| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 103 === Molecular dynamics (MD) simulation was carried out to investigate the structural evolutions of fourth generation polyamidoamine (G4 PAMAM) dendrimer encapsulating different size Au nanoparticles (AuNPs) in both dry and aqueous environments. To ensure the accuracy of the simulation model, a hybrid potential system was applied to describe the interactions between polymers and metals. The conformations and the thermal stability of G4 PAMAM dendrimer covering AuNPs were investigated under a dry environment. We determined that the AuNPs are covered by branched structures and the internal cavities of the G4 PAMAM dendrimers. Moreover, the melting points of the dendrimer-encapsulated AuNPs increase significantly when compared to non-encapulated nanoparticles. To simulate the biological conditions, the conformations and the diffusion behavior of G4 PAMAM encapsulated AuNPs under neutral and low pH conditions (pH ~7 and pH ~5, respectively) were also investigated for studying the effects of solution. The results show that the conformations of dendrimers become more compact when covering the AuNPs at neutral pH; however, when at low pH, the extended conformations can be observed. We also obtained the higher diffusion coefficients of these composites at neutral pH. This study helps clarify the internal conformations and characteristics of PAMAM-AuNP composites, as well as contributing to the designs of catalysts, biosensors and drug carriers.
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