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Focassio B, Fiuza TER, Bettini J, Schleder GR, Rodrigues MHM, Souza Junior JB, Leite ER, Fazzio A, Capaz RB. Stability and Rupture of an Ultrathin Ionic Wire. PHYSICAL REVIEW LETTERS 2022; 129:046101. [PMID: 35939018 DOI: 10.1103/physrevlett.129.046101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
Using a combination of in situ high-resolution transmission electron microscopy and density functional theory, we report the formation and rupture of ZrO_{2} atomic ionic wires. Near rupture, under tensile stress, the system favors the spontaneous formation of oxygen vacancies, a critical step in the formation of the monatomic bridge. In this length scale, vacancies provide ductilelike behavior, an unexpected mechanical behavior for ionic systems. Our results add an ionic compound to the very selective list of materials that can form monatomic wires and they contribute to the fundamental understanding of the mechanical properties of ceramic materials at the nanoscale.
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Affiliation(s)
- Bruno Focassio
- Federal University of ABC (UFABC), 09210-580 Santo André, São Paulo, Brazil
- Ilum School of Science, CNPEM, 13083-970 Campinas, São Paulo, Brazil
| | - Tanna E R Fiuza
- Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, São Paulo, Brazil
| | - Jefferson Bettini
- Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, São Paulo, Brazil
| | - Gabriel R Schleder
- Federal University of ABC (UFABC), 09210-580 Santo André, São Paulo, Brazil
- Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, São Paulo, Brazil
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Murillo H M Rodrigues
- Departamento de Química, Universidade Federal de São Carlos, 13565-905 São Carlos, São Paulo, Brazil
| | - João B Souza Junior
- Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, São Paulo, Brazil
| | - Edson R Leite
- Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, São Paulo, Brazil
- Departamento de Química, Universidade Federal de São Carlos, 13565-905 São Carlos, São Paulo, Brazil
| | - Adalberto Fazzio
- Federal University of ABC (UFABC), 09210-580 Santo André, São Paulo, Brazil
- Ilum School of Science, CNPEM, 13083-970 Campinas, São Paulo, Brazil
| | - Rodrigo B Capaz
- Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, São Paulo, Brazil
- Instituto de Física, Universidade Federal do Rio de Janeiro, 21941-909 Rio de Janeiro, Rio de Janeiro, Brazil
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2
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Rodrigues Fiuza TE, Muniz da Silva M, Bettini J, Leite ER. Visualization of the Final Stage of Sintering in Nanoceramics with Atomic Resolution. NANO LETTERS 2022; 22:1978-1985. [PMID: 35225619 DOI: 10.1021/acs.nanolett.1c04708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The deep understanding of the sintering mechanism is pivotal to optimizing denser ceramics production. Although several models explain the sintering satisfactorily on the micrometric scale, the extrapolation for nanostructured systems is not trivial. Aiming to provide additional information about the particularities of the sintering at the nanoscale, we performed in situ experiments using high-resolution transmission electron microscopy (HRTEM). We studied the pore elimination process in a ZrO2 thin film and identified a high anisotropic pore elimination. Interestingly, there is a redistribution of the atoms from the rough surface in the solid-gas surface, followed by the atom attachment in a faceted surface. Finally, we found evidence of the pore acting as a pin, reducing the GB mobility. These findings certainly can contribute to enhance the kinetic models to describe the densification process of systems at the nanoscale.
