Self-Assembled Surfactant Micelles And Silica Nanochannels As The Extraction Matrix For Electrochemical Analysis

Surfactants are amphiphilic compounds which possess two important properties, i.e., adsorption at the interface and self-assembly to supramolecule. They have been widely used in the electrochemistry and electroanalytical chemistry. They can control the reaction rate by modifying or controling the surface properties. Moreover, they can also control the reaction pathway. As a cation surfactant, cetyltrimethyl ammonium bromide (CTAB) can be employed as the template to prepare vertically ordered silica mesochannels (VSMs). Meanwhile, the CTAB molecules confined in nanochannel formed highly orderd cylindrical surfactant micelles (CSMs). Thus obtained hybrid film consisting of VSMs and CSMs, designated as CSM@VSM, can function as a good matrix for electrochemical analysis. First, VSMs can markedly enhance the extraction property towards the lipophilic analytes with the hydrophobic cores. Second, VSMs display apparent size exclusion effect, selectively extracting small organic molecules. Third, the film also own antipollution ability. In this work, indium tin oxide glass (ITO) was used as the substrate electrode, on which CSM@VSM was modified. The modified electrode was used for concentration and detection of antibiotics and phenolic antioxidants. The detection of target molecules in real samples was also succesfully achieved.Chapter one simply summarizes the typical characteristics of the surfactant, outlines the surfactant adsorption at the solid-liquid interface, introduces two kinds of structure of the surfactant formation-micelle and microemulsion. The application of surfactant in the voltammetric analysis and the approaches for the preparation of ordered micelles are also reviewed.The second chapter describes how to modify the CSM@VSM thin film on the ITO surface and the use in the detection of antibiotic molecules, achieving the electrochemical analysis of organic material under test by integrating extraction/enrichment and detection. As a result, the sensor can detect chloramphenicol (CAP) and nitrofurantoin (NFT) respectively, with a wider linear range and lower detection limit. The CAP presents two linear ranges of 0.1-3.6 ppm and 3.6-15.0 ppm, respectively, with a low detection limit of 40.0 ppb. And the detection range of NFT are 0.1-3.4 ppm and 3.4-15.0 ppm, with a low detection limit of 76.0 ppb. Furthermore, this method was used for detection of CAP in the two actual samples of milk and honey. The experimental results show that the response sensitivity of the modified electrodes for CAP in complex samples is much higher than that of blank ITO, reliable results have also been achieved in the recovery test in low concentration levels.The third chapter expounds the synthesis of CSM@VSM composite membrane containing surfactant micelles in channel in the ITO substrate according to Stober solution growth method, which could be used for the enrichment and detection of phenolic antioxidants. In this work, differential pulse stripping voltammetry (DPSV) was used to detect the content of tert-butylhydroquinone (TBHQ) and butylated hydroxyanisole (BHA) which was enriched in the channel after extraction respectively. A linear detection range was obtained for TBHQ determination, namely 1.8 - 100.0 μM, as well as a detection limit at 0.66 μM. A linear detection range from 0.3 μM to 27.7 μM and a detection limit of 0.13μM were obtained for BHA.The fourth chapter summarizes the above two aspects of work, and the application prospects of CSM@VSM modified electrode in the field of electrochemical sensor analysis are given as well.