Biotemplate-Guided Self-Assembly of Gold Nanoparticles with Plasmonic Circular Dichroism

Cholesteric assembly of plasmonic nanoparticles promotes applications in optics and sensing due to their inherent chiro-optical responses and strong interaction with light. Template-assisted colloidal assembly is a promising route to achieve such structures, yet it often suffers from difficulties in maintaining template integrity and attaining the required particle concentration. In this proof-of-concept work, we report the plasmonic activity of gold nanoparticles (AuNPs) coupled with circular dichroism, achieved through in situ cyclic deposition onto cholesteric biotemplates derived from prawn shells. Upon aging, the samples exhibited clear circular dichroism in both reflection and transmission under left- and right-circularly polarized light. These optical signatures confirm macroscopic coupling between the cholesteric periodicity of the biotemplate and the localized surface plasmon resonance (LSPR) of the AuNPs. High-resolution imaging further revealed handed arrangements of the nanoparticles within the membrane structure. Together, these findings offer a scalable and effective route for engineering chiral plasmonic materials using cholesteric templates.