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Affiliation(s)
| | - Marlon Muniz da Silva
- Laboratório Nacional de Nanotecnologia (LNNano), CNPEM, 13083-970, Campinas, São Paulo, Brazil
- Faculdade de Química, Centro de Ciências Exatas, Ambientais e de Tecnologias (CEATEC), Pontifícia Universidade Católica de Campinas (PUCCamp), 13086-900, Campinas, São Paulo, Brazil
| | - Jefferson Bettini
- Laboratório Nacional de Nanotecnologia (LNNano), CNPEM, 13083-970, Campinas, São Paulo, Brazil
| | - Edson Roberto Leite
- Laboratório Nacional de Nanotecnologia (LNNano), CNPEM, 13083-970, Campinas, São Paulo, Brazil
- Departamento de Química, Universidade Federal de São Carlos, 13565-905, São Carlos, São Paulo, Brazil
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3
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Liu J, Zheng X, Mohammed OF, Bakr OM. Self-Assembly and Regrowth of Metal Halide Perovskite Nanocrystals for Optoelectronic Applications. Acc Chem Res 2022; 55:262-274. [PMID: 35037453 PMCID: PMC8811956 DOI: 10.1021/acs.accounts.1c00651] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
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Over the past decade, the impressive development
of metal halide
perovskites (MHPs) has made them leading candidates for applications
in photovoltaics (PVs), X-ray scintillators, and light-emitting diodes
(LEDs). Constructing MHP nanocrystals (NCs) with promising optoelectronic
properties using a low-cost approach is critical to realizing their
commercial potential. Self-assembly and regrowth techniques provide
a simple and powerful “bottom-up” platform for controlling
the structure, shape, and dimensionality of MHP NCs. The soft ionic
nature of MHP NCs, in conjunction with their low formation energy,
rapid anion exchange, and ease of ion migration, enables the rearrangement
of their overall appearance via self-assembly or regrowth. Because
of their low formation energy and highly dynamic surface ligands,
MHP NCs have a higher propensity to regrow than conventional hard-lattice
NCs. Moreover, their self-assembly and regrowth can be achieved simultaneously.
The self-assembly of NCs into close-packed, long-range-ordered mesostructures
provides a platform for modulating their electronic properties (e.g.,
conductivity and carrier mobility). Moreover, assembled MHP NCs exhibit
collective properties (e.g., superfluorescence, renormalized emission,
longer phase coherence times, and long exciton diffusion lengths)
that can translate into dramatic improvements in device performance.
Further regrowth into fused MHP nanostructures with the removal of
ligand barriers between NCs could facilitate charge carrier transport,
eliminate surface point defects, and enhance stability against moisture,
light, and electron-beam irradiation. However, the synthesis strategies,
diversity and complexity of structures, and optoelectronic applications
that emanate from the self-assembly and regrowth of MHPs have not
yet received much attention. Consequently, a comprehensive understanding
of the design principles of self-assembled and fused MHP nanostructures
will fuel further advances in their optoelectronic applications. In this Account, we review the latest developments in the self-assembly
and regrowth of MHP NCs. We begin with a survey of the mechanisms,
driving forces, and techniques for controlling MHP NC self-assembly.
We then explore the phase transition of fused MHP nanostructures at
the atomic level, delving into the mechanisms of facet-directed connections
and the kinetics of their shape-modulation behavior, which have been
elucidated with the aid of high-resolution transmission electron microscopy
(HRTEM) and first-principles density functional theory calculations
of surface energies. We further outline the applications of assembled
and fused nanostructures. Finally, we conclude with a perspective
on current challenges and future directions in the field of MHP NCs.
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Affiliation(s)
- Jiakai Liu
- Division of Physical Sciences and Engineering, KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
- College of New Materials and New Energies, Shenzhen Technology University, Shenzhen 518118, China
| | - Xiaopeng Zheng
- Division of Physical Sciences and Engineering, KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Omar F. Mohammed
- Division of Physical Sciences and Engineering, KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Osman M. Bakr
- Division of Physical Sciences and Engineering, KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
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4
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Chakraborty S, Petel BE, Schreiber E, Matson EM. Atomically precise vanadium-oxide clusters. NANOSCALE ADVANCES 2021; 3:1293-1318. [PMID: 36132875 PMCID: PMC9419539 DOI: 10.1039/d0na00877j] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 01/19/2021] [Indexed: 05/08/2023]
Abstract
Polyoxovanadate (POV) clusters are an important subclass of polyoxometalates with a broad range of molecular compositions and physicochemical properties. One relatively underdeveloped application of these polynuclear assemblies involves their use as atomically precise, homogenous molecular models for bulk metal oxides. Given the structural and electronic similarities of POVs and extended vanadium oxide materials, as well as the relative ease of modifying the homogenous congeners, investigation of the chemical and physical properties of pristine and modified cluster complexes presents a method toward understanding the influence of structural modifications (e.g. crystal structure/phase, chemical makeup of surface ligands, elemental dopants) on the properties of extended solids. This review summarises recent advances in the use of POV clusters as atomically precise models for bulk metal oxides, with particular focus on the assembly of vanadium oxide clusters and the consequences of altering the molecular composition of the assembly via organofunctionalization and the incorporation of elemental "dopants".
