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14 pages, 4002 KiB

Open AccessArticle

Ultra-Porous Nanocellulose Foams: A Facile and Scalable Fabrication Approach

by Carlo Antonini, Tingting Wu, Tanja Zimmermann, Abderrahmane Kherbeche, Marie-Jean Thoraval, Gustav Nyström and Thomas Geiger

Nanomaterials 2019, 9(8), 1142; https://doi.org/10.3390/nano9081142 - 9 Aug 2019

Cited by 56 | Viewed by 6392

Abstract

Cellulose nanofibril foams are cellulose-based porous materials with outstanding mechanical properties, resulting from the high strength-to-weight ratio of nanofibrils. Here we report the development of an optimized fabrication process for highly porous cellulose foams, based on a well-controlled freeze-thawing-drying (FTD) process at ambient [...] Read more.

Cellulose nanofibril foams are cellulose-based porous materials with outstanding mechanical properties, resulting from the high strength-to-weight ratio of nanofibrils. Here we report the development of an optimized fabrication process for highly porous cellulose foams, based on a well-controlled freeze-thawing-drying (FTD) process at ambient pressure. This process enables the fabrication of foams with ultra-high porosity, up to 99.4%, density of 10 mg/cm³, and liquid (such as oil) absorption capacity of 100 L/kg. The proposed approach is based on the ice-templating of nanocellulose suspension in water, followed by thawing in ethanol and drying at environmental pressures. As such, the proposed fabrication route overcomes one of the major bottle-necks of the classical freeze-drying approach, by eliminating the energy-demanding vacuum drying step required to avoid wet foam collapse upon drying. As a result, the process is simple, environmentally friendly, and easily scalable. Details of the foam development fabrication process and functionalization are thoroughly discussed, highlighting the main parameters affecting the process, e.g., the concentration of nanocellulose and additives used to control the ice nucleation. The foams are also characterized by mechanical tests and oil absorption measurements, which are used to assess the foam absorption capability as well as the foam porosity. Compound water-in-oil drop impact experiments are used to demonstrate the potential of immiscible liquid separation using cellulose foams. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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12 pages, 3444 KiB

Open AccessArticle

Self-Assembly Fluorescent Cationic Cellulose Nanocomplex via Electrostatic Interaction for the Detection of Fe³⁺ Ions

by Haoying Wang, Xiu Ye and Jinping Zhou

Nanomaterials 2019, 9(2), 279; https://doi.org/10.3390/nano9020279 - 16 Feb 2019

Cited by 8 | Viewed by 3362

Abstract

In this work, an aggregation-induced emission (AIE) sensor for the detection of Fe³⁺ ions was fabricated through the electrostatic interaction between 1,1,2-triphenyl-2-[4-(3-sulfonatopropoxyl)-phenyl]-ethene sodium salt (SPOTPE) and quaternized cellulose (QC). The structure and properties of the SPOTPE/QC nanocomplex were studied by using ¹ [...] Read more.

In this work, an aggregation-induced emission (AIE) sensor for the detection of Fe³⁺ ions was fabricated through the electrostatic interaction between 1,1,2-triphenyl-2-[4-(3-sulfonatopropoxyl)-phenyl]-ethene sodium salt (SPOTPE) and quaternized cellulose (QC). The structure and properties of the SPOTPE/QC nanocomplex were studied by using ¹H NMR, spectrofluorophotometer, transmission electron microscopy (TEM), and dynamic laser light scattering (DLS). An aqueous solution of SPOTPE and QC resulted in a remarkably enhanced cyan fluorescence in comparison to that of the SPOTPE solution. Strong through-space electrostatic interaction between SPOTPE and QC is the main cause for the fluorescence emerging. The fluorescence of the SPOTPE/QC solutions show good stability over a wide pH range of 5.0–10.0. When introducing Fe³⁺ ions into the SPOTPE/QC solution, the fluorescence quenched within 5 s. SPOTPE/QC solutions exhibited high selectivity and sensitivity for the detection of Fe³⁺ ions with ignored interferences from other ions, and the detection limit was determined to be 2.92 × 10⁻⁶ M. The quenching mechanism was confirmed to be the consequence of the binding interactions between Fe³⁺ ions and SPOTPE/QC complex. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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13 pages, 2796 KiB

Open AccessArticle

Highly Charged Cellulose Nanocrystals Applied as A Water Treatment Flocculant

by Dana Morantes, Efrén Muñoz, Doron Kam and Oded Shoseyov

Nanomaterials 2019, 9(2), 272; https://doi.org/10.3390/nano9020272 - 15 Feb 2019

Cited by 52 | Viewed by 5866

Abstract

Various cellulosic materials have replaced petroleum-derived polymers, offering natural and sustainable alternatives. Among them, cellulose nanocrystals (CNC) feature an easily modifiable surface, enabling the exploration of a wide spectrum of applications. In this work, the quaternary agent 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) was used as [...] Read more.

