1
|
High Surface Area VOx/TiO2/SBA-15 Model Catalysts for Ammonia SCR Prepared by Atomic Layer Deposition. Catalysts 2020. [DOI: 10.3390/catal10121386] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The mode of operation of titania-supported vanadia (VOx) catalysts for NOx abatement using ammonia selective catalytic reduction (NH3-SCR) is still vigorously debated. We introduce a new high surface area VOx/TiO2/SBA-15 model catalyst system based on mesoporous silica SBA-15 making use of atomic layer deposition (ALD) for controlled synthesis of titania and vanadia multilayers. The bulk and surface structure is characterized by X-ray diffraction (XRD), UV-vis and Raman spectroscopy, as well as X-ray photoelectron spectroscopy (XPS), revealing the presence of dispersed surface VOx species on amorphous TiO2 domains on SBA-15, forming hybrid Si–O–V and Ti–O–V linkages. Temperature-dependent analysis of the ammonia SCR catalytic activity reveals NOx conversion levels of up to ~60%. In situ and operando diffuse reflection IR Fourier transform (DRIFT) spectroscopy shows N–Hstretching modes, representing adsorbed ammonia and -NH2 and -NH intermediate structures on Bronsted and Lewis acid sites. Partial Lewis acid sites with adjacent redox sites are proposed as the active sites and desorption of product molecules as the rate-determining step at low temperature. The high NOx conversion is attributed to the presence of highly dispersed VOx species and the moderate acidity of VOx supported on TiO2/SBA-15.
Collapse
|
2
|
Martinelli A, Creci S, Vavra S, Carlsson PA, Skoglundh M. Local anisotropy in single crystals of zeotypes with the MFI framework structure evidenced by polarised Raman spectroscopy. Phys Chem Chem Phys 2020; 22:1640-1654. [PMID: 31894792 DOI: 10.1039/c9cp06199a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Polarised Raman spectroscopy is used to characterise the local structure in single crystals of zeotypes, namely silicalite-1 and ZSM-5, which share the MFI framework structure. Attributes favourable for applying polarised Raman spectroscopy are the orthogonal axes of these single crystals and their size, i.e. 10 to 30 micrometers in all three directions. We show that the intensity of certain vibrational modes in silicalite-1 depends on the polarisation of the incident light, reflecting the anisotropic character of the molecular bonds contributing to these vibrations. Using these observations, and by estimating the depolarisation ratio (ρ) and the pseudo-order factor (f), we propose a more accurate assignment of the Raman active modes. More precisely, Raman intensities peaked at 294, 360, 383 and 472 cm-1 are attributed to bending modes in 10-, 6-, 5- and 4-membered rings, respectively. In the region of stretching modes, the vibration at 832 cm-1 is assigned to Si-O-Si bonds shared between 5-membered rings, which have an orientation parallel to the a-axis of the crystal. By virtue of having a strongly polarised character, the modes at 472 and 832 cm-1 can be used as orientational indicators. The proposed assignment is supported by the good agreement between experimental and simulated polar plots, where Raman intensities are plotted as a function of the polarisation angle of the incident light. Finally, upon partial substitution of Si atoms by Al, the crystalline structure is maintained and almost no spectroscopic changes are observed. The only significant difference is the increased width of most vibrational modes, which is consistent with the local lower symmetry. This is also seen in the angular dependence of selected vibrational modes that compared to the case of pure silicalite-1 appear less polarised. In the Raman spectrum of ZSM-5 a new feature at 974 cm-1 is observed, which we attribute to Al-OH stretching. In the high frequency range, the O-H stretching modes are observed which arise from the Si-O(H)-Al Brønsted acid sites. The intensity of the characteristic mode at 3611 cm-1 reveals an anisotropic character as well, which is in line with previous findings from solid state NMR that Al atoms distribute nonrandomly within the MFI framework structure.
