1
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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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Brown CD, Wang Y, Namazi M, Harris GI, Uysal MT, Harris JGE. Superfluid Helium Drops Levitated in High Vacuum. PHYSICAL REVIEW LETTERS 2023; 130:216001. [PMID: 37295082 DOI: 10.1103/physrevlett.130.216001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 01/19/2023] [Accepted: 04/04/2023] [Indexed: 06/12/2023]
Abstract
We demonstrate the trapping of millimeter-scale superfluid helium drops in high vacuum. The drops are sufficiently isolated that they remain trapped indefinitely, cool by evaporation to 330 mK, and exhibit mechanical damping that is limited by internal processes. The drops are also shown to host optical whispering gallery modes. The approach described here combines the advantages of multiple techniques, and should offer access to new experimental regimes of cold chemistry, superfluid physics, and optomechanics.
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Affiliation(s)
- C D Brown
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
| | - Y Wang
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - M Namazi
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
| | - G I Harris
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- AARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - M T Uysal
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - J G E Harris
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Yale Quantum Institute, Yale University, New Haven, Connecticut 06520, USA
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
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3
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Alić J, Messner R, Alešković M, Küstner F, Rubčić M, Lackner F, Ernst WE, Šekutor M. Diamondoid ether clusters in helium nanodroplets. Phys Chem Chem Phys 2023; 25:11951-11958. [PMID: 36942672 PMCID: PMC10155488 DOI: 10.1039/d3cp00489a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Abstract
Diamondoid ethers were introduced into superfluid helium nanodroplets and the resulting clusters were analyzed by time-of-flight mass spectrometry. Clusters of higher abundances (magic number clusters) were identified and the corresponding potential cluster geometries were obtained from GFN2-xTB and DFT computations. We found that the studied diamondoid ethers readily self-assemble in helium nanodroplets and that London dispersion attraction between hydrocarbon subunits acts as a driving force for cluster formation. On the other hand, hydrogen bonding between ether oxygens and trace water molecules fosters the eventual breakdown of the initial supramolecular aggregate.
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Affiliation(s)
- Jasna Alić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
| | - Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Marija Alešković
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
| | - Florian Küstner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Mirta Rubčić
- Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10 000 Zagreb, Croatia
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Marina Šekutor
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
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4
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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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5
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Efficient Formation of Size-Selected Clusters upon Pickup of Dopants into Multiply Charged Helium Droplets. Int J Mol Sci 2022; 23:ijms23073613. [PMID: 35408968 PMCID: PMC8998201 DOI: 10.3390/ijms23073613] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/18/2022] [Accepted: 03/24/2022] [Indexed: 02/01/2023] Open
Abstract
Properties of clusters often depend critically on the exact number of atomic or molecular building blocks, however, most methods of cluster formation lead to a broad, size distribution and cluster intensity anomalies that are often designated as magic numbers. Here we present a novel approach of breeding size-selected clusters via pickup of dopants into multiply charged helium nanodroplets. The size and charge state of the initially undoped droplets and the vapor pressure of the dopant in the pickup region, determines the size of the dopant cluster ions that are extracted from the host droplets, via evaporation of the helium matrix in a collision cell filled with room temperature helium or via surface collisions. Size distributions of the selected dopant cluster ions are determined utilizing a high-resolution time of flight mass spectrometer. The comparison of the experimental data, with simulations taking into consideration the pickup probability into a shrinking He droplet due to evaporation during the pickup process, provides a simple explanation for the emergence of size distributions that are narrower than Poisson.
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6
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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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7
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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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8
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Tanyag RMP, Bacellar C, Pang W, Bernando C, Gomez LF, Jones CF, Ferguson KR, Kwok J, Anielski D, Belkacem A, Boll R, Bozek J, Carron S, Chen G, Delmas T, Englert L, Epp SW, Erk B, Foucar L, Hartmann R, Hexemer A, Huth M, Leone SR, Ma JH, Marchesini S, Neumark DM, Poon BK, Prell J, Rolles D, Rudek B, Rudenko A, Seifrid M, Swiggers M, Ullrich J, Weise F, Zwart P, Bostedt C, Gessner O, Vilesov AF. Sizes of pure and doped helium droplets from single shot x-ray imaging. J Chem Phys 2022; 156:041102. [PMID: 35105059 DOI: 10.1063/5.0080342] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Advancements in x-ray free-electron lasers on producing ultrashort, ultrabright, and coherent x-ray pulses enable single-shot imaging of fragile nanostructures, such as superfluid helium droplets. This imaging technique gives unique access to the sizes and shapes of individual droplets. In the past, such droplet characteristics have only been indirectly inferred by ensemble averaging techniques. Here, we report on the size distributions of both pure and doped droplets collected from single-shot x-ray imaging and produced from the free-jet expansion of helium through a 5 μm diameter nozzle at 20 bars and nozzle temperatures ranging from 4.2 to 9 K. This work extends the measurement of large helium nanodroplets containing 109-1011 atoms, which are shown to follow an exponential size distribution. Additionally, we demonstrate that the size distributions of the doped droplets follow those of the pure droplets at the same stagnation condition but with smaller average sizes.
