form a simple cubic lattice where nanocrystals can slide without steric overlap, whereas hexagonal prisms interlock, preventing translation. Regarding orientational order, cube assemblies display a narrower orientation distribution. Intuitively, hexagonal prisms are a more "spherical" shape compared to cubes. The results presented here outline a conceptual framework for identifying superlattice structures which favor translationally and orientationally ordered self-assembled superlattices.
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Affiliation(s)
- Justin C Ondry
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Kavli Energy NanoScience Institute, Berkeley, California 94720, United States
| | - Layne B Frechette
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Phillip L Geissler
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - A Paul Alivisatos
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Kavli Energy NanoScience Institute, Berkeley, California 94720, United States
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
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Giansante C. Surface Chemistry Impact on the Light Absorption by Colloidal Quantum Dots. Chemistry 2021; 27:14359-14369. [PMID: 34351015 PMCID: PMC8596982 DOI: 10.1002/chem.202102168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Indexed: 11/10/2022]
Abstract
At the size scale at which quantum confinement effects arise in inorganic semiconductors, the materials' surface-to-volume ratio is intrinsically high. This consideration sets surface chemistry as a powerful tool to exert further control on the electronic structure of the inorganic semiconductors. Among the materials that experience the quantum confinement regime, those prepared via colloidal synthetic procedures (the colloidal quantum dots - and wires and wells, too -) are prone to undergo surface reactions in the solution phase and thus represent an ideal framework to study the ensemble impact of surface chemistry on the materials' electronic structure. It is here discussed such an impact at the ground state by using the absorption spectrum of the colloidal quantum dots as a descriptor. The experiments show that the chemical species (the ligands) at the colloidal quantum dot surface induce changes to the optical band gap, the absorption coefficient at all wavelengths, and the ionization potential. These evidences point to a description of the colloidal quantum dot (the ligand/core adduct) as an indecomposable species, in which the orbitals localized on the ligands and the core mix in each other's electric field. This description goes beyond conventional models that conceive the ligands on the basis of pure electrostatic arguments (i. e., either as a dielectric shell or as electric dipoles) or as a mere potential energy barrier at the core boundaries.
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Affiliation(s)
- Carlo Giansante
- Carlo Giansante CNR NANOTEC, Istituto di NanotecnologiaVia Monteroni73100LecceItaly
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Moreels I. Let There Be Order, in Films of Colloidal CdSe 2D Nanocrystals. Nano Lett 2020; 20:2941-2942. [PMID: 32243174 DOI: 10.1021/acs.nanolett.0c01373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Progression from random orientation of 2D CdSe nanoplatelets to ordered close-packed thin films enables us to exploit the in-plane dipole moment of the band-edge transition on a macroscopic scale and gain control over the direction of charge and energy transport within the film. Momper et al. show how this can be achieved by tuning the solvent evaporation rate during deposition. They are able to switch from thermodynamically to kinetically controlled conditions for the film formation, resulting in ordered films with either face-down or edge-up alignment of the 2D nanoplatelets.
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Affiliation(s)
- Iwan Moreels
- Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
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