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Affiliation(s)
| | - Brittney E Petel
- University of Rochester, Department of Chemistry Rochester NY 14627 USA
| | - Eric Schreiber
- University of Rochester, Department of Chemistry Rochester NY 14627 USA
| | - Ellen M Matson
- University of Rochester, Department of Chemistry Rochester NY 14627 USA
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5
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Monego D, Kister T, Kirkwood N, Doblas D, Mulvaney P, Kraus T, Widmer-Cooper A. When Like Destabilizes Like: Inverted Solvent Effects in Apolar Nanoparticle Dispersions. ACS NANO 2020; 14:5278-5287. [PMID: 32298080 DOI: 10.1021/acsnano.9b03552] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We report on the colloidal stability of nanoparticles with alkanethiol shells in apolar solvents. Small-angle X-ray scattering and molecular dynamics simulations were used to characterize the interaction between nanoparticles in linear alkane solvents ranging from hexane to hexadecane, including 4 nm gold cores with hexadecanethiol shells and 6 nm cadmium selenide cores with octadecanethiol shells. We find that the agglomeration is enthalpically driven and that, contrary to what one would expect from classical colloid theory, the temperature at which the particles agglomerate increases with increasing solvent chain length. We demonstrate that the inverted trend correlates with the temperatures at which the ligands order in the different solvents and show that the inversion is due to a combination of enthalpic and entropic effects that enhance the stability of the ordered ligand state as the solvent length increases. We also explain why cyclohexane is a better solvent than hexadecane despite the two having very similar solvation parameters.
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Affiliation(s)
- Debora Monego
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
- The University of Sydney Nano Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Thomas Kister
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - Nicholas Kirkwood
- ARC Centre of Excellence in Exciton Science, School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - David Doblas
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
| | - Paul Mulvaney
- ARC Centre of Excellence in Exciton Science, School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Tobias Kraus
- INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
- Colloid and Interface Chemistry, Saarland University, Campus D2 2, 66123 Saarbrücken, Germany
| | - Asaph Widmer-Cooper
- ARC Centre of Excellence in Exciton Science, School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
- The University of Sydney Nano Institute, The University of Sydney, Sydney, New South Wales 2006, Australia
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6
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Santos MS, Freitas JCC, Dalmaschio CJ. Designed single-phase ZrO2 nanocrystals obtained by solvothermal syntheses. CrystEngComm 2020. [DOI: 10.1039/c9ce01992h] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Crystal growth pathways controlled by the acidity, type and concentration of the capping agent lead to different nanostructures and crystalline phases.
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Affiliation(s)
- Mayara S. Santos
- Department of Chemistry
- Federal University of Espírito Santo
- Vitória
- Brazil
| | - Jair C. C. Freitas
- Laboratory of Carbon and Ceramic Materials
- Department of Physics
- Federal University of Espírito Santo
- Vitória
- Brazil
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7
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Patra TK, Chan H, Podsiadlo P, Shevchenko EV, Sankaranarayanan SKRS, Narayanan B. Ligand dynamics control structure, elasticity, and high-pressure behavior of nanoparticle superlattices. NANOSCALE 2019; 11:10655-10666. [PMID: 30839029 DOI: 10.1039/c8nr09699f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Precise engineering of nanoparticle superlattices (NPSLs) for energy applications requires a molecular-level understanding of the physical factors governing their morphology, periodicity, mechanics, and response to external stimuli. Such knowledge, particularly the impact of ligand dynamics on physical behavior of NPSLs, is still in its infancy. Here, we combine coarse-grained molecular dynamics simulations, and small angle X-ray scattering experiments in a diamond anvil cell to demonstrate that coverage density of capping ligands (i.e., number of ligands per unit area of a nanoparticle's surface), strongly influences the structure, elasticity, and high-pressure behavior of NPSLs using face-centered cubic PbS-NPSLs as a representative example. We demonstrate that ligand coverage density dictates (a) the extent of diffusion of ligands over NP surfaces, (b) spatial distribution of the ligands in the interstitial spaces between neighboring NPs, and (c) the fraction of ligands that interdigitate across different nanoparticles. We find that below a critical coverage density (1.8 nm-2 for 7 nm PbS NPs capped with oleic acid), NPSLs collapse to form disordered aggregates via sintering, even under ambient conditions. Above the threshold ligand coverage density, NPSLs surprisingly preserve their crystalline order even under high applied pressures (∼40-55 GPa), and show a completely reversible pressure behavior. This opens the possibility of reversibly manipulating lattice spacing of NPSLs, and in turn, finely tuning their collective electronic, optical, thermo-mechanical, and magnetic properties.
