Bioactive Lyocell Fibers with Inherent Antibacterial, Antiviral and Antifungal Properties

Functional Lyocell fibers gain interest in garments and technical textiles, especially when equipped with inherently bioactive features. In this study, Lyocell fibers are modified with an ion exchange resin and subsequently loaded with copper (Cu) ions. The modified Lyocell process enables high amounts of the resin additive (>10%) through intensive dispersion and subsequently, high uptake of 2.7% Cu throughout the whole cross-section of the fiber. Fixation by Na2CO3 increases the washing and dyeing resistance considerably. Cu content after dyeing compared to the original fiber value amounts to approx. 65% for reactive, 75% for direct, and 77% for HT dyeing, respectively. Even after 50 household washes, a recovery of 43% for reactive, 47% for direct and 26% for HT dyeing is proved. XRD measurements reveal ionic bonding of Cu fixation inside the cellulose/ion exchange resin composite. A combination of the fixation process with a change in Cu valence state by glucose/NaOH leads to the formation of Cu2O crystallites, which is proved by XRD. Cu fiber shows a strong antibacterial effect against Staphylococcus aureus and Klebsiella pneumonia bacteria, even after 50 household washing cycles of both >5 log CFU. In nonwoven blends with a share of only 6% Cu fiber, a strong antimicrobial (CFU > log 5) and full antiviral effectiveness (>log 4) was received even after 50 washing cycles. Time-dependent measurements already show strong antiviral behavior after 30 s. Further, the fibers show an increased die off of the fungal isolate Candida auris with CFU log 4.4, and nonwovens made from 6% Cu fiber share a CFU log of 1.7. Findings of the study predestines the fiber for advanced textile processing and applications in areas with high germ loads.

Shrinkage and Cracking Properties of Cellulose Fiber-Concrete Composites for 3D Printing by Leveraging Internal Curing

Compared with conventional formwork casting materials, 3D printed concrete (3DPC) is characterized by large amounts of cementitious materials, a low aggregate-binder ratio, and a large water evaporation area, which make the printed materials and structures highly prone to plastic shrinkage and cracking. In this study, cellulose fibers were incorporated into concrete to improve its moisture distribution and increase its early-age strength. The effects of both dry and prewet cellulose fibers on properties of 3DPC were experimentally investigated. To ensure consistency in the amounts of dry fibers used, 0.5-2% dry cellulose fibers and 1-4% prewet cellulose fibers were adopted. The effects of the added cellulose fibers on printability, mechanical strength, shrinkage, and cracking performance of the 3DPC were experimentally studied. Particularly, a constraint method was developed to access the cracking behavior of 3DPC. Favorable shrinkage resistance was achieved, and the 120-day shrinkage decreased by 17.9% and 23.3% by addition of 2% dry fibers and 4% prewet fibers, respectively. Cracking was eliminated with addition of 4% prewet fibers, without influencing the printability and mechanical properties.

Applications of Xylan Derivatives to Improve the Functional Properties of Cellulose Foams for Noise Insulation

Cellulose-based foams present a high potential for noise insulation applications. These materials are bio-degradable, eco-friendly by both embedded components and manufacturing process, have low density and high porosity, and are able to provide good noise insulation characteristics compared with available petroleum-based foams currently used on a large scale. This paper presents the results of some investigations performed by the authors in order to improve the functional characteristics in terms of free surface wettability and structural integrity. Native xylan and xylan-based derivatives (in terms of acetylated and hydrophobized xylan) were taken into account for surface treatment of cellulose foams, suggesting that hemicelluloses represent by-products of pulp and paper industry, and xylan polysaccharides are the most abundant hemicelluloses type. The investigations were mainly conducted in order to evaluate the level to which surface treatments have affected the noise insulation properties of basic cellulose foams. The results indicate that surface treatments with xylan derivatives have slowly affected the soundproofing characteristics of foams, but these clearly have to be taken into account because of their high decrease in wettability level and improving structural integrity.

