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  • 1.
    Aili, Daniel
    et al.
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Enander, Karin
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Rydberg, Johan
    Linköping University, The Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Nesterenko, Irina
    Linköping University, The Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Baltzer, Lars
    Division of Organic Chemistry, Department of Biochemistry and Organic Chemistry, BMC, Box 599, Uppsala University, SE-751 24 Uppsala, Sweden..
    Liedberg, Bo
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Controlled Assembly of Gold Nanoparticles using De Novo Designed Polypeptide Scaffolds2008In: Proceedings SPIE, Vol. 6885, Photonic Biosensing and Microoptics, 2008, p. 688506-1-688506-8Conference 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.

  • 2.
    Aili, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Rydberg, Johan
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Nesterenko, Irina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Baltzer, Lars
    Department of Biochemistry and Organic Chemistry, BMC, Box 599, Uppsala UniVersity, SE-751 24 Uppsala, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 17, p. 5780-5788Article in journal (Refereed)
    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.

  • 3.
    Andersson, Olof
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Ulrich, Christian
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Ederth, Thomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Characterization of Surface Modifications using Voltammetry and Imaging SPR2006In: Europtrode VIII, 2006Conference paper (Other academic)
  • 4.
    Andersson, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Ulrich, Christian
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Imaging SPR for detection of local electrochemical processes on patterned surfaces2008In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 134, no 2, p. 545-550Article in journal (Refereed)
    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.

  • 5.
    Andersson, Olof
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Ulrich, Christian
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Characterization Of Surface Modifications Using Voltammetry Combined With Imaging SPR2006Conference paper (Other academic)
  • 6.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Daniels, Tad
    Allara, David
    Molecular Electronics - Assembly and Contacting of Single Molecular Wires2003In: Analysdagarna,2003, 2003Conference paper (Refereed)
    Abstract [en]

      

  • 7.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Ekeroth, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Borgh, Annika
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Konradsson, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry .
    Electrochemical Analysis of Self-Assembled Monolayers2001In: Analysdagarna,2001, 2001Conference paper (Refereed)
  • 8.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Characterization of the capacitance and quality of thiol based self-assembled monolayers by impedance spectroscopy and cyclic voltammetry2000In: ESEAC2000 European Society for ElectroAnalytical Chemistry,2000, 2000Conference paper (Other academic)
  • 9.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Petoral Jr, Rodrigo M.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Electrochemical impedance spectroscopy for investigations on ion permeation in ?-functionalized self-assembled monolayers2007In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 79, no 21, p. 8391-8398Article in journal (Refereed)
    Abstract [en]

    Electrochemical impedance spectroscopy was employed to explore the possibility of relating the permeation of electrolyte ions in ?-functionalized self-assembled monolayers to structural or polarity changes induced by interaction with metal ions. The monolayers were based on alkanethiols modified with a phosphorylated tyrosine analogue, which from previous work are known to drastically change their organization on gold surfaces upon interaction with aluminum and magnesium ions. The ion permeation was evaluated by using relatively low excitation frequencies, 1000 to 2 Hz, and quantified by an extra resistive component in the equivalent circuit (R SAM). The extent of ion permeation influenced by the dc potential, the electrolyte concentration, the functional group, and the thiol length were also investigated. It was, for example, found that RSAM decreased ~20% when the thiol organization collapsed and that RSAM increased ~4-5 times when the electrolyte concentration was decreased by 1 order of magnitude. Interesting observations were also made regarding the potential dependence of RSAM and the double layer capacitance. The evaluation of the ion permeation can be used to indirectly detect whether the organization of a SAM is influenced by, for example, electric fields or chemical and biological interactions. This analysis can be performed without addition of redox species, but is on the other hand complicated by the fact that other factors also influence the presence of ions within the monolayer. In addition, a second parallel RC process was obtained in some of the impedance spectra when using even lower frequencies, and its resistive component revealed different results compared to RSAM. Such data may be useful for the understanding of complex double layer phenomena at modified electrodes. © 2007 American Chemical Society.

