Polyaniline-Based Rose-like Chiral Nanostructures for Raman Enhancement

Metal-free materials for efficiently enhancing Raman spectrum represent a Frontier in the field of Raman enhancement. Herein, a metal-free Raman enhancement-active material, polyaniline (PANI)-based rose-like chiral nanostructures, which is fabricated by the oxidation polymerization of aniline occurred in a reaction droplet on a glass slide, is developed. The morphology of the as-prepared PANI nanostructures is well designed to rose-like chiral (left-handed or right-handed) nanostructures. Due to the suitable energy level and chiral nanostructure feature, the prepared PANI nanostructures exhibit excellent Raman enhancement performance compared with other metal-free materials. The enhancement factors of the chiral nanostructures are 10 times more than that of achiral nanostructures for dye molecules (e.g., 22.5 times for crystal violet), indicative of significance of the chiral nanostructure to the macroscopic performance. Moreover, the superior reproducibility and generality of the PANI-based rose-like chiral nanostructures illustrate its high potential in Raman enhancement applications. This work not only provides an efficient metal-free platform for Raman enhancement but also develops herein the idea, which is highly instructive for the rational design of advanced Raman enhancement-active materials for broader applications.