1
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Tan CD, Hähner G, Fitzer S, Cole C, Finch AA, Hintz C, Hintz K, Allison N. The response of coral skeletal nano structure and hardness to ocean acidification conditions. R Soc Open Sci 2023; 10:230248. [PMID: 37538739 PMCID: PMC10394408 DOI: 10.1098/rsos.230248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 07/12/2023] [Indexed: 08/05/2023]
Abstract
Ocean acidification typically reduces coral calcification rates and can fundamentally alter skeletal morphology. We use atomic force microscopy (AFM) and microindentation to determine how seawater pCO2 affects skeletal structure and Vickers hardness in a Porites lutea coral. At 400 µatm, the skeletal fasciculi are composed of tightly packed bundles of acicular crystals composed of quadrilateral nanograins, approximately 80-300 nm in dimensions. We interpret high adhesion at the nanograin edges as an organic coating. At 750 µatm the crystals are less regular in width and orientation and composed of either smaller/more rounded nanograins than observed at 400 µatm or of larger areas with little variation in adhesion. Coral aragonite may form via ion-by-ion attachment to the existing skeleton or via conversion of amorphous calcium carbonate precursors. Changes in nanoparticle morphology could reflect variations in the sizes of nanoparticles produced by each crystallization pathway or in the contributions of each pathway to biomineralization. We observe no significant variation in Vickers hardness between skeletons cultured at different seawater pCO2. Either the nanograin size does not affect skeletal hardness or the effect is offset by other changes in the skeleton, e.g. increases in skeletal organic material as reported in previous studies.
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Affiliation(s)
- Chao Dun Tan
- EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews KY16 9TS, UK
| | - Georg Hähner
- EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews KY16 9TS, UK
| | - Susan Fitzer
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
| | - Catherine Cole
- School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews KY16 9TS, UK
| | - Adrian A. Finch
- School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews KY16 9TS, UK
| | - Chris Hintz
- Department of Marine and Environmental Sciences, Savannah State University, Savannah, GA USA
| | - Ken Hintz
- Department of Electrical and Computer Engineering, George Mason University, Fairfax, VA, USA
| | - Nicola Allison
- School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews KY16 9TS, UK
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2
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Makou E, Bailey RG, Johnston H, Parkin JD, Hulme AN, Hähner G, Barlow PN. Combining SPR with atomic-force microscopy enables single-molecule insights into activation and suppression of the complement cascade. J Biol Chem 2019; 294:20148-20163. [PMID: 31719147 PMCID: PMC6937562 DOI: 10.1074/jbc.ra119.010913] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 11/07/2019] [Indexed: 12/05/2022] Open
Abstract
Activation and suppression of the complement system compete on every serum-exposed surface, host or foreign. Potentially harmful outcomes of this competition depend on surface molecules through mechanisms that remain incompletely understood. Combining surface plasmon resonance (SPR) with atomic force microscopy (AFM), here we studied two complement system proteins at the single-molecule level: C3b, the proteolytically activated form of C3, and factor H (FH), the surface-sensing C3b-binding complement regulator. We used SPR to monitor complement initiation occurring through a positive-feedback loop wherein surface-deposited C3b participates in convertases that cleave C3, thereby depositing more C3b. Over multiple cycles of flowing factor B, factor D, and C3 over the SPR chip, we amplified C3b from ∼20 to ∼220 molecules·μm−2. AFM revealed C3b clusters of up to 20 molecules and solitary C3b molecules deposited up to 200 nm away from the clusters. A force of 0.17 ± 0.02 nanonewtons was needed to pull a single FH molecule, anchored to the AFM probe, from its complex with surface-attached C3b. The extent to which FH molecules stretched before detachment varied widely among complexes. Performing force-distance measurements with FH(D1119G), a variant lacking one of the C3b-binding sites and causing atypical hemolytic uremic syndrome, we found that it detached more uniformly and easily. In further SPR experiments, KD values between FH and C3b on a custom-made chip surface were 5-fold tighter than on commercial chips and similar to those on erythrocytes. These results suggest that the chemistry at the surface on which FH acts drives conformational adjustments that are functionally critical.
