1
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Stam M, Almeida G, Ubbink RF, van der Poll LM, Vogel YB, Chen H, Giordano L, Schiettecatte P, Hens Z, Houtepen AJ. Near-Unity Photoluminescence Quantum Yield of Core-Only InP Quantum Dots via a Simple Postsynthetic InF 3 Treatment. ACS NANO 2024; 18:14685-14695. [PMID: 38773944 PMCID: PMC11155241 DOI: 10.1021/acsnano.4c03290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Revised: 05/06/2024] [Accepted: 05/15/2024] [Indexed: 05/24/2024]
Abstract
Indium phosphide (InP) quantum dots (QDs) are considered the most promising alternative for Cd and Pb-based QDs for lighting and display applications. However, while core-only QDs of CdSe and CdTe have been prepared with near-unity photoluminescence quantum yield (PLQY), this is not yet achieved for InP QDs. Treatments with HF have been used to boost the PLQY of InP core-only QDs up to 85%. However, HF etches the QDs, causing loss of material and broadening of the optical features. Here, we present a simple postsynthesis HF-free treatment that is based on passivating the surface of the InP QDs with InF3. For optimized conditions, this results in a PLQY as high as 93% and nearly monoexponential photoluminescence decay. Etching of the particle surface is entirely avoided if the treatment is performed under stringent acid-free conditions. We show that this treatment is applicable to InP QDs with various sizes and InP QDs obtained via different synthesis routes. The optical properties of the resulting core-only InP QDs are on par with InP/ZnSe/ZnS core-shell QDs, with significantly higher absorption coefficients in the blue, and with potential for faster charge transport. These are important advantages when considering InP QDs for use in micro-LEDs or photodetectors.
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Affiliation(s)
- Maarten Stam
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Guilherme Almeida
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Reinout F. Ubbink
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Lara M. van der Poll
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Yan B. Vogel
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Hua Chen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
| | - Luca Giordano
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000 Gent, Belgium
| | - Pieter Schiettecatte
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000 Gent, Belgium
| | - Zeger Hens
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000 Gent, Belgium
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The
Netherlands
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2
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Hai Y, Gahlot K, Tanchev M, Mutalik S, Tekelenburg EK, Hong J, Ahmadi M, Piveteau L, Loi MA, Protesescu L. Metal-Solvent Complex Formation at the Surface of InP Colloidal Quantum Dots. J Am Chem Soc 2024; 146:12808-12818. [PMID: 38668701 PMCID: PMC11082887 DOI: 10.1021/jacs.4c03325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/17/2024] [Accepted: 04/17/2024] [Indexed: 05/09/2024]
Abstract
The surface chemistry of colloidal semiconductor nanocrystals (QDs) profoundly influences their physical and chemical attributes. The insulating organic shell ensuring colloidal stability impedes charge transfer, thus limiting optoelectronic applications. Exchanging these ligands with shorter inorganic ones enhances charge mobility and stability, which is pivotal for using these materials as active layers for LEDs, photodetectors, and transistors. Among those, InP QDs also serve as a model for surface chemistry investigations. This study focuses on group III metal salts as inorganic ligands for InP QDs. We explored the ligand exchange mechanism when metal halide, nitrate, and perchlorate salts of group III (Al, In Ga), common Lewis acids, are used as ligands for the conductive inks. Moreover, we compared the exchange mechanism for two starting model systems: InP QDs capped with myristate and oleylamine as X- and L-type native organic ligands, respectively. We found that all metal halide, nitrate, and perchlorate salts dissolved in polar solvents (such as n-methylformamide, dimethylformamide, dimethyl sulfoxide, H2O) with various polarity formed metal-solvent complex cations [M(Solvent)6]3+ (e.g., [Al(MFA)6]3+, [Ga(MFA)6]3+, [In(MFA)6]3+), which passivated the surface of InP QDs after the removal of the initial organic ligand. All metal halide capped InP/[M(Solvent)6]3+ QDs show excellent colloidal stability in polar solvents with high dielectric constant even after 6 months in concentrations up to 74 mg/mL. Our findings demonstrate the dominance of dissociation-complexation mechanisms in polar solvents, ensuring colloidal stability. This comprehensive understanding of InP QD surface chemistry paves the way for exploring more complex QD systems such as InAs and InSb QDs.
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Affiliation(s)
- Yun Hai
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
| | - Kushagra Gahlot
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
| | - Mark Tanchev
- Institute
of Chemistry and Chemical Engineering, École
Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Suhas Mutalik
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
| | - Eelco K. Tekelenburg
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
| | - Jennifer Hong
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
| | - Majid Ahmadi
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
| | - Laura Piveteau
- Institute
of Chemistry and Chemical Engineering, École
Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Maria Antonietta Loi
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
| | - Loredana Protesescu
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, Groningen, 9747AG, The Netherlands
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3
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Calvin JJ, Brewer AS, Crook MF, Kaufman TM, Alivisatos AP. Observation of negative surface and interface energies of quantum dots. Proc Natl Acad Sci U S A 2024; 121:e2307633121. [PMID: 38648471 PMCID: PMC11067453 DOI: 10.1073/pnas.2307633121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 03/21/2024] [Indexed: 04/25/2024] Open
Abstract
Surface energy is a fundamental property of materials and is particularly important in describing nanomaterials where atoms or molecules at the surface constitute a large fraction of the material. Traditionally, surface energy is considered to be a positive quantity, where atoms or molecules at the surface are less thermodynamically stable than their counterparts in the interior of the material because they have fewer bonds or interactions at the surface. Using calorimetric methods, we show that the surface energy is negative in some prototypical colloidal semiconductor nanocrystals, or quantum dots with organic ligand coatings. This implies that the surface atoms are more thermodynamically stable than those on the interior due to the strong bonds between these atoms and surfactant molecules, or ligands, that coat their surface. In addition, we extend this work to core/shell indium phosphide/zinc sulfide nanocrystals and show that the interfacial energy between these materials is highly thermodynamically favorable in spite of their large lattice mismatch. This work challenges many of the assumptions that have guided thinking about colloidal nanomaterial thermodynamics, investigates the fundamental stability of many technologically relevant colloidal nanomaterials, and paves the way for future experimental and theoretical work on nanocrystal thermodynamics.