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Affiliation(s)
- Rico Mayro P Tanyag
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Camila Bacellar
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Weiwu Pang
- Department of Computer Science, University of Southern California, Los Angeles, California 90089, USA
| | - Charles Bernando
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, USA
| | - Luis F Gomez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Curtis F Jones
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Ken R Ferguson
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Justin Kwok
- Department of Chemical Engineering and Material Science, University of Southern California, Los Angeles, California 90089, USA
| | - Denis Anielski
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Ali Belkacem
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Rebecca Boll
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - John Bozek
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Sebastian Carron
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Gang Chen
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Tjark Delmas
- Center for Free-Electron Laser Science (CFEL), Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
| | - Lars Englert
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85741 Garching, Germany
| | - Sascha W Epp
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Benjamin Erk
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Lutz Foucar
- Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany
| | | | - Alexander Hexemer
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Martin Huth
- PNSensor GmbH, Otto-Hahn-Ring 6, 81739 München, Germany
| | - Stephen R Leone
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jonathan H Ma
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Stefano Marchesini
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Daniel M Neumark
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Billy K Poon
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - James Prell
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Daniel Rolles
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Benedikt Rudek
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Artem Rudenko
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Martin Seifrid
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Michele Swiggers
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Joachim Ullrich
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Fabian Weise
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Petrus Zwart
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Christoph Bostedt
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Oliver Gessner
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Andrey F Vilesov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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9
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López-Martín R, Burgos BS, Normile PS, De Toro JA, Binns C. Gas Phase Synthesis of Multi-Element Nanoparticles. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:2803. [PMID: 34835568 PMCID: PMC8618514 DOI: 10.3390/nano11112803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 10/01/2021] [Accepted: 10/04/2021] [Indexed: 11/16/2022]
Abstract
The advantages of gas-phase synthesis of nanoparticles in terms of size control and flexibility in choice of materials is well known. There is increasing interest in synthesizing multi-element nanoparticles in order to optimize their performance in specific applications, and here, the flexibility of material choice is a key advantage. Mixtures of almost any solid materials can be manufactured and in the case of core-shell particles, there is independent control over core size and shell thickness. This review presents different methods of producing multi-element nanoparticles, including the use of multiple targets, alloy targets and in-line deposition methods to coat pre-formed cores. It also discusses the factors that produce alloy, core-shell or Janus morphologies and what is possible or not to synthesize. Some applications of multi-element nanoparticles in medicine will be described.
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Affiliation(s)
| | | | | | | | - Chris Binns
- Departamento de Física Aplicada, Instituto Regional de Investigación Científica Aplicada (IRICA), Universidad de Castilla la Mancha, 13071 Ciudad Real, Spain; (R.L.-M.); (B.S.B.); (P.S.N.); (J.A.D.T.)
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10
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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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11
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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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12
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Alić J, Messner R, Lackner F, Ernst WE, Šekutor M. London dispersion dominating diamantane packing in helium nanodroplets. Phys Chem Chem Phys 2021; 23:21833-21839. [PMID: 34554159 PMCID: PMC8494270 DOI: 10.1039/d1cp03380h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 09/16/2021] [Indexed: 11/21/2022]
Abstract
Diamantane clusters formed inside superfluid helium nanodroplets were analyzed by time-of-flight mass spectrometry. Distinct cluster sizes were identified as "magic numbers" and the corresponding feasible structures for clusters consisting of up to 19 diamantane molecules were derived from meta-dynamics simulations and subsequent DFT computations. The obtained interaction energies were attributed to London dispersion attraction. Our findings demonstrate that diamantane units readily form assemblies even at low pressures and near-zero Kelvin temperatures, confirming the importance of the intermolecular dispersion effect for condensation of matter.
