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Trejo M, Clifford A, Alfonso EG, Halberstadt N, Xue L, Kong W. Electron diffraction of foam-like clusters between xenon and helium in superfluid helium droplets. J Chem Phys 2024; 161:054306. [PMID: 39092938 DOI: 10.1063/5.0221682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2024] [Accepted: 07/17/2024] [Indexed: 08/04/2024] Open
Abstract
We report electron diffraction results of xenon clusters formed in superfluid helium droplets, with droplet sizes in the range of 105-106 atoms/droplet and xenon clusters from a few to a few hundred atoms. Under four different experimental conditions, the diffraction profiles can be fitted using four atom pairs of Xe. For the two experiments performed with higher helium contributions, the fittings with one pair of Xe-He and three pairs of Xe-Xe distances are statistically preferred compared with four pairs of Xe-Xe distances, while the other two experiments exhibit the opposite preference. In addition to the shortest pair distances corresponding to the van der Waals distances of Xe-He and Xe-Xe, the longer distances are in the range of the different arrangements of Xe-He-Xe and Xe-He-He-Xe. The number of independent atom pairs is too many for the small xenon clusters and too few for the large clusters. We consider these results evidence of xenon foam structures, with helium atoms stuck between Xe atoms. This possibility is confirmed by helium time-dependent density functional calculations. When the impact parameter of the second xenon atom is a few Angstroms or longer, the second xenon atom fails to penetrate the solvation shell of the first atom, resulting in a dimer with a few He atoms in between the two Xe atoms. In addition, our results for larger droplets point toward a multi-center growth process of dopant atoms or molecules, which is in agreement with previous proposals from theoretical calculations and experimental results.
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Affiliation(s)
- Marisol Trejo
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Andrew Clifford
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Ernesto Garcia Alfonso
- Labo Collisions, Agrégats, Réactivité (LCAR) Université de Toulouse and CNRS, 118 route de Narbonne, 31062 CEDEX 09 Toulouse, France
| | - Nadine Halberstadt
- Labo Collisions, Agrégats, Réactivité (LCAR) Université de Toulouse and CNRS, 118 route de Narbonne, 31062 CEDEX 09 Toulouse, France
| | - Lan Xue
- Department of Statistics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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2
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Topcu G, Al Hindawi AMA, Feng C, Spence D, Sitorus B, Liu H, Ellis AM, Yang S. Precision engineering of nano-assemblies in superfluid helium by the use of van der Waals forces. Commun Chem 2024; 7:125. [PMID: 38834741 DOI: 10.1038/s42004-024-01203-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 05/16/2024] [Indexed: 06/06/2024] Open
Abstract
The ability to precisely engineer nanostructures underpins a wide range of applications in areas such as electronics, optics, and biomedical sciences. Here we present a novel approach for the growth of nanoparticle assemblies that leverages the unique properties of superfluid helium. Unlike viscous solvents at or near room temperature, superfluid helium provides an unperturbed and cold environment in which weak van der Waals interactions between molecular templates and metal atoms become significant and can define the spatial arrangement of nanoparticles. To demonstrate this concept, diol and porphyrin-based molecules are employed as templates to grow gold nanoparticle assemblies in superfluid helium droplets. After soft-landing on a solid surface to remove the helium, transmission electron microscopy (TEM) imaging shows the growth of gold nanoparticles at specific binding sites within the molecular templates where the interaction between gold atoms and the molecular template is at its strongest.
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Affiliation(s)
- Gokhan Topcu
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Aula M A Al Hindawi
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
- Department of Chemistry, College of Education for Pure Science, University of Karbala, Karbala, Iraq
| | - Cheng Feng
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Daniel Spence
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Berlian Sitorus
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
- Department of Chemistry, Tanjungpura University, Pontianak, Indonesia
| | - Hanqing Liu
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Andrew M Ellis
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Shengfu Yang
- School of Chemistry, University of Leicester, Leicester, LE1 7RH, UK.
