The reference for fitting the peaks was taken from the International Centre for Diffraction Data PDF-4 + 2009 database. The wavelength for all of these databases was chosen to be the same as the wavelength of the synchrotron radiation used. The diffraction peaks shown in Fig. 8 belong to monoclinic WO3 (PDF file 00-043-1035). These results indicate that both the micro-sized WO3 and the nano-sized WO3 were single-phase pure without impurities.