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Affiliation(s)
- Elisavet Makou
- EaStChem School of Chemistry, University of Edinburgh, Joseph Black Chemistry Building, Edinburgh, Scotland EH9 3FJ, United Kingdom
| | - Richard G Bailey
- EaStChem School of Chemistry, University of St. Andrews, St Andrews, Scotland KY16 9ST, United Kingdom
| | - Heather Johnston
- EaStChem School of Chemistry, University of Edinburgh, Joseph Black Chemistry Building, Edinburgh, Scotland EH9 3FJ, United Kingdom
| | - John D Parkin
- EaStChem School of Chemistry, University of St. Andrews, St Andrews, Scotland KY16 9ST, United Kingdom
| | - Alison N Hulme
- EaStChem School of Chemistry, University of Edinburgh, Joseph Black Chemistry Building, Edinburgh, Scotland EH9 3FJ, United Kingdom
| | - Georg Hähner
- EaStChem School of Chemistry, University of St. Andrews, St Andrews, Scotland KY16 9ST, United Kingdom
| | - Paul N Barlow
- EaStChem School of Chemistry, University of Edinburgh, Joseph Black Chemistry Building, Edinburgh, Scotland EH9 3FJ, United Kingdom .,School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland EH9 3JY, United Kingdom
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3
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Parkin JD, Chisholm R, Frost AB, Bailey RG, Smith AD, Hähner G. Direct Organocatalytic Enantioselective Functionalization of SiO
x
Surfaces. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804814] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- John D. Parkin
- EaStCHEM School of Chemistry; University of St. Andrews; North Haugh St. Andrews KY16 9ST UK
| | - Ross Chisholm
- EaStCHEM School of Chemistry; University of St. Andrews; North Haugh St. Andrews KY16 9ST UK
| | - Aileen B. Frost
- EaStCHEM School of Chemistry; University of St. Andrews; North Haugh St. Andrews KY16 9ST UK
| | - Richard G. Bailey
- EaStCHEM School of Chemistry; University of St. Andrews; North Haugh St. Andrews KY16 9ST UK
| | - Andrew D. Smith
- EaStCHEM School of Chemistry; University of St. Andrews; North Haugh St. Andrews KY16 9ST UK
| | - Georg Hähner
- EaStCHEM School of Chemistry; University of St. Andrews; North Haugh St. Andrews KY16 9ST UK
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4
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Parkin JD, Chisholm R, Frost AB, Bailey RG, Smith AD, Hähner G. Direct Organocatalytic Enantioselective Functionalization of SiO x Surfaces. Angew Chem Int Ed Engl 2018; 57:9377-9381. [PMID: 29870577 DOI: 10.1002/anie.201804814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/29/2018] [Indexed: 01/17/2023]
Abstract
Traditional methods to prepare chiral surfaces involve either the adsorption of a chiral molecule onto an achiral surface, or adsorption of a species that forms a chiral template creating lattices with long range order. To date only limited alternative strategies to prepare chiral surfaces have been studied. In this manuscript a "bottom-up" approach is developed that allows the preparation of chiral surfaces by direct enantioselective organocatalytic reactions on a functionalized silicon oxide supported self-assembled monolayer (SAM). The efficient catalytic generation of enantiomerically enriched organic surfaces is achieved using a commercially available homogeneous isothiourea catalyst that promotes an enantioselective Michael-lactonization process upon a silicon-oxide supported SAM functionalized with a reactive trifluoroenone group. Chiral atomic force microscopy (χ-AFM) is used to probe the enantiomeric enrichment of the organic films by measurement of the force distributions arising from interaction of d- or l-cysteine-modified AFM tips and the organic films.