  • 10.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Stålhandske, Per
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Characterization of the Capacitance and Quality of Thiol Based Self-Assembled Monolayers by Impedance Spectroscopy and Cyclic Voltammetry2000In: ISE 2000 International Society of Electrochemistry,2000, 2000Conference paper (Other academic)
  • 11.
    Ekeroth, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Borgh, Annika
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry . Linköping University, The Institute of Technology.
    Electrochemical Evaluation of the Interfacial Capacitance upon Phosphorylation of Amino Acid Analogue Molecular Films2001In: Analytical Chemistry, ISSN 0003-2700, Vol. 73, no 18, p. 4463-4468Article in journal (Refereed)
    Abstract [en]

    An approach based on electrochemistry to differentiate between phosphorylated and nonphosphorylated amino acid analogues adsorbed on gold is presented. Analogues of serine, threonine, and tyrosine, containing thiohexadecyl headgroups, were synthesized and assembled on gold, and the surface capacitance was evaluated using electrochemical impedance spectroscopy. A procedure for deprotection of tert-butyl phosphate protecting groups, on the monolayer, is also described. Characterizations of the assembled analogues by cyclic voltammetry, infrared spectroscopy, and ellipsometry are used to confirm the insulating properties of the monolayers and the outcome of surface modifications. The results from cyclic voltammetry show good insulating properties for the monolayers even after phosphate deprotection. The infrared measurements reveal well-ordered monolayers, and the thickness from ellipsometry is in good agreement with expectations from molecular modeling. The impedance experiments show a capacitance increase up to 0.6 μF/cm2 as phosphate groups are introduced. The results in this study indicate the possibility of using a surface chemical and impedance spectroscopy approach to detect the kinase/phosphatase activity and kinetics involved in phosphorylation reactions.

  • 12.
    Ekeroth, Johan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Monitoring the interfacial capacitance at self-assembled phosphate monolayers on gold electrodes upon interaction with calcium and magnesium2002In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 74, no 9, p. 1979-1985Article in journal (Refereed)
    Abstract [en]

    Electrochemical impedance spectroscopy has been used to evaluate the change in interracial capacitance upon calcium and magnesium coordination to a phosphate-modified electrode. The phosphate electrode was prepared via immobilization of phosphorylated, thiol-containing, serine analogues onto gold. Upon subjection to calcium and magnesium, a substantial drop in capacitance was observed. Magnesium displayed the largest influence on the capacitance: a 27% capacitance drop was observed upon introduction of a 1 mM solution of magnesium ions. The lowered capacitance is a result of a change in the potential and charge distribution at the film/electrolyte interface as the cations coordinate to the phosphate groups. Moreover, the relationship between electrode potential and capacitance has been investigated and reveals a significant difference between monovalent and divalent cations. As complementary information, infrared reflection absorption spectra of the phosphorylated monolayer having different counterions are presented. The results reported in this paper indicate that the phosphorylated amino acid analogue monolayers could be used in investigations of the biochemically important coordination of calcium and magnesium to phosphates and phosphorylated amino acids.

  • 13.
    Eskhult, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ulrich, Christian
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Nyholm, Leif
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Current oscillations during chronoamperometric and cyclic voltammetric measurements in alkaline Cu(II)-citrate solutions2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 5, p. 2188-2197Article in journal (Refereed)
    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.

  • 14.
    Holmin, Susanne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Krantz-Rulcker, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Investigation of Electrode Materials as Sensors in a Voltammetric Electronic Tongue2002In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 14, no 12, p. 839-847Article in journal (Refereed)
    Abstract [en]

    In this work different electrode materials were investigated as sensors in a voltammetric electronic tongue. Basically, the electronic tongue is based on the combination of nonspecific sensors (electrodes) and pattern recognition tools, for example principal component analysis (PCA). Copper. glassy carbon, nickel, palladium, silver, tin, titanium and zirconium together with more traditional electrode materials such as gold, iridium, and platinum were studied. Cyclic voitammetry was applied to study typical model reactions in solutions containing different electroactive compounds, like ascorbic acid, glucose, histidine and potassium hexacyanoferrate(II). Different sensitivity and selectivity were obtained with the electrodes. Large responses were for example found for the amino acid and the carbohydrate using the copper, nickel and silver electrode. Some of the electrodes were employed in multicomponent solutions, i.e., liquid washing detergents from different suppliers together with differential pulse voltammetry. Responses from the electrodes in combination with PCA showed that they separated the detergents to different extents. This was further used when information from the sensors was merged together for successful discrimination of the detergents. It was found that two detergents close to each other in the score plot were from the same supplier. Furthermore. scanning electron microscopy (SEM) was used to monitor surface changes at the nonnoble electrodes (copper, nickel, and silver).

