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  • 151.
    Skedung, Lisa
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden.
    Ringstad, Lovisa
    YKI Institute for Surface Chemistry.
    Norin, Izabela
    ACO HUD Nordic AB.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden.
    Tactile friction of topical formulations2016Ingår i: Skin research and technology, ISSN 0909-752X, E-ISSN 1600-0846, Vol. 22, nr 1, s. 46-54Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: The tactile perception is essential for all types of topical formulations (cosmetic, pharmaceutical, medical device) and the possibility to predict the sensorial response by using instrumental methods instead of sensory testing would save time and cost at an early stage product development. Here, we report on an instrumental evaluation method using tactile friction measurements to estimate perceptual attributes of topical formulations. Methods: Friction was measured between an index finger and an artificial skin substrate after application of formulations using a force sensor. Both model formulations of liquid crystalline phase structures with significantly different tactile properties, as well as commercial pharmaceutical moisturizing creams being more tactile-similar, were investigated. Friction coefficients were calculated as the ratio of the friction force to the applied load. The structures of the model formulations and phase transitions as a result of water evaporation were identified using optical microscopy. Results: The friction device could distinguish friction coefficients between the phase structures, as well as the commercial creams after spreading and absorption into the substrate. In addition, phase transitions resulting in alterations in the feel of the formulations could be detected. A correlation was established between skin hydration and friction coefficient, where hydrated skin gave rise to higher friction. Also a link between skin smoothening and finger friction was established for the commercial moisturizing creams, although further investigations are needed to analyse this and correlations with other sensorial attributes in more detail. Conclusion: The present investigation shows that tactile friction measurements have potential as an alternative or complement in the evaluation of perception of topical formulations.

  • 152. Skedung, Lisa
    et al.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Arvidsson, M.
    Berglund, B
    Young, J. C.
    Stafford, C. M.
    Tribology, texture and touch2014Ingår i: 5th World Tribology Congress, WTC 2013, 2014, s. 2270-2273Konferensbidrag (Refereegranskat)
  • 153. Stenler, S.
    et al.
    Wiklander, O. P. B.
    Badal-Tejedor, M.
    Turunen, J.
    Nordin, J. Z.
    Hallengärd, D.
    Wahren, B.
    Andaloussi, S. E. L.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Smith, C. I. E.
    Lundin, K. E.
    Blomberg, P.
    Micro-minicircle gene therapy: Implications of size on fermentation, complexation, shearing resistance, and expression2014Ingår i: Molecular Therapy - Nucleic Acids, ISSN 2162-2531, Vol. 3, s. e140-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The minicircle (MC), composed of eukaryotic sequences only, is an interesting approach to increase the safety and efficiency of plasmid-based vectors for gene therapy. In this paper, we investigate micro-MC (miMC) vectors encoding small regulatory RNA. We use a construct encoding a splice-correcting U7 small nuclear RNA, which results in a vector of 650 base pairs (bp), as compared to a conventional 3600 bp plasmid carrying the same expression cassette. Furthermore, we construct miMCs of varying sizes carrying different number of these cassettes. This allows us to evaluate how size influences production, supercoiling, stability and efficiency of the vector. We characterize coiling morphology by atomic force microscopy and measure the resistance to shearing forces caused by an injector device, the Biojector. We compare the behavior of miMCs and plasmids in vitro using lipofection and electroporation, as well as in vivo in mice. We here show that when the size of the miMC is reduced, the formation of dimers and trimers increases. There seems to be a lower size limit for efficient expression. We demonstrate that miMCs are more robust than plasmids when exposed to shearing forces, and that they show extended expression in vivo.

  • 154. Stenler, Sofia
    et al.
    Wiklander, Oscar
    Tejedor, Maria Badal
    Hallengard, David
    Wahren, Britta
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Smith, C. I. Edvard
    Lundin, Karin E.
    Blomberg, Pontus
    On small minicircles: effect on coiling and function when approaching the sterical limits2012Ingår i: Human Gene Therapy, ISSN 1043-0342, E-ISSN 1557-7422, Vol. 23, nr 10, s. A144-A145Artikel i tidskrift (Övrigt vetenskapligt)
  • 155.
    Stiernstedt, Johanna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Brumer III, Harry
    KTH, Skolan för bioteknologi (BIO).
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO).
    Teeri, Tuula
    KTH, Skolan för bioteknologi (BIO).
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Friction between cellulose surfaces and the effect of and xyloglucan adsorption2006Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, nr 7, s. 2147-2153Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The forces and friction between cellulose spheres have been measured in the absence and presence of xyloglucan using an atomic force microscope. The forces between cellulose are monotonically repulsive with negligible adhesion after contact is achieved. The friction coefficient is observed to be unusually high in comparison with other nanotribological systems. We have confirmed that xyloglucan adsorbs strongly to cellulose, which results in a much stronger adhesion, which is dependent on the time the surfaces are in contact. Xyloglucan also increases the repulsion on approach of the cellulose surfaces, and the friction is markedly reduced. The apparently incompatible observations of decreased friction in combination with increased adhesion fulfills many of the necessary criteria for a papermaking additive.

  • 156.
    Stiernstedt, Johanna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Fröberg, J.C.
    Tiberg, F.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Forces between silica surfaces with adsorbed cationic surfactants:  Influence of salt and added non-ionic surfactant2005Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, nr 5, s. 1875-1883Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Forces have been measured between silica surfaces with adsorbed surfactants by means of a bimorph surface force apparatus. The surfactants used are the cationic surfactant tetradecyltrimethylammonium bromide (TTAB) and the nonionic surfactant hexakis(ethylene glycol) mono-n-tetradecyl ether (C14E6) as well as mixtures of these two surfactants. The measurements were made at elevated pH, and the effect of salt was studied. At high pH the glass surface is highly charged, which increases the adsorption of TTAB. Despite the low adsorption generally seen for nonionic surfactants on silica at high pH, addition Of C14E6 has a considerable effect on the surface forces between two glass surfaces in a TTAB solution. The barrier force is hardly affected, but the adhesion is reduced remarkably. Also, addition of salt decreases the adhesion, but increases the barrier force. In the presence of salt, addition Of C14E6 also increases the thickness of the adsorbed layer. The force barrier height is also shown to be related to literature values for surface pressure data in these systems.

