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Valencia Ramirez A, Bonneux G, Terfort A, Losada-Pérez P, Renner FU. Nanomechanical Stability of Laterally Heterogeneous Films of Corrosion Inhibitor Molecules Obtained by Microcontact Printing on Au Model Substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:15614-15621. [PMID: 36484233 DOI: 10.1021/acs.langmuir.2c02276] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Self-assembled monolayers of corrosion inhibitors of the mercaptobenzimidazole family, SH-BimH, SH-BimH-5NH2, and SH-BimH-5OMe, were formed on template-stripped ultraflat Au surfaces using microcontact printing, and subsequently analyzed using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and AFM-force spectroscopy (AFM-FS) using a quantitative imaging (QI) mode. Printing of all used inhibitor molecules resulted in clear patterns and in slightly more compact films compared to immersion. The stability of the monolayers is further probed by AFM-FS. Adhesion values of laterally heterogeneous inhibitor-modified surfaces compared to bare Au surfaces, nonpatterned areas, and fully covered surfaces are analyzed and discussed. Microcontact printing confers a superior nanomechanical stability to imidazole-modified films of the printed surface patches as compared to homogeneously covered surfaces by immersion into the inhibitor solution.
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Affiliation(s)
- Andrea Valencia Ramirez
- Institute for Materials Research, Hasselt University, Diepenbeek 3590, Belgium
- Division IMOMEC, IMEC vzw, Diepenbeek 3590, Belgium
| | - Gilles Bonneux
- Institute for Materials Research, Hasselt University, Diepenbeek 3590, Belgium
- Division IMOMEC, IMEC vzw, Diepenbeek 3590, Belgium
| | - Andreas Terfort
- Institute of Inorganic and Analytical Chemistry, Goethe-University, Frankfurt am Main 60438, Germany
| | - Patricia Losada-Pérez
- Experimental Soft Matter and Thermal Physics Laboratory, Université Libre de Bruxelles (ULB), Brussels 1050, Belgium
| | - Frank Uwe Renner
- Institute for Materials Research, Hasselt University, Diepenbeek 3590, Belgium
- Division IMOMEC, IMEC vzw, Diepenbeek 3590, Belgium
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Self-assembled monolayers of O-(2-Mercaptoethyl)-O′-methyl-hexa(ethylene glycol) (EG7-SAM) on gold electrodes. Effects of the nature of solution/electrolyte on formation and electron transfer blocking characteristics. J Electroanal Chem (Lausanne) 2022. [DOI: 10.1016/j.jelechem.2022.116303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Skoda MWA, Conzelmann NF, Fries MR, Reichart LF, Jacobs RMJ, Zhang F, Schreiber F. Switchable β-lactoglobulin (BLG) adsorption on protein resistant oligo (ethylene glycol) (OEG) self-assembled monolayers (SAMs). J Colloid Interface Sci 2022; 606:1673-1683. [PMID: 34534835 DOI: 10.1016/j.jcis.2021.08.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 07/07/2021] [Accepted: 08/03/2021] [Indexed: 12/16/2022]
Abstract
HYPOTHESIS Although protein adsorption at an interface is very common and important in biology and biotechnology, it is still not fully understood - mainly due to the intricate balance of forces that ultimately control it. In food processing (and medicine), controlling and manipulating protein adsorption, as well as avoiding protein adsorption (biofilm formation or membrane fouling) by the production of protein-resistant surfaces is of substantial interest. A major factor conferring resistance towards protein adsorption to a surface is the presence of tightly bound water molecules, as is the case in oligo ethylene glycol (OEG)-terminated self-assembled monolayers (SAMs). Due to strong attractive protein-protein and protein-surface interactions observed in systems containing trivalent salt ions, we hypothesize that these conditions may lead to a breakdown of protein resistance in OEG SAMs. EXPERIMENTS We studied the adsorption behavior of BLG in the presence of a lanthanum(III) chloride (LaCl3) at concentrations of 0, 0.1, 0.8 and 5.0 mM on normally protein resistant triethylene glycol-termianted (EG3) SAMs on a gold surface. We used quartz-crystal microbalance with dissipation (QCM-D) and neutron reflectivity (NR) to characterize the morphology of the interfacial region of the SAM. FINDINGS We demonstrate that the protein resistance of the EG3 SAM breaks down beyond a threshold salt concentration c∗ and mirrors the bulk behaviour of this system, showing reduced adsorption beyond a second critical salt concentration c∗∗. These results demonstrate for the first time the controlled switching of the protein-resistant properties of this type of SAM by the addition of trivalent salt.
