Surface Properties Of Monolayers Research Articles

Local desorption of thiols by scanning electrochemical microscopy: patterning and tuning the reactivity of self-assembled monolayers

Self-assembled monolayers (SAMs) are widely used in the field of nanotechnologies and (bio)sensors. The monolayer surface properties are tailored by employing several techniques. A large set of SAM post-modification routes are commonly performed to adapt them to a variety of nano-technological and bio-technological studies as well as to several bio-sensoristic applications. Here, we report a procedure to locally modify SAMs by electrochemical desorption of alkanethiols in order to create microsized spots of bare gold area without affecting the surrounding monolayer stability. The tip of the scanning electrochemical microscope (SECM) was employed to draw microstructured pattern according to a defined geometry. The time stability of the pattern was also tested. Furthermore, the patterned surface was post-functionalized using the same alkanethiol or a ferrocene-terminated thiol, in order to tune the surface reactivity of the microstructure. The local surface properties, including reactivity and electron transfer kinetics toward redox mediator reduction, were characterized by SECM.

Quantitative studies on the dependence of NDV penetration and elution on the attachment multiplicity

Using32P-labelled NDV at various attachment multiplicities of infection the respective quantities of both eluted and cell-associated virus after one hour period of incubation at 37° C were determined, the virus attachment being carried out at 4° C. It turned out to be impossible to separate directly the fraction of cell-associated virus into the fractions of penetrating and cell surface-bound virus by means of the treatment of the cell monolayer with 8m solution of urea. An approach consisting in the consideration of certain mathematical models made it possible to estimate penetrating virus as a fraction of the whole quantity of the cell-associated virus remaining upon the cell surface after the incubation at 37° C. The experimental data turned out to be compatible with the hypothesis based on the stochastic nature of the virus penetration and elution processes and the uniformity of both virus population and cell monolayer surface properties with regard to virus penetration and elution.

Surface isotherms of eicosanoic acid (C 20) and sodium eicosylsulfate (C 20) on substrates containing substituted alkanol amines

The force-area (Tr-~) and surface-potentialarea (~XV-~) characteristics of Arachidic acid (eicosanoic acid, C20) and sodium eicosylsulfate (C20) monolayers at the airwater interface have been investigated over 0.1 N solutions of various substituted alkanol amines. This study of the effect of a series of alkanol amines as cations, at constant ionic strength (0.I N), on the surface properties of an aliphatic carboxylate and an aliphatie sulfate (both C20) was undertaken in order to determine the role played by the stereochemistry, and substitution, within the series. An automated Langmuir trough was used to establish reproducible compression and expansion surface isotherms. Since at high pH monolayers become slightly solubilized into the aqueous substrate, the use of an automated Langmuir trough allows one to overcome this difficulty. Compression-expansion surface isotherms allows one to compare the hysteresis areas (work lost following compression-expansion of the monolayers) of the various long-chain salts. The comparison of compression and expansion isotherms appears to be related to foamability and foam stability. The correlation between monolayer surface properties and foaming characteristics (5) will be presented in a subsequent paper. Theories associated with surface potential, based on elementary models, are generally barely applicable. Nevertheless, it was found that our results could be interpreted by using unsophisticated : assumptions. The reason for this development is probably attributable to our choice of substituted alkanol amines.