Plasmon-enhanced chirality sensing platform: chiral polymer (PHEMA) grafted with plasmonic nanocrystals (silver...

A Raman sensing platform composed of plasmonic nanocrystals (silver nanocubes, AgNCs) and chiral polymers (hydroxyethyl methacrylate, PHEMA) utilizes the excellent plasmonic response of AgNCs and the chiral properties of PHEMA to detect chiral molecules using Raman spectroscopy. The sensing performance of such platforms (such as selectivity and detection limit) can be studied using the following parameters: PHEMA graft density on AgNCs, PHEMA tacticity, plasmon-induced chirality, etc. In circular dichroism (CD) detection, the chirality of the PHEMA-AgNC sensing platform changes with the arrangement of PHEMA (graft density) on AgNCs and the tacticity of PHEMA. However, the detection selectivity of such platforms is highly dependent on the arrangement of PHEMA molecules on AgNCs. Even for highly chiral platforms, the intermolecular hydrogen bonding between PHEMA molecules reduces the active sites for PHEMA-analyte interaction, thereby inhibiting detection selectivity. When plasmon-induced chirality is generated on the platform, the detection selectivity can increase by about 2 times compared to when this effect is not present. The structural compatibility between PHEMA and the analyte molecular structure can affect the platform's selectivity for detecting chiral molecules. This type of platform has a detection limit of approximately 10^-8 M for chiral molecules, consistent with results reported for SERS-based devices. These results provide a pathway for designing highly sensitive and selective Raman sensing platforms for detecting chiral molecules that achieve this by combining plasmonic nanocrystals with chiral materials to allow plasmon-induced electromagnetic fields and chiral effects to overlap.