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Affiliation(s)
- Maximilian W A Skoda
- STFC, ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, UK
| | - Nina F Conzelmann
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, Tübingen 72076, Germany
| | - Madeleine R Fries
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, Tübingen 72076, Germany
| | - Lara F Reichart
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, Tübingen 72076, Germany
| | - Robert M J Jacobs
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, South Parks Road, Oxford OX1 3TA, UK
| | - Fajun Zhang
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, Tübingen 72076, Germany
| | - Frank Schreiber
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, Tübingen 72076, Germany.
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Abstract
Interfaces between a liquid and a solid (L-S) are the most important surface science in chemistry, catalysis, energy, and even biology. Formation of an electric double layer (EDL) at the L-S interface has been attributed due to the adsorption of a layer of ions at the solid surface, which causes the ions in the liquid to redistribute. Although the existence of a layer of charges on a solid surface is always assumed, the origin of the charges is not extensively explored. Recent studies of contact electrification (CE) between a liquid and a solid suggest that electron transfer plays a dominant role at the initial stage for forming the charge layer at the L-S interface. Here, we review the recent works about electron transfer in liquid-solid CE, including scenerios such as liquid-insulator, liquid-semiconductor, and liquid-metal. Formation of the EDL is revisited considering the existence of electron transfer at the L-S interface. Furthermore, the triboelectric nanogenerator (TENG) technique based on the liquid-solid CE is introduced, which can be used not only for harvesting mechanical energy from a liquid but also as a probe for probing the charge transfer at liquid-solid interfaces.
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Affiliation(s)
- Shiquan Lin
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, P. R. China.,School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Xiangyu Chen
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, P. R. China.,School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhong Lin Wang
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, P. R. China.,School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
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Nie J, Ren Z, Xu L, Lin S, Zhan F, Chen X, Wang ZL. Probing Contact-Electrification-Induced Electron and Ion Transfers at a Liquid-Solid Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1905696. [PMID: 31782572 DOI: 10.1002/adma.201905696] [Citation(s) in RCA: 109] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 11/03/2019] [Indexed: 05/11/2023]
Abstract
As a well-known phenomenon, contact electrification (CE) has been studied for decades. Although recent studies have proven that CE between two solids is primarily due to electron transfer, the mechanism for CE between liquid and solid remains controversial. The CE process between different liquids and polytetrafluoroethylene (PTFE) film is systematically studied to clarify the electrification mechanism of the solid-liquid interface. The CE between deionized water and PTFE can produce a surface charges density in the scale of 1 nC cm-2 , which is ten times higher than the calculation based on the pure ion-transfer model. Hence, electron transfer is likely the dominating effect for this liquid-solid electrification process. Meanwhile, as ion concentration increases, the ion adsorption on the PTFE hinders electron transfer and results in the suppression of the transferred charge amount. Furthermore, there is an obvious charge transfer between oil and PTFE, which further confirms the presence of electron transfer between liquid and solid, simply because there are no ions in oil droplets. It is demonstrated that electron transfer plays the dominant role during CE between liquids and solids, which directly impacts the traditional understanding of the formation of an electric double layer (EDL) at a liquid-solid interface in physical chemistry.
