The graphene oxide (GO) and its hydrothermal reduction graphene oxides (r-GO) are studied by Transmission Electron Microscopy (TEM), Raman spectrosocpy, Photoluminescence spectroscopy, Near-edge X-ray Absorption Fine Structure (NEXAFS), and Resonant inelastic X-ray Scattering (RIXS). The structural recovery and removel of oxygen/hydroxyl groups indicate the evolution of carbonaceous specices. The combination of XANES and XES in GO and r-GO shows the overlapping π and π* orbitals in carbon site, but has the 1.1 eV value of band-gap in oxygen site. The oxygen atom in the electron structure and local DOSs within the π and π* gap reflects the energy traps formation through the coupling between O site and C sp2 clusters, which is decreased with the narrowing and shifted PL features. The two-dimensional C Kα RIXS plots with a function of both emission and excitation energies demonstrate the band structure dispersion of the π and σ features near the K point of GO and r-GO. The tunable ability via selecting the working stage of functional group displays the direct modification of occupied and unoccupied state in the photovoltaic and photocatalyst application.
We investigate the position-selected electronic structure of laser modified carbon nanotubes Carbon Nanotubes (CNTs) by scanning photoelectron microscopy (SPEM). After laser pruning removed the top layer of CNTs in air and N2 environment, the modified region shows enhanced chemical shifts of 0.9 and 0.6 eV in carbon 1s state, strongly dependent on the gaseous species. We demonstrate an effective postgrowth process to modify the electronic structure of CNTs for further applications. The challenge is how to connect the electronic structure change of CNTs to the real-space morphology. Our approach toward the nanoscience problem utilizes the visualize probing of the chemical structure in SPEM, Taiwan. We are currently interested in the surface modification of gold-graphene and protein-trypsin system through the unique spatial ability of SPEM for biotechnology and nanotechnology applications.