2.5. Characterization of Structure and SERS

SEM characterizations were performed on a JEOL-6500F (JEOL LTD., Tokyo, Japan) scanning electron microscope with an acceleration voltage of 15 kV. X-ray diffraction (XRD) patterns were obtained using a Rigaku D/MAX 3C X-ray diffractometer (Rigaku Corporation, Tokyo, Japan) with Cu Kα radiation. Raman spectra were measured with a Renishaw Raman system at a laser wavelength of 633 nm. The laser beam was focused on the sample at 50 × long-range objective for characterization. The signal acquisition time was set to 10 s. Ultraviolet-visible (UV-Vis) spectra were measured by a SHIMADTU ultraviolet spectrophotometer (UV-3600).