1
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Tielens F, Gierada M, Handzlik J, Calatayud M. Characterization of amorphous silica based catalysts using DFT computational methods. Catal Today 2020. [DOI: 10.1016/j.cattod.2019.03.062] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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2
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Kartouzian A. Spectroscopy for model heterogeneous asymmetric catalysis. Chirality 2019; 31:641-657. [PMID: 31318108 DOI: 10.1002/chir.23113] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/02/2019] [Indexed: 12/31/2022]
Abstract
Heterogeneous catalysis has vastly benefited from investigations performed on model systems under well-controlled conditions. The application of most of the techniques utilized for such studies is not feasible for asymmetric reactions as enantiomers possess identical physical and chemical properties unless while interacting with polarized light and other chiral entities. A thorough investigation of a heterogeneous asymmetric catalytic process should include probing the catalyst prior to, during, and after the reaction as well as the analysis of reaction products to evaluate the achieved enantiomeric excess. I present recent studies that demonstrate the strength of chiroptical spectroscopic methods to tackle the challenges in investigating model heterogeneous asymmetric catalysis covering all the abovementioned aspects.
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Affiliation(s)
- Aras Kartouzian
- Lehrstuhl für physikalische Chemie, Catalysis Research Center, Technische Universität München, Garching bei München, Germany
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3
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Theoretical study of O2 interaction with subnanometer-sized Ag clusters supported on defective SiO2 surface. COMPUT THEOR CHEM 2018. [DOI: 10.1016/j.comptc.2018.10.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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4
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Ruiz Puigdollers A, Schlexer P, Tosoni S, Pacchioni G. Increasing Oxide Reducibility: The Role of Metal/Oxide Interfaces in the Formation of Oxygen Vacancies. ACS Catal 2017. [DOI: 10.1021/acscatal.7b01913] [Citation(s) in RCA: 423] [Impact Index Per Article: 60.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Antonio Ruiz Puigdollers
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
| | - Philomena Schlexer
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
| | - Sergio Tosoni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 55 I-20125 Milano, Italy
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5
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Active sites formation and their transformations during ethylene polymerization by the Phillips CrOx/SiO2 catalyst. J Catal 2017. [DOI: 10.1016/j.jcat.2017.05.025] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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6
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Johnson GE, Gunaratne D, Laskin J. Soft- and reactive landing of ions onto surfaces: Concepts and applications. MASS SPECTROMETRY REVIEWS 2016; 35:439-479. [PMID: 25880894 DOI: 10.1002/mas.21451] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 10/31/2014] [Indexed: 06/04/2023]
Abstract
Soft- and reactive landing of mass-selected ions is gaining attention as a promising approach for the precisely-controlled preparation of materials on surfaces that are not amenable to deposition using conventional methods. A broad range of ionization sources and mass filters are available that make ion soft-landing a versatile tool for surface modification using beams of hyperthermal (<100 eV) ions. The ability to select the mass-to-charge ratio of the ion, its kinetic energy and charge state, along with precise control of the size, shape, and position of the ion beam on the deposition target distinguishes ion soft landing from other surface modification techniques. Soft- and reactive landing have been used to prepare interfaces for practical applications as well as precisely-defined model surfaces for fundamental investigations in chemistry, physics, and materials science. For instance, soft- and reactive landing have been applied to study the surface chemistry of ions isolated in the gas-phase, prepare arrays of proteins for high-throughput biological screening, produce novel carbon-based and polymer materials, enrich the secondary structure of peptides and the chirality of organic molecules, immobilize electrochemically-active proteins and organometallics on electrodes, create thin films of complex molecules, and immobilize catalytically active organometallics as well as ligated metal clusters. In addition, soft landing has enabled investigation of the size-dependent behavior of bare metal clusters in the critical subnanometer size regime where chemical and physical properties do not scale predictably with size. The morphology, aggregation, and immobilization of larger bare metal nanoparticles, which are directly relevant to the design of catalysts as well as improved memory and electronic devices, have also been studied using ion soft landing. This review article begins in section 1 with a brief introduction to the existing applications of ion soft- and reactive landing. Section 2 provides an overview of the ionization sources and mass filters that have been used to date for soft landing of mass-selected ions. A discussion of the competing processes that occur during ion deposition as well as the types of ions and surfaces that have been investigated follows in section 3. Section 4 discusses the physical phenomena that occur during and after ion soft landing, including retention and reduction of ionic charge along with factors that impact the efficiency of ion deposition. The influence of soft landing on the secondary structure and biological activity of complex ions is addressed in section 5. Lastly, an overview of the structure and mobility as well as the catalytic, optical, magnetic, and redox properties of bare ionic clusters and nanoparticles deposited onto surfaces is presented in section 6.
