## 2 Materials and Methods
### Nanomaterialssynthesis  
#### 2.2.1 Cellulose Extraction and CNC Synthesis  
Hazelnut tree pruning shoots (HP) and hazelnut shells (HS) were used for cellulose extraction and purification. HP were firstly washed in distilled water several times in order to remove the powder and environmental contaminations. Subsequently, the pruning residues were treated for 72 h at room temperature (RT) with 1% _w/v_ of sodium hydroxide (NaOH) (purity \(\geq\) 98%, pellets, anhydrous, CAS No: 1310-73-2) solution and then for 2 h at 98 \({}^{\circ}\)C with 5% _w/v_ of NaOH solution to remove the external lignin components. The soaked lignocellulosic materials were chopped with a mechanic shredder in order to obtain individualized fibers (length around 10-15 mm). The fibers were dried at 60 \({}^{\circ}\)C for 24 h. Afterwards, the bleaching treatment has been performed: the fibers were bleached with 5% _w/v_ of sodium chlorite (NaClO\({}_{2}\)) (purity \(\geq\) 80%, powder, CAS No: 7758-19-2) (liquor ratio 1:50) at 80 \({}^{\circ}\)C for 120 min [53]. The solution pH was adjusted to 3.5 by means acetic acid before the addition of the biomass. At the end of bleaching treatment, the material was washed several times and treated with sodium bisulfate (NaHSO\({}_{4}\)) (technical grade, powder, powder, CAS No: 7681-38-1) solution at 5% _w/v_ for 30 min at RT (liquor ratio 1:40), washed again with deionized water, and treated with NaOH solution at 17.5% _w/v_ for 20 min at RT (liquor ratio 1:50) in order to remove lignin and hemicellulose components [22]. The resulting material was finally dried at 60\({}^{\circ}\)C for 24 h. Dried and cleaned HS were used for cellulose extraction. HS were milled in a bench-scale mill to make the biomass more prone/accessible to chemical pretreatments and sifted with a 500-mesh sieve to maintain the size uniformity of powdered shells. These powdered HS were subjected to chemical treatment for cellulose purification as previously reported [54; 55]. HS were first subjected to dewaxing by using a boiling solution of benzene:methanol (80:20 ratio) (purity \(\geq\) 99.8%, liquid, anhydrous, CAS No: 71-43-2) (purity \(\geq\) 99.8%, liquid, anhydrous, CAS No: 67-56-1) for 6 h with magnetic stirring (powder-solution ratio 3:10). This step was carried out to remove the surface wax, to allow the solvents to better penetrate the matrix [56]. The dewaxed shells were treated with 1 M NaOH solution under magnetic stirring at 85\({}^{\circ}\)C for 4 h to first remove the excess of lignin and hemicellulose (powder-solution ratio 1:10). This alkali treatment was repeated for 3-4 times, and the final product was washed with distilled water at each step. The resulting material was subjected to the bleaching step with 1.7% sodium chlorite solution at 80 \({}^{\circ}\)C for 6 h, to further remove lignin (powder-solution ratio 1:20). The pH was adjusted to 3.5 by means of glacial acetic acid (purity \(\geq\) 99%, liquid, CAS No: 64-19-7). This process was repeated for 3-4 times too, and the obtained product was filtered and dried for 24 h at 60 \({}^{\circ}\)C. The final dried products obtained from pruning and shells residue are considered as chemically purified cellulose (CPC-HP and CPC-HS). The cellulose nanocrystals were synthesized from chemical purified cellulose extracted from both pruning shoots and hazelnut shells by following the acid hydrolysis method. Twenty grams of CPC-HP and CPC-HS were treated with 175 mL of 64 wt% sulphuric acid (purity \(\geq\) 95-98%, liquid, CAS No: 7664-93-9) solution for 30 min at 45 \({}^{\circ}\)C under vigorous stirring. The reaction was stopped by pouring the hydrolyzed cellulose in distilled water. The aqueous suspension of hydrolyzed nanocellulose had been left to precipitate for 2 days. The supernatant was discarded, while the remaining aqueous CNCs suspension was dialyzed with nitrocellulose membranes against distilled water for several days, until the pH reached 6-7.