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Affiliation(s)
- Jason J. Calvin
- Department of Chemistry, University of California, Berkeley, CA94720
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Amanda S. Brewer
- Department of Chemistry, University of California, Berkeley, CA94720
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Michelle F. Crook
- Department of Chemistry, University of California, Berkeley, CA94720
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Tierni M. Kaufman
- Department of Chemistry, University of California, Berkeley, CA94720
| | - A. Paul Alivisatos
- Department of Chemistry, University of California, Berkeley, CA94720
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
- Department of Materials Science and Engineering, University of California, Berkeley, CA94720
- Kavli Energy NanoScience Institute, University of California, Berkeley, CA94720
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4
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Liu M, Tang G, Liu Y, Jiang FL. Ligand Exchange of Quantum Dots: A Thermodynamic Perspective. J Phys Chem Lett 2024; 15:1975-1984. [PMID: 38346356 DOI: 10.1021/acs.jpclett.3c03413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Colloidal quantum dots (QDs) consist of an inorganic core and organic surface ligands. Surface ligands play a dominant role in maintaining the colloidal stability of QDs and passivating the surface defects of QDs. However, the original ligands introduced in the synthetic process of QDs cannot meet the requirements for diverse applications; therefore, ligand exchanges with functional ligands are mandatory. Understanding the ligand exchange process requires a comprehensive combination of the concepts and techniques of surface chemistry. In this Perspective, the ligand exchange process is discussed in detail. Specifically, we elaborate on the thermodynamics that can reveal the feasibility and mechanism of ligand exchange. It depicts a critical physical picture of the surface of QDs along with the following ligand exchange.
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Affiliation(s)
- Meng Liu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China
| | - Ge Tang
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China
| | - Yi Liu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Chemistry, Tiangong University, Tianjin 300387, P. R. China
| | - Feng-Lei Jiang
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China
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5
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Eagle F, Harvey S, Beck R, Li X, Gamelin DR, Cossairt BM. Enhanced Charge Transfer from Coinage Metal Doped InP Quantum Dots. ACS NANOSCIENCE AU 2023; 3:451-461. [PMID: 38144703 PMCID: PMC10740119 DOI: 10.1021/acsnanoscienceau.3c00029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 08/24/2023] [Accepted: 08/25/2023] [Indexed: 12/26/2023]
Abstract
This paper describes coinage-metal-doped InP quantum dots (QDs) as a platform for enhanced electron transfer to molecular acceptors relative to undoped QDs. A synthetic strategy is developed to prepare doped InP/ZnSe QDs. First-principles DFT calculations show that Ag+ and Cu+ dopants localize photoexcited holes while leaving electrons delocalized. This charge carrier wave function modulation is leveraged to enhance electron transfer to molecular acceptors by up to an order of magnitude. Examination of photoluminescence quenching data suggests that larger electron acceptors, such as anthraquinone and methyl viologen, bind to the QD surface in two ways: by direct adsorption to the surface and by adsorption following displacement of a weakly bound surface cation-ligand complex. Reactions with larger acceptors show the greatest increases in electron transfer between doped and undoped quantum dots, while smaller acceptors show smaller enhancements. Specifically, benzoquinone shows the smallest, followed by naphthoquinone and then methyl viologen and anthraquinone. These results demonstrate the benefits of dopant-induced excited-state carrier localization on photoinduced charge transfer and highlight design principles for improved implementation of quantum dots in photoredox catalysis.
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Affiliation(s)
- Forrest
W. Eagle
- Department of Chemistry, University
of Washington, Seattle, Washington 98195-1700, United States
| | - Samantha Harvey
- Department of Chemistry, University
of Washington, Seattle, Washington 98195-1700, United States
| | - Ryan Beck
- Department of Chemistry, University
of Washington, Seattle, Washington 98195-1700, United States
| | - Xiaosong Li
- Department of Chemistry, University
of Washington, Seattle, Washington 98195-1700, United States
| | - Daniel R. Gamelin
- Department of Chemistry, University
of Washington, Seattle, Washington 98195-1700, United States
| | - Brandi M. Cossairt
- Department of Chemistry, University
of Washington, Seattle, Washington 98195-1700, United States
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6
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Yuan C, He M, Liao X, Liu M, Zhang Q, Wan Q, Qu Z, Kong L, Li L. Interface defects repair of core/shell quantum dots through halide ion penetration. Chem Sci 2023; 14:13119-13125. [PMID: 38023521 PMCID: PMC10664535 DOI: 10.1039/d3sc04136k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 10/31/2023] [Indexed: 12/01/2023] Open
Abstract
The interface defects of core-shell colloidal quantum dots (QDs) affect their optoelectronic properties and charge transport characteristics. However, the limited available strategies pose challenges in the comprehensive control of these interface defects. Herein, we introduce a versatile strategy that effectively addresses both surface and interface defects in QDs through simple post-synthesis treatment. Through the combination of fine chemical etching methods and spectroscopic analysis, we have revealed that halogens can diffuse within the crystal structure at elevated temperatures, acting as "repairmen" to rectify oxidation and significantly reducing interface defects within the QDs. Under the guidance of this protocol, InP core/shell QDs were synthesized by a hydrofluoric acid-free method with a full width at half-maximum of 37.0 nm and an absolute quantum yield of 86%. To further underscore the generality of this strategy, we successfully applied it to CdSe core/shell QDs as well. These findings provide fundamental insights into interface defect engineering and contribute to the advancement of innovative solutions for semiconductor nanomaterials.
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Affiliation(s)
- Changwei Yuan
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 P. R. China
| | - Mengda He
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 P. R. China
| | - Xinrong Liao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 P. R. China
| | - Mingming Liu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 P. R. China
| | - Qinggang Zhang
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 P. R. China
| | - Qun Wan
- Macao Institute of Materials Science and Engineering (MIMSE), Macau University of Science and Technology Taipa Macao 999078 P. R. China
| | - Zan Qu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 P. R. China
| | - Long Kong
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 P. R. China
| | - Liang Li
- Macao Institute of Materials Science and Engineering (MIMSE), Macau University of Science and Technology Taipa Macao 999078 P. R. China
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7
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Muhammad, Choi D, Parmar DH, Rehl B, Zhang Y, Atan O, Kim G, Xia P, Pina JM, Li M, Liu Y, Voznyy O, Hoogland S, Sargent EH. Halide-Driven Synthetic Control of InSb Colloidal Quantum Dots Enables Short-Wave Infrared Photodetectors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2306147. [PMID: 37734861 DOI: 10.1002/adma.202306147] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 09/13/2023] [Indexed: 09/23/2023]
Abstract
In the III-V family of colloidal quantum dot (CQD) semiconductors, InSb promises access to a wider range of infrared wavelengths compared to many light-sensing material candidates. However, achieving the necessary size, size-dispersity, and optical properties has been challenging. Here the synthetic challenges associated with InSb CQDs are investigated and it is found that uncontrolled reduction of the antimony precursor hampers the controlled growth of CQDs. To overcome this, a synthetic strategy that combines nonpyrophoric precursors with zinc halide additives is developed. The experimental and computational studies show that zinc halide additives decelerate the reduction of the antimony precursor, facilitating the growth of more uniformly sized CQDs. It is also found that the halide choice provides additional control over the strength of this effect. The resultant CQDs exhibit well-defined excitonic transitions in spectral range of 1.26-0.98 eV, along with strong photoluminescence. By implementing a postsynthesis ligand exchange, colloidally stable inks enabling the fabrication of high-quality CQD films are achieved. The first demonstration of InSb CQD photodetectors is presented reaching 75% external quantum efficiency (QE) at 1200 nm, to the knowledge the highest short-wave infrared (SWIR) QE reported among heavy-metal-free infrared CQD-based devices.