Various cellulosic materials have replaced petroleum-derived polymers, offering natural and sustainable alternatives. Among them, cellulose nanocrystals (CNC) feature an easily modifiable surface, enabling the exploration of a wide spectrum of applications. In this work, the quaternary agent 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) was used as a cationic graft on CNCs, to form a novel water treatment flocculant. The resulting material was chemically and structurally characterized by the determination of Zeta potential; degree of substitution by elemental analysis; hydrodynamic size by dynamic light scattering (DLS) and infrared spectroscopy with Fourier Transform Infrared (FT-IR); and X-ray diffraction (XRD). The flocculation capacity of cationic cellulose nanocrystals (CNC-EPTMAC) was evaluated in a jar test filled with an 0.25 wt.% silica (SiO2) suspension. CNC-EPTMAC proved to be an effective water treatment flocculant, reducing turbidity by up to 99.7% at a concentration of only 2 ppm. This work demonstrates a natural and environmentally sustainable alternative to homologous commercial flocculants. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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14 pages, 2608 KiB

Open AccessArticle

Oil-in-Water Emulsions Stabilized by Cellulose Nanofibrils—The Effects of Ionic Strength and pH

by Ragnhild Aaen, Fredrik Wernersson Brodin, Sébastien Simon, Ellinor Bævre Heggset and Kristin Syverud

Nanomaterials 2019, 9(2), 259; https://doi.org/10.3390/nano9020259 - 14 Feb 2019

Cited by 50 | Viewed by 4976

Abstract

Pickering o/w emulsions prepared with 40 wt % rapeseed oil were stabilized with the use of low charged enzymatically treated cellulose nanofibrils (CNFs) and highly charged 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized CNFs. The emulsion-forming abilities and storage stability of the two qualities were tested in the [...] Read more.

Pickering o/w emulsions prepared with 40 wt % rapeseed oil were stabilized with the use of low charged enzymatically treated cellulose nanofibrils (CNFs) and highly charged 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized CNFs. The emulsion-forming abilities and storage stability of the two qualities were tested in the presence of NaCl and acetic acid, at concentrations relevant to food applications. Food emulsions may be an important future application area for CNFs due to their availability and excellent viscosifying abilities. The emulsion characterization was carried out by visual inspection, light microscopy, viscosity measurements, dynamic light scattering and mild centrifugation, which showed that stable emulsions could be obtained for both CNF qualities in the absence of salt and acid. In addition, the enzymatically stabilized CNFs were able to stabilize emulsions in the presence of acid and NaCl, with little change in the appearance or droplet size distribution over one month of storage at room temperature. The work showed that enzymatically treated CNFs could be suitable for use in food systems where NaCl and acid are present, while the more highly charged TEMPO-CNFs might be more suited for other applications, where they can contribute to a high emulsion viscosity even at low concentrations. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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11 pages, 3281 KiB

Open AccessArticle

Biocellulose for Incisional Hernia Repair—An Experimental Pilot Study

by Falk Rauchfuß, Julian Helble, Johanna Bruns, Olaf Dirsch, Uta Dahmen, Michael Ardelt, Utz Settmacher and Hubert Scheuerlein

Nanomaterials 2019, 9(2), 236; https://doi.org/10.3390/nano9020236 - 10 Feb 2019

Cited by 7 | Viewed by 3611

Abstract

Ventral or incisional hernia are a common disease pattern in general surgery. Most commonly, a mesh repair is used for reconstruction, whereby the mesh itself might cause complications, like infections or adhesions. Biological materials, like biocellulose, might reduce these clinical problems substantially. In [...] Read more.

Ventral or incisional hernia are a common disease pattern in general surgery. Most commonly, a mesh repair is used for reconstruction, whereby the mesh itself might cause complications, like infections or adhesions. Biological materials, like biocellulose, might reduce these clinical problems substantially. In this prospective rodent study, a biocellulose mesh (produced by Gluconacetobacter xylinus) was implanted either by a sublay technique or as supplementation of the abdominal wall. After an observation period of 90 days, animals were sacrificed. The adhesions after the reconstruction of the abdominal wall were moderate. The histologic investigations revealed that the biocellulose itself was inert, with a minimal regenerative response surrounding the mesh. The explanted mesh showed a minimal shrinkage (around 15%) as well as a minimal loss of tear-out force, which might be without clinical relevance. This is the first in vivo study describing biocellulose as a suitable mesh for the repair of ventral hernia in two different hernia models. The material seems to be a promising option for solving actual problems in modern hernia surgery. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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18 pages, 3955 KiB

Open AccessArticle

Rapid Water Softening with TEMPO-Oxidized/Phosphorylated Nanopapers

by Andreas Mautner, Thawanrat Kobkeatthawin, Florian Mayer, Christof Plessl, Selestina Gorgieva, Vanja Kokol and Alexander Bismarck

Nanomaterials 2019, 9(2), 136; https://doi.org/10.3390/nano9020136 - 22 Jan 2019

Cited by 25 | Viewed by 4941

Abstract

Water hardness not only constitutes a significant hazard for the functionality of water infrastructure but is also associated with health concerns. Commonly, water hardness is tackled with synthetic ion-exchange resins or membranes that have the drawbacks of requiring the awkward disposal of saturated [...] Read more.

