| AVS 62nd International Symposium & Exhibition | |
| Biomaterial Interfaces | Tuesday Sessions |
| Session BI-TuP |
| Session: | Biomaterial Interfaces Poster Session |
| Presenter: | Shingo Yoneda, Toyo University, Japan |
| Authors: | S. Yoneda, Toyo University, Japan T. Okamoto, RIKEN, Japan H. Vieker, Bielefeld University, Germany A. Beyer, Bielefeld University, Germany A. Gölzhäuser, Bielefeld University, Germany H. Takei, Toyo University, Japan |
| Correspondent: | Click to Email |
There has been an increasing interest in creating silver nanostructures for optical analytical techniques such as surface-enhanced Raman spectroscopy. Galvanic displacement reaction, exploiting the difference in ionization tendency of different metals, can be used for such purposes, but previously there was not much room for controlling the final morphology of nanostructures when bulk metal was simply treated with silver nitrate solution. However, recently it was reported that use of copper colloids rather than bulk copper allows finer structural controls. We have also found that surface-adsorbed copper structures can be transformed to silver nanostructures with various morphologies. The size and amount of copper were crucial for the morphology of the final structures. Recently we have also begun experimenting with addition of polyvinylpyrrolidone (PVP) to the silver nitrate solution because PVP was known to affect the morphology of the silver nanostructures with the conventional galvanic displacement reaction using bulk metal. Here we describe its results.
Our base metal nanoparticles are formed by evaporation of a base metal on surface-adsorbed monodisperse SiO2 nanospheres. Variable parameters are the metal deposition thickness and the nanosphere diameter. We treated these base metal nanoparticles with an aqueous silver nitrate solution containing PVP. In this experiment, we investigated effects of changing the concentration of PVP, the molecular weight of PVP (K15, K30, K90), and the deposition thickness of copper (10, 30, 60 nm). For evaluation of the structures, we observed their morphologies with SEM and obtained Raman spectra of 1 mM rhodamine 6G, R6G.
Use of PVP leads to silver nanostructures with different morphologies. When PVP is used, massive silver nanostructures are formed. When not, however, silver nano-filaments are formed instead. It was also confirmed that the form of silver nanostructres is dependent on the molecular weight of PVP used and the deposition thickness of the original base metal. When these nanostructures are used as a substrate for SERS, the enhancing effect becomes greater when prepared with PVP.