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Affiliation(s)
- Jinhui Nie
- CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, P. R. China
- School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Zewei Ren
- CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, P. R. China
- School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Liang Xu
- CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, P. R. China
- School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Shiquan Lin
- CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, P. R. China
- School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Fei Zhan
- CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, P. R. China
- School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Xiangyu Chen
- CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, P. R. China
- School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Zhong Lin Wang
- CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, P. R. China
- School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0245, USA
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Electrochemistry Study of Permselectivity and Interfacial Electron Transfers of a Branch-Tailed Fluorosurfactant Self-Assembled Monolayer on Gold. Molecules 2018; 23:molecules23112998. [PMID: 30453539 PMCID: PMC6278534 DOI: 10.3390/molecules23112998] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 11/10/2018] [Accepted: 11/15/2018] [Indexed: 11/16/2022] Open
Abstract
We investigated the permselectivity and interfacial electron transfers of an amphiphilic branch-tailed fluorosurfactant self-assembled monolayer (FS-SAM) on a gold electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The FS-SAM was prepared by a self-assembly technique and a "click" reaction. The barrier property and interfacial electron transfers of the FS-SAM were also evaluated using various probes with different features. The FS-SAM allowed a higher degree of permeation by small hydrophilic (Cl- and F-) electrolyte ions than large hydrophobic (ClO₄- and PF₆-) ones. Meanwhile, the redox reaction of the Fe(CN)₆3- couple was nearly completely blocked by the FS-SAM, whereas the electron transfer of Ru(NH₃)₆3+ was easier than that of Fe(CN)₆3-, which may be due to the underlying tunneling mechanism. For hydrophobic dopamine, the hydrophobic bonding between the FS-SAM exterior fluoroalkyl moieties and the hydrophobic probes, as well as the hydration resistance from the interior hydration shell around the oligo (ethylene glycol) moieties, hindered the transport of hydrophobic probes into the FS-SAM. These results may have profound implications for understanding the permselectivity and electron transfers of amphiphilic surfaces consisting of molecules containing aromatic groups and branch-tailed fluorosurfactants in their structures.
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Chang R, Asatyas S, Lkhamsuren G, Hirohara M, Mondarte EAQ, Suthiwanich K, Sekine T, Hayashi T. Water near bioinert self-assembled monolayers. Polym J 2018. [DOI: 10.1038/s41428-018-0075-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Huang Q, Yoon I, Villanueva J, Kim K, Sirbuly DJ. Quantitative mechanical analysis of thin compressible polymer monolayers on oxide surfaces. SOFT MATTER 2014; 10:8001-8010. [PMID: 25157609 DOI: 10.1039/c4sm01530d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A clear understanding of the mechanical behavior of nanometer thick films on nanostructures, as well as developing versatile approaches to characterize their mechanical properties, are of great importance and may serve as the foundation for understanding and controlling molecular interactions at the interface of nanostructures. Here we report on the synthesis of thin, compressible polyethylene glycol (PEG) monolayers with a wet thickness of <20 nm on tin dioxide (SnO2) nanofibers through silane-based chemistries. Nanomechanical properties of such thin PEG films were extensively investigated using atomic force microscopy (AFM). In addition, tip-sample interactions were carefully studied, with different AFM tip modifications (i.e., hydrophilic and hydrophobic) and in different ionic solutions. We find that the steric forces dominate the tip-sample interactions when the polymer film is immersed in solution with salt concentrations similar to biological media (e.g., 1x phosphate buffer solution), while van der Waals and electrostatic forces have minimal contributions. A Dimitriadis thin film polymer compression model shows that the linear elastic regime is reproducible in the initial 50% indentation of these films which have tunable Young's moduli ranging from 5 MPa for the low molecular weight films to 700 kPa for the high molecular weight PEG films. Results are compared with the same PEG films deposited on silicon substrates which helped quantify the structural properties and understand the relationship between the structural and the mechanical properties of PEG films on the SnO2 fibers.
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Affiliation(s)
- Qian Huang
- Department of NanoEngineering, University of California, La Jolla, San Diego, CA 92093, USA.
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9
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Johnson PS, Goel M, Abbott NL, Himpsel FJ. Helical versus all-trans conformations of oligo(ethylene glycol)-terminated alkanethiol self-assembled monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:10263-10269. [PMID: 25133805 DOI: 10.1021/la500978s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The complex mixture of conformational states exhibited by oligo(ethylene glycol)-terminated alkanethiols on Ag and Au surfaces is explored by polarization-dependent X-ray absorption spectroscopy. Three self-assembled monolayers (SAMs) with known helical or all-trans conformations are used as references to characterize a SAM with unknown conformations. This case study is used as a prototype for developing a systematic framework to extract the conformations of SAMs from the polarization dependence of several orbitals. In the case at hand, these are associated with the C-H/Rydberg bonds of the alkane, the C-H/Rydberg bonds of ethylene glycol, and the C-C bonds of the backbone. The C-H/Rydberg orbitals of the alkane and ethylene glycol are distinguished via the chemical shift of the corresponding C 1s core levels.
