Rotating analyzer–fixed analyzer ellipsometer based on null type ellipsometer

Russev, Stoyan C.; Arguirov, Tzanimir Vl.

doi:10.1063/1.1149870

Cited by 19 publications

(13 citation statements)

References 16 publications

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“…The Setup . The adsorbed protein amount was measured by ellipsometry, using a “rotating analyzer” apparatus (with a fixed angle of incidence of 50°). , The scheme of the ellipsometer is shown in Figure a. The two ellipsometric parameters Ψ and Δ, which characterize the protein layer, were determined as functions of time.…”

Section: Methodsmentioning

confidence: 99%

Monolayers of Globular Proteins on the Air/Water Interface: Applicability of the Volmer Equation of State

et al. 2003

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We performed simultaneous measurements of the instantaneous values of the surface pressure versus time, Π(t) (by the Wilhelmy plate method), and the adsorption versus time, Γ(t) (by ellipsometry), for aqueous solutions of a globular protein (β-lactoglobulin, BLG). The resulting dependence Π(Γ) was found to be well described by the Volmer equation of state (when Γ ≤ 1.6 mg/m2, a value corresponding to an almost complete monolayer), for all times and bulk concentrations. The excluded area per molecule, α, turned out to be twice as large as the maximum cross-sectional area of the molecule, ω, in accordance with the theoretical considerations. We processed in the same way available literature data for various proteins (BLG, α-lactalbumin, bovine serum albumin), both for equilibrium and for nonequilibrium adsorbed layers, as well as for spread layers. In all cases, the experimental dependencies Π(Γ) were fitted well by the Volmer equation; the excluded area either was almost exactly twice the maximum cross-sectional area (for spherical molecules) or could be interpreted in a similar way (for nonspherical molecules), by means of qualitatively equivalent reasoning. These results have led us to the following conclusions for the studied globular proteins: (i) The surface state depends only on the instantaneous adsorption, Γ, regardless of how it was reached. (ii) The Volmer equation is obeyed for surface coverages close to or lower than the monomolecular adsorption. (iii) No denaturation occurs during the adsorption process.

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Section: Methodsmentioning

confidence: 99%

Monolayers of Globular Proteins on the Air/Water Interface: Applicability of the Volmer Equation of State

et al. 2003

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“…The polymer adsorption on the air−water interface was determined by ellipsometry. The used instrument is a modification of a conventional null type ellipsometer (LEF 3M, Novosibirsk, Russia), which is adapted for kinetic measurements with time resolution of 1 s. 42 A solid state laser (λ = 532 nm, Compass 215M, Coherent), equipped with a light polarizer, emits a beam with a certain polarization state. All experiments are performed at 50°angle of incidence, which is close to the Brewster angle for water, 53.1°.…”

Section: Foam Testmentioning

confidence: 99%

Foaming and Foam Stability for Mixed Polymer–Surfactant Solutions: Effects of Surfactant Type and Polymer Charge

2012

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Solutions of surfactant-polymer mixtures often exhibit different foaming properties, compared to the solutions of the individual components, due to the strong tendency for formation of polymer-surfactant complexes in the bulk and on the surface of the mixed solutions. A generally shared view in the literature is that electrostatic interactions govern the formation of these complexes, for example between anionic surfactants and cationic polymers. In this study we combine foam tests with model experiments to evaluate and explain the effect of several polymer-surfactant mixtures on the foaminess and foam stability of the respective solutions. Anionic, cationic, and nonionic surfactants (SDS, C(12)TAB, and C(12)EO(23)) were studied to clarify the role of surfactant charge. Highly hydrophilic cationic and nonionic polymers (polyvinylamine and polyvinylformamide, respectivey) were chosen to eliminate the (more trivial) effect of direct hydrophobic interactions between the surfactant tails and the hydrophobic regions on the polymer chains. Our experiments showed clearly that the presence of opposite charges is not a necessary condition for boosting the foaminess and foam stability in the surfactant-polymer mixtures studied. Clear foam boosting (synergistic) effects were observed in the mixtures of cationic surfactant and cationic polymer, cationic surfactant and nonionic polymer, and anionic surfactant and nonionic polymer. The mixtures of anionic surfactant and cationic polymer showed improved foam stability, however, the foaminess was strongly reduced, as compared to the surfactant solutions without polymer. No significant synergistic or antagonistic effects were observed for the mixture of nonionic surfactant (with low critical micelle concentration) and nonionic polymer. The results from the model experiments allowed us to explain the observed trends by the different adsorption dynamics and complex formation pattern in the systems studied.

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“…%), spun at 3000 rpm for 60 s on a microscope cover slip (20 × 20 mm) and hot plate baked at 180°C for 2 minutes. The thickness of the PMMA layer after baking was 105 nm (measured ellipsometrically (Russev & Arguirov, 1999). To avoid charging effects a 200 nm layer of chromium was electron beam evaporated (Edwards E610A) onto the substrate before deposition of the resist.…”

Section: Exemplary Resultsmentioning

confidence: 99%

An electron beam lithography and digital image acquisition system for scanning electron microscopes

Russev¹,

Tsutsumanova²,

Angelov³

et al. 2007

Journal of Microscopy

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Summary A low‐cost microcontroller based control and data acquisition unit for digital image recording of scanning electron microscope (SEM) images and scanning electron microscope based electron beam lithography (EBL) is described. The developed microcontroller low‐level embedded software incorporates major time critical functions for image acquisition and electron beam lithography and makes the unit an intelligent module which communicates via USB with the main computer. The system allows recording of images with up to 4096 × 4096 pixel size, different scan modes, controllable dwell time, synchronization with main power frequency, and other user controllable functions. The electron beam can be arbitrary positioned with 12‐bit precision in both dimensions and this is used to extend the scanning electron microscope capabilities for electron beam lithography. Hardware and software details of the system are given to allow its easy duplication. Performance of the system is discussed and exemplary results are presented.

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Rotating analyzer–fixed analyzer ellipsometer based on null type ellipsometer

Cited by 19 publications

References 16 publications

Monolayers of Globular Proteins on the Air/Water Interface: Applicability of the Volmer Equation of State

Monolayers of Globular Proteins on the Air/Water Interface: Applicability of the Volmer Equation of State

Foaming and Foam Stability for Mixed Polymer–Surfactant Solutions: Effects of Surfactant Type and Polymer Charge

An electron beam lithography and digital image acquisition system for scanning electron microscopes

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