Quanta 3d feg

The X-ray diffraction (XRD) pattern was measured using a D2 Phaser X-ray diffractometer, and the Raman spectroscopy was measured with an excitation wavelength of 532 nm using a Raman microscope (Renishaw InVia, Wotton-under-Edge, UK); these measurements were used to confirm the crystal structure of CVT-grown WS₂ crystals. The height profiles were carried out to find the thickness of nanoflakes using atomic force microscopy (AFM, Bruker-ICON2-SYS, Billerica, MA, USA). Scanning electron microscopy (SEM, Hitachi S3000H, Tokyo, Japan) was used to capture the image of the nanoflake device to obtain the dimensions of the conduction channel. Focused ion beam (FIB, FEI Quanta 3D FEG) was utilized for the deposition of Pt contacts. The dark current-voltage (i_d-V) curves and photoconductive measurements of the photodetector were carried out in a four-point probe electrical measurement system using Keithly 4200-SCS. A 532 nm laser source was used for illumination and the incident laser power was measured using a calibrated power meter (Ophir Nova II) with a silicon photodiode head (Ohir PD300-UV). A holographic diffuser was utilized to minimize the error in the power density calculation by broadening the laser beam size (~20 mm²).

Transmission electron microscopy (TEM) analysis was performed by means of a high-resolution transmission electron microscope Tecnai G2 T20 X-TWIN (FEI) equipped with an energy dispersive X-ray spectrometer (EDS). The samples were prepared for analysis by scratching the film from the surface of the electrode and placing it on a TEM copper grid. Moreover, microscopic images of the pSPCE/PbNPs surface were attained with a high-resolution scanning electron microscope Quanta 3D FEG (FEI, USA) (acceleration voltage of 5.0 kV, working distance of 9.3 mm, magnification of 25,000×).
All voltammetric studies were made using a µAutolab electrochemical analyzer (Eco Chemie, Utrecht, The Netherlands) controlled by GPES 4.9 software. The standard quartz electrochemical cell with a volume of 10 mL composed of a commercially available screen-printed carbon sensor (SPCE, DropSens, Spain, Ref. C150) was applied for experiments. The SPCE sensor consisted of a screen-printed carbon working electrode, a platinum screen-printed auxiliary electrode, and a silver screen-printed pseudo-reference electrode. The µAutolab analyzer controlled by FRA 4.9 software was used for electrochemical impedance spectroscopy (EIS) measurements.
HPLC analyses were performed on a VWR Hitachi Elite LaChrom HPLC with a PDA detector using an Ascentis Express C18 column (15 cm × 2.1 mm i.d., 2.7 μm).

The lamellar specimens for HRTEM observation were prepared by a dual-beam scanning electron microscopy (SEM)/focused ion beam (FIB) system (FEI Quanta 3D FEG and FEI Helios) based on site-specific in situ lift-out technique. Before the ion thinning, a metallic protective layer of Cr with a thickness between 30 and 40 nm was first deposited on the sample surface. Then, a platinum supporting layer with a thickness between 1 and 1.5 μm was further deposited on the targeted area using the ion beam deposition inside the chamber. This dual-beam system is capable of fast milling at a high voltage of 30 kV and subtle thinning at the final stage using a few kV (2–5 kV) Ga⁺ ion milling. During ion thinning, the sample was tilted between 1 and 2° towards the ion beam in order to avoid significant damage to the sample structure. The ion beam current was between 10 and 15 pA.

Cryo-FIB milling (Rigort et al., 2012b (link)) was performed as described in detail at Bio-protocol (Schaffer et al., 2015 (link)). Plunge-frozen grids were mounted into autogrids that were modified for FIB milling (Autogrid sample holder, FEI), providing stability to the EM grids during sample preparation and transfers. These autogrids were mounted into a dual-beam (FIB/SEM) microscope (Quanta 3D FEG, FEI) using a cryo-transfer system (PP3000T, Quorum) with a custom-built transfer shuttle. During FIB operation, samples were kept at a constant temperature of −180°C using a homemade 360° rotatable cryo-stage (Rigort et al., 2010 (link), 2012a (link)). To improve sample conductivity and reduce curtaining artifacts during FIB milling, the whole Autogrid was coated by organometallic platinum (protocol adapted from Hayles et al., 2007 (link)) using the in situ gas injection system (GIS, FEI) and the following parameters: 13.5 mm stage working distance, 26°C GIS pre-heating temperature, and 4 s gas injection time. Thin lamellas were prepared using the Ga⁺ ion beam at 30 kV under a shallow 8°–12° angle. Rough milling was performed with a rectangular pattern and 0.3 nA beam current, followed by sequentially lowered beam currents of 0.1 nA, 50 pA and 30 pA during the thinning and cleaning steps. During the milling, the specimen was also imaged using the SEM at 3–5 kV and 5–30 pA.

The embedded slices were placed on a metal stub and further trimmed with glass and diamond knives in an ultramicrotome (Ultracut E microtome, Leica, Wetzlar, Germany). The slices were coated with a protective layer of carbon, which prevented any charge. The metal stub with the slices was set on the stage of FIB/SEM. The serial section images in the middle molecular layer of the dorsal DG were automatically obtained by FIB/SEM (Quanta 3D FEG, FEI, Hillsboro, OR, USA). Serial images of the block face were acquired by repeated cycles of sample surface milling and imaging using the Slice & View G2 operating software (FEI). The milling was performed with a gallium ion beam at 30 kV with a current of 1.0 nA or 3.0 nA (Golgi stain). The milling pitch was set to 15 or 30 (Golgi stain) nm/step. The images were acquired at an accelerating voltage of 2.5 kV. The other acquisition parameters were as follows: dwell time = 6 s/pixel, pixel size = 4.9 and 14.6 (Golgi stain) nm/pixel.