包裹有机链的银纳米粒子一维二维阵列的分子模拟研究

Molecular dynamics simulation on the one- and two- dimensional arrays of the silver nanoparticles passivated by organic chains

通过含贵金属纳米粒子的一维、二维有序阵列,可以制备纳米线和纳米膜。利用Materials Studio软件构建了由87个银原子内核化学吸附22根含苯不对称硫醚链(TTOE)形成的含银纳米粒子,在不同的间距条件下构建一维和二维阵列模型。首先考察了模型中链及苯环间相关关系受温度及阵列参数的影响情况。相关性由相关性判据界定。经分析,选用了平行次序参数大于0.6、垂直次序参数小于-0.3以及苯环质心间距小于1.0nm的一组判据。相关性分析结果表明,当温度升高至600K时,所有11个模型中链及苯环间相关性几近消失,说明较高温度下,此纳米粒子及其阵列可能不太适合作为纳米电子器件使用。在升温过程中,间距为4.8nm的一维纳米粒子阵列相关性保持较好,而二维则出现在较大间距情况下。其次,考察了模型中TTOE链平均头尾距(可视为链长,反映链伸展情况)受温度及阵列参数影响情况。模拟结果表明,较低温度下链的平均头尾距随纳米粒子间距减小而增加,而在较高温度下链则呈现出不同的伸展情况,转换区间在(500～600)K之间,这与链及苯环间相关性几近消失的区间相一致。产生这一现象应该是链包裹层能量效应和空间效应共同作用的结果。

Nano-wire and nano-film can be obtained by ordered arrays of precious metal nanoparticles in one-dimension and two-dimension.In this work,the models of one-and two-dimensional array of the title nanoparticle with different spacing were constructed by Materials Studio software. The nanoparticle is formed by 22 thiol-terminated asymmetric hydroquinonyl oligoethers（TTOE）chains adsorbed chemically on an inner core of 87 silver atoms.Firstly,the correlation between TTOE chains and the phenyl rings was investigated under different temperature and different array parameter conditions.The correlation is determined by the correlation criterion.The carefully selected criterion group is that,the parallel ordered parameter is greater than 0.6,the vertical ordered parameters is less than-0.3,and the distance from different phenyl rings is less than 1.0 nm.The analysis results to the correlation revealed that the correlation almost disappeared in all models when the simulation temperature was raised to 600 K, which indicates that the title nanoparticle and its arrays may not be suitable to be used as the nano-electronics device at higher temperature.In temperature elevating process,the one-dimensional array within 4,8 nm spacing distance seemed to be able to keep a better correlation,while it appeared in a larger distance case for two-dimensional array.Secondly,how the mean head-to-end distance of TTOE chains in the model,which can be seen as the chain length and be used to reflect the chain stretching,were affected by the temperature and the array parameters was investigated.The simulation results showed that the mean head-to-end distance increased with the decrease of the spacing distance at the lower temperature,while the different chain stretching situation was observed at higher temperature.The conversion region was from 500 K to 600 K,which was consistent with that of correlation disappearance.This phenomenon should be explained by the combined action of energy effect and steric effect in the chain crown.