Water hardness not only constitutes a significant hazard for the functionality of water infrastructure but is also associated with health concerns. Commonly, water hardness is tackled with synthetic ion-exchange resins or membranes that have the drawbacks of requiring the awkward disposal of saturated materials and being based on fossil resources. In this work, we present a renewable nanopaper for the purpose of water softening prepared from phosphorylated TEMPO-oxidized cellulose nanofibrils (PT-CNF). Nanopapers were prepared from CNF suspensions in water (PT-CNF nanopapers) or low surface tension organic liquids (ethanol), named EPT-CNF nanopapers, respectively. Nanopaper preparation from ethanol resulted in a significantly increased porosity of the nanopapers enabling much higher permeances: more than 10,000× higher as compared to nanopapers from aqueous suspensions. The adsorption capacity for Ca²⁺ of nanopapers from aqueous suspensions was 17 mg g⁻¹ and 5 mg g⁻¹ for Mg²⁺; however, EPT-CNF nanopapers adsorbed more than 90 mg g⁻¹ Ca²⁺ and almost 70 mg g⁻¹ Mg²⁺. The higher adsorption capacity was a result of the increased accessibility of functional groups in the bulk of the nanopapers caused by the higher porosity of nanopapers prepared from ethanol. The combination of very high permeance and adsorption capacity constitutes a high overall performance of these nanopapers in water softening applications. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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25 pages, 9814 KiB

Open AccessArticle

Functionalized Cellulose Nanocrystal Nanocomposite Membranes with Controlled Interfacial Transport for Improved Reverse Osmosis Performance

by Ethan D. Smith, Keith D. Hendren, James V. Haag IV, E. Johan Foster and Stephen M. Martin

Nanomaterials 2019, 9(1), 125; https://doi.org/10.3390/nano9010125 - 20 Jan 2019

Cited by 44 | Viewed by 7070

Abstract

Thin-film nanocomposite membranes (TFNs) are a recent class of materials that use nanoparticles to provide improvements over traditional thin-film composite (TFC) reverse osmosis membranes by addressing various design challenges, e.g., low flux for brackish water sources, biofouling, etc. In this study, TFNs were [...] Read more.

Thin-film nanocomposite membranes (TFNs) are a recent class of materials that use nanoparticles to provide improvements over traditional thin-film composite (TFC) reverse osmosis membranes by addressing various design challenges, e.g., low flux for brackish water sources, biofouling, etc. In this study, TFNs were produced using as-received cellulose nanocrystals (CNCs) and 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TOCNs) as nanoparticle additives. Cellulose nanocrystals are broadly interesting due to their high aspect ratios, low cost, sustainability, and potential for surface modification. Two methods of membrane fabrication were used in order to study the effects of nanoparticle dispersion on membrane flux and salt rejection: a vacuum filtration method and a monomer dispersion method. In both cases, various quantities of CNCs and TOCNs were incorporated into a polyamide TFC membrane via in-situ interfacial polymerization. The flux and rejection performance of the resulting membranes was evaluated, and the membranes were characterized via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The vacuum filtration method resulted in inconsistent TFN formation with poor nanocrystal dispersion in the polymer. In contrast, the dispersion method resulted in more consistent TFN formation with improvements in both water flux and salt rejection observed. The best improvement was obtained via the monomer dispersion method at 0.5 wt% TOCN loading resulting in a 260% increase in water flux and an increase in salt rejection to 98.98 ± 0.41% compared to 97.53 ± 0.31% for the plain polyamide membrane. The increased flux is attributed to the formation of nanochannels at the interface between the high aspect ratio nanocrystals and the polyamide matrix. These nanochannels serve as rapid transport pathways through the membrane, and can be used to tune selectivity via control of particle/polymer interactions. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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11 pages, 3240 KiB

Open AccessArticle

Manufacture of Highly Transparent and Hazy Cellulose Nanofibril Films via Coating TEMPO-Oxidized Wood Fibers

by Weisheng Yang, Liang Jiao, Wei Liu and Hongqi Dai

Nanomaterials 2019, 9(1), 107; https://doi.org/10.3390/nano9010107 - 16 Jan 2019

Cited by 43 | Viewed by 5484

Abstract

Traditionally, inorganic nanoparticles (SiO₂, TiO₂) have been utilized to tune the optical haze of optoelectronic devices. However, restricted to complex and costly processes for incorporating these nanoparticles, a simple and low-cost approach becomes particularly important. In this work, a [...] Read more.

