Two-Dimensional Nanoassemblies from Plasmonic Matryoshka Nanoframes

Two-dimensional (2D) plasmonic nanoassemblies are programmable ultrathin materials that one can, in principle, adjust the size and shape of their constituent building blocks to fine-tune collective optical, electrical, and mechanical properties. Here, we report a new 2D nanoassembly from structurally complex plasmonic building blocks, namely, matryoshka-like gold (Au) nanoframes. Using a seed-mediated alternating deposition of Au and silver (Ag) elements in conjunction with a selective etching process, we obtain monodisperse matryoshka-like Au nanoframes with a nesting number (N-n) of up to 5. A cubic nanoframe displays dominant intraplasmonic coupling attributed to bonding and antibonding dipolar modes, which shift to blue and red, respectively, with an increased N-n. Combined with polystyrene (PS) ligand exchange and drying-mediated self-assembly, the approach mentioned above can be used to produce 2D plasmonic matryoshka nanoassemblies. Both experimental and simulation results demonstrate the presence of intra- and inter-ridge plasmonic coupling in the nanoassemblies. The 5-nested nanomatryoshka assemblies exhibit a Raman enhancement 14-fold greater than those with 1-nested cubic nanomatryoshka, demonstrating the dominant intraridge hot spot effects. Taking advantage of interparticle distance-dependent optical transparency of 2D matryoshka nanoframe assemblies, we further demonstrate temperature-enabled encryption/decryption using thermoresponsive polymers.

Automated summary

The study presents a new 2D plasmonic matryoshka nanoassembly composed of structurally complex gold nanoframes, demonstrating unique optical and mechanical properties. By utilizing a seed-mediated alternating deposition and selective etching process, monodisperse nested gold nanoframes can be obtained, showing prominent plasmonic coupling effects.