DNA稳定的Ag-Au团簇：合金化和包埋对光学性质的影响
DNA-stabilized Ag-Au bimetallic clusters: The effects of alloying and embedding on optical properties
摘要：
采用全局几何优化和含时密度泛函理论计算方法研究了（AgAu）n（n=2-6）纳米合金的结构演化和光学性质.我们表明，合金化可以用来控制和调整的金属原子的簇和DNA配体的有机片段之间的相互作用的水平。例如，金和银原子在从核碱基到簇的电荷转移过程中表现出协同效应，直接连接到胞嘧啶的氮原子的银原子增加了它们的正部分电荷，而它们的电负性更强的相邻金原子则携带过量的负电荷。这使得小的纳米团簇的几何结构和光学吸收光谱在与相对大的DNA片段（例如基于胞嘧啶的9-核苷酸发夹环）聚集时保留它们的许多主要特征，这表明了这种混合金属-有机化合物的潜在合成路线，并开辟了将纳米合金的独特可调性质带入生物应用的可能性。
英文摘要：
Global geometry optimization and time-dependent density functional theory calculations have been used to study the structural evolution and optical properties of (AgAu)n (n=2-6) nanoalloys both as individual clusters and as clusters stabilized with the fragments of DNA of different size. We show that alloying can be used to control and tune the level of interaction between the metal atoms of the cluster and the organic fragments of the DNA ligands. For instance, gold and silver atoms are shown to exhibit synergistic effects in the process of charge transfer from the nucleobase to the cluster, with the silver atoms directly connected to the nitrogen atoms of cytosine increasing their positive partial charge, while their more electronegative neighbouring gold atoms host the excess negative charge. This allows the geometrical structures and optical absorption spectra of small bimetallic clusters to retain many of their main features upon aggregation with relatively large DNA fragments, such as a cytosine-based 9-nucleotide hairpin loop, which suggests a potential synthetic route to such hybrid metal-organic compounds, and opens up the possibility of bringing the unique tunable properties of bimetallic nanoalloys to biological applications.
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