1
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Shen M, Ding T, Tan C, Rackers WH, Zhang D, Lew MD, Sadtler B. In Situ Imaging of Catalytic Reactions on Tungsten Oxide Nanowires Connects Surface-Ligand Redox Chemistry with Photocatalytic Activity. NANO LETTERS 2022; 22:4694-4701. [PMID: 35674669 DOI: 10.1021/acs.nanolett.2c00674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Semiconductor nanocrystals are promising candidates for generating chemical feedstocks through photocatalysis. Understanding the role of ligands used to prepare colloidal nanocrystals in catalysis is challenging due to the complexity and heterogeneity of nanocrystal surfaces. We use in situ single-molecule fluorescence imaging to map the spatial distribution of active regions along individual tungsten oxide nanowires before and after functionalizing them with ascorbic acid. Rather than blocking active sites, we observed a significant enhancement in activity for photocatalytic water oxidation after treatment with ascorbic acid. While the initial nanowires contain inactive regions dispersed along their length, the functionalized nanowires show high uniformity in their photocatalytic activity. Spatial colocalization of the active regions with their surface chemical properties shows that oxidation of ascorbic acid during photocatalysis generates new oxygen vacancies along the nanowire surface. We demonstrate that controlling surface-ligand redox chemistry during photocatalysis can enhance the active site concentration on nanocrystal catalysts.
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Affiliation(s)
- Meikun Shen
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Tianben Ding
- Department of Electrical and Systems Engineering, Washington University, St. Louis, Missouri 63130, United States
| | - Che Tan
- Department of Energy, Environmental, and Chemical Engineering, Washington University, St. Louis, Missouri 63130, United States
| | - William H Rackers
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Dongyan Zhang
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Matthew D Lew
- Department of Electrical and Systems Engineering, Washington University, St. Louis, Missouri 63130, United States
- Institute of Materials Science and Engineering, Washington University, St. Louis, Missouri 63130, United States
| | - Bryce Sadtler
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
- Institute of Materials Science and Engineering, Washington University, St. Louis, Missouri 63130, United States
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2
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Tappan BA, Chu W, Mecklenburg M, Prezhdo OV, Brutchey RL. Discovery of a Wurtzite-like Cu 2FeSnSe 4 Semiconductor Nanocrystal Polymorph and Implications for Related CuFeSe 2 Materials. ACS NANO 2021; 15:13463-13474. [PMID: 34346226 DOI: 10.1021/acsnano.1c03974] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
I2-II-IV-VI4 and I-III-VI2 semiconductor nanocrystals have found applications in photovoltaics and other optoelectronic technologies because of their low toxicity and efficient light absorption into the near-infrared. Herein, we report the discovery of a metastable wurtzite-like polymorph of Cu2FeSnSe4, a member of the I2-II-IV-VI4 family of semiconductors containing only earth-abundant metals. Density functional theory calculations on this metastable polymorph of Cu2FeSnSe4 indicate that it may be a superior semiconductor for solar energy and optoelectronics applications compared to the thermodynamically preferred stannite polymorph, since the former displays a sharper dispersion of energy levels near the conduction band minimum that can enhance electron mobility and suppress hot electron cooling. The experimental optical band gap was measured by the inverse logarithmic derivative method to be direct, in agreement with theory, and in the range of 1.48-1.59 eV. Mechanistic studies reveal that this metastable phase derives from intermediate Cu3Se2 nanocrystals that serve as a structural template for the final hexagonal wurtzite-like product. We compare the chemistry of wurtzite-like Cu2FeSnSe4 to the related CuFeSe2 material system. Our experimental and computational comparisons between Cu2FeSnSe4 and CuFeSe2 help explain both the crystal chemistry of CuFeSe2 that prevents it from forming wurtzite-like polymorphs and the essential role of Sn in stabilizing the metastable structure of Cu2FeSnSe4. This work provides insight into the importance of elemental composition when designing syntheses for metastable materials.