Traditionally, inorganic nanoparticles (SiO₂, TiO₂) have been utilized to tune the optical haze of optoelectronic devices. However, restricted to complex and costly processes for incorporating these nanoparticles, a simple and low-cost approach becomes particularly important. In this work, a simple, effective, and low-cost method was proposed to improve optical haze of transparent cellulose nanofibril films by directly depositing micro-sized 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized wood fibers (“coating” method). The obtained films had a high total transmittance of 85% and a high haze of 62%. The film samples also showed a high tensile strength of 80 MPa and excellent thermal stability. Dual sides of the obtained films had different microstructures: one side was extremely smooth (root-mean-square roughness of 6.25 nm), and the other was extremely rough (root-mean-square roughness of 918 nm). As a reference, micro-sized TEMPO-oxidized wood fibers and cellulose nanofibrils were mixed to form a transparent and hazy film (“blending” method). These results show that hazy transparent films prepared using the “coating” method exhibit superior application performances than films prepared using the “blending” method. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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13 pages, 20971 KiB

Open AccessArticle

Hydrothermal Synthesis of Cellulose-Derived Carbon Nanospheres from Corn Straw as Anode Materials for Lithium ion Batteries

by Kaifeng Yu, Jingjing Wang, Kexian Song, Xiaofeng Wang, Ce Liang and Yanli Dou

Nanomaterials 2019, 9(1), 93; https://doi.org/10.3390/nano9010093 - 12 Jan 2019

Cited by 46 | Viewed by 6466

Abstract

As a most attractive renewable resource, biomass has the advantages of low pollution, wide distribution and abundant resources, promoting its applications in lithium ion batteries (LIBs). Herein, cellulose-derived carbon nanospheres (CCS) were successfully synthesized by hydrothermal carbonization (HTC) from corn straw for use [...] Read more.

As a most attractive renewable resource, biomass has the advantages of low pollution, wide distribution and abundant resources, promoting its applications in lithium ion batteries (LIBs). Herein, cellulose-derived carbon nanospheres (CCS) were successfully synthesized by hydrothermal carbonization (HTC) from corn straw for use as an anode in LIBs. The uniform distribution and cross-linked structure of carbon nanospheres were obtained by carefully controlling reaction time, which could not only decrease the transport pathway of lithium ions, but also reduce the structural damage caused by the intercalation of lithium ions. Especially, obtained after hydrothermal carbonization for 36 h, those typical characteristics make it deliver excellent cycling stability as well as the notable specific capacity of 577 mA h g⁻¹ after 100 cycles at 0.2C. Hence, this efficient and environment-friendly method for the fabrication of CCS from corn straw could realize the secondary utilization of biomass waste, as well as serve as a new choice for LIBs anode materials. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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22 pages, 4670 KiB

Open AccessArticle

Three-Dimensional Stable Alginate-Nanocellulose Gels for Biomedical Applications: Towards Tunable Mechanical Properties and Cell Growing

by Priscila Siqueira, Éder Siqueira, Ana Elza De Lima, Gilberto Siqueira, Ana Delia Pinzón-Garcia, Ana Paula Lopes, Maria Esperanza Cortés Segura, Augusta Isaac, Fabiano Vargas Pereira and Vagner Roberto Botaro

Nanomaterials 2019, 9(1), 78; https://doi.org/10.3390/nano9010078 - 8 Jan 2019

Cited by 100 | Viewed by 7306

Abstract

Hydrogels have been studied as promising materials in different biomedical applications such as cell culture in tissue engineering or in wound healing. In this work, we synthesized different nanocellulose-alginate hydrogels containing cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals (CNCTs), cellulose nanofibers or TEMPO-oxidized cellulose nanofibers [...] Read more.

Hydrogels have been studied as promising materials in different biomedical applications such as cell culture in tissue engineering or in wound healing. In this work, we synthesized different nanocellulose-alginate hydrogels containing cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals (CNCTs), cellulose nanofibers or TEMPO-oxidized cellulose nanofibers (CNFTs). The hydrogels were freeze-dried and named as gels. The nanocelluloses and the gels were characterized by different techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA), while the biological features were characterized by cytotoxicity and cell growth assays. The addition of CNCTs or CNFTs in alginate gels contributed to the formation of porous structure (diameter of pores in the range between 40 and 150 μm). TEMPO-oxidized cellulose nanofibers have proven to play a crucial role in improving the dimensional stability of the samples when compared to the pure alginate gels, mainly after a thermal post-treatment of these gels containing 50 wt % of CNFT, which significantly increased the Ca²⁺ crosslinking density in the gel structure. The morphological characteristics, the mechanical properties, and the non-cytotoxic behavior of the CNFT-alginate gels improved bioadhesion, growth, and proliferation of the cells onto the gels. Thus, the alginate-nanocellulose gels might find applications in tissue engineering field, as for instance, in tissue repair or wound healing applications. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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18 pages, 2039 KiB