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Affiliation(s)
- Jasna Alić
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
| | - Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Marina Šekutor
- Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10 000 Zagreb, Croatia.
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13
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Laimer F, Zappa F, Scheier P. Size and Velocity Distribution of Negatively Charged Helium Nanodroplets. J Phys Chem A 2021; 125:7662-7669. [PMID: 34449223 PMCID: PMC9282675 DOI: 10.1021/acs.jpca.1c05619] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Precharged helium nanodroplets can be used in doping experiments with the advantage that they are amenable to size selection with electrostatic fields, therefore adding a useful tuning parameter for dopant growth. For all these applications, the knowledge of the size distribution of charged droplets is an essential parameter, which we have so far assumed would be equivalent to that of their neutral precursors. Here, this assumption is experimentally investigated for negatively charged clusters for temperatures between 4 and 9 K at a stagnation pressure of 2 MPa. We observe a dependency of the velocity of the droplets on mass per charge, especially at the lowest temperatures of the investigated range, and values 20% lower than those known from the literature. Below 6 K, a large deviation from the literature is also found for the average droplet sizes. This information has to be taken into consideration in future experiments where large, charged droplets are sought to produce large dopant clusters. Possible origins for this deviation are discussed in the text.
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Affiliation(s)
- F Laimer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
| | - F Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria.,Departamento de Física-ICE, Universidade Federal de Juiz de Fora, Campus Universitário, 36036-900 Juiz de Fora, Minas Gerais, Brazil
| | - P Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria
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14
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Complexes with Atomic Gold Ions: Efficient Bis-Ligand Formation. Molecules 2021; 26:molecules26123484. [PMID: 34201126 PMCID: PMC8228841 DOI: 10.3390/molecules26123484] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 05/31/2021] [Accepted: 06/04/2021] [Indexed: 11/25/2022] Open
Abstract
Complexes of atomic gold with a variety of ligands have been formed by passing helium nanodroplets (HNDs) through two pickup cells containing gold vapor and the vapor of another dopant, namely a rare gas, a diatomic molecule (H2, N2, O2, I2, P2), or various polyatomic molecules (H2O, CO2, SF6, C6H6, adamantane, imidazole, dicyclopentadiene, and fullerene). The doped HNDs were irradiated by electrons; ensuing cations were identified in a high-resolution mass spectrometer. Anions were detected for benzene, dicyclopentadiene, and fullerene. For most ligands L, the abundance distribution of AuLn+ versus size n displays a remarkable enhancement at n = 2. The propensity towards bis-ligand formation is attributed to the formation of covalent bonds in Au+L2 which adopt a dumbbell structure, L-Au+-L, as previously found for L = Xe and C60. Another interesting observation is the effect of gold on the degree of ionization-induced intramolecular fragmentation. For most systems gold enhances the fragmentation, i.e., intramolecular fragmentation in AuLn+ is larger than in pure Ln+. Hydrogen, on the other hand, behaves differently, as intramolecular fragmentation in Au(H2)n+ is weaker than in pure (H2)n+ by an order of magnitude.
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16
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Messner R, Ernst WE, Lackner F. Shell-Isolated Au Nanoparticles Functionalized with Rhodamine B Fluorophores in Helium Nanodroplets. J Phys Chem Lett 2021; 12:145-150. [PMID: 33315408 PMCID: PMC7812593 DOI: 10.1021/acs.jpclett.0c03399] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 12/07/2020] [Indexed: 05/08/2023]
Abstract
Nanoparticles consisting of three different materials in a layered core@shell@shell structure are synthesized in cold helium droplets by sequential doping. Upon the formation of Au core particles, a first shell layer is formed by adding either Ar, isopropyl alcohol, or hexane. Subsequently, the droplets are doped with rhodamine B (RB) molecules; fluorescence spectra recorded upon laser excitation at 532 nm provide insight into the structure of the formed complexes. For the two-component Au@RB system, the RB fluorescence is quenched in the presence of the Au core. If an intermediate isolating shell layer is introduced (Au@shell@RB), the fluorescence increases again. The results demonstrate that shell-isolated nanoparticles can be formed inside He nanodroplets and functionalized in situ with additional molecules. As the structure of the particles depends on the pickup sequence, the approach can be exploited for the synthesis and investigation of a large variety of different combinations of plasmonic metals, intermediate layers, and molecules.
