# Spanish Poplar Biomass as a Precursor for Nanocellulose Extraction
## 3 Results and Discussions  
In Figure 1, the TEM morphological depiction of poplar sourced nanocellulose is show-cased. As explained in the caption, three types of nanocellulose are depicted. Figure 1B,D,F are zoomed spots of Figure 1A,C,E; hydrolyzed for 5, 10, and 15 min, respectively. Acidic hydrolysis for 5 min yielded splitch-like structure morphology, of minimal portion of whisker shaped parts. Hydrolysis for 10 min yielded more fibril-like shape; a higher aspect ratio is quite clearer in Figure 1B than Figure 1A. Hydrolysis for 15 min yielded a mesh-like structure, more likely to appear like whiskers between nodes. It is obvious that for the three hydrolysis durations (5, 10, and 15 min), as the hydrolysis duration increases, the morphology transforms from splotch to meshed-like whiskers. This observation is valid for figures which are zoomed out (Figure 1A,C,E) and those zoomed in (Figure 1B,D,F). Finer morphology with longer duration can be elucidated by increasing the likelihood of each region to be hydrolyzed, yielding whisker-shaped CNC. Figure 1: TEM investigation of poplar sourced cellulose nanocrystals (CNC). (**A,B**) depict CNC after 5 min of hydrolysis; (**C,D**) depict CNC after 10 min of hydrolysis, and (**E,F**) depict CNC after 15 min of hydrolysis. The morphology of MCC sourced nanocellulose is exhibited in Figure 2. Results of two hydrolysis durations (5 and 10 min) are showcased in Figure 2A,B, and Figure 2C,D, respectively. Hydrolysis for 5 min resulted in distanced (or dispersed) groups of attached whiskers; the magnified rightwards figure shows nodal connection, and longitudinal attachment between whiskers. The 10-min hydrolysis yielded a uniformly distributed meshed structure of almost uniform whisker diameter in the magnified figure. To quantitatively compare between poplar and MCC, ImageJ tool was employed to measure the lengths and widths of whiskers (or other particles) from the two sources, which were subjected to different hydrolysis durations (processing time). The values in Table 1 were based on Figure 1A,C,E and Figure 2A,C. The table shows that whiskers originated from MCC are smaller than those from poplar by about 50% (length), and by 70% (width). Generally, as the processing time increased, both length and width decreased; however, width was more affected by time than length. Maximum processing time for poplar yielded 68.8-nm width whiskers, with aspect ratio 3.2. MCC yielded 19.9-nm width whiskers, with aspect ratio 10.1. Zoomed depictions (Figure 1B,D,F and Figure 2B,D) after size measurement by ImageJ showed s smaller size than other figures; poplar sourced nanocellulose was of 23-nm width with aspect ratio 5.5 after 15 min, and MCC sourced nanocellulose yielded 10.9 nm with aspect 7. Fourier Transform Infrared (IR) was conducted on all samples (Figure 3). Analysis encompassed untreated poplar fibers, treated fibers, poplar sourced nanocellulose, MCC, and MCC sourced nanocellulose. IR helped in characterizing the chemical structure by recognizing the functional groups present in each investigated sample. IR spectra of cellulose, hemicellulose, and lignin components were studied previously in the literature [37; 38; 39; 40; 41]. Typical functional groups and corresponding bands for each component are listed elsewhere [39; 40; 42]. All characterized samples showed main absorbance regions. The first one was at low range of 700-1800, and the second one at higher range between 2700 and 3500 wave number/cm approximately. Very narrow ranges between 2200 and 2400 wave number/cm were exhibited as well. Specific absorption peaks could be recognized for each particular constituent of the lignocellulosic texture (Figure 3). For the three components of lignocellulosic tissue (cellulose, hemicellulose, and lignin), hydroxyl group stretching vibrations were found between 3000 cm\({}^{-1}\) and 3500 cm\({}^{-1}\). Peak intensity in hydrolyzed poplar (Figure 3B) was dramatically higher than n non-hydrolyzed poplar (Figure 3A).