Recently, a research group led by Prof. Yi Gaoat the Institute of Water Science and Technology, Shanghai Institute of Applied Physics and collaborators have developed a universal model GUM(Grand Unified Model) to explain the structural stabilities and growth mechanism of liganded gold nanoclusters. This work has been published in Nature Communications. (A grand unified model for liganded gold clusters, Nat. Commun. 7, 13574 doi: 10.1038/ncomms13574 (2016)).
As we all know, "Octetrule" is the basis of modern chemical theory, and is the cornerstone to understand and explain the structural stabilities and the physical and chemical properties of the molecular structuresof the main group of elements. The subsequent development of the "18 electron rule" and "Wade’s rule" in the 20th century has also been a great success, and become the basic chemical theory to understand the transition metal molecules and small sized clusters. However, with the great progress of nanotechnology in recent 20 years, whether traditional chemical theory is still applied at the nanoscale has attracted wide attention. Especially for the metal nanoclusters, so far it is generally believed that these nanoparticles areformed by one metal atom after another with a random growth, and does not obey a universal chemical rule.
For a long time, liganded gold nanoclusters have attracted extensive attention due to their unique structure and physicochemical properties, as well as their wide applications in catalysis, nanotechnology and biomedicine. In the recent 10 years, with the success of crystallization of a series of large sized gold nanoclusters, attempts have been made to explain the structural stability of the gold nanoclusters, but they have not been generally successful. Dr. WenwuXu and Dr. BeienZhu at the Shanghai Institute of Applied Physics, under the guidance of Prof. Yi Gao, cooperated with Prof. Xiao Cheng Zeng at the University of Nebraska at Lincoln and the University of Science and Technology of China, established a universal model to achieve a basic understanding of all the 71 ligand gold nanoclusters reported so far. The model considers that each gold atom has three different valence states, and three or four gold atoms can satisfy the electronic states with two electrons shell closure, which constitute the basic structural unit (triangular Au3 and tetrahedral Au4). When these basic units are stacked together, stable gold nanoclusters with different structures are formed. The establishment of the model strongly proves that the structure and growth of gold nanoclusters follow the basic chemical laws, which opens a new way for the further understanding of metal nanoclusters besides gold nanoclusters. Since this model is very similar to the basic particle model in particle physics, such as quarks have different "flavor", three quarks constitute neutron and proton, and further constitute the nucleus and atoms, it is termed Grand Unified Model. The researchers used the model to predict a series of highly stable gold clusters, which provides a basis for the realization of controlled synthesis of nano-gold clusters based on chemical rules.