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Affiliation(s)
- Grant E Johnson
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, MSIN K8-88, Richland, WA, 99352
| | - Don Gunaratne
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, MSIN K8-88, Richland, WA, 99352
| | - Julia Laskin
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, MSIN K8-88, Richland, WA, 99352
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7
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Del Rosal I, Gerber IC, Poteau R, Maron L. Grafting of lanthanide complexes on silica surfaces dehydroxylated at 200 °C: a theoretical investigation. NEW J CHEM 2015. [DOI: 10.1039/c5nj01645b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The grafting reaction of lanthanide silylamide complexes has been studied, in the framework of the DFT, highlighting the different grafting modes on a silica surface dehydroxylated at 200 °C.
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Affiliation(s)
- Iker Del Rosal
- Université de Toulouse
- INSA
- UPS
- LPCNO (IRSAMC)
- F-31077 Toulouse
| | - Iann C. Gerber
- Université de Toulouse
- INSA
- UPS
- LPCNO (IRSAMC)
- F-31077 Toulouse
| | - Romuald Poteau
- Université de Toulouse
- INSA
- UPS
- LPCNO (IRSAMC)
- F-31077 Toulouse
| | - Laurent Maron
- Université de Toulouse
- INSA
- UPS
- LPCNO (IRSAMC)
- F-31077 Toulouse
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8
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Li B, Cui H, Han Y, Gao L, Guo C, Gao C, Wang Y. Simultaneous determination of optical loss, residual reflectance and transmittance of highly anti-reflective coatings with cavity ring down technique. OPTICS EXPRESS 2014; 22:29135-29142. [PMID: 25402152 DOI: 10.1364/oe.22.029135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Cavity ring down (CRD) technique was employed to measure optical losses (absorption and scattering losses), residual reflectance and transmittance of anti-reflectively (AR) coated laser components with transmittance higher than 99.9%. By inserting the AR coated laser component with parallel optical surfaces into the ring-down cavity and measuring the ring-down time versus the angle of incidence with respect to the surface normal, the optical loss and residual reflectance of the laser component were determined respectively at normal and out-of-normal incidences with repeatability of part-per-million level. The transmittance was also determined simultaneously. Experimental results demonstrated that CRD is a simple, inexpensive and fast technique for highly accurate measurements of optical loss, residual reflectance, and transmittance of AR coated laser components widely used in high-power laser systems.
