Gold nanorods (AuNRs) are anisotropic nanoparticles that have attracted great interest because of their unique optical properties and different dimensions that enable applications in sensing, imaging and therapy. Despite several investigations have reported the broad longitudinal surface plasmon resonance (LSPR) band tunability, few of them have focused on the synthesis of small nanorods in high yield. Here, we report a novel, reproducible and scalable protocol for the seedless synthesis of AuNRs with hydroquinone as weak reducing agent and poly(vinylpyrrolidone) (PVP) as additive. The polymer is introduced to growth solutions during synthesis for 100 mM of surfactant cetyltrimethylammonium bromide (CTAB). By using PVP of distinct molecular weights (5-360 kDa), the LSPR band is tuned from 850 to 1010 nm as a function of polymer addition time. Also, the original aspect ratio (length/width) for nanorods with size of 43 x 7 nm is reduced at different extents depending on the polymer molecular weight. It was found that PVP accelerates the growth rate of AuNRs by more than two times as the molecular weight increases. However, only the use of low molecular weight PVP such as 10 kDa produces AuNRs in high yield. The interaction of the polymer to the nanorod surface was determined by attenuated total reflectance (ATR) and X-ray photoelectron spectroscopy (XPS) analysis. It is suggested that PVP interacts with AuNRs through the oxygen atom of the carbonyl group. Moreover, the estimation of the average number of PVP chains per nanorod in solution indicates that around 30 molecules may interact with AuNRs and contribute to their stabilization. Because nanomolar concentration of PVP is utilized, it is expected that the polymer acts less like a reducing agent, as seen in traditional polyol synthesis, but as a templating group to stabilize the growing nanorods.

Management of gold nanorod synthesis with poly(vinylpyrrolidone) of different molecular weights in minor concentration

256th National Meeting (2018)

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