  • 157.
    Stiernstedt, Johanna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Nordgren, Niklas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Brumer III, Harry
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Gray, Derek
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Friction and forces between cellulose model surfaces: A comparison2006Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 303, nr 1, s. 117-123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four different cellulose model surfaces, and one silica surface, have been studied by means of atomic force microscopy (AFM). The normal interactions have been found to consist of a longer range double layer force with a short range steric interaction, the nature of which is extensively discussed. Both the surface charge and range of the steric force depend on the type of cellulose substrate used, as does the magnitude of the adhesion. Studies of friction reveal that surface roughness is the determining factor for the friction coefficient, with which it increases monotonically. The absolute value, however, is determined by the surface chemistry. All studied cellulose surfaces show similar behavior in response to xyloglucan addition.

  • 158.
    Stiernstedt, Johanna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Rutland, M W
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Attard, P
    A novel technique for the in situ calibration and measurement of friction with the atomic force microscope (vol 76, pg 083710, 2005)2006Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, nr 1, artikel-id 019901Artikel i tidskrift (Refereegranskat)
  • 159.
    Stiernstedt, Johanna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Attard, P.
    A novel technique for the in situ calibration and measurement of friction with the atomic force microscope2005Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 76, nr 8, s. 083710-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     Presented here is a novel technique for the in situ calibration and measurement of friction with the atomic force microscope that can be applied simultaneously with the normal force measurement. The method exploits the fact that the cantilever sits at an angle of about 10 degrees to the horizontal, which causes the tip (or probe) to slide horizontally over the substrate as a normal force run is performed. This sliding gives rise to an axial friction force (in the axial direction of the cantilever), which is measured through the difference in the constant compliance slopes of the inward and outward traces. Traditionally, friction is measured through lateral scanning of the substrate, which is time consuming, and requires an ex situ calibration of both the torsional spring constant and the lateral sensitivity of the photodiode detector. The present method requires no calibration other than the normal spring constant and the vertical sensitivity of the detector, which is routinely done in the force analysis. The present protocol can also be applied to preexisting force curves, and, in addition, it provides the means to correct force data for cantilevers with large probes.

  • 160. Stubenrauch, C.
    et al.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Manev, E.
    Johansson, I.
    Pedersen, J. S.
    Langevin, D.
    Blunk, D.
    Bain, C. D.
    Mixtures of n-dodecyl-beta-D-maltoside and hexaoxyethylene dodecyl ether: Surface properties, bulk properties, foam films, and foams2010Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, nr 1-2, s. 5-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mixtures of the two non-ionic surfactants hexaoxyethylene dodecyl ether (C12E6) and n-dodecyl-beta-D-maltoside (beta-C(12)G(2)) were studied with regard to surface properties, bulk properties, foam films, and foams. The reason for studying a mixture of an ethylene oxide (CiEj) and a sugar (C(n)G(m),) based surfactant is that despite being non-ionic, these two surfactants behave quite differently. Firstly, the physico-chemical properties of aqueous solutions of C(n)G(m) surfactants are less temperature-sensitive than those of CiEj solutions. Secondly, the surface charge density q(0) of foam films stabilized by C(n)G(m) surfactants is pH insensitive down to the so-called isoelectric point, while that of foam films stabilized by CiEj surfactants changes linearly with the pH. The third difference is related to interaction forces between solid surfaces. Under equilibrium conditions very high forces are needed to expel beta-C(12)G(2) from between thiolated gold surfaces, while for C12E6 low loads are sufficient. Fourthly, the adsorption of C12E6 and beta-C(12)G(2) on hydrophilic silica and titania, respectively, is inverted. While the surface excess of C12E6 is large on silica and negligible on titania, beta-C(12)G(2) adsorbs very little on silica but has a large surface excess on titania. What is the reason for this different behaviour? Under similar conditions and for comparable head group sizes, it was found that the hydration of CiEj surfactants is one order of magnitude higher but on average much weaker than that of C(n)G(m) surfactants. Moreover, C(n)G(m) surfactants possess a rigid maltoside unit, while CiEj surfactants have a very flexible hydrophilic part. Indeed, most of the different properties mentioned above can be explained by the different hydration and the head group flexibilities. The intriguing question of how mixtures of CiEj and C(n)G(m) surfactants would behave arises organically. Thus various properties of C12E6 + beta-C(12)G(2) mixtures in aqueous solution have been studied with a focus on the 1:1 mixture. The results are compared with those of the single surfactants and are discussed accordingly.

  • 161. Svahn, Mathias G.
    et al.
    Hasan, Maroof
    Sigot, Valeria
    Valle-Delgado, Juan Jose
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Lundin, Karin E.
    Smith, C. I. Edvard
    Self-assembling supramolecular complexes by single-stranded extension from plasmid DNA2007Ingår i: Oligonucleotides, ISSN 1545-4576, Vol. 17, nr 1, s. 80-94Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-assembling supramolecular complexes are of great interest for bottom-up research like nanotechnology. DNA is an inexpensive building block with sequence-specific self-assembling capabilities through Watson-Crick and/or Hoogsteen base pairing and could be used for applications in surface chemistry, material science, nanomechanics, nanoelectronics, nanorobotics, and of course in biology. The starting point is usually single-stranded DNA, which is rather easily accessible for base pairing and duplex formation. When long stretches of double-stranded DNA are desirable, serving either as genetic codes or electrical wires, bacterial expansion of plasmids is an inexpensive approach with scale-up properties. Here, we present a method for using double-stranded DNA of any sequence for generating simple structures, such as junctions and DNA lattices. It is known that supercoiled plasmids are strand-invaded by certain DNA analogs. Here we add to the complexity by using Selfassembling UNiversal (SUN) anchors formed by DNA analog oligonucleotides, synthesized with an extension, a sticky-end that can be used for further base pairing with single-stranded DNA. We show here how the same set of SUN anchors can be utilized for gene therapy, plasmid purification, junction for lattices, and plasmid dimerization through Watson-Crick base pairing. Using atomic force microscopy, it has been possible to characterize and quantify individual components of such supra-molecular complexes.