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Affiliation(s)
- Muhammad
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Dongsun Choi
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Darshan H Parmar
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Benjamin Rehl
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Yangning Zhang
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Ozan Atan
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Gahyeon Kim
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
- Department of Chemistry, Korea University, Seoul, 02841, Republic of Korea
| | - Pan Xia
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Joao M Pina
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Mengsha Li
- Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario, M5S 3E4, Canada
| | - Yanjiang Liu
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
- Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario, M5S 3E4, Canada
| | - Oleksandr Voznyy
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada
| | - Sjoerd Hoogland
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Edward H Sargent
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
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8
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Liu J, Yue S, Zhang H, Wang C, Barba D, Vidal F, Sun S, Wang ZM, Bao J, Zhao H, Selopal GS, Rosei F. Efficient Photoelectrochemical Hydrogen Generation Using Eco-Friendly "Giant" InP/ZnSe Core/Shell Quantum Dots. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37433096 DOI: 10.1021/acsami.3c04900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/13/2023]
Abstract
InP quantum dots (QDs) are promising building blocks for use in solar technologies because of their low intrinsic toxicity, narrow bandgap, large absorption coefficient, and low-cost solution synthesis. However, the high surface trap density of InP QDs reduces their energy conversion efficiency and degrades their long-term stability. Encapsulating InP QDs into a wider bandgap shell is desirable to eliminate surface traps and improve optoelectronic properties. Here, we report the synthesis of "giant" InP/ZnSe core/shell QDs with tunable ZnSe shell thickness to investigate the effect of the shell thickness on the optoelectronic properties and the photoelectrochemical (PEC) performance for hydrogen generation. The optical results demonstrate that ZnSe shell growth (0.9-2.8 nm) facilitates the delocalization of electrons and holes into the shell region. The ZnSe shell simultaneously acts as a passivation layer to protect the surface of InP QDs and as a spatial tunneling barrier to extract photoexcited electrons and holes. Thus, engineering the ZnSe shell thickness is crucial for the photoexcited electrons and hole transfer dynamics to tune the optoelectronic properties of "giant" InP/ZnSe core/shell QDs. We obtained an outstanding photocurrent density of 6.2 mA cm-1 for an optimal ZnSe shell thickness of 1.6 nm, which is 288% higher than the values achieved from bare InP QD-based PEC cells. Understanding the effect of shell thickness on surface passivation and carrier dynamics offers fundamental insights into the suitable design and realization of eco-friendly InP-based "giant" core/shell QDs toward improving device performance.
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Affiliation(s)
- Jiabin Liu
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
| | - Shuai Yue
- Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, P. R. China
| | - Hui Zhang
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
| | - Chao Wang
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
| | - David Barba
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
| | - François Vidal
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
| | - Shuhui Sun
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
| | - Zhiming M Wang
- Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, P. R. China
- Institute for Advanced Study, Chengdu University, Chengdu, Sichuan 610106, P. R. China
| | | | - Haiguang Zhao
- State Key Laboratory of Bio-Fibers and Eco-Textiles & College of Physics, University-Industry Joint Center for Ocean Observation and Broadband Communication, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, P. R. China
| | - Gurpreet Singh Selopal
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
- Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, P. R. China
- Department of Engineering, Faculty of Agriculture, Dalhousie University, Truro, Nova Scotia B2N 5E3, Canada
| | - Federico Rosei
- Centre Énergie Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boul. Lionel Boulet, Varennes, Quebec J3X 1P7, Canada
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9
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Mahmood AU, Rizvi MH, Tracy JB, Yingling YG. Solvent Effects in Ligand Stripping Behavior of Colloidal Nanoparticles. ACS NANO 2023. [PMID: 37311219 DOI: 10.1021/acsnano.3c01313] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Inorganic colloidal nanoparticle (NP) properties can be tuned by stripping stabilizing ligands using a poor solvent. However, the mechanism behind ligand stripping is poorly understood, in part because in situ measurements of ligand stripping are challenging at the nanoscale. Here, we investigate ethanol solvent-mediated oleylamine ligand stripping from magnetite (Fe3O4) NPs in different compositions of ethanol/hexane mixtures using atomistic molecular dynamics (MD) simulations and thermogravimetric analysis (TGA). Our study elucidates a complex interplay of ethanol interactions with system components and indicates the existence of a threshold concentration of ∼34 vol % ethanol, above which ligand stripping saturates. Moreover, hydrogen bonding between ethanol and stripped ligands inhibits subsequent readsorption of the ligands on the NP surface. A proposed modification of the Langmuir isotherm explains the role of the enthalpy of mixing of the ligands and solvents on the ligand stripping mechanism. A good agreement between the MD predictions and TGA measurements of ligand stripping from Fe3O4 NPs validates the simulation observations. Our findings demonstrate that the ligand coverage of NPs can be controlled by using a poor solvent below the threshold concentration and highlight the importance of ligand-solvent interactions that modulate the properties of colloidal NPs. The study also provides an approach for a detailed in silico study of ligand stripping and exchange from colloidal NPs that are crucial for applications of NPs spanning self-assembly, optoelectronics, nanomedicine, and catalysis.