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3
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Wu W, Pavloudis T, Palmer RE. Core atoms escape from the shell: reverse segregation of Pb-Al core-shell nanoclusters via nanoscale melting. DISCOVER NANO 2023; 18:143. [PMID: 37975964 PMCID: PMC10656412 DOI: 10.1186/s11671-023-03924-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 11/13/2023] [Indexed: 11/19/2023]
Abstract
Melting is a phase transition that profoundly affects the fabrication and diverse applications of metal nanoclusters. Core-shell clusters offer distinctive properties and thus opportunities compared with other classes of nano-alloys. Molecular dynamics simulations have been employed to investigate the melting behaviour of Pb-Al core-shell clusters containing a fixed Pb147 core and varying shell thickness. Our results show that the core and shell melt separately. Surprisingly, core melting always drives the core Pb atoms to break out the shell and coat the nanoclusters in a reversed segregation process at the nanoscale. The melting point of the core increases with the shell thickness to exceed that of the bare core cluster, but the thinnest shell always supresses the core melting point. These results can be a reference for the future fabrication, manipulation, and exploitation of the core-shell nanoalloys chosen. The system chosen is ideally suited for experimental observations.
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Affiliation(s)
- Wenkai Wu
- Nanomaterials Lab, Mechanical Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, SA1 8EN, UK
| | - Theodoros Pavloudis
- Nanomaterials Lab, Mechanical Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, SA1 8EN, UK
- School of Physics, Faculty of Sciences, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece
| | - Richard E Palmer
- Nanomaterials Lab, Mechanical Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, SA1 8EN, UK.
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4
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Jensen M, Kierulf-Vieira W, Kooyman PJ, Sjåstad AO. Variable temperature in situ TEM mapping of the thermodynamically stable element distribution in bimetallic Pt-Rh nanoparticles. NANOSCALE ADVANCES 2023; 5:5286-5294. [PMID: 37767042 PMCID: PMC10521204 DOI: 10.1039/d3na00448a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Accepted: 08/16/2023] [Indexed: 09/29/2023]
Abstract
We report here the first variable temperature in situ transmission electron microscopy (TEM) study on smaller Pt-Rh nanoparticles (≤24 nm) under vacuum conditions. Well-defined 50 at% Pt/50 at% Rh Pt-Rh solid solution and Rh(core)-Pt(shell) nanoparticles, obtained via colloidal synthesis routes, were investigated between room temperature and 650 °C to elucidate the tendency of elemental mixing/segregation. Key findings are that Pt-Rh nanoparticles <13 nm are stable in a solid solution configuration over the entire studied temperature range, whereas nanoparticles >13 nm tend to segregate upon cooling. Such a cross-over in element distribution with nanoparticle size has not been reported for the Pt-Rh system previously. The results demonstrate the technique's ability to extract valuable information concerning the intricate dynamic processes that take place in the bimetallic Pt-Rh system at the nanoscale, which may be indispensable when optimizing, e.g., the metal composition in catalytically active materials.
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Affiliation(s)
- Martin Jensen
- Center for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo P.O. Box 1033 Blindern N-0315 Oslo Norway
| | - Walace Kierulf-Vieira
- Center for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo P.O. Box 1033 Blindern N-0315 Oslo Norway
| | - Patricia J Kooyman
- Catalysis Institute, Department of Chemical Engineering, University of Cape Town Private Bag X3 Rondebosch 7701 South Africa
| | - Anja O Sjåstad
- Center for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo P.O. Box 1033 Blindern N-0315 Oslo Norway
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5
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Fernández B, Pi M, de Lara-Castells MP. Superfluid helium droplet-mediated surface-deposition of neutral and charged silver atomic species. Phys Chem Chem Phys 2023. [PMID: 37317779 DOI: 10.1039/d3cp01303k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Experimental and theoretical work has delivered evidence of the helium nanodroplet-mediated synthesis and soft-landing of metal nanoparticles, nanowires, clusters, and single atoms on solid supports. Recent experimental advances have allowed the formation of charged metal clusters into multiply charged helium nanodroplets. The impact of the charge of immersed metal species in helium nanodroplet-mediated surface deposition is proved by considering silver atoms and cations at zero-temperature graphene as the support. By combining high-level ab initio intermolecular interaction theory with a full quantum description of the superfluid helium nanodroplet motion, evidence is presented that the fundamental mechanism of soft-deposition is preserved in spite of the much stronger interaction of charged species with surfaces, with high-density fluctuations in the helium droplet playing an essential role in braking them. Corroboration is also presented that the soft-landing becomes favored as the helium nanodroplet size increases.
