The Science
Gold nanocrystals are industrial catalysts and are also widely used in diagnostic assays and therapeutics. A recent study revealed a photochemical strategy that enables synthesis of gold nanocrystals with desirable properties.
The Impact
The study reveals a key role for a surfactant called polyvinylpyrrolidone (PVP) in the growth of gold nanocrystals upon exposure to visible light. The findings could be used to optimize properties of gold nanocrystals for specific industrial and medical applications.
Summary
Gold is highly stable and has other attractive features suitable for various industrial and medical applications, but it has been difficult to control the size and shape of single-crystal nanostructures. A team of researchers from the University of Florida, EMSL, the Environmental Molecular Sciences Laboratory, and Brookhaven National Laboratory recently revealed a photochemical strategy that enables growth of gold nanocrystals with controlled properties. The researchers found a high yield of hexagonal or triangular gold nanoprisms can be obtained by mixing organic polymer PVP in an aqueous solution containing gold nanocrystal seeds and tetrachloroauric acid (HAuCl4). To understand underlying mechanisms, researchers probed the spatial distribution of PVP molecules on individual gold nanoprisms using nanoscale secondary ion mass spectrometry at EMSL, an Office of Science user facility. They also used EMSL’s scanning probe atomic force microscope (AFM) compound microscope as well as the dynamic force AFM. Surprisingly, the results revealed PVP preferentially adsorbs onto defects along the perimeter of the gold nanocrystals instead of the top and bottom facets as previously suggested. Upon exposure to visible light, the adsorbed PVP directed photo-excited electrons as they reduced aqueous HAuCl4− ions to add metal to the growing nanocrystal. This study broadens the applicability of this photochemical strategy beyond synthesis of silver-based nanostructures and reveals novel insights into molecular mechanisms driving the growth of gold nanocrystals. The findings could be used to tailor the shape and size of gold nanocrystals for specific industrial and medical applications.
PI Contacts
Wei David Wei
wwei@mail.ufl.edu
University of Florida
Zilua Zhu
zihua.zhu@pnnl.gov
EMSL
Funding
This work was supported by the U.S. Department of Energy’s Office of Science (Offices of Biological and Environmental Research and Basic Energy Sciences), including support of EMSL and Center for Functional Nanomaterials, both of which are Office of Science user facilities, U.S. Air Force, National Science Foundation CCI Center for Nanostructured Electronic Materials, and University of Florida.
Publication
Y. Zhai, J.S. DuChene, Y.-C. Wang, J. Qiu, A.C. Johnston-Peck, B. You, W. Guo, B. DiCiaccio, K. Qian, E.W. Zhao, F. Ooi, D. Hu, D. Su, E.A. Stach, Z. Zhu and W.D. Wei, “Polyvinylpyrrolidone-induced anisotropic growth of gold nanoprisms in plasmon-driven synthesis.” Nature Materials (2016). [DOI:10.1038/nmat4683]