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Affiliation(s)
- John D Parkin
- EaStCHEMSchool of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
| | - Ross Chisholm
- EaStCHEMSchool of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
| | - Aileen B Frost
- EaStCHEMSchool of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
| | - Richard G Bailey
- EaStCHEMSchool of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
| | - Andrew D Smith
- EaStCHEMSchool of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
| | - Georg Hähner
- EaStCHEMSchool of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
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5
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Neyyappadath RM, Chisholm R, Greenhalgh MD, Rodríguez-Escrich C, Pericàs MA, Hähner G, Smith AD. Acylative Kinetic Resolution of Alcohols Using a Recyclable Polymer-Supported Isothiourea Catalyst in Batch and Flow. ACS Catal 2018. [DOI: 10.1021/acscatal.7b04001] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
| | - Ross Chisholm
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, U.K
| | - Mark D. Greenhalgh
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, U.K
| | - Carles Rodríguez-Escrich
- Institute
of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av. Països Catalans 16, 43007 Tarragona, Spain
| | - Miquel A. Pericàs
- Institute
of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av. Països Catalans 16, 43007 Tarragona, Spain
- Department
de Química Inorgànica i Orgànica, Universitat de Barcelona, 08080 Barcelona, Spain
| | - Georg Hähner
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, U.K
| | - Andrew D. Smith
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, U.K
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6
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Chisholm R, Parkin JD, Smith AD, Hähner G. Isothiourea-Mediated Organocatalytic Michael Addition-Lactonization on a Surface: Modification of SAMs on Silicon Oxide Substrates. Langmuir 2016; 32:3130-3138. [PMID: 27015037 DOI: 10.1021/acs.langmuir.5b04686] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Tailoring the functionality of self-assembled monolayers (SAMs) can be achieved either by depositing prefunctionalized molecules with the appropriate terminal groups or by chemical modification of an existing SAM in situ. The latter approach is particularly advantageous to allow for diversity of surface functionalization from a single SAM and if the incorporation of bulky groups is desired. In the present study an organocatalytic isothiourea-mediated Michael addition-lactonization process analogous to a previously reported study in solution is presented. An achiral isothiourea, 3,4-dihydro-2H-pyrimido[2,1-b]benzothiazole (DHPB), promotes the intermolecular Michael addition-lactonization of a trifluoromethylenone terminated SAM and a variety of arylacetic acids affording C(6)-trifluoromethyldihydropyranones tethered to the surface. X-ray photoelectron spectroscopy, atomic force microscopy, contact angle, and ellipsometry analysis were conducted to confirm the presence of the substituted dihydropyranone. A model study of this approach was also performed in solution to probe the reaction diastereoselectivity as it cannot be measured directly on the surface.
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Affiliation(s)
- Ross Chisholm
- EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, U.K
| | - John D Parkin
- EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, U.K
| | - Andrew D Smith
- EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, U.K
| | - Georg Hähner
- EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, U.K
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7
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Parkin JD, Hähner G. Contact-free experimental determination of the static flexural spring constant of cantilever sensors using a microfluidic force tool. Beilstein J Nanotechnol 2016; 7:492-500. [PMID: 27335740 PMCID: PMC4901535 DOI: 10.3762/bjnano.7.43] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 03/12/2016] [Indexed: 06/06/2023]
Abstract
Micro- and nanocantilevers are employed in atomic force microscopy (AFM) and in micro- and nanoelectromechanical systems (MEMS and NEMS) as sensing elements. They enable nanomechanical measurements, are essential for the characterization of nanomaterials, and form an integral part of many nanoscale devices. Despite the fact that numerous methods described in the literature can be applied to determine the static flexural spring constant of micro- and nanocantilever sensors, experimental techniques that do not require contact between the sensor and a surface at some point during the calibration process are still the exception rather than the rule. We describe a noncontact method using a microfluidic force tool that produces accurate forces and demonstrate that this, in combination with a thermal noise spectrum, can provide the static flexural spring constant for cantilever sensors of different geometric shapes over a wide range of spring constant values (≈0.8-160 N/m).