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Ray M, Basu TS, Bandyopadhyay NR, Klie RF, Ghosh S, Raja SO, Dasgupta AK. Highly lattice-mismatched semiconductor-metal hybrid nanostructures: gold nanoparticle encapsulated luminescent silicon quantum dots. NANOSCALE 2014; 6:2201-2210. [PMID: 24382635 DOI: 10.1039/c3nr05960j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Synthesis of hybrid core-shell nanostructures requires moderate lattice mismatch (<5%) between the materials of the core and the shell and usually results in the formation of structures with an atomically larger entity comprising the core. A reverse situation, where an atomically larger entity encapsulates a smaller atomic radius component having substantial lattice mismatch is unachievable by conventional growth techniques. Here, we report successful synthesis of ultra-small, light-emitting Si quantum dots (QDs) encapsulated by Au nanoparticles (NPs) forming a hybrid nanocomposite that exhibits intense room temperature photoluminescence (PL) and intriguing plasmon-exciton coupling. A facile strategy was adopted to utilize the active surface of oxide etched Si QDs as preferential sites for Au NP nucleation and growth which resulted in the formation of core-shell nanostructures consisting of an atomically smaller Si QD core surrounded by a substantially lattice-mismatched Au NP shell. The PL characteristics of the luminescent Si QDs (quantum yield ∼28%) are dramatically altered following Au NP encapsulation. Au coverage of the bare Si QDs effectively stabilizes the emission spectrum and leads to a red-shift of the PL maxima by ∼37 nm. The oxide related PL peaks observed in Si QDs are absent in the Au treated sample suggesting the disappearance of oxide states and the appearance of Au NP associated Stark shifted interface states within the widened band-gap of the Si QDs. Emission kinetics of the hybrid system show accelerated decay due to non-radiative energy transfer between the Si QDs and the Au NPs and associated quenching in PL efficiency. Nevertheless, the quantum yield of the hybrid remains high (∼20%) which renders these hetero-nanostructures exciting candidates for multifarious applications.
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Affiliation(s)
- Mallar Ray
- School of Materials Science and Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711103, West Bengal, India.
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Portale G, Sciortino L, Albonetti C, Giannici F, Martorana A, Bras W, Biscarini F, Longo A. Influence of metal–support interaction on the surface structure of gold nanoclusters deposited on native SiOx/Si substrates. Phys Chem Chem Phys 2014; 16:6649-56. [DOI: 10.1039/c3cp54847c] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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11
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Nasluzov VA, Ivanova-Shor EA, Shor AM, Yudanov IV, Rösch N. Simulation of heterogeneous catalysts and catalytic processes using the density functional method. KINETICS AND CATALYSIS 2010. [DOI: 10.1134/s0023158410060091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Del Rosal I, Gerber IC, Poteau R, Maron L. Grafting of Lanthanide Complexes on Silica Surfaces: A Theoretical Investigation. J Phys Chem A 2010; 114:6322-30. [DOI: 10.1021/jp101495n] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Iker Del Rosal
- Université de Toulouse, INSA, UPS, LPCNO (IRSAMC), 135 avenue de Rangueil, F-31077 Toulouse, France and CNRS, UMR 5215 (IRSAMC), F-31077 Toulouse, France
| | - Iann C. Gerber
- Université de Toulouse, INSA, UPS, LPCNO (IRSAMC), 135 avenue de Rangueil, F-31077 Toulouse, France and CNRS, UMR 5215 (IRSAMC), F-31077 Toulouse, France
| | - Romuald Poteau
- Université de Toulouse, INSA, UPS, LPCNO (IRSAMC), 135 avenue de Rangueil, F-31077 Toulouse, France and CNRS, UMR 5215 (IRSAMC), F-31077 Toulouse, France
| | - Laurent Maron
- Université de Toulouse, INSA, UPS, LPCNO (IRSAMC), 135 avenue de Rangueil, F-31077 Toulouse, France and CNRS, UMR 5215 (IRSAMC), F-31077 Toulouse, France
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13
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Egashira K, Terasaki A, Kondow T. Photon-trap spectroscopy applied to molecules adsorbed on a solid surface: probing with a standing wave versus a propagating wave. APPLIED OPTICS 2010; 49:1151-1157. [PMID: 20197812 DOI: 10.1364/ao.49.001151] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We apply photon-trap spectroscopy, a generalized scheme of cavity ringdown spectroscopy, to infrared spectroscopy of molecular adsorbates on a solid substrate. The storage lifetime of light in a high-finesse Fabry-Perot cavity provides a high absorbance sensitivity for the substrate sample, which is placed exactly normal to the light beam in the cavity to minimize optical losses. Infrared spectra of the C-H stretching vibration of alkylsiloxane monolayer films on a silicon substrate are measured in three ways, namely by employing pulsed and continuous-wave lasers as well as by conventional Fourier transform infrared spectroscopy. The magnitude of optical absorption is shown to vary by the character of the interacting light used in the measurement, i.e., a standing wave versus a propagating wave.
