Nicolet 8700 ftir

Graphene powder (GPs, purity higher than 99.5%) was purchased from SkySpring Nanomaterials (Houston, TX, USA). The size and shape of the graphene platelets were inspected using a JEM-1220 (JEOL, Tokyo, Japan) TEM at 80 KeV, with a Morada 11 megapixels camera (Olympus Soft Imaging Solutions, Münster, Germany) and FEI QUANTA 200 SEM. The average size of agglomerates and zeta potential measurements were carried out using Zetasizer Nano S90 (Malvern Instruments Ltd., Malvern, UK). using DLS at room temperature (25 °C). Infrared spectra were collected in a Fourier transform infrared spectrophotometer (Nicolet 8700 FTIR, Thermo Scientific, Waltham, MA, USA). Measurements were performed using the FT-IR ATR (attenuated total reflectance) technique over a range of 4000–400 cm^-1.

For Fourier-transform infrared spectroscopy (FT-IR) analysis, a Nicolet 8700 FT-IR (Thermo Scientific, Waltham, MA, USA) equipment was used in a range of 4000–650 cm⁻¹ wavelength, with 100 scans and a resolution of 4 cm⁻¹. For analysis, 10 mg of sample were placed in a ZnSe crystal, and an absorbance mode with attenuated total reflection (ATR) and an optical speed of 0.4747 was used [38 (link)].
The esterification degree (%DE) of the pectin was also calculated using the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) methodology to corroborate the results obtained by the titration method [39 (link),40 (link)]. According to DRIFTS, the peak area values of free carboxyl groups (1630 cm⁻¹) and the esterified groups (1745 cm⁻¹) are related to the esterification degree by Equations (21) and (22): R=A1745/(A1745+A1630)×100
%DE=124.7×R+2.2013

ATR-IR of the components used to fabricate the ESS-CA matrices was performed using a Nicolet 8700 FT-IR with a Smart iTR diamond tip accessory (Thermo Scientific, Grand Island, NY, USA). Spectra representative of the top, bottom, and internal surface of the matrices were collected. To analyze the internal surface, the matrices were sectioned along the transverse plane.

Attenuated total reflectance Fourier transform spectroscopy analysis (ATR FTIR) on graphene oxide flakes was made using Nicolet 8700 FTIR (Thermo Scientific, Waltham, MA, USA) over a range of 4000–400 cm⁻¹ at a resolution of 4 cm⁻¹. To prepare the samples in the form of thin films for analysis, the water suspension of the flakes in the concentration of 0.4 mg/mL was poured into a Teflon mold of 50 mm diameter and left under a fume hood for 72 h. The air-dried samples were thereafter freeze-dried at −20 °C for up to 72 h using an Alpha 1–2 lyophilizator.

SEM analysis was conducted using a Carl Zeiss Supra 40 field emission scanning electron microscope (2–5 kV, depending on the sample state). The SEM samples were coated with Au film for 30 s at a constant current of 30 mA before observation.
EDS data were acquired by EDS (Hitachi S4800, Hitachi Ltd., Tokyo, Japan; FEI, Sirion 200, Philips, Hillsboro, OR, USA).
Infrared spectra of the samples were acquired by a Thermo Scientific Nicolet 8700 FT-IR (Thermo Fisher Scientific, Madison, WI, USA) spectrometer in the attenuated total reflectance (ATR) mode.
XRD data were measured by a PANalytical X’pert PRO MRD X-ray diffractometer equipped with Cu Kα radiation (λ = 1.54056 Å).
Samples were characterized using a UV−Vis−NIR spectrophotometer (Lambda 750, PerKinElmer Inc., Waltham, MA, USA).