Physical methods of chemistry
01 Jan 1986-
About: The article was published on 1986-01-01 and is currently open access. It has received 542 citations till now.
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TL;DR: Supporting lipid-protein bilayers form versatile models of low-dimensionality complex fluids, which can be used to study interfacial forces and wetting phenomena, and enable the design of phantom cells to explore the interplay of lock-and-key forces and universal forces for cell adhesion.
Abstract: Scientific and practical applications of supported lipid-protein bilayers are described. Membranes can be covalently coupled to or separated from solids by ultrathin layers of water or soft polymer cushions. The latter systems maintain the structural and dynamic properties of free bilayers, forming a class of models of biomembranes that allow the application of a manifold of surface-sensitive techniques. They form versatile models of low-dimensionality complex fluids, which can be used to study interfacial forces and wetting phenomena, and enable the design of phantom cells to explore the interplay of lock-and-key forces (such as receptor-ligand binding) and universal forces for cell adhesion. Practical applications are the design of (highly selective) receptor surfaces of biosensors on electrooptical devices or the biofunctionalization of inorganic solids.
2,123 citations
TL;DR: An emphasis is put on the combination set-up of surface plasmon optics with electrochemical techniques, allowing for the on-line characterization of various surface functionalization strategies, e.g. for (bio-) sensor purposes.
Abstract: This contribution summarizes the use of plasmon surface polaritons and guided optical waves for the characterization of interfaces and thin organic films. After a short introduction to the theoretical background of evanescent wave optics, examples are given that show how this interfacial “light” can be employed to monitor thin coatings at a solid/air or solid/liquid interface. Examples are given for a very sensitive thickness determination of samples ranging from self-assembled monolayers, to multilayer assemblies prepared by the Langmuir/Blodgett/Kuhn technique or by the alternate polyelectrolyte deposition. These are complemented by the demonstration of the potential of the technique to also monitor time-dependent processes in a kinetic mode. Here, we put an emphasis on the combination set-up of surface plasmon optics with electrochemical techniques, allowing for the online characterization of various surface functionalization strategies, e.g. for (bio-) sensor purposes.
958 citations
TL;DR: The surface plasmon microscopy (SPM) method as mentioned in this paper uses plasmor surface polariton (PSP) fields instead of normal light as the illumination source, which can provide superior contrast without loss of spatial resolution.
Abstract: The imaging of low-contrast samples is a challenging task for optical measuring techniques, especially if high lateral resolution is also required. For example, a heterogeneously organized lipid monolayer transferred from the water surface to a solid substrate1 still needs an additional contrast enhancement mechanism (the solubility difference for a fluorescing chromophore incorporated between the fluid and the crystalline domains of the monolayer) to be visualized by fluorescence microscopy. The mere thickness or index contrast between the different regions is not sufficient to use either phase contrast or Nomarsky microscopy2 or the more recently developed Isoscope ellipsometer3. Here we describe a new microscope technique—surface plasmon microscopy (SPM)— which offers superior contrast without loss of spatial resolution by using plasmon surface polariton (PSP) fields instead of normal light as the illumination source. Such electromagnetic modes travel along a metal–dielectric interface as a bound, non-radiative surface wave, with its field amplitudes decaying exponentially perpen-dicular to the interface. Although photons can be converted into PSPs by means of a plasmon coupler (a grating or a prism in many cases) this 'light' differs considerably from plane electromagneticwaves4. PSPs are characterized by first, a pronounced disper-sion (energy and momentum are not linearly related by the speed of light); and second, a field intensity that is concentrated at the interface and strongly enhanced there. Some of these properties make these modes a sensitive measure of interfaces and ultrathin films. If plasmon surface polariton fields are used to illuminate interfacial structures in light microscopy, high contrast without loss of spatial resolution can be obtained owing to the high sensitivity of the plasmon resonance coupling to (for example) small optical thickness variations of thin dielectric coatings.
718 citations
TL;DR: A generally useful method for obtaining electronic and vibrational Stark spectra that does not require sophisticated equipment is described and applications to donor-acceptor polyenes, transition metal complexes, and nonphotosynthetic biological systems are reviewed.
Abstract: Stark spectroscopy has been applied to a wide range of molecular systems and materials. A generally useful method for obtaining electronic and vibrational Stark spectra that does not require sophisticated equipment is described. By working with frozen glasses it is possible to study nearly any molecular system, including ions and proteins. Quantitative analysis of the spectra provides information on the change in dipole moment and polarizability associated with a transition. The change in dipole moment reflects the degree of charge separation for a transition, a quantity of interest to a variety of fields. The polarizability change describes the sensitivity of a transition to an electrostatic field such as that found in a protein or an ordered synthetic material. Applications to donor-acceptor polyenes, transition metal complexes (metal-to-ligand and metal-to-metal mixed valence transitions), and nonphotosynthetic biological systems are reviewed.
560 citations
TL;DR: In this paper, the surface roughness and nanometer scale structure of Ag films used for surface-enhanced Raman scattering (SERS) are characterized using atomic force microscopy (AFM).
Abstract: The surface roughness and nanometer scale structure of Ag films used for surface‐enhanced Raman scattering (SERS) are characterized using atomic force microscopy (AFM). Two important types of thin film based SERS‐active surface have been examined in this study: (1) Ag island films (AgIF’s) on smooth, insulating substrates and (2) thick Ag films evaporated over both preroughened and smooth substrates. AFM is demonstrated to be capable of quantitatively defining the three‐dimensional (3D) structure of these roughened surfaces. The effects of mass thickness, dm, and thermal annealing on the nanostructure of AgIF’s are studied in detail. Particle size histograms are calculated from the AFM images for both ‘‘as‐deposited’’ and annealed IF’s with dm=1.8 and 3.5 nm. Quantitative measurements of the SERS enhancement factor (EF) are coupled with the AFM data and interpreted within the framework of the electromagnetic theory of SERS. AFM images for thick evaporated Ag films over a monolayer of polymer nanospheres (AgFON) shows the clear presence of ‘‘random substructure roughness’’ reducing their utility as controlled roughness surfaces. Similar roughness structures are observed for thick evaporated Ag films on smooth, insulating substrates. Nevertheless, AgFON surfaces are demonstrated to be among the most strongly enhancing thin film based surfaces ever studied with EF’s comparable to those found for electrochemically roughened surfaces. Applications of FON surfaces to ultrahigh sensitivity SERS, anti‐Stokes detected SERS, and surface‐enhanced hyper‐Raman spectroscopy (SEHRS) are reported.
464 citations