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Affiliation(s)
- Bryce A Tappan
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Weibin Chu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Matthew Mecklenburg
- Core Center of Excellence in Nano Imaging, University of Southern California, Los Angeles, California 90089, United States
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Richard L Brutchey
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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3
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Chen Y, Dorn RW, Hanrahan MP, Wei L, Blome-Fernández R, Medina-Gonzalez AM, Adamson MAS, Flintgruber AH, Vela J, Rossini AJ. Revealing the Surface Structure of CdSe Nanocrystals by Dynamic Nuclear Polarization-Enhanced 77Se and 113Cd Solid-State NMR Spectroscopy. J Am Chem Soc 2021; 143:8747-8760. [PMID: 34085812 DOI: 10.1021/jacs.1c03162] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) spectroscopy was used to obtain detailed surface structures of zinc blende CdSe nanocrystals (NCs) with plate or spheroidal morphologies which are capped by carboxylic acid ligands. 1D 113Cd and 77Se cross-polarization magic angle spinning (CPMAS) NMR spectra revealed distinct signals from Cd and Se atoms on the surface of the NCs, and those residing in bulk-like environments, below the surface. 113Cd cross-polarization magic-angle-turning (CP-MAT) experiments identified CdSe3O, CdSe2O2, and CdSeO3 Cd coordination environments on the surface of the NCs, where the oxygen atoms are presumably from coordinated carboxylate ligands. The sensitivity gain from DNP enabled natural isotopic abundance 2D homonuclear 113Cd-113Cd and 77Se-77Se and heteronuclear 113Cd-77Se scalar correlation solid-state NMR experiments which revealed the connectivity of the Cd and Se atoms. Importantly, 77Se{113Cd} scalar heteronuclear multiple quantum coherence (J-HMQC) experiments were used to selectively measure one-bond 77Se-113Cd scalar coupling constants (1J(77Se, 113Cd)). With knowledge of 1J(77Se, 113Cd), heteronuclear 77Se{113Cd} spin echo (J-resolved) NMR experiments were used to determine the number of Cd atoms bonded to Se atoms and vice versa. The J-resolved experiments directly confirmed that major Cd and Se surface species have CdSe2O2 and SeCd4 stoichiometries, respectively. Considering the crystal structure of zinc blende CdSe and the similarity of the solid-state NMR data for the platelets and spheroids, we conclude that the surface of the spheroidal CdSe NCs is primarily composed of {100} facets. The methods outlined here will generally be applicable to obtain detailed surface structures of various main group semiconductor nanoparticles.
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Affiliation(s)
- Yunhua Chen
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Rick W Dorn
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Michael P Hanrahan
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Lin Wei
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | | | | | - Marquix A S Adamson
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Anne H Flintgruber
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States
| | - Javier Vela
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Aaron J Rossini
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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4
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Hanrahan MP, Chen Y, Blome-Fernández R, Stein JL, Pach GF, Adamson MAS, Neale NR, Cossairt BM, Vela J, Rossini AJ. Probing the Surface Structure of Semiconductor Nanoparticles by DNP SENS with Dielectric Support Materials. J Am Chem Soc 2019; 141:15532-15546. [PMID: 31456398 DOI: 10.1021/jacs.9b05509] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Surface characterization is crucial for understanding how the atomic-level structure affects the chemical and photophysical properties of semiconducting nanoparticles (NPs). Solid-state nuclear magnetic resonance spectroscopy (NMR) is potentially a powerful technique for the characterization of the surface of NPs, but it is hindered by poor sensitivity. Dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) has previously been demonstrated to enhance the sensitivity of surface-selective solid-state NMR experiments by 1-2 orders of magnitude. Established sample preparations for DNP SENS experiments on NPs require the dilution of the NPs on mesoporous silica. Using hexagonal boron nitride (h-BN) to disperse the NPs doubles DNP enhancements and absolute sensitivity in comparison to standard protocols with mesoporous silica. Alternatively, precipitating the NPs as powders, mixing them with h-BN, and then impregnating the powdered mixture with radical solution leads to further 4-fold sensitivity enhancements by increasing the concentration of NPs in the final sample. This modified procedure provides a factor of 9 improvement in NMR sensitivity in comparison to previously established DNP SENS procedures, enabling challenging homonuclear and heteronuclear 2D NMR experiments on CdS, Si, and Cd3P2 NPs. These experiments allow NMR signals from the surface, subsurface, and core sites to be observed and assigned. For example, we demonstrate the acquisition of DNP-enhanced 2D 113Cd-113Cd correlation NMR experiments on CdS NPs and natural isotropic abundance 2D 13C-29Si HETCOR of functionalized Si NPs. These experiments provide a critical understanding of NP surface structures.
