1
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Bellomo C, Lagostina V, Pavan C, Paganini MC, Turci F. Reaction with Water Vapor Defines Surface Reconstruction and Membranolytic Activity of Quartz Milled in Different Molecular Environments. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2308369. [PMID: 38102095 DOI: 10.1002/smll.202308369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 11/20/2023] [Indexed: 12/17/2023]
Abstract
Industrial processing of quartz (SiO2) and quartz-containing materials produces toxic dust. Fracturing quartz crystals opens the Si‒O bond and produces highly reactive surface species which mainly react with molecules like water and oxygen. This surface-reconstruction process forms silanol (Si‒OH) on the quartz surface, which can damage biological membranes under specific configurations. To comprehend the impact of the quartz surface restructuring on membranolytic activity, the formation and reactivity of quartz radicals produced in four distinct molecular environments with electron paramagnetic resonance (EPR) spectroscopy are evaluated and their membranolytic activity is measured through in vitro hemolysis test. The four molecular environments are formulated with and without molecular water vapor and oxygen (±H2O/±O2). The absence of water favored the formation of surface radical species. In water-rich environments, diamagnetic species prevailed due to radical recombination. Quartz milled in -H2O/±O2 acquired membranolytic activity when exposed to water vapor, unlike quartz milled in +H2O/±O2. After being stabilized by reaction with water vapor, the membranolytic activity of quartz is maintained over time. It is demonstrated that the type and the reactivity of radical sites on quartz are modulated by the outer molecular environment, ultimately determining the biological activity of milled quartz dust.
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Affiliation(s)
- Chiara Bellomo
- Department of Chemistry, Università degli Studi di Torino, Torino, 10125, Italy
- "G. Scansetti" Interdepartmental Center for Studies on Asbestos, Other Toxic Particulates, Università degli Studi di Torino, Torino, 10125, Italy
| | - Valeria Lagostina
- Department of Chemistry, Università degli Studi di Torino, Torino, 10125, Italy
| | - Cristina Pavan
- Department of Chemistry, Università degli Studi di Torino, Torino, 10125, Italy
- "G. Scansetti" Interdepartmental Center for Studies on Asbestos, Other Toxic Particulates, Università degli Studi di Torino, Torino, 10125, Italy
- Louvain Center for Toxicology, Applied Pharmacology, Université catholique de Louvain, Brussels, 1200, Belgium
| | - Maria Cristina Paganini
- Department of Chemistry, Università degli Studi di Torino, Torino, 10125, Italy
- NIS interdepartmental Center for Nanomaterials for Industry and Sustainability, Università degli Studi di Torino, Torino, 10125, Italy
| | - Francesco Turci
- Department of Chemistry, Università degli Studi di Torino, Torino, 10125, Italy
- "G. Scansetti" Interdepartmental Center for Studies on Asbestos, Other Toxic Particulates, Università degli Studi di Torino, Torino, 10125, Italy
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2
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Tian K, Li Z, Gosvami NN, Goldsby DL, Szlufarska I, Carpick RW. Memory Distance for Interfacial Chemical Bond-Induced Friction at the Nanoscale. ACS NANO 2019; 13:7425-7434. [PMID: 31180629 DOI: 10.1021/acsnano.8b09714] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Macroscale rate and state friction (RSF) laws include a memory distance, Dc, which is considered to be the distance required for a population of frictional contacts to renew itself via slip, counteracting the effects of aging in slow or static contact. This concept connects static friction and kinetic friction. Here, we use atomic force microscopy to study interfacial chemical bond-induced kinetic friction and the memory distance at the nanoscale for single silica-silica nanocontacts. We observe a logarithmic trend of decreasing friction with sliding velocity (i.e., velocity-weakening) at low velocities and a transition to increasing friction with velocity at higher velocities (i.e., velocity-strengthening). We propose a physically based kinetic model for the nanoscale memory effect, the "activation-passivation loop" model, which accounts for the activation and passivation of chemical reaction sites and the formation of new chemical bonds from dangling bonds during sliding. In the model, we define the memory distance to be the average sliding distance that accrues before an activated reaction site becomes passivated. Results from numerical simulations based on this model match experimental friction data well in the velocity-weakening regime and show that Dc is sensitive to the surface chemistry, and nearly independent of sliding velocity. The simulations also show values of Dc that are consistent with those obtained from the experiments. We propose a semiquantitative physical explanation of the observed logarithmic velocity-weakening behavior based on the conservation of the number of interfacial bonds during sliding. We also extract from the experimental data physically reasonable values of the energy barriers to the activation of reaction sites. Our results provide one possible physical mechanism for the nanoscale memory distance.