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Affiliation(s)
- Akhlak U Mahmood
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Mehedi H Rizvi
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Joseph B Tracy
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Yaroslava G Yingling
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
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10
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Elimelech O, Oded M, Harries D, Banin U. Spontaneous Patterning of Binary Ligand Mixtures on CdSe Nanocrystals: From Random to Janus Packing. ACS NANO 2023; 17:5852-5860. [PMID: 36893308 PMCID: PMC10061916 DOI: 10.1021/acsnano.2c12676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 03/01/2023] [Indexed: 06/18/2023]
Abstract
Binary compositions of surface ligands are known to improve the colloidal stability and fluorescence quantum yield of nanocrystals (NCs), due to ligand-ligand interactions and surface organization. Herein, we follow the thermodynamics of a ligand exchange reaction of CdSe NCs with alkylthiol mixtures. The effects of ligand polarity and length difference on ligand packing were investigated using isothermal titration calorimetry (ITC). The thermodynamic signature of the formation of mixed ligand shells was observed. Correlating the experimental results with thermodynamic mixing models has allowed us to calculate the interchain interactions and to infer the final ligand shell configuration. Our findings demonstrate that, in contrast to macroscopic surfaces, the small dimensions of the NCs and the subsequent increased interfacial region between dissimilar ligands allow the formation of a myriad of clustering patterns, controlled by the interligand interactions. This work provides a fundamental understanding of the parameters determining the ligand shell structure and should help guide smart surface design toward NC-based applications.
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Affiliation(s)
- Orian Elimelech
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Meirav Oded
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Daniel Harries
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- The
Fritz Haber Center, The Hebrew University
of Jerusalem, Jerusalem 9190401, Israel
| | - Uri Banin
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
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11
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Burkitt-Gray M, Casavola M, Clark PCJ, Fairclough SM, Flavell WR, Fleck RA, Haigh SJ, Ke JCR, Leontiadou M, Lewis EA, Osiecki J, Qazi-Chaudhry B, Vizcay-Barrena G, Wichiansee W, Green M. Structural investigations into colour-tuneable fluorescent InZnP-based quantum dots from zinc carboxylate and aminophosphine precursors. NANOSCALE 2023; 15:1763-1774. [PMID: 36601869 DOI: 10.1039/d2nr02803d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Fluorescent InP-based quantum dots have emerged as valuable nanomaterials for display technologies, biological imaging, and optoelectronic applications. The inclusion of zinc can enhance both their emissive and structural properties and reduce interfacial defects with ZnS or CdS shells. However, the sub-particle distribution of zinc and the role this element plays often remains unclear, and it has previously proved challenging to synthesise Zn-alloyed InP-based nanoparticles using aminophosphine precursors. In this report, we describe the synthesis of alloyed InZnP using zinc carboxylates, achieving colour-tuneable fluorescence from the unshelled core materials, followed by a one-pot ZnS or CdS deposition using diethyldithiocarbamate precursors. Structural analysis revealed that the "core/shell" particles synthesised here were more accurately described as homogeneous extended alloys with the constituent shell elements diffusing through the entire core, including full-depth inclusion of zinc.
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Affiliation(s)
- Mary Burkitt-Gray
- Department of Physics, King's College London, The Strand, London, WC2R 2LS, UK.
- Centre for Ultrastructural Imaging, King's College London, New Hunt's House, London, SE1 1UL, UK
| | - Marianna Casavola
- Department of Physics, King's College London, The Strand, London, WC2R 2LS, UK.
| | - Pip C J Clark
- The Photon Science Institute, School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester, M13 9PL, UK
| | - Simon M Fairclough
- Department of Physics, King's College London, The Strand, London, WC2R 2LS, UK.
| | - Wendy R Flavell
- The Photon Science Institute, School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester, M13 9PL, UK
| | - Roland A Fleck
- Centre for Ultrastructural Imaging, King's College London, New Hunt's House, London, SE1 1UL, UK
| | - Sarah J Haigh
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Jack Chun-Ren Ke
- The Photon Science Institute, School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester, M13 9PL, UK
| | - Marina Leontiadou
- The Photon Science Institute, School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester, M13 9PL, UK
| | - Edward A Lewis
- Department of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Jacek Osiecki
- MAX IV Laboratory, Lund University, Box 118, 221 00 Lund, Sweden
| | - Basma Qazi-Chaudhry
- Department of Physics, King's College London, The Strand, London, WC2R 2LS, UK.
| | - Gema Vizcay-Barrena
- Centre for Ultrastructural Imaging, King's College London, New Hunt's House, London, SE1 1UL, UK
| | - Wijittra Wichiansee
- Department of Physics, King's College London, The Strand, London, WC2R 2LS, UK.
| | - Mark Green
- Department of Physics, King's College London, The Strand, London, WC2R 2LS, UK.
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12
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Zhou X, Pang Z, Cao W, Cao Z, Zhu J, Qi Y, Peng X, Kong X. Diffusion NMR for Measuring Dynamic Ligand Exchange on Colloidal Nanocrystals. Anal Chem 2023; 95:792-801. [PMID: 36520837 DOI: 10.1021/acs.analchem.2c02964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Ligand exchange is fundamentally related to the surface chemistry of nanoparticles in solution and is also an essential procedure for their synthesis and solution processing. The solution of ligand-bearing nanoparticles can be regarded as a dynamic equilibrium of bound and free ligands depending on the concentration and temperature. The direct experimental calibration of the ligand exchange dynamics relies on the in situ and real-time quantification of bound and free ligands. However, existing analytical strategies are often with limited applicability considering the requirement of special functional groups or the indirect detection of photoluminescence or reaction heat. In this work, we explore diffusion-based methods of solution-state nuclear magnetic resonance (NMR) as a general strategy to probe ligand exchange. Using comprehensive numerical simulations, we show that diffusion NMR with designable time sequences can effectively distinguish bound and free ligands and measure the exchange rate constants from 0.5 to 200 s-1 under typical instrumental settings. These methods are demonstrated experimentally on colloidal CdSe nanocrystal systems with carboxylate or amine ligands whose exchange rates were previously undetectable. The kinetic rate constants, activation energies, and thermodynamic parameters of ligand exchange have been obtained under variable temperature conditions. We expect the diffusion NMR strategies to be generally applicable for calibrating the exchange of organic ligands on various nanoparticle systems.
