*2.3. Characterization*

#### 2.3.1. Fourier Transform Infrared (FT-IR)

FT-IR study was conducted to determine the functional groups present in the cellulose. The measurements were performed using a Nicolet iS5 spectrometer (Thermo Scientific, Whatman, MA, USA). Spectra were obtained between 4000 and 400 cm<sup>−</sup><sup>1</sup> at a resolution of 4 cm<sup>−</sup><sup>1</sup> and scanning speed of 20 mm/sat.

#### 2.3.2. X-Ray Diffraction (XRD)

XRD patterns of the cellulose were performed in a D8 Advance (Bruker, Bremen, Germany). Samples were examined with a scanning angle of 2θ from 10◦ to 40◦ at a rate of 1◦/min with the CuKα filtered radiation. The crystallinity index, CrI was calculated from the diffraction intensity data using deconvolution method [45]. In which the diffraction profile was fitted by Gaussian function to find the contribution of each individual peak relative to the crystallographic planes and the amorphous background. The CrI was calculated Hermans equation as follows:

$$\text{CrI} = \left(\frac{\text{A}\_{\text{cr}}}{\text{A}\_{\text{cr}} + \text{A}\_{\text{am}}}\right) \times 100\% \tag{1}$$

where Aam is the amorphous area, and Acr is the sum of the area of the 101, 10¯ı, 002, 040 peaks.

#### 2.3.3. Differential Scanning Calorimetry (DSC)

DSC was carried out to analyze the thermal behavior of the cellulose. The samples were characterized on a DSC Q100 (TA Instruments, DE, USA) under constant nitrogen flow (50 mL/min), from 25 to 400 ◦C, at a heating rate of 10 ◦C/min.

#### 2.3.4. Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy STEM)

The morphology of BC-NC suspension was measured by using the high-resolution JEOL-2100F TEM (Jeol, Akishima, Tokyo, Japan) in TEM and STEM mode. Samples were conventionally deposited on carbon coated copper grids and a negative staining was achieved using uranyLess solution (Delta Microscopies, Toulouse, France). The size and diameter distribution particle were measured by ImageJ (version 1.41 h) and origin pro-8 software.
