Construction of Asymmetric Graphene Sandwiches: Decoration Using Semiconductor and Metal Nanostructures

The low-dimensional carbon materials, i.e. graphene-based metal and metal oxide nanocomposites fabrication procedure at the polarizable organic/water interface opens an alternative way to prepare catalyst materials.^1-2 These graphene-based nanostructures could be useful substrates for catalytic processes, such as the hydrogen evolution or the oxidation of low molecular weight alkanes to liquid alcohol fuels. The polarizable organic/water interface offers the possibility of incorporating, as well as constructing in situ at the interface, highly complex catalytic centers and supports, including photoactive semiconductors, metallic nanostructures.³

Chemical vapor deposition (CVD) on copper foil was employed to grow macroscopic (cm scale) graphene and the high purity CVD GR monolayers assembled at an polarizable organic/water interface.^1-2 The semiconductors, titanium oxide (TiO₂) and molybdenum disulfide (MoS₂) were exfoliated in an organic solvent, and assembled at the interface, then the top of CVD GR was decorated by fishing out either the TiO₂ or MoS₂ layer. The top-side of CVD GR was also decorated by metal and metal oxide nanoparticles (NPs), i.e. Au, Pd, Pt and PdO, PtO, respectively, using a solution chemistry-based galvanic displacement.¹ In situ electrochemical and spontaneous, electroless metal deposition of Pd, Pt, Au and Ag NPs at the interface-assembled previously top-side decorated CVD GR was studied.^1-2

We have fabricated a range of different dual-decorated CVD GR-based nanostructures, including semiconductors, metals and metal oxides on top, and metal NPs on bottom-side, respectively. Either the same nanostructures (symmetric decoration), or different ones (asymmetric decoration) were used for the preparation of bi-functionalized graphene sandwiches, which are adsorbed at the organic/water interface. The successful fabrication of such dual-decorated graphene-based metal nanocomposites was confirmed using various microscopic techniques (scanning electron and atomic force microscopies) and several spectroscopic methods (X-ray photoelectron, 3D energy dispersive X-ray tomography, mapping mode Raman spectroscopy and electron energy loss spectroscopy). Taken together it is inferred from these techniques that the location of deposited nanoparticles is on opposite sides of the graphene monolayer.

 

1. Toth, P. S.; Velický, M.; Ramasse, Q. M.; Kepaptsoglou, D. M.; Dryfe, R. A. W., Advanced Functional Materials, 2015, DOI: 10.1002/adfm.201500277.

2. Toth, P. S.; Ramasse, Q. M.; Velický, M.; Dryfe, R. A. W., Chemical Science, 2015, 6, 1316-1323.

3. Rodgers, A. N. J.; Booth, S. G.; Dryfe, R. A. W., Electrochemistry Communications, 2014, 47, 17-20.