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Björefors, Fredrik
Alternative names
Publications (10 of 29) Show all publications
Ulrich, C., Louthander, D., Mårtensson, P., Kluftinger, A., Gawronski, M. & Björefors, F. (2012). Evaluation of industrial cutting fluids using electrochemical impedance spectroscopy and multivariate data analysis. Talanta: The International Journal of Pure and Applied Analytical Chemistry, 97, 468-472
Open this publication in new window or tab >>Evaluation of industrial cutting fluids using electrochemical impedance spectroscopy and multivariate data analysis
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2012 (English)In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 97, p. 468-472Article in journal (Refereed) Published
Abstract [en]

In this paper, we explore the combination of electrochemical impedance spectroscopy (EIS) and multivariate data analysis to evaluate the concentration and pH of an industrial cutting fluid. These parameters are vital for the performance of for instance tooling processes, and an on-line monitoring system would be very beneficial. It is shown that both the total impedance and the phase angle contain information that allows the simultaneous discrimination of the concentration and the pH. The final evaluation was made with a regression model, namely partial least squares (PLS). This approach provided a way to quickly and simply find the correlation between EIS data and the sought parameters. The results from the measurements showed the possibility to predict the concentration and pH level, indicating the potential of this method for on-line measurements.

Place, publisher, year, edition, pages
Elsevier, 2012
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-14888 (URN)10.1016/j.talanta.2012.05.001 (DOI)000308268800071 ()
Note

funding agencies|Carl Trygger Foundation (CTS)||Swedish Sensor Center (S-SENCE)||

Available from: 2008-09-29 Created: 2008-09-29 Last updated: 2017-12-13
Lee, H.-H., Ruzele, Z., Malysheva, L., Onipko, A., Gutes, A., Björefors, F., . . . Liedberg, B. (2009). Long-Chain Alkylthiol Assemblies Containing Buried In-Plane Stabilizing Architectures. Langmuir, 25(24), 13959-13971
Open this publication in new window or tab >>Long-Chain Alkylthiol Assemblies Containing Buried In-Plane Stabilizing Architectures
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2009 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 24, p. 13959-13971Article in journal (Refereed) Published
Abstract [en]

A series of alkylthiol compounds were synthesized to study the formation and structure of complex self-assembled monolayers (SAMs) consisting of interchanging structural modules stabilized by intermolecular hydrogen bonds. The chemical structure of the synthesized compounds, HS(CH2)(15)CONH(CH2CH2O)(6)CH2CONH-X, where X refers to the extended chains of either -(CH2)(n)CH3 or -(CD2)(n)CD3, with n = 0, 1, 7, 8, 15, was confirmed by NMR and elemental analysis. The formation of highly ordered, methyl-terminated SAMs oil gold from diluted ethanolic solutions of these compounds was revealed using contact angle goniometry, mill ellipsometry, cyclic voltammetry, and infrared reflection absorption spectroscopy. The experimental work was complemented with extensive DFT modeling of infrared spectra and molecular orientation. New assignments were introduced for both nondeuterated and deuterated Compounds. The latter set of compounds also served as a convenient tool to resolve the packing, conformation, and orientation of the buried and extended modules within the SAM. Thus, it was shown that the lower alkyl portion together with the hexa(ethylene glycol) portion is stabilized by the two layers of lateral hydrogen bonding networks between the amide groups, and they provide it Structurally robust support for the extended alkyls, The presented system can be considered to be an extension of the well-known alkyl SAM platform, enabling precise engineering of nanoscopic architectures oil the length scale from a Few to similar to 60 angstrom for applications such as cell membrane mimetics, molecular nanolithography, and so forth.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-52826 (URN)10.1021/la901668u (DOI)
Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
Ulrich, C., Andersson, O., Nyholm, L. & Björefors , F. (2009). Potential and Current Density Distributions at Electrodes Intended for Bipolar Patterning. Analytical Chemistry, 81(1), 453-459
Open this publication in new window or tab >>Potential and Current Density Distributions at Electrodes Intended for Bipolar Patterning
2009 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 1, p. 453-459Article in journal (Refereed) Published
Abstract [en]