  • 15.
    Klett, Oliver
    et al.
    Uppsala universitet.
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Nyholm, Leif
    Uppsala universitet.
    Elimination of High-Voltage Field Effects in End Column Electrochemical Detection in Capillary Electrophoresis by Use of On-Chip Microband Electrodes2001In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 73, no 8, p. 1909-1915Article in journal (Refereed)
  • 16.
    Lee, Hung-Hsun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ruzele, Zivile
    Institute Phys, Department Funct Nanomat, LT-02300 Vilnius, Lithuania .
    Malysheva, Lyuba
    Bogolyubov Institute Theoret Phys, UA-03143 Kiev, Ukraine .
    Onipko, Alexander
    Bogolyubov Institute Theoret Phys, UA-03143 Kiev, Ukraine .
    Gutes, Albert
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Valiokas, Ramunas
    Institute Phys, Department Funct Nanomat, LT-02300 Vilnius, Lithuania .
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Long-Chain Alkylthiol Assemblies Containing Buried In-Plane Stabilizing Architectures2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 24, p. 13959-13971Article in journal (Refereed)
    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.

  • 17.
    Lundgren, Anders O
    et al.
    University of Gothenburg.
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Olofsson, Linda G M
    University of Gothenburg.
    Elwing , Hans
    University of Gothenburg.
    Self-Arrangement Among Charge-Stabilized Gold Nanoparticles on a Dithiothreitol Reactivated Octanedithiol Monolayer2008In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 11, p. 3989-3992Article in journal (Refereed)
    Abstract [en]

    Gold surfaces and structures modified with octanedithiol were reacted with dithiothreitol prior to immersion in buffered solutions of charge stabilized gold nanoparticles. The procedure gives a dithiol layer with adequate properties for a homogeneous octanedithiol monolayer and uniform and reproducible gold nanoparticle binding. The distance between the adsorbing particles is controlled by the particle electrostatic interactions and can be carefully tuned by variation of ionic strength. To some extent, long-range ordering occurs among the adsorbed particles. This behavior is facilitated by the particles small size compared to the Debye screening but also by the homogeneity of the surface modification. The simple character of the system makes it attractive for fabrication of controlled nanoparticle arrays where further chemical and biological modifications are required.

  • 18.
    Masunaga, Kumi
    et al.
    Kyushu University Graduate School of Systems Life Sciences.
    Michiwaki, Shintaro
    Kyushu University Graduate School of Information Science and Electrial Engineering.
    Izumi, Ryosuke
    Kyushu University Graduate School of Information Science and Electrial Engineering.
    Ivarsson, Patrik
    Asko Cylinda AB .
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Hayashi, Kenshi
    Kyushu University Graduate School of Information Science and Electrial Engineering.
    Toko, Kiyoshi
    Kyushu University Graduate School of Information Science and Electrial Engineering.
    Development of sensor surface with recognition of molecular substructure2008In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 130, no 1, p. 330-337Article in journal (Refereed)
    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.

