The influence of counter-ion adsorption on the ψ0/pH characteristics of insulator surfaces

Abstract

The site-binding theory of Yates, Levine, and Healy is extended to include the possibility that counter-ion binding of anions and cations occurs at different distances from the insulator surface. A method for straightforward computation of the $,,/ea/pH characteristics is given. This theory is applied to the study of electrolyte/insulator/silicon structures, which makes it possible to measure the $e/pH characteristics. Measurements are presented for structures where the insulator is y-AlaO, deposited by chemical vapour deposition at 900°C. The influence of counter-ion binding on the +e/pH curves is a second-order effect compared to the site-dissociation acid/base reactions, but it is clearly visible. Consideration of the influence of the ionic strength of the electrolyte leads to an estimated anion adsorption equilibrium constant in the range of 0.05 to 0.4 mol-' dm3 in chloride solutions, although no significant influence of the type of ions present could be observed. Application of the theory to existing measurements of the +,,/pH and oa/pH curves of SiO, surfaces indicates that for this material the cation adsorption equilibrium constant is in the order of 0.1 mol-' dm3.

Interaction of colloidal nanoparticles with their local environment: the (ionic) nanoenvironment around nanoparticles is different from bulk and determines the physico-chemical properties of the nanoparticles

“…Additionally, table 1 provides literature for a more detailed study, sorted by the metals (Au, Ag) studied. [107][108][109][110][111]. At low pH, the surface can be charged positively by the adsorption of protons (MOH 2 þ ), whereas it will be negatively charged at high pH owing to depletion of protons (M-O 2 ).…”

Silicon‐on‐Insulator Based Thin‐Film Resistor for Chemical and Biological Sensor Applications

“…This has been discussed very actively in the literature, and different models have been used to explain the mechanism of surface complexation of alkali ions. [12,13] The potential at a surface with a constant charge density is controlled by the salt concentration of the electrolyte solution. Hence, any change in salt concentration will alter the surface potential.…”

The Effects on the Response of Metal Oxide and Fluorite Single Crystal Electrodes and the Equilibration Process in the Interfacial Region

“…for measuring the pH of a solution). [18][19][20][21][22][23][24][25] An electrode based on the ISFET concepts consists of a metal attached to a semiconductor (e.g. Si) whose surface is covered by the phase of interest, an insulator (e.g.…”

“…The ISFET electrode is a sensitive electronic device for determining the concentration of H + ions and also for the study of equilibrium processes at the metal oxide/aqueous electrolyte interfaces. ISFETs have been successfully used for SiO2, [21] TiO2, [22] Al2O3 [20] surfaces. The sensitivity of the ISFET electrode (the dependency of surface potential) to pH (compared to the Nernstian slope) is given in Table 1.…”

“…The next attempt was to use semiconducting materials such as an ion sensitive field-effect transistor (ISFET). [18][19][20][21][22][23][24][25] The ISFET electrode was already used as a sensitive electronic device for determining the concentration of H + ions in the solutions. Twelve years ago, the first metal oxide single crystal electrode (SCrE) was constructed ( Figure 2c) [26] and since then have been developed (Figure 2d) [9,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] A special case of the single crystal electrode is the ice electrode, [43,44] i.e.…”