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Affiliation(s)
- John D Parkin
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
| | - Georg Hähner
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
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8
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Adamkiewicz M, O'Hagan D, Hähner G. Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs). Beilstein J Org Chem 2015; 10:2897-902. [PMID: 25550756 PMCID: PMC4273226 DOI: 10.3762/bjoc.10.307] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 11/11/2014] [Indexed: 11/28/2022] Open
Abstract
C11-Vinyl-terminated self-assembled monolayers (SAMs) on silica surfaces are successfully modified in C–C bond forming reactions with dihalocarbenes to generate SAMs, terminated with dihalo- (fluoro, chloro, bromo) cyclopropane motifs with about 30% surface coverage.
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Affiliation(s)
| | - David O'Hagan
- EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK
| | - Georg Hähner
- EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK
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9
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Abstract
A method suitable for the calibration of the spring constants of all torsional and lateral eigenmodes of micro- and nanocantilever sensors is described. Such sensors enable nanomechanical measurements and the characterization of nanomaterials, for example with atomic force microscopy. The method presented involves the interaction of a flow of fluid from a microchannel with the cantilever beam. Forces imparted by the flow cause the cantilever to bend and induce a measurable change of the torsional and lateral resonance frequencies. From the frequency shifts the cantilever spring constants can be determined. The method does not involve physical contact between the cantilever or its tip and a hard surface. As such it is non-invasive and does not risk damage to the cantilever. Experimental data is presented for two rectangular microcantilevers with fundamental flexural spring constants of 0.046 and 0.154 N m(-1). The experimentally determined torsional stiffness values are compared with those obtained by the Sader method. We demonstrate that the torsional spring constants can be readily calibrated using the method with an accuracy of around 15%.
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Affiliation(s)
- John D Parkin
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
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10
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Adamkiewicz M, O’Hagan D, Hähner G. Bis(trifluoromethyl)methylene addition to vinyl-terminated SAMs: a gas-phase C-C bond-forming reaction on a surface. Langmuir 2014; 30:5422-5428. [PMID: 24806554 PMCID: PMC4031204 DOI: 10.1021/la5011727] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 04/23/2014] [Indexed: 06/03/2023]
Abstract
Vinyl-terminated self-assembled monolayers (SAMs) on silicon oxide substrates were chemically modified by the addition of a bis(trifluoromethyl)methylene group in a rare gas-phase C-C bond-forming reaction to directly generate films carrying terminal CF3 groups. The vinyl-terminated films were treated with hexafluoroacetone azine (HFAA) for modification. The films were characterized with ellipsometry, contact angle measurements, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). In this study, we find that for optimized conditions clean reactions occur on a surface between SAMs with terminal olefins and HFAA, and the product is consistent with bis(trifluoromethyl)cyclopropanation formation after nitrogen extrusion.
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11
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Abstract
A method for the simultaneous calibration of the spring constants of all flexural modes of microcantilevers is presented. It is based on a flow of gas from a microchannel that interacts with the microcantilever. The gas flow causes a measurable shift in the resonance frequencies of thermal noise spectra of the flexural modes. From the magnitude of the frequency shifts of the individual modes the spring constants can be determined with high accuracy and precision. The method is non-invasive and does not risk damage to the cantilever. Experimental data are presented for several V-shaped and rectangular cantilevers with nominal fundamental spring constants in the range of 0.03-1.75 N m(-1). The spring constants of the fundamental modes compare favorably to those obtained using the Sader method. The higher modes of oscillation are readily calibrated with experimental uncertainties of 5-10%.