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Affiliation(s)
- Tarak K Patra
- Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439, USA.
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8
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Schleder GR, Azevedo GM, Nogueira IC, Rebelo QHF, Bettini J, Fazzio A, Leite ER. Decreasing Nanocrystal Structural Disorder by Ligand Exchange: An Experimental and Theoretical Analysis. J Phys Chem Lett 2019; 10:1471-1476. [PMID: 30868882 DOI: 10.1021/acs.jpclett.9b00439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Nanocrystals (NCs) present unique physicochemical properties arising from their size and the presence of ligands. Comprehending and controlling the ligand-crystal interactions as well as the ligand exchange process is one of the central themes in NC science nowadays. However, the relationship between NC structural disorder and the ligand exchange effect in the NC atomic structure is not yet sufficiently understood. Here we combine pair distribution function analysis from electron diffraction data, extended X-ray absorption fine structure, and high-resolution transmission electron microscopy as experimental techniques and first-principles density functional theory calculations to elucidate the ligand exchange effects in the ZrO2 NC structure. We report a substantial decrease in the structural disorder for ZrO2 NCs caused by strain rearrangements during the ligand exchange process. These results can have a direct impact on the development of functional nanomaterials, especially in properties controlled by structural disorder.
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Affiliation(s)
- Gabriel R Schleder
- Federal University of ABC (UFABC) , Santo André , São Paulo 09210-580 , Brazil
- Brazilian Nanotechnology National Laboratory (LNNano)/CNPEM , Campinas , São Paulo 13083-970 , Brazil
| | - Gustavo M Azevedo
- Brazilian Synchrotron Light Laboratory (LNLS)/CNPEM , Campinas , São Paulo 13083-970 , Brazil
- Federal University of Rio Grande do Sul (UFRGS) , Porto Alegre , Rio Grande do Sul 90040-060 , Brazil
| | - Içamira C Nogueira
- Federal University of Amazonas (UFAM) , Manaus , Amazonas 69080-900 , Brazil
| | - Querem H F Rebelo
- Federal University of Amazonas (UFAM) , Manaus , Amazonas 69080-900 , Brazil
- Federal University of Western Pará (UFOPA) , Santarém , Pará 68035-110 , Brazil
| | - Jefferson Bettini
- Brazilian Nanotechnology National Laboratory (LNNano)/CNPEM , Campinas , São Paulo 13083-970 , Brazil
| | - Adalberto Fazzio
- Federal University of ABC (UFABC) , Santo André , São Paulo 09210-580 , Brazil
- Brazilian Nanotechnology National Laboratory (LNNano)/CNPEM , Campinas , São Paulo 13083-970 , Brazil
| | - Edson R Leite
- Brazilian Nanotechnology National Laboratory (LNNano)/CNPEM , Campinas , São Paulo 13083-970 , Brazil
- Federal University of São Carlos (UFSCar) , São Carlos , São Paulo 13565-905 , Brazil
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9
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Cordeiro MAL, Leite ER, Stach EA. Controlling the Formation and Structure of Nanoparticle Superlattices through Surface Ligand Behavior. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:11606-11614. [PMID: 27673391 DOI: 10.1021/acs.langmuir.6b03026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The tailoring of nanoparticle superlattices is fundamental to the design of novel nanostructured materials and devices. To obtain specific collective properties of these nanoparticle superlattices, reliable protocols for their self-assembly are required. This study provides insight into the self-assembly process by using oleate-covered CeO2 nanoparticles (cubic and polyhedral shapes) through the correlation of experimental and theoretical investigations. The self-assembly of CeO2 nanoparticles is controlled by tuning the colloid deposition parameters (temperature and evaporation rate), and the ordered structures so obtained were correlated to the Gibbs free energy variation of the system. The analysis of the interparticle force contributions for each structure showed the importance of both the effective ligand mean size and its Flory-Huggins parameter in determining the total potential energies. Additionally, the roles of ligand solubility and effective mean size were used to understand the formation of specific superlattice phases as a function of temperature and ligand accommodation in the arrangement. Furthermore, the face-to-face interactions between nanoparticles were correlated to the type of exposed crystallographic facet in each particle.