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Affiliation(s)
- Kaiwen Tian
- Department of Physics and Astronomy , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Zhuohan Li
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Nitya N Gosvami
- Department of Mechanical Engineering and Applied Mechanics , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - David L Goldsby
- Department of Earth and Environmental Sciences , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Izabela Szlufarska
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Robert W Carpick
- Department of Mechanical Engineering and Applied Mechanics , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
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3
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Assaf SM, Subhi Khanfar M, Bassam Farhan A, Said Rashid I, Badwan AA. Preparation and characterization of co-processed starch/MCC/chitin hydrophilic polymers onto magnesium silicate. Pharm Dev Technol 2019; 24:761-774. [PMID: 30888873 DOI: 10.1080/10837450.2019.1596131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
It was aimed to investigate the compressibility, compactibility, powder flow and tablet disintegration of a new excipient comprising magnesium (Mg) silicate co-processed (5%-85% w/w) onto chitin, microcrystalline cellulose (MCC) and starch as the hydrophilic polymers of interest. Initially, the mechanism of tablet disintegration was studied by measuring water infiltration rate, moisture sorption, swelling capacity and hydration ability. Moreover, the powders compression behavior was carried out by applying Kawakita model of compression analysis in addition to porosity and radial tensile strength measurements. In vitro drug release of compacts made of 400 mg ibuprofen and 300 mg of the hydrophilic polymers containing 30% w/w Mg silicate co-precipitate was investigated in phosphate buffer (pH 7.8). This work demonstrated that the incorporation of Mg silicate to the hydrophilic polymers lead to the improvement of powder flowability, compactibility, stability (with regard to storage conditions), compacts crushing strength, and disintegration time in addition to faster drug release. The overall findings are practically advantageous in the context of finding a low cost and multifunctional co-processed excipient of natural origins.
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Affiliation(s)
- Shereen M Assaf
- a Department of Pharmaceutical Technology, Faculty of Pharmacy , Jordan University of Science and Technology , Irbid , Jordan
| | - Mai Subhi Khanfar
- a Department of Pharmaceutical Technology, Faculty of Pharmacy , Jordan University of Science and Technology , Irbid , Jordan
| | - Ahmed Bassam Farhan
- a Department of Pharmaceutical Technology, Faculty of Pharmacy , Jordan University of Science and Technology , Irbid , Jordan
| | - Iyad Said Rashid
- b Jordanian Pharmaceutical Manufacturing Company , Amman , Jordan
| | - Adnan Ali Badwan
- b Jordanian Pharmaceutical Manufacturing Company , Amman , Jordan
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4
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Sarkar A, Das J, Ghosh P. p-TsOH-Catalyzed one-pot transformation of di- and trihydroxy steroids towards diverse A/B-ring oxo-functionalization. NEW J CHEM 2017. [DOI: 10.1039/c7nj01878a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A milder, facile, and greener transformative protocol, specifically on solid supports, to yield A-ring and/or B-ring oxo-functionalized steroids has been accomplished.