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Affiliation(s)
- John D Parkin
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK
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12
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She Z, DiFalco A, Hähner G, Buck M. Electron-beam patterned self-assembled monolayers as templates for Cu electrodeposition and lift-off. Beilstein J Nanotechnol 2012; 3:101-13. [PMID: 22428101 PMCID: PMC3304313 DOI: 10.3762/bjnano.3.11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Accepted: 01/18/2012] [Indexed: 05/26/2023]
Abstract
Self-assembled monolayers (SAMs) of 4'-methylbiphenyl-4-thiol (MBP0) adsorbed on polycrystalline gold substrates served as templates to control electrochemical deposition of Cu structures from acidic solution, and enabled the subsequent lift-off of the metal structures by attachment to epoxy glue. By exploiting the negative-resist behaviour of MBP0, the SAM was patterned by means of electron-beam lithography. For high deposition contrast a two-step procedure was employed involving a nucleation phase around -0.7 V versus Cu(2+)/Cu and a growth phase at around -0.35 V versus Cu(2+)/Cu. Structures with features down to 100 nm were deposited and transferred with high fidelity. By using substrates with different surface morphologies, AFM measurements revealed that the roughness of the substrate is a crucial factor but not the only one determining the roughness of the copper surface that is exposed after lift-off.
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Affiliation(s)
- Zhe She
- EaStCHEM School of Chemistry, University of St. Andrews, KY16 9ST, U.K
| | - Andrea DiFalco
- School of Physics and Astronomy, University of St. Andrews, KY16 9ST, U.K
| | - Georg Hähner
- EaStCHEM School of Chemistry, University of St. Andrews, KY16 9ST, U.K
| | - Manfred Buck
- EaStCHEM School of Chemistry, University of St. Andrews, KY16 9ST, U.K
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13
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Parkin JD, Hähner G. Mass determination and sensitivity based on resonance frequency changes of the higher flexural modes of cantilever sensors. Rev Sci Instrum 2011; 82:035108. [PMID: 21456790 DOI: 10.1063/1.3563724] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Micro- and nanocantilevers are increasingly employed as mass sensors. Most studies consider the first flexural mode and adsorbed masses that are either discretely attached or homogeneously distributed along the entire length of the cantilever. We derive general expressions that allow for the determination of the total attached mass with any mass distribution along the cantilever length and all flexural modes. The expressions are valid for all cantilevers whose flexural deflection can be described by a one-dimensional function. This approach includes the most common types of microcantilevers, namely, rectangular, picket, and V-shaped. The theoretical results are compared with experimental data up to the fourth flexural mode obtained from thermal noise spectra of rectangular and V-shaped cantilevers.
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Affiliation(s)
- John D Parkin
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, United Kingdom
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14
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Hähner G. Dynamic spring constants for higher flexural modes of cantilever plates with applications to atomic force microscopy. Ultramicroscopy 2010; 110:801-6. [DOI: 10.1016/j.ultramic.2010.02.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 02/02/2010] [Accepted: 02/09/2010] [Indexed: 11/25/2022]
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15
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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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Zwahlen M, Caseri WR, Hähner G. Pure and Molecularly Mixed Methyl- and Hydroxyl-Terminated Self-Assembled Dialkylammonium Monolayers on Mica: Wettability and Conformational Order. Z PHYS CHEM 2009. [DOI: 10.1524/zpch.2008.6010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Muscovite mica surfaces were coated with methyl- and hydroxyl-terminated dialkyldimethylammonium monolayers via ion exchange by immersion of the substrates into solutions of the corresponding salts. The samples were examined by water contact-angle measurements and near edge X-Ray absorption fine structure spectroscopy (NEXAFS). The purely methyl-terminated species was found to form self-assembled monolayers (SAMs) of comparable quality to those of a similar thiol/gold system as has been reported earlier. The hydroxyl-terminated surfactant established films with a lower degree of orientation under the same preparation conditions and showed a high water contact angle value for a hydrophilic surface (47°). The molecularly mixed film where one alkyl chain of the surfactant is methyl terminated and one hydroxyl terminated had a significantly lower wettability but established a similar degree of orientation as the film prepared from the purely OH-terminated species.