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Affiliation(s)
- Marco A L Cordeiro
- Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Edson R Leite
- Department of Chemistry, Federal University of Sao Carlos , 13565-905 Sao Carlos, SP Brazil
| | - Eric A Stach
- Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States
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10
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de Oliveira OV, Costa LT, Leite ER. Molecular modeling of a polymer nanocomposite model in water and chloroform solvents. COMPUT THEOR CHEM 2016. [DOI: 10.1016/j.comptc.2016.08.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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11
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Abstract
X-ray scattering is a structural characterization tool that has impacted diverse fields of study. It is unique in its ability to examine materials in real time and under realistic sample environments, enabling researchers to understand morphology at nanometer and angstrom length scales using complementary small and wide angle X-ray scattering (SAXS, WAXS), respectively. Herein, we focus on the use of SAXS to examine nanoscale particulate systems. We provide a theoretical foundation for X-ray scattering, considering both form factor and structure factor, as well as the use of correlation functions, which may be used to determine a particle's size, size distribution, shape, and organization into hierarchical structures. The theory is expanded upon with contemporary use cases. Both transmission and reflection (grazing incidence) geometries are addressed, as well as the combination of SAXS with other X-ray and non-X-ray characterization tools. We conclude with an examination of several key areas of research where X-ray scattering has played a pivotal role, including in situ nanoparticle synthesis, nanoparticle assembly, and operando studies of catalysts and energy storage materials. Throughout this review we highlight the unique capabilities of X-ray scattering for structural characterization of materials in their native environment.
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Affiliation(s)
- Tao Li
- X-ray Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Andrew J Senesi
- X-ray Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Byeongdu Lee
- X-ray Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States
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12
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Bernardino K, de Moura AF. Surface Electrostatic Potential and Water Orientation in the presence of Sodium Octanoate Dilute Monolayers Studied by Means of Molecular Dynamics Simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:10995-11004. [PMID: 26393372 DOI: 10.1021/acs.langmuir.5b02904] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A series of atomistic molecular dynamics simulations were performed in the present investigation to assess the spontaneous formation of surfactant monolayers of sodium octanoate at the water-vacuum interface. The surfactant surface coverage increased until a saturation threshold was achieved, after which any further surfactant addition led to the formation of micellar aggregates within the solution. The saturated films were not densely packed, as might be expected for short-chained surfactants, and all films regardless of the surface coverage presented surfactant molecules with the same ordering pattern, namely, with the ionic heads toward the aqueous solution and the tails lying nearly parallel to the interface. The major contributions to the electrostatic surface potential came from the charged heads and the counterion distribution, which nearly canceled out each other. The balance between the oppositely charged ions rendered the electrostatic contributions from water meaningful, amounting to ca. 10% of the contributions arising from the ionic species. And even the aliphatic tails, whose atoms bear relatively small partial atomic charges as compared to the polar molecules and molecular fragments, contributed with ca. 20% of the total electrostatic surface potential of the systems under investigation. Although the aliphatic tails were not so orderly arranged as in a compact film, the C-H bonds assumed a preferential orientation, leading to an increased contribution to the electrostatic properties of the interface. The most prominent feature arising from the partitioning of the electrostatic potential into individual contributions was the long-range ordering of the water molecules. This ordering of the water molecules produced a repulsive dipole-dipole interaction between the two interfaces, which increased with the surface coverage. Only for a water layer wider than 10 nm was true bulk behavior observed, and the repulsive dipole-dipole interaction faded away.
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Affiliation(s)
- Kalil Bernardino
- Departamento de Química, Universidade Federal de São Carlos , Rodovia Washington Luiz km 235, CP 676, CEP 13565-905, São Carlos, SP Brasil
| | - André F de Moura
- Departamento de Química, Universidade Federal de São Carlos , Rodovia Washington Luiz km 235, CP 676, CEP 13565-905, São Carlos, SP Brasil
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13
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Gaulding EA, Diroll BT, Goodwin ED, Vrtis ZJ, Kagan CR, Murray CB. Deposition of wafer-scale single-component and binary nanocrystal superlattice thin films via dip-coating. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:2846-51. [PMID: 25820834 DOI: 10.1002/adma.201405575] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 03/05/2015] [Indexed: 05/09/2023]
Affiliation(s)
- E Ashley Gaulding
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA
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14
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Baranov AV, Ushakova EV, Golubkov VV, Litvin AP, Parfenov PS, Fedorov AV, Berwick K. Self-organization of colloidal PbS quantum dots into highly ordered superlattices. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:506-513. [PMID: 25514192 DOI: 10.1021/la503913z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
X-ray structural analysis, together with steady-state and transient optical spectroscopy, is used for studying the morphology and optical properties of quantum dot superlattices (QDSLs) formed on glass substrates by the self-organization of PbS quantum dots with a variety of surface ligands. The diameter of the PbS QDs varies from 2.8 to 8.9 nm. The QDSL's period is proportional to the dot diameter, increasing slightly with dot size due to the increase in ligand layer thickness. Removal of the ligands has a number of effects on the morphology of QDSLs formed from the dots of different sizes: for small QDs the reduction in the amount of ligands obstructs the self-organization process, impairing the ordering of the QDSLs, while for large QDs the ordering of the superlattice structure is improved, with an interdot distance as low as 0.4 nm allowing rapid charge carrier transport through the QDSLs. QDSL formation does not induce significant changes to the absorption and photoluminescence spectra of the QDs. However, the luminescence decay time is reduced dramatically, due to the appearance of nonradiative relaxation channels.