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Affiliation(s)
- Xiaoqi Zhou
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Zhenfeng Pang
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Weicheng Cao
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Zhenming Cao
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Jie Zhu
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Yixin Qi
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Xiaogang Peng
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
| | - Xueqian Kong
- Department of Chemistry, Zhejiang University, Hangzhou310027, China.,Key Laboratory of Excited-State Materials of Zhejiang Province, Zhejiang University, Hangzhou310027, China
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13
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Heteroepitaxial chemistry of zinc chalcogenides on InP nanocrystals for defect-free interfaces with atomic uniformity. Nat Commun 2023; 14:43. [PMID: 36596807 PMCID: PMC9810615 DOI: 10.1038/s41467-022-35731-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 12/19/2022] [Indexed: 01/05/2023] Open
Abstract
Heteroepitaxy on colloidal semiconductor nanocrystals is an essential strategy for manipulating their optoelectronic functionalities. However, their practical synthesis typically leads to scattered and unexpected outcomes due to the intervention of multiple reaction pathways associated with complicated side products of reactants. Here, the heteroepitaxy mechanism of zinc chalcogenide initiated on indium phosphide (InP) colloidal nanocrystals is elucidated using the precursors, zinc carboxylate and trialkylphosphine selenide. The high magnetic receptivity of 77Se and the characteristic longitudinal optical phonon mode of ZnSe allowed for monitoring the sequence of epilayer formation at the molecular level. The investigation revealed the sterically hindered acyloxytrialkylphosphonium and diacyloxytrialkylphosphorane to be main intermediates in the surface reaction, which retards the metal ion adsorption by a large steric hindrance. The transformation of adsorbates to the crystalline epilayer was disturbed by surface oxides. Raman scattering disclosed the pathway of secondary surface oxidation triggered by carboxylate ligands migrated from zinc carboxylate. The surface-initiated heteroepitaxy protocol is proposed to fabricate core/shell heterostructured nanocrystals with atomic-scale uniformity of epilayers. Despite the large lattice mismatch of ZnS to InP, we realised a uniform and interface defect-free ZnS epilayer (~0.3 nm thickness) on InP nanocrystals, as evidenced by a high photoluminescence quantum yield of 97.3%.
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14
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Ye C, Yu M, Wang Z. Fabrication of sulfur quantum dots via a bottom-up strategy and its application for enhanced fluorescence monitoring of o-phenylenediamine. Microchem J 2022. [DOI: 10.1016/j.microc.2022.107978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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Ubbink R, Almeida G, Iziyi H, du Fossé I, Verkleij R, Ganapathy S, van Eck ERH, Houtepen AJ. A Water-Free In Situ HF Treatment for Ultrabright InP Quantum Dots. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2022; 34:10093-10103. [PMID: 36439318 PMCID: PMC9686131 DOI: 10.1021/acs.chemmater.2c02800] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/25/2022] [Indexed: 06/16/2023]
Abstract
Indium phosphide quantum dots are the main alternative for toxic and restricted Cd-based quantum dots for lighting and display applications, but in the absence of protecting ZnSe and/or ZnS shells, InP quantum dots suffer from low photoluminescence quantum yields. Traditionally, HF treatments have been used to improve the quantum yield of InP to ∼50%, but these treatments are dangerous and not well understood. Here, we develop a postsynthetic treatment that forms HF in situ from benzoyl fluoride, which can be used to strongly increase the quantum yield of InP core-only quantum dots. This treatment is water-free and can be performed safely. Simultaneous addition of the z-type ligand ZnCl2 increases the photoluminescence quantum yield up to 85%. Structural analysis via XPS as well as solid state and solution NMR measurements shows that the in situ generated HF leads to a surface passivation by indium fluoride z-type ligands and removes polyphosphates, but not PO3 and PO4 species from the InP surface. With DFT calculations it is shown that InP QDs can be trap-free even when PO3 and PO4 species are present on the surface. These results show that both polyphosphate removal and z-type passivation are necessary to obtain high quantum yields in InP core-only quantum dots. They further show that core-only InP QDs can achieve photoluminescence quantum yields rivalling those of InP/ZnSe/ZnS core/shell/shell QDs and the best core-only II-VI QDs.
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Affiliation(s)
- Reinout
F. Ubbink
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Guilherme Almeida
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Hodayfa Iziyi
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ruud Verkleij
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Swapna Ganapathy
- Department
of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, 2629 JB Delft, The Netherlands
| | - Ernst R. H. van Eck
- Magnetic
Resonance Research Center, Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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16
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Chen S, Riedinger A. Anisotropic and hyperbranched InP nanocrystals via chemical transformation of in situ produced In 2O 3. Chem Commun (Camb) 2022; 58:9246-9249. [PMID: 35900041 DOI: 10.1039/d2cc03456e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We synthesized indium phosphide (InP) nanoparticles of different shapes and sizes, utilizing triphenyl phosphite (TPOP) as the phosphorus source. We show that this reaction proceeds via the formation of in situ formed In2O3 nanoparticles followed by subsequent transformation with triphenyl TPOP acting as the phosphorus source. Our findings open up new synthetic possibilities utilizing a cost-effective, non-pyrophoric and non-toxic phosphorus precursor. The large surface area of hyperbranched InP NCs might be ideally suited for surface-driven processes such as catalysis and energy storage.
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Affiliation(s)
- Shuai Chen
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
| | - Andreas Riedinger
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
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17
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Li H, Zhang W, Bian Y, Ahn TK, Shen H, Ji B. ZnF 2-Assisted Synthesis of Highly Luminescent InP/ZnSe/ZnS Quantum Dots for Efficient and Stable Electroluminescence. NANO LETTERS 2022; 22:4067-4073. [PMID: 35536635 DOI: 10.1021/acs.nanolett.2c00763] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
High-quality InP-based quantum dots (QDs) have become very promising, environmentally benign light emitters for display applications, but their synthesis generally entails hazardous hydrofluoric acid. Here, we present a highly facile route to InP/ZnSe/ZnS core/shell/shell QDs with a near-unity photoluminescence quantum yield. As the key additive, the inorganic salt ZnF2 mildly reacts with carboxylic acid at a high temperature and in situ generates HF, which eliminates surface oxide impurities, thus facilitating epitaxial shell growth. The resulting InP/ZnSe/ZnS QDs exhibit a narrower emission line width and better thermal stability in comparison with QDs synthesized with hydrofluoric acid. Light-emitting diodes using large-sized InP/ZnSe/ZnS QDs without replacing original ligands achieve the highest peak external quantum efficiency of 22.2%, to the best of our knowledge, along with a maximum brightness of >110 000 cd/m2 and a T95 lifetime of >32 000 h at 100 cd/m2. This safe approach is anticipated to be applied for a wide range of III-V QDs.