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Affiliation(s)
- Kazuhiro Egashira
- East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan
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14
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Lim DC, Hwang CC, Ganteför G, Kim YD. Model catalysts of supported Au nanoparticles and mass-selected clusters. Phys Chem Chem Phys 2010; 12:15172-80. [DOI: 10.1039/c0cp00467g] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Lim DC, Dietsche R, Ganteför G, Kim YD. Oxidation of deposited Aun (n=2–13) on SiO2/Si: Influence of the NaOH(aq) treatment. Chem Phys 2009. [DOI: 10.1016/j.chemphys.2009.03.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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16
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Cai X, Zhang P, Ma L, Zhang W, Ning X, Zhao L, Zhuang J. Tuning Optical Properties of Magic Number Cluster (SiO2)4O2H4 by Substitutional Bonding with Gold Atoms. J Phys Chem A 2009; 113:4889-94. [DOI: 10.1021/jp811347c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Xiulong Cai
- Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Institute of Modern Physics, Department of Physics, Fudan University, Shanghai 200433, China
| | - Peng Zhang
- Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Institute of Modern Physics, Department of Physics, Fudan University, Shanghai 200433, China
| | - Liuxue Ma
- Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Institute of Modern Physics, Department of Physics, Fudan University, Shanghai 200433, China
| | - Wenxian Zhang
- Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Institute of Modern Physics, Department of Physics, Fudan University, Shanghai 200433, China
| | - Xijing Ning
- Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Institute of Modern Physics, Department of Physics, Fudan University, Shanghai 200433, China
| | - Li Zhao
- Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Institute of Modern Physics, Department of Physics, Fudan University, Shanghai 200433, China
| | - Jun Zhuang
- Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Institute of Modern Physics, Department of Physics, Fudan University, Shanghai 200433, China
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17
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Wang X, Hinz M, Vogelsang M, Welsch T, Kaufmann D, Jones H. A new approach to detecting biologically active substances with evanescent-wave cavity ring-down spectroscopy. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.10.086] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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18
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Pacchioni G. Modeling doped and defective oxides in catalysis with density functional theory methods: room for improvements. J Chem Phys 2008; 128:182505. [PMID: 18532790 DOI: 10.1063/1.2819245] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Due to the well-known problem of the self-interaction, standard density functional theory (DFT) methods tend to produce delocalized holes and electrons in defective oxide materials even when there is ample experimental evidence of a strong localization. For late transition metal compounds or rare earth oxides, this results in the incorrect description of the electronic structure of the system (e.g., magnetic insulators are predicted to be metallic). Practical ways to correct this deficiency are based on the use of hybrid functionals or of the DFT+U approach. In this way, most of the limitations related to the self-interaction are removed, and the electronic structure is properly described. What is less clear is to what extent hybrid functionals, DFT+U approaches, or standard DFT functionals can properly describe the strength of the chemical bonds at the surface of an oxide. This is a crucial question if one is interested in the catalytic properties of oxide surfaces. Oxidation reactions often involve oxygen detachment from the surface and incorporation into an organic substrate. Oxides are doped with heteroatoms to create defects and facilitate oxygen removal from the surface, with formation of oxygen vacancies. Do standard DFT calculations provide a good binding energy of the missing oxygen despite the failure in giving the right electronic structure? Can hybrid functionals or the DFT+U approach provide a simple yet reliable way to get accurate reaction enthalpies and energy barriers? In this essay, we discuss these problems by analyzing some case histories and the relatively scarce data existing in the literature. The conclusion is that while modern electronic structure methods accurately reproduce and predict a wide range of electronic, optical, and magnetic properties of oxides, the description of the strength of chemical bonds still needs considerable improvements.
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Affiliation(s)
- Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi 53, Milan, Italy.
