2.3 Material characterization
The as-prepared materials were characterized by scanning electron
microscopy (SEM, Quanta 200F), transmission electron microscopy (TEM,
FEI F20), elementary analysis (Vario MICRO Cube CHNS analyzer), X-ray
diffraction (XRD, Bruker D8 Advance),X-ray photoelectron spectroscopy
(XPS, PHI Quantera Scanning X-ray Microprobe) and Raman spectroscopy
(Renishaw RM2000, at 633 nm).