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Affiliation(s)
- Haiyang Li
- Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, School of Engineering, Westlake University and Institute of Advanced Technology, Westlake Institute for Advanced Study, Hangzhou 310024, China
- Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials, Henan University, Kaifeng 475004, China
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Wenjing Zhang
- Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials, Henan University, Kaifeng 475004, China
| | - Yangyang Bian
- Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials, Henan University, Kaifeng 475004, China
| | - Tae Kyu Ahn
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Huaibin Shen
- Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, School of Materials, Henan University, Kaifeng 475004, China
| | - Botao Ji
- Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, School of Engineering, Westlake University and Institute of Advanced Technology, Westlake Institute for Advanced Study, Hangzhou 310024, China
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18
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Cui Z, Mei S, Wen Z, Yang D, Qin S, Xiong Z, Yang B, He H, Bao R, Qiu Y, Chen Y, Zhang W, Xie F, Xing G, Guo R. Synergistic Effect of Halogen Ions and Shelling Temperature on Anion Exchange Induced Interfacial Restructuring for Highly Efficient Blue Emissive InP/ZnS Quantum Dots. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2108120. [PMID: 35253372 DOI: 10.1002/smll.202108120] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/04/2022] [Indexed: 06/14/2023]
Abstract
InP quantum dots (QDs) have attracted much attention owing to their nontoxic properties and shown great potential in optoelectronic applications. Due to the surface defects and lattice mismatch, the interfacial structure of InP/ZnS QDs plays a significant role in their performance. Herein, the formation of In-S and Sx -In-P1-x interlayers through anion exchange at the shell-growth stage is revealed. More importantly, it is proposed that the composition of interface is dependent on the synergistic effect of halogen ions and shelling temperature. High shelling temperature contributes to the optical performance improvement resulting from the formation of interlayers, besides the thicker ZnS shell. Moreover, the effect relates to the halogen ions where I- presents more obvious enhancement than Br- and Cl- , owing to their different ability to coordinate with In dangling bonds, which are inclined to form In-S and Sx -In-P1-x bonds. Further, the anion exchange under I- -rich environment causes a blue-shift of emission wavelength with shelling temperature increasing, unobserved in a Cl- - or Br- -rich environment. It contributes to the preparation of highly efficient blue emissive InP/ZnS QDs with emission wavelength of 473 nm, photoluminescence quantum yield of ≈50% and full width at half maximum of 47 nm.
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Affiliation(s)
- Zhongjie Cui
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Shiliang Mei
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Zhuoqi Wen
- Institute of Future Lighting, Academy for Engineering and Technology, Fudan University, Shanghai, 200433, China
| | - Dan Yang
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Shuaitao Qin
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Zhiyong Xiong
- Institute of Future Lighting, Academy for Engineering and Technology, Fudan University, Shanghai, 200433, China
| | - Bobo Yang
- School of Science, Shanghai Institute of Technology, Shanghai, 201418, China
| | - Haiyang He
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Rui Bao
- Institute of Future Lighting, Academy for Engineering and Technology, Fudan University, Shanghai, 200433, China
| | - Yi Qiu
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Yuanyuan Chen
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Wanlu Zhang
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
| | - Fengxian Xie
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
- Zhongshan-Fudan Joint Innovation Center, Zhongshan, 528437, China
| | - Guichuan Xing
- Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, 999078, China
| | - Ruiqian Guo
- Institute for Electric Light Sources, School of Information Science and Technology, Fudan University, Shanghai, 200433, China
- Institute of Future Lighting, Academy for Engineering and Technology, Fudan University, Shanghai, 200433, China
- Zhongshan-Fudan Joint Innovation Center, Zhongshan, 528437, China
- Yiwu Research Institute of Fudan University, Chengbei Road, Yiwu City, 322000, China
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19
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Elimelech O, Aviv O, Oded M, Peng X, Harries D, Banin U. Entropy of Branching Out: Linear versus Branched Alkylthiols Ligands on CdSe Nanocrystals. ACS NANO 2022; 16:4308-4321. [PMID: 35157440 PMCID: PMC8945696 DOI: 10.1021/acsnano.1c10430] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Surface ligands of semiconductor nanocrystals (NCs) play key roles in determining their colloidal stability and physicochemical properties and are thus enablers also for the NCs flexible manipulation toward numerous applications. Attention is usually paid to the ligand binding group, while the impact of the ligand chain backbone structure is less discussed. Using isothermal titration calorimetry (ITC), we studied the effect of structural changes in the ligand chain on the thermodynamics of the exchange reaction for oleate coated CdSe NCs, comparing linear and branched alkylthiols. The investigated alkylthiol ligands differed in their backbone length, branching position, and branching group length. Compared to linear ligands, lower exothermicity and entropy loss were observed for an exchange with branched ligands, due to steric hindrance in ligand packing, thereby justifying their previous classification as "entropic ligands". Mean-field calculations for ligand binding demonstrate the contribution to the overall entropy originating from ligand conformational entropy, which is diminished upon binding mainly by packing of NC-bound ligands. Model calculations and the experimental ITC data both point to an interplay between the branching position and the backbone length in determining the entropic nature of the branched ligand. Our findings suggest that the most entropic ligand should be a short, branched ligand with short branching group located toward the middle of the ligand chain. The insights provided by this work also contribute to a future smarter NC surface design, which is an essential tool for their implementation in diverse applications.
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Affiliation(s)
- Orian Elimelech
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Omer Aviv
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Meirav Oded
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Xiaogang Peng
- Department
of Chemistry, Zhejiang University, Hangzhou 310027 P. R. China
| | - Daniel Harries
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- The
Fritz Haber Center, The Hebrew University
of Jerusalem, Jerusalem 9190401, Israel
| | - Uri Banin
- The
Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
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20
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Zhang X, Hudson MH, Castellano FN. Engineering Long-Lived Blue Photoluminescence from InP Quantum Dots Using Isomers of Naphthoic Acid. J Am Chem Soc 2022; 144:3527-3534. [PMID: 35188779 DOI: 10.1021/jacs.1c12207] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Leveraging triplet excitons in semiconductor quantum dots (QDs) in concert with surface-anchored molecules to produce long-lifetime thermally activated delayed photoluminescence (TADPL) continues to emerge as a promising technology in diverse areas including photochemical catalysis and light generation. All QDs presently used to generate TADPL in QD/molecule constructs contain toxic metals including Cd(II) and Pb(II), ultimately limiting potential real-world applications. Here, we report newly conceived blue-emitting TADPL-producing nanomaterials featuring InP QDs interfaced with 1- and 2-naphthoic acid (1-NA and 2-NA) ligands. These constitutional isomers feature similar triplet energies but disparate triplet lifetimes, translating into InP-based TADPL processes displaying two distinct average lifetime ranges upon cooling from 293 to 193 K. The time constants fall between 4.4 and 59.2 μs in the 2-NA-decorated InP QDs while further expanding between 84.2 and 733.2 μs in the corresponding 1-NA-ligated InP materials, representing a 167-fold time window. The resulting long-lived excited states enabled facile bimolecular triplet sensitization of 1O2 phosphorescence in the near-IR and promoted sensitized triplet-triplet annihilation photochemistry in 2,5-diphenyloxazole. We speculate that the discovery of new nanomaterials exhibiting TADPL lies on the horizon as myriad QDs can be readily derivatized using isomers of numerous classes of surface-anchoring chromophores yielding precisely regulated photophysical properties.
