A great deal of progress has recently been made in the field of ordered porous materials with uniform channel dimensions that can be adjusted over a wide range of length scales. The present paper describes the state of the art and the evolution from highly ordered mesoporous silica, aluminosilicate and pure carbon materials to our very recent success in hierarchically structured meso-macroporous carbon materials, single and binary oxides and aluminosilicates. By means of selected examples, we want to shed some light on the current strategies for the conception of these sophisticated materials. The great potential applications of these new nanomaterials emerge while their real utilisation in some expected and traditional industrial processes such as catalysis, separation, electrode materials for fuel cells and biomaterials still faces some important challenges, for example, the high price, the pelletisation and the stability (thermal, hydrothermal and water resistance). Some new perspectives, which can open the concrete applications of these materials in nanotechnology, biotechnology, information technology and medical purposes, will be prospected.
An electrochemical detector was designed and constructed, based upon a thin-layer cell with a working electrode prepared from carbon paste modi®ed with copper-(or silver-) exchanged zeolite particles. This electrode was then evaluated as a sensor for nonelectroactive cations in an electrolyte-free¯ow injection system and as an amperometric detector for suppressed ion chromatography. In the absence of supporting electrolyte, a higher signal-to-background ratio enhanced by about two order of magnitude the response obtained in electrolytic medium. Peak currents resulted from an important faradic component which was due to the electrochemical activity of the mediatorcontaining zeolites, while the capacitive counterpart was much lower. When applied to the analysis of alkali, alkaline earth metal and ammonium ions, in combination with a suppressed ion chromatography system, the zeolite-modi®ed detector gave rise to reproducible amperometric responses. This resulted in chromatograms comparable to those obtained simultaneously by using a conductivity detector in series, and any extra-column effects were never observed. The most sensitive responses were achieved when using zeolites displaying the largest pore size, the highest ion exchange capacity, and the most mobile mediator, to ensure the highest exchange rates for the analytes within the zeolite framework.
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