  • 162. Sweeney, James
    et al.
    Hausen, Florian
    Hayes, Robert
    Webber, Grant B.
    Endres, Frank
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Bennewitz, Roland
    Atkin, Rob
    Control of Nanoscale Friction on Gold in an Ionic Liquid by a Potential-Dependent Ionic Lubricant Layer2012Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, nr 15, s. 155502-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The lubricating properties of an ionic liquid on gold surfaces can be controlled through application of an electric potential to the sliding contact. A nanotribology approach has been used to study the frictional behavior of 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate ([Py-1,Py-4]FAP) confined between silica colloid probes or sharp silica tips and a Au(111) substrate using atomic force microscopy. Friction forces vary with potential because the composition of a confined ion layer between the two surfaces changes from cation-enriched (at negative potentials) to anion-enriched (at positive potentials). This offers a new approach to tuning frictional forces reversibly at the molecular level without changing the substrates, employing a self-replenishing boundary lubricant of low vapor pressure.

  • 163. Sweeney, James
    et al.
    Webber, Grant B.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden, Sweden .
    Atkin, Rob
    Effect of ion structure on nanoscale friction in protic ionic liquids2014Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, nr 31, s. 16651-16658Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of ionic liquid (IL) molecular structure on nanoscale friction has been investigated using colloidal probe Friction Force Microscopy (FFM). The ILs studied were ethylammonium formate (EAF), ethylammonium nitrate (EAN), propylammonium formate (PAF), propylammonium nitrate (PAN), dimethylethylammonium formate (DMEAF), and ethanolammonium nitrate (EtAN). ILs were confined between a silica colloid probe and a mica surface, and the friction force was measured as a function of normal load for sliding velocities between 10 and 40 mu m s(-1). At low normal forces, multiple IL layers are found between the probe and the surface, but at higher force, in the boundary layer regime, a single ion layer separates the probe and the surface. In the boundary layer regime energy is dissipated by two main pathways. Firstly, the ionic liquid near the surface, with the exception of the boundary layer, is expelled from the advancing contact made by the probe on the surface. This disruption in the interactions between the boundary layer and the near surface multilayers, leads to energy dissipation and depends on the strength of the attraction between the boundary and near surface layers. The second pathway is via rotations and twists of ions in the boundary layer, primarily associated with the cation terminal methyl group. The friction coefficient did not vary over the limited range of sliding speeds investigated.

  • 164.
    Sörensen, Malin H.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi (stängd 20081231).
    Valle-Delgade, Juan J.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Corkery, Robert W.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Alberius, Peter C.
    AFM-Porosimetry: Density and pore volume measurements ofparticulate materials2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, s. 7024-7030Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduced the novel technique of AFM-porosimetry and applied it to measure the total pore volume of porous particles with a spherical geometry. The methodology is based on using an atomic force microscope as a balance to measure masses of individual particles. Several particles within the same batch were measured, and by plotting particle mass versus particle volume, the bulk density of the sample can be extracted from the slope of the linear fit. The pore volume is then calculated from the densities of the bulk and matrix materials, respectively. In contrast to nitrogen sorption and mercury porosimetry, this method is capable of measuring the total pore volume regardless of pore size distribution and pore connectivity. In this study, three porous samples were investigated by AFM-porosimetry: one ordered mesoporous sample and two disordered foam structures. All samples were based on a matrix of amorphous silica templated by a block copolymer, Pluronic F127, swollen to various degrees with poly(propylene glycol). In addition, the density of silica spheres without a template was measured by two independent techniques: AFM and the Archimedes principle.

  • 165.
    Tejedor, Maria Badal
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Nordgren, Niklas
    Schuleit, Michael
    Pazesh, Samaneh
    Alderborn, Göran
    Millqvist-Fureby, Anna
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    Determination of Interfacial Amorphicity in Functional Powders2017Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 4, s. 920-926Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nature of the surfaces of particles of pharmaceutical ingredients, food powders, and polymers is a determining factor for their performance in for example tableting, powder handling, or mixing. Changes on the surface structure of the material will impact the flow properties, dissolution rate, and tabletability of the 2 powder blend. For crystalline materials, surface amorphization is a phenomenon which is known to impact performance. Since it is important to measure and control the level of amorphicity, several characterization techniques are available to determine the bulk amorphous content of a processed material. The possibility of characterizing the degree of amorphicity at the surface, for example by studying the mechanical properties of the particles' surface at the nanoscale, is currently only offered by atomic force microscopy (AFM). The AFM PeakForce QNM technique has been used to measure the variation in energy dissipation (eV) at the surface of the particles which sheds light on the mechanical changes occurring as a result of amorphization or recrystallization events. Two novel approaches for the characterization of amorphicity are presented here. First, since particles are heterogeneous, we present a methodology to present the results of extensive QNM analysis of multiple particles in a coherent and easily interpreted manner, by studying cumulative distributions of dissipation data with respect to a threshold value which can be used to distinguish the crystalline and amorphous states. To exemplify the approach, which is generally applicable to any material, reference materials of purely crystalline alpha-lactose monohydrate and completely amorphous spray dried lactose particles were compared to a partially amorphized alpha-lactose monohydrate sample. Dissipation data are compared to evaluations of the lactose samples with conventional AFM and SEM showing significant topographical differences. Finally, the recrystallization of the surface amorphous regions in response to humidity was followed by studying the dissipation response of a well-defined surface region over time, which confirms both that dissipation measurement is a useful measure of surface amorphicity and that significant recrystallization occurs at the surface in response to humidity.