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Affiliation(s)
- Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU
| | - Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria/EU
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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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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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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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Alghamdi M, Zhang J, Kong W. Doping with multiple cations and failure of charge transfer in large ionized helium droplets. J Chem Phys 2019; 151:134307. [PMID: 31594345 DOI: 10.1063/1.5123735] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report experimental observations of aniline (A) cations and He2 + when aniline is doped into ionized helium droplets. Large droplets containing 108 atoms are bombarded by energetic electrons, resulting in more than one positive charge in one droplet. When aniline encounters the charged droplets, some are ionized via charge transfer, while others can remain neutral in the presence of He2 + when the mass-to-charge ratio (m/z) of the droplet is sufficiently large. Upon resonant excitation of the dopant An or An + (n ≥ 1), He2 + can be ejected. The excitation spectrum of He2 + becomes a juxtaposition of the spectra of An and An +. Moreover, an anticorrelation between the yields of He2 + and A+ is observed with increasing energies of the ionizing electrons. We attribute this result to the combined effect of reduction in m/z of the droplets and the different locations of He2 + and neutral An. Limited by the penetration depths of the ionizing electrons and further assisted by the Coulomb repulsion of coexisting cations, He2 + is located within 20 nm of the surface, while neutral An has an average position inside a large droplet. Upon resonant excitation of the interior An, He2 + is preferentially ejected. With increasing energies of the colliding electrons, the m/z of the droplets are reduced, leading to less effective charge shielding and more effective charge transfer, until ultimately, all He2 + can be neutralized to form A+.
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Affiliation(s)
- Maha Alghamdi
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Jie Zhang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
| | - Wei Kong
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA
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Lasserus M, Knez D, Lackner F, Schnedlitz M, Messner R, Schennach D, Kothleitner G, Hofer F, Hauser AW, Ernst WE. Synthesis of nanosized vanadium(v) oxide clusters below 10 nm. Phys Chem Chem Phys 2019; 21:21104-21108. [PMID: 31528952 DOI: 10.1039/c9cp04357h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Vanadium oxide clusters with a mean diameter below 10 nm are investigated by high resolution Scanning Transmission Electron Microscopy (STEM), Electron Energy Loss Spectroscopy (EELS) and UV-vis absorption spectroscopy. The clusters are synthesised by sublimation from bulk vanadium(v) oxide, in combination with a pick-up by superfluid helium droplets. The latter act as reaction chambers which enable cluster growth under fully inert and solvent-free conditions. High-resolution STEM images of deposited vanadium oxide particles allowing for the determination of lattice constants, clearly indicate a dominating presence of V2O5. This finding is further supported by UV-vis absorption spectra of nanoparticles after deposition on fused silica substrates, which indicates that the oxidation state of the material is preserved over the entire process. From the results of the UV-vis measurement, the band gap of the nanosized V2O5 could be determined to be 3.3 eV. The synthesis approach provides a route to clean V2O5 clusters as it does not involve any surfactant or solvents, which is crucial for an unbiased measurement of intrinsic catalyst properties.
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Affiliation(s)
- Maximilian Lasserus
- 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
| | - Florian Lackner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Martin Schnedlitz
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Daniel Schennach
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Gerald Kothleitner
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, Graz University of Technology, Steyrergasse 17, 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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22
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Abstract
We report suppression of multiphoton ionization (MPI) of aniline doped large superfluid helium droplets containing over 5 × 106 atoms. In contrast, surface-bound sodium atoms and dimers are readily desorbed and ionized. Adequacy of the experimental conditions is also confirmed from ejection of embedded aniline cations from smaller droplets containing multiple cations, and MPI of gaseous aniline. The photoelectrons have a mean-free-path of less than 1 nm and a thermalization distance of 10 nm. In a droplet with a diameter of over 70 nm, effective charge recombination within the droplet is expected.
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Schnedlitz M, Fernandez-Perea R, Knez D, Lasserus M, Schiffmann A, Hofer F, Hauser AW, de Lara-Castells MP, Ernst WE. Effects of the Core Location on the Structural Stability of Ni-Au Core-Shell Nanoparticles. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2019; 123:20037-20043. [PMID: 33014236 PMCID: PMC7526986 DOI: 10.1021/acs.jpcc.9b05765] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 07/18/2019] [Indexed: 05/14/2023]
Abstract
Structural changes of Ni-Au core-shell nanoparticles with increasing temperature are studied at atomic resolution. The bimetallic clusters, synthesized in superfluid helium droplets, show a centralized Ni core, which is an intrinsic feature of the growth process inside helium. After deposition on SiN x , the nanoparticles undergo a programmed temperature treatment in vacuum combined with an in situ transmission electron microscopy study of structural changes. We observe not only full alloying far below the actual melting temperature, but also a significantly higher stability of core-shell structures with decentralized Ni cores. Explanations are provided by large-scale molecular dynamics simulations on model structures consisting of up to 3000 metal atoms. Two entirely different diffusion processes can be identified for both types of core-shell structures, strikingly illustrating how localized, atomic features can still dictate the overall behavior of a nanometer-sized particle.