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Affiliation(s)
- Berta Fernández
- Department of Physical Chemistry, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - Martí Pi
- Departament FQA, Facultat de Física, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
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Ernst WE, Lasserus M, Knez D, Hofer F, Hauser AW. Mixed-metal nanoparticles: phase transitions and diffusion in Au-VO clusters. Faraday Discuss 2023; 242:160-173. [PMID: 36178317 PMCID: PMC9890498 DOI: 10.1039/d2fd00089j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Nanoparticles with diameters in the range of a few nanometers, consisting of gold and vanadium oxide, are synthesized by sequential doping of cold helium droplets in a molecular beam apparatus and deposited on solid carbon substrates. After surface deposition, the samples are removed and various measurement techniques are applied to characterize the created particles: scanning transmission electron microscopy (STEM) at atomic resolution, temperature dependent STEM and TEM up to 650 °C, energy-dispersive X-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS). In previous experiments we have shown that pure V2O5 nanoparticles can be generated by sublimation from the bulk and deposited without affecting their original stoichiometry. Interestingly, our follow-up attempts to create Au@V2O5 core@shell particles do not yield the expected encapsulated structure. Instead, Janus particles of Au and V2O5 with diameters between 10 and 20 nm are identified after deposition. At the interface of the Au and the V2O5 parts we observe an epitaxial-like growth of the vanadium oxide next to the Au structure. To test the temperature stability of these Janus-type particles, the samples are heated in situ during the STEM measurements from room temperature up to 650 °C, where a reduction from V2O5 to V2O3 is followed by a restructuring of the gold atoms to form a Wulff-shaped cluster layer. The temperature dependent dynamic interplay between gold and vanadium oxide in structures of only a few nanometer size is the central topic of this contribution to the Faraday Discussion.
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Affiliation(s)
- Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of TechnologyGrazAustria
| | | | - Daniel Knez
- Institute for Electron Microscopy and Nanoanalysis, Graz University of TechnologyGrazAustria
| | - Ferdinand Hofer
- Institute for Electron Microscopy and Nanoanalysis, Graz University of TechnologyGrazAustria
| | - Andreas W. Hauser
- Institute of Experimental Physics, Graz University of TechnologyGrazAustria
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7
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Wang L, Ore RM, Jayamaha PK, Wu ZP, Zhong CJ. Density functional theory based computational investigations on the stability of highly active trimetallic PtPdCu nanoalloys for electrochemical oxygen reduction. Faraday Discuss 2023; 242:429-442. [PMID: 36173024 DOI: 10.1039/d2fd00101b] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Activity, cost, and durability are the trinity of catalysis research for the electrochemical oxygen reduction reaction (ORR). While studies towards increasing activity and reducing cost of ORR catalysts have been carried out extensively, much effort is needed in durability investigation of highly active ORR catalysts. In this work, we examined the stability of a trimetallic PtPdCu catalyst that has demonstrated high activity and incredible durability during ORR using density functional theory (DFT) based computations. Specifically, we studied the processes of dissolution/deposition and diffusion between the surface and inner layer of Cu species of Pt20Pd20Cu60 catalysts at electrode potentials up to 1.2 V to understand their role towards stabilizing Pt20Pd20Cu60 catalysts. The results show there is a dynamic Cu surface composition range that is dictated by the interplay of the four processes, dissolution, deposition, diffusion from the surface to inner layer, and diffusion from the inner layer to the surface of Cu species, in the stability and observed oscillation of lattice constants of Cu-rich PtPdCu nanoalloys.
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Affiliation(s)
- Lichang Wang
- School of Chemical and Biomolecular Sciences and the Materials Technology Center, Southern Illinois University, Carbondale, IL 62901, USA.
| | - Rotimi M Ore
- School of Chemical and Biomolecular Sciences and the Materials Technology Center, Southern Illinois University, Carbondale, IL 62901, USA.
| | - Peshala K Jayamaha
- School of Chemical and Biomolecular Sciences and the Materials Technology Center, Southern Illinois University, Carbondale, IL 62901, USA.
