Investigation of Electrical Double Layers on SIO2 Surfaces by Means of Forcevs. Distance Measurements

Abstract

The formation of electrical charges at solid/liquid interfaces results in a diffuse electrical double layer close to the solid surface. This layer determines, for example, the behaviour of ceramic particles in aqueous media and the effective pore radius of membranes acting in liquids. The SiO2/SiO2 system is used to demonstrate that linear measurements using atomic force microscopy are suited for characterizing double layers at real surfaces. It has to be taken into consideration that the tip itself, which is acting as the probe, is also surrounded by a double layer and responds to the composition of the electrolyte in a material‐specific way. For this reason an oxidized silicon tip was used for the present investigations, so that tip and sample consisted the same material. In this way it is possible to obtain results that can be evaluated easily and compared with the DLVO theory.© 1997 John Wiley & Sons, Ltd.

Chemical and Biochemical Analysis Using Scanning Force Microscopy

“…At a pH of 6.2, however, the double-layer interaction vanished, indicating that the Si 3 N 4 surface was not charged and that the IEP of Si 3 N 4 is 6.2. In similar experiments using a Si 3 N 4 tip and an alumina surface, Raiteri and co-workers determined the IEP of Si 3 N 4 to be at pH 6.5, a finding similar to that of Lin et al Furthermore, Huttl and co-workers have examined the pH dependence of the forces between a silicon oxide tip and a silicon oxide surface.…”

Charge Properties and Electric Field Energy Density of Functional Group-Modified Nanoparticle Interacting with a Flat Substrate

“…By changing the above conditions to enhance or weaken the interaction between the particle and the plate, the local H + ion concentration in the PE brush layer at the bottom of the particle changes, which affects the chemical reaction equilibrium in the brush layer, and changes the number of positive and negative ion groups. Because the nanoparticles modified by the PE brush layer have been widely used in colloid science, biomolecule transport and drug delivery [21,[31][32][33][34][35][36][37], and many nanofluid devices (such as nanopores and nanochannels) use PE brush layer as wall coating [38][39][40], we investigate the charge characteristics of nanoparticles modified by a PE brush layer interacting with a flat plate. In contrast to most previous studies on surface charge density changes of silica particle, we analyzed the effects of local pH and background salt concentration on bulk charge density using a multi-ion charge regulation model, as well as the changes of electric field energy density in brushed nanoparticle brushes at different distances to study the charge/discharge effect between particles and plate [41][42][43].…”

Microfabrication of colloidal scanning probes with controllable tip radii of curvature

“…The run-to-run reliability and repeatability are inconsistent and mass fabrication is practically unfeasible. As alternative approaches, different microfabrication processes have been investigated to 'reshape' the sharp SPM probe tips, which include thermal oxidation [20,21] (figure 2(b)), physical or chemical vapor deposition [22,23] (figure 2(c)) and local isotropic etching [24] (figure 2(d)). However, due to the low growth or deposition rates, the 'reshaping' effect of thermal oxidation and material deposition is rather limited [25,26] and also time consuming.…”