The surface properties of any substance in the solid state differ from its bulk properties. This can give rise to the formation of a liquid-like layer (LLL) at the interface, at temperatures below the melting point. The phenomenon generated interest among both theoreticians and experimentalists for more than 150 years and was studied, employing different techniques. However, electrochemical techniques have not been implemented in studies of this phenomenon.We used, for the first time, the quartz crystal microbalance (QCM) to study the LLL at the ice/gold and the frozen electrolyte/gold interfaces. It was shown that the QCM in contact with ice or with frozen electrolyte at temperatures well below the melting point shows detectable resonance. The parameters of the resonance depend strongly on temperature, composition of the frozen phase, adsorption taking place at the gold surface (including gold surfaces modified by different thiol-derivates) and, in the case of electrolyte, on the potential applied across the interface.Corresponding theoretical models have been developed to understand the kind of information contained in the response of the QCM on the properties of the LLL. Independent data obtained with a device allowing direct optical measurement of the displacement show good agreement with the calculations of thickness of the LLL based on developed models. (C) 2005 Elsevier Ltd. All rights reserved.

The surface properties of any substance in the solid state differ from its bulk properties. This can give rise to the formation of a liquid-like layer (LLL) at the interface, at temperatures below the melting point. The phenomenon generated interest among both theoreticians and experimentalists for more than 150 years and was studied, employing different techniques. However, electrochemical techniques have not been implemented in studies of this phenomenon. We used, for the first time, the quartz crystal microbalance (QCM) to study the LLL at the ice/gold and the frozen electrolyte/gold interfaces. It was shown that the QCM in contact with ice or with frozen electrolyte at temperatures well below the melting point shows detectable resonance. The parameters of the resonance depend strongly on temperature, composition of the frozen phase, adsorption taking place at the gold surface (including gold surfaces modified by different thiol-derivates) and, in the case of electrolyte, on the potential applied across the interface. Corresponding theoretical models have been developed to understand the kind of information contained in the response of the QCM on the properties of the LLL. Independent data obtained with a device allowing direct optical measurement of the displacement show good agreement with the calculations of thickness of the LLL based on developed models.

Electrochemical removal of oxygen and hydrogen from aqueous solution in the vicinity of gold electrodes, with simultaneous measurements of the response of the quartz crystal microbalance, show no evidence of gas nano-bubbles attached to the surface, irrespective of its roughness and hydrophobicity. The contact between gold and frozen electrolyte, which forms a liquid-like layer between them, also does not contain gas bubbles. These statements could be extended to nano-bubbles with characteristic dimensions larger than a few nanometers.

A device allowing direct optical measurement of the displacement was employed to measure the thickness of the liquid-like layer. The data were correlated with calculations of the thickness based on admittance data of the quartz crystal microbalance, measured simultaneously. Agreement between the two independent measurements lends strong support for the validity of the models assumed in our calculations. The approach developed here allows the direct measurement of the thickness of the LLL in the range of a few tens up to few hundreds of nanometers.

Poster is devoted to analytical application of direct redoxmetry in the field of cerimetry, iodometry, etc. Questions of the possibility to realize reversible potentials are discussed. The central point is a modification of electrode or usage of novel electrode materials, like electron condactive glass, which allow to make reversible redox measurements down to very low concentrations.

New redoxmetric methods for oxidant’s analysis with using of a high seletive indicator eletrode were developed. The basis of these methods - high selectivity of platinum electrode with modified surface to redox system J. High precision and technical simplicity were achived by application of a standard addition method. The standard addition of molecular iodine was generated by coulometric anodic oxidation of iodide without division cathodic and anodic spaces.