Theoretical Study On The Structure And Properties Of Ligand-Stabilized Low-Dimensional Gold Nanomaterials

Low-dimensional gold nanomaterial?such as gold clusters,gold nanorods?wires?and gold nanosheets?have unique electrical,optical,and catalytic properties that are different from bulk materials.They have always been the focus of many researchers.A large number of studies have found that there are obvious structural and natrue similarities between many Au_m?SR?_n clusters.However,there is no unified view about the questions that how do gold nanoclusters grow into larger-sized gold nanosuperstructures,and how are their electronic and optical properties?Solving this problem is the key to promoting the development and application of gold nanomaterials.The main research contents of this paper are as follows:?1?Based on the same family of FCC-type clusters Au₂₈?SR?₂₀,Au₃₆?SR?₂₄,Au₄₄?SR?₂₈,and Au₅₂?SR?₃₂,we have theoretically predicted multiple series of FCC structure which one dimensional growthing along the crystal[100]or[010]direction.We have studied the structure,structure evolution,electronic properties and optical properties of these series of gold nanostructures.The results show that the energy barrier decreases gradually with the increase of the aspect ratio of the cluster.The energy barrier of one-dimensional infinitely long gold nanowire still remains a certain value,indicating semi-conductivity.With the increase of the aspect ratio of the cluster,the characteristic absorption peak appears to move to the near-infrared region,which is consistent with the trend of the longitudinal plasmon resonance absorption peak experimentally.In this paper,the 2D superclusters originated from Au₂₈?SR?₂₀ and Au₃₆?SR?₂₄4 is also constructed.Few studies have previously extended the variation and influencing factors of the optical properties of two-dimensional structures.The results show that the feature absorption peaks of isotropic 2D Au_m?SR?_n shift significantly to the near-infrared region.It is believed that the optical properties of 2D clusters mainly originate from a substantial increase in the ratio of width to thickness.In addition,the results indicate that the thiolate-ligand are also a key factor in the generation of absorption peaks in the near-infrared region of the 1D and 2D clusters.?2?In order to explore the electronic properties of gold nanosuperstructures,different sizes of 1D and 2D periodic gold nanostructures are constructed.For example,FCC-type two-layer structure protected by thiolate-ligand,the infinitely long structures from gold nanowires to gold nanobelts to gold nanosheets always maintain certain semiconductivity.As the number of layers increases,the semiconductor properties gradually weaken until it becomes completely metallicity.This is because the thiolate-ligand exerts a regulatory effect on the properties of the surface gold atoms.In addition,the effect of thickness on CO oxidation reaction activity was studied by using two-dimensional gold nanosheets containing FCC-type core as catalysts.The results showed that the four-layer thiolate-protected gold nanosheets possese the highest activity for CO oxidation.The structure evolution pattens of small-sized fcc-type gold cluster seeds growing along the 1D and 2D directions was revealed theoretically.At the same time,we proposed the effect of thiolate-protedcted on the optical properties of gold nanostructures.In addition,the size-electronic properties relations of FCC low-dimensional gold nanomaterials is revealed,and the catalytic activity of FCC-type gold nanosheets with different thicknesses were also studied.The results will provides important theoretical value for the experimental and theoretical development of Low-dimensional Gold Nanomaterials.