  • 166.
    Theander, Katarina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pugh, R. J.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Forces and Friction Between Hydrophilic and Hydrophobic Surfaces: Influence of Oleate Species2007Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 313, nr 2, s. 735-746Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     The atomic force microscope has been used to investigate normal surface forces and lateral friction forces at different concentrations of sodium oleate, a frequently used fatty acid in the deinking process. The measurements have been performed using the colloidal probe technique with bead materials consisting of cellulose and silica. Cellulose was used together with a printing ink alkyd resin and mica, whereas silica was used with a hydrophobized silica wafer. The cellulose-alkyd resin system showed stronger double layer repulsion and the friction was reduced with increasing surfactant concentration. The adhesive interaction disappeared immediately on addition of sodium oleate. The normal Surface forces for cellulose-mica indicated no apparent adsorption of the sodium oleate however, the friction coefficient increased on addition of sodium oleate, which we ascribe to some limited adsorption increasing the effective surface roughness. The silica-hydrophobic silica system showed a completely different surface force behavior at the different concentrations. An attractive hydrophobic interaction was evident since the surfaces jumped into adhesive contact at a longer distance than the van der Waals forces would predict. The strong adhesion was reflected in the friction forces as a nonlinear relationship between load and friction and a large friction response at zero applied load. Indirect evidence of adsorption to the hydrophilic silica surface was also observed in this case, and QCM studies were performed to confirm the adsorption of material to both surfaces.

  • 167.
    Theander, Katarina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pugh, R. J.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Friction force measurements relevant to de-inking by means of atomic force microscope2005Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 291, nr 2, s. 361-368Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the pulping step of the de-inking process, the ink detaches from the fibers due to shear and physical chemical interaction. In order to get a better understanding of the forces involved between cellulose and ink, the atomic force microscope and the colloidal probe technique have been used in the presence of a model chemical dispersant (hexa-ethyleneglycol mono n-dodecyl ether, C 12E6). A cellulose bead was used as the colloidal probe and three different lower surfaces have been used, an alkyd resin, mica and a cellulose sphere. The normal and lateral forces have been measured at a range of nonionic concentrations. It was found that the lateral sliding friction forces deceased with increasing surfactant concentration for both the alkyd resin and mica while no differences were observed for the cellulose surface. In addition, only a very small change in normal force could be detected for the alkyd surface as the concentration changed.

  • 168.
    Thormann, Esben
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Mizuno, Hiroyasu
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Jansson, Kjell
    Stockholm Univ, Stockholm, Sweden.
    Hedin, Niklas
    Stockholm Univ, Stockholm, Sweden.
    Soledad Fernandez, M.
    Univ Chile, Santiago, Chile.
    Luis Arias, Jose
    Univ Chile, Santiago, Chile.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pai, Ranjith Krishna
    Stockholm Univ, Stockholm, Sweden.
    Bergström, Lennart
    Stockholm Univ, Stockholm, Sweden.
    Embedded proteins and sacrificial bonds provide the strong adhesive properties of gastroliths2012Ingår i: Nanoscale, ISSN 2040-3364, Vol. 4, nr 13, s. 3910-3916Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adhesive properties of gastroliths from a freshwater crayfish (Cherax quadricarinatus) were quantified by colloidal probe atomic force microscopy (AFM) between heavily demineralized gastrolith microparticles and gastrolith substrates of different composition. Combined AFM and transmission electron microscopy studies demonstrated that the sequential detachment and large adhesion energies that characterise the adhesive behaviour of a native gastrolith substrate are dominated by sacrificial bonds between chitin fibres and between chitin fibres and CaCO3. The sacrificial bonds were shown to be strongly related to the gastrolith proteins and when the majority of these proteins were removed by ethylenediaminetetraacetic acid (EDTA), the sequential detachment disappeared and the adhesive energy was reduced by more than two orders of magnitude.

  • 169.
    Tyrode, Eric
    et al.
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Johnson, C M
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Kumpulainen, A
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Rutland, Mark W.
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Claesson, Per M.
    KTH, Tidigare Institutioner (före 2005), Kemi.
    Hydration state of non-ionic surfactant monolayers at the liquid/vapor interface: Structure determination by vibrational sum frequency spectroscopy (VSFS)2005Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 230, s. U2904-U2905Artikel i tidskrift (Övrigt vetenskapligt)
  • 170.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Johnson, C. Magnus
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Rutland, Mark W.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    COLL 153-Molecular ordering at the liquid/air interface and hydration of surfactants2006Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 232Artikel i tidskrift (Övrigt vetenskapligt)
  • 171.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Claes Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Rutland, Mark W
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per M
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Structure and hydration of poly(ethylene oxide) surfactants at the air/liquid interface. A vibrational sum frequency spectroscopy study2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 31, s. 11642-11652Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorption layers of penta(ethylene oxide) n-dodecyl ether (C12E5) at the air/liquid interface have been studied using the surface-sensitive technique vibrational sum frequency spectroscopy (VSFS). The CH and COC stretching vibrations of the surfactant molecule, as well as the OH stretching vibrations of the surface water molecules, have been targeted to obtain a comprehensive picture of the adsorption process. The concentration range studied comprises different adsorption regimes, starting from the neat water surface until attaining the saturated liquid expanded monolayer when approaching the critical micellar concentration (cmc). The surfactant molecules were found to first adsorb to the air-liquid interface with their hydrocarbon tails preferentially orientated close to the surface plane, surrounded by patches of unperturbed surface water. These patches were only seen to disappear at areas per molecule close to 65 A(2), coinciding with a sudden change in the orientation of the surfactant alkyl chains, which adopted a more upright configuration. Nonetheless, gauche defects in the hydrocarbon tails were observed along the whole concentration range, even above the cmc. Moreover, the poly(ethylene oxide) headgroup was seen to induce a significant structuring of the water molecules in direct proximity to the surfactant monolayer, despite being themselves substantially disordered. Comparison of the hydration fingerprint region is made with another non-ionic surfactant with a sugar-based headgroup. The temperature effect in the VSFS spectra of C12E4 and C12E8 solutions has also been considered, and the results are discussed in terms of the different models proposed to explain the peculiar temperature dependence of ethylene oxide-based surfactants and polymers in water.

