Fabrication And Properties Of Colorimetric Sensors For Metal Ion And Silicon Material Based On Natural Cellulose Substance

Owing to its advantages such as on-site, real time qualitative and without complicated and expensive instruments, optical chemical sensors have received a great deal of attention. Colorimetric sensors, of course, have received much more attention because it can realize the detection of heavy metal ion through naked-eye. Thus, colorimetric sensors have a wide space for development. As it well known to us, cellulose such as filter paper, cotton and cloth is the cheapest and easily accessible organic raw materials in the world. Cellulose is a natural polymer which consists of repeat units ofβ-(1â†'4)-D-glucopyranose; polymer chains assemble into randomly sophistical hierarchical three-dimensional network structure through multiple hydrogen bonding. Therefore, it is a good choice to use natural cellulose substances as ideal scaffolds and templates to fabricate chemosensors.Using natural cellulose as scaffolds or templates, silica ultrathin film was coated on cellulose nanofibers by surface sol-gel method to activated hydroxyl groups of cellulose surface for further modification. Then, dye molecules were deposited self-assembly onto silica thin film to fabricate heavy metal ion (Cd2+, Cu2+) colorimetric sensors. Or removing of cellulose template through calcinations, then through low temperature magnesiothermic reduction to fabricate silicon material with hierarchical morphologies and three-dimensional structure which were derived from the initial filter paper, at last, we studied the electrochemical properties of the obtained silicon materials. In order to improve the electrochemical properties of silicon material, silver nanoparticles were introduced into silicon materials to fabricate silver-coated silicon material with better electrochemical properties. The main research details and the results are as follows:1. The fabrication and properties of colorimetric Cd2+sensing material based on natural substances. Employing natural cellulose (common commercial quantitative filter paper) as scaffolds, we designed and fabricated a colorimetric heavy metal ion sensor which can detect Cd2+in aqueous solution and also can be recycled to use. First of all, employing surface sol-gel technique, ultrathin silica film was coated onto the individual nanofibers of cellulose materials. Then, TMAC molecules N-trimethoxylsilylpropyl-N, N, N-trimethylammonium chloride was deposited self-assembly onto silica thin film pre-coated filter paper. At last, PAR dye molecules4-(2-pyridylazo) resorcinol was immobilized onto TMAC monolayer elctrostatically to fabricate sensing materials. The sensing materials of colorimetric detection of Cd2+possess good sensitivity and selectivity. Upon exposure to higher concentrations of Cd2+aqueous solution, the sensing materials will turn purple from yellow and the detection limit is5μ.M. We also studied the recycling of sensing materials, which can be reused by treatment with0.5M EDTA aqueous solution.2. The fabrication and properties of colorimetric Cu2+sensing material based on natural substances. First of all, we synthesized compound RHB-tren using Rhodamine B and tri (aminoethyl) amine as raw materials, then obtained compound RHB-tren-NCO using RHB-tren and triethoxysilylpropylisocyanatc as reactants. Last, we studied response of the compound RHB-tren-NCO in acetonitrile solution upon addition of Cu2+. Upon exposure of high concentrated Cu2+, the Rhodamine derivative RHB-tren-NCO in acetonitrile would turn pink form colorless. Other metal ion would not cause such color change when addition into the solution of RHB-tren-NCO. The compound RHB-tren-NCO possesses better selectivity. Further more, Rhodamine derivative RHB-tren-NCO was immobilized onto silica layer pre-coated onto natural substance to fabricate Cu2+colorimetric sensing materials and the properties of sensing metal ion were studied.3. Magnesiothermic reduction of silica to fabricate silicon and further researched its electrochemical properties. Using natural cellulose (common commercial filter paper) as templates, silica ultrathin film was coated on cellulose nanofibcrs by surface sol-gel method, and then calcinations to obtain pure silica materials with hierarchical and complex structure of cellulose filter paper. Then through low temperature magnesiothermic reduction to fabricate silicon material with hierarchical morphologies and three-dimensional structure which were derived from the initial filter paper. We studied the electrochemical properties of obtained silicon materials and found its relative low capacitance value. In order to improve capacitance of silicon materials we introduced silver nanoparticles onto silicon material to fabricate Ag-coated silicon materials with better capacitance.