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19
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Lim DC, Dietsche R, Ganteför G, Kim YD. Chemical properties of size-selected Au clusters treated under ambient conditions. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.04.059] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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20
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Eichelbaum M, Rademann K, Hoell A, Tatchev DM, Weigel W, Stößer R, Pacchioni G. Photoluminescence of atomic gold and silver particles in soda-lime silicate glasses. NANOTECHNOLOGY 2008; 19:135701. [PMID: 19636156 DOI: 10.1088/0957-4484/19/13/135701] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report the chemistry and photophysics of atomic gold and silver particles in inorganic glasses. By synchrotron irradiation of gold-doped soda-lime silicate glasses we could create and identify unambiguously the gold dimer as a stable and bright luminescing particle embedded in the glassy matrix. The gold dimer spectra coincide perfectly with rare gas matrix spectra of Au(2). The glass matrix is, however, stable for years, and is hence perfectly suited for various applications. If the irradiated gold-doped sample is annealed at 550 degrees C a bright green luminescence can be recognized. Intense 337 nm excitation induces a decrease of the green luminescence and the reappearance of the 753 nm Au(2) emission, indicating a strong interrelationship between both luminescence centers. Time-dependent density functional theory (TD-DFT) calculations indicate that the green luminescence can be assigned to noble metal dimers bound to silanolate centers. These complexes are recognized as the first stages in the further cluster growth process, which has been investigated with small-angle x-ray scattering (SAXS). In silver-doped glasses, Ag(0) atoms can be identified with electron paramagnetic resonance (EPR) spectroscopy after synchrotron activation. Annealing at 300 degrees C decreases the concentration of Ag(1), but induces an intense white light emission with 337 nm excitation. The white luminescence can be decomposed into bands that are attributed to small silver clusters such as Ag(2), Ag(3) and Ag(4), and an additional band matching the green emission of gold-doped glasses.
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Affiliation(s)
- Maik Eichelbaum
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany
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21
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Giordano L, Martinez U, Sicolo S, Pacchioni G. Observable consequences of formation of Au anions from deposition of Au atoms on ultrathin oxide films. J Chem Phys 2007; 127:144713. [DOI: 10.1063/1.2794339] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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22
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Giordano L, Sushko PV, Pacchioni G, Shluger AL. Electron trapping at point defects on hydroxylated silica surfaces. PHYSICAL REVIEW LETTERS 2007; 99:136801. [PMID: 17930618 DOI: 10.1103/physrevlett.99.136801] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Indexed: 05/25/2023]
Abstract
The origin of electron trapping and negative charging of hydroxylated silica surfaces is predicted based on accurate quantum-mechanical calculations. The calculated electron affinities of the two dominant neutral paramagnetic defects, the nonbridging oxygen center, identical with Si-O*, and the silicon dangling bond, identical with Si*, demonstrate that both defects are deep electron traps and can form the corresponding negatively charged defects. We predict the structure and optical absorption energies of these diamagnetic defects.
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Affiliation(s)
- Livia Giordano
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy
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Abstract
Recent progress in the understanding of the fascinating catalysis of CO combustion by supported gold particles is summarized. Focusing on size-selected gold clusters consisting of only a few atoms, that is, the size regime with properties nonscalable from the bulk properties, we discuss the current knowledge of the different factors controlling the reactivity at the molecular level. These factors include the role of the oxide support, its defects, cluster charging as well as the structural fluxionality of clusters, the cluster size dependency, and the promotional effect of water. By combining experimental results with quantum mechanical ab initio calculations, a detailed picture of the reaction mechanism emerges. While similar mechanisms might be active for gold nanoparticles in the scalable size regime, it is shown that for different systems (defined by the cluster size, the support, experimental conditions, etc.) the reaction mechanism differs and, hence, no generalized explanation for the catalytic driving force of small gold particles can be given.
