Su8020

After cucumber fruit skin was air-dried, the epidermis cells were visualized under a HITACHI SU8020 variable pressure SEM (Hitachi, Japan). For TEM assay, fruit skin were cut into small pieces, and were collected for fixation, and the process was performed as according to Wang et al. (2019) [54 ].

Porous structures of the materials under investigation were characterized by using nitrogen (N₂) adsorption/desorption analysis at −196 °C on Micromeritics Tristar II 3020, and the specific surface area (S_BET) was calculated using the Brunauer–Emmett–Teller (BET) method. Prior N₂ sorption analysis, the sample was degassed at 100 °C under vacuum for at least 24 h. The total pore volume (V_total) was measured from the adsorption amounts of N₂ gas at p/p₀ = 0.99 and the micropore volume (V_micro) was determined by density functional theory (DFT). The mesopore volumes (V_meso) were calculated by subtracting the V_micro from V_total. The structural transformation and degree of graphitization of the materials were analyzed using Raman spectroscopy (on Raman Xplora Plus spectrometer). To study the phase structure and crystallinity of the materials, an X-ray diffractometer (XRD, Rigaku SmartLab; Rigaku Corporation, The Woodlands, TX, United States) was used. Surface morphology and diameter, as well as the elemental composition of the materials, were analyzed using field electron scanning emission microscope coupled with elemental dispersive X-ray spectroscopy (FE-SEM-EDX, Hitachi SU8020; Hitachi High-Technologies Corporaation, Tokyo, Japan). Prior to FE-SEM analysis, all samples were dried at 100 °C and stored in a desiccator overnight.

Morphologic changes of bacterial cell surfaces after D-AP19 treatment were investigated by scanning electron microscopy (SEM) as previously described^{26 ,27} . Bacterial cells in mid-log phase were diluted with PBS to obtain an OD₆₂₀ of 0.05 and incubated at 37 °C for 0.25 h with peptide at a concentration of 0.5 × MIC. After incubation, the treated bacterial cells were centrifuged at 10,000 g for 10 min and washed 3 times with PBS, pH 7.2. Then, they were filtered through 0.22 µM mixed cellulose ester (MCE) membrane filters to retain the treated bacterial cells. Samples were pre-fixed by immersion into 2.5% (vol/vol) glutaraldehyde–PBS, then post-fixed with 1% OsO₄ in DW. After washing 3 times, they were dehydrated using a graded ethanol series of 20%, 40%, 60%, 80% and 100%, 15 min in each dilution. After that, the samples were transferred into absolute ethanol 2 times, 15 min each time. Specimens were then dried and coated by platinum particle using Sputter Coater (Quorum Q150R ES; Quorum). Processed bacterial cells were observed using a scanning electron microscope (Hitachi SU8020; Hitachi, Japan).

Surface roughness has been measured with an optic 3D measuring instrument InfiniteFocusSL Alicona. Microhardness measurements were performed on a Vickers tester UHL VMHT AUTO using a load of different values within the compound zone and diffusion layer. Chemical composition was examined with the microanalysis X-ray method on an EDS detector (EDS NSS 312, ThermoScientific, Waltham, MA, USA), which was connected to a scanning electron microscope HitachiSu8020. Microstructure analyses were conducted on scanning electron microscopes—JEOL-6400 (JEOL, Tokyo, Japan) and HitachiSu8020 (Hitachi, Tokyo, Japan). X-ray diffraction (XRD) was conducted using an Empyrean (PANalytical, Malvern, UK) diffractometer with a monochromator and PIXcel3D detector. A Cu anode was used to obtain Cu K_α (K_α1 = 0.154056 nm). The measurements were conducted in 2θ ranges of 20–80°. The PDF-4+ 2020 International Centre for Diffraction Data database and High Score Plus software were used for phase analysis.
Chemical composition was determined with X-ray photoelectron spectroscopy in a commercial UHV surface analysis system (PREVAC, Rogow, Poland). The analysis chamber was equipped with nonmonochromatic X-ray photoelectron spectroscope and a kinetic electron energy analyzer (SES 2002; Scienta, Uppsala, Sweden). The XPS analysis was performed using Al K_α (h = 1489.6 eV) radiation.

The conventional three-electrode system was used for the electrochemical experiments. The modified glass carbon electrode (3 mm) was used as a working electrode, a saturated Ag/AgCl was used as a reference electrode, and a platinum wire (1 mm) was used as the auxiliary electrode. All electrodes were obtained from Aida Heng-sheng Technology Development Co., Ltd. (Aida, Tianjin, China). Cyclic voltammograms (CVs) (Gamry 600+, Warminster, PA, USA) and amperometric (i-t) (Gamry 600+, Warminster, PA, USA) measurements were performed by the Gamry 600+ (Warminster, PA, USA) electrochemical workstation.
For AuNPs/CS/MXene characterization, scanning electron microscopy (SEM) and X-ray energy-dispersive spectrometry (EDS) were recorded by Hitachi SU8020 (Hitachi, Tokyo, Japan). The transmission electron microscopy (TEM) images and X-ray diffraction (XRD) data were obtained by Tecnai G2 F30 (FEI, Hillsboro, OR, USA) and Bruker D8-Advance X-ray diffractometer (Bruker, Karlsruhe, Germany).

The morphology of CuNW transparent electrode was characterized by field emission scanning electron microscopy (SEM, Hitachi SU8020, Hitachi High Technologies America, Inc.). The composition of the surface coatings was also investigated by X-ray diffractometry (XRD, Rigaku Smart Lab, Rigaku Americas Holding Company Inc.). The transmittance of CuNW transparent electrodes was measured using a UV-visible-near infrared spectrophotometer (V670, JASCO Corp.) at 550 nm. The sheet resistance was examined by the four-probe method with a surface resistivity meter (LorestaGPT610, Mitsubishi Chemical Analytech Co. Ltd). The bending test was examined using a machine which could bend the sample from 0° to 180° on rods with various diameters. The resistance was recorded in time using a resistance meter (RM 3544-01, Hioki E.E. Corporation). The thermal property of the PET films was tested by simultaneous thermogravimetry-differential scanning calorimetry, (STA/TG-DSC, STA449 F3, NETZCH) with a heating rate of 10 °C min⁻¹ in nitrogen atmosphere.