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Liang H.,Chongqing University | Liang H.,University of Helsinki | Miranto H.,University of Helsinki | Miranto H.,BioNavis Ltd | And 6 more authors.
Sensors and Actuators, B: Chemical

A surface plasmon resonance (SPR) setup in Kretschmann configuration is being utilized as a refractometer for both liquids as well as ultrathin films. The SPR signal detection technology used is based on a goniometer approach providing a wide angular scan range which facilitates highly accurate liquid and gas phase measurements. Attention was paid to improve sample handling and preparation. In order to avoid cross-contamination between measurements an easily removable and exchangeable molded PDMS flow cell was used during the measurements. By careful choice of components for liquid handling the dead volume of the system could be reduced down to some microliters. The angular change and thus the refractive index for sucrose, ethylene glycol (EG) and ethanol solutions with different concentrations, the thickness and refractive index of deposited Langmuir-Blodgett (LB) films, and the interaction kinetics between a biotin containing self-assembled monolayer (SAM) and streptavidin were determined. The measured refractive indices of sucrose, EG and ethanol solutions corresponded well with literature values. LB films were characterized by measuring the complete SPR curve in an angular scan range from 40 to 78°. A two-color SPR approach combined with two-media measurements was successfully employed for simultaneous and unambiguous determination of both refractive index and thickness of stearic acid monolayers. The thickness obtained for the stearic acid monolayer was 2.66 nm, and the refractive indices at 635 and 670 nm were 1.5800 and 1.4138, respectively. The developed sensor-plate holder enabled functionalization of the SPR gold chip outside the instrument, therefore making the sample handling more flexible. The affinity constant obtained for the streptavidin-biotin interaction was 1.01 × 10-8 M. The total angle SPR method used in this study clearly shows its potential to be used as a refractometer for both liquids and ultrathin films, as well as for traditional liquid phase biomolecular kinetic studies. © 2010 Elsevier B.V. All rights reserved. Source

Barzyk W.,Polish Academy of Sciences | Vuorinen J.,Biolin Scientific
Colloids and Surfaces A: Physicochemical and Engineering Aspects

This paper describes the measuring procedure which enables overcoming the base difficulty in application of the vibrating plate (VP) technique to measuring electric surface potential (ΔV) of free solution surfaces, namely loosing the zero level set for the reference sample (water) while replacing it with the solution measured. (The ΔV measurement is performed by comparing two measurements in series, i.e., for the pure interface and that containing a surface film.) Main improvement in the measuring procedure is achieved by (i) applying a flow for exchanging the reference sample with the measured solution and (ii) elimination of an error driven by dependency of the measuring signal on the air gap width. The air gap width is fixed by contact of the bottom edge of a platinum Wilhelmy plate with the solution surface which the plate is simultaneously used for measurement of the surface pressure (Π). The results received with the new methodology for n-decanoic acid, n-decyl-trimethylammonium bromide (C10TABr) and sodium n-dodecyl sulphate (SLS) are discussed. © 2011 Elsevier B.V. Source

Wayment-Steele H.K.,Pomona College | Johnson L.E.,Pomona College | Johnson L.E.,University of Washington | Tian F.,University of San Diego | And 3 more authors.
ACS Applied Materials and Interfaces

Understanding the kinetics of dye adsorption and desorption on semiconductors is crucial for optimizing the performance of dye-sensitized solar cells (DSSCs). Quartz crystal microbalance with dissipation monitoring (QCM-D) measures adsorbed mass in real time, allowing determination of binding kinetics. In this work, we characterize adsorption of the common RuBipy dye N3 to the native oxide layer of a planar, sputter-coated titanium surface, simulating the TiO2 substrate of a DSSC. We report adsorption equilibrium constants consistent with prior optical measurements of N3 adsorption. Dye binding and surface integrity were also verified by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS). We further study desorption of the dye from the native oxide layer on the QCM sensors using tetrabutylammonium hydroxide (TBAOH), a commonly used industrial desorbant. We find that using TBAOH as a desorbant does not fully regenerate the surface, though little ruthenium or nitrogen is observed by XPS after desorption, suggesting that carboxyl moieties of N3 remain bound. We demonstrate the native oxide layer of a titanium sensor as a valid and readily available planar TiO2 morphology to study dye adsorption and desorption and begin to investigate the mechanism of dye desorption in DSSCs, a system that requires further study. © 2014 American Chemical Society. Source