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Affiliation(s)
- Matthias Arenz
- Lehrstuhl für Physikalische Chemie I, Technische Universität München Lichtenbergstrasse 4, 85747 Garching, Germany
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25
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Egashira K, Terasaki A, Kondow T. Infrared spectra of organic monolayer films in a standing wave measured by photon-trap spectroscopy. J Chem Phys 2007; 126:221102. [PMID: 17581037 DOI: 10.1063/1.2748747] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photon-trap spectroscopy, a generalized scheme of cavity ringdown spectroscopy, is applied to measure an infrared spectrum of the C-H stretching vibration of alkylsiloxane monolayer films grafted on a silicon substrate. A continuous-wave laser beam is introduced into a high-finesse Fabry-Pérot cavity containing the substrate placed exactly normal to the light beam to minimize optical losses. The lifetime of the light trapped in the cavity is measured to detect optical absorption sensitively. The results show clear dependence of the absorbance on the location of the monolayers with respect to a standing wave formed in the cavity; the absorbance is practically zero when the monolayers on both the surfaces are adjusted at nodes, whereas it is maximized at antinodes. The present experiment is materialized on the basis of the principles established by our previous study [Terasaki et al., J. Opt. Soc. Am. B 22, 675 (2005)].
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Affiliation(s)
- Kazuhiro Egashira
- East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan
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26
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Landman U, Yoon B, Zhang C, Heiz U, Arenz M. Factors in gold nanocatalysis: oxidation of CO in the non-scalable size regime. Top Catal 2007. [DOI: 10.1007/s11244-007-0288-6] [Citation(s) in RCA: 150] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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27
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Abstract
Clusters of atoms/molecules show dynamics characteristic of the method of excitation. Two contrasted processes are discussed: (1) electronic excitation via single-photon absorption and (2) impulsive excitation of nuclear motions by surface impact. Process 1 is exemplified by photodissociation dynamics of size-selected metal cluster ions. The electronic energy is converted most likely to vibrational energy of internal modes; dissociation follows via statistical mechanism to produce energetically favored fragments. Exceptionally, a silver cluster ion, Ag4(+), is shown to undergo nonstatistical dissociation along the potential-energy surface of the excited state. Energy partitioning to translational and vibrational modes of fragments is analyzed as well as bond dissociation energies. Furthermore, the spectrum of the photodissociation yield provides electronic and geometrical structures of a cluster with the aid of ab initio calculations; manganese, Mn(N)(+), and chromium, Cr(N)(+), cluster ions are discussed, where the importance of magnetic interactions is manifested. On the other hand, momentum transfer upon surface impact plays a role in process 2. An impulsive mechanical force triggers extraordinary chemical processes distinct from those initiated by atomic collision as well as photoexcitation. Experiments on aluminum, Al(N)(-), silicon, SiN(-), and solvated, I(2)(-)(CO2)(N), cluster anions provide evidence for reactions proceeding under extremely high temperatures, such as pickup of surface atoms, annealing of products, and mechanical splitting of chemical bonds. In addition, a model experiment to visualize and time-resolve the cluster impact process is performed by using a micrometer-sized liquid droplet. Multiphoton absorption initiates superheating of the droplet surface followed by a shock wave and disintegration into a number of small fragments (shattering). These studies further reveal how the nature of chemical bonds influences the dynamics of clusters.
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Affiliation(s)
- Akira Terasaki
- Cluster Research Laboratory, Toyota Technological Institute, in East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan.
