Fe sem

Microstructures of the bionic lotus polymer coating surfaces were observed by a scanning electron microscopy (JSM-5600LV and field emission scanning electron microscopy (FE-SEM), JEOL, Akishima, Japan). Compositions of the surface of pure PTFE and PTFE/PPS coatings were analyzed by an X-ray photoelectron spectroscopy (XPS) on a VG Escalab 210 (VG Scientific, East Grinstead, UK) spectrometer with a Mg Ka X-ray source (1253.6 eV). The water static contact angle (WCA) and water sliding angle (WSA) of distilled water droplets of 5 μL on the superhydrophobic coating samples were tested by a contact angle apparatus (DSA-100, KRÜSS GmbH, Hamburg, Germany). Morphologies of the water droplets of 5 μL on the coatings were recorded with a digital camera.

The morphological characteristics of the fibers fabricated were determined using field emission scanning electron microscopy (FESEM) (JEOL, Tokyo, Japan). Samples were stuck on metal stubs and then coated with gold palladium (10 nm). About 50 fibers from each sample were randomly selected from SEM images and their diameters were measured by using ImageJ software V 1.8.0 (NIH, Bethesda, MD, USA).

A single colony of L. fermentum SMFM2017-NK2 was inoculated into MRS broth and incubated anaerobically at 37 °C for 24 h. The culture (100 μL) was inoculated into 10 mL fresh MRS broth containing sterile glass (0.5 × 0.5 cm) and incubated anaerobically at 37 °C for 24 h to allow bacteria to attach to the glass. The glass was then transferred to a 24-well plate and 50 μL of 1.8% glutaraldehyde solution (Sigma, St. Louis, MO, USA) was added. The glass was washed with 1 mL sterile distilled water three times for 5 min. After washing, the moisture from the glass was removed with sterile gauze, and 40 μL of 2% osmium tetroxide solution (Sigma) was dropped onto the glass for secondary fixation at room temperature in a dark condition for 20 min. The glass was then washed with 1 mL sterile distilled water three times for 5 min and soaked with 25, 50, 75, 90, and 100% ethanol for 5 min each. The glass was dried at room temperature for 1 h. Then, 40 μL of hexamethyldisilazane (HMDS; Sigma) was added to dry it completely. The surface of the glass was coated with platinum using a Sputter Coater (Cressington Ltd., Oxhey, Watford, UK) to give conductivity. It was fixed to the mount, and the morphology of the bacteria was observed with a field emission scanning electron microscope (FE-SEM; JEOL USA Inc., Peabody, MA, USA).

The crystallinity of the prepared AgNPs was determined using powder X-ray diffraction by a Bruker diffractometer, model D8 Advance. The crystallite size of the prepared AgNPs was determined using Debye–Scherrer’s formula: $$D=\frac{\mathrm{K}\mathsf{\lambda }}{ \beta \cos \theta }$$
where D is the crystallite size, β is the full width at half maximum (FWHM), λ is the X-ray wavelength (0.154 nm), θ is the diffraction angle, K is a constant related to the crystallite shape and is approximately 0.94. The functional groups in the produced samples and extracts were identified using Fourier transform infrared spectroscopy (FTIR, Perkin Elmer spectrometer, model Spectrum One). The samples were scanned over a range of 4000 to 500 cm⁻¹. The shapes and sizes of the synthesized nanoparticles were examined using a field-emission scanning electron microscope (FESEM, JEOL Japan).

The surface morphologies of the iron-loaded activated carbon composites (NZVI/GAC) prepared in this study were examined by SEM (FESEM, JEOL Ltd., Japan), and the sizes of the NZVI, GAC and NZVI/GAC were obtained by TEM (TEM, JEOL Ltd., Japan). XRD patterns were collected with an Ultima IV instrument at a scan rate of 2 degrees per minute with a 2-h range of 10–90 degrees with Cu K-beta radiation operating at an accelerating voltage of 40 kV to determine the crystal structures and chemical compositions of these particles (1: GAC-BCS5 stored for one year; 2: NZVI stored for two months; 3: NZVI stored for one year; 4: NZVI stored for 19 months and 5: NZVI/GAC stored for two months). FTIR spectra (Perkin-Elmer Instrument Co. Ltd., USA) were collected to analyse the surface chemical structures and compositions of the NZVI, GAC-BCS5 and NZVI/GAC particles. BET surface areas were measured using a surface area analyser (BELSORP-max, MDTC-EQ-M0302) according to GB/T 19587–2004. In addition, the zeta potentials of the powders were measured using a Zetasizer (NaNoZS) according to GB/T 32668-2016, and the total Fe contents of the samples were measured via ICP-MS (Spectro Arcos II, model: MDTC-EQ-M21-01) according to JY/T 015-1996.

All absorbance measurements were performed spectrophotometrically using a 6705 UV/Vis spectrophotometer (Jenway Scientific, Staffordshire, UK) [22 (link)]. The methanol concentration was assessed using an Agilent 7890A chromatography system equipped with a flame ionization detector and an Agilent 19091 J-413 (HP-5) column (Santa Clara, CA, USA) [19 (link)]. Validation of whole-cell encapsulation within CuFe₂O₄-containing polymeric matrix was performed via field-emission scanning electron microscopy (FE-SEM, JEOL, Tokyo, Japan) [21 (link)]. X-ray diffraction (XRD) analysis was performed using an X’pert PRO MPD, Malvern PANalytical, Malvern, UK). All presented values are based on three experimental replicates.