Interfacial complexation of nanocellulose into functional filaments and their potential applications

Abstract In nature, diverse materials, such as bone, wood, and mollusk shells, are constructed by the assembly of micro- and/or nanoscopic biological building blocks into hierarchical structures. Inspired by these designs in nature, the conversion of bio-based colloidal nanoparticles into nanocomposites with pre-designed structure is attracting more and more attention. Of particular recent interest are continuous natural fibers and filaments, such as spider silk and the microfibrils in plant cells. Nanocellulose (NC), as one of the most promising biosourced nanomaterials, has become an appealing building block for the fabrication of green materials due to its abundance, biocompatibility, and tailorable surface chemistry and morphology. In the current thesis, the fabrication of NC-based nano-structured filaments via a simple and green interfacial nanoparticle complexation (INC) method was introduced. Moreover, the feasibility of filament formation via the INC method using different oppositely charged nanoparticle pairs was demonstrated, including oppositely charged NCs (Papers Ⅰ and Ⅱ), cationic chitin nanocrystals with anionic NC (Paper Ⅲ), and cationic NC combined with graphene oxide (Paper Ⅳ). Furthermore, different functional NC-based filaments were synthesized by incorporating different additives, including an antitumor drug (doxorubicin hydrochloride, DOX), silver nanoparticles (Ag NPs), and carbon nanotubes (CNTs) into NC-based filaments during the INC process. The filaments demonstrated potential applications in drug delivery, antimicrobial materials, and electronics. The developed INC method may not only provide new pathways for engineering continuous filaments from other oppositely charged nanoparticle pairs (such as DNA and protein nanofibrils) but pave the way towards a completely new class of green materials (fibers, capsules, and membranes) based on oppositely charged colloidal nanoparticles.Tiivistelmä Luonnossa useat materiaalit, kuten luu, puu ja hyönteisten kuori, rakentuvat mikro- ja / tai nanokokoisten biologisten rakennuspalikoiden järjestäytyessä hierarkkisiksi rakenteiksi. Nämä materiaalit ovat innoittaneet kehittämään nanokomposiitteja, jotka perustuvat biopohjaisiin kolloidisiin nanopartikkeleihin. Viime aikoina erityisen mielenkiinnon kohteena ovat olleet luonnonkuidut ja jatkuvarakenteiset filamentit, kuten hämähäkin silkki ja kasvisolujen mikrofibrillit. Nanoselluloosasta, joka on yksi lupaavimmista biopohjaisista nanomateriaaleista, on tullut eräs tärkeimmistä raaka-aineista uusien vihreiden materiaalien valmistukseen sen runsauden, biologisen yhteensopivuuden ja muokattavan pinta-kemian ja morfologian vuoksi. Tässä väitöstyössä on tutkittu nanoselluloosapohjaisten filamenttien valmistusta yksinkertaisella ja vihreällä ”interfacial nanoparticle complexation”-menetelmällä (INC). Työssä on erityisesti selvitetty filamenttien muodostumista INC-menetelmällä käyttämällä erilaisia vastakkaisesti varautuneita nanohiukkaspareja, kuten vastakkaismerkkisiä nanoselluloosapartikkeleita NC (Paperi Ⅰ ja Ⅱ), kationisia kitiininanokiteitä yhdessä anionisen (Paperi Ⅲ), ja kationinen nanoselluloosan ja grafeenioksidin kanssa (Paperi Ⅳ). Lisäksi nanoselluloosasta valmistettujen filamenttien ominaisuuksia muokattiin INC-prosessin aikana erilaisilla lisäaineilla kuten lääkeaineella (doksorubisiinihydrokloridi, DOX), hopeananohiukkasilla (Ag NPs) ja hiilinanoputkilla (CNT). Näitä funktionaalisia filamentteja voidaan hyödyntää mahdollisesti lääkkeiden annostelussa, antimikrobisissa materiaaleissa ja elektroniikassa. Kehitetty INC-menetelmä tarjoaa uusia reittejä filamenttien valmistukselle myös muista vastakkaisesti varautuneista nanopartikkeleista kuten DNA:sta ja proteiineista ja mahdollistaa täysin uusien vihreiden materiaalien (mm. kuidut, kapselit ja membraanit) kehityksen vastakkaisesti varautuneisiin kolloidiset nanopartikkeleihin perustuen

Water-resistant nanopaper with tunable water barrier and mechanical properties from assembled complexes of oppositely charged cellulosic nanomaterials