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Affiliation(s)
- Phillip S Johnson
- Department of Physics, University of Wisconsin-Madison , 1150 University Avenue, Madison, Wisconsin 53706, United States
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11
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Hayashi T, Tanaka Y, Koide Y, Tanaka M, Hara M. Mechanism underlying bioinertness of self-assembled monolayers of oligo(ethyleneglycol)-terminated alkanethiols on gold: protein adsorption, platelet adhesion, and surface forces. Phys Chem Chem Phys 2012; 14:10196-206. [DOI: 10.1039/c2cp41236e] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Wang H, Tian H, Hao Z. Study of DDT and its derivatives DDD, DDE adsorption and degradation over Fe-SBA-15 at low temperature. J Environ Sci (China) 2012; 24:536-540. [PMID: 22655370 DOI: 10.1016/s1001-0742(11)60800-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Mesoporous SBA-15 with different Fe2O3 loading were synthesized by an in-situ coating progress for removals of dichlorodiphenyltrichloroethane (DDT) and its derivatives, i.e., 1,1-dichloro-2,2-bis-(p-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis-(4-chloro -phenyl) ethane (DDE). The results from XRD (X-ray diffractometer), TEM (transmission electron microscopy) indicated that the iron could be well dispersed on SBA-15 within 6 wt.% Fe2O3 loading. Nitrogen adsorption-desorption tests indicated that the synthesized materials were characterized by ordered meso-structure, high surface area and large pore volume. DDTs were removed from aqueous media in 12-hr treatment and high removal efficiency of DDTs was achieved at over 94%. DDTs could be completely degraded at 350 degrees C under the existence of SBA-15 with 4 wt.% Fe2O3 loading. The final degradation products of DDT were dichlorobenzophenone (DCB) and bis-(4-chloro-phenyl) methane (DDM), suggesting a complete dechlorination from trichloromethyl.
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Affiliation(s)
- Hailin Wang
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
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13
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Hurley CR, Ducker RE, Leggett GJ, Ratner BD. Fabrication of submicrometer biomolecular patterns by near-field exposure of plasma-polymerized tetraglyme films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10203-10209. [PMID: 20329717 DOI: 10.1021/la100362q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Plasma-polymerized tetraglyme films (PP4G) have been modified by exposure to ultraviolet (UV) light from a frequency-doubled argon ion laser (244 nm) and characterized using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS data indicated that the ether component of the C 1s spectrum declined after UV exposure, while components due to carbonyl and carboxylate groups increased. The film was physically eroded by UV exposure: after 100 s the rate of erosion reached a steady state of 0.05 nm s(-1). The coefficient of friction, measured by friction force microscopy (FFM), increased substantially following exposure to UV light, reaching a limiting value after 10 min exposure, in agreement with the time taken for the ether and carboxylate components in the C 1s spectrum to reach a limiting value. Samples exposed to UV light through a mask yielded excellent frictional contrast. When immersed in solutions of proteins and protein-functionalized nanoparticles labeled with fluorescent markers, selective adsorption occurred onto the exposed regions of these samples. Excellent fluorescence contrast was obtained when samples were characterized by confocal microscopy, indicating that the exposed areas become adhesive toward proteins, while the masked areas remain resistant to adsorption. Submicrometer structures have been formed by exposing PP4G films to UV light using a scanning near-field optical microscope coupled to a UV laser. Structures as small as 338 nm have been formed and used to immobilize proteins. Again, excellent contrast difference was observed when labeled proteins were adsorbed and characterized by confocal microscopy, suggesting a simple and effective route to the formation of submicrometer scale protein patterns.
