Improving the Shape Yield and Long-Term Stability of Gold Nanoprisms with Poly(vinylpyrrolidone)

Gold nanoprisms (AuNPRs) are anisotropic nanostructures that have gained great attention in recent years because of their interesting and unique optical properties that can be tailored for biomedical, energy, and sensing applications. At present, several protocols have reported the high yield synthesis of AuNPRs of different dimensions using a seed-mediated approach. However, there is a need to develop reproducible and scalable methods with the goal of a controllable synthesis. Here, we report an improved seed-mediated synthesis of small monodisperse AuNPRs of distinct sizes in high yield using poly(vinylpyrrolidone) (PVP) as an additive in nanomolar concentrations. We show optimal synthetic parameters for a blue-shifting of the surface plasmon resonance band which correlates with the reduction in the edge length (L) of AuNPRs from 75 to 35 nm. Using measured extinction coefficients for AuNPRs of different sizes, a linear equation is proposed to estimate the concentration of unknown samples by using Beer's law. Interestingly, the use of nanomolar amounts of PVP during the growth of AuNPRs significantly improves the shape yield. The surface chemistry properties of AuNPRs were measured by X-ray photoelectron spectroscopy and attenuated total reflectance infrared spectroscopy and revealed that PVP chains interact with AuNPRs through the carbonyl oxygen. This method is reproducible and scalable and enables the synthesis of AuNPRs with long-term shape stability (1 year) in aqueous solution.