Open AccessArticle

Scaffolds for Chondrogenic Cells Cultivation Prepared from Bacterial Cellulose with Relaxed Fibers Structure Induced Genetically

by Paulina Jacek, Marcin Szustak, Katarzyna Kubiak, Edyta Gendaszewska-Darmach, Karolina Ludwicka and Stanisław Bielecki

Nanomaterials 2018, 8(12), 1066; https://doi.org/10.3390/nano8121066 - 17 Dec 2018

Cited by 21 | Viewed by 5228

Abstract

Development of three-dimensional scaffolds mimicking in vivo cells’ environment is an ongoing challenge for tissue engineering. Bacterial nano-cellulose (BNC) is a well-known biocompatible material with enormous water-holding capacity. However, a tight spatial organization of cellulose fibers limits cell ingrowth and restricts practical use [...] Read more.

Development of three-dimensional scaffolds mimicking in vivo cells’ environment is an ongoing challenge for tissue engineering. Bacterial nano-cellulose (BNC) is a well-known biocompatible material with enormous water-holding capacity. However, a tight spatial organization of cellulose fibers limits cell ingrowth and restricts practical use of BNC-based scaffolds. The aim of this study was to address this issue avoiding any chemical treatment of natural nanomaterial. Genetic modifications of Komagataeibacter hansenii ATCC 23769 strain along with structural and mechanical properties characterization of obtained BNC membranes were conducted. Furthermore, the membranes were evaluated as scaffolds in in vitro assays to verify cells viability and glycosaminoglycan synthesis by chondrogenic ATDC5 cells line as well as RBL-2H3 mast cells degranulation. K. hansenii mutants with increased cell lengths and motility were shown to produce BNC membranes with increased pore sizes. Novel, BNC membranes with relaxed fiber structure revealed superior properties as scaffolds when compared to membranes produced by a wild-type strain. Obtained results confirm that a genetic modification of productive bacterial strain is a plausible way of adjustment of bacterial cellulose properties for tissue engineering applications without the employment of any chemical modifications. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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11 pages, 3817 KiB

Open AccessArticle

Electrically-Conductive Sub-Micron Carbon Particles from Lignin: Elucidation of Nanostructure and Use as Filler in Cellulose Nanopapers

by Janea Köhnke, Harald Rennhofer, Christoph Unterweger, Notburga Gierlinger, Jozef Keckes, Cordt Zollfrank, Orlando J. Rojas and Wolfgang Gindl-Altmutter

Nanomaterials 2018, 8(12), 1055; https://doi.org/10.3390/nano8121055 - 15 Dec 2018

Cited by 8 | Viewed by 4444

Abstract

Carbon particles were produced from kraft lignin through carbonization of perfectly spherical, sub-micron beads obtained by aerosol flow. The structure of the resulting carbon particles was elucidated and compared to that derived from commercially available technical lignin powder, which is undefined in geometry. [...] Read more.

Carbon particles were produced from kraft lignin through carbonization of perfectly spherical, sub-micron beads obtained by aerosol flow. The structure of the resulting carbon particles was elucidated and compared to that derived from commercially available technical lignin powder, which is undefined in geometry. In addition to the smaller diameters of the lignin beads (<1 µm) compared to those of the lignin powder (100 µm), the former displayed a slightly higher structural order as revealed by X-ray diffraction and Raman spectroscopy. With regard to potential application in composite structures, the sub-micron carbon beads were clearly advantageous as a filler of cellulose nanopapers, which displayed better mechanical performance but with limited electrical conductivity. Compression sensing was achieved for this nanocomposite system. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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21 pages, 4534 KiB

Open AccessArticle

Preparation and Characterization of Polyvinylpyrrolidone/Cellulose Nanocrystals Composites

by Marina Voronova, Natalia Rubleva, Nataliya Kochkina, Andrei Afineevskii, Anatoly Zakharov and Oleg Surov

Nanomaterials 2018, 8(12), 1011; https://doi.org/10.3390/nano8121011 - 5 Dec 2018

Cited by 72 | Viewed by 6331

Abstract

Composite films and aerogels of polyvinylpyrrolidone/cellulose nanocrystals (PVP/CNC) were prepared by solution casting and freeze-drying, respectively. Investigations into the PVP/CNC composite films and aerogels over a wide composition range were conducted. Thermal stability, morphology, and the resulting reinforcing effect on the PVP matrix [...] Read more.

