This article aims to review the electroanalytical applications of chemically modified electrodes involving silica and silica-containing matrices. After a brief introduction to silica chemistry, the implication of pure and grafted silicas in electrochemistry, as well as that of the silica-based materials originating from the sol-gel technology, will be discussed. The interest of silica-modified electrodes (SiO2-MEs) with respect to electroanalysis will be pointed out by means of several examples. In the last five years, successful applications of SiO2-MEs have been achieved. Among them, silica grafted with inorganic films or organic moieties was successfully applied to the selective preconcentration or the electrocatalytic detection of various analytes. Also, the ability of the sol-gel chemistry to encapsulate enzymes within a silica matrix without preventing its activity was exploited in the development of new amperometric biosensors. These promising fields are thought to lead to significant advances in the near future, because of the explosive growth in both the synthesis of novel mesoporous organically-modified silica-based materials and the huge development of sol-gel chemistry in tailoring and construction of new modified electrodes.

Analytical Applications of Silica-Modified Electrodes -A Comprehensive Review

Zeolite-modified electrodes in electroanalytical chemistry

Microporous zeolites and ordered mesoporous (organo)silicas have been widely used as electrode modifiers because of their attractive properties (ion exchange and size selectivity of zeolites, well ordered nanoreactors containing a high number of widely accessible active centers in mesoporous (organo)silicas). These properties have been intelligently combined to selected redox processes to improve the response of the resulting modified electrodes or to design novel electrochemical detection schemes. This up-to-date review provides the recent advances made in the electroanalytical applications of zeolite modified electrodes and discusses the interest of ordered mesoporous (organo)silica materials in electroanalysis.

Electroanalytical Applications of Microporous Zeolites and Mesoporous (Organo)Silicas: Recent Trends

A review is presented dealing with the use of zeolite-modified electrodes (ZMEs) for electroanalytical purposes (183 references). It includes an introduction to the zeolite molecular sieves, a short overview of zeolites and electroactive species used at electrochemical interfaces modified by the presence of zeolite particles, three aspects of the electroanalysis using ZMEs, including voltammetry, potentiometry and electrocatalysis. New prospects concerning the electrochemistry of ZMEs are also discussed.

Zeolite‐modified electrodes: Analytical applications and prospects

Factors affecting the analytical applications of zeolite-modified electrodes preconcentration of electroactive species

The performance of synthetic-polymer membrane-electrodes for cation sensing is investigated by obtaining E versus pM graphs and E versus time curves of the same membrane type under different treatments or of membranes constructed by modified procedures. The slopes of E versus pM curves for the salts of monovalent cations show different values for the same membrane type as well as for the different membrane types and are found within the range of 43 to 57 mV per pM. The response time of the membrane is found to be slower when the membranes are plastic phase deficient. Generally, the detection limit is only slightly dependent on the composition of the membrane and the best value is obtained with the polished membranes which is close to the value of pM=5 while for the other membranes the values are within the range of pM 4 to 5. The range of linearity is also slightly dependent on the method of membrane construction and in general is shorter when the membranes are plastic phase deficient. The selectivity coefficients are found to depend significantly on the method of construction of the membrane but in general the selectivity of all the membranes studied in this report is poor. The asymmetry potential is found to be related to an ion exchange process and is developed slowly in 5A-type membranes. However, when the value of asymmetry potential is high, a longer time is needed to reach the final value of e.m.f. in measurements among different concentrations of the same metal ion and much longer is needed where there is switching of measurement from a monovalent cation to a divalent cation.

A. G. Vlessidis

Papers

Effect of treatment of synthetic zeolite-polymer membranes on their electrochemical-potential response characteristics