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Affiliation(s)
- Claire R Hurley
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, UK
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Zimmermann R, Freudenberg U, Schweiß R, Küttner D, Werner C. Hydroxide and hydronium ion adsorption — A survey. Curr Opin Colloid Interface Sci 2010. [DOI: 10.1016/j.cocis.2010.01.002] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Bonnet N, O'Hagan D, Hähner G. Protein adsorption onto CF3-terminated oligo(ethylene glycol) containing self-assembled monolayers (SAMs): the influence of ionic strength and electrostatic forces. Phys Chem Chem Phys 2010; 12:4367-74. [DOI: 10.1039/b923065n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Behavior of Hydroxide Ions in Vicinity of Self-Assembled Monolayers of Alkanethiols on Metals. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2009. [DOI: 10.1380/ejssnt.2009.601] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Zhang F, Skoda MWA, Jacobs RMJ, Zorn S, Martin RA, Martin CM, Clark GF, Goerigk G, Schreiber F. Gold nanoparticles decorated with oligo(ethylene glycol) thiols: protein resistance and colloidal stability. J Phys Chem A 2007; 111:12229-37. [PMID: 17914772 DOI: 10.1021/jp074293v] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interactions between proteins and gold colloids functionalized with protein-resistant oligo(ethylene glycol) (OEG) thiol, HS(CH2)11(OCH2CH2)6OMe (EG6OMe), in aqueous solution have been studied by small-angle X-ray scattering (SAXS) and UV-vis spectroscopy. The mean size, 2R, and the size distribution of the decorated gold colloids have been characterized by SAXS. The monolayer-protected gold colloids have no correlations due to the low volume fraction in solution and are stable in a wide range of temperatures (5-70 degrees C), pH (1.3-12.4), and ionic strength (0-1.0 M). In contrast, protein (bovine serum albumin) solutions with concentrations in the range of 60-200 mg/mL (4.6-14.5 vol %) show a pronounced correlation peak in SAXS, which results from the repulsive electrostatic interaction between charged proteins. These protein interactions show significant dependence on ionic strength, as would be expected for an electrostatic interaction (Zhang et al. J. Phys. Chem. B 2007, 111, 251). For a mixture of proteins and gold colloids, the protein-protein interaction changes little upon mixing with OEG-decorated gold colloids. In contrast, the colloid-colloid interaction is found to be strongly dependent on the protein concentration and the size of the colloid itself. Adding protein to a colloidal solution results in an attractive depletion interaction between functionalized gold colloids, and above a critical protein concentration, c*, the colloids form aggregates and flocculate. Adding salt to such mixtures enhances the depletion effect and decreases the critical protein concentration. The aggregation is a reversible process (i.e., diluting the solution leads to dissolution of aggregates). The results also indicate that the charge of the OEG self-assembled monolayer at a curved interface has a rather limited effect on the colloidal stabilization and the repulsive interaction with proteins.
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Affiliation(s)
- Fajun Zhang
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany
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Bonnet N, O'Hagan D, Hähner G. Ionic strength mediated hydrophobic force switching of CF3-terminated ethylene glycol self-assembled monolayers (SAMs) on gold. Chem Commun (Camb) 2007:5066-8. [DOI: 10.1039/b712968h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Brandes N, Welzel PB, Werner C, Kroh LW. Adsorption-induced conformational changes of proteins onto ceramic particles: Differential scanning calorimetry and FTIR analysis. J Colloid Interface Sci 2006; 299:56-69. [PMID: 16500671 DOI: 10.1016/j.jcis.2006.01.065] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2005] [Revised: 01/31/2006] [Accepted: 01/31/2006] [Indexed: 10/25/2022]
Abstract
Three model proteins, bovine serum albumin, hen's egg lysozyme and bovine serum fibrinogen, were adsorbed from aqueous solution onto finely dispersed ceramic particles, namely different kinds of alumina and hydroxyapatite particles. The influence of adsorption on protein secondary structure was investigated. The FTIR spectroscopic findings were compared with the results of DSC measurements. In almost all cases it was found that adsorption results in destabilisation and structural loss of the bound protein. A decrease in transition enthalpy is correlated with a loss in alpha-helical structure, which seems to be the most sensitive structure on adsorption-induced rearrangements. A total collapse of structure in the adsorbed proteins was not determined on any ceramic surface. Some residual structure is always retained. Structural changes in the D- or E-domains of fibrinogen could be independently observed by two different calorimetric signals. The two techniques applied in the present study -- micro-DSC and FTIR spectroscopy -- can be concluded to provide complementary information on adsorption-induced structural changes on both the molecular (thermal stability, overall structure) and the sub-molecular level (secondary structure).
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Affiliation(s)
- Natascha Brandes
- Institute of Food Technology and Food Chemistry, Technical University Berlin, TIB 4/3-1, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany.