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Affiliation(s)
- Michael P Hanrahan
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
| | - Yunhua Chen
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
| | | | - Jennifer L Stein
- University of Washington , Department of Chemistry , Seattle , Washington 98195 , United States
| | - Gregory F Pach
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , 15013 Denver West Parkway , Golden , Colorado 80401 , United States
| | - Marquix A S Adamson
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States
| | - Nathan R Neale
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , 15013 Denver West Parkway , Golden , Colorado 80401 , United States
| | - Brandi M Cossairt
- University of Washington , Department of Chemistry , Seattle , Washington 98195 , United States
| | - Javier Vela
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
| | - Aaron J Rossini
- Iowa State University , Department of Chemistry , Ames , Iowa 50011 , United States.,US DOE Ames Laboratory , Ames , Iowa 50011 , United States
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5
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Tchaplyguine M, Mikkelä MH, Mårsell E, Polley C, Mikkelsen A, Zhang W, Yartsev A, Hetherington CJD, Wallenberg LR, Björneholm O. Metal-passivated PbS nanoparticles: fabrication and characterization. Phys Chem Chem Phys 2018; 19:7252-7261. [PMID: 28239693 DOI: 10.1039/c6cp06870g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Organic-shell-free PbS nanoparticles have been produced in the size range relevant for quantum-dot solar cells (QDSCs) by a vapor aggregation method involving magnetron reactive sputtering. This method creates a beam of free 5-10 nm particles in a vacuum. The dimensions of the particles were estimated after their deposition on a substrate by imaging them using ex situ SEM and HRTEM electron microscopy. The particle structure and chemical composition could be deduced "on the fly", prior to deposition, using X-ray photoelectron spectroscopy (XPS) with tunable synchrotron radiation. Our XPS results suggest that under certain conditions it is possible to fabricate particles with a semiconductor core and 1 to 2 monolayer shells of metallic lead. For this case the absolute energy of the highest occupied molecular orbital (HOMO) in PbS has been determined to be (5.0 ± 0.5) eV below the vacuum level. For such particles deposited on a substrate HRTEM has confirmed the XPS-based conclusions on the crystalline PbS structure of the semiconductor core. Absorption spectroscopy on the deposited film has given a value of ∼1 eV for the lowest exciton. Together with the valence XPS results this has allowed us to reconstruct the energy level scheme of the particles. The results obtained are discussed in the context of the properties of PbS QDSCs.
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Affiliation(s)
- M Tchaplyguine
- MAX-lab, Lund University, P.O. Box SE-118, 22100 Lund, Sweden.
| | - M-H Mikkelä
- MAX-lab, Lund University, P.O. Box SE-118, 22100 Lund, Sweden.
| | - E Mårsell
- Synchrotron Radiation Research Division, Department of Physics, Lund University, Box 118, SE-22100 Lund, Sweden
| | - C Polley
- MAX-lab, Lund University, P.O. Box SE-118, 22100 Lund, Sweden.
| | - A Mikkelsen
- Synchrotron Radiation Research Division, Department of Physics, Lund University, Box 118, SE-22100 Lund, Sweden
| | - W Zhang
- Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - A Yartsev
- Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - C J D Hetherington
- nCHREM, Center for analysis and synthesis, Lund University, Box 124, SE-22100 Lund, Sweden
| | - L R Wallenberg
- nCHREM, Center for analysis and synthesis, Lund University, Box 124, SE-22100 Lund, Sweden
| | - O Björneholm
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
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6
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Slang S, Loghina L, Palka K, Vlcek M. Exposure enhanced photoluminescence of CdS0.9Se0.1quantum dots embedded in spin-coated Ge25S75thin films. RSC Adv 2017. [DOI: 10.1039/c7ra09540f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Semiconductor quantum dots (QDs) are well known photoluminescent materials.
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Affiliation(s)
- Stanislav Slang
- Center of Materials and Nanotechnologies
- Faculty of Chemical Technology
- University of Pardubice
- Pardubice 53210
- Czech Republic
| | - Liudmila Loghina
- Center of Materials and Nanotechnologies
- Faculty of Chemical Technology
- University of Pardubice
- Pardubice 53210
- Czech Republic
| | - Karel Palka
- Center of Materials and Nanotechnologies
- Faculty of Chemical Technology
- University of Pardubice
- Pardubice 53210
- Czech Republic
| | - Miroslav Vlcek
- Center of Materials and Nanotechnologies
- Faculty of Chemical Technology
- University of Pardubice
- Pardubice 53210
- Czech Republic
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7
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Shen Y, Roberge A, Tan R, Gee MY, Gary DC, Huang Y, Blom DA, Benicewicz BC, Cossairt BM, Greytak AB. Gel permeation chromatography as a multifunctional processor for nanocrystal purification and on-column ligand exchange chemistry. Chem Sci 2016; 7:5671-5679. [PMID: 30034705 PMCID: PMC6022040 DOI: 10.1039/c6sc01301e] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 05/20/2016] [Indexed: 01/31/2023] Open
Abstract
This article illustrates the use of gel permeation chromatography (GPC, organic-phase size exclusion chromatography) to separate nanocrystals from weakly-bound small molecules, including solvent, on the basis of size. A variety of colloidal inorganic nanocrystals of different size, shape, composition, and surface termination are shown to yield purified samples with greatly reduced impurity concentrations. Additionally, the method is shown to be useful in achieving a change of solvent without requiring precipitation of the nanocrystals. By taking advantage of the different rates at which small molecules and nanoparticles travel through the column, we show that it is furthermore possible to use the GPC column as a multi-functional flow reactor that can accomplish in sequence the steps of initial purification, ligand exchange with controlled reactant concentration and interaction time, and subsequent cleanup without requiring a change of phase. This example of process intensification via GPC is shown to yield nearly complete displacement of the initial surface ligand population upon reaction with small molecule and macromolecular reactants to form ligand-exchanged nanocrystal products.