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Lim DC, Dietsche R, Bubek M, Ketterer T, Ganteför G, Kim YD. Chemistry of mass-selected Au clusters deposited on sputter-damaged HOPG surfaces: The unique properties of Au8 clusters. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Arenz M, Gilb S, Heiz U. Chapter 1 Size effects in the chemistry of small clusters. ATOMIC CLUSTERS: FROM GAS PHASE TO DEPOSITED 2007. [DOI: 10.1016/s1571-0785(07)12001-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Cinquini F, Valentin CD, Finazzi E, Giordano L, Pacchioni G. Theory of oxides surfaces, interfaces and supported nano-clusters. Theor Chem Acc 2006. [DOI: 10.1007/s00214-006-0204-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Structural, Electronic, and Optical Properties of Noble Metal Clusters from First Principles. J CLUST SCI 2006. [DOI: 10.1007/s10876-006-0075-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Lim DC, Dietsche R, Bubek M, Ganteför G, Kim YD. Oxidation and Reduction of Mass-Selected Au Clusters on SiO2/Si. Chemphyschem 2006; 7:1909-11. [PMID: 16881087 DOI: 10.1002/cphc.200600285] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Dong Chan Lim
- Department of Physics, University of Konstanz Universitätsstrasse 10, 78457 Konstanz, Germany
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Martinez U, Giordano L, Pacchioni G. Nature of Point Defects on SiO2/Mo(112) Thin Films and Their Interaction with Au Atoms. J Phys Chem B 2006; 110:17015-23. [PMID: 16927995 DOI: 10.1021/jp063681e] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have studied by means of periodic DFT calculations the structure and properties of point defects at the surface of ultrathin silica films epitaxially grown on Mo(112) and their interaction with adsorbed Au atoms. For comparison, the same defects have been generated on an unsupported silica film with the same structure. Four defects have been considered: nonbridging oxygen (NBO, [triple bond]Si-O(*)), Si dangling bond (E' center, [triple bond]Si(*)), oxygen vacancy (V(O), [triple bond]Si-Si[triple bond]), and peroxo group ([triple bond]Si-O-O-Si[triple bond]), but only the NBO and the V(O) centers are likely to form on the SiO(2)/Mo(112) films under normal experimental conditions. The [triple bond]Si-O(*) center captures one electron from Mo forming a silanolate group, [triple bond]Si-O(-), sign of a direct interaction with the metal substrate. Apart from the peroxo group, which is unreactive, the other defects bind strongly the Au atom forming stable surface complexes, but their behavior may differ from that of the same centers generated on an unsupported silica film. This is true in particular for the two most likely defects considered, the nonbridging oxygen, [triple bond]Si-O(*), and the oxygen vacancy, [triple bond]Si-Si[triple bond].
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Affiliation(s)
- Umberto Martinez
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi, 53-20125, Milano, Italy
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Joshi AM, Delgass WN, Thomson KT. Adsorption of Small Aun (n = 1−5) and Au−Pd Clusters Inside the TS-1 and S-1 Pores. J Phys Chem B 2006; 110:16439-51. [PMID: 16913775 DOI: 10.1021/jp061754o] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We used a hybrid quantum-mechanics/molecular-mechanics (QM/MM) approach to simulate the adsorption of Au(n)() (n = 1-5), AuPd, and Au(2)Pd(2) clusters inside the TS-1 and S-1 pores. We studied nondefect and metal-vacancy defect sites in TS-1 and S-1 for a total of four different environments around the T6 crystallographic site. We predict stronger binding of all clusters near Ti sites in Ti-substituted framework compared to adsorption near Si sites-consistent with the experimental finding of a direct correlation between the Ti-loading and the Au-loading on the Au/TS-1 catalysts with high Si/Ti ratio. The cluster binding is also stronger near lattice-metal vacancies compared to fully coordinated, nondefect sites. In all the cases, a trend of binding energy (BE) versus Au cluster size (n) shows a peak at around n = 3-4. Our results show that there is enough room for the attack of H(2)O(2) on the Ti-defect site even with Au(1-4) adsorbed-a result that supports the possibility of H(2)O(2) spillover from the Au clusters to the adjacent Ti-defect sites. Mulliken charge analysis indicates that in all the cases there is electron density transfer to adsorbed clusters from the zeolite lattice. In the case of both gas-phase and adsorbed Au-Pd clusters, all the Pd atoms were positively charged, and all the Au atoms were negatively charged due to the higher electron-affinity of Au. We also found a correlation between the BE and the charge transfer to the clusters (the higher the charge transfer to the clusters, the higher the BE), and a universal correlation was found for Au(2-5) when BE and charge transfer were plotted on a per atom basis. A relatively larger charge transfer to the adsorbed clusters was found for the Ti sites versus the Si sites, and for the defect sites versus the nondefect sites. The trends in the BE were corroborated using Gibbs free energy of adsorption (DeltaG(ads)), and the implications of DeltaG(ads) in sintering of Au clusters are also discussed. Our results confirm that electronic factors such as cluster-charging are potentially important support effects for the Au/TS-1 catalyst.
