Feg sem

Micro-texture of the extruded rods was obtained using the electron back-scatter diffraction (EBSD) technique in a Field Emission Gun Scanning Electron Microscope (FEG-SEM) by FEI Company. The samples were cloth polished with diamond paste (0.05 microns) to obtain a mirror finish, with kerosene acting as a lubricant. Further, mechanical electro-polishing was carried out (using an electrolyte containing 3:5 solution of H₃PO₄ in ethanol and pure aluminum cathode at 3 V for 30 s and 1.5 V for 3 min at ~0 °C) in the final polishing step. The EBSD scans were recorded on the radial plane of the samples parallel to the extrusion direction (ED). Kernel average misorientation (KAM) of each EBSD spot with all of its neighbouring spots was calculated with the provision that misorientations exceeding 5° were excluded from the average calculation. The misorientation between a grain at the centre of the kernel and all points at the perimeter of the kernel were measured. The local misorientation value assigned to the centre point was the average of these misorientations, which could be obtained from the EBSD scans. Maps, constructed using this method, are helpful in visualizing the distribution of local misorientation within a grain.

Samples for scanning electron microscopy were prepared as follows: 24-well plates containing glass slides were inoculated with both Listeria strains in TSB-YE medium containing or not containing TiO₂ nanoparticles at different concentrations. After 48 hrs incubation, samples were washed three times with phosphate buffered saline (PBS), fixed with glutaraldehyde 2.5% in 0.1 M cacodilate buffer (pH 7.4), and post-fixed in 1% OsO₄ solution. After dehydratation in ethanol–water misture with increasing ethanol concentrations (65%, 75%, 85%, 95%, and 100%), biofilms were treated with hexamethyldisilazane (Sigma–Aldrich, St Louis, MO), and overnight air-dried. Dehydrated specimens were coated with a thin film of Au in a sputter coater. Morphological analysis was performed in an Ultra-high resolution Field Emission Gun Scanning Electron Microscopy (FEG-SEM, FEI Company). Secondary electron images were performed with an acceleration voltage of 10 KV. The images were processed for display using photoshop (Adobe Systems Inc., San Jose, CA, USA) software.

Scanning electron microscopy (SEM) was used to assess the morphological effects of peptides on the E. coli and S. aureus strains. Both untreated and treated bacteria were fixed overnight at 4 °C with 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH of 7.4) and post-fixed with 1% osmium tetroxide. After washing with cacodylate buffer, the samples were seeded onto glass slides coated with ε-poly-L-lysine (Sigma-Aldrich, Saint Louis, MO, USA). Adsorbed bacteria were dehydrated using an alcohol gradient (35 to 100%) followed by treatment with hexamethyldisilazane (Sigma–Aldrich, MO, USA) and air drying. The dried specimens were mounted on stubs containing adhesives and sputter-coated with gold. Morphological analysis was performed using an ultra-high-resolution Field Emission Gun Scanning Electron Microscope (FEG-SEM, FEI, Hillsboro, OR, USA). Secondary electron images were taken with an acceleration voltage of 20 kV. The images were processed for display using Photoshop CS4 (version 11.0) software (Adobe Systems Inc., San Jose, CA, USA).