The crystal structure of the samples was investigated using X-ray diffraction analysis (XRD, Rigaku X-ray diffractometer) with Cu Kα radiation. The morphologies and elemental compositions of as-prepared samples were examined by field-emission gun scanning Erlotinib Hydrochloride microscope (FEG-SEM, FEI Inspect F50) equipped with an energy-dispersive X-ray spectroscope (EDS). Transmission electron microscopy (TEM) analysis was conducted on a FEI Tecnai F20 with a field emission gun and an accelerating voltage of 200 kV. XPS studies were carried out using a PHI 5000 VersaProbe spectrometer (UlVAC-PHI), employing Al Kα as the incident radiation source. The C1s (E = 284.5 eV) level was served as the internal standard. The N2 adsorption-desorption curves at liquid nitrogen temperatures (77.3 K) were measured on Micromeritics ASAP 2010 instrument. Fourier transform infrared spectra (FT-IR) were recorded at room temperature using a NEXUS 870 FTIR spectrometer (Nicolet). Raman measurement was carried out on a Horiba Jobin Yvon LabRAM HR 800 micro-Raman spectrometer with 514 nm excitation source at room temperature. The UV–vis absorption spectra of as-prepared solid samples were measured on Varian Cary 50 UV–Vis–NIR spectrophotometer via diffuse reflectance spectrum (DRS) mode, and pure BaSO4 was employed as a reference.