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17
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Abstract
Knowledge of the spring constants of microcantilevers is vital in atomic force microscopy and for cantilever-based devices that are, for example, employed as probes in biomedical applications. We compare two recently developed hydrodynamic methods for the determination of the normal spring constant of microcantilevers. Both approaches are non-invasive when determining the spring constant and require only knowledge of the thermal noise response of the cantilever in a fluid and its plan view dimensions. The methods do not bear the risk of damaging the cantilever and are therefore attractive for example in mass sensing applications in cases where the cantilever has been modified, e.g. with a coating. The specific strengths of the methods are discussed and the results for a variety of cantilevers are presented and compared.
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Affiliation(s)
- Gennady V Lubarsky
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK
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18
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19
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Abstract
We demonstrate a novel approach to determine the normal spring constant of microcantilevers. The cantilevers are placed parallel to a fluid flow thus establishing one of the walls of the flow channel. Resonance frequencies are recorded depending on the velocity of the fluid. The pressure gradient resulting from the flow causes the resonance frequency to change. This change can be exploited to deduce the cantilever spring constant with high precision. The method we present can be performed in situ and does not involve any contact of the cantilever with a surface thus having great potential for the calibration of modified probes and for being incorporated in microfluidic systems. In case the spring constant is known, the setup can also be employed to determine the velocity of fluid flows and the flow rate with high precision and up to high speeds.
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Affiliation(s)
- Gennady V Lubarsky
- EaStCHEM School of Chemistry, University of St. Andrews, North Haugh, St. Andrews KY16 9ST, United Kingdom
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20
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McLoughlin N, Lee SL, Hähner G. Temperature dependence of viscosity and density of viscous liquids determined from thermal noise spectra of uncalibrated atomic force microscope cantilevers. Lab Chip 2007; 7:1057-61. [PMID: 17653349 DOI: 10.1039/b705787c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We demonstrate that the thermal response of uncalibrated atomic force microscope cantilevers can be used to extract the density and the viscosity of viscous liquids with good accuracy. Temperature dependent thermal noise spectra were measured in water/poly(ethylene glycol) mixtures. Empirical parameters characteristic of the resonance behavior of the system were extracted from data recorded for one of the solutions at room temperature. These parameters were then employed to determine both viscosity and density values of the solutions simultaneously at different temperatures. In addition, activation energies for viscous flow were determined from the viscosity values obtained. The method presented is both fast and reliable and has the potential to be applied in connection with microfluidic systems, making macroscopic amounts of liquid and separate measurements with a viscometer and a densimeter redundant.
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Affiliation(s)
- Neal McLoughlin
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, UK
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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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Hähner G. Near edge X-ray absorption fine structure spectroscopy as a tool to probe electronic and structural properties of thin organic films and liquids. Chem Soc Rev 2006; 35:1244-55. [PMID: 17225886 DOI: 10.1039/b509853j] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synchrotron-based spectroscopic techniques have contributed significantly to a better understanding of the properties of materials on the macroscopic and microscopic scale over the last decades. They can be applied to samples from a diversity of fields, including Biology, Life Sciences, Chemistry and Materials. One of these techniques is Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy, revealing electronic structure and information on the orientation of adsorbed molecules. The present article describes the basics of the technique and the progress it has made over the last three decades, and summarizes some of its more recent developments and applications. This tutorial review article should be accessible for novices to the field from Physics, Chemistry, Biology, Materials, and the Life Sciences, interested in thin organic films and liquid systems.
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Affiliation(s)
- Georg Hähner
- EaStCHEM School of Chemistry, North Haugh, University of St Andrews, St Andrews, Fife KY16 9ST, UK.