Collapse
Affiliation(s)
- Anna Martinelli
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
| | - Simone Creci
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. and Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Szilvia Vavra
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
| | - Per-Anders Carlsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. and Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Magnus Skoglundh
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. and Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| |
Collapse
|
3
|
|
4
|
Vecchione R, Luciani G, Calcagno V, Jakhmola A, Silvestri B, Guarnieri D, Belli V, Costantini A, Netti PA. Multilayered silica-biopolymer nanocapsules with a hydrophobic core and a hydrophilic tunable shell thickness. NANOSCALE 2016; 8:8798-8809. [PMID: 27065306 DOI: 10.1039/c6nr01192f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Stable, biocompatible, multifunctional and multicompartment nanocarriers are much needed in the field of nanomedicine. Here, we report a simple, novel strategy to design an engineered nanocarrier system featuring an oil-core/hybrid polymer/silica-shell. Silica shells with a tunable thickness were grown in situ, directly around a highly mono-disperse and stable oil-in-water emulsion system, stabilized by a double bio-functional polyelectrolyte heparin/chitosan layer. Such silica showed a complete degradation in a physiological medium (SBF) in a time frame of three days. Moreover, the outer silica shell was coated with polyethyleneglycol (PEG) in order to confer antifouling properties to the final nanocapsule. The outer silica layer combined its properties (it is an optimal bio-interface for bio-conjugations and for the embedding of hydrophilic drugs in the porous structure) with the capability to stabilize the oil core for the confinement of high payloads of lipophilic tracers (e.g., CdSe quantum dots, Nile Red) and drugs. In addition, polymer layers--besides conferring stability to the emulsion while building the silica shell--can be independently exploited if suitably functionalized, as demonstrated by conjugating chitosan with fluorescein isothiocyanate. Such numerous features in a single nanocarrier system make it very intriguing as a multifunctional platform for smart diagnosis and therapy.
Collapse
Affiliation(s)
- Raffaele Vecchione
- Istituto Italiano di Tecnologia, IIT@CRIB, Largo Barsanti e Matteucci, 53 80125 Napoli, Italy. and Centro di Ricerca Interdipartimentale sui Biomateriali CRIB, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| | - Giuseppina Luciani
- Centro di Ricerca Interdipartimentale sui Biomateriali CRIB, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy and Dipartimento di Ingegneria Chimica dei Materiali e della Produzione Industriale, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| | - Vincenzo Calcagno
- Istituto Italiano di Tecnologia, IIT@CRIB, Largo Barsanti e Matteucci, 53 80125 Napoli, Italy. and Centro di Ricerca Interdipartimentale sui Biomateriali CRIB, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| | - Anshuman Jakhmola
- Istituto Italiano di Tecnologia, IIT@CRIB, Largo Barsanti e Matteucci, 53 80125 Napoli, Italy.
| | - Brigida Silvestri
- Dipartimento di Ingegneria Chimica dei Materiali e della Produzione Industriale, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| | - Daniela Guarnieri
- Istituto Italiano di Tecnologia, IIT@CRIB, Largo Barsanti e Matteucci, 53 80125 Napoli, Italy. and Centro di Ricerca Interdipartimentale sui Biomateriali CRIB, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| | - Valentina Belli
- Istituto Italiano di Tecnologia, IIT@CRIB, Largo Barsanti e Matteucci, 53 80125 Napoli, Italy. and Centro di Ricerca Interdipartimentale sui Biomateriali CRIB, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| | - Aniello Costantini
- Centro di Ricerca Interdipartimentale sui Biomateriali CRIB, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy and Dipartimento di Ingegneria Chimica dei Materiali e della Produzione Industriale, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| | - Paolo A Netti
- Istituto Italiano di Tecnologia, IIT@CRIB, Largo Barsanti e Matteucci, 53 80125 Napoli, Italy. and Centro di Ricerca Interdipartimentale sui Biomateriali CRIB, Università di Napoli Federico II, Piazzale Tecchio, 80 80125 Napoli, Italy
| |
Collapse
|
5
|
El Hamzaoui H, Bouazaoui M, Capoen B. Raman investigation of germanium- and phosphorus-doping effects on the structure of sol–gel silica-based optical fiber preforms. J Mol Struct 2015. [DOI: 10.1016/j.molstruc.2015.06.061] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
6
|
Sun Q, Hu L, Zhou C, Zheng H, Yue Y. Correlation between supercooled liquid relaxation and glass Poisson’s ratio. J Chem Phys 2015; 143:164504. [DOI: 10.1063/1.4934228] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Qijing Sun
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China