Eisele N.B.,CIC Biomagune | Eisele N.B.,Max Planck Institute for Biophysical Chemistry | Andersson F.I.,Biolin Scientific | Frey S.,Max Planck Institute for Biophysical Chemistry | And 2 more authors.

Immobilization of proteins onto surfaces is useful for the controlled generation of biomolecular assemblies that can be readily characterized with in situ label-free surface-sensitive techniques. Here we analyze the performance of a quartz crystal microbalance with dissipation monitoring (QCM-D) sensor surface that enables the selective and oriented immobilization of histidine-tagged molecules for morphological and interaction studies. More specifically, we characterize monolayers of natively unfolded nucleoporin domains that are rich in phenylalanine-glycine repeats (FGRDs). An FGRD meshwork is thought to be responsible for the selectivity of macromolecular transport across the nuclear pore complex between the cytosol and the nucleus of living cells. We demonstrate that nucleoporin FGRD films can be formed on His-tag Capturing Sensors with properties comparable to a previously reported immobilization platform based on supported lipid bilayers (SLB). Approaches to extract the film thickness and viscoelastic properties in a time-resolved manner from the QCM-D response are described, with particular emphasis on the practical implementation of viscoelastic modeling and a detailed analysis of the quality and reliability of the fit. By comparing the results with theoretical predictions for the viscoelastic properties of polymer solutions and gels, and experimental data from an atomic force microscopy indentation assay, we demonstrate that detailed analysis can provide novel insight into the morphology and dynamics of FG repeat domain films. The immobilization approach is simple and versatile, and can be easily extended to other His-tagged biomolecules. The data analysis procedure should be useful for the characterization of other ultrathin biomolecular and polymer films. © 2012 American Chemical Society. Source

Yang Z.,Argonne National Laboratory | Dixon M.C.,Biolin Scientific | Erck R.A.,Argonne National Laboratory | Trahey L.,Argonne National Laboratory
ACS Applied Materials and Interfaces

Electrochemical quartz crystal microbalance coupled with dissipation (EQCM-D) is employed to investigate the solid electrolyte interphase (SEI) formation and Li insertion/deinsertion into thin film electrodes of tin. Based on the frequency change we find that the initial SEI formation process is rapid before Li insertion but varies significantly with increasing concentration of the additive fluoroethylene carbonate (FEC) in the electrolyte. The extent of dissipation, which represents the film rigidity, increases with cycle number, reflecting film thickening and softening. Dissipation values are almost twice as large in the baseline electrolyte (1.2 M LiPF6 in 3:7 wt % ethylene carbonate:ethyl methyl carbonate), indicating the film in baseline electrolyte is roughly twice as soft as in the FEC-containing cells. More importantly, we detail how quantitative data about mass, thickness, shear elastic modulus, and shear viscosity in a time-resolved manner can be obtained from the EQCM-D response. These parameters were extracted from the frequency and dissipation results at multiple harmonics using the Sauerbrey and Voigt viscoelastic models. From these modeled results we show the dynamic mass changes for each half cycle. We also demonstrate that different amounts of FEC additive influence the SEI formation behavior and result in differences in the estimated mass, shear modulus and viscosity. After three cycles, the film in baseline electrolyte exhibits a 1.2 times larger mass change compared with the film in the FEC-containing electrolyte. The shear elastic modulus of films formed in the presence of FEC is larger than in the baseline electrolyte at early stages of lithiation. Also with lithiation is a marked increase in film viscosity, which together point to a much stiffer and more homogeneous SEI formed in the presence of FEC. © 2015 American Chemical Society. Source

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