Characterization of Cellulose Fiber Derived from Hemp and Polyvinyl Alcohol-Based Composite Hydrogel as a Scaffold Material

Cellulose nanocrystals (CNCs) were successfully extracted and purified from hemp using an alkaline treatment and bleaching process and subsequently used in conjunction with polyvinyl alcohol to form a composite hydrogel. Cellulose nanocrystals (1-10% (w/v)) were integrated into polyvinyl alcohol, and sodium tetraborate (borax) was employed as a crosslinking agent. Due to the small number of cellulose nanocrystals, no significant peak change was observed in the FT-IR spectra compared to pristine polyvinyl alcohol. The porosity was created upon the removal of the water molecules, and the material was thermally stable up to 200 °C. With the presence of cellulose nanocrystals, the melting temperature was slightly shifted to a higher temperature, while the glass transition temperature remained practically unchanged. The swelling behavior was examined for 180 min in deionized water and PBS solution (pH 7.4) at 37 °C. The degree of swelling of the composite with cellulose nanocrystals was found to be higher than that of pristine PVA hydrogel. The cell viability (%) of the prepared hydrogel with different proportions of cellulose nanocrystals was higher than that of pristine PVA hydrogel. Based on the results, the prepared composite hydrogels from cellulose nanocrystals extracted from hemp and polyvinyl alcohol were revealed to be an excellent candidate for scaffold material for medical usage.

Cellulose Fibers-Based Porous Lightweight Foams for Noise Insulation

This paper examines effective and environmentally friendly materials intended for noise insulation and soundproofing applications, starting with materials that have gained significant attention within last years. Foam-formed materials based on cellulose fibers have emerged as a promising solution. The aim of this study was to obtain a set of foam-formed, porous, lightweight materials based on cellulose fibers from a resinous slurry pulp source, and to investigate the impact of surfactant percentage of the foam mixtures on their noise insulation characterisitcs. The basic foam-forming technique was used for sample assembly, with three percentages of sodium dodecyl sulphate (as anionic surfactant) related to fiber weight, and a standardised sound transmission loss tube procedure was used to evaluate noise insulation performance. Results were obtained as observations of internal structural configurations and material characteristics, and as measurements of sound absorption/reflection, sound transmission loss, and surface acoustic impedance. Based on the findings within this study, the conclusions highlight the strong potential of these cellulosic foams to replace widely used synthetic materials, at least into the area of practical noise insulation applications.

Comparative Study on the Stiffness of Poly(lactic acid) Reinforced with Untreated and Bleached Hemp Fibers

Composite materials containing natural reinforcement fibers, generally called biocomposites, have attracted the interest of both researchers and manufacturers, but the most environmentally advantageous combinations include a bio-based matrix, as well. With this in mind, a poly(lactic acid) (PLA) matrix was reinforced with natural fibers from hemp, both untreated strands (UHSs) and soda-bleached fibers (SBHFs). The preparation of the subsequent fully bio-sourced, discontinuously reinforced composites involved kinetic mixing, intensive single-screw extrusion, milling, and injection molding. Up to a fiber content of 30 wt%, the tensile modulus increased linearly with the volume fraction of the dispersed phase. Differences between SBHFs (up to 7.6 Gpa) and UHSs (up to 6.9 Gpa) were hardly significant (p = 0.1), but SBHF-reinforced composites displayed higher strain at failure. In any case, for the same fiber load (30 wt%), the Young's modulus of PLA/hemp biocomposites was greater than that of glass fiber (GF)-reinforced polypropylene (5.7 GPa), albeit lower than that of PLA/GF (9.8 GPa). Considering all the measurements, the contribution of each phase was analyzed by applying the Hirsch model and the Tsai-Pagano model. As a concluding remark, although the intrinsic tensile modulus of SBHFs was lower than that of GF, the efficiency of those natural fibers as reinforcement (according to the rule of mixtures) was found to be higher.

Influence of Short Carbon Fibers on the Properties of Autoclaved Fiber Cement in Standard Fire Environment

In case of a fire, the flame can spread from the building through the outer openings to the outside. In such cases, the fire temperature thermal effect determines the façade fibrocement tile thermal destruction, while the flammable thermo-insulating systems used for building energy effectiveness ensures it sets on fire. The spread of such a fire becomes uncontrollable and raises an immediate danger to the people inside the building, while such event dynamics delay and make it harder to put out the fire. Extra additive usage in façade fibrocement tiles can raise its resistance to fire temperature effect. Carbon fiber is widely known as a material resistant to the high temperature destructive effect. An investigation was conducted on the influence that carbon fiber has on the properties of autoclaved fiber cement samples. The autoclaved fiber cement samples were made from the raw materials, typical for façade fiber cement plates, produced in an industrial way (using the same proportions). In the samples, carbon fiber was used instead of mix cellulose fiber in 0.5%, 0.75%, 1% proportions. After completing the density research, it was determined that the carbon fiber effect had no general effect on the sample density. Ultrasound speed spreading research showed that the carbon fiber insignificantly