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Preparation and Application of PAMAM composite nanomaterials modified electrode

Author: ShenYing
Tutor: ZhuNingNing
School: Shanghai Normal University
Course: Analytical Chemistry
Keywords: Dendrimers Nanocomposites Pd nanoparticles Electrochemical Detection
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 192
Quote: 1
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Abstract

Detecting based on electro-signal, electro-chemical sensors always attracted people’s attention because it is fast, sensitive, stable, quantitative detection, posible to achive micromation. It is used widely in many fields, such as life sciences, national defense, chemical detection.Nano-materials, named as the most promising materials in the 21st Century, attracts more and more attentions owning to their special properties, such as big surface area, high activity, good ability of catalysis, strong adsorptive ability. Due to their small size, these materials exhibit surface effect, small-size effect, quanta-size effect and tunneling effect. All these give them tremendous potentials in research. Noble metal nanoparticles are widely used in the fields of catalysis. It is a doable job to introduce noble metal nanoparticles into the research of modified electrode to realize the detection of some certain substance; Dendtrimers molecules, with its designed structure, small scale, exterior functional groups and interior cavums, have become the highest materials to research in the fields of genic carrier, nanocomposites, catalyzer and film materials, especially as templates in preparing noble metals nanoparticles. Nanoparticles are stable and showed a narrow distribution size when dendrimers exist; Carbon nanotubes attracted much attention for their properties. Depending on their atomic structure, CNT behave electronic properties suggest that CNT have the ability to promote electron-transfer reactions. With the further development of CNT and nanotechnology, studies on preparation, properties and application of CNT and its composite materials have still been a hot topic attracting lots of researchers in the world.The paper focuses on the application of PAMAM in preparing noble metals nanoparticles and their performance on modified electrodes. It includes two aspects. (1) Preparing stable, small noble metals nanoparticles and their nanocomposites combined with PAMAM dendrimers by the electrochemical and chemical methods. (2) The application of prepared nanoparticles in electro-chemical sensors. We combine the noble metals nanoparticles, PAMAM dendrimers and carbon nanotubes to report an analyticle method which is simple, fast, stable and cheap. Realizing direct detection of H2O2 and noxious substances such as HCHO, N2H4.H2SO4. The pater can be divided into four sections as follows:I The Preparation of Pd Nanoparticles Modified Au Electrode and Its Electrocatalytic Deoxidation of H2O2Gold-bead electrodes were modified by covalent bonding or physical adsorption of several Starburst PAMAM dendrimers followed by absorption of Pd. The covalent dendrimer-Pd modified electrodes can be used in amperometric detection of H2O2 in aqueous solution.The preparation and electrocatalytic properties of the Pd Gold-bead electrode for reduce of H2O2 have been investigated by EIS, XRD, TEM, CV and DPV, and excellent electrocatalytic activity can be observed. This may be attributed to the small particle size, high dispersion of palladium particles. The results imply that the Pd Gold-bead electrodes composites have good potential application clinical diagnostics and certain environmental applications.II Synthesis of Dendrimer-Encapsulated Palladium Nanoparticles and its use for Electrocatalytic oxidation of formaldehydePAMAM dendrimers are good stabilizers and templates, with palladium ions through covalent obtained PAMAM-Pd composite nanoparticles. In this paper we use PdCl2 as raw material, sodium borohydride as reducing agent, PAMAM as template and stabilizer, produced particle size distribution in the range of about 4-5nm Pd-PAMAM composite nanoparticles. It was found that under the condition of pH 3 and 1 hour stiring, when the ratio of PdCl42- to PAMAM is 40,NaBH4 to PdCl42- is 20, the resulting Pd-PAMAM nanocomposites were stable and showed a narrow distribution size. And the oxidation of Pd-PAMAM is reversible. We modified the prepared nanocomposites on glassy carbon electrode and gold electrode successfully. Formaldehyde was found to be electrocatalytically oxidized on the Pd-PAMAM modified electrodes.III The Preparation of Pd-PAMAM-MWNTs/GC Modified Electrode and The Research of Its Electrocatalytic Properties On the basis of word in section III, we convalently linked COO--MWNTs with PdCl42--PAMAM nanocomposites, and modified them on the surface of glass carbon electrode. The result showed that the sensitivity, stability and current signal have been greatly improved. The process of the modification have be investigated by CV, TEM and XRD. The catalytic properties of the modified electrode has been studied, too. Hydrazine was found to be electrocatalytically oxidized on the modified electrode. The current value was lined with the concentration of Hydrazine in the concentration ranging from 4.0×10-4M to 1.6×10-3M. The detection limit is 2.4×10-4M. We also found that H2O2 can be electrocatalytically reduced on the Pd-PAMAM-MWNTs modified electrode.VI Preparation and characterization of AgI nanoclusters with PAMAM dendrimers with a trimesyl core(DT)as templatePAMAM dendrimers with a trimesyl core (DT) were used as templates in preparing AgI nanoclusters. The influence factors in the process of AgI nanoclusters prepared were investigated. The terminated groups of PAMAM dendrimers, the molar ratio of silver ions to PAMAM dendrimers and the reaction time are proved to play an important role in the size of prepared AgI nanoclusters. UV-Vis spectrophotometer, fluorescence spectrophotometer and TEM were used to characterize the obtained AgI/DT dendrimer nanocomposites. Under the neutral conditions, the fluorescence intensity of DT4.5 dendrimers is strong, and it obviously decreased after Ag+/DT4.5 was obtained. Further decrease happened when AgI/DT4.5 was obtained and a new fluorescence peak of AgI appeared at the same time. When the ratio of silver ions to DT 4.5 is 30, the resulting AgI nanoclusters were stable and showed a narrow distribution size. This was result of the innertemplate of DT4.5.

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