| AVS 59th Annual International Symposium and Exhibition | |
| Graphene and Related Materials Focus Topic | Thursday Sessions |
| Session GR-ThP |
| Session: | Graphene and Related Materials Poster Session |
| Presenter: | K. Yamazaki, Yokohama National University, Japan |
| Authors: | K. Yamazaki, Yokohama National University, Japan T. Ogino, Yokohama National University, Japan |
| Correspondent: | Click to Email |
Graphene is two-dimensional honeycomb lattice of carbon atoms. It is well known that the graphene sheets are strongly affected by their environment because of its extremely small thickness and large specific surface area. There are many reports about the chemical doping into graphene films induced by the support substrate and charge transfer. In this paper, we studied control of chemical doping to graphene flakes through the substrate engineering and using raman spectroscopy. We also demonstrate the selective adsorption of biomolecules toward the unique sensors.
We used sapphire surfaces for support substrates of graphene. After the acid treatment, the sapphire surfaces are terminated with hydroxyl groups, which work as adsorption sites of water molecules. We deposited graphene flakes on sapphire (0001) and (1-102) surfaces by mechanical exfoliation method. To reveal influence of a water layer at the interface between the sapphire surface and graphene, we annealed the sapphire surfaces at 700℃ for 1h just before graphene deposition and compared the G-peak and 2D-peak positions on Raman spectra.
We observed shift of G-peak and 2D-peak positions to wave numbers lower than those on the hydrophilic sapphire (0001) substrate. But, in the case of (1-102) surfaces, the G-peak and 2D-peak positions did not shift upon annealing. The peak positions are almost same among the annealed (0001), the annealed (1-102), and the on-annealed (1-102) surfaces. It is well known that formation of water layers on sapphire surfaces depends on plane directions1). A (0001) surface has more bound water molecules than the other faces. Therefore, the peak shifts were induced by the amount of water layer that existed at the interfaces between the sapphire surfaces and the graphene flakes. We demonstrated the adsorption of protein molecules on these surfaces. We used ferritin molecules, which are negatively charged for adsorption on the graphene flakes. We observed well-correlated adsorption pattern with the G-peak and the 2D-peak positions of Raman spectra. Ferritin molecules were preferentially adsorbed to the graphene flakes that were supported by hydrophilic (0001) surfaces. Amount of adsorbed ferritin molecules to the other surfaces were dramatically small. These different adsorption behaviors directly show the effect of chemical doping from the interfacial water molecules to the graphene flakes.
In summary, we demonstrated control of protein adsorption to the graphene surfaces by using the suitable support substrates for graphene towards the biosensors without any labeling to substrates and targets.
1) T. Tsukamoto et al. J. Phys. Chem. C (2012) 116, 4732-4737.