Nanorings are an intriguing nanoscale structure due to their unique physical properties. However, relatively large elliptical nanorings could so far not be fabricated.

Yong-Jun Li and colleagues, Hunan University, Changsha, China, have prepared comparatively large elliptical AgAu nanorings by splitting single Ag nanowires along their longitudinal axes (pictured). The synthesis involves a self-assembly of Ag nanowires at an oil/water interface, followed by a galvanic replacement between the Ag nanowires at the interface and AuCl₄ in the water phase.

The resulting AgAu nanorings have rough surfaces, which leads to enhanced catalytic performance towards the reduction of p-nitrophenol. The formation of the nanorings is mainly attributed to the local nanomasking of Au atoms and the asymmetrical etching of the Ag nanowire at the interface. According to the researchers, this new etching mechanism broadens the understanding of interfacial reactions involving nanoparticles and also provides a method to guide the etching of other nanostructures.

• Transformation of single Ag nanowires into super-large AgAu elliptic rings via a water/oil interface-oriented asymmetrical etching,
  Wen-Chao Geng, Wen-Jin Shen, Huan-Huan Xue, Ji-Long Sang, Lin-Nan Zhou, Xia Yin, Yong-Jun Li,
  ChemNanoMat 2018.
  https://doi.org/10.1002/cnma.201800473