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Saalmink M, van der Marel C, Stapert HR, Burdinski D. Positive microcontact printing with mercaptoalkyloligo(ethylene glycol)s. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:1016-26. [PMID: 16430261 DOI: 10.1021/la052513v] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The soft lithographic replication of patterns with a low filling ratio by microcontact printing (microCP) is problematic due to the poor mechanical stability of common elastomeric stamps. A recently described strategy to avoid this problem employs a modified patterning method, positive microcontact printing ((+)microCP), in which a stamp with a mechanically more stable inverted relief pattern is used. In contrast to conventional negative microCP ((-)microCP), in the contact areas a self-assembled monolayer (SAM) is printed of a "positive ink", which provides only minor etch protection, whereas the noncontacted areas are subsequently covered with a different, etch-resistant SAM, prior to development by chemical etching. With the aim to identify novel, highly versatile positive inks, the patterning of gold by (+)microCP with mercaptoalkyloligo(ethylene glycol)s (MAOEGs), the subsequent adsorption of octadecanethiol (ODT), and the final development by wet chemical etching have now been studied. A polydisperse mixture of mercaptoundecylocta(ethylene glycol) derivatives was found to provide the best patterning results. The surface spreading of the positive ink during stamping, the exchange of printed MAOEGs with ODT, and the choice of the right etching bath were identified as key parameters that influence the achievable pattern resolution and contrast. Due to the modular composition of functionalized alkyloligo(ethylene glycol) derivatives, (+)microCP with these positive inks has the potential for easy adaptation to a variety of materials and development conditions.
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Affiliation(s)
- Milan Saalmink
- Philips Research, High Tech Campus Eindhoven, 5656 AE Eindhoven, The Netherlands
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21
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Abstract
The use of chemically modified atomic force microscopy (AFM) probes allows us to measure the surface charges of supported planar lipid bilayers with high sensitivity through the force spectroscopy operation mode. By controlling the chemistry of the tip, we can perform a classical analytical chemistry titration where the titration agent is a weak acid (attached to the AFM tip) with the particularity of being performed in surface rather than in solution and, especially, at the nanometric scale. Thus, the AFM tip acts as a real "nanosensor". The approaching curves of the force plots reveal that electrostatic interactions between the tip and the supported membrane play a key role. Besides, the plot of the adhesion force (measured from the retracting curve of the force plots) versus pH displays a nonsigmoidal shape with a peak in the adhesion force attributed to high-energy hydrogen bonds. One of these peaks corresponds to the pKa of the surface under study and the other to the pKa of the titrating probe attached to the tip.
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Affiliation(s)
- Sergi Garcia-Manyes
- Department of Physical Chemistry, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
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22
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Hoffmann C, Tovar GEM. Mixed self-assembled monolayers (SAMs) consisting of methoxy-tri(ethylene glycol)-terminated and alkyl-terminated dimethylchlorosilanes control the non-specific adsorption of proteins at oxidic surfaces. J Colloid Interface Sci 2005; 295:427-35. [PMID: 16256130 DOI: 10.1016/j.jcis.2005.10.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 08/31/2005] [Accepted: 10/03/2005] [Indexed: 11/21/2022]
Abstract
Monolayers from the newly synthesized compound methoxy-tri(ethylene glycol)-undecenyldimethylchlorosilane (CH3O(CH2CH2O)3(CH2)11Si(CH3)2Cl, MeO(EG)3C11DMS) and dodecyldimethylchlorosilane (DDMS), both pure and mixed, were prepared by self-assembly from organic solution in the presence of an organic base. The films obtained were characterized by advancing and receding contact angle measurements and ellipsometry to confirm the formation of self-assembled monolayers (SAMs). The resulting data on the covalently attached dimethylsilanes were compared to known oligo(ethylene glycol) (OEG)-terminated SAM systems based on terminal alkenes, thiolates or trihydrolyzable silanes. The composition of the mixed SAMs was found to depend directly and linearly on the composition of the silanization solution. Enhanced protein repellent properties were found for the SAMs using a variety of proteins, including the Ras Binding Domain (RBD), a protein with high relevance for cancer diagnostics. Roughly a RBD protein monolayer amount was adsorbed to silicon oxide surfaces silanized with DDMS or non-silanized silicon wafers, and in contrast, no RBD was adsorbed to surfaces silanized with MeO(EG)3C11DMS or to mixed monolayers consisting of DDMS and MeO(EG)3C11DMS if the content of OEG-silane overcame a critical content of X(EG) approximately 0.9.