  • 172.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Baldelli, Steve
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    A vibrational sum frequency spectroscopy study of the liquid-gas interface of acetic acid-water mixtures: 2: orientation analysis2005Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, nr 1, s. 329-341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrational sum frequency spectroscopy has been used to investigate the surface of aqueous acetic acid solutions. By studying the methyl and carbonyl vibrations with different polarization combinations, an orientation analysis of the acetic acid molecules has been performed in the concentration range 0-100%. The surface tension of acetic acid solutions was also measured in order to obtain the surface concentration. The orientation of the interfacial acetic acid molecules was found to remain essentially constant in an upright position with the methyl group directed toward the gas phase in the whole concentration range. The tilt angle (theta(CH3)) of the symmetry axis of the methyl group with respect to the surface normal was found to be lower than 15degrees when considering a delta distribution of angles or as narrow as 0 +/- 11degrees when assuming a Gaussian distribution. Further investigations showed that the C=O bond tilt (theta(C=O)) of the acetic acid hydrated monomer was constant and close to 55degrees in the concentration range where it was detected. Finally, the orientation information is discussed in terms of different species of acetic acid, where the formation of a surface layer of acetic acid cyclic dimers is proposed at high acid concentrations.

  • 173.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Kumpulainen, Atte
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Hydration State of Non-ionic Surfactant Monolayers at the Liquid/Vapor Interface:  Structure Determination by Vibrational Sum Frequency Spectroscopy2005Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, nr 48, s. 16848-16859Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The OH stretching region of water molecules in the vicinity of nonionic surfactant monolayers has been investigated using vibrational sum frequency spectroscopy (VSFS) under the polarization combinations ssp, ppp, and sps. The surface sensitivity of the VSFS technique has allowed targeting the few water molecules present at the surface with a net orientation and, in particular, the hydration shell around alcohol, sugar, and poly(ethylene oxide) headgroups. Dramatic differences in the hydration shell of the uncharged headgroups were observed, both in comparison to each another and in comparison to the pure water surface. The water molecules around the rigid glucoside and maltoside sugar rings were found to form strong hydrogen bonds, similar to those observed in tetrahedrally coordinated water in ice. In the case of the poly(ethylene oxide) surfactant monolayer a significant ordering of both strongly and weakly hydrogen bonded water was observed. Moreover, a band common to all the surfactants studied, clearly detected at relatively high frequencies in the polarization combinations ppp and sps, was assigned to water species located in proximity to the surfactant hydrocarbon tail phase, with both hydrogen atoms free from hydrogen bonds. An orientational analysis provided additional information on the water species responsible for this band.

  • 174.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Day, James P. R.
    Bain, Colin D.
    A study of the adsorption of ammonium perfluorononanoate at the air-liquid interface by vibrational sum-frequency spectroscopy2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 1, s. 316-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     Vibrational sum frequency spectroscopy (VSFS) has been used to study the adsorption of ammonium perfluorononanoate (APFN) at the air-liquid interface, specifically targeting the C-F and carboxylate stretches. In the spectral region extending from 1050 to 1850 cm(-1), three major peaks situated at 1369, 1408, and similar to 1665 cm(-1) were detected under the polarization combinations ssp, ppp, and sps. The first of these peaks was assigned to CF3 stretching vibrations after a detailed comparison with other surfactant molecules with different degrees of fluorination, while the last two resonant features were assigned to symmetric and antisymmetric carboxylate stretching vibrations. From the combined analysis of the VSFS, ellipsometry, and previous FTIR measurements, a consistent physical model for the adsorption of APFN to the liquid surface is proposed. At low surface coverages the APFN molecules lie essentially flat on the surface. At concentrations from 1 mM to the critical micellar concentration (molecular areas < 70 angstrom(2)) the mean orientation of both the surfactant head group and terminal CF3 group remained constant. The formation of surface micelles at higher concentrations is consistent with the experimental data.

  • 175.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Niga, Petru
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Molecular Structure upon Compression and Stability toward Oxidation of Langmuir Films of Unsaturated Fatty Acids: A Vibrational Sum Frequency Spectroscopy Study2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 17, s. 14024-14031Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrational sum frequency spectroscopy (VSFS) has been used to determine the stability toward oxidation in air of a series of unsaturated fatty acids, measuring as a function of time the changes in the chemical structure and conformational order of films spread on a Langmuir trough. The fatty acids studied consisted of a 20-carbon backbone with increasing numbers of cis double bonds in the chain: 11c-eicosenoic acid (20:1 EA, omega-9), 11c,14c-eicosadienoic acid (20:2 EA, omega-6), and 11c, 14c, 17c-eicosatrienoic acid (20:3 EA, omega-3). Measurements at constant surface pressure show that double bonds are lost from the surface region and that drops in intensity of the vinyl CH stretch are detectable within a few minutes of spreading the monolayer. The results are consistent with the fatty acid peroxidation free radical mechanism. The sum frequency spectra also reveal that what remains on the surface is conformationally more disordered with a larger number of gauche defects. The oxidation kinetics are found to be strongly dependent on the packing density of the monolayer, being more stable at higher pressures. Oxidation can be avoided by purging the system in an inert atmosphere. Finally, the molecular structure upon compression was tracked in unoxidized monolayers. The results suggest that the packing and orientation of the double bond sections of all three unsaturated fatty acids show remarkable similarities, with the direction of the double bonds approximately parallel to each other irrespective of the number of unsaturations in the chain, with the 20:3 EA probably forming "iron-angle" structures. The possibility of unsaturated chains in a "hairpin" configuration is discarded for area per molecules smaller than similar to 50 angstrom(2), which corresponds to the lowest surface pressure measured with VSFS.