| | - Lina Hu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China
| | - Chao Zhou
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China
| | - Haijiao Zheng
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China
| | - Yuanzheng Yue
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China
- Section of Chemistry, Aalborg University, DK-9000 Aalborg, Denmark
| |
Collapse
|
7
|
Abramczyk H, Brozek-Pluska B, Krzesniak M, Kopec M, Morawiec-Sztandera A. The cellular environment of cancerous human tissue. Interfacial and dangling water as a "hydration fingerprint". SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 129:609-623. [PMID: 24836126 DOI: 10.1016/j.saa.2014.03.103] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 03/17/2014] [Accepted: 03/22/2014] [Indexed: 06/03/2023]
Abstract
Despite a large number of publications, the role of water in the cellular environment of biological tissue has not been clarified. Characterizing the biological interface is a key challenge in understanding the interactions of water in the tissue. Although we often assume that the properties of the bulk water can be translated to the crowded biological environment, this approach must be considerably revised when considering the biological interface. To our knowledge, few studies have directly monitored the interactions and accumulation of water in the restricted environments of the biological tissue upon realistic crowding conditions. The present study focuses on a molecular picture of water molecules at the biological interface, or specifically, water molecules adjacent to the hydrophobic and hydrophilic surfaces of normal and cancerous tissues. We recorded and analyzed the IR and Raman spectra of the νs(OH) stretching modes of water at the biological interfaces of the human breast and neck tissues. The results revealed dramatic changes in the water content in the tissue and are potentially relevant to both the fundamental problems of interfacial water modeling and the molecular diagnostics of cancer as a 'hydration fingerprint'. Herein, we will discuss the origin of the vibrational substructures observed for the νs(OH) stretching modes of water, showing that the interfacial water interacting via H-bond with other water molecules and biomolecules at the biological surface and free OH vibration of the dangling water are sensitive indicators of the pathology between the normal (noncancerous) and cancerous tissue and cancer types.
Collapse
Affiliation(s)
- Halina Abramczyk
- Laboratory of Laser Molecular Spectroscopy, Institute of Applied Radiation Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland.
| | - Beata Brozek-Pluska
- Laboratory of Laser Molecular Spectroscopy, Institute of Applied Radiation Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland
| | - Marta Krzesniak
- Laboratory of Laser Molecular Spectroscopy, Institute of Applied Radiation Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland
| | - Monika Kopec
- Laboratory of Laser Molecular Spectroscopy, Institute of Applied Radiation Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland
| | - Alina Morawiec-Sztandera
- Department of Head and Neck Cancer, Medical University of Lodz, Kosciuszki 4, 90-419 Lodz, Poland
| |
Collapse
|
8
|
Saito M, D’Amico F, Bencivenga F, Cucini R, Gessini A, Principi E, Masciovecchio C. Spatial correlation between chemical and topological defects in vitreous silica: UV-resonance Raman study. J Chem Phys 2014; 140:244505. [DOI: 10.1063/1.4884155] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- M. Saito
- Elettra-Sincrotrone Trieste, S. S. 14 Km 163.5, I-34149 Trieste, Italy
| | - F. D’Amico
- Elettra-Sincrotrone Trieste, S. S. 14 Km 163.5, I-34149 Trieste, Italy
| | - F. Bencivenga
- Elettra-Sincrotrone Trieste, S. S. 14 Km 163.5, I-34149 Trieste, Italy
| | - R. Cucini
- Elettra-Sincrotrone Trieste, S. S. 14 Km 163.5, I-34149 Trieste, Italy
| | - A. Gessini
- Elettra-Sincrotrone Trieste, S. S. 14 Km 163.5, I-34149 Trieste, Italy
| | - E. Principi
- Elettra-Sincrotrone Trieste, S. S. 14 Km 163.5, I-34149 Trieste, Italy
| | - C. Masciovecchio
- Elettra-Sincrotrone Trieste, S. S. 14 Km 163.5, I-34149 Trieste, Italy
| |
Collapse
|
9
|
|
10
|
Raman spectra of high- κ dielectric layers investigated with micro-Raman spectroscopy comparison with silicon dioxide. ScientificWorldJournal 2013; 2013:208081. [PMID: 24072982 PMCID: PMC3773432 DOI: 10.1155/2013/208081] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 07/31/2013] [Indexed: 11/17/2022] Open
Abstract
Three samples with dielectric layers from high- κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high- κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the structure of this material. Raman spectra recorded for as-deposited hafnium oxide are similar to the results obtained for silicon dioxide layer. After thermal treatment especially at higher temperatures (600°C and above), the structure of hafnium oxide becomes similar to the bulk non-densified silicon dioxide.
