Em ace200 sputter coater

The surface and internal morphology of CS/PVA hydrogels were investigated using a Quanta 200 Scanning Electron Microscope (FEI Company, Bruno, Czech Republic) and a Verios G4 UC Scanning Electron Microscope (Thermo Scientific, Bruno, Czech Republic) equipped with an energy dispersive X-ray spectrometer (EDS, EDAX Octane Elect Super SDD detector, Ametek, Mahwah, NJ, USA) with a better magnification that allowed the visualization of AgNPs. The samples were coated with 10 nm platinum using a Leica EM ACE200 Sputter coater to provide electrical conductivity and to prevent charge buildup during exposure to the electron beam.

Self-wicking grids were prepared as described previously by incubating 400 mesh copper–rhodium grids (Maxtaform, Electron Microscopy Sciences) in nanowire growth solution consisting of 750 mM sodium hydroxide and 65 mM ammonium persulfate for 5 min followed by washing with water (Razinkov et al., 2016 ▸ ; Wei et al., 2018 ▸ ). A continuous formvar film with ∼2 µm holes spaced 4 µm centre to centre was prepared and overlaid on the self-wicking grids as described previously (Marr et al., 2014 ▸ ) and coated with ∼35 nm of gold using a Leica EM ACE200 sputter coater before dissolving the plastic film with chloroform. It may be that during spraying of the grid droplets smaller than the hole size in the gold film pass through the holes, while the larger droplets cover the holes. However, the high density of smaller droplets may also contribute to the formation of a suitable film for cryo-EM once the holes have been blocked by larger droplets.

The morphology of CS-AgNps was analyzed by transmission electron microscopy (TEM) using a Hitachi High-Tech HT7700 microscope (Japan) operated in “high contrast” mode and at a 100 kV acceleration potential. Samples were applied from aqueous suspension (1 mg/mL) to 300 mesh copper grids, coated with carbon and dried under vacuum.
The morphology of films (surface and cross-sections) was observed by SEM through a Verios G4 UC Scanning Electron Microscope (Thermo Scientific, Bruno, Czech Republic) equipped with an energy dispersive X-ray spectrometer (EDS, EDAX Octane Elect Super SDD detector, Ametek, Mahwah, NJ, USA). The samples were coated with 10 nm platinum using a Leica EM ACE200 Sputter coater to provide electrical conductivity and to prevent charge buildup during exposure to the electron beam.
The visualization of the surface films (unloaded and IBF-loaded F #3 sample) was carried out by atomic force microscopy (AFM) using Nanoscope IIIa-type Multimode (Digital Instruments, Tonawanda, NY, USA) equipped with an “E”-type scanner. Amplitude- and height-mode images were captured at room temperature in the air using the tapping mode with a silicon tip cantilever (Bruker Corporation, Billerica, MA, USA) operated at a resonance frequency of 275–300 kHz and at a scan rate of 1.2 Hz. The images were evaluated with the Nanoscope V614r1 software (Digital Instruments, Buffalo, NY, USA).