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Affiliation(s)
- Antara Sarkar
- Natural Products and Polymer Chemistry Laboratory
- Department of Chemistry
- North Bengal University
- Darjeeling-734013
- India
| | - Jayanta Das
- Natural Products and Polymer Chemistry Laboratory
- Department of Chemistry
- North Bengal University
- Darjeeling-734013
- India
| | - Pranab Ghosh
- Natural Products and Polymer Chemistry Laboratory
- Department of Chemistry
- North Bengal University
- Darjeeling-734013
- India
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5
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Atia AA, El-Nahas AM, Marie AM, Mahdy LDA. Adsorption of Oleic Acid on Silica Gel Derived from Rice Ash Hulls: Experimental and Theoretical Studies. ADSORPT SCI TECHNOL 2016. [DOI: 10.1260/026361706781388978] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Affiliation(s)
- Asem A. Atia
- Chemistry Department, Faculty of Science, El-Menoufia University, Shebin El-Kom, Egypt
| | - Ahmed M. El-Nahas
- Chemistry Department, Faculty of Science, El-Menoufia University, Shebin El-Kom, Egypt
| | - Asmaa M. Marie
- Food Technology Research Institute, Agricultural Research Center, Cairo, Egypt
| | - Laila D. Al Mahdy
- Food Technology Research Institute, Agricultural Research Center, Cairo, Egypt
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6
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Zhao Z, Sun X, Dong Y. Synergistic Effect of Doped Functionalized Ionic Liquids in Silica Hybrid Material for Rare Earth Adsorption. Ind Eng Chem Res 2016. [DOI: 10.1021/acs.iecr.5b04742] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zeyuan Zhao
- Xiamen Institute of Rare
Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, China
| | - Xiaoqi Sun
- Xiamen Institute of Rare
Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, China
| | - Yamin Dong
- Xiamen Institute of Rare
Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, China
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7
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Hadi P, Ning C, Kubicki JD, Mueller K, Fagan JW, Luo Z, Weng L, McKay G. Sustainable development of a surface-functionalized mesoporous aluminosilicate with ultra-high ion exchange efficiency. Inorg Chem Front 2016. [DOI: 10.1039/c5qi00182j] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The present work employs a facile hydroxylation technique to efficiently functionalize the surface of a waste-derived aluminosilicate for ultra-high heavy metal uptakeviaion exchange.
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Affiliation(s)
- Pejman Hadi
- Chemical and Biomolecular Engineering Department
- Hong Kong University of Science and Technology
- Kowloon
- China
| | - Chao Ning
- Chemical and Biomolecular Engineering Department
- Hong Kong University of Science and Technology
- Kowloon
- China
| | - James D. Kubicki
- Department of Geological Sciences
- University of Texas at El Paso
- El Paso
- USA
| | - Karl Mueller
- Department of Chemistry
- The Pennsylvania State University
- University Park
- USA
- Physical and Computational Sciences Directorate
| | - Jonathan W. Fagan
- Department of Chemistry
- The Pennsylvania State University
- University Park
- USA
| | - Zhengtang Luo
- Chemical and Biomolecular Engineering Department
- Hong Kong University of Science and Technology
- Kowloon
- China
| | - Lutao Weng
- Chemical and Biomolecular Engineering Department
- Hong Kong University of Science and Technology
- Kowloon
- China
- Materials Characterization and Preparation Facility
| | - Gordon McKay
- Chemical and Biomolecular Engineering Department
- Hong Kong University of Science and Technology
- Kowloon
- China
- Division of Sustainable Development
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8
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Jin T, Kong FM. Effect of differently terminal groups of poly(amido-amine) dendrimers on dispersion stability of nano-silica and ab initio calculations. SURF INTERFACE ANAL 2015. [DOI: 10.1002/sia.5735] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Tao Jin
- College of Material Science and Engineering; Shandong University of Science and Technology; Qingdao 266590 China
| | - Fan-mei Kong
- College of Earth Science and Engineering; Shandong University of Science and Technology; Qingdao 266590 China
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9
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Khachatryan L, McFerrin C, Hall R, Dellinger B. Environmentally persistent free radicals (EPFRs). 3. Free versus bound hydroxyl radicals in EPFR aqueous solutions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:9220-6. [PMID: 25036238 PMCID: PMC4140529 DOI: 10.1021/es501158r] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 07/08/2014] [Accepted: 07/18/2014] [Indexed: 05/19/2023]
Abstract
Additional experimental evidence is presented for in vitro generation of hydroxyl radicals because of redox cycling of environmentally persistent free radicals (EPFRs) produced after adsorption of 2-monochlorophenol at 230 °C (2-MCP-230) on copper oxide supported by silica, 5% Cu(II)O/silica (3.9% Cu). A chemical spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed. Experiments in spiked O(17) water have shown that ∼15% of hydroxyl radicals formed as a result of redox cycling. This amount of hydroxyl radicals arises from an exogenous Fenton reaction and may stay either partially trapped on the surface of particulate matter (physisorbed or chemisorbed) or transferred into solution as free OH. Computational work confirms the highly stable nature of the DMPO-OH adduct, as an intermediate produced by interaction of DMPO with physisorbed/chemisorbed OH (at the interface of solid catalyst/solution). All reaction pathways have been supported by ab initio calculations.