| | - Zhi-Peng Wu
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY 13902, USA
| | - Chuan-Jian Zhong
- Department of Chemistry, State University of New York at Binghamton, Binghamton, NY 13902, USA
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8
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de Lara-Castells MP. First-principles modelling of the new generation of subnanometric metal clusters: Recent case studies. J Colloid Interface Sci 2022; 612:737-759. [PMID: 35033919 DOI: 10.1016/j.jcis.2021.12.186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/28/2021] [Accepted: 12/29/2021] [Indexed: 10/19/2022]
Abstract
The very recent development of highly selective techniques making possible the synthesis and experimental characterization of subnanometric (subnanometer-sized) metal clusters (even single atoms) is pushing our understanding far beyond the present knowledge in materials science, driving these clusters as a new generation of quantum materials at the lower bounds of nanotechnology. When the size of the metal cluster is reduced to a small number of atoms, the d-band of the metal splits into a subnanometric d-type molecular orbitals network in which all metal atoms are inter-connected, with the inter-connections having the length of a chemical bond (1-2 Å). These molecular characteristics are at the very core of the high stability and novel properties of the smallest metal clusters, with their integration into colloidal materials interacting with the environment having the potential to further boost their performance in applications such as luminescence, sensing, bioimaging, theranostics, energy conversion, catalysis, and photocatalysis. Through the presentation of very recent case studies, this Feature Article is aimed to illustrate how first-principles modelling, including methods beyond the state-of-the-art and an interplay with cutting-edge experiments, is helping to understand the special properties of these clusters at the most fundamental level. Moreover, it will be discussed how superfluid helium droplets can act both as nano-reactors and carriers to achieve the synthesis and surface deposition of metal clusters. This concept will be illustrated with the quantum simulation of the helium droplet-assisted soft-landing of a single Au atom onto a titanium dioxide (TiO2) surface. Next, it will be shown how the application of first-principles methods have disclosed the fundamental reasons why subnanometric Cu5 clusters are resistant to irreversible oxidation, and capable of increasing and extending into the visible region the solar absorption of TiO2, of augmenting its efficiency for photo-catalysis beyond a factor of four, also considering the decomposition and photo-activation of CO2 as a prototypical (photo-) catalytic reaction. Finally, I will discuss how the modification of the same material with subnanometric Ag5 clusters has converted it into a "reporter" of a surface polaron property as well as a novel two-dimensional polaronic material.
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9
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Zhang J, Kong W. Electron diffraction as a structure tool for charged and neutral nanoclusters formed in superfluid helium droplets. Phys Chem Chem Phys 2022; 24:6349-6362. [PMID: 35257134 PMCID: PMC10508180 DOI: 10.1039/d2cp00048b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This perspective presents the current status and future directions in using electron diffraction to determine the structures of clusters formed in superfluid helium droplets. The details of the experimental setup and data treatment procedures are explained, and several examples are illustrated. The ease of forming atomic and molecular clusters has been recognized since the invention of superfluid helium droplet beams. To resolve atomic structures from clusters formed in droplets, substantial efforts have been devoted to minimizing the contribution of helium to diffraction signals. With active background subtraction, we have obtained structures from clusters containing a few to more than 10 monomers, with and without heavy atoms to assist with the diffraction intensity, for both neutral and ionic species. From fittings of the diffraction profiles using model structures, we have observed that some small clusters adopt the structures of the corresponding solid sample, even for dimers such as iodine and pyrene, while others require trimers or tetramers to reach the structural motif of bulk solids, and smaller clusters such as CS2 dimers adopt gas phase structures. Cationic clusters of argon clusters contain an Ar3+ core, while pyrene dimers demonstrate a change in the intermolecular distance, from 3.5 Å for neutral dimers to 3.0 Å for cations. Future improvements in reducing the background of helium, and in expanding the information content of electron diffraction such as detection of charge distributions, are also discussed.
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Affiliation(s)
- Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, OR 97331, USA.
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, OR 97331, USA.
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10
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Lei L, Zhang J, Trejo M, Bradford SD, Kong W. Resolving the interlayer distance of cationic pyrene clusters embedded in superfluid helium droplets using electron diffraction. J Chem Phys 2022; 156:051101. [DOI: 10.1063/5.0080365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Lei Lei
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Marisol Trejo
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Stephen D. Bradford
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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11
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Settem M, Srivastav AK, Kanjarla AK. Understanding the strain-dependent structure of Cu nanocrystals in Ag-Cu nanoalloys. Phys Chem Chem Phys 2021; 23:26165-26177. [PMID: 34797355 DOI: 10.1039/d1cp04145b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The structure of octahedral Ag-Cu nanoalloys is investigated by means of basin hopping Monte Carlo (BHMC) searches involving the optimization of shape and chemical ordering. Due to the significant size mismatch between Ag and Cu, the misfit strain plays a key role in determining the structure of Ag-Cu nanoalloys. At all the compositions, segregated chemical ordering is observed. However, the shape of the Cu nanocrystal and the associated defects are significantly different. At lower amounts of Cu (as little as 2 atom %), defects close to the surface are observed leading to a highly non-compact shape of the Cu nanocrystal which is non-trivial. The number of Cu-Cu bonds is relatively lower in the non-compact shape which is contrary to the preference of bulk Ag-Cu alloys to maximize the homo-atomic bonds. Due to the non-compact shape, {100} Ag-Cu interfaces are observed which are not expected. As the amount of Cu increases, the Cu nanocrystal undergoes a shape transition from non-compact to a compact octahedron. The associated defect structure is also modified. The structural changes due to the strain effects have been explained by calculating the atomic pressure maps and the bond length distributions. The trends relating to the structure have also been verified at larger sizes.