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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
| | - Alexander Schiffmann
- 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
- E-mail: (A.W.H.)
| | | | - Wolfgang E. Ernst
- Institute
of Experimental Physics, Graz University
of Technology, Petersgasse 16, A-8010 Graz, Austria
- E-mail: . Phone: +43 (316) 873-8140 (W.E.E.)
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Lasserus M, Knez D, Schnedlitz M, Hauser AW, Hofer F, Ernst WE. On the passivation of iron particles at the nanoscale. NANOSCALE ADVANCES 2019; 1:2276-2283. [PMID: 36131962 PMCID: PMC9418694 DOI: 10.1039/c9na00161a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 04/22/2019] [Indexed: 05/08/2023]
Abstract
The oxidation of Fe@Au core@shell clusters with sizes below 5 nm is studied via high resolution scanning transmission electron microscopy. The bimetallic nanoparticles are grown in superfluid helium droplets under fully inert conditions, avoiding any effect of solvents or template structures, and deposited on amorphous carbon. Oxidation resistivity is tested by exposure to oxygen at ambient conditions. The passivating effect of Au-shells is studied in detail and a critical Au shell thickness is determined which keeps the Fe core completely unharmed. Additionally, we present the first synthesis of Fe@Au@Fe-oxide onion-type structures.
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Affiliation(s)
- Maximilian Lasserus
- Institute of Experimental Physics, Graz University of Technology Petersgasse 16 A-8010 Graz Austria +43-316-873-108140 +43-316-873-8157 +43-316-873-8140
| | - Daniel Knez
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, Graz University of Technology Steyrergasse 17 A-8010 Graz Austria
| | - Martin Schnedlitz
- Institute of Experimental Physics, Graz University of Technology Petersgasse 16 A-8010 Graz Austria +43-316-873-108140 +43-316-873-8157 +43-316-873-8140
| | - Andreas W Hauser
- Institute of Experimental Physics, Graz University of Technology Petersgasse 16 A-8010 Graz Austria +43-316-873-108140 +43-316-873-8157 +43-316-873-8140
| | - Ferdinand Hofer
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, Graz University of Technology Steyrergasse 17 A-8010 Graz Austria
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology Petersgasse 16 A-8010 Graz Austria +43-316-873-108140 +43-316-873-8157 +43-316-873-8140
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25
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Lasserus M, Schnedlitz M, Messner R, Lackner F, Ernst WE, Hauser AW. Vanadium(V) oxide clusters synthesized by sublimation from bulk under fully inert conditions. Chem Sci 2019; 10:3473-3480. [PMID: 30996937 PMCID: PMC6432649 DOI: 10.1039/c8sc05699d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 02/23/2019] [Indexed: 12/01/2022] Open
Abstract
While laser ablation in combination with electron impact mass spectroscopy yield numerous fragments and reaction products, helium-mediated mass analysis reveals the sublimation from bulk in units of (V2O5)2.
Oxide nanoparticles in the size range of a few nanometers are typically synthesized in solution or via laser ablation techniques, which open numerous channels for structural change via chemical reactions or fragmentation processes. In this work, neutral vanadium oxide nanoparticles are instead synthesized by sublimation from bulk in combination with a pickup by superfluid helium droplets. Mass spectroscopy measurements clearly demonstrate the preservation of the bulk stoichiometric ratio of vanadium to oxygen in He-grown nanoparticles, indicating a tendency towards tetrahedral coordination of the vanadium centers in finite geometries. This unexpected finding opens up new possibilities for a combined on-the-fly synthesis of nanoparticles consisting of metal and metal-oxide layers. In comparison to mass spectra obtained via direct ionization of vanadium oxide in an effusive beam, where strong fragmentation occurred, we observe a clear preference for (V2O5)n oligomers with even n inside the He nanodroplets, which is further investigated and explained using the electronic structure theory.