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Hähner G, Zwahlen M, Caseri W. Solvent dependence of the molecular order in ion-exchanged self-assembled dialkylammonium monolayers on mica studied with soft X-ray absorption. J Colloid Interface Sci 2005; 291:45-52. [PMID: 15927195 DOI: 10.1016/j.jcis.2005.04.111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Revised: 04/28/2005] [Accepted: 04/29/2005] [Indexed: 10/25/2022]
Abstract
Dialkyldimethylammonium films on mica prepared via ion exchange from solution have been reported to be of high quality in terms of their density and molecular orientation. Different preparation procedures are described in the literature. The molecular order and the inclination of the alkyl chains, however, are often deduced from indirect experimental evidence such as the wettability and the film thickness. In the present study we employed near edge X-ray absorption fine structure spectroscopy (NEXAFS) to determine directly the order of the molecules adsorbed from different solvents (water, methanol, water/methanol 1:1, cyclohexanol, and chloroform). It was found that films prepared from different solvents are displaying large differences in the established surface coverage and orientation. In particular, NEXAFS disclosed that the orientation of the alkyl chains can differ significantly even when similar water contact angle values are observed.
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Affiliation(s)
- Georg Hähner
- EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK.
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Hähner G, Zwahlen M, Caseri W. Chain-length dependence of the conformational order in self-assembled dialkylammonium monolayers on mica studied with soft X-ray absorption. Langmuir 2005; 21:1424-1427. [PMID: 15697290 DOI: 10.1021/la047841u] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Self-assembled alkyl chain based monolayers on mica are important for industrial and technological processes since they can be employed for an organic modification of the inorganic substrate. The conformational structure and orientational order of the films determine the interaction of the modified substrate with the environment and the chemical character and stability of its surface. We have studied the conformational order in ion exchanged dialkylammonium monolayers adsorbed on mica depending on the length of the alkyl chains systematically with near-edge X-ray absorption fine structure spectroscopy (NEXAFS). In addition, films were characterized by water contact angle measurements. The experimentally determined average tilt angles of the chains are discussed in terms of the degree of order. It was found that the absolute number of gauche defects in the films increases with decreasing chain length.
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Affiliation(s)
- Georg Hähner
- School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9ST, UK.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Dicke C, Hähner G. Interaction between a Hydrophobic Probe and Tri(ethylene glycol)-Containing Self-assembled Monolayers on Gold Studied with Force Spectroscopy in Aqueous Electrolyte Solution. J Phys Chem B 2002. [DOI: 10.1021/jp013809m] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christian Dicke
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, U.K
| | - Georg Hähner
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, U.K
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de León AG, Dirix Y, Staedler Y, Feldman K, Hähner G, Caseri WR, Smith P. Method for fabricating pixelated, multicolor polarizing films. Appl Opt 2000; 39:4847-4851. [PMID: 18350078 DOI: 10.1364/ao.39.004847] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Pixelated, multicolor polarizing filters--of potential use in full-color displays--were produced by what we believe to be a novel method, i.e., masked evaporation of silver and gold onto glass substrates partially covered with separated sub-micrometer-wide strips of oriented poly(tetrafluoroethylene) (PTFE), prepared by friction deposition. The evaporated metal films preferentially nucleated at the glass surface and, consequently, formed parallel arrays in between the PTFE strips. The structures thus produced feature a strong angle-dependent absorption of polarized visible light, allowing for optical switching between red and blue and between green and yellow.