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Affiliation(s)
- Manoj Settem
- Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600036, India.
| | - Ajeet K Srivastav
- Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology, Nagpur, 440010, India
| | - Anand K Kanjarla
- Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600036, India. .,Ceramic Technologies Group - Center of Excellence in Materials and Manufacturing for Futuristic Mobility, Indian Institute of Technology Madras, Chennai, 600036, India
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12
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Blancafort-Jorquera M, González M. Vibrational energy relaxation of a diatomic molecule in a superfluid helium nanodroplet: influence of the nanodroplet size, interaction energy and energy gap. Phys Chem Chem Phys 2021; 23:25961-25973. [PMID: 34783338 DOI: 10.1039/d1cp03629g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The influence of the nanodroplet size, molecule-helium interaction potential energy and ν = 1 - ν = 0 vibrational energy gap on the vibrational energy relaxation (VER) of a diatomic molecule (X2) in a superfluid helium nanodroplet [HeND or (4He)N; finite quantum solvent at T = 0.37 K] has been studied using a hybrid quantum approach recently proposed by us and taking as a reference the VER results on the I2@(4He)100 doped nanodroplet (Vilà et al., Phys. Chem. Chem. Phys., 2018, 20, 118, which corresponds to the first theoretical study on the VER of molecules embedded in a HeND). This has allowed us to obtain a deeper insight into the vibrational relaxation dynamics. The nanodroplet size has a very small effect on the VER, as this process mainly depends on the interaction between the molecule and the nanodroplet first solvation shell. Regarding the interaction potential energy and the energy gap, both factors play an important and comparable role in the VER time properties (global relaxation time, lifetime and transition time). As the former becomes stronger the relaxation time properties decrease in a significant way (their inverse follows a linear dependence with respect to the ν = 1 - ν = 0 coupling term) and they also decrease in a significant manner when the energy gap diminishes (linear dependence on the ν = 1 - ν = 0 energy difference). We expect that this study will motivate further work on the vibrational relaxation process in HeNDs.
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Affiliation(s)
- Miquel Blancafort-Jorquera
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
| | - Miguel González
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
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13
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Hudry D, De Backer A, Popescu R, Busko D, Howard IA, Bals S, Zhang Y, Pedrazo-Tardajos A, Van Aert S, Gerthsen D, Altantzis T, Richards BS. Interface Pattern Engineering in Core-Shell Upconverting Nanocrystals: Shedding Light on Critical Parameters and Consequences for the Photoluminescence Properties. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2104441. [PMID: 34697908 DOI: 10.1002/smll.202104441] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 09/01/2021] [Indexed: 06/13/2023]
Abstract
Advances in controlling energy migration pathways in core-shell lanthanide (Ln)-based hetero-nanocrystals (HNCs) have relied heavily on assumptions about how optically active centers are distributed within individual HNCs. In this article, it is demonstrated that different types of interface patterns can be formed depending on shell growth conditions. Such interface patterns are not only identified but also characterized with spatial resolution ranging from the nanometer- to the atomic-scale. In the most favorable cases, atomic-scale resolved maps of individual particles are obtained. It is also demonstrated that, for the same type of core-shell architecture, the interface pattern can be engineered with thicknesses of just 1 nm up to several tens of nanometers. Total alloying between the core and shell domains is also possible when using ultra-small particles as seeds. Finally, with different types of interface patterns (same architecture and chemical composition of the core and shell domains) it is possible to modify the output color (yellow, red, and green-yellow) or change (improvement or degradation) the absolute upconversion quantum yield. The results presented in this article introduce an important paradigm shift and pave the way toward the emergence of a new generation of core-shell Ln-based HNCs with better control over their atomic-scale organization.