This paper deals with the use of reaction gradients on bipolar electrodes for the patterning of electrode surfaces. More specifically, the potential and current density distributions in two setups containing bipolar electrodes were investigated to optimize and design specific gradient geometries. Comparisons with simulations based on simple conductivity models showed a good qualitative agreement, demonstrating that these models could be used to predict bipolar behavior in more complex setups. In conjunction with imaging surface plasmon resonance (iSPR) experiments, the reaction gradients on bipolar electrodes could further be visualized. It was, for example, found that the gradient in potential difference was approximately linearly distributed in the center of the bipolar electrode and that these potential differences could be determined using an ordinary Ag/AgCl reference electrode. The present results thus provide a better understanding of the processes relevant for bipolar patterning. This approach was finally used to generate a circular gradient region in a self-assembled monolayer, thereby showing the possibilities to create interesting substrates for biosensors and microarray applications.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-16423 (URN)10.1021/ac801871c (DOI)
Available from: 2009-01-23 Created: 2009-01-23 Last updated: 2017-12-14
Aili, D., Enander, K., Rydberg, J., Nesterenko, I., Björefors, F., Baltzer, L. & Liedberg, B. (2008). Controlled Assembly of Gold Nanoparticles using De Novo Designed Polypeptide Scaffolds. In: Proceedings SPIE, Vol. 6885, Photonic Biosensing and Microoptics: (pp. 688506-1-688506-8).
Open this publication in new window or tab >>Controlled Assembly of Gold Nanoparticles using De Novo Designed Polypeptide Scaffolds
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2008 (English)In: Proceedings SPIE, Vol. 6885, Photonic Biosensing and Microoptics, 2008, p. 688506-1-688506-8Conference paper, Published paper (Refereed)
Abstract [en]

Heterodimerization between designed helix-loop-helix polypeptides was utilized in order to assemble gold nanoparticles on planar substrates. The peptides were designed to fold into four-helix bundles upon dimerization. A Cys-residue in the loop region was used to immobilize one of the complementary peptides on a maleimide containing SAM on planar gold substrates whereas the second peptide was immobilized directly on gold nanoparticles. Introducing the peptide decorated particles over a peptide functionalized surface resulted in particle assembly. Further, citrate stabilized particles were assembled on amino-silane modified glass and silicon substrates. By subsequently introducing peptides and gold nanoparticles, particle-peptide hybrid multi layers could be formed.

Keywords
Heterodimerization, polypeptides, gold nanoparticles, four-helix bundle, helix-loop-helix, self-assembly
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:liu:diva-15118 (URN)10.1117/12.775806 (DOI)
Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-01-12Bibliographically approved
Eskhult, J., Ulrich, C., Björefors, F. & Nyholm, L. (2008). Current oscillations during chronoamperometric and cyclic voltammetric measurements in alkaline Cu(II)-citrate solutions. Electrochimica Acta, 53(5), 2188-2197
Open this publication in new window or tab >>Current oscillations during chronoamperometric and cyclic voltammetric measurements in alkaline Cu(II)-citrate solutions
2008 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 5, p. 2188-2197Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that current oscillations can be observed during chronoamperometric and cyclic voltammetric experiments in solutions containing 0.4 M CuSO4 and 1.2 M citrate at pH 11 and 50 °C. The oscillations, which are shown to originate from local variations in the pH, result in the deposition of nanostructured Cu and Cu2O materials. It is concluded that the current oscillations are analogous to the previously described potential oscillations obtained under controlled current conditions in alkaline Cu(II)-lactate, -tartrate and -citrate solutions. Rotating disk electrode results clearly show that the reduction of the Cu(II)-complexes is kinetically controlled and that the rate of the reduction increases with increasing pH and temperature. It is also shown that the presence of a cathodic peak on the anodic scan in the cyclic voltammograms can be used to identify the experimental conditions leading to the spontaneous current (or potential) oscillations. Electrochemical quartz crystal microbalance results indicate that the cathodic peak stems from an increased rate of the reduction of the Cu(II)-citrate complexes due to a rapid increase in the local pH. This causes Cu2O rather than Cu to be deposited which, however, results in a decrease in the local pH and a decreasing current. In situ ellipsometry data confirm that Cu2O deposition replaces that of Cu in the potential region of the cathodic peak. The present findings should facilitate syntheses of nanolayered materials based on spontaneous potential or current oscillations.

Keywords
Current oscillations, Cu; Cu2O, Nanolayers, Local pH variations, Citrate
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-14885 (URN)10.1016/j.electacta.2007.09.032 (DOI)
Available from: 2008-09-29 Created: 2008-09-29 Last updated: 2017-12-13
Masunaga, K., Michiwaki, S., Izumi, R., Ivarsson, P., Björefors, F., Lundström, I., . . . Toko, K. (2008). Development of sensor surface with recognition of molecular substructure. Sensors and actuators. B, Chemical, 130(1), 330-337
Open this publication in new window or tab >>Development of sensor surface with recognition of molecular substructure
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2008 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 130, no 1, p. 330-337Article in journal (Refereed) Published
Abstract [en]

