The investigation of gold nanoparticle (AuNP) aggregation at the atomic level is a great challenge from the experimental view, while theoretical methods facilitate our understanding of the AuNP aggregation process. In this article, by applying full atomistic molecular dynamics simulations, the aggregation process and the stability of the functionalized AuNPs with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AT) was investigated. Moreover, the ability of AT–AuNPs toward selective detection of dopamine was analyzed. Theoretical results showed that AT groups on the surface of the AuNPs increase the resistance of nanoparticles against the aggregation. Also, AT–AuNPs are only accumulated in the presence of dopamine in a mixture of different analytes. In this process, dopamine acts as a molecular bridge between the AT–AuNPs, which facilitates nanoparticle aggregation through hydrogen bond interactions. Quantum chemistry calculations confirmed that the structural feature of dopamine is a more effective factor in AT–AuNP aggregation than hydrogen bonding. Finally, a comparison between the theoretical results and experimental data showed the capability of the theoretical approach to modeling and designing new efficient sensors based on the functionalized AuNPs.

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