Study On The Structure And Structure-activity Relationship Of Au Nano Clusters

In recent years,gold nanoclusters?Au_n?have received extensive attention due to their broad potential applications in catalysis,bioengineering,environmental engineering,and so on,on account of their unique structures,photoelectric properties,and good catalytic activity.By adopting the density functional theory,we make a systematic investigation on the geometry and the electronic structures of Au_n in vacuum and adsorbed on different oxide surfaces,respectively.The main results are shown as follows:?1?It is found that the geometrical structure of Au_n will present a transition from two-dimensional to three-dimensional structure.In three-dimensional case,typical structures include pyramid structure,pyramid-like one,double-layer one,hollow cage one,compact one,fullerene-like one,core-shell one,face-centered cubic one,and stacking fault one.In the case n>32,the stationary structure for Au_n of odd atom number will be mainly stacking fault structure.?2?The average binding energy,the second order energy difference,and the energy gap of frontier molecular orbitals of Au_n show the odd-even oscillations with the atom numbers of the cluster increasing.In addition,Au_n with even number atoms will be more stable than those with neighboring odd number atoms.Also,Au₂₀,Au₃₂,and Au₅₈8 exhibit special stability and have certain magic number effect.?3?The catalytic properties of Au_n will be enhanced when they are adsorbed on certain support.Because of the differences of the electronegativity of the metal in supports,the direction of the charge transfer between the support and Au_n may be different,thus making the different charges appear on Au_n.When absorbed on MgO?001?[TiO₂?101?]surface,Au_n will have negative[positive]charges and have higher catalytic reactivity in oxidation[reduction]reaction.The variation of surface charges caused by the support makes Au_n possess different catalytic activity in different systems.?4?When Au_n are adsorbed on the support surface,the electronic structure of the support will make an obvious influence on the p and d density of states of the Au_n,which should be the intrinsic reason that induces the variations of the geometric structures and properties.The research results in this thesis may provide the theoretical reference and data support for the design of the structures of Au_n catalyst,as well as further studying its stability and catalytic properties.