Talanquer V
Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
J Chem Phys. 2006 Nov 21;125(19):194701. doi: 10.1063/1.2370872.
We use decorated-lattice models to explore the phase behavior of two types of DNA-linked colloidal mixtures: systems with identical nanoparticles functionalized with two different DNA strands (mixture Aab) and mixtures involving two types of particles each one functionalized with a different DNA strand (mixture Aa-Ab). The model allows us to derive the properties of the mixtures from the well-known behavior of underlying spin-n Ising models with temperature and activity dependent effective interactions. The predicted evolution of the dissolution profiles for the colloidal assemblies as a function of temperature and number of single DNA strands on a nanoparticle M is in qualitative agreement with that observed in real systems. According to our model, the temperature at which the assemblies dissolve can be expected to increase with increasing M only for concentrations of colloids below a certain threshold. For more concentrated solutions, the dissolution temperature is a decreasing function of M. Linker-mediated interactions between Aa and Ab particles in the Aa-Ab mixture render the phase separation involving disordered aggregates metastable with respect to a phase transition between a solvent-rich and an ordered phase. The stability of the DNA-linked assembly is enhanced by the ordering of the colloidal network and the ordered aggregates dissolve at higher temperatures. Our results may explain the contrasting evolution of the dissolution temperatures with increasing probe size in Aab and Aa-Ab mixtures as observed experimentally.
我们使用装饰晶格模型来探索两种类型的DNA连接胶体混合物的相行为:一种是具有用两种不同DNA链功能化的相同纳米颗粒的系统(混合物Aab),另一种是涉及两种类型颗粒且每种颗粒用不同DNA链功能化的混合物(混合物Aa - Ab)。该模型使我们能够从具有温度和活性依赖有效相互作用的基础自旋 - n伊辛模型的已知行为中推导出混合物的性质。预测的胶体聚集体溶解曲线随温度和纳米颗粒上单个DNA链数量M的变化与实际系统中观察到的情况在定性上是一致的。根据我们的模型,只有在胶体浓度低于某个阈值时,聚集体溶解的温度才有望随着M的增加而升高。对于更浓的溶液,溶解温度是M的递减函数。Aa - Ab混合物中Aa和Ab颗粒之间的连接体介导相互作用使得涉及无序聚集体的相分离相对于富溶剂相和有序相之间的相变是亚稳的。DNA连接聚集体的稳定性通过胶体网络的有序化得到增强,并且有序聚集体在更高温度下溶解。我们的结果可能解释了实验观察到的Aab和Aa - Ab混合物中溶解温度随探针尺寸增加的对比演变。