Thermophysical properties and interactions for Au complex nanoparticles in water and salt environment by molecular dynamic simulation

Molecular dynamics provides a computational microscopy tool to visualize the interactionand, at the same time, compute various global physical quantities for subsequent verificationagainst experiments [1,2].Gold nanoparticles are being used extensively in biotechnology and nanosciences, andrevealing the details of their interactions with biological fluids at an atomistic level is highlyregarded. In this work, gold nanoparticles (AuNPs) of 144 Au atoms modeled withfunctionalized alkanethiol side groups (undecanyl chain, R=C11 H22, and a terminal group)[3],is chosen. Two types of Au nanoparticles were prepared: one with a terminal amine group(NH+ 3) and the other with a carboxylic group (COO-) attached to each hydrocarbon chain.The molecular formulas of the corresponding particles can be represented as Au144 (SRNH- 3)60and Au144 (SRCOO-)60 for AuNP+ and AuNP−, respectively. In this work a simulation is donewith Au144 (SRCOO-) in aqueous environment. Previous work carried out by thisnanoparticles only in the presence of one of ions Na+ or Cl- [3] while this research in a rangeof various concentrations of salt and various temperatures is done. The results of thesimulation for one of conditions included 0.1M NaCl and 310K , is presented. Thesimulation box dimensions are adjusted to allocate volume of system to 5 x 5 x 5nm30. Withchoosing Gromos45a3 and the SPC model of water simulation is started. The particle-meshEwald summation (PME) method is used for the electrostatic interactions with a real spacecutoff of 1.0 nm and a reciprocal grid of 42 x 42 x 42 cells with a fourth-order B-splineinterpolation. For van der Waals interactions, we use a cutoff distance of 1.2 nm. Thesimulations are performed both in the NVT and NPT ensembles for 200 ps, respectively. According to the figure (a) mixing in about 1.4 nm of box dimension occurs. Thermophysicalproperties for this simulation and figures are given in the following. Molecularconfiguration of the system shown in Figure (b). Information on minimum energy and selfdiffusioncoefficient for system components is listed in tables 1 and 2.