Abstract Owing to the intrinsic hydrophilicity of nanocellulose, films and nanopapers prepared from cellulosic nanomaterials exhibit weak mechanical strength when exposed to high-moisture conditions. In this study, an approach for designing a water resistant, assembled nanopaper through controlled and irreversible aqueous complexation of oppositely charged cellulose nanoconstituents, i.e., cationic cellulose nanocrystals (AH-CNC) and anionic cellulose nanofibers (TO-CNF), is proposed. The fabrication process and features of the nanopaper can be adjusted by altering of the AH-CNC/TO-CNF ratio. For example, the draining time during the filtration of a nanopaper decreased dramatically (480–10 min) when the dosage of nanocelluloses resulted in charge compensation. This dosage also reduced the swelling of the nanopaper. After all charged groups were neutralized, a nanopaper with a wet strength of 11 ± 3 MPa was obtained when immersed in water for 24 h. Furthermore, the electrostatic interaction between the charged nano-entities enhanced the mechanical properties of the nanopaper in dry state (the maximum of tensile strength was 174 ± 3 MPa) and resulted in improved water barrier properties (water vapor transmission rate of 1683 g μm m⁻² d⁻¹). This straightforward method based on simply aqueous mixing of two oppositely charged nanomaterials may provide a new pathway for the fabrication of various functionalized films and sheets with advanced characteristics from different type of charged nanoparticles and colloids

Comparison of acidic deep eutectic solvents in production of chitin nanocrystals

Abstract Five different acidic deep eutectic solvents (DESs) composed of choline chloride and organic acids were applied to fabricate chitin nanocrystals (ChNCs). All DESs resulted in high transmittance and stable ChNCs suspensions with very high mass yield ranging from 78 % to 87.5 % under proper reaction conditions. The acidic DESs had a dual role in ChNCs fabrication, i.e. they promoted hydrolysis of chitin and acted as an acylation reagent. Physicochemical characterization of chitin revealed that the removal of amorphous area during DES treatments led to increased crystallinity of ChNCs and a dimension diversity correlated the DES used. The average diameter and length of individual ChNCs ranged from 42 nm to 49 nm and from 257 nm to 670 nm, respectively. The thermal stability of ChNCs was comparable to that of pristine chitin. Thus, acidic DESs showed to be non-toxic and environmentally benign solvents for production of functionalized chitin nanocrystals

Conductive hybrid filaments of carbon nanotubes, chitin nanocrystals and cellulose nanofibers formed by interfacial nanoparticle complexation

Abstract In this paper, anionic TEMPO-oxidized cellulose nanofibers (TO-CNFs) and cationic, partially deacetylated, chitin nanocrystals (ChNCs) were used to fabricate continuous composite filaments (TO-CNF/ChNC filament) with a straightforward and sustainable aqueous process based on the interfacial nanoparticle complexation (INC) of oppositely charged nano-constituents. In particular, the role of TO-CNF and ChNC concentrations in filament drawing and the effect of drawing speed on the mechanical properties of composite filaments were investigated. Moreover, conductive filaments were fabricated by mixing single walled carbon nanotubes (SWCNTs) with TO-CNF dispersion and further complexing with the ChNC aqueous suspension. A conductive filament with an electrical conductivity of 2056 S/m was obtained. However, the increase in the SWCNTs content reduced the mechanical properties of the formed filament compared to neat TO-CNF/ChNC filament. This study not only introduces a new nanoparticle candidate to prepare filaments based on INC method but also provides potential advanced and alternative green filament to be used as wearable electronics in biomedical area

Efficient hydrolysis of chitin in a deep eutectic solvent synergism for production of chitin nanocrystals

Abstract A deep eutectic solvent (DES) derived from ferric chloride hexahydrate and betaine chloride (molar ratio of 1:1) was used as hydrolytic media for production of chitin nanocrystals (ChNCs) with a high yield (up to 88.5%). The synergistic effect of Lewis acid and released Brønsted acid from betaine hydrochloride enabled the efficient hydrolysis of chitin for production of ChNCs coupled with ultrasonication with low energy consumption. The obtained ChNCs were with an average diameter of 10 nm and length of 268 nm, and a crystallinity of 89.2% with optimal synthesis conditions (at 100 °C for 1 h with chitin-to-DES mass ratio of 1:20). The ChNCs were further investigated as efficient emulsion stabilizers, and they resulted in stable o/w emulsions even at a high oil content of 50% with a low ChNC dosage of 1 mg/g. Therefore, a potential approach based on a DES on the production of chitin-based nanoparticles as emulsifiers is introduced

Facile synthesis of palladium and gold nanoparticles by using dialdehyde nanocellulose as template and reducing agent

Abstract Cellulose nanofibrils (CNFs) were firstly prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation and further oxidized to 2,3-dialdehyde nanocelluloses (DANCs) by periodate oxidation. Furthermore, by using DANCs as reducing as well as stabilizing agent, palladium (Pd) and gold (Au) nanoparticles (NPs) supported on nanocellulose (PdNPs@NC and AuNPs@NC) were synthesized, respectively. The reduction of Pd or Au ions to its metallic form by DANCs was confirmed by UV–vis spectra, XRD, and XPS. TEM results showed that Pd and Au NPs were homogenously deposited onto cellulose nanofibrils, respectively. The catalytic performance of PdNPs@NC was further investigated by Suzuki coupling reaction. The product yield of the Suzuki coupling reaction between aryl bromides and phenyl boronic acid was more than 90% after 1 h with 0.1 mol% PdNPs@NC catalyst, which demonstrated that the synthesized PdNPs@NC nanohybrid could be successfully applied in Suzuki coupling reaction with an efficient catalytic activity