  • 19. Nilsson, S
    et al.
    Svedberg, M
    Pettersson, J
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Markides, K
    Nyholm, L
    Evaluations of the stability of sheathless electrospray ionization mass spectrometry emitters using electrochemical techniques2001In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 73, no 19, p. 4607-4616Article in journal (Refereed)
    Abstract [en]

    The processes that cause the failure of sheathless electrospray ionization (ESI) emitters, based on different kinds of gold coatings on fused-silica capillaries, are described and explained. The methods chosen for this study include electrochemical methods, ICPMS analysis of the electrolytes used, SEM studies, and electrospray experiments. Generally, the failure occurs by loss of the conductive coating. It is shown that emitters with sputter-coated gold lose their coatings because of mechanical stress caused by the gas evolution accompanying water oxidation or reduction. Emitters with gold coatings on top of adhesion layers of chromium and nickel alloy withstand this mechanical stress and have excellent durability when operating as cathodes. When operating as anodes, the adhesion layer is electrochemically dissolved through the gold film, and the gold film then flakes off. It is shown that the conductive coating behaves as a cathode even in the positive electrospray mode when the magnitude of a superimposed reductive electrophoretic current exceeds that of the oxidative electrospray current. Fairy-dust coatings developed in our laboratory (see Barnidge, D. R., et al. Anal. Chem. 1999, 71, 4115-4118) by gluing gold dust onto the emitter, are unaffected by the mechanical stress due to gas evolution. When oxidized, the fairy-dust coatings show an increased surface roughness and decreased conductivities due to the formation of gold oxide. The resistance of this oxide layer is however negligible in comparison with that of the gas phase in ESI. Furthermore, since no flaking and only negligible electrochemical etching of gold was found, practically unlimited emitter lifetimes may be achieved with fairy-dust coatings.

  • 20.
    Ulrich, Christian
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Leif, Nyholm
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Surface Gradients on Bipolar Electrodes2008In: ESEAC2008 European Society for ElectroAnalytical Chemistry,2008, 2008Conference paper (Other academic)
  • 21.
    Ulrich, Christian
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    New Methods in Surface Science and Surface Analysis-Towards Biomimetic Sensing2007In: A Vinnova program conference: Multidisciplinary BIO,2007, 2007Conference paper (Refereed)
    Abstract [en]

            

  • 22.
    Ulrich, Christian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Nyholm, Leif
    Uppsala University.
    Björefors , Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Potential and Current Density Distributions at Electrodes Intended for Bipolar Patterning2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 1, p. 453-459Article in journal (Refereed)
    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.

  • 23.
    Ulrich, Christian
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Nyholm, Leif
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Formation and Imaging of Gradients in Electrochemical Reactions and Molecular Films2008In: ESEAC2008 European Society for ElectroAnalytical Chemistry,2008, 2008Conference paper (Other academic)
  • 24.
    Ulrich, Christian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Nyholm, Leif
    Department of Materials Chemistry, Uppsala University, P.O. Box 538, 75121 Uppsala, Sweden.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Formation of Molecular Gradients on Bipolar Electrodes2008In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 47, no 16, p. 3034-3036Article in journal (Refereed)
  • 25.
    Ulrich, Christian
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Electrochemistry Combined With Imaging Ellipsometry2006Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Konferensbidrag (i form av Poster) vid "ISE", Edingburgh, Scotland, August

  • 26.
    Ulrich, Christian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Louthander, Dan
    Senset AB, Universitetsvägen 14, SE-583 30 Linköping, Sweden.
    Mårtensson, Per
    Senset AB, Universitetsvägen 14, SE-583 30 Linköping, Sweden.
    Kluftinger, André
    WIKA Alexander Wiegand GmbH & Co. KG, Alexander-Wiegand-Strasse, 63911 Klingenberg, Germany.
    Gawronski, Michael
    WIKA Alexander Wiegand GmbH & Co. KG, Alexander-Wiegand-Strasse, 63911 Klingenberg, Germany.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Evaluation of industrial cutting fluids using electrochemical impedance spectroscopy and multivariate data analysis2012In: 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)
    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.

  • 27.
    Ulrich, Christian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Sundgren, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Krantz-Rülcker, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Simultaneous estimation of soot and diesel contamination in engine oil using electrochemical impedance spectroscopy2007In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 127, no 2, p. 613-618Article in journal (Refereed)
    Abstract [en]

    In this paper, we explore the combination of electrochemical impedance spectroscopy and multivariate data analysis to simultaneously predict the concentrations of soot and diesel in engine oil. For this purpose, we use a well defined measurement set-up to minimize interference from ambient noise, and to obtain a large amount of data in a short period of time. An imperative requirement is that soot and diesel affect the impedance in different ways over the employed frequency range. It was, for example, found that diesel had a larger influence at lower frequencies. Using partial least squares modelling we show that it is possible to simultaneously predict the concentrations of both soot and diesel in engine oil. Since the temperature in an engine varies, the influence of the oil temperature is investigated in a preliminary experiment. This study is a part of the development of an electrochemical on-board sensor for real-time monitoring of engine oil.