Composite films and aerogels of polyvinylpyrrolidone/cellulose nanocrystals (PVP/CNC) were prepared by solution casting and freeze-drying, respectively. Investigations into the PVP/CNC composite films and aerogels over a wide composition range were conducted. Thermal stability, morphology, and the resulting reinforcing effect on the PVP matrix were explored. FTIR, TGA, DSC, X-ray diffraction, SEM, and tensile testing were used to examine the properties of the composites. It was revealed PVP-assisted CNC self-assembly that produces uniform CNC aggregates with a high aspect ratio (length/width). A possible model of the PVP-assisted CNC self-assembly has been considered. Dispersibility of the composite aerogels in water and some organic solvents was studied. It was shown that dispersing the composite aerogels in water resulted in stable colloidal suspensions. CNC particles size in the redispersed aqueous suspensions was near similar to the CNC particles size in never-dried CNC aqueous suspensions. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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11 pages, 1678 KiB

Open AccessArticle

Use of Cellulose Nanofibers as an Electrode Binder for Lithium Ion Battery Screen Printing on a Paper Separator

by Oussama El Baradai, Davide Beneventi, Fannie Alloin, Yann Bultel and Didier Chaussy

Nanomaterials 2018, 8(12), 982; https://doi.org/10.3390/nano8120982 - 27 Nov 2018

Cited by 23 | Viewed by 5353

Abstract

Water-based inks were formulated using cellulose nanofibers as a binder in order to directly front/reverse print lithium ion cells on a paper separator. Moreover, the high cohesion of electrodes as provided by cellulose nanofibers allowed for the embedding metallic current collectors in the [...] Read more.

Water-based inks were formulated using cellulose nanofibers as a binder in order to directly front/reverse print lithium ion cells on a paper separator. Moreover, the high cohesion of electrodes as provided by cellulose nanofibers allowed for the embedding metallic current collectors in the electrodes during the printing stage, in order to develop a one-step printing and assembling process. Positive and negative inks based on LiFePO₄, or graphite, respectively, and cellulose nanofibers, displayed rheological properties complying with a variety of printing processes, as well as with screen printing. Printed cells exhibited high electrical conductivity and adhesion between current collectors and inks, i.e., up to 64 ± 1 J/m². Electrochemical cycling tests at C/10 showed a reversible capacity during the first cycle of about 80 mAh/g, which slightly decayed upon cycling. Preliminary results and assembling strategies can be considered as promising, and they represent a quick solution for the manufacturing of lithium ion batteries. Work is in progress to improve these processing issues and the cycling performances of Li-ion cells. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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13 pages, 3250 KiB

Open AccessArticle

Microwave-Hydrothermal Rapid Synthesis of Cellulose/Ag Nanocomposites and Their Antibacterial Activity

by Lian-Hua Fu, Qing-Long Gao, Chao Qi, Ming-Guo Ma and Jun-Feng Li

Nanomaterials 2018, 8(12), 978; https://doi.org/10.3390/nano8120978 - 27 Nov 2018

Cited by 19 | Viewed by 4134

Abstract

Silver-based antimicrobial nanomaterials are considered as the most promising antibacterial agents owing to their outstanding antimicrobial efficacy and their relatively low toxicity to human beings. In this work, we report on a facile and environment-friendly microwave-hydrothermal method to prepare cellulose/Ag nanocomposites using hemicellulose [...] Read more.

Silver-based antimicrobial nanomaterials are considered as the most promising antibacterial agents owing to their outstanding antimicrobial efficacy and their relatively low toxicity to human beings. In this work, we report on a facile and environment-friendly microwave-hydrothermal method to prepare cellulose/Ag nanocomposites using hemicellulose as the reductant. The influences of the microwave-hydrothermal heating time and temperature, as well as the hemicellulose concentration on the formation of cellulose nanocomposites, were investigated in detail. Experimental results indicated that the hemicellulose was an effective reductant for silver ions, with higher temperature and longer heating time favoring the formation of silver with higher crystallinity and mass content in the nanocomposites. Moreover, the antimicrobial properties of the as-prepared cellulose/Ag nanocomposites were explored using Gram-positive S. aureus ATCC 6538 and Gram-negative E. coli HB 101 by both disc diffusion method and agar dilution method, and the nanocomposites showed excellent antibacterial activity. These results demonstrate that the as-prepared cellulose/Ag nanocomposites, as a kind of antibacterial material, are promising for applications in a wide range of biomedical fields. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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15 pages, 4990 KiB

Open AccessArticle

Study of The Reaction Mechanism to Produce Nanocellulose-Graft-Chitosan Polymer

by Jose Luis Sanchez-Salvador, Ana Balea, M. Concepcion Monte, Angeles Blanco and Carlos Negro

Nanomaterials 2018, 8(11), 883; https://doi.org/10.3390/nano8110883 - 30 Oct 2018

Cited by 22 | Viewed by 5299

Abstract

Cellulose and chitin are the most abundant polymeric materials in nature, capable of replacing conventional synthetic polymers. From them, cellulose nano/microfibers (CNFs/CMFs) and chitosan are obtained. Both polymers have been used separately in graft copolymerization but there are not many studies on the [...] Read more.