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Affiliation(s)
- Lavrent Khachatryan
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Telephone: 225-578-4417. E-mail:
| | - Cheri
A. McFerrin
- Department
of Natural Sciences and Mathematics, Dominican
University of California, San Rafael, California 94901, United States
| | - Randall
W. Hall
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Department
of Natural Sciences and Mathematics, Dominican
University of California, San Rafael, California 94901, United States
| | - Barry Dellinger
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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10
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Zarubin DP. Compositional effects on Si–OH bond length in hydrous silicates with implications for trends in the SiOH acidity. J SOLID STATE CHEM 2014. [DOI: 10.1016/j.jssc.2014.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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11
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Rimola A, Costa D, Sodupe M, Lambert JF, Ugliengo P. Silica surface features and their role in the adsorption of biomolecules: computational modeling and experiments. Chem Rev 2013; 113:4216-313. [PMID: 23289428 DOI: 10.1021/cr3003054] [Citation(s) in RCA: 328] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Albert Rimola
- Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra (Cerdanyola del Vallès), Spain
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12
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Jin T, Lü H. Ab initioStudy of Complexation Process between Poly(amido‐amine) and Nano‐Silicon Dioxide. CHINESE J CHEM PHYS 2013. [DOI: 10.1063/1674-0068/26/03/277-286] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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13
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Futamura R, Jorge M, Gomes JRB. Structures and energetics of organosilanes in the gaseous phase: a computational study. Theor Chem Acc 2013. [DOI: 10.1007/s00214-012-1323-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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14
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Leroch S, Wendland M. Simulation of Forces between Humid Amorphous Silica Surfaces: A Comparison of Empirical Atomistic Force Fields. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2012; 116:26247-26261. [PMID: 23378869 PMCID: PMC3558025 DOI: 10.1021/jp302428b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 11/06/2012] [Indexed: 05/28/2023]
Abstract
Atmospheric humidity strongly influences the interactions between dry granular particles in process containers. To reduce the energy loss in industrial production processes caused by particle agglomeration, a basic understanding of the dependence of particle interactions on humidity is necessary. Hence, in this study, molecular dynamic simulations were carried out to calculate the adhesion between silica surfaces in the presence of adsorbed water. For a realistic description, the choice of force field is crucial. Because of their frequent use and transferability to biochemical systems, the Clay and CWCA force fields were investigated with respect to their ability to describe the water-silica interface in comparison to the more advanced Reax force field, ab initio calculations, and experiments.
