According to a study published in Nano Letters, researchers from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences have developed an antielectric potential growth method for the large-area preparation of Au-Ag heterodimer arrays. The prepared patterned Au-Ag dimer arrays have nanometer-scale information resolution due to the multipolar coupling resonance between the Au and Ag components.

Localized surface plasmonic resonance effects endow plasmonic nanoparticles (NPs) with the ability to modulate light-matter interactions, enabling patterned plasmonic arrays to encode complex colors and polarization patterns. Among them, the heterogeneous plasmonic arrays composed of periodically arranged heterogeneous plasmonic NPs have multidimensional optical tunability. It is conducive to the realization of high-resolution information encryption.

In this study, the researchers proposed the antielectric potential strategy to realize the in situ growth of Ag NPs on Au nanosphere (NS) array to form the unique Au-Ag dimer array.

Briefly, the Au NSs seed arrays were modified with the 5-amino-2-mercapto benzimidazole ligand to increase the interfacial energy, which was able to overcome the electrical potential resistance between the Au NSs and the substrate for the nucleation of Ag ions. By modulating the kinetic factors, the morphology, size and number of growing Ag NPs can be precisely regulated.

In addition, patterned Au-Ag dimer arrays have been fabricated by electron beam lithography. When the pattern line width is as small as 400 nm, the encrypted information can also be clearly expressed, thus realizing nanoscale information resolution.

This work demonstrates a facile and large-area controllable method for fabricating multidimensional dimer arrays, which promotes the development of plasmonic metal arrays in the field of optical information encryption.

Characterization of Au-Ag dimer arrays. (a-b) Schematic of Au-Ag dimer arrays with different morphologies of Ag NPs. (c-d) SEM images of Au-Ag dimer arrays. (e-f) Dark-field optical images of patterned Au-Ag dimer arrays with line widths of four μm ("USTC" "ISSP"). (Image by ZENG Pan)