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Affiliation(s)
- Yi Shen
- Department of Chemistry and Biochemistry , University of South Carolina , Columbia , SC 29208 , USA .
| | - Adam Roberge
- Department of Chemistry and Biochemistry , University of South Carolina , Columbia , SC 29208 , USA .
| | - Rui Tan
- Department of Chemistry and Biochemistry , University of South Carolina , Columbia , SC 29208 , USA .
| | - Megan Y Gee
- Department of Chemistry and Biochemistry , University of South Carolina , Columbia , SC 29208 , USA .
| | - Dylan C Gary
- Department of Chemistry , University of Washington , Seattle , WA 98195 , USA
| | - Yucheng Huang
- Department of Chemistry and Biochemistry , University of South Carolina , Columbia , SC 29208 , USA .
| | - Douglas A Blom
- USC Nanocenter , University of South Carolina , Columbia , SC 29208 , USA
| | - Brian C Benicewicz
- Department of Chemistry and Biochemistry , University of South Carolina , Columbia , SC 29208 , USA .
- USC Nanocenter , University of South Carolina , Columbia , SC 29208 , USA
| | - Brandi M Cossairt
- Department of Chemistry , University of Washington , Seattle , WA 98195 , USA
| | - Andrew B Greytak
- Department of Chemistry and Biochemistry , University of South Carolina , Columbia , SC 29208 , USA .
- USC Nanocenter , University of South Carolina , Columbia , SC 29208 , USA
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8
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Deringer VL, Dronskowski R. Von atomistischer Oberflächenchemie zu Nanokristallen funktionaler Chalkogenide. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201506874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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9
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Deringer VL, Dronskowski R. From Atomistic Surface Chemistry to Nanocrystals of Functional Chalcogenides. Angew Chem Int Ed Engl 2015; 54:15334-40. [DOI: 10.1002/anie.201506874] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 09/03/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Volker L. Deringer
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen (Germany)
| | - Richard Dronskowski
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen (Germany)
- Jülich‐Aachen Research Alliance (JARA‐HPC), RWTH Aachen University, 52056 Aachen (Germany)
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10
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Jiang T, Wang Y, Meng D, Kong J, Jia H, Wang Z. Self‐Assembly Growth and Photocatalytic Performance of Nanostructured Copper Compounds. Eur J Inorg Chem 2015. [DOI: 10.1002/ejic.201500563] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Tingting Jiang
- Faculty of Material Science and Chemisty, China University of Geoscience, Wuhan 430074, P. R. China http://chxy.cug.edu.cn/cn/Tech_Cons.asp?id=79
| | - Yongqian Wang
- Faculty of Material Science and Chemisty, China University of Geoscience, Wuhan 430074, P. R. China http://chxy.cug.edu.cn/cn/Tech_Cons.asp?id=79
- Guangxi University, Nanning 530004, P. R. China
| | - Dawei Meng
- Faculty of Material Science and Chemisty, China University of Geoscience, Wuhan 430074, P. R. China http://chxy.cug.edu.cn/cn/Tech_Cons.asp?id=79
| | - Junhan Kong
- Faculty of Material Science and Chemisty, China University of Geoscience, Wuhan 430074, P. R. China http://chxy.cug.edu.cn/cn/Tech_Cons.asp?id=79
| | - Hanxiang Jia
- Faculty of Material Science and Chemisty, China University of Geoscience, Wuhan 430074, P. R. China http://chxy.cug.edu.cn/cn/Tech_Cons.asp?id=79
| | - Zhengshu Wang
- Faculty of Material Science and Chemisty, China University of Geoscience, Wuhan 430074, P. R. China http://chxy.cug.edu.cn/cn/Tech_Cons.asp?id=79
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11
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Ortiz N, Weiner RG, Skrabalak SE. Ligand-controlled Co-reduction versus electroless Co-deposition: synthesis of nanodendrites with spatially defined bimetallic distributions. ACS NANO 2014; 8:12461-12467. [PMID: 25490676 DOI: 10.1021/nn5052822] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The predictable synthesis of bimetallic nanostructures via co-reduction of two metal precursors is challenging due to our limited understanding of precursor ligand effects. Here, the influence of different metal-ligand environments is systematically examined in the synthesis of Pd-Pt nanostructures as a model bimetallic system. Nanodendrites with different spatially defined Pd-Pt compositions are achieved, where the local ligand environments of metal precursors dictate if temporally separated co-reduction dominates to achieve core-shell nanostructures or whether electroless co-deposition proceeds to facilitate alloyed nanostructure formation. As the properties of bimetallic nanomaterials depend on crystal ordering and composition, chemical routes to structurally defined bimetallic nanomaterials are critically needed. The approaches reported here should be applicable to other bimetallic compositions given the established reactivity of coordination complexes available for use as precursors.
