Nanocellulose is known to act as a platform for the in-situ formation of metal oxide nanoparticles, where the multiple components of the resultant hybrids act synergistically toward specific applications. However, typical mineralization reactions require hydrothermal conditions or addition of further reducing agents. Herein, we demonstrate that carboxylated cellulose nanofibril-based films can spontaneously grow functional metal oxide nanoparticles during the adsorption of heavy metal ions from water, without the need of any further chemicals or temperature. Despite the apparent universality of this behavior with different metal ions, this work focuses on studying the in-situ formation of copper oxide nanoparticles on TOCNF films as well as the resultant hybrid films with improved functionality toward dye removal from water and antimicrobial activity. Using a combination of cutting-edge techniques (e.g., in-situ SAXS and QCMD) to systematically follow the nanoparticle formation on the nanocellulosic films in real time, we suggest a plausible mechanism of assembly. Our results confirm that carboxylated cellulose nanofibril films act as universal substrate for the formation of metal oxide nanoparticles, and thus hybrid nanomaterials, during metal ion adsorption processes. This phenomenon enables the upcycling of nanocellulosic materials through multistage applications, thus increasing its sustainability and efficiency in terms of an optimal use of resources.

In this work, we identify and characterize a new intriguing capability of carboxylated cellulose nanofibrils that could be exploited to design smart nanomaterials with tuned response properties for specific applications. Cellulose nanofibrils undergo a multivalent counter-ion induced re-entrant behavior at a specific multivalent metal salt concentration. This effect is manifested as an abrupt increase in the strength of the hydrogel that returns upon a further increment of salt concentration. We systematically study this phenomenon using dynamic light scattering, small-angle X-ray scattering, and molecular dynamics simulations based on a reactive force field. We find that the transitions in the nanofibril microstructure are mainly because of the perturbing actions of multivalent metal ions that induce conformational changes of the nanocellulosic chains and thus new packing arrangements. These new aggregation states also cause changes in the thermal and mechanical properties as well as wettability of the resulting films, upon water evaporation. Our results provide guidelines for the fabrication of cellulose-based films with variable properties by the simple addition of multivalent ions.

Hybrid materials from nanocellulose, lignin, and surface- grafted zwitterionic poly(sulfobetaine methacrylate) (PSBMA) chains are prepared to attain antifouling bio-based nanomaterials with enhanced antibacterial performance. The grafting of PSBMA from both cellulose and lignocellulose nanocrystals (CNC and LCNC, respectively) is attempted; however, the materials' analysis with FTIR, XPS, and solid-state C-13 NMR reveals that the grafting on LCNC is negligible. Antifouling and antibacterial performances of CNC and LCNC, as well as PSBMA-grafted CNC, are evaluated by using quartz crystal microbalance with dissipation monitoring, confocal microscopy, and the agar diffusion method using bovine serum albumin and E. coli ACTT 8937 as protein model and bacterial model, respectively. The results demonstrate that the grafting of CNC with PSBMA improves the antifouling and antibacterial activity of the material compared to pristine CNC and LCNC.

Low-concentration oil-in-water emulsions stabilized by cellulose nanofibrils (CNFs) extracted from primary plant cell wall materials are used to prepare thin biobased CNF–oil composite films by solvent casting. Flexible, transparent, and biodegradable composite films are obtained, with increased thermal stability (up to 300 °C) as the oil concentration increases. Examination of the microstructure demonstrates a clear dependency on the oil content, as a multilayered structure where the oil phase trapped between two layers of CNFs is appreciated at high oil concentrations. The embedded oil significantly influences the mechanical and wetting properties of the films, confirming their potential for use in packaging systems. Encapsulation of curcumin in the composite films leads to an increased antioxidant (up to 30% radical scavenging activity) and antimicrobial activity, inhibiting the growth of foodborne bacteria such as Escherichia coli. The resulting composite films show promising results in the field of active packaging for applications in the food, pharmaceutical, and cosmetic industries.

Microporous (<2 nm) crystalline aluminosilicates in the form of zeolites offer a great potential as efficient adsorbents for atmospheric CO2 in the eminent battle against global warming and climate change. The processability of conventional zeolite powders is, however, poor, which limits their implementation in many applications, such as in gas filtration industrial systems. In this work, we overcome this issue through the preparation of hybrid foams using mesoporous/macroporous supporting materials based on the strong network properties of gelatin/nanocellulose, which can support ultrahigh loadings of silicalite-1, used as a model sorbent nanomaterial. We achieved up to 90 wt % of zeolite content and a microporous/mesoporous/macroporous hybrid material. The application of hybrid foams for selective CO2 sorption exhibits a linear relationship between the zeolite content and CO2 adsorption capacity and high selectivity over N2, where the gelatin/nanocellulose foam efficiently supports the zeolite crystals without apparently blocking their pores.

Nanocellulose has been lately considered as the “Holy-Grail” in the design of sustainable materials due to its bio-origin and an unprecedented combination of prominent features, including good mechanical properties, anisotropy and versatile surface chemistry. In addition, nanocellulose in the form of cellulose nanofibrils, can adopt variable structures and morphologies depending on the processing technique, such as aerogels, films and monoliths.