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15
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Jin T, Li XY. Interaction Mechanism of Nano-silicon Dioxide Modified by Poly(amidoamine) Dendrimers. CHINESE J CHEM PHYS 2012. [DOI: 10.1088/1674-0068/25/05/592-604] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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16
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Bakk IP, Deme I, Szieberth D, Nyulászi L. Molecular level investigation of the dynamic structure model in molten and solid alkali glasses. Struct Chem 2012. [DOI: 10.1007/s11224-012-9969-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Grillo ME, Coll DS, Rodríguez J. Effect of the environment on the hydroxyl density of α-quartz (111). Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2011.11.084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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18
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Differentiating and characterizing geminal silanols in silicas by 29Si NMR spectroscopy. J Colloid Interface Sci 2010; 352:163-70. [DOI: 10.1016/j.jcis.2010.08.045] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 08/12/2010] [Accepted: 08/17/2010] [Indexed: 11/19/2022]
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19
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Murray DK. The characterization of phospholipid functional group probe species on respirable silicon-containing dusts by solid-state 13C and 31P nuclear magnetic resonance spectroscopy. APPLIED SPECTROSCOPY 2010; 64:328-336. [PMID: 20223070 DOI: 10.1366/000370210790918427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Solid-state nuclear magnetic resonance (NMR) spectroscopic studies are reported for the interactions of probe molecules with respirable silicon-containing dusts as experimental evidence complementing computational studies reported by Snyder and Madura recently in J. Phys. Chem. B 112, 7095 (2008). The selected probe molecules represent the individual functional groups of a model lung surfactant dipalmitoylphosphatidyl choline (DPPC) deposited on a respirable silica and kaolin from water solution. (13)C and (31)P solid-state NMR spectroscopies were employed to detect chemical shift, line width, and chemical shift anisotropy, providing experimental evidence of mobility and relaxation changes describing the site and orientation of surface-associated species. NMR results confirm that only the phosphate and adjacent carbons are immobilized by surface hydroxyls on kaolin, while these and the carbons of the cationic head group are likewise immobilized by surface silanols on Miu-U-Sil 5. The phosphates in phosphoryl- and phosphatidyl-cholines were the primary interaction sites, with additional weak coordination with the trimethylammonium cation species. Covalent Al-O-P formation is not likely a factor in in vivo or in vitro toxicity mechanisms of respirable silicon-containing materials, but is rather the result of dehydration or demethoxylation reactions occurring over time or during heating or reduced pressure used in preparing materials for NMR spectroscopic study. Hydration is a critical factor in the formation and preparation for spectroscopic observation of coated dusts. Care must be taken to ensure that products formed and studied correspond to species formed in vivo under suitable concentration and hydration conditions.
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Affiliation(s)
- David K Murray
- National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Road, MS/3030, Morgantown, West Virginia 26505, USA.
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20
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Costa D, Tougerti A, Tielens F, Gervais C, Stievano L, Lambert JF. DFT study of the adsorption of microsolvated glycine on a hydrophilic amorphous silica surface. Phys Chem Chem Phys 2008; 10:6360-8. [DOI: 10.1039/b806501b] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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21
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Narayanasamy J, Kubicki JD. Mechanism of hydroxyl radical generation from a silica surface: molecular orbital calculations. J Phys Chem B 2007; 109:21796-807. [PMID: 16853831 DOI: 10.1021/jp0543025] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The interaction of an H(2)O molecule with cluster models of fractured silica surfaces was studied by means of quantum mechanical calculations. Two clusters representing homolytic cleavage (triple bond Si(*) and triple bond SiO(*)) and two representing heterolytic cleavage (triple bond Si(+) and triple bond Si-O(-)) of silica surfaces were modeled. Vibrational frequencies of the reactants and products of these silica surfaces reacting with H(2)O have been calculated and compare favorably with experiment. Comparisons of the Gibbs free and potential energies for the model ionic and radical states were made, and the radical pair of sites was predicted to be more stable by approximately -70 to -85 kJ/mol, depending on the computational methodology. These calculations suggest that when silica is fractured in a vacuum homolytic cleavage is favored. Reaction pathways were investigated for these four model surface sites interacting with H(2)O. The reaction of H(2)O with triple bond SiO(*) was predicted to generate OH(*). Rate constants for these reactions were also calculated and predict a rapid equibrium for the reaction triple bond SiO(*) + H(2)O --> triple bond SiOH + OH(*). Stability of a finite number of triple bond SiO(*) sites at equilibrium in the above reaction with H(2)O was also predicted, which implies a long-term ability of silica surfaces to produce OH(*) radicals if the sites of the broken bonds do not repolymerize to form siloxane groups.