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Affiliation(s)
- Ajay M Joshi
- School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
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Giordano L, Del Vitto A, Pacchioni G. Au and Pd atoms adsorbed on pure and Ti-doped SiO2∕Mo(112) films. J Chem Phys 2006; 124:034701. [PMID: 16438594 DOI: 10.1063/1.2151175] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The interaction of Pd and Au atoms with a silica surface and SiO2Mo(112) ultrathin films has been studied with periodic density-functional theory-generalized gradient approximation calculations. On both unsupported and supported silica, Pd and Au are weakly bound. No charge transfer occurs to the empty Pd and Au orbitals. Differently from Au, Pd can easily penetrate with virtually no barrier into the hexagonal rings of the supported silica film and binds strongly at the SiO2-Mo interface. The same process for Au implies overcoming a barrier of 0.9 eV. Completely different is the behavior of Ti-doped silica films. Au forms a direct covalent bond with substitutional Ti at the expense of the Ti...O-Mo interface bond which breaks. The global process is exothermic by 1 eV and nonactivated, showing that Ti doping results in solid anchoring points for the adsorbed Au atoms and for nucleation and growth of small gold particles. The effect of Ti doping is less pronounced for Pd but still visible with substantial enhancement of the Pd adsorption strength.
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Affiliation(s)
- Livia Giordano
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi 53, 20125 Milano, Italy
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Solans-Monfort X, Filhol JS, Copéret C, Eisenstein O. Structure, spectroscopic and electronic properties of a well defined silica supported olefin metathesis catalyst, [(SiO)Re(CR)(CHR)(CH2R)], through DFT periodic calculations: silica is just a large siloxy ligand. NEW J CHEM 2006. [DOI: 10.1039/b603426h] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Eichelbaum M, Rademann K, Müller R, Radtke M, Riesemeier H, Görner W. Zur Chemie des Goldes in Silicatgläsern: Untersuchungen zum nicht-thermisch aktivierten Wachstum von Goldclustern. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200502174] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Eichelbaum M, Rademann K, Müller R, Radtke M, Riesemeier H, Görner W. On the Chemistry of Gold in Silicate Glasses: Studies on a Nonthermally Activated Growth of Gold Nanoparticles. Angew Chem Int Ed Engl 2005; 44:7905-9. [PMID: 16259030 DOI: 10.1002/anie.200502174] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Maik Eichelbaum
- Institut für Chemie, Humboldt-Universität zu Berlin, Germany
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Del Vitto A, Pacchioni G, Lim KH, Rösch N, Antonietti JM, Michalski M, Heiz U, Jones H. Gold Atoms and Dimers on Amorphous SiO2: Calculation of Optical Properties and Cavity Ringdown Spectroscopy Measurements. J Phys Chem B 2005; 109:19876-84. [PMID: 16853570 DOI: 10.1021/jp054794l] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report on the optical absorption spectra of gold atoms and dimers deposited on amorphous silica in size-selected fashion. Experimental spectra were obtained by cavity ringdown spectroscopy. Issues on soft-landing, fragmentation, and thermal diffusion are discussed on the basis of the experimental results. In parallel, cluster and periodic supercell density functional theory (DFT) calculations were performed to model atoms and dimers trapped on various defect sites of amorphous silica. Optically allowed electronic transitions were calculated, and comparisons with the experimental spectra show that silicon dangling bonds [[triple bond]Si(.-)], nonbridging oxygen [[triple bond]Si-O(.-)], and the silanolate group [[triple bond]Si-O(-)] act as trapping centers for the gold particles. The results are not only important for understanding the chemical bonding of atoms and clusters on oxide surfaces, but they will also be of fundamental interest for photochemical studies of size-selected clusters on surfaces.
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Affiliation(s)
- Annalisa Del Vitto
- Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, via R. Cozzi 53, I-20125 Milano, Italy
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