Exploring the atomic structure of 1.8nm monolayer-protected gold clusters with aberration-corrected STEM

Copper nanoclusters: designed synthesis, structural diversity, and multiplatform applications

Atomically precise metal nanoclusters (MNCs) have gained tremendous research interest in recent years due to their extraordinary properties. The molecular-like properties that originate from the quantized electronic states provide novel opportunities for the construction of unique nanomaterials possessing rich molecular-like absorption, luminescence, and magnetic properties. The field of monolayer-protected metal nanoclusters, especially copper, with well-defined molecular structures and compositions, is relatively new, about two to three decades old. Nevertheless, the massive progress in the field illustrates the importance of such nanoobjects as promising materials for various applications. In this respect, nanocluster-based catalysts have become very popular, showing high efficiencies and activities for the catalytic conversion of chemical compounds. Biomedical applications of clusters are an active research field aimed at finding better fluorescent contrast agents, therapeutic pharmaceuticals for the treatment and prevention of diseases, the early diagnosis of cancers and other potent diseases, especially at early stages. A huge library of structures and the compositions of copper nanoclusters (CuNCs) with atomic precisions have already been discovered during last few decades; however, there are many concerns to be addressed and questions to be answered. Hopefully, in future, with the combined efforts of material scientists, inorganic chemists, and computational scientists, a thorough understanding of the unique molecular-like properties of metal nanoclusters will be achieved. This, on the other hand, will allow the interdisciplinary researchers to design novel catalysts, biosensors, or therapeutic agents using highly structured, atomically precise, and stable CuNCs. Thus, we hope this review will guide the reader through the field of CuNCs, while discussing the main achievements and improvements, along with challenges and drawbacks that one needs to face and overcome.

Overcoming bacterial physical defenses with molecule-like ultrasmall antimicrobial gold nanoclusters

The size of metal nanoparticles (NPs) is crucial in their biomedical applications. Although abundant studies on the size effects of metal NPs in the range of 2-100 nm have been conducted, the exploration of the ultrasmall metal nanoclusters (NCs) of ~1 nm in size with unique features is quite limited. We synthesize three different sized gold (Au) NCs of different Au atom numbers and two bigger sized Au NPs protected by the same ligand to study the size influence on antimicrobial efficacy. The ultrasmall Au NCs can easily traverse the cell wall pores to be internalized inside bacteria, inducing reactive oxygen species generation to oxidize bacterial membrane and disturb bacterial metabolism. This explains why the Au NCs are antimicrobial while the Au NPs are non-antimicrobial, suggesting the key role of size in antimicrobial ability. Moreover, in contrast to the widely known size-dependent antimicrobial properties, the Au NCs of different atom numbers demonstrate molecule-like instead of size-dependent antimicrobial behavior with comparable effectiveness, indicating the unique molecule-like feature of ultrasmall Au NCs. Overcoming the bacterial defenses at the wall with ultrasmall Au NCs changes what was previously believed to harmless to the bacteria instead to a highly potent agent against the bacteria.

From Solute, Fluidic and Particulate Precursors to Complex Organizations of Matter

The organization of matter from its constitutive units recruits intermediate states with distinctive degrees of self-association and molecular order. Existing as clusters, droplets, gels as well as amorphous and crystalline nanoparticles, these precursor forms have fundamental contributions towards the composition and structure of inorganic and organic architectures. In this personal account, we show that the transitions from atoms, molecules or ionic species to superstructures of higher order are intertwined with the interfaces and interactions of precursor and intermediate states. Structural organizations distributed across different length scales are explained by the multistep nature of nucleation and crystallization, which can be guided towards functional hybrid materials by the strategic application of additives, templates and reaction environments. Thus, the non-classical pathways for material formation and growth offer conceptual frameworks for elucidating, inducing and directing fascinating material organizations of biogenic and synthetic origins.