Dottorato in MODELLI MATEMATICI PER L'INGEGNERIA, ELETTROMAGNETISMO E
NANOSCIENZE

Titolo della tesi: Extraction, Synthesis and Characterization of Nanocellulose: Applications in Sustainable Agriculture and Cultural Heritage Conservation

Recently the use of biopolymers is becoming increasingly popular and necessary to combat the many environmental problems. Among these biopolymers, due to their renewability, sustainability, and eco-friendliness, cellulose nanomaterials are capturing the interest of research world. In this work, cellulose nanocrystals (CNC) were extracted from different natural sources, such as tomato plant residue (TPR), olive leaves (OL) and artichoke waste (AW) by acid hydrolysis and used to produce new multifunctional nanocomposite materials for different applications. All the agricultural waste were kindly provided by some small and medium agricultural holdings of the Lazio region, thanks to the collaboration with NanoShare Srl, the Industrial Partner of this PhD project. Chemical and morphological analyses of the extracted CNC_TPR, CNC_OL and CNC_A and of the two commercial references CNC_HMI and CNC_NG were performed using Fourier Transform-Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Moreover, the Sub-micron X-ray Microscopy (XRM) was carried out to obtain the 3D reconstruction of nanocrystals extracted from TPR, which turned out to be the best nanocrystals among those extracted. Once characterized, some of these nanocelluloses were used for different purposes; firstly, new cellulosic nanostructured systems for drug delivery for plants were synthesized, exploiting the antifungal action of abietic acid and of its derivatives against Aspergillus flavus, one of the most common pathogens of the local crops of kiwifruit. The antifungal activity of the synthesized compound NC_7, obtained by direct functionalization of nanocellulose with abietic acid as demonstrating by Raman Spectroscopy, was tested in vitro, showing unsatisfactory results because the DMSO, the solvent in which was dissolved our product, was the first agent to inhibit the growth of A. flavus. After that, the nanocellulose was also used in the field of cultural heritage, to treat degraded ancient wood belonging to a beam of a 16th century villa, and kindly provided by the Cabinet of Scientific Research applied to Cultural Heritage of Vatican Museums. The aim of this experiment was to provide a sustainable alternative to synthetic products usually used for the recovery and conservation of wooden works of art, such as Paraloid B-72 and Regalrez 1126, demonstrating by the colorimetric analysis the more effectiveness of this nanocellulosic protective treatment against the visual aging, and by SEM analysis its consolidating capacity. Moreover, a composite material based on nanocellulose (NC) and graphene oxide (GO) was synthesized, with the aim to obtain a nanocellulosic multifunctional material (GONC), capable to offering an ultraviolet shield against the harmful action of UV-rays, and therefore applicable for many purposes. To do this, two nanocelluloses were used, both the commercial CNC_HMI and the extracted CNC_TPR, in order to compare the respective GONC solutions and to assess the differences due to the different nature of the starting nanocellulose. Finally, once characterized by SEM and AFM, and evaluated their UV-shielding power by UV-vis Spectroscopy, the multifunctional solutions of GONC_HMI and GONC_TPR were applied for the treatment of some degraded wood samples belonging to a Perugino canvas and provided by the Cabinet of Scientific Research applied to Cultural Heritage of Vatican Museums. In this case, the effectiveness of these new composite solutions, both as fillers and as protective agents against UV-rays for ancient wooden works of art, was studied. The SEM characterization of treated wood allowed to observe the different morphology of the treated surfaces in function of the product applied, and the texture of these treatment solutions. Moreover, the AFM – force curve analysis allowed to obtain information about the wood elasticity variation in function of the different product applied, showing greater local stiffness for the samples treated with extracted nanocellulose-based products. Finally, the XRM analysis provided information about the real penetration of the nanocellulose multifunctional solutions into the treated wood, their pore filling capacity, and therefore their effectiveness as consolidants of degraded wood. To conclude, this thesis provides a detailed research study on nanocellulose, its extraction, characterization, and innovative applications, both as it is and after being functionalized for the various purposes mentioned above; in addition, at the end of this dissertation there is an Annex regarding the case study of chitosan as a natural biopolymer for drug delivery, demonstrating the importance and effectiveness of these bionanomaterials used as carrier for drug delivery, whether it is human medicines or plant protection products.