Cellulose and chitin are the most abundant polymeric materials in nature, capable of replacing conventional synthetic polymers. From them, cellulose nano/microfibers (CNFs/CMFs) and chitosan are obtained. Both polymers have been used separately in graft copolymerization but there are not many studies on the use of cellulose and chitosan together as copolymers and the reaction mechanism is unknown. In this work, the reaction mechanism to produce nano/microcellulose-graft-chitosan polymer has been studied. Recycled cellulose pulp was used, with and without a 2,2,6,6-tetramethylpiperidin-1-oxyl-radical (TEMPO)-mediated oxidation pretreatment, to produce CNFs and CMFs, respectively. For chitosan, a low-molecular weight product dissolved in an acetic acid solution was prepared. Grafted polymers were synthesized using a microwave digester. Results showed that TEMPO-mediated oxidation as the cellulose pretreatment is a key factor to obtain the grafted polymer CNF-g-CH. A reaction mechanism has been proposed where the amino group of chitosan attacks the carboxylic group of oxidized cellulose, since non-oxidized CMFs do not achieve the desired grafting. ¹³C NMR spectra, elemental analysis and SEM images validated the proposed mechanism. Finally, CNF-g-CH was used as a promising material to remove water-based inks and dyes from wastewater. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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18 pages, 4065 KiB

Open AccessArticle

Enhancing the Stability of Aqueous Dispersions and Foams Comprising Cellulose Nanofibrils (CNF) with CaCO₃ Particles

by Tiia-Maria Tenhunen, Tiina Pöhler, Annaleena Kokko, Hannes Orelma, Michel Schenker, Patrick Gane and Tekla Tammelin

Nanomaterials 2018, 8(9), 651; https://doi.org/10.3390/nano8090651 - 23 Aug 2018

Cited by 21 | Viewed by 5527

Abstract

In this work, stability of dispersions and foams containing CaCO₃-based pigments and cellulose nanofibrils (CNF) was evaluated with the aim to reveal the mechanisms contributing to the overall stability of the selected systems. The utmost interest lies in the recently developed [...] Read more.

In this work, stability of dispersions and foams containing CaCO₃-based pigments and cellulose nanofibrils (CNF) was evaluated with the aim to reveal the mechanisms contributing to the overall stability of the selected systems. The utmost interest lies in the recently developed hydrocolloid hybrid CaCO₃ pigments and their potential to form bionanocomposite structures when incorporated with CNF. These pigments possess a polyelectrolyte layer deposited on the surface of the particle which is expected to enhance the compatibility between inorganic and organic components. Stability assessment of both dispersions and foams was conducted using turbidity profile scanning. In dispersions, CNF provides stability due to its ability to form a firm percolation network. If surface-modified pigments are introduced, the favourable surface interactions between the pigments and CNF positively influence the stability behaviour and even large macro-size pigments do not interfere with the stability of either dispersions or foams. In foams, the stability can be enhanced due to the synergistic actions brought by CNF and particles with suitable size, shape and wetting characteristics resulting in a condition where the stability mechanism is defined by the formation of a continuous plateau border incorporating a CNF network which is able to trap the inorganic particles uniformly. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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13 pages, 1232 KiB

Open AccessArticle

Towards Tunable Protein-Carrier Wound Dressings Based on Nanocellulose Hydrogels Crosslinked with Calcium Ions

by Alex Basu, Maria Strømme and Natalia Ferraz

Nanomaterials 2018, 8(7), 550; https://doi.org/10.3390/nano8070550 - 20 Jul 2018

Cited by 25 | Viewed by 4890

Abstract

A Ca²⁺-crosslinked wood-based nanofibrillated cellulose (NFC) hydrogel was investigated to build knowledge toward the use of nanocellulose for topical drug delivery applications in a chronic wound healing context. Proteins of varying size and isoelectric point were loaded into the hydrogel in [...] Read more.

