Tecnai g2 f20 s tem

The bright field transmission electron microscopy (TEM) observations were carried out on FEI Tecnai G2 F20 S/TEM at accelerating voltage of 200 kV. The X-ray photoelectron spectroscopy (XPS) was conducted on an ESCALAB 250 X-ray photoelectron spectrometer with a monochromated X-ray source (Al Kα hv = 1486.6 eV), and the energy calibration of the spectrometer was performed using C 1s peak at 5284.8 eV. The powder X-ray diffraction (XRD) patterns were obtained on a Bruker DD8 Advanced diffractometer with Cu Kα radiation (λ=1.5418 Å). Gas chromatography-thermal conductivity detector (GC-TCD) was conducted on an Agilent 6890N Network Gas Chromatograph using argon (Ar) as the carrier gas. Ultraviolet-visible (UV-vis) spectrometry was performed by Agilent Cary 5000 series UV-vis-NIR spectrometer. Fluorescence quenching was performed on VARIAN CARY Eclipse fluorescence spectrophotometer. The PL measurement was performed with either a 405-nm laser or a 325-nm He-Cd laser (Kimmon Koha) as excitation source. Electron paramagnetic resonance (EPR) spectroscopy measurement was performed on a Bruker Elexsys E580 X-band EPR Spectrometer.