  • 176.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Niga, Petru
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Molecular Structure upon Compression and Stability towards Oxidation of Langmuir Films of Unsaturated Fatty Acids: a Vibrational Sum Frequency Spectroscopy StudyArtikel i tidskrift (Övrigt vetenskapligt)
  • 177.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Bain, Colin D.
    Dep. of Chemistry, Durham University, UK.
    Adsorption of CTAB on Hydrophilic Silica Studied by Linear and Nonlinear Optical Spectroscopy2008Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, nr 51, s. 17434-17445Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrational sum-frequency spectroscopy (SFS) and total internal reflection Raman scattering (TIR Raman) have been used to study the adsorption of hexadecyltrimethylammonium bromide (CTAB) to hydrophilic silica. These two complementary techniques permit the determination of the adsorbed amount with a sensitivity of similar to 1% of the maximum surface coverage, changes in the average tilt of the adsorbed molecules, the presence of asymmetric aggregates in the adsorbed film, and the structure and orientation of the water molecules in the interfacial region. The TIR Raman spectra show a monotonic increase with CTAB concentration with no measurable changes in the relative intensities of the different polarization combinations probed, implying that no significant changes occur in the conformational order of the hydrocarbon chain. In the sum-frequency (SF) spectra, no detectable peaks from the surfactant headgroup and hydrophobic chain were observed at any surface coverage. Major changes are observed in the water bands of the SF spectra, as the originally negatively charged silica surface becomes positively charged with an increase in the adsorbed amount, inducing a change in the polar orientation of the water molecules near the surface. The detection limits for hydrocarbons chains in the SF spectra were estimated by comparison with the SF spectrum of a disordered octadecyltrichlorosilane monolayer. The simulations demonstrate that the asymmetry in the adsorbed CTAB layer at any concentration is less than 5% of a monolayer. The results obtained pose severe constraints on the possible structural models, in particular at concentrations below the critical micellar concentration where information is scarce. The formation of hemimicelles, monolayers and other asymmetric aggregates is ruled out, with centrosymmetric aggregates forming from early on in the adsorption process.

  • 178. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, A.
    Rutland, Mark W
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Adhesion forces between protein layers studied by means of atomic force microscopy2006Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 11, s. 5108-5114Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adhesion forces between different protein layers adsorbed on different substrates in aqueous media have been measured by means of an atomic force microscope using the colloid probe technique. The effects of the loading force, the salt concentration and pH of the medium, and the electrolyte type on the strength, the pull-off distance, and the separation energy of such adhesion forces have been analyzed in depth. Two very different proteins (bovine serum albumin and apoferritin) and two dissimilar substrates (silica and polystyrene) were used in the experiments. The results clearly point out a very important contribution of the electrostatic interactions in the adhesion between protein layers.

  • 179. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, A.
    Rutland, Mark W
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Existence of hydration forces in the interaction between apoferritin molecules adsorbed on silica surfaces2005Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, nr 21, s. 9544-9554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The atomic force microscope, together with the colloid probe technique, has become a very useful instrument to measure interaction forces between two surfaces. Its potential has been exploited in this work to study the interaction between protein (apoferritin) layers adsorbed on silica surfaces and to analyze the effect of the medium conditions (pH, salt concentration, salt type) on such interactions. It has been observed that the interaction at low salt concentrations is dominated by electrical double layer (at large distances) and steric forces (at short distances), the latter being due to compression of the protein layers. The DLVO theory fits these experimental data quite well. However, a non-DLVO repulsive interaction, prior to contact of the protein layers, is observed at high salt concentration above the isoelectric point of the protein. This behavior could be explained if the presence of hydration forces in the system is assumed. The inclusion of a hydration term in the DLVO theory (extended DLVO theory) gives rise to a better agreement between the theoretical fits and the experimental results. These results seem to suggest that the hydration forces play a very important role in the stability of the proteins in the physiological media.

  • 180. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, A.
    Rutland, Mark W
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Hydration forces between silica surfaces: Experimental data and predictions from different theories2005Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 123, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Silica is a very interesting system that has been thoroughly studied in the last decades. One of the most outstanding characteristics of silica suspensions is their stability in solutions at high salt concentrations. In addition to that, measurements of direct-interaction forces between silica surfaces, obtained by different authors by means of surface force apparatus or atomic force microscope (AFM), reveal the existence of a strong repulsive interaction at short distances (below 2 nm) that decays exponentially. These results cannot be explained in terms of the classical Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory, which only considers two types of forces: the electrical double-layer repulsion and the London-van der Waals attraction. Although there is a controversy about the origin of the short-range repulsive force, the existence of a structured layer of water molecules at the silica surface is the most accepted explanation for it. The overlap of structured water layers of different surfaces leads to repulsive forces, which are known as hydration forces. This assumption is based on the very hydrophilic nature of silica. Different theories have been developed in order to reproduce the exponentially decaying behavior (as a function of the separation distance) of the hydration forces. Different mechanisms for the formation of the structured water layer around the silica surfaces are considered by each theory. By the aid of an AFM and the colloid probe technique, the interaction forces between silica surfaces have been measured directly at different pH values and salt concentrations. The results confirm the presence of the short-range repulsion at any experimental condition (even at high salt concentration). A comparison between the experimental data and theoretical fits obtained from different theories has been performed in order to elucidate the nature of this non-DLVO repulsive force.

  • 181. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, Adam
    KTH, Tidigare Institutioner, Kemi.
    Rutland, Mark W
    KTH, Tidigare Institutioner, Kemi.
    Interaction forces between BSA layers adsorbed on silica surfaces measured with an atomic force microscope2004Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, nr 17, s. 5365-5371Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interaction forces between bovine serum albumin (BSA) layers adsorbed on silica surfaces have been measured using an atomic force microscope (AFM) in Conjunction with the colloid probe technique. Measurements of force-distance curves were made at different pH values and electrolyte concentrations (NaCl and CaCl2). The interaction at long range is dominated by electrical double-layer forces, while at short surface separations an additional repulsion due to the compression of the adsorbed protein layers appears. However, prior to this steric interaction, when the pH is above the isoelectric point of the protein and at high salt concentration, a non-DLVO repulsive interaction is observed. This behavior is explained if the presence of hydration forces in the system is assumed. Theoretical predictions including a hydration term in the DLVO theory fit the experimental results satisfactorily. The results presented in this article provide a direct confirmation that the AFM colloid probe technique can provide a useful way of directly quantifying the interaction of biological macromolecules.