Collapse
|
11
|
Protti S, Raulin K, Cristini O, Kinowski C, Turrell S, Mezzetti A. Wavelength shifting systems based on flavonols and their metal complexes encapsulated by post-doping in porous SiO2 xerogel matrices. J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2011.02.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
12
|
Haines J, Levelut C, Isambert A, Hébert P, Kohara S, Keen DA, Hammouda T, Andrault D. Topologically Ordered Amorphous Silica Obtained from the Collapsed Siliceous Zeolite, Silicalite-1-F: A Step toward “Perfect” Glasses. J Am Chem Soc 2009; 131:12333-8. [DOI: 10.1021/ja904054v] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Julien Haines
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| | - Claire Levelut
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| | - Aude Isambert
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| | - Philippe Hébert
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| | - Shinji Kohara
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| | - David A. Keen
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| | - Tahar Hammouda
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| | - Denis Andrault
- Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Université Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France, Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587 CNRS UM2, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France, CEA, DAM Le Ripault, F-37260 Monts, France, Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8) 1
| |
Collapse
|
13
|
Kalampounias AG, Yannopoulos SN, Papatheodorou GN. Temperature-induced structural changes in glassy, supercooled, and molten silica from 77 to 2150 K. J Chem Phys 2006; 124:14504. [PMID: 16409038 DOI: 10.1063/1.2136878] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In situ polarized and depolarized Raman spectra of glassy, supercooled, and molten SiO2 have been measured over the broad temperature range 77-2150 K in an effort to examine possible structural changes caused by temperature variation. A new experimental setup using a CO2 laser for heating the sample has been designed allowing measurement with controllable blackbody radiation background at temperatures up to 2200 K. Careful and systematic relative intensity measurements and the use of the isotropic and anisotropic Raman representation of the spectra revealed hidden bands in the bending mode region and resolved bands in the stretching region of the spectra. Overall the spectra behavior shows similarities with the spectra of the recently studied tetrahedral glasses/melts of ZnCl2 and ZnBr2. Increasing temperature causes subtle changes of the relative intensities within the silicon-oxygen stretching region at approximately 750-850 cm(-1) and gives rise to a new band at approximately 930 cm(-1). The spectral behavior is interpreted to indicate that the "SiO42" tetrahedra are bound to each other to form the network by apex-bridging and partly by edge-bridging oxygens. The network structure of the glass/melt is formed by mixing a variety of tetrahedra participating in "open" (cristobalitelike), "cluster" (supertetrahedra), and "chain" edge-bridged substructures bound to each other by bridging oxygens. A weak in intensity but strongly polarized composite band is resolved at approximately 1400 cm(-1) and is assigned to Si[Double Bond]O terminal bond frequency. Temperature rise increases the concentration of the terminal bonds by breaking up the network. These structural changes are reminiscent of the polyamorphic transformations occurring in silica as has recently been predicted by computer simulations. At low frequencies the Raman spectra reveal the presence of the Boson peak at approximately 60 cm(-1) which is well resolved even above melting temperature up to 2150 K.
