Construction and evolution mechanism of hierarchical silver clusters
Faculty of Sciences, Ordzhonikidze, 3, hall 2 (room 708),
Lector — prof. Di Sun (State Key Laboratory of Crystal Materials, Shandong University, People’s Republic of China).
Clusters are polynuclear aggregates situated between atomic/molecular and macroscopic matter, possessing a defined atomic composition and chemical structure. They represent the nascent state of condensed matter and serve as ideal models for understanding the relationship between microscopic structure and macroscopic properties of correlated materials, with significant implications for a profound understanding of material transformation laws. Among the numerous elements capable of forming clusters, coinage metal elements are widely employed in constructing metal clusters with diverse structural types and functionalities due to their unique electronic configuration, coordination habits, and metalophilic properties. Compared to gold and copper, silver ions exhibit diverse coordination configurations and moderate silver∙∙∙silver interactions, endowing silver clusters with a richer variety of structural types and structural dynamics. Simultaneously, silver clusters have greater stability and lower costs than copper clusters, making them a hot topic in the field of metal clusters.
Despite numerous research groups both domestically and internationally achieving fruitful results in this field, the synthesis methods of silver clusters lack universality, making it difficult to establish a comprehensive database of silver cluster structures and making the study of their optical, electrical, and catalytic properties even more challenging. Additionally, the diversity of silver cluster structural types results in varying growth mechanisms for their cores and dynamic shell evolution, lacking a systematic understanding of the underlying principles. Understanding the growth mechanism of silver clusters can provide feedback to guide their controllable synthesis, while the dynamic structural mechanisms of silver clusters will provide a basis for understanding their inherent stability, chemical reactivity, and catalytic activity.
The presenter, based on silver cluster synthesis chemistry, has constructed a database comprising over 200 examples of core/shell hierarchical silver clusters, focusing on a systematic and in-depth study of the critical scientific questions surrounding the growth and dynamic structural mechanisms of silver clusters. They have established a universal nucleation/hardening synergy strategy, achieving the controllable synthesis of core/shell hierarchical silver clusters. This strategy captured and characterized a variety of nascent silver core structures of different sizes, deriving an approximate mathematical relationship between the number of negative charges of the anion group and the core size of silver clusters. The presenter revealed the “polyhedral fusion” mechanism for small core sizes and the “layer-by-layer nesting” growth mechanism for medium to large core sizes. They introduced new methods for the study of complex silver cluster dynamic structural mechanisms (tracking of reaction processes, capturing intermediate single-crystal structures through gradient low-temperature crystallization, etc.), revealing the dynamic nature of silver cluster interface structures. This led to the synthesis of interconversion between clusters and the establishment of a relevant transformation mechanism called “core-shell cooperative expansion.”
Participants: students, postgraduates and scientific-pedagogical workers of the faculty of Sciences of RUDN and other Universities