A biological olfaction system is one of the highest performance chemical sensing systems for low-molecular-weight compounds. An ability of recognizing a various molecular properties based on their structures is essential for a biological odor recognition process. For the development of a sensor mimicking the olfactory system, we have formed benzene-patterned self-assembled monolayer (SAM) on the sensor surface using SAMs with nanostructure that serves as adsorption sites for benzene ring, which is representative substructure of aromatics. The structure of the benzene-patterned SAM surface was analyzed by contact-angle measurement, ellipsometry, cyclic voltammetry (CV) and atomic force microscopy (AFM). Moreover, the electrodes evaluated as sensor surfaces with cyclic surface-polarization impedance (cSPI) sensor that measures changes in impedance of the electrode surface by adsorption of substances. The results of cSPI indicated the benzene-patterned SAM surface could distinguish benzene by recognizing of the hydrophobicity and the molecular size. © 2007 Elsevier B.V. All rights reserved.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-44512 (URN)10.1016/j.snb.2007.08.027 (DOI)76939 (Local ID)76939 (Archive number)76939 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
Aili, D., Enander, K., Rydberg, J., Nesterenko, I., Björefors, F., Baltzer, L. & Liedberg, B. (2008). Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles. Journal of the American Chemical Society, 130(17), 5780-5788
Open this publication in new window or tab >>Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles
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2008 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 17, p. 5780-5788Article in journal (Refereed) Published
Abstract [en]

Reversible assembly of gold nanoparticles controlled by the homodimerization and folding of an immobilized de novo designed synthetic polypeptide is described. In solution at neutral pH, the polypeptide folds into a helix–loop–helix four-helix bundle in the presence of zinc ions. When immobilized on gold nanoparticles, the addition of zinc ions induces dimerization and folding between peptide monomers located on separate particles, resulting in rapid particle aggregation. The particles can be completely redispersed by removal of the zinc ions from the peptide upon addition of EDTA. Calcium ions, which do not induce folding in solution, have no effect on the stability of the peptide decorated particles. The contribution from folding on particle assembly was further determined utilizing a reference peptide with the same primary sequence but containing both D and L amino acids. Particles functionalized with the reference peptide do not aggregate, as the peptides are unable to fold. The two peptides, linked to the nanoparticle surface via a cysteine residue located in the loop region, form submonolayers on planar gold with comparable properties regarding surface density, orientation, and ability to interact with zinc ions. These results demonstrate that nanoparticle assembly can be induced, controlled, and to some extent tuned, by exploiting specific molecular interactions involved in polypeptide folding.

Place, publisher, year, edition, pages
ACS Publications, 2008
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:liu:diva-15116 (URN)10.1021/ja711330f (DOI)
Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-01-12Bibliographically approved
Ulrich, C., Andersson, O., Nyholm, L. & Björefors, F. (2008). Formation and Imaging of Gradients in Electrochemical Reactions and Molecular Films. In: ESEAC2008 European Society for ElectroAnalytical Chemistry,2008.
Open this publication in new window or tab >>Formation and Imaging of Gradients in Electrochemical Reactions and Molecular Films
2008 (English)In: ESEAC2008 European Society for ElectroAnalytical Chemistry,2008, 2008Conference paper, Published paper (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-44496 (URN)76879 (Local ID)76879 (Archive number)76879 (OAI)
Available from: 2009-10-10 Created: 2009-10-10
Ulrich, C., Andersson, O., Nyholm, L. & Björefors, F. (2008). Formation of Molecular Gradients on Bipolar Electrodes. Angewandte Chemie International Edition, 47(16), 3034-3036
Open this publication in new window or tab >>Formation of Molecular Gradients on Bipolar Electrodes
2008 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 47, no 16, p. 3034-3036Article in journal (Refereed) Published
Keywords
Bipolar electrodes, electrochemistry, imaging, molecular gradients, surface chemistry
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-14881 (URN)10.1002/anie.200705824 (DOI)
Available from: 2008-09-29 Created: 2008-09-29 Last updated: 2017-12-13Bibliographically approved
Andersson, O., Ulrich, C., Björefors, F. & Liedberg, B. (2008). Imaging SPR for detection of local electrochemical processes on patterned surfaces. Sensors and actuators. B, Chemical, 134(2), 545-550
Open this publication in new window or tab >>Imaging SPR for detection of local electrochemical processes on patterned surfaces
2008 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 134, no 2, p. 545-550Article in journal (Refereed) Published
Abstract [en]

Imaging surface plasmon resonance (iSPR) was used in conjunction with voltammetry to investigate the possibility of detecting local electrochemical processes in situ on chemically modified electrodes. More specifically, a pattern of self-assembled monolayers (SAMs) of thiocholesterol and 1-hexadecanethiol was microcontact printed on gold substrates, and the blocking characteristics on different parts of the pattern were investigated. The SPR images reflected the changes in the refractive index over the working electrode due to electrochemical processes, which in the present case showed the ability of the SAMs to impede faradaic reactions. The results show that differences in packing densities or porosity of SAMs in different regions of a patterned surface can be visualized as electrochemical images using iSPR. The strength of utilizing an optical detection method for electrochemical characterization lies in the ability to achieve lateral resolution in real-time. Electrochemical reactions can also be used to enhance the contrast in SPR images of thin layers of components with similar thicknesses and refractive indices.

Keywords
Imaging surface plasmon resonance, Microcontact printing, Local electrochemical analysis, Surface analysis
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-14884 (URN)10.1016/j.snb.2008.05.042 (DOI)
Available from: 2008-09-29 Created: 2008-09-29 Last updated: 2017-12-13
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