Enhancement of the nanofibrillation of birch cellulose pretreated with natural deep eutectic solvent

Abstract n this study, we demonstrate a new bio-derived and non-toxic deep eutectic solvent composed of betaine hydrochloride (Bh) and glycerol (Gl) as a pretreatment medium for birch cellulose (Betula pendula) to prepare cellulose nanofibers (CNFs) using microfluidization. The co-solvent could readily penetrate into cellulose to swell the fibrillar structure and weaken the interaction within the hydrogen bond network. Moreover, the cationization of glycerol and cellulose by betaine hydrochloride further enhances the swelling process. All of these effects promote the nanofibrillation of cellulose and reduce the energy demand in CNF production. A high CNF mass yield of up to 72.5 % was obtained through co-solvent pretreatment using a Bh-to-Gl mole ratio of 1:2 at 150 °C for 1 h. The mole amount of betaine hydrochloride was noted to affect the nanofibrillation process and stability of the CNF suspension. The obtained CNFs possessed a cationic charge of 0.05–0.06 mmol/g, a diameter of 17–20 nm, and a degree of crystallinity of 67.7–74.4 %. The CNFs displayed good thermal stability comparable to that of the pristine cellulose. Thus, this study provides a green and efficient swelling strategy for producing CNFs with a low cationic charge density

Self-assembly of graphene oxide and cellulose nanocrystals into continuous filament via interfacial nanoparticle complexation

Abstract The present work demonstrates the spinning of conductive filaments from oppositely charged nano-scale entities, i.e., cationic cellulose nanocrystals (CNC) and anionic graphene oxide (GO), via interfacial nanoparticle complexation. Especially, the role of CNC and GO concentration in filament formation was investigated. Moreover, the chemical structure, morphology and composition of formed CNC/GO composite filaments were further characterized. The positively charged CNC formed firstly a complex film with negatively charged GO flake and then the complexed structures were further assembled into macroscale hybrid filament (diameter about 20 to 50 μm). After chemical reduction of the hybrid filament, conductive filaments with an average tensile strength of 109 ± 8 MPa and electrical conductivity of 3298 ± 167 S/m were obtained. The presented approach provides a new pathway to understand the interaction of GO and nanocellulose, and to design macroscopic, assembled and functionalized architectures of GO and nanocellulose composites

Size exclusion and affinity-based removal of nanoparticles with electrospun cellulose acetate membranes infused with functionalized cellulose nanocrystals

Abstract Membrane filtration and affinity-based adsorption are the two most used strategies in separation technologies. Here, µm-thick multifunctional and sustainable composite membranes of electrospun cellulose acetate (CA) infused with functionalized, anionic, and cationic cellulose nanocrystals (CNCs) with enhanced wettability, tensile strength, and excellent retention capacities were designed. CNCs could uniformly impregnate into the three-dimensional CA network to effectively improve its properties. The impregnation of cationic CNCs at 0.5 wt% concentration drastically increased the tensile strength (1669%) while maintaining high permeation flux of 9400 Lm-2h-1 which is remarkable with cellulose modified electrospun membranes. The membranes infused with anionic CNCs exhibited a particle retention efficiency of 96% for 500 nm and 77% for 100 nm latex beads whilst the cationic CNC membranes exhibited a combined particle retention strategy using selectivity and size exclusion with a retention of >81% with 100 nm latex beads and 80% with ∼50 nm silver nanoparticles. We envision that the developed multifunctional membranes can be utilized for affinity-based and size-exclusion filtration to selectively trap bacteria or substances of biological significance

Nanostructured and advanced designs from biomass and mineral residues:multifunctional biopolymer hydrogels and hybrid films reinforced with exfoliated mica nanosheets

Abstract Transforming potential waste materials into high-value-added sustainable materials with advanced properties is one of the key targets of the emerging green circular economy. Natural mica (muscovite) is abundant in the mining industry, which is commonly regarded as a byproduct and gangue mineral flowing to waste rock and mine tailings. Similarly, chitin is the second-most abundant biomass resource on Earth after cellulose, extracted as a byproduct from the exoskeleton of crustaceans, fungal mycelia, and mushroom wastes. In this study, exfoliated mica nanosheets were individualized using a mechanochemical process and incorporated into regenerated chitin matrix through an alkali dissolution system (KOH/urea) to result in a multifunctional, hybrid hydrogel, and film design. The hydrogels displayed a hierarchical and open nanoporous structure comprising an enhanced, load-bearing double-cross-linked polymeric chitin network strengthened by mica nanosheets possessing high stiffness after high-temperature curing, while the hybrid films (HFs) exhibited favorable UV-shielding properties, optical transparency, and dielectric properties. These hybrid designs derived from industrial residues pave the way toward sustainable applications for many future purposes, such as wearable devices and tissue engineering/drug delivery