Axis ultra photoelectron spectrometer

The analyses of the surface composition of membranes were carried out with the use of the AXIS Ultra photoelectron spectrometer by Kratos Analytical Ltd. The source of photoelectron emission from the sample surface (down to approx. 5 nm deep) was X radiation generated by the Al anode with monochromator (Kα line with an energy of 1486.6 eV). All XPS spectra were made using a charge neutralizer due to the insulating nature of the sample material. The analysis was performed on 3 to 6 fields with an area of 700 × 300 μm each, on the surface of each sample. The parameters of the XPS analysis are presented in Table 4.

X-ray photoelectron spectroscopy (XPS) studies were carried out by an AXIS ULTRA photoelectron spectrometer (Kratos Analytical Ltd., Manchester, UK) on the surface of the neat PEEK, plasma-treated PEEK, PDA-coated PEEK (24 h), plasma-pretreated PEEK, and PDA-coated PEEK (24 h). The X-ray source of monochromatized Al Kα (hν = 1,486.7 eV) was operated at 50 W and 15 kV. Elemental compositions (C, O, and N) were determined on the PEEK surfaces. The component peak in the C 1 s spectrum was used as a reference with a binding energy of 284.8 eV. Data analysis was performed using the Kratos spectra deconvolution software (version 2.2.9; Kratos Analytical Ltd., Manchester, UK).

XRD characterization of the samples was carried out on a German Bruker D8 Advance X-ray diffractometer using the Ni-filtered Cu Kα radiation at 40 kV and 40 mA. XPS data were recorded with the Axis Ultra Photoelectron Spectrometer (Kratos Analytical Ltd.) by means of a monochromatized Al Kα anode (225 W, 15 mA, 15 kV). The C 1s peak at 284.8 eV was used as the reference to calibrate the binding energies (BE). A Tecnai F20 electron microscope operating at 200 kV equipped with an EDS unit (Si(Li) detector) was used for the TEM investigations. The samples for electron microscopy were prepared by grinding and subsequent dispersing the powder in ethanol and applying a drop of very dilute suspension on carbon-coated grids. High resolution TEM, EDS mapping, and HADDF-STEM were performed on an FEI Titan G2 (60-300) probe-corrected TEM system with a field emission gun operated at 300 kV.