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Affiliation(s)
- Xingao Zhang
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Margaret H Hudson
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Felix N Castellano
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
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21
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Hoisang W, Uematsu T, Torimoto T, Kuwabata S. Surface ligand chemistry on quaternary Ag(In x Ga 1-x )S 2 semiconductor quantum dots for improving photoluminescence properties. NANOSCALE ADVANCES 2022; 4:849-857. [PMID: 36131838 PMCID: PMC9419514 DOI: 10.1039/d1na00684c] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 12/08/2021] [Indexed: 06/15/2023]
Abstract
Ternary and quaternary semiconductor quantum dots (QDs) are candidates for cadmium-free alternatives. Among these, semiconductors containing elements from groups 11, 13, and 16 (i.e., I-III-VI2) are attracting increasing attention since they are direct semiconductors whose bandgap energies in the bulk state are tunable between visible and near infrared. The quaternary system of alloys consisting of silver indium sulfide (AgInS2; bandgap energy: E g = 1.8 eV) and silver gallium sulfide (AgGaS2; E g = 2.4 eV) (i.e., Ag[In x Ga1-x ]S2 (AIGS)) enables bandgap tuning over a wide range of visible light. However, the photoluminescence (PL) quantum yield (10-20%) of AIGS QDs is significantly lower than that of AgInS2 (60-70%). The present study investigates how to improve the PL quantum yield of AIGS QDs via surface ligand engineering. Firstly, the use of a mixture of oleic acid and oleylamine, instead of only oleylamine, as the solvent for the QD synthesis was attempted, and a threefold improvement of the PL quantum yield was achieved. Subsequently, a post-synthetic ligand exchange was performed. Although the addition of alkylphosphine, which is known as an L-type ligand, improved the PL efficiency only by 20%, the use of metal halides, which are categorized as Z-type ligands, demonstrated a twofold to threefold improvement of the PL quantum yield, with the highest value reaching 73.4%. The same procedure was applied to the band-edge emitting core/shell-like QDs that were synthesized in one batch based on our previous findings. While the as-prepared core/shell-like QDs exhibited a PL quantum yield of only 9%, the PL quantum yield increased to 49.5% after treatment with metal halides.
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Affiliation(s)
- Watcharaporn Hoisang
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan
| | - Taro Uematsu
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan
| | - Tsukasa Torimoto
- Department of Materials Chemistry, Graduate School of Engineering, Nagoya University Chikusa-ku Nagoya 464-8603 Japan
| | - Susumu Kuwabata
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan
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22
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Greytak AB, Abiodun SL, Burrell JM, Cook EN, Jayaweera NP, Islam MM, Shaker AE. Thermodynamics of nanocrystal–ligand binding through isothermal titration calorimetry. Chem Commun (Camb) 2022; 58:13037-13058. [DOI: 10.1039/d2cc05012a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Manipulations of nanocrystal (NC) surfaces have propelled the applications of colloidal NCs across various fields such as bioimaging, catalysis, electronics, and sensing applications.
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Affiliation(s)
- Andrew B. Greytak
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Sakiru L. Abiodun
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Jennii M. Burrell
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Emily N. Cook
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Nuwanthaka P. Jayaweera
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Md Moinul Islam
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Abdulla E Shaker
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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23
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Parvizian M, De Roo J. Precursor chemistry of metal nitride nanocrystals. NANOSCALE 2021; 13:18865-18882. [PMID: 34779811 PMCID: PMC8615547 DOI: 10.1039/d1nr05092c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 10/08/2021] [Indexed: 06/13/2023]
Abstract
Metal nitride nanocrystals are a versatile class of nanomaterials. Depending on their chemical composition, the optical properties vary from those of traditional semiconductor nanocrystals (called quantum dots) to more metallic character (featuring a plasmon resonance). However, the synthesis of colloidal metal nitride nanocrystals is challenging since the underlying precursor chemistry is much less developed compared to the chemistry of metal, metal chalcogenide or metal phosphide nanocrystals. Here, we review chemical approaches that lead (or could lead) to the formation of colloidally stable metal nitride nanocrystals. By systematically comparing different synthetic approaches, we uncover trends and gain insight into the chemistry of these challenging materials. We also discuss and critically evaluate the plausibility of certain suggested mechanisms. This review is meant as a guide for the further development of colloidal nitride nanocrystals.
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Affiliation(s)
- Mahsa Parvizian
- Department of Chemistry, University of Basel, Basel, Switzerland.
| | - Jonathan De Roo
- Department of Chemistry, University of Basel, Basel, Switzerland.
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24
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Zhang X, Lv H, Xing W, Li Y, Geng C, Xu S. Trioctylphosphine accelerated growth of InP quantum dots at low temperature. NANOTECHNOLOGY 2021; 33:055602. [PMID: 34670196 DOI: 10.1088/1361-6528/ac3180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/20/2021] [Indexed: 06/13/2023]
Abstract
Significant advance was realized on the economic synthesis of InP quantum dots (QDs) by using aminophosphines as phosphorus precursor. However, the low reaction activity and thermal degradation of aminophosphines bring severe difficulty for growth control of InP QDs. Here, we employed trioctylphosphine (TOP) as a surfactant to accelerate the growth of the InP QDs. The reaction mechanism study reveals that the TOP could form a reactive complex with indium halides that effectively accelerates the formation of InP monomer and reduces the demand for reaction temperature. On this basis, the effect of reaction temperature, precursors, and zinc halide additives on the growth of the TOP-InP QDs was explored. This strategy alleviates the difficulty in growth control of InP QDs and also benefits to the synthesis of luminescent InP/ZnS core-shell QDs within visible regime. A white-light emitting diode device was fabricated with the InP/ZnS QDs that demonstrates their application potential in light-emitting devices.