  • 28.
    Uvdal, Kajsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Petoral, Rodrigo Jr
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Metal ion interaction with phosphorylated tyrosine analogue monolayers on gold2006In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 46, p. 23410-23416Article in journal (Refereed)
    Abstract [en]

    Phosphorylated tyrosine analogue molecules (pTyr-PT) were assembled onto gold substrates, and the resulting monolayers were used for metal ion interaction studies. The monolayers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection−absorption spectroscopy (IRAS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), both prior to and after exposure to metal ions. XPS verified the elemental composition of the molecular adsorbate and the presence of metal ions coordinated to the phosphate groups. Both the angle-dependent XPS and IRAS results were consistent with the change in the structural orientation of the pTyr-PT monolayer upon exposure to metal ions. The differential capacitance of the monolayers upon coordination of the metal ions was evaluated using EIS. These metal ions were found to significantly change the capacitance of the pTyr-PT monolayers in contrast to the nonphosphorylated tyrosine analogue (TPT). CV results showed reduced electrochemical blocking capabilities of the phosphorylated analogue monolayer when exposed to metal ions, supporting the change in the structure of the monolayer observed by XPS and IRAS. The largest change in the structure and interfacial capacitance was observed for aluminum ions, compared to calcium, magnesium, and chromium ions. This type of monolayer shows an excellent capability to coordinate metal ions and has a high potential for use as sensing layers in biochip applications to monitor the presence of metal ions.

  • 29.
    Valiokas, Ramunas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Östblom, Mattias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Shi, Jing
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry.
    Structural and kinetic properties of laterally stabilized, oligo(ethylene glycol)-containing alkylthiolates on gold: A modular approach2006In: Biointerphases, ISSN 1934-8630, E-ISSN 1559-4106, Vol. 1, no 1, p. 22-34Article in journal (Refereed)
    Abstract [en]

    The formation of highly ordered self-assembled monolayers (SAMs) on goldfrom an unusually long and linear compound HS(CH2)15CONH(CH2CH2O)6CH2CONH(CH2)15CH3 is investigated by contact angle goniometry, ex situ null ellipsometry, cyclic voltammetry and infrared reflection-absorption spectroscopy. The molecules are found to assemble in an upright position as a complete monolayer within 60 min. The overall structure of the SAM reaches equilibrium within 24 h as evidenced by infrared spectroscopy, although a slight improvement in water contact angles is observed over a period of a few weeks. The resulting SAM is 60 Å thick and it displays an advancing water contact angle of 112° and excellent electrochemicalblocking characteristics with typical current densities about 20 times lower as compared to those observed for HS(CH2)15CH3 SAMs. The dominating crystalline phases of the supporting HS(CH2)15 and terminal (CH2)15CH3 alkyl portions, as well as the sealed oligo(ethylene glycol) (OEG) “core,” appear as unusually sharp features in the infrared spectra at room temperature. For example, the splitting seen for the CH3 stretching and CH2 scissoring peaks is normally only observed for conformationally trapped alkylthiolate SAMs at low temperatures and for highly crystalline polymethylenes. Temperature-programmed infrared spectroscopy in ultrahigh vacuum reveals a significantly improved thermal stability of the SAM under investigation, as compared to two analogous OEG derivatives without the extended alkyl chain. Our study points out the advantages of adopting a “modular approach” in designing novel SAM-forming compounds with precisely positioned in plane stabilizing groups. We demonstrate also the potential of using the above set of compounds in the fabrication of “hydrogel-like” arrays with controlled wetting properties for application in the ever-growing fields of protein and cell analysis, as well as for bioanalytical applications.

1 - 29 of 29
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