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Affiliation(s)
- Maximilian Lasserus
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; ; Tel: +43 316 873 8157 ; Tel: +43 316 873 8140
| | - Martin Schnedlitz
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; ; Tel: +43 316 873 8157 ; Tel: +43 316 873 8140
| | - Roman Messner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; ; Tel: +43 316 873 8157 ; Tel: +43 316 873 8140
| | - Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; ; Tel: +43 316 873 8157 ; Tel: +43 316 873 8140
| | - Wolfgang E Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; ; Tel: +43 316 873 8157 ; Tel: +43 316 873 8140
| | - Andreas W Hauser
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; ; Tel: +43 316 873 8157 ; Tel: +43 316 873 8140
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26
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Shcherbinin M, Westergaard FV, Hanif M, Krishnan SR, LaForge AC, Richter R, Pfeifer T, Mudrich M. Inelastic scattering of photoelectrons from He nanodroplets. J Chem Phys 2019; 150:044304. [PMID: 30709284 DOI: 10.1063/1.5074130] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We present a detailed study of inelastic energy-loss collisions of photoelectrons emitted from He nanodroplets by tunable extreme ultraviolet (XUV) radiation. Using coincidence imaging detection of electrons and ions, we probe the lowest He droplet excited states up to the electron impact ionization threshold. We find significant signal contributions from photoelectrons emitted from free He atoms accompanying the He nanodroplet beam. Furthermore, signal contributions from photoionization and electron impact excitation/ionization occurring in pairs of nearest-neighbor atoms in the He droplets are detected. This work highlights the importance of inelastic electron scattering in the interaction of nanoparticles with XUV radiation.
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Affiliation(s)
- M Shcherbinin
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - F Vad Westergaard
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - M Hanif
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
| | - S R Krishnan
- Department of Physics, Indian Institute of Technology, Madras, Chennai 600 036, India
| | - A C LaForge
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - R Richter
- Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy
| | - T Pfeifer
- Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany
| | - M Mudrich
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
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Knez D, Schnedlitz M, Lasserus M, Schiffmann A, Ernst WE, Hofer F. Modelling electron beam induced dynamics in metallic nanoclusters. Ultramicroscopy 2018; 192:69-79. [DOI: 10.1016/j.ultramic.2018.05.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/20/2018] [Accepted: 05/29/2018] [Indexed: 10/14/2022]
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Messner R, Schiffmann A, Pototschnig JV, Lasserus M, Schnedlitz M, Lackner F, Ernst WE. Spectroscopy of gold atoms and gold oligomers in helium nanodroplets. J Chem Phys 2018; 149:024305. [PMID: 30007398 DOI: 10.1063/1.5026480] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The 6p 2P1/2 ← 6s 2S1/2 and 6p 2P3/2 ← 6s 2S1/2 transitions (D lines) of gold atoms embedded in superfluid helium nanodroplets have been investigated using resonant two-photon ionization spectroscopy. Both transitions are strongly blue-shifted and broadened due to the repulsive interaction between the Au valence electron and the surrounding helium. The in-droplet D lines are superimposed by the spectral signature of Au atoms relaxed into the metastable 2D states. These features are narrower than the in-droplet D lines and exhibit sharp rising edges that coincide with bare atom transitions. It is concluded that they originate from metastable 2D state AuHen exciplexes that have been ejected from the helium droplets during a relaxation process. Interestingly, the mechanism that leads to the formation of these complexes is suppressed for very large helium droplets consisting of about 2 × 106 He atoms, corresponding to a droplet diameter on the order of 50 nm. The assignment of the observed spectral features is supported by ab initio calculations employing a multiconfigurational self-consistent field method and a multi-reference configuration interaction calculation. For large helium droplets doped with Au oligomers, excitation spectra for mass channels corresponding to Aun with n = 2, 3, 4, 5, 7, and 9 are presented. The mass spectrum reveals even-odd oscillations in the number of Au atoms that constitute the oligomer, which is characteristic for coinage metal clusters. Resonances are observed close by the in-droplet D1 and D2 transitions, and the corresponding peak forms are very similar for different oligomer sizes.