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Affiliation(s)
- Xinsu Zhang
- Tianjin Key Laboratory of Electronic Materials and Devices, School of Electronics and Information Engineering, Hebei University of Technology, 5340 Xiping Road, Tianjin 300401, People's Republic of China
| | - Hao Lv
- Tianjin Key Laboratory of Electronic Materials and Devices, School of Electronics and Information Engineering, Hebei University of Technology, 5340 Xiping Road, Tianjin 300401, People's Republic of China
| | - Weishuo Xing
- Tianjin Key Laboratory of Electronic Materials and Devices, School of Electronics and Information Engineering, Hebei University of Technology, 5340 Xiping Road, Tianjin 300401, People's Republic of China
| | - Yanjun Li
- Tianjin Key Laboratory of Electronic Materials and Devices, School of Electronics and Information Engineering, Hebei University of Technology, 5340 Xiping Road, Tianjin 300401, People's Republic of China
| | - Chong Geng
- Tianjin Key Laboratory of Electronic Materials and Devices, School of Electronics and Information Engineering, Hebei University of Technology, 5340 Xiping Road, Tianjin 300401, People's Republic of China
| | - Shu Xu
- Tianjin Key Laboratory of Electronic Materials and Devices, School of Electronics and Information Engineering, Hebei University of Technology, 5340 Xiping Road, Tianjin 300401, People's Republic of China
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25
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du Fossé I, Lal S, Hossaini AN, Infante I, Houtepen AJ. Effect of Ligands and Solvents on the Stability of Electron Charged CdSe Colloidal Quantum Dots. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:23968-23975. [PMID: 34765075 PMCID: PMC8573769 DOI: 10.1021/acs.jpcc.1c07464] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 10/12/2021] [Indexed: 06/07/2023]
Abstract
Many colloidal quantum dot (QD)-based devices involve charging of the QD, either via intentional electronic doping or via electrical charge injection or photoexcitation. Previous research has shown that this charging can give rise to undesirable electrochemical surface reactions, leading to the formation of localized in-gap states. However, little is known about the factors that influence the stability of charged QDs against surface oxidation or reduction. Here, we use density functional theory to investigate the effect of various ligands and solvents on the reduction of surface Cd in negatively charged CdSe QDs. We find that X-type ligands can lead to significant shifts in the energy of the band edges but that the in-gap state related to reduced surface Cd is shifted in the same direction. As a result, shifting the band edges to higher energies does not necessarily lead to less stable electron charging. However, subtle changes in the local electrostatic environment lead to a clear correlation between the position of the in-gap state in the bandgap and the energy gained upon surface reduction. Binding ligands directly to the Cd sites most prone to reduction was found to greatly enhance the stability of the electron charged QDs. We find that ligands bind much more weakly after reduction of the Cd site, leading to a loss in binding energy that makes charge localization no longer energetically favorable. Lastly, we show that increasing the polarity of the solvent also increases the stability of QDs charged with electrons. These results highlight the complexity of surface reduction reactions in QDs and provide valuable strategies for improving the stability of charged QDs.
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Affiliation(s)
- Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Snigdha Lal
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Aydin Najl Hossaini
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ivan Infante
- Department
of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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26
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Observation of ordered organic capping ligands on semiconducting quantum dots via powder X-ray diffraction. Nat Commun 2021; 12:2663. [PMID: 33976186 PMCID: PMC8113276 DOI: 10.1038/s41467-021-22947-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 03/30/2021] [Indexed: 02/03/2023] Open
Abstract
Powder X-ray diffraction is one of the key techniques used to characterize the inorganic structure of colloidal nanocrystals. The comparatively low scattering factor of nuclei of the organic capping ligands and their propensity to be disordered has led investigators to typically consider them effectively invisible to this technique. In this report, we demonstrate that a commonly observed powder X-ray diffraction peak around [Formula: see text] observed in many small, colloidal quantum dots can be assigned to well-ordered aliphatic ligands bound to and capping the nanocrystals. This conclusion differs from a variety of explanations ascribed by previous sources, the majority of which propose an excess of organic material. Additionally, we demonstrate that the observed ligand peak is a sensitive probe of ligand shell ordering. Changes as a function of ligand length, geometry, and temperature can all be readily observed by X-ray diffraction and manipulated to achieve desired outcomes for the final colloidal system.
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27
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Calvin JJ, O'Brien EA, Sedlak AB, Balan AD, Alivisatos AP. Thermodynamics of Composition Dependent Ligand Exchange on the Surfaces of Colloidal Indium Phosphide Quantum Dots. ACS NANO 2021; 15:1407-1420. [PMID: 33404231 DOI: 10.1021/acsnano.0c08683] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Quantum dot surfaces can have a substantial effect on their physical, chemical, and optoelectronic properties. When the chemistry that occurs at the surface of nanocrystals is studied, critical insights can be gained into the fundamental structural, thermodynamic, and optical properties of quantum dot materials providing a valuable guide for how to best adapt them for desired applications. Colloidal quantum dots are often terminated with organic ligands that consist of a long aliphatic chain and a head group that binds tightly to the nanocrystal surface. While extensive work has been done to understand how ligand head groups influence quantum dot properties, studies to unravel the influence of the organic ligand tail on ligands and surface reaction equilibria are incomplete. To further investigate the driving forces of quantum dot surface modification, a series of ligand exchange reactions with oleic acid were performed on indium phosphide quantum dots, initially terminated with straight-chain carboxylates of variable lengths. The reaction was monitored using isothermal titration calorimetry and 1H NMR to determine the extent of each reaction and its associated thermodynamics. From these measurements, interligand interactions were observed to be dependent on the length of the straight-chain ligand. A modified Ising model was used to investigate the enthalpic and entropic effects contributing to these ligand exchanges and reveal that interligand interactions play a much larger role than previously thought. Additional experimentation with phosphonic acid ligand exchange reveals complexity in the reaction mechanism but further illustrates the significant impact of ligand tail group length on thermodynamics, even in cases where there is a large difference in head group binding energy.
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Affiliation(s)
- Jason J Calvin
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Erin A O'Brien
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | | | - Arunima D Balan
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - A Paul Alivisatos
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Kavli Energy NanoScience Institute, Berkeley, California 94720, United States
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