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Affiliation(s)
- Damien Hudry
- Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Annick De Backer
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
- NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Radian Popescu
- Laboratory for Electron Microscopy, Karlsruhe Institute of Technology, Engesserstrasse 7, 76131, Karlsruhe, Germany
| | - Dmitry Busko
- Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Ian A Howard
- Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
- Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131, Karlsruhe, Germany
| | - Sara Bals
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
- NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Yang Zhang
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
- NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Adrian Pedrazo-Tardajos
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
- NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Sandra Van Aert
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
- NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Dagmar Gerthsen
- Laboratory for Electron Microscopy, Karlsruhe Institute of Technology, Engesserstrasse 7, 76131, Karlsruhe, Germany
| | - Thomas Altantzis
- Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
- NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp, 2020, Belgium
| | - Bryce S Richards
- Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
- Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131, Karlsruhe, Germany
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14
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Nelli D, Pietrucci F, Ferrando R. Impurity diffusion in magic-size icosahedral clusters. J Chem Phys 2021; 155:144304. [PMID: 34654289 DOI: 10.1063/5.0060236] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Atomic diffusion is at the basis of chemical ordering transformations in nanoalloys. Understanding the diffusion mechanisms at the atomic level is therefore a key issue in the study of the thermodynamic behavior of these systems and, in particular, of their evolution from out-of-equilibrium chemical ordering types often obtained in the experiments. Here, the diffusion is studied in the case of a single-atom impurity of Ag or Au moving within otherwise pure magic-size icosahedral clusters of Cu or Co by means of two different computational techniques, i.e., molecular dynamics and metadynamics. Our simulations reveal unexpected diffusion pathways, in which the displacement of the impurity is coupled with the creation of vacancies in the central part of the cluster. We show that the observed mechanism is quite different from the vacancy-mediated diffusion processes identified so far, and we demonstrate that it can be related to the presence of non-homogeneous compressive stress in the inner part of the icosahedral structure.
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Affiliation(s)
- Diana Nelli
- Dipartimento di Fisica dell'Università di Genova, via Dodecaneso 33, Genova 16146, Italy
| | - Fabio Pietrucci
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IMPMC, 75005 Paris, France
| | - Riccardo Ferrando
- Dipartimento di Fisica dell'Università di Genova and CNR-IMEM, via Dodecaneso 33, Genova 16146, Italy
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15
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Zhang J, Trejo M, Bradford SD, Lei L, Kong W. Electron Diffraction of Ionic Argon Nanoclusters Embedded in Superfluid Helium Droplets. J Phys Chem Lett 2021; 12:9644-9650. [PMID: 34586826 PMCID: PMC8550877 DOI: 10.1021/acs.jpclett.1c02712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We report electron diffraction of cationic argon nanoclusters embedded in superfluid helium droplets. Superfluid helium droplets are first doped with neutral argon atoms to form nanoclusters, and then the doped droplets are ionized by electrons. The much lower ionization energy of argon ensures that the positive charge resides on the Ar nanocluster. Using different stagnation temperatures and therefore droplets with different sizes, we have been able to preferentially form a small ionic cluster containing 2-4 Ar atoms and a larger cluster containing 7-11 atoms. The fitting results of the diffraction profiles agree with structures reported from theoretical calculations, containing a cationic trimer core with the remaining atoms largely neutral. This work testifies to the feasibility of performing electron diffraction from ionic species embedded in superfluid helium droplets, dispelling the concern over the particle density in the diffraction region. However, the large number of neutral helium atoms surrounding the cationic nanoclusters poses a challenge for the detection of the helium solvation layer, and the detection of which awaits further technological improvements.
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Affiliation(s)
| | | | | | | | - Wei Kong
- Corresponding author, , 541-737-6714
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16
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Molecular dynamics study on structural and atomic evolution between Au and Ni nanoparticles through coalescence. Sci Rep 2021; 11:15432. [PMID: 34326385 PMCID: PMC8322430 DOI: 10.1038/s41598-021-94822-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 07/06/2021] [Indexed: 11/22/2022] Open
Abstract
Motivated by the structure evolution experiments of Janus NiAu nanoparticles (NPs), we present a detailed study on the thermodynamic evolution of Ni and Au NPs with different ratios of Au and Ni through the molecular dynamics (MD) simulations. It is found that, for fixed Ni particle size (5.8 nm in diameter), the energy variation with the increasing temperature is related to the Au sizes (1.5–9.6 nm in diameter), due to the diverse atomic segregation modes. For a small Au particle, due to lattice induction, the structure will change from order to disorder and then to order. The interface defects of the merging NPs could be automatically eliminated by coalescence processes. The change in energy as the temperature increases is similar to that of monometallic NPs. For larger Au particles, the irregular variation of energy occurs and the atomic energy experience one or two reductions at least with the increase of the temperature. The segregation of Au atoms to the surface of Ni particle is dominant during the continuous heating process. The coalescence processes of Au atoms strongly determine the final morphology of the particles. Dumbbell-like, Janus and eccentric core–shell spherical structures could be obtained during the heating process. Our results will provide an effective approach to the design of novel materials with specific properties through thermal control.