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Affiliation(s)
- Jayakumar Narayanasamy
- Department of Geosciences and the Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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22
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Murashov VV, Demchuk E. A comparative study of unrelaxed surfaces on quartz and kaolinite, using the periodic density functional theory. J Phys Chem B 2007; 109:10835-41. [PMID: 16852318 DOI: 10.1021/jp050113a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To investigate surface properties of fractured silica particles, which are commonly connected to the etiology of silica toxicity, models of low-index unrelaxed surfaces of quartz and kaolinite were constructed and analyzed using the periodic density functional theory calculations. The models were used to investigate surface sites that emerge in the processes of heterolytic and homolytic cleavage of quartz. It is found that the quartz surface is stabilized by two types of interactions. One, due to a more even charge distribution of sites, was characterized by surface energies of up to 0.025 eV x A(-2) and the other, due to a more even oxygen distribution between complementary surfaces, was up to 0.036 eV x A(-2). The total specific surface energies of unrelaxed surfaces ranged from 0.161 to 0.200 eV x A(-2) for quartz and from 0.017 to 0.158 eV x A(-2) for kaolinite. For the conchoidal fracture of quartz an average specific surface energy of 0.187 eV x A(-2) was obtained. These results provide a foundation for further characterization of the surface properties of mechanically comminuted respirable silica particulate and for reduction of occupational health hazards due to pulverized silica.
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Affiliation(s)
- Vladimir V Murashov
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, West Virginia 26505, USA.
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23
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McNamee CE, Yamamoto S, Higashitani K. Preparation and characterization of pure and mixed monolayers of poly(ethylene glycol) brushes chemically adsorbed to silica surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:4389-99. [PMID: 17367176 DOI: 10.1021/la063512l] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We prepared pure and mixed monolayers of methoxy-terminated poly(ethylene glycol)s (m-PEG's) chemically attached to silica surfaces by using m-PEG silane coupling agents of three different molecular weights. These films were subsequently characterized in water by atomic force microscopy (AFM). Images of pure m-PEG monolayers showed the formation of polymer brushes on silica. Force curves between two modified surfaces suggested that an increase in the number of oxyethylene (OE) groups from 6 (PEG6 surface) to 43 (PEG43 surface) to 113 (PEG113 surface) decreased the flexibility of the m-PEG chains in the m-PEG brushes. Frictional force measurements also showed that the friction increased in the order PEG6 < PEG43 <PEG113. Because PEG113 had a molecular weight that was greater than the critical molecular weight for entanglement in a PEG melt and displayed the least stretching of its chain, a chain in the PEG113 brush was thought to participate in entanglements or interchain hydrogen bonding. Mixed monolayers of PEG6 and PEG113 were prepared using various fractions of PEG6 and PEG113. Images of mixed PEG6 and PEG113 monolayers showed that the size of the PEG113 islands in the film decreased as the fraction of PEG113 decreased. The force curves between two modified surfaces suggested that the flexibility of the mixed monolayers decreased as the fraction of PEG113 increased. Frictional force measurements also showed that the friction decreased as the fraction of PEG6 in the PEG6-PEG113 mixed film increased. Entanglements were therefore thought to decrease as the fraction of PEG113 in the mixed monolayer decreased.
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Affiliation(s)
- Cathy E McNamee
- Department of Chemical Engineering, Kyoto University-Katsura, Nishikyo-ku, Kyoto, Kyoto 615-8510, Japan.
