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NANOSTRUCTURED ASSEMBLIES FOR SOLID PHASE EXTRACTION OF METAL IONS

Ca, Diep Vu
http://rave.ohiolink.edu/etdc/view?acc_num=miami1107552000

Abstract Details

2005, Doctor of Philosophy, Miami University, Chemistry and Biochemistry.
The main goal of our research was to develop nanostructured materials for i) solid phase extraction of metal ions and ii) electrocatalytic systems. The selective preconcentration of cesium from aqueous solutions containing high concentrations of alkali metals is an important problem in the treatment of radioactive waste. We investigated the use of cobalt hexacyanoferrate (CoHCF) for this purpose. The CoHCF in our work was encapsulated in a silica sol-gel material that is templated to have pores in the nano-domain. A capacity of 0.61 ± 0.01 mmol Cs+ g-1 was achieved for the CoHCF-doped sonogel. The CoHCF silica sol-gels are promising both for the solid phase extraction of Cs+ and for the capture and storage of this cation. For environmental applications, after sorbing Cs+ the glass-like material can be sintered to collapse the pores. We found that silica sol-gel is not only a good hosting material but also a medium for growing crystals and extruding fibers. Here, a sonogel was used to grow CoSO4 and CuSO4 crystals and extrude Prussian Blue-containing fibers. Subsequently, we investigated the use of mixed-ligand monolayer-protected gold nanoclusters (MPCs) with crown ether (CE) and carboxylate functionalities for the preconcentration of cesium from aqueous solution. 18-crown-6 ether was used as a functional group because it has a selective affinity to cesium. Here, the MPCs were used to assemble layer-by-layer (LBL) films on a substrate. The uptake of cesium from solution by these films was monitored by a quartz crystal microbalance. Our general interest was to modify electrode surfaces that can selectively interact with substances ranging from metal ions to biological models. We focused on the former as a surrogate. Thus, the study was developed for a metal ion, Pb2+ which is electrochemically active. In this case, 15-crown-5, which selectively complexes with Pb2+, was used instead of 18-crown-6. The electrostatic LBL films were assembled on gold and indium tin oxide (ITO) electrodes. Trapping Pb2+ within these nanostructured films was demonstrated by voltammetry and quartz crystal microbalance measurements. Metal nanoparticles (NPs) can have different electrocatalytic properties from the corresponding bulk metal under given conditions. A hypothesis of our study was that NP catalysts can be optimized by controlling the distribution of metal NPs on an electrode surface. The oxidation of cysteine and arsenite were the test systems for AuNPs and PtNPs, respectively. Generation-4 poly(amidoamine)-encapsulated Au and Pt nanoparticles were synthesized. The metal-PAMAM NPs were assembled on an ITO electrode. The PAMAM was then decomposed by heating, leaving the NPs on the ITO. The surface excess, gamma, of PAMAM-metal NPs was controlled. The catalytic oxidation of cysteine at the resulting AuNP array was observed. Interestingly, a study of the cyclic voltammetric peak current vs gamma showed that a small amount of metal NPs dispersed on a surface electrode gave high electrocatalytic activities. For example, a mole fraction of Au-PAMAM in the assembled layer of 0.062 yielded the highest sensitivity. Linear calibration curves were obtained over the range 5 uM - 500 uM for cysteine with AuNP catalysts. For AsIII with PtNPs, linearity was observed over the range 0.2 mM – 1.0 mM.
James Cox (Advisor)
231 p.
Chemistry, Analytical
Nanoparticles; Au; Pt; ITO; LBL; electrochemistry

Recommended Citations

Citations

  • Ca, D. V. (2005). NANOSTRUCTURED ASSEMBLIES FOR SOLID PHASE EXTRACTION OF METAL IONS [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1107552000

    APA Style (7th edition)

  • Ca, Diep. NANOSTRUCTURED ASSEMBLIES FOR SOLID PHASE EXTRACTION OF METAL IONS. 2005. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1107552000.

    MLA Style (8th edition)

  • Ca, Diep. "NANOSTRUCTURED ASSEMBLIES FOR SOLID PHASE EXTRACTION OF METAL IONS." Doctoral dissertation, Miami University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1107552000

    Chicago Manual of Style (17th edition)

miami1107552000
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© 2005, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.