Current Sensor Of Langmuir-Bodgett Film Of P-allylcalixarenes And Its Application In Electroanalysis

Tools have been playing most important role in the process of society development. Chemically modified electrodes (CMEs), one important tool in electrochemistry, have received increasing attentions which enhance the sensitivity and selectivity of electrochemical analysis techniques. Several methods have been used for electrode modification. Langmuir-Blodgett (LB) method has become one of the most widely used approach because it allows the formation of films with a high internal order, with the desired number of layers, the possibility of depositing alternate monolayer of different molecules, etc. On this purpose, we have done some works about current sensor. The main results are expressed as follows:1. Behavior of LB film of calixarenes at air/water interfaceCalixarenes are macrocyclic molecules made up by base-induced condensation of p-substituted phenols and formaldehyde. The interest on calixarenes has been increased for their complexing abilities, conformational flexibility, and reactivity. The glassy carbon electrodes modified with LB films of calixarenes were studied, π-k isotherms show that p-tert-butylcalixarene and p-allylcalix[4]arene can form stable LB films. The average area value per molecule increase with the increasing of cavity size, however, the value of p-tert-butylcalix[8]arene is unexpectedly smaller than that of p-tert-butylcalix[6]arene.2. Determination of thallium and cadmium on a chemically modified electrode with LB film of p-allylcalix[4]areneA new type of current sensor, LB film of p-allylcalix[4]arene coated glassy carbon electrode (GCE) was described for simultaneous determination of trace thallium and cadmium in environmental water. The LB film electrode in 0.1M KH₂PO₄ solution shows linear voltammetric response in the range of 5.0-250.0 μg L^-1 for thallium and 10.0-300.0 μg L^-1 for cadmium. The detected limit of thallium(I) and cadmium(II) are estimated to be 1.0 μg L^-1 (ca. 5.0×10^-9 mol L^-1) and 2.2 μg L^-1 (ca. 2.0×10^-8 mol L^-1), respectively. Above all, the indium is not response at this LB film electrode. The recognition mechanism of this electrode for thallium and cadmium ion in aqueous solution was discussed. The hard soft acid base (HSAB) principle involves in the mechanism.3. Electrode Modified with LB Film of Calixarenes for Freconcerntration and Stripping Analysis ofHg(II)LB film of calixarene on the surface of GCE was prepared for determination of mercury by anodic stripping voltammetry (ASV). An anodic stripping peak was obtained at 0.15 V (vs. SCE) by scanning the potential from -0.6 to +0.6 V. The fabricated electrode in a 0.1 mol L^-1 H₂SO₄ + 0.01 mol L^-1 HC1 solution shows a linear voltammetric response in the range of 0.07 - 40.0 μg L^-1 and detection limit of 0.04 μg L^-1 (ca. 2.0×10^-10 mol L^-1). The high sensitivity, selectivity, and stability of this LB film modified electrode demonstrated its practical application for a simple, rapid and economical determination of Hg²⁺ in water sample. The allyl groups at the upper rim of calixarene play important role in this recognition process.