Gemini sem 500 system

Scanning Electron Microscopy (SEM) was carried out on a Zeiss Gemini SEM 500 system at 10 kV using a working distance (WD) of 13.3 mm and an aperture (AP) of 30 μm, unless otherwise mentioned. Two detectors were used alternatively: an in lense secondary electron detector (In Lens) for best imaging resolution and a Everhart-Thornley detector (SE) for the detection of secondary electrons providing both topography and chemical contrast, with the lightest elements (C) appearing darker than the heaviest elements (Cu). An EDXS SDD probe (30 nm²) confirmed that C, Cu, and O were the only elements present in the composites and that the white spots were indeed copper oxides. The powder samples were pressed on a sample holder decorated with carbon tape before analysis.

The morphological characterization of (AM/PA) hydrogel layers was performed using scanning electron microscopy (SEM, Gemini SEM 500 system, Zeiss, Oxford Instruments, Oxford, UK). First, hydrogels layers were immersed in distilled water to completely swell. Then, they were frozen at −20 °C prior to lyophilization overnight (Telstar Lyoquest freeze-drier, Azbil Telstar Technologies, S. L. U., Terrasa, Spain). The resultant dry aerogel samples were finally covered with a Au layer of about 15 nm using sputter-coating (BAL-TEC SCD 005 sputter coater, Leica microsystems, Wetzlar, Germany).

Nanopipettes were fabricated from quartz capillary
tubes (QTF100-50-10, Sutter Instrument) with dimensions: 1.0 OD ×
0.5 ID × 100 L mm. They were pulled to a fine aperture with a
CO₂-laser puller (Sutter Instrument P-2000; pulling parameters:
line 1 with HEAT 750, FIL 4, VEL 30, DEL 150, and PUL 80; line 2 with
HEAT 650, FIL 3, VEL 40, DEL 135, and PUL 150). The nanopipettes possessed
an opening diameter of ∼50 nm, characterized with field emission
scanning electron microscopy (FE-SEM) (GeminiSEM 500 system, Zeiss,
Germany); representative SEM images can be found in Figure S1. Each nanopipette was filled with 3 mM FcDM in 50
mM KCl, with a QRCE (AgCl-coated Ag wire) inserted from the back.
A small droplet of silicone oil (DC 200, Fluka) was added atop the
solution in the nanopipette to minimize electrolyte evaporation from
the back opening.^{43 (link)} The QRCE potential
was stable^{44 (link)} and calibrated routinely before
and after the SECCM measurements against a commercial leakless Ag/AgCl
electrode (3.4 M KCl, ET072, eDAQ, Australia), giving a potential
of +75 ± 2 mV. All electrochemical results hereafter are presented
versus Ag/AgCl (3.4 M KCl), referred to as Ag/AgCl.