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Affiliation(s)
- Christian Hoffmann
- Institute for Interfacial Engineering, University of Stuttgart, Nobelstr. 12, 70569 Stuttgart, Germany
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23
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Zimmermann R, Norde W, Cohen Stuart MA, Werner C. Electrokinetic characterization of poly(acrylic acid) and poly(ethylene oxide) brushes in aqueous electrolyte solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:5108-14. [PMID: 15896058 DOI: 10.1021/la050191p] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Surfaces carrying hydrophilic polymer brushes were prepared from poly(styrene)-poly(acrylic acid) and poly(styrene)-poly(ethylene oxide) diblock copolymers, respectively, using a Langmuir-Blodgett technique and employing poly(styrene)-coated planar glass as substrates. The electrical properties of these surfaces in aqueous electrolyte were analyzed as a function of pH and KCl concentration using streaming potential/streaming current measurements. From these data, both the zeta potential and the surface conductivity could be obtained. The poly(acrylic acid) brushes are charged due to the dissociation of carboxylic acid groups and give theoretical surface potentials of -160 mV at full dissociation in 10(-)(3) M solutions. The surface conductivity of these brushes is enormous under these conditions, accounting for more than 93% of the total measured surface conductivity. However, the mobility of the ions within the brush was estimated from the density of the carboxylic acid groups and the surface conductivity data to be only about 14% of that of free ions. The poly(ethylene oxide) (PEO) brushes effectively screen the charge of the underlying substrate, giving a very low zeta potential except when the ionic strength is very low. From the data, a hydrodynamic layer thickness of the PEO brushes could be estimated which is in good agreement with independent experiments (neutron reflectivity) and theoretical estimates. The surface conductivity in this system was slightly lower than that of the polystyren substrate. This also indicates that no significant amount of preferentially, i.e., nonelectrostatically attracted, ions taken up in the brush.
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Affiliation(s)
- Ralf Zimmermann
- Department Biocompatible Materials, Leibniz Institute of Polymer Research Dresden and The Max Bergmann Center of Biomaterials Dresden, Hohe Strasse 6, 01069 Dresden, Germany.
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24
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Kwon HC, Gewirth AA. AFM Force Measurements between SAM-Modified Tip and SAM-Modified Substrate in Alkaline Solution. J Phys Chem B 2005; 109:10213-22. [PMID: 16852238 DOI: 10.1021/jp044655o] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reversible desorption and adsorption of ethanethiol (ET) and hexadecane thiol (HDT) self-assembled monolayers (SAMs) on gold substrates are addressed with potential-dependent AFM force measurements where both tip and substrate potentials are controlled independently. For HDT-modified tip and substrate, the potential dependence of the force curve corresponds to the observed voltammetric features. The adhesion interaction between HDT-modified tip and substrate exhibits a large adhesion, whereas the adhesion is reduced to one-quarter of its original value after HDT on the substrate is removed. The presence of both attractive features on the approach curve and large adhesion on retraction after thiol desorption are ascribed to micelle formation from the desorbed, insoluble, thiols above the Au surface. For the ET-modified tip and substrate, the force curve evinces time-dependent recovery after the thiol adsorption peak which arises from the finite time of diffusion of the desorbed thiol back to the substrate. However, the force curves exhibit little potential dependence when the ET-desorbed tip is interacted with ET-modified substrate.