A Ca²⁺-crosslinked wood-based nanofibrillated cellulose (NFC) hydrogel was investigated to build knowledge toward the use of nanocellulose for topical drug delivery applications in a chronic wound healing context. Proteins of varying size and isoelectric point were loaded into the hydrogel in a simple soaking procedure. The release of the proteins from the hydrogel was monitored and kinetics determining parameters of the release processes were assessed. The integrity of the hydrogel and proteins were also studied. The results showed that electrostatic interactions between the proteins and the negatively-charged NFC hydrogel structure played a central role in the loading process. The release of the proteins were governed by Fickian diffusion. An increased protein size, as well as a positive protein charge facilitated a slower and more sustained release process from the hydrogel matrix. At the same time, the positively-charged protein was shown to increase the post-loading hydrogel strength. Released proteins maintained structural stability and activity, thus indicating that the Ca²⁺-crosslinked NFC hydrogel could function as a carrier of therapeutic proteins without compromising protein function. It is foreseen that, by utilizing tunable charge properties of the NFC hydrogel, release profiles can be tailored to meet very specific treatment needs. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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14 pages, 32769 KiB

Open AccessArticle

Fabrication Flexible and Luminescent Nanofibrillated Cellulose Films with Modified SrAl₂O₄: Eu, Dy Phosphors via Nanoscale Silica and Aminosilane

by Longfei Zhang, Shaoyi Lyu, Zhilin Chen and Siqun Wang

Nanomaterials 2018, 8(5), 352; https://doi.org/10.3390/nano8050352 - 22 May 2018

Cited by 30 | Viewed by 5879

Abstract

Flexible 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose (ONFC) films with long afterglow luminescence containing modified SrAl₂O₄: Eu²⁺, Dy³⁺ (SAOED) phosphors were fabricated by a template method. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) trimethoxy-silane (APTMS) were employed cooperatively to [...] Read more.

Flexible 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose (ONFC) films with long afterglow luminescence containing modified SrAl₂O₄: Eu²⁺, Dy³⁺ (SAOED) phosphors were fabricated by a template method. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) trimethoxy-silane (APTMS) were employed cooperatively to improve the water resistance and compatibility of the SAOED particles in the ONFC suspension. The structure and morphology after modification evidenced the formation of a superior SiO₂ layer and coarse amino-compounds on the surface of the phosphors. Homogeneous dispersions containing ONFC and the modified phosphors were prepared and the interface of composite films containing the amino-modified particles showed a more closely packed structure and had less voids at the interface between the cellulose and luminescent particles than that of silica-modified phosphors. The emission spectra for luminescent films showed a slight blue shift (3.2 nm) at around 512 nm. Such flexible films with good luminescence, thermal resistance, and mechanical properties can find applications in fields like luminous flexible equipment, night indication, and portable logo or labels. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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Review

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39 pages, 2061 KiB

Open AccessReview

Versatile Application of Nanocellulose: From Industry to Skin Tissue Engineering and Wound Healing

by Lucie Bacakova, Julia Pajorova, Marketa Bacakova, Anne Skogberg, Pasi Kallio, Katerina Kolarova and Vaclav Svorcik

Nanomaterials 2019, 9(2), 164; https://doi.org/10.3390/nano9020164 - 29 Jan 2019

Cited by 264 | Viewed by 17418

Abstract

Nanocellulose is cellulose in the form of nanostructures, i.e., features not exceeding 100 nm at least in one dimension. These nanostructures include nanofibrils, found in bacterial cellulose; nanofibers, present particularly in electrospun matrices; and nanowhiskers, nanocrystals, nanorods, and nanoballs. These structures can be [...] Read more.

Nanocellulose is cellulose in the form of nanostructures, i.e., features not exceeding 100 nm at least in one dimension. These nanostructures include nanofibrils, found in bacterial cellulose; nanofibers, present particularly in electrospun matrices; and nanowhiskers, nanocrystals, nanorods, and nanoballs. These structures can be further assembled into bigger two-dimensional (2D) and three-dimensional (3D) nano-, micro-, and macro-structures, such as nanoplatelets, membranes, films, microparticles, and porous macroscopic matrices. There are four main sources of nanocellulose: bacteria (Gluconacetobacter), plants (trees, shrubs, herbs), algae (Cladophora), and animals (Tunicata). Nanocellulose has emerged for a wide range of industrial, technology, and biomedical applications, namely for adsorption, ultrafiltration, packaging, conservation of historical artifacts, thermal insulation and fire retardation, energy extraction and storage, acoustics, sensorics, controlled drug delivery, and particularly for tissue engineering. Nanocellulose is promising for use in scaffolds for engineering of blood vessels, neural tissue, bone, cartilage, liver, adipose tissue, urethra and dura mater, for repairing connective tissue and congenital heart defects, and for constructing contact lenses and protective barriers. This review is focused on applications of nanocellulose in skin tissue engineering and wound healing as a scaffold for cell growth, for delivering cells into wounds, and as a material for advanced wound dressings coupled with drug delivery, transparency and sensorics. Potential cytotoxicity and immunogenicity of nanocellulose are also discussed. Full article

(This article belongs to the Special Issue Cellulose Nanomaterials)

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