This study reports the synthesis of Au dodecahedral-walled nanoframes, featuring elongated hollow structures with four rectangular plates on the sides and open-frame ends, designed for near-field focusing and efficient gaseous analyte detection when combined with Raman spectroscopy. The nanoframes, synthesized through shape transformation of Au nanorods, facet-selective Pt growth, and selective etching, exhibit an attomolar detection limit for benzenethiol due to their flat terraces, sharp edges, and open frames that enhance surface area, electromagnetic field collection, and analyte transport. These nanoframes demonstrated 20 times higher sensitivity than solid counterparts in detecting mustard gas simulants, representing their potential for chemical warfare agent detection. 

A synthesis method was developed for Au double-walled nanoframes, where single-walled truncated octahedral nanoframes with open (111) facets and solid (100) planes are nested in a core-shell structure. By controlling the face-to-face nanogaps between the inner and outer frames, enhanced electromagnetic near-field focusing was achieved, generating hot zones verified through surface-enhanced Raman spectroscopy. These nanoframes demonstrated superior near-field enhancement for detecting both strongly and weakly adsorbing analytes, enabling effective gas-phase detection of chemical warfare agents, addressing critical challenges in early warning systems. 

This study presents the synthesis of three-dimensional plasmonic nanolenses, termed Au octahedral nanosponges, featuring nanoporous sponge-like networks within their interior. The porous domains enhance scattering and absorption of light, transferring optical energy to the nanospheres at the vertex for maximized near-field focusing, an effect described as the "lightning-sphere effect." These nanosponges achieved a detection limit of 10 ppb for weakly adsorbing analytes in the gas phase and enabled successful Raman detection of nonadsorbing species when combined with metal–organic frameworks as gas-adsorbing intermediates.