  • 182. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, Adam
    KTH, Tidigare Institutioner, Kemi.
    Rutland, Mark W.
    KTH, Tidigare Institutioner, Kemi.
    Interactions between bovine serum albumin layers adsorbed on different substrates measured with an atomic force microscope2004Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 6, nr 7, s. 1482-1486Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By the aid of an atomic force microscope (AFM) and the colloid probe technique, the interaction forces between bovine serum albumin (BSA) layers adsorbed on different substrates (silica and polystyrene) have been measured directly as a function of pH and salt concentration. Electrostatic and steric forces dominate the interactions at low salt concentrations. At high salt concentrations, when electrostatic interactions are screened, a very strange behaviour is found as a function of pH. The behaviour around the i.e.p. of the protein is also very striking: the interaction is attractive at low salt concentration, but it is repulsive at high salt concentration. These results could be explained if the presence of hydration forces is assumed. Theoretical predictions including a hydration term in the DLVO theory fit the experimental results satisfactorily.

  • 183. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, Adam
    KTH, Tidigare Institutioner, Kemi.
    Rutland, Mark W
    KTH, Tidigare Institutioner, Kemi.
    Measurement of interactions between protein layers adsorbed on silica by atomic force microscopy2004Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 16, nr 26, s. S2383-S2392Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work, using an atomic force microscope and the colloid probe technique, investigates the interaction forces between bovine serum albumin (BSA) layers and between apoferritin layers adsorbed on silica surfaces. The measurements have been carried out in an aqueous medium at different pH values and NaCl concentrations. Similar behaviours have been found with both proteins. Electrostatic and steric forces dominate the interactions between the protein layers at low NaCl concentrations. However, a very strange behaviour is found as a function of pH at high NaCl concentrations. The results obtained under these conditions could be explained if the presence of hydration forces in these systems is assumed.

  • 184. Veeregowda, Deepak H.
    et al.
    van der Mei, Henny C.
    de Vries, Joop
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Valle-Delgado, Juan J.
    Sharma, Prashant K.
    Busscher, Henk J.
    Boundary lubrication by brushed salivary conditioning films and their degree of glycosylation2012Ingår i: Clinical Oral Investigations, ISSN 1432-6981, E-ISSN 1436-3771, Vol. 16, nr 5, s. 1499-1506Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Toothbrushing, though aimed at biofilm removal, also affects the lubricative function of adsorbed salivary conditioning films (SCFs). Different modes of brushing (manual, powered, rotary-oscillatory or sonically driven) influence the SCF in different ways. Our objectives were to compare boundary lubrication of SCFs after different modes of brushing and to explain their lubrication on the basis of their roughness, dehydrated layer thickness, and degree of glycosylation. A pilot study was performed to relate in vitro lubrication with mouthfeel in human volunteers. Coefficient of friction (COF) on 16-h-old SCFs after manual, rotary-oscillatory, and sonically driven brushing was measured using colloidal probe atomic force microscopy (AFM). AFM was also used to assess the roughness of SCFs prior to and after brushing. Dehydrated layer thicknesses and glycosylation of the SCFs were determined using X-ray photoelectron spectroscopy. Mouthfeel after manual and both modes of powered brushing were evaluated employing a split-mouth design. Compared with unbrushed and manually or sonically driven brushed SCFs, powered rotary-oscillatory brushing leads to deglycosylation of the SCF, loss of thickness, and a rougher film. Concurrently, the COF of a powered rotary-oscillatory brushed SCF increased. Volunteers reported a slightly preferred mouthfeel after sonic brushing as compared to powered rotating-oscillating brushing. Deglycosylation and roughness increase the COF on SCFs. Powered rotary-oscillatory brushing can deglycosylate a SCF, leading to a rougher film surface as compared with manual and sonic brushing, decreasing the lubricative function of the SCF. This is consistent with clinical mouthfeel evaluation after different modes of brushing.

  • 185.
    Wakeham, Deborah
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Crivoi, Dana G.
    Medina, Francesc
    Segarra, Anna M.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden.
    In-situ study of substrate - catalyst interactions in a Julia-Colonna epoxidation using quartz crystal microbalance with dissipation2016Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 469, s. 263-268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quartz crystal microbalance with dissipation (QCM-D) analysis of the hexa-L-Leucine (PLL)-catalyzed epoxidation of chalcone gives in-situ experimental evidences which demonstrate that the reaction proceeds mainly via the formation of a PLL-bound hydroperoxide complex followed by the reversible addition of chalcone. The observations offer an alternative rationalization for the viability of the preferred catalytic pathway.

  • 186. Wakeham, Deborah
    et al.
    Niga, Petru
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ridings, Christiaan
    Andersson, Gunther
    Nelson, Andrew
    Warr, Gregory G.
    Baldelli, Steven
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Atkin, Rob
    Surface structure of a "non-amphiphilic" protic ionic liquid2012Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, nr 15, s. 5106-5114Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nanostructure of the ethanolammonium nitrate (EtAN)-air surface has been investigated using X-ray reflectometry (XRR), vibrational sum frequency spectroscopy (VSFS) and neutral impact collision ion scattering spectroscopy (NICISS). The XRR data decays more rapidly than expected for a perfectly sharp interface, indicating a diffuse electron (scattering length) density profile. Modelling of the XRR data using three different fitting routines produced consistent interfacial profiles that suggest the formation of interfacial EtAN clusters. Consistent with this, VSFS reveals that the EtAN surface is predominantly covered by -CH2- moieties, with the -NH3+ and -OH groups of the cation buried slightly deeper in the interface. The elemental profiles determined using NICISS also show enrichment of carbon relative to nitrogen and oxygen in the outermost surface layer, which is consistent with the surface cation orientation deduced from VSFS, and with the presence of EtAN aggregates at the liquid surface.