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Affiliation(s)
- Han-Cheol Kwon
- Department of Chemistry and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
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25
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Herrwerth S, Eck W, Reinhardt S, Grunze M. Factors that determine the protein resistance of oligoether self-assembled monolayers --internal hydrophilicity, terminal hydrophilicity, and lateral packing density. J Am Chem Soc 2003; 125:9359-66. [PMID: 12889964 DOI: 10.1021/ja034820y] [Citation(s) in RCA: 486] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein resistance of oligoether self-assembled monolayers (SAMs) on gold and silver surfaces has been investigated systematically to elucidate structural factors that determine whether a SAM will be able to resist protein adsorption. Oligo(ethylene glycol) (OEG)-, oligo(propylene glycol)-, and oligo(trimethylene glycol)-terminated alkanethiols with different chain lengths and alkyl termination were synthesized as monolayer constituents. The packing density and chemical composition of the SAMs were examined by XPS spectroscopy; the terminal hydrophilicity was characterized by contact angle measurements. IRRAS spectroscopy gave information about the chain conformation of specific monolayers; the amount of adsorbed protein as compared to alkanethiol monolayers was determined by ellipsometry. We found several factors that in combination or by themselves suppress the protein resistance of oligoether monolayers. Monolayers with a hydrophobic interior, such as those containing oligo(propylene glycol), show no protein resistance. The lateral compression of oligo(ethylene glycol) monolayers on silver generates more highly ordered monolayers and may cause decreased protein resistance, but does not necessarily lead to an all-trans chain conformation of the OEG moieties. Water contact angles higher than 70 degrees on gold or 65 degrees on silver reduce full protein resistance. We conclude that both internal and terminal hydrophilicity favor the protein resistance of an oligoether monolayer. It is suggested that the penetration of water molecules in the interior of the SAM is a necessary prerequisite for protein resistance. We discuss and summarize the various factors which are critical for the functionality of "inert" organic films.
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Affiliation(s)
- Sascha Herrwerth
- Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, D 69120 Heidelberg, Germany
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26
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Kreuzer HJ, Wang RLC, Grunze M. Hydroxide ion adsorption on self-assembled monolayers. J Am Chem Soc 2003; 125:8384-9. [PMID: 12837111 DOI: 10.1021/ja0350839] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It is argued, on the basis of density functional calculations, that a self-assembled monolayer of oligo(ethylene glycol) or n-alkanes in contact with water will preferentially adsorb hydroxyl ions (either from autoionization of water or added to the solution) on both methoxy- and hydroxide-terminated endgroups, thus charging the surface region of the SAM negatively with an estimated charge density of about 1 microC/cm(2) in agreement with recent experiments. The negative charging can explain long-ranged forces between opposing SAM surfaces. On dense SAMs, hydroxyl ions are highly mobile. Hydronium ions can absorb by penetration into the SAM provided there is enough lateral space for their encapsulation. The important role of hydration is demonstrated by calculating the excess binding energy of adsorption using a Born-Haber cycle.
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Affiliation(s)
- H Jürgen Kreuzer
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada.
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27
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Pertsin AJ, Hayashi T, Grunze M. Grand Canonical Monte Carlo Simulations of the Hydration Interaction between Oligo(ethylene glycol)-Terminated Alkanethiol Self-Assembled Monolayers. J Phys Chem B 2002. [DOI: 10.1021/jp025747l] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alexander J. Pertsin
- Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, D-69120 Heidelberg, Germany
| | - Tomohiro Hayashi
- Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, D-69120 Heidelberg, Germany
| | - Michael Grunze
- Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, D-69120 Heidelberg, Germany
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28
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Dicke C, Hähner G. pH-Dependent force spectroscopy of tri(ethylene glycol)- and methyl-terminated self-assembled monolayers adsorbed on gold. J Am Chem Soc 2002; 124:12619-25. [PMID: 12381208 DOI: 10.1021/ja027447n] [Citation(s) in RCA: 41] [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
Self-assembled monolayers (SAMs) of methoxy-tri(ethylene glycol)- (EG(3)-OMe) and methyl-terminated alkanethiols (C(16)) adsorbed on polycrystalline gold were investigated by chemical force spectroscopy. Measurements were performed in aqueous electrolyte solutions depending on ionic strength and pH value. Charged and hydrophobic tips were employed as probes to mimic local patches of proteins and to study the interaction at the organic/liquid interface in detail. Force-distance curves reveal information about the origin of the observed interaction and the underlying mechanisms. The measurements confirm an effective negative surface charge to be present at the oligo(ethylene glycol) (OEG) and the methyl interface and suggest that the charges are due to the adsorption of hydroxyl ions from aqueous solution. pH-dependent measurements further support the robustness of the established charge associated with the OEG films. Its sign does not change over the whole range of investigated values between pH approximately 3.5 and approximately 10. In contrast, the hydrophobic self-assembled hexadecanethiol films on gold show an isoelectric point (IEP) around pH 4. While the mechanism of charge establishment appears to be similar for both SA films, the strength of hydrogen bonding to interfacial water, which acts as a template for hydroxyl ion adsorption, is likely to be responsible for the observed difference.
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Affiliation(s)
- Christian Dicke
- School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9ST, UK
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