Full atomistic molecular dynamic -MD- simulations and quantum mechanics -QM- calculations were carried out to investigate the aggregation process of the pure and functionalized gold nanoparticles -AuNPs-. On the basis of the obtained results, pure AuNPs are not stable in water, while 1‑-2‑mercaptoethyl-‑1,3,5‑triazinane‑2,4,6‑trione -MTT- functionalized gold nanoparticles -MTT-AuNPs- show a considerable stability in water. MTT groups change the surface properties of AuNPs and increase their resistance against aggregation. Moreover, MTT-AuNPs have an interesting ability for selective detection of melamine in the presence of different analytes, due to hydrogen bond formation of NH⋯N and NH⋯O. Moreover, electrostatic interactions are the driving force of the selective detection of melamine by MTT-AuNPs. A good agreement between the theoretical and experimental results confirms the ability of the theoretical methods for simulating the complex systems and designing new sensors based on the functionalized AuNPs.

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