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17
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López-Caballero P, Garsed R, de Lara-Castells MP. Computational Characterization of the Intermixing of Iron Triade (Fe, Co, and Ni) Surfaces and Sub-nanometric Clusters with Atomic Gold. ACS OMEGA 2021; 6:16165-16175. [PMID: 34179662 PMCID: PMC8223428 DOI: 10.1021/acsomega.1c02116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 05/24/2021] [Indexed: 05/05/2023]
Abstract
Dispersion-corrected density functional theory (DFT-D3) is applied to model iron triade (Fe, Co, and Ni) surfaces upon exchange of surface atoms with atomic gold. One first goal is to analyze the contact problem at the triade surface-Au interface and to correlate our findings with recent observations on iron triade nanoparticles (with diameters of around 5 nm) passivated by a few layers of gold. For this purpose, we analyze: (1) the energies of substitution; (2) the restructuring of the iron triade surfaces upon the atomic exchange; (3) the density of the orbitals bearing the largest projection on d(Au) atomic orbitals and, particularly, their overlap with orbitals from neighboring atoms of the triade surfaces; (4) the modification of the electronic density of states; and (5) the redistribution of the electronic density upon intermixing of Au and triade atoms. Inspite of the similarities between Ni, Co, and Fe in the condensed phase, significant differences are found in the features characterizing the exchange process. In particular, we find a better integration of the Au atom on the substitutional site of the Ni(001) surface than on those of the Fe(001) and Co(001) surfaces. This is in agreement with the fact that the electronic density of states is almost indistinguishable before and after Ni-Au intermixing. This outcome is correlated with the experimental observation on the allowing transition of Ni-Au core-shell nanoparticles before reaching the melting temperature. Our second objective is to explore the Au-triade atom intermixing process in sub-nanometric clusters, finding that it is energetically more favored than at solid surfaces yet endothermic at 0 K. This feature is explained as the result of the structural fluxionality characterizing clusters at the sub-nanometer scale. Entropy contributions make mixed Au-Ni clusters more stable than the unmixed counterpart already at 650 K while unmixed Co clusters remain energetically more favored up to 1295 K and iron clusters are predicted to be stable against intermixing over the experimentally relevant range of temperatures (up to 1100 °C). Remarkably, the net charge donated from the three triade atoms to atomic gold upon intermixing is similar in triade sub-nanometeric clusters and at extended triade surfaces. Gold clusters are prone to host Fe, Co, and Ni atoms at the center of their structures and the exchange process is predicted to be exothermic at 0 K even for a small cluster made of 13 atoms. More generally, our work highlights the importance of the polarity of the chemical bond between unlike metal atoms in alloys.
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18
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Diez JA, González AG, Garfinkel DA, Rack PD, McKeown JT, Kondic L. Simultaneous Decomposition and Dewetting of Nanoscale Alloys: A Comparison of Experiment and Theory. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:2575-2585. [PMID: 33587633 DOI: 10.1021/acs.langmuir.0c02964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We consider the coupled process of phase separation and dewetting of metal alloys of nanoscale thickness deposited on solid substrates. The experiments involve applying nanosecond laser pulses that melt the Ag40Ni60 alloy films in two setups: either on thin supporting membranes or on bulk substrates. These two setups allow for extracting both temporal and spatial scales on which the considered processes occur. The theoretical model involves a longwave version of the Cahn-Hilliard formulation used to describe spinodal decomposition, coupled with an asymptotically consistent longwave-based description of dewetting that occurs due to destabilizing interactions between the alloy and the substrate, modeled using the disjoining pressure approach. Careful modeling, combined with linear stability analysis and fully nonlinear simulations, leads to results consistent with the experiments. In particular, we find that the two instability mechanisms occur concurrently, with the phase separation occurring faster and on shorter temporal scales. The modeling results show a strong influence of the temperature dependence of relevant material properties, implying that such a dependence is crucial for the understanding of the experimental findings. The agreement between theory and experiment suggests the utility of the proposed theoretical approach in helping to develop further experiments directed toward formation of metallic alloy nanoparticles of desired properties.
