The Study of Gold Nanoparticles: Modification and Preparation
| Autor: | Chia-Hao Su, 蘇家豪 |
|---|---|
| Rok vydání: | 2003 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 In this study, two experiments including (1) pH dependence of Au assemblies formation by hydrogen bonding and electrostatic attraction and (2) the synthesis of gold nanoparticles by sonochemical method have been performed. In pH dependence of Au assemblies formation study, we demonstrated that w-sulfanylalkanoic or w-alkyldisulfanylalkanoic acids can be mixed with Au colloidal solutions to result in functionalized Au colloids which exhibit developed self-assembled architectures by bonding properties as electrostatic and hydrogen-bonding interactions. As the result, Au nanoparticle assemblies resulted from the simple addition of w-sulfanylalkanoic or w-alkyldisulfanylalkanoic acids into sodium citrate contained aqueous Au colloidal solutions and the 2D arrays revealed the characteristics of the coexistence of both electrostatic and hydrogen-bonding attraction at pH 6. At pH 11, Au nanoparticles capped with carboxylate-terminated thiolates could interact with Na+ to lead to aggregates formation via electrostatic interactions in alkaline solutions, but the observed 3D arrays might also be due to coagulation during the dry-up process in the preparation of TEM samples. Under acidic conditions (pH 3), the colloidal solutions exhibited precipitation and suggested the formation of hydrogen-bonding interactions leading to 3D close-packed aggregates. In the synthesis of gold nanoparticles by sonochemical method, a newly modified sonochemical approach was demonstrated to synthesize stable Au suspensions. The formation of Au nanoparticles with diameters of ~ 20 nm was accomplished through the ultrasonic irradiation of aqueous HAuCl4 solutions containing trisodium citrate at 4 ºC. The efficient generation in gold particles only occurred when the sufficient citrate concentrations (＞1.9 mM) were reached. At low citrate concentrations ranging from 0.49 to 1.5 mM, large aggregates of coalesced Au particles were observed as sonication time increased. When the sonication was operated at room temperature, the differential particles formation was observed as compared with the results described at 4 ºC. It was observed that the particles were mainly formed as coagulation domains at 15 min sonolysis while the isolated Au colloids accompanied with aggregates morphology were attained as irradiation extended to 30 min and the prepared Au diameters showed broad distribution and no dependence of citrate dosages in particle sizes. It is proposed that citrate could transform as the reducing radicals, for the AuCl4- reduction and might also act as the stabilizer during particles formation. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|