However, there are limitations that hinder the implementation of cellulose nanofibrils in “real-life applications”, such as inherent interaction with bacteria and proteins, thus leading to surface-fouling; and loss of integrity due to water-induced swelling. A way to overcome these challenges, and provide further functionality, is through hybridization strategies, at which the multiple components act synergistically towards specific properties and applications. In this thesis, the aim is to present multiple strategies for the synthesis of novel cellulose nanofibril-based hybrid materials, in the form of 2D-films and 3D-foams, towards their employment for separation applications or active food packaging.

A novel strategy to surface-functionalize cellulose nanofibril-membranes is proposed via grafting zwitterionic polymer brushes of poly (cysteine methacrylate). The modification can suppress the absorption of proteins in an 85%, as well as decreasing the adhesion of bacteria in an 87%, while introducing antimicrobial properties, as demonstrated against S. aureus.

The spontaneous formation of functional metal oxide nanoparticles occurring in situ on cellulose nanofibrils-films during the adsorption of metal ions from water is investigated, which occurs without the additional use of chemicals or temperature. Notably, this process not only enables the upcycling of materials through multi-stage applications, but also provides a cost-effective method to prepare multifunctional hybrid materials with enhanced dye-removal/antimicrobial activity.

The processing of functional composite films from cellulose nanofibril-stabilized Pickering emulsions and their suitability to be used as active edible barriers was demonstrated. The presence of oil in the films fine-tuned the properties of the films, as well as acted as the medium to encapsulate bio-active hydrophobic compounds, providing further functionality such as antioxidant and antimicrobial properties.

Anisotropic porous hybrid foams with ultra-high loading capacity of sorbents (e.g., zeolites and metal-organic frameworks) were produced via unidirectional freeze-casting method using cellulose nanofibrils/gelatin as template material. The foams indeed exhibited ultra-high loading capacity of sorbent nanomaterials, a linear relationship between sorbent content and CO2 adsorption capacity, and high CO2/N2 selectivity.

The last decades have been witness of an ever-growing interests for the synthesis and application of metal-organic frameworks (MOFs). However, most of the current synthetic procedures produce MOFs in powder state. In this work, hybrid foams were fabricated via in situ synthesis of leaf-like zeolitic imidazolate frameworks (ZIF-L) into nanocellulose at room temperature using water as solvent, followed by a gelatin matrix incorporation and freeze-drying. The foams are ultralight weight and are highly porous with densities ranging from 19.18 to 37.4 kg.m(-3). The shapeability, hierarchical porosity, and low density of the formed foams offer promising potentials for applications such as CO2 sorption. The dispersion of ZIF-L into the cellulose network increases the material accessibility and may open new venues for further MOFs processing.

The deposition of a thin layer of graphene oxide onto cellulose nanofibril membranes, to form CNF-GO layered-composite membranes, dramatically enhances their wet-mechanical stability, water flux and capacity to adsorb water pollutants (P. Liu, C. Zhu and A. P. Mathew, J. Hazard. Mater., 2019, 371, 484-493). In this work, we studied in real time the behavior of these layered membranes during filtration of water and metal ion solutions by means of in situ SAXS and reactive molecular dynamics (ReaxFF) computational simulations. SAXS confirms that the GO layers limit the swelling and structural deformations of CNFs during filtration of aqueous solutions. Moreover, during filtration of metal ion solutions, the connection of the CNF-GO network becomes highly complex mass-fractal like, with an increment in the correlation length. In addition, after ion adsorption, the SAXS data revealed apparent formation of nanoparticles during the drying stage and particle size increase as a function of time during drying. The molecular dynamics simulations, on the other hand, provide a deep insight into the assembly of both components, as well as elucidating the motion of the metal ions that potentially lead to the formation of metal clusters during adsorption, confirming the synergistic behavior of GO and CNFs for water purification applications.

Rising sustainability demands the search of new low-market-value sources of lignocellulosic biomass as raw material for nanocellulose processing. In this paper, we accordingly propose the isolation of nanocellulose from Prosopis juliflora, an abundant but environmentally undesired tree. P. juliflora wood was powered, refined by steam explosion and bleaching, and subsequently used to isolate cellulose nanocrystals and nanofibers by means of acid hydrolysis and mechanical fibrillation. The derived nanocrystals had a rod-shaped structure with an average diameter of 20 nm and length of 150 nm, whereas the nanofibers had a diameter of 10 nm and length in micron size. Moreover, we report a simple method to isolate nanolignocellulose by using partially bleached P. juliflora as feedstock. The presence of lignin provided antioxidant and antimicrobial activity to nanocellulose, as well as hydrophobicity and increased thermal stability. The study demonstrates the successful use of P. juliflora to extract functional nanomaterials, which compensate for its environmental concern and declining market interest.

This article proposes a strategy to functionalize cellulose nanocrystals by means of plasma-surface modification utilizing monomers of different nature: caprolactone, styrene and farnesene. The surface characteristics of the nanocrystals were studied by different techniques including XPS, FTIR and STEM, demonstrating that this technique allows a successful functionalization, yielding homogenous functionalization which does not alter the rod-like shape of the nanocrystals, and therefore their anisotropic behavior. We have furthermore studied the employment of the modified nanocrystals as reinforcement additive of ABS, which significantly enhanced the impact resistance of the thermoplastic, which could have great implications for industrial applications.