  • 187. Wakeham, Deborah
    et al.
    Niga, Petru
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Warr, Gregory G.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Atkin, Rob
    Nonionic Surfactant Adsorption at the Ethylammonium Nitrate Surface: A Neutron Reflectivity and Vibrational Sum Frequency Spectroscopy Study2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorbed layers of polyoxyethylene n-alkyl ether surfactants C12E4, C14E4, and C16E4 at the LEAN surface have a headgroup layer that is thin and compact (only similar to 30 vol % EAN). The headgroups do not adopt a preferred orientation and are disordered within the ethylene oxide layer. Alkyl tails contain a significant number of gauche defects indicating a high degree of conformational disorder. The thickness of the tail layer increases with increasing alkyl chain length, while the headgroup layer shows little change. Lowering the C12E4 concentration from 1 to 0.1 wt % decreases the adsorbed amount, and the headgroup layer becomes thinner and less solvated, whereas C14E4 and C16E4 adsorbed layers are unaffected by dilution over the same concentration range. The C16E4 layer thickness increases and area per molecule decreases on warming to 60 degrees C, but the adsorbed layer structures of C12E4 and C14E4 are unchanged. Both effects are attributed to surfactant solubility.

  • 188. Werzer, Oliver
    et al.
    Cranston, Emily D.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Warr, Gregory G.
    Atkin, Rob
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ionic liquid nanotribology: mica-silica interactions in ethylammonium nitrate2012Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, nr 15, s. 5147-5152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Colloid probe atomic force microscopy has been used to study the nanotribological properties of the silica-ethylammonium nitrate (EAN)-mica system. Normal force curve measurements reveal a series of steps at separations that are consistent with the size of an EAN ion pair (0.5 nm) due to displacement of structured solvent layers as the two surfaces are brought together. At closest separations, two steps are measured with widths of 0.3 nm and 0.1 nm, which are too small to be due to an ion pair layer. The 0.3 nm step is attributed to a partial displacement of a silica-bound cation-rich layer, with residual cations being removed in the subsequent 0.1 nm step. Lateral force measurements reveal that the frictional response is dependent on the number of ion pair layers between the surfaces. At low forces, when there is more than a single layer of EAN between silica and mica, the lateral force increases relatively steeply with applied load, and is independent of the sliding speed. At intermediate forces, a single layer of cations in an intercalated bilayer structure is present between the surfaces. The friction coefficient (mu) increases logarithmically with sliding speed consistent with an activated, discontinuous sliding process. At high force, m is small and once again, independent of sliding velocity. The adsorbed cation layer is bound primarily to mica and compressed by the high normal force. This robust layering with a well-defined sliding plane permits the colloid probe to slide easily over the mica surface.

  • 189.
    Zhou, Qi
    et al.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Rutland, Mark W
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Teeri, Tuula T.
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Xyloglucan in cellulose modification2007Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 14, nr 6, s. 625-641Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Xyloglucans are the principal polysaccharides coating and crosslinking cellulose microfibrills in the majority of land plants. This review summarizes current knowledge of xyloglucan structures, solution properties, and the mechanism of interaction of xyloglucans with cellulose. This knowledge base forms the platform for new biomimetic methods of cellulose surface modification with applications within the fields of textile manufacture, papermaking, and materials science. Recent advances using the enzyme xyloglucan endo-transglycosylase (XET, EC 2.4.1.207) to introduce varied chemical functionality onto cellulose surfaces are highlighted.

  • 190.
    Álvarez Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Bettini, Eleonora
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden, Sweden .
    Friction Coefficient Mapping (FCM) and Contact Adhesion Mapping (CAM): Surface Microstructure and Function2013Ingår i: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, s. 3120-3121Konferensbidrag (Refereegranskat)
  • 191.
    Álvarez Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Cranston, Emily
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wakeham, Deborah
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Niga, Petru
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Werzer, O.
    Sweeney, J.
    Hausen, F.
    Hayes, R.
    Webber, G. B.
    Endres, F.
    Bennewitz, R.
    Hjalmarsson, Nicklas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Glavatskih, Sergei
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
    Atkin, R.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Nanotribology: Tribotronics, ionic liquids and control of surface interactions2013Ingår i: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, s. 3106-3108Konferensbidrag (Refereegranskat)
    Abstract [en]

    The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation between the number of ion pairs trapped in the tribological contact and the friction coefficient displayed. The second is the fact that the surface electrical potential can be used to control the composition of the boundary layer and thus tune the friction. Thirdly, the interfacial ordering appears to significantly affect the fluid dynamics over large distances.

  • 192.
    Álvarez Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sababi, Majid
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Ejnermark, Sebastian
    Ekman, Lars
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden, Sweden.
    Role of microstructure on corrosion initiation of an experimental tool alloy: A Quantitative Nanomechanical Property Mapping study2014Ingår i: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 89, s. 236-241Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adhesion properties of a FeCrVN experimental tool alloy immersed in pure water and sodium chloride solution have been studied by Quantitative Nanomechanical Property Mapping to understand the influence of microstructure on corrosion initiation of this alloy. The approach used here allows early observation and identification of pre-pitting events that may lead to passivity breakdown of the alloy. Adhesion provides a good distinction between the different regions and we ascribe this to their vanadium and nitrogen contents. Finally, the prepitting is characterized by generation of small particles in specific regions of the surface with low chromium content.

  • 193.
    Álvarez-Asencio, Rubén
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Institute for Advanced Studies, IMDEA Nanoscience, C/Faraday 9, Spain.
    Wallqvist, V.
    Kjellin, M.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, Sweden.
    Camacho, A.
    Nordgren, N.
    Luengo, G. S.
    Nanomechanical properties of human skin and introduction of a novel hair indenter2016Ingår i: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 54, s. 185-193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.

1234 151 - 193 av 193
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