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15
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de Moura AF, Bernardino K, Dalmaschio CJ, Leite ER, Kotov NA. Thermodynamic insights into the self-assembly of capped nanoparticles using molecular dynamic simulations. Phys Chem Chem Phys 2015; 17:3820-31. [PMID: 25562068 DOI: 10.1039/c4cp03519d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Although the molecular modeling of self-assembling processes stands as a challenging research issue, there have been a number of breakthroughs in recent years. This report describes the use of large-scale molecular dynamics simulations with coarse grained models to study the spontaneous self-assembling of capped nanoparticles in chloroform suspension. A model system comprising 125 nanoparticles in chloroform evolved spontaneously from a regular array of independent nanoparticles to a single thread-like, ramified superstructure spanning the whole simulation box. The aggregation process proceeded by means of two complementary mechanisms, the first characterized by reactive collisions between monomers and oligomers, which were permanently trapped into the growing superstructure, and the second a slow structural reorganization of the nanoparticle packing. Altogether, these aggregation processes were over after ca. 0.6 μs and the system remained structurally and energetically stable until 1 μs. The thread-like structure closely resembles the TEM images of capped ZrO2, but a better comparison with experimental results was obtained by the deposition of the suspension over a graphene solid substrate, followed by the complete solvent evaporation. The agreement between the main structural features from this simulation and those from the TEM experiment was excellent and validated the model system. In order to shed further light on the origins of the stable aggregation of the nanoparticles, the Gibbs energy of aggregation was computed, along with its enthalpy and entropy contributions, both in chloroform and in a vacuum. The thermodynamic parameters arising from the modeling are consistent with larger nanoparticles in chloroform due to the solvent-swelled organic layer and the overall effect of the solvent was the partial destabilization of the aggregated state as compared to the vacuum system. The modeling strategy has been proved effective and reliable to describe the self-assembling of capped nanoparticles, but we must acknowledge the fact that larger model systems and longer timescales will be necessary in future investigations in order to assess structural and dynamical information approaching the behavior of macroscopic systems.
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Affiliation(s)
- André F de Moura
- Departamento de Química, Centro de Ciências Exatas e de Tecnologia, Universidade Federal de São Carlos, Rodovia Washington Luiz km 235, CP 676, CEP 13565-905, São Carlos, SP, Brasil.
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Staniuk M, Zindel D, van Beek W, Hirsch O, Kränzlin N, Niederberger M, Koziej D. Matching the organic and inorganic counterparts during nucleation and growth of copper-based nanoparticles – in situ spectroscopic studies. CrystEngComm 2015. [DOI: 10.1039/c5ce00454c] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Closing the loop: initially, the reactivity of benzyl alcohol determines the nucleation of Cu nanoparticles, but as soon as they start to form they begin to catalyze the condensation of benzyl alcohol to dibenzylether.
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Affiliation(s)
- Malwina Staniuk
- Laboratory for Multifunctional Materials
- Department of Materials
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Daniel Zindel
- Laboratory of Physical Chemistry
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Wouter van Beek
- Swiss-Norwegian Beamlines at European Synchrotron Research Facility
- 38043 Grenoble, France
| | - Ofer Hirsch
- Laboratory for Multifunctional Materials
- Department of Materials
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Niklaus Kränzlin
- Laboratory for Multifunctional Materials
- Department of Materials
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Markus Niederberger
- Laboratory for Multifunctional Materials
- Department of Materials
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Dorota Koziej
- Laboratory for Multifunctional Materials
- Department of Materials
- ETH Zurich
- 8093 Zurich, Switzerland
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