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Zhang Y, Li ZH, Truhlar DG. Computational Requirements for Simulating the Structures and Proton Activity of Silicaceous Materials. J Chem Theory Comput 2007; 3:593-604. [DOI: 10.1021/ct6002884] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yuan Zhang
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431
| | - Zhen Hua Li
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431
| | - Donald G. Truhlar
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431
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Carteret C. Vibrational properties of silanol group: from alkylsilanol to small silica cluster. Effects of silicon substituents. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2006; 64:670-80. [PMID: 16677854 DOI: 10.1016/j.saa.2005.08.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 07/26/2005] [Accepted: 08/02/2005] [Indexed: 05/09/2023]
Abstract
Structural and vibrational features of silanol group are investigated in detail by quantum calculations and normal mode analysis. The structural parameters, charge distributions, force fields, vibrational wavenumbers, potential energy distributions of normal modes and derivatives of the electric dipole moment are analyzed in relation to the nature of the substituents adjacent to the silanol group. The calculations results are discussed in light of available experimental data. Although the OH stretching mode has already been well localized in various silanols, both the Si-(OH) stretching and SiOH bending vibrations have not been yet finely analyzed leading to some discrepancies reported in literature. Clarified assignments of these vibrations are proposed on the basis of normal mode analysis and of SiOH-->SiOD isotopic exchange. The following spectral ranges are determined: 790-1030 cm-1 for nuSi-(OH), 790-1010 cm-1 for nuSi-(OD), 790-900 cm-1 for deltaOH and 580-640 cm-1 for deltaOD. The nuSi-(OH)/nuSi-(OD) wavenumbers are highly dependent on silicon substituents: electron-withdrawing groups induce shifts to higher wavenumbers while electron-releasing groups induce shifts to lower wavenumbers. In alkylsilanols, the SiOH bending is observed at higher wavenumber than the stretching vibration. Analysis of infrared intensities and dipole derivatives in internal coordinates gives explanations to spectral "anomalies" observed in experimental measurements such as well defined and intense nuSi-(OD) absorption in contrast with very low intensity for nuSi-(OH). Numerous empirical correlations are established allowing reconstruction of both SiOH force field and SiOH structural parameters with knowledge of few experimental data.
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Affiliation(s)
- Cédric Carteret
- Laboratoire de Chimie Physique pour l'Environnement, Equipe Chimie et Spectrochimie des Interfaces, UMR 7564 CNRS-Université Henri Poincaré, 405 rue de Vandoeuvre, 54600 Villers-lès-Nancy, France.
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Sahai N, Rosso K. Computational Molecular Basis for Improved Silica Surface Complexation Models. INTERFACE SCIENCE AND TECHNOLOGY 2006. [DOI: 10.1016/s1573-4285(06)80057-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Tero R, Watanabe H, Urisu T. Supported phospholipid bilayer formation on hydrophilicity-controlled silicon dioxide surfaces. Phys Chem Chem Phys 2006; 8:3885-94. [DOI: 10.1039/b606052h] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Reconstruction of the most common pristine and hydrolyzed surfaces of quartz was investigated with periodic density functional theory calculations. Surface energies of reconstructed pristine faces, pertinent to quartz growth morphologies in melts, are found to range from 0.071 eV/A2 for the (101) surface to 0.139 eV/A2 for the (001) surface, and they increase as (101) < (102) < (112) < [(100), (111)] < (110) < (001). Four types of reconstruction reactions are observed: (1) formation of two-membered rings from vicinal silyl and siloxy sites, (2) formation of a pair of tricoordinated/unicoordinated oxygen atoms, (3) formation of three-membered rings, and (4) transformation of silanone sites into siloxane sites. The main features of reconstructed pristine quartz surfaces are two-membered rings formed from bridged siloxy and silyl sites on all investigated surfaces, a stable site complex with geminal positively charged tricoordinated and negatively charged unicoordinated oxygen atoms revealed on the (112) surface, and charged nonbridged siloxy/silyl sites, which are more stable than radical siloxy/silyl sites. Hydrolyzed surface energies range from -0.010 eV/A2 for the (001) surface to 0.002 eV/A2 for the (101) surface and increase as (001) < (110) < (102) < (111) < (100) < (112) < (101). The hydrolyzed surface stability is found to depend strongly on inter-site silanol hydrogen bonding. Observed networks of hydrogen bonds are important for interactions between silica surfaces and biomolecules in an aqueous environment.
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Affiliation(s)
- Vladimir V Murashov
- National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA.
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