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Affiliation(s)
- Nancy Ortiz
- Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
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12
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Devi AB, Moirangthem DS, Talukdar NC, Devi MD, Singh NR, Luwang MN. Novel synthesis and characterization of CuO nanomaterials: Biological applications. CHINESE CHEM LETT 2014. [DOI: 10.1016/j.cclet.2014.07.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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13
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Guo Y, Rowland CE, Schaller RD, Vela J. Near-infrared photoluminescence enhancement in Ge/CdS and Ge/ZnS Core/shell nanocrystals: utilizing IV/II-VI semiconductor epitaxy. ACS NANO 2014; 8:8334-8343. [PMID: 25010416 DOI: 10.1021/nn502792m] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ge nanocrystals have a large Bohr radius and a small, size-tunable band gap that may engender direct character via strain or doping. Colloidal Ge nanocrystals are particularly interesting in the development of near-infrared materials for applications in bioimaging, telecommunications and energy conversion. Epitaxial growth of a passivating shell is a common strategy employed in the synthesis of highly luminescent II-VI, III-V and IV-VI semiconductor quantum dots. Here, we use relatively unexplored IV/II-VI epitaxy as a way to enhance the photoluminescence and improve the optical stability of colloidal Ge nanocrystals. Selected on the basis of their relatively small lattice mismatch compared with crystalline Ge, we explore the growth of epitaxial CdS and ZnS shells using the successive ion layer adsorption and reaction method. Powder X-ray diffraction and electron microscopy techniques, including energy dispersive X-ray spectroscopy and selected area electron diffraction, clearly show the controllable growth of as many as 20 epitaxial monolayers of CdS atop Ge cores. In contrast, Ge etching and/or replacement by ZnS result in relatively small Ge/ZnS nanocrystals. The presence of an epitaxial II-VI shell greatly enhances the near-infrared photoluminescence and improves the photoluminescence stability of Ge. Ge/II-VI nanocrystals are reproducibly 1-3 orders of magnitude brighter than the brightest Ge cores. Ge/4.9CdS core/shells show the highest photoluminescence quantum yield and longest radiative recombination lifetime. Thiol ligand exchange easily results in near-infrared active, water-soluble Ge/II-VI nanocrystals. We expect this synthetic IV/II-VI epitaxial approach will lead to further studies into the optoelectronic behavior and practical applications of Si and Ge-based nanomaterials.
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Affiliation(s)
- Yijun Guo
- Department of Chemistry, Iowa State University , Ames, Iowa 50010, United States
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14
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Ortiz N, Skrabalak SE. On the dual roles of ligands in the synthesis of colloidal metal nanostructures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:6649-59. [PMID: 24446902 DOI: 10.1021/la404539p] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Eloquent routes to colloidal metal nanostructures have emerged in recent years, and a central component to any successful nanosynthesis is the initial selection of metal complexes with an appropriate ligand environment. This local ligand environment may be predetermined by the coordination complex selected as the metal precursor; however, recent studies reveal that the ligand environment of coordination complexes can be modified through exchange with other components for the synthesis that include solvent molecules, capping agents, anions, and even reducing agents. Importantly, ligands can often play multiple roles in a synthesis and direct the outcome by manipulating the rates of precursor reduction and particle coalescence, providing colloidal and facet stabilization and even serving as reducing agents themselves. This Feature Article highlights examples in which the ligand environments of metal precursors and nanoparticles contribute to product formation in multiple ways. Acknowledgment of the dual roles of ligands in nanomaterial synthesis will enable new strategies for nanostructures by decoupling the often contradictory roles of ligands.
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Affiliation(s)
- Nancy Ortiz
- Department of Chemistry, Indiana University , 800 E. Kirkwood Avenue, Bloomington, Indiana 47405, United States
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