Omega energy filter

The morphological characteristics of the CNCs were evaluated via transmission electron microscopy (TEM), using a LEO 912AB TEM with an Omega energy filter (Zeiss, Oberkochen, Germany) at an accelerating voltage of 120 kV. For the microscopic observations, drops of dilute aqueous suspension of CNCs (≈4 wt %), previously sonicated for 1 min, were deposited on carbon-coated electron microscope grids, negatively stained with 2% uranyl acetate, and allowed to dry. Representative micrographs were selected for measuring the diameter (D), length (L), and aspect ratio (L/D) of the nanocrystals by digital image analysis (iTEM, software, Olympus Soft Imaging Solutions GmbH, Münster, Germany). In addition, the dimensions of CNCs from all heating programs, in dilute suspensions (at pH 8), were also investigated by dynamic light scattering (DLS) measurements (mod. Litesizer500, Anton Paar, Graz, Austria), performed at 25.0 ± 0.1 °C with a 35 mW laser diode light (λ = 658 nm), and collecting the scattered light at 15° and 90°. By applying correlation analysis and the Stokes–Einstein relation, the equivalent hydrodynamic diameters (D_Hy), the polydispersity index (PDI), and size distributions of the scatters were calculated. Four runs were performed, withdrawing three different aliquots for each set of experimental conditions.

The TEM grid specimens were imaged and analyzed in a Hitachi SU6600 field emission scanning electron microscope (Hitachi, Tokyo, Japan) equipped with a Bruker energy-dispersive X-ray detector (Bruker Nano GmbH, Berlin, Germany) and a NORDIF electron backscatter (EBSD) detector (NORDIF, Trondheim, Norway). For elemental analysis of particles, an acceleration voltage of 15 keV, analytical working distance of 10 mm and electron probe current 7–8 nA were used. For aggregates/agglomerates with primary particle sizes less than 20 nm, an area of approximately 100 × 100 nm was scanned for X-ray acquisition in a particle–dense area to obtain elemental spectra. For larger particles (> 30 nm) X-ray spectrums from single particles were obtained. In addition, an Auriga Crossbeam Workstation (Carl Zeiss AG, Oberkochen, Germany), equipped with INCA X-Max silicon drift detector (Oxford Instruments, Abingdon, UK) for energy dispersive X-ray microanalysis was used.
The phase and elemental composition of the particles were studied by a Zeiss Libra 120 transmission electron microscope equipped with an OMEGA energy filter (Carl Zeiss AG, Oberkochen, Germany). Particle diameter measurements were conducted by statistical analysis of TEM images using the Minitab version 16 software (Minitab Statistical Software, Minitab 16; https://www.minitab.com).

TEM imaging of DCs was carried out by using a LEO 912 AB TEM with an in-column Omega energy filter (Zeiss) at 80 kV accelerating voltage. TEM images were recorded with a Tröndle TRS Sharp Eye bottom-mounted 2 K CCD camera (Tröndle), filtered at zero energy loss. The TEM implementation and recording process were controlled by iTEM 5.0 software (Olympus).