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Affiliation(s)
- Roman Messner
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Alexander Schiffmann
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Johann V Pototschnig
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Maximilian Lasserus
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Martin Schnedlitz
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
| | - Florian Lackner
- 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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29
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Schnedlitz M, Lasserus M, Knez D, Hauser AW, Hofer F, Ernst WE. Thermally induced breakup of metallic nanowires: experiment and theory. Phys Chem Chem Phys 2018; 19:9402-9408. [PMID: 28327747 DOI: 10.1039/c7cp00463j] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We present time-resolved transmission electron microscopy studies of the degradation of Au, Ag, Cu and Ni nanowires deposited on a heated support. The wires are grown under fully inert conditions in superfluid helium droplets and deposited onto amorphous carbon. The inherent stability of these pristine metal nanowires with diameters below 10 nm is investigated in the absence of any stabilizers, templates or solvents. The phenomenon of Rayleigh-breakup, a consequence of diffusion processes along the wire surfaces, is analysed in situ via scans over time and support temperature. Our experimental efforts are combined with simulations based on a novel model featuring a cellular automaton to emulate surface diffusion. Based on this model, correlations between the material parameters and actual breakup behaviour are studied.
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Affiliation(s)
- Martin Schnedlitz
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
| | - Maximilian Lasserus
- 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
| | - Andreas W Hauser
- 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
| | - Wolfgang E Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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30
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Lasserus M, Schnedlitz M, Knez D, Messner R, Schiffmann A, Lackner F, Hauser AW, Hofer F, Ernst WE. Thermally induced alloying processes in a bimetallic system at the nanoscale: AgAu sub-5 nm core-shell particles studied at atomic resolution. NANOSCALE 2018; 10:2017-2024. [PMID: 29319708 PMCID: PMC5795486 DOI: 10.1039/c7nr07286d] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 12/31/2017] [Indexed: 05/24/2023]
Abstract
Alloying processes in nanometre-sized Ag@Au and Au@Ag core@shell particles with average radii of 2 nm are studied via high resolution Transmission Electron Microscopy (TEM) imaging on in situ heatable carbon substrates. The bimetallic clusters are synthesized in small droplets of superfluid helium under fully inert conditions. After deposition, they are monitored during a heating cycle to 600 K and subsequent cooling. The core-shell structure, a sharply defined feature of the TEM High-Angle Annular Dark-Field images taken at room temperature, begins to blur with increasing temperature and transforms into a fully mixed alloy around 573 K. This transition is studied at atomic resolution, giving insights into the alloying process with unprecedented precision. A new image-processing method is presented, which allows a measurement of the temperature-dependent diffusion constant at the nanoscale. The first quantification of this property for a bimetallic structure <5 nm sheds light on the thermodynamics of finite systems and provides new input for current theoretical models derived from bulk data.
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Affiliation(s)
- Maximilian Lasserus
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; Fax: +43 (316) 873-108140 ; Tel: +43 (316) 873-8157 ; Tel: +43 (316) 873-8140
| | - Martin Schnedlitz
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; Fax: +43 (316) 873-108140 ; Tel: +43 (316) 873-8157 ; Tel: +43 (316) 873-8140
| | - Daniel Knez
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy , Graz University of Technology , Steyrergasse 17 , A-8010 Graz , Austria
| | - Roman Messner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; Fax: +43 (316) 873-108140 ; Tel: +43 (316) 873-8157 ; Tel: +43 (316) 873-8140
| | - Alexander Schiffmann
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; Fax: +43 (316) 873-108140 ; Tel: +43 (316) 873-8157 ; Tel: +43 (316) 873-8140
| | - Florian Lackner
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; Fax: +43 (316) 873-108140 ; Tel: +43 (316) 873-8157 ; Tel: +43 (316) 873-8140
| | - Andreas W. Hauser
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; Fax: +43 (316) 873-108140 ; Tel: +43 (316) 873-8157 ; Tel: +43 (316) 873-8140
| | - Ferdinand Hofer
- Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy , Graz University of Technology , Steyrergasse 17 , A-8010 Graz , Austria
| | - Wolfgang E. Ernst
- Institute of Experimental Physics , Graz University of Technology , Petersgasse 16 , A-8010 Graz , Austria . ; ; Fax: +43 (316) 873-108140 ; Tel: +43 (316) 873-8157 ; Tel: +43 (316) 873-8140
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31
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Loginov E, Gomez LF, Sartakov BG, Vilesov AF. Formation of Core-Shell Ethane-Silver Clusters in He Droplets. J Phys Chem A 2017; 121:5978-5982. [PMID: 28723086 DOI: 10.1021/acs.jpca.7b05136] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ethane core-silver shell clusters consisting of several thousand particles have been assembled in helium droplets upon capture of ethane molecules followed by Ag atoms. The composite clusters were studied via infrared laser spectroscopy in the range of the C-H stretching vibrations of ethane. The spectra reveal a splitting of the vibrational bands, which is ascribed to interaction with Ag. A rigorous analysis of band intensities for a varying number of trapped ethane molecules and Ag atoms indicates that the composite clusters consist of a core of ethane that is covered by relatively small Ag clusters. This metastable structure is stabilized due to fast dissipation in superfluid helium droplets of the cohesion energy of the clusters.
