Epoxidized natural rubber (ENR-50) stabilized gold and platinum organosols

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dc.contributor.authorTeoh, Cheng Hoon
dc.date.accessioned2014-11-04T02:55:16Z
dc.date.available2014-11-04T02:55:16Z
dc.date.issued2006
dc.descriptionMasteren_US
dc.description.abstractGold and platinum metal organosols were synthesized in-situ in the presence of ENR-50 via chemical reduction method by employing 2-propanol as the reducing agent. A similar organosols was also prepared via water to toluene phase transfer technique of the preformed particles in aqueous solution by sodium borohydride (NaBH4) reduction of metal ions. For the in-situ preparation, the finest gold and platinum nanoparticles in terms of size, dispersability and stability can be obtained by varying the metal ions concentrations and reaction temperatures. The size of gold nanoparticles decreased with decreasing gold ions concentrations and at higher (reflux) temperature affording the smallest particles of 9.6 nm while the size of platinum nanoparticles decreases with increasing platinum ions concentration and moderate temperature (ca. 80oC) with 1.7 nm particle size obtained. Changes in the reaction temperatures will influence the rate of reduction of metal ions and the hydrodynamic volume of ENR, forming gold particles in the size range of 9.6 to 45.6 nm and for platinum ranging from 1.7 to 173.6 nm. However, for platinum at different concentrations, the smallest particles is only possible when the ENR chain experience partial opening of epoxide ring which occurs at high platinum metal ion concentration thus creating accessibility for the metal to the C=C sites in the ENR chain. Nonetheless, the different affinity of gold and platinum towards C=C contributes to the different size trends obtained for these metals in the in-situ preparation. Smaller gold and platinum nanoparticles in the size range of 4.0 to 7.2 nm with very narrow size distribution can be prepared through the liquid-liquid phase transfer technique. The transfer of the metal nanoparticles from aqueous to organic phase was highly efficient and with very little variation on the size of the nanoparticles before and after transfer. The metals transferred were stabilized by the nano-void exist in the ENR interchains and the stability was further enhanced by the metal complexation to the C=C and epoxide ring of ENR. There is evidence that the metal particles are stripped of the initial stabilizer, citrate, during transfer from aqueous to organic phase due to the better stabilizing capability of ENR compared to citrate in the organic phase. Various morphologies of gold and platinum nanoparticles formed via both methods can be evaluated in terms of the known models. From this research, ENR was a capable stabilizer for gold or platinum nanoparticles obtained from both the in-situ and phase transfer method regardless of the changed in the structure of ENR.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/371
dc.language.isoenen_US
dc.subjectChemical scienceen_US
dc.subjectEpoxidized natural rubberen_US
dc.subjectPlatinum organosolsen_US
dc.titleEpoxidized natural rubber (ENR-50) stabilized gold and platinum organosolsen_US
dc.typeThesisen_US
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