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Affiliation(s)
- A G de León
- Department of Materials, Eidgenössische Technische Hochschule Zürich, CH-8092 Zürich, Switzerland
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Feldman K, Hähner G, Spencer ND, Harder P, Grunze M. Probing Resistance to Protein Adsorption of Oligo(ethylene glycol)-Terminated Self-Assembled Monolayers by Scanning Force Microscopy. J Am Chem Soc 1999. [DOI: 10.1021/ja991049b] [Citation(s) in RCA: 240] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- K. Feldman
- Contribution from the Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland, and Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, 69120 Heidelberg, Germany
| | - G. Hähner
- Contribution from the Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland, and Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, 69120 Heidelberg, Germany
| | - N. D. Spencer
- Contribution from the Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland, and Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, 69120 Heidelberg, Germany
| | - P. Harder
- Contribution from the Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland, and Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, 69120 Heidelberg, Germany
| | - M. Grunze
- Contribution from the Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland, and Angewandte Physikalische Chemie, Universität Heidelberg, INF 253, 69120 Heidelberg, Germany
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Brovelli D, Caseri WR, Hähner G. Self-Assembled Monolayers of Alkylammonium Ions on Mica: Direct Determination of the Orientation of the Alkyl Chains. J Colloid Interface Sci 1999; 216:418-423. [PMID: 10421750 DOI: 10.1006/jcis.1999.6340] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Near edge X-ray absorption fine structure spectroscopy was used to study the orientation of the alkyl chains in monolayers of R(1)(3)R(2)N(+) and R(1)(2)R(2)(2)N(+) (R(1) = methyl and R(2) = octadecyl), self-assembled on muscovite mica via ion exchange. The alkyl chains adopt a random orientation in the monooctadecylammonium ions. Dimethyldioctadecylammonium ions, however, form a well-ordered self-assembled monolayer. The average tilt angle between the alkyl chains and the surface normal is 38 degrees. The difference between the mono- and the dioctadecylammonium ions reflects at least partially the packing density of the alkyl chains. When adsorbed on muscovite mica, dimethyldioctadecylammonium ions establish monolayers that are similarly well ordered as alkanethiol monolayers on gold. Copyright 1999 Academic Press.
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Affiliation(s)
- D Brovelli
- Department of Materials, ETH Zürich, Sonneggstr. 5, Laboratory for Surface Science and Technology, Zürich, CH-8092, Switzerland
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Sittig C, Hähner G, Marti A, Textor M, Spencer ND, Hauert R. The implant material, Ti6Al7Nb: surface microstructure, composition and properties. J Mater Sci Mater Med 1999; 10:191-8. [PMID: 15348150 DOI: 10.1023/a:1008997726370] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The excellent biocompatibility of titanium and its alloys is intimately related with the properties of the surface in contact with the biological environment, and therefore it is closely connected with the stable, passivating oxide layer that forms on its surface. In the present paper, the oxide layer on the alloy Ti6Al7Nb has been characterized using X-ray photoelectron spectroscopy, scanning Auger microscopy and pH-dependent lateral force microscopy. The alloying elements Al and Nb are incorporated in the oxide layer and detected in their most stable oxidized form, as Al2O3 and Nb2O5. Their distribution in the oxide reflects the underlying alpha-beta microstructure, with enrichment of Al in the alpha- and of Nb in the beta-phase (determined by electron microprobe). Friction measurements (lateral force microscopy) indicate slightly different, pH-dependent, lateral forces above the alpha- and beta-phase structures that point to small local variations in surface charges.
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Affiliation(s)
- C Sittig
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, Sonneggstr. 5, CH - 8092 Zürich, Switzerland
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Hähner G, Marti A, Spencer ND, Caseri WR. Orientation and electronic structure of methylene blue on mica: A near edge x‐ray absorption fine structure spectroscopy study. J Chem Phys 1996. [DOI: 10.1063/1.471451] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kinzler M, Schertel A, Hähner G, Wöll C, Grunze M, Albrecht H, Holzhüter G, Gerber T. Structure of mono‐ and multilayer Langmuir–Blodgett films from Cd arachidate and Ca arachidate. J Chem Phys 1994. [DOI: 10.1063/1.466867] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Zubrägel C, Schneider F, Neumann M, Hähner G, Wöll C, Grunze M. Electronic structure of alkane chains. Complete one-dimensional band structures of the valence states. Chem Phys Lett 1994. [DOI: 10.1016/0009-2614(94)00057-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Hähner G, Kinzler M, Wöll C, Grunze M, Cederbaum LS. Near edge x-ray-absorption fine-structure determination of alkyl-chain orientation: Breakdown of the "building-block" scheme. Phys Rev Lett 1991; 67:851-854. [PMID: 10045005 DOI: 10.1103/physrevlett.67.851] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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