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Affiliation(s)
- Javier A Diez
- CIFICEN-CONICET-CICPBA, Instituto de Física Arroyo Seco, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, 7000 Tandil, Argentina
| | - Alejandro G González
- CIFICEN-CONICET-CICPBA, Instituto de Física Arroyo Seco, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, 7000 Tandil, Argentina
| | - David A Garfinkel
- Department of Materials Science & Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Philip D Rack
- Department of Materials Science & Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Joseph T McKeown
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Lou Kondic
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
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19
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Ernst WE, Hauser AW. Metal clusters synthesized in helium droplets: structure and dynamics from experiment and theory. Phys Chem Chem Phys 2020; 23:7553-7574. [PMID: 33057510 DOI: 10.1039/d0cp04349d] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Metal clusters have drawn continuous interest because of their high potential for the assembly of matter with special properties that may significantly differ from the corresponding bulk. Controlled combination of particular elements in one nanoparticle can increase the options for the creation of new materials for photonic, catalytic, or electronic applications. Superfluid helium droplets provide confinement and ultralow temperature, i.e. an ideal environment for the atom-by-atom aggregation of a new nanoparticle. This perspective presents a review of the current research progress on the synthesis of tailored metal and metal oxide clusters including core-shell designs, their characterization within the helium droplet beam, deposition on various solid substrates, and analysis via surface diagnostics. Special attention is given to the thermal properties of mixed metal clusters and questions about alloy formation on the nanoscale. Experimental results are accompanied by theoretical approaches employing computational chemistry, molecular dynamics simulations and He density functional theory.
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Affiliation(s)
- Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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20
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Schnedlitz M, Knez D, Lasserus M, Hofer F, Fernández-Perea R, Hauser AW, Pilar de Lara-Castells M, Ernst WE. Thermally Induced Diffusion and Restructuring of Iron Triade (Fe, Co, Ni) Nanoparticles Passivated by Several Layers of Gold. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:16680-16688. [PMID: 32765801 PMCID: PMC7397372 DOI: 10.1021/acs.jpcc.0c04561] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 07/09/2020] [Indexed: 05/21/2023]
Abstract
The temperature-induced structural changes of Fe-, Co-, and Ni-Au core-shell nanoparticles with diameters around 5 nm are studied via atomically resolved transmission electron microscopy. We observe structural transitions from local toward global energy minima induced by elevated temperatures. The experimental observations are accompanied by a computational modeling of all core-shell particles with either centralized or decentralized core positions. The embedded atom model is employed and further supported by density functional theory calculations. We provide a detailed comparison of vacancy formation energies obtained for all materials involved in order to explain the variations in the restructuring processes which we observe in temperature-programmed TEM studies of the particles.
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Affiliation(s)
- Martin Schnedlitz
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Daniel Knez
- Institute
for Electron Microscopy and Nanoanalysis & Graz Centre for Electron
Microscopy, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria
| | - Maximilian Lasserus
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Ferdinand Hofer
- Institute
for Electron Microscopy and Nanoanalysis & Graz Centre for Electron
Microscopy, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria
| | | | - Andreas W. Hauser
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
| | | | - Wolfgang E. Ernst
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
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21
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Zhang J, Bradford SD, Kong W, Zhang C, Xue L. Electron diffraction of CS 2 nanoclusters embedded in superfluid helium droplets. J Chem Phys 2020; 152:224306. [PMID: 32534524 PMCID: PMC7292678 DOI: 10.1063/5.0011340] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 05/25/2020] [Indexed: 11/14/2022] Open
Abstract
We report experimental results from electron diffraction of CS2 nanoclusters embedded in superfluid helium droplets. From detailed measurements of the sizes of doped droplets, we can model the doping statistics under different experimental conditions, thereby obtaining the range of cluster sizes of CS2. Using a least squares fitting procedure, we can then determine the structures and contributions of dimers, trimers, and tetramers embedded in small droplets. While dimers prefer a stable gas phase structure, trimers and tetramers seem to forgo the highly symmetric gas phase structures and prefer compact cuts from the crystalline structure of CS2. In larger droplets containing more than 12 CS2 monomers, the diffraction profile is consistent with a three-dimensional nanostructure of bulk CS2. This work demonstrates the feasibility of electron diffraction for in situ monitoring of nanocluster formation in superfluid helium droplets.
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Affiliation(s)
- Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Stephen D. Bradford
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Chengzhu Zhang
- Department of Statistics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Lan Xue
- Department of Statistics, Oregon State University, Corvallis, Oregon 97331, USA
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