X ray photoelectron spectroscopy

The atomic concentration of the PoLfs fiber was measured using an X-ray photoelectron spectroscopy (Thermo Fisher Scientific Inc., East Grinstead, UK) apparatus that had the characteristics of a monochromatic Al-Ka (1486.7 eV) X-ray source and a 300 µm diameter beam. The range used to gather XPS data was 1361–10 eV, with a precision of 0.1 eV and pass energy of 50 eV. Ionic Ar gas was sputtered before the fiber sample was examined on the surface, and 10 scans were made from a single spot to collect the data.

Optical microscope (Motic, Xiamen, China) was used to characterize the morphology. Material composition was characterized by X-ray photoelectron spectroscopy (XPS) (Thermo Fisher, Waltham, MA, USA). X-ray diffraction (XRD) (Bruker, Bilerika, MA, USA) and high-resolution transmission electron microscopy (HRTEM) (FEI, Hillsboro, OR, USA) were applied to characterize microstructure. The electric and photoelectric properties were studied on a four-probe table (SEMISHARE, Shenzhen, China) combined with the 2636B source meter (KEITHLEY, Cleveland, OH, USA). For this, 365, 405, 532, 808, and 1550 nm lasers were applied as the probing light sources.

The synthesized catalysts were analyzed for structural information using an X-ray diffractometer (Panalytical’s X’Pert Pro, Malvern, UK) with a Cukα radiation source. The experiments were performed in the 2θ scanning range of 20–70 degrees with step size of 0.02°. The particle size of catalysts was obtained with the help of a transmission electron microscope (EM-410 LS, Philips, Amsterdam, The Netherlands). The surface morphology of the catalysts was examined using a scanning electron microscope (SEM, Hitachi, Tokyo, Japan). X-ray photoelectron spectroscopy (Thermofisher Scientific, Nexsa base, Waltham, MA, USA) was employed for the determination of elemental presence and their valence states. The metal-stretching vibrations in the synthesized catalysts were performed with the help of a Raman spectrometer (Raman Horiba, Lab RAM HR evolution). The bandgap estimation was performed by analysis of the absorbance spectra recorded using a UV-VIS-NIR spectrophotometer (Perkin Elmer, Waltham, MA, USA). The magnetic properties of the catalysts were investigated using a vibrating sample magnetometer (Micrösense, EV7) to record the room temperature M-H loop at a field strength of 15,000 Oe. Photoluminescence (PL) spectra were recorded on a FS5 spectrophotometer (Edinburgh Instruments, Edinburgh, UK).

The morphology of the as-synthesized WNW and interlayers was investigated using scanning electron microscopy (SEM; Nova NanoSEM 450, FEI, Hillsboro, OR, USA) and transmission electron microscopy (TEM; JEM-2100F, JEOL, Tokyo, Japan). The crystal structures of the obtained products were characterized by X-ray diffractometry (MiniFlex600, Rigaku, Japan) using Cu Kα radiation. The surface area and pore size distribution of the WNWs were measured using a Quantachrome Autosorb iQ MP automated gas adsorption system with liquid nitrogen (at 77 K). X-ray photoelectron spectroscopy (XPS; Thermo Fisher Scientific, Waltham, MA, USA) was used to investigate the surface and chemical states of the WNWs; the binding energy values were calibrated based on the C 1s peak at 284.5 eV.

The structural features of as-prepared materials were analyzed by powder X-ray diffraction (X-ray diffractometer model XRD-6100, Shimadzu, Kyoto, Japan) with CuKα X-ray radiation (λ = 0.15406 nm). The morphological features were examined by scanning electron microscopy (FESEM, Hitachi, S-4800 and HRTEM, Tecnai G2 F20 S-Twin at an accelerating voltage of 200 kV). The elements of active materials were recognized using energy-dispersive X-ray spectroscopy (EDS) attached to the SEM. Sample mappings were obtained using annular dark-field imaging in a scanning transmission electron microscope (STEM) equipped with a high-angle annular dark field (HAADF) detector. The chemical states of the materials were tested using a Thermo Scientific X-ray photoelectron spectroscopy (XPS) instrument utilizing Al Kα radiation (λ = 1486.6 eV). The Brunauer–Emmett–Teller (BET) specific surface area was examined by N₂ adsorption-desorption measurements in a Micromeritics ASAP 2420 surface area analyzer. The samples were evacuated at 150 °C before the N₂ adsorption test. The BET surface area was estimated by the multipoint BET method based on the adsorption data in the P/P₀ range of 0.0–1.0, where P and P₀ correspond to the equilibrium and saturation pressures of the adsorbates at the temperature of adsorption, respectively.