Silver nanoplates are two-dimensional nanostructures that interact with visible light. They are promising for applications such as optical probes or contrast agents in biomedical imaging. As their optical properties are shape dependant, synthetic methods that allow reproducible control over shape and size are needed.

Yadong Yin and colleagues, University of California, Riverside, USA, have studied the role of each reagent in the direct chemical reduction route to silver nanoplates from silver salts or metallic silver. They found that H₂O₂ plays the key role in determining the shape instead of the generally believed citrate.

Citrate is required to stabilize the silver nanoplate nuclei through preferential binding to the Ag (111) facets, but can be substituted by many di- and tricarboxylate compounds whose two nearest carboxylate groups are separated by two or three carbon atoms.

NaBH₄ was found to act as a capping agent to stabilize the silver nanoparticles. This prolonged the initiation time required for nanoplate nucleation and gave control of the thickness as well as the aspect ratio of the nanoplates.

• A Systematic Study of the Synthesis of Silver Nanoplates: Is Citrate a “Magic” Reagent?
  Q. Zhang, N. Li, J. Goebl, Z. Lu, Y. Yin,
  J. Am. Chem. Soc. 2011.
  DOI: 10.1021/ja2080345