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Affiliation(s)
- Evgeny Loginov
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Luis F Gomez
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Boris G Sartakov
- Prokhorov General Physics Institute, Russian Academy of Sciences , Vavilov Street, 38, 119991 Moscow, Russia
| | - Andrey F Vilesov
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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32
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Yang S, Feng C, Spence D, Al Hindawi AMAA, Latimer E, Ellis AM, Binns C, Peddis D, Dhesi SS, Zhang L, Zhang Y, Trohidou KN, Vasilakaki M, Ntallis N, MacLaren I, de Groot FMF. Robust Ferromagnetism of Chromium Nanoparticles Formed in Superfluid Helium. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1604277. [PMID: 27787938 DOI: 10.1002/adma.201604277] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 09/19/2016] [Indexed: 06/06/2023]
Abstract
Chromium nanoparticles are formed using superfluid helium droplets as the nanoreactors, which are strongly ferromagnetic. The transition from antiferromagentism to ferromagnetism is attributed to atomic-scale disorder in chromium nanoparticles, leading to abundant unbalanced surface spins. Theoretical modeling confirms a frustrated aggregation process in superfluid helium due to the antiferromagnetic nature of chromium.
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Affiliation(s)
- Shengfu Yang
- Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Cheng Feng
- Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Daniel Spence
- Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | | | - Elspeth Latimer
- Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Andrew M Ellis
- Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
| | - Chris Binns
- Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
| | - Davide Peddis
- Institute of Structure of Matter, National Research Council (CNR), 00015, Monterotondo Scalo, Italy
| | - Sarnjeet S Dhesi
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Liying Zhang
- School of Electronics, Information and Electrical Engineering, Shanghai Jiaotong University, Shanghai, 200240, China
| | - Yafei Zhang
- School of Electronics, Information and Electrical Engineering, Shanghai Jiaotong University, Shanghai, 200240, China
| | - Kalliopi N Trohidou
- Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 153 10, Aghia, Greece
| | - Marianna Vasilakaki
- Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 153 10, Aghia, Greece
| | - Nikolaos Ntallis
- Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 153 10, Aghia, Greece
- Department of Physics, Aristotle University, 54124, Thessaloniki, Greece
| | - Ian MacLaren
- Department of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Frank M F de Groot
- Department of Chemistry, Utrecht University, Universiteitsweg 99, 3584CG, Utrecht, The Netherlands
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33
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Buelna X, Freund A, Gonzalez D, Popov E, Eloranta J. Ejection of Metal Particles into Superfluid 4He by Laser Ablation. J Phys Chem B 2016; 120:11010-11017. [DOI: 10.1021/acs.jpcb.6b06594] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xavier Buelna
- Department of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
| | - Adam Freund
- Department of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
| | - Daniel Gonzalez
- Department of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
| | - Evgeny Popov
- Department of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
| | - Jussi Eloranta
- Department of Chemistry and
Biochemistry, California State University at Northridge, 18111
Nordhoff Street, Northridge, California 91330, United States
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34
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35
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Volk A, Thaler P, Knez D, Hauser AW, Steurer J, Grogger W, Hofer F, Ernst WE. The impact of doping rates on the morphologies of silver and gold nanowires grown in helium nanodroplets. Phys Chem Chem Phys 2015; 18:1451-9. [PMID: 26603482 DOI: 10.1039/c5cp06248a] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Silver and gold nanowires are grown within superfluid helium nanodroplets and investigated by high resolution electron microscopy after surface deposition. The wire morphologies depend on the rate of metal atom doping in the pickup sequence. While high doping rates result in a polycrystalline face-centered cubic nanowire structure, at lower doping rates the initial fivefold-symmetry seems to be preserved. An explanation for this observation is given by computer simulations, which allow the derivation of timescales for the nanowire growth process inside helium nanodroplets.
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Affiliation(s)
- Alexander Volk
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
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