The crystalline pattern of Ag species was analyzed by X-ray diffraction (XRD) using an XTRA X-ray diffractometer (Rigaku Inc., Tokyo, Japan). The XRD pattern was obtained using CuK αradiation with an incident wavelength of 0.1542 nm under a voltage of 40 kV and a current of 30 mA. X-ray photoelectron spectroscope (XPS) was carried on the Thermal Scientific ESCALab 250Xi using 200 W monochromatic Al K αradiation. Both survey scans and in- dividual high-resolution scans for Ag (3d), N (1s), O (1s) and C (1s) peaks were measured. All the experimental data were analyzed by