Collapse
Affiliation(s)
- A G Kalampounias
- Department of Chemical Engineering, University of Patras, GR-26 504 Patras, Greece
| | | | | |
Collapse
|
14
|
Novikov VN, Ding Y, Sokolov AP. Correlation of fragility of supercooled liquids with elastic properties of glasses. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:061501. [PMID: 16089737 DOI: 10.1103/physreve.71.061501] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2004] [Indexed: 05/03/2023]
Abstract
We present a detailed analysis of correlations between fragility and other parameters of glass-forming systems. The analysis shows the importance of the ratio between the instantaneous bulk and shear modulus of glass-forming systems, or their Poisson ratio, for structural alpha relaxation and fast dynamics. In particular, for simple glass formers, the bulk to shear modulus ratio in the glassy state correlates with fragility in the liquid state and is inversely proportional to the intensity of the boson peak. A simple relationship between the temperature dependence of the viscosity of liquids at high temperatures and near the glass transition is used to rationalize these correlations. We argue that the ratio of the moduli controls the high-temperature activation energy of the structural relaxation and in this way affects the fragility. The ratio also defines the amplitude of the structural relaxation (i.e., the nonergodicity parameter) and the latter influences the strength of the boson peak. These observations might explain the puzzling correlation observed between the fragility and fast dynamics in glass-forming systems.
Collapse
Affiliation(s)
- V N Novikov
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909, USA
| | | | | |
Collapse
|
15
|
Müller-Buschbaum P. Influence of surface cleaning on dewetting of thin polystyrene films. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2003; 12:443-448. [PMID: 15007773 DOI: 10.1140/epje/e2004-00014-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Thin polystyrene (PS) films on top of silicon substrates are a frequently investigated model system in the framework of unstable films. However, with respect to stability the various experiments yielded contradictory results. Focussing on the influence of preparation conditions such as the surface cleaning solves these contradictions. By applying different surface cleans the PS film can be changed from a stable homogeneous one into a completely dewetted one. In addition to the type of clean applied, the time between cleaning the surface and spin-coating the polymeric layer on top turned out to be an important experimental parameter.
Collapse
Affiliation(s)
- P Müller-Buschbaum
- TU München, Phy.-Dept. E13, James-Franck-Str.1, 85748 Garching, Germany.
| |
Collapse
|
16
|
Scopigno T, Yannopoulos SN, Kastrissios DT, Monaco G, Pontecorvo E, Ruocco G, Sette F. High frequency acoustic modes in vitreous beryllium fluoride probed by inelastic x-ray scattering. J Chem Phys 2003. [DOI: 10.1063/1.1526097] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
17
|
Duverger C, Nedelec JM, Benatsou M, Bouazaoui M, Capoen B, Ferrari M, Turrell S. Waveguide Raman spectroscopy: a non-destructive tool for the characterization of amorphous thin films. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(98)00694-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
18
|
|
19
|
Sarnthein J, Pasquarello A, Car R. Origin of the High-Frequency Doublet in the Vibrational Spectrum of Vitreous SiO2. Science 1997; 275:1925-7. [PMID: 9072968 DOI: 10.1126/science.275.5308.1925] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The vibrational properties of amorphous SiO2 were studied within first-principles density functional theory. The calculated spectrum is in good agreement with neutron data, showing, in particular, a double peak in the high-frequency region. This doublet results from different local modes of the tetrahedral subunits and cannot be ascribed to a longitudinal-optic-transverse-optic (LO-TO) effect. This solves a long-standing controversy about the origin of the doublet in neutron spectra. A LO-TO splitting is recovered only when the long-wavelength limit is probed, as in optical experiments. These findings should be a general feature of tetrahedral AX2 amorphous networks.
Collapse
Affiliation(s)
- J Sarnthein
- J. Sarnthein, Institut Romand de Recherche Numerique en Physique des Materiaux (IRRMA), IN-Ecublens, CH-1015 Lausanne, Switzerland. A. Pasquarello and R. Car, IRRMA, IN-Ecublens, CH-1015 Lausanne, Switzerland, and Department of Condensed Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
| | | | | |
Collapse
|
20
|
Sugai S, Onodera A. Medium-Range Order in Permanently Densified SiO2 and GeO2 Glass. PHYSICAL REVIEW LETTERS 1996; 77:4210-4213. [PMID: 10062476 DOI: 10.1103/physrevlett.77.4210] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
21
|
|
22
|
Karpov VG, Grimsditch M. Pressure-induced transformations in glasses. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:6941-6948. [PMID: 10006862 DOI: 10.1103/physrevb.48.6941] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
23
|
Polian A, Grimsditch M. Sound velocities and refractive index of densified a-SiO2 to 25 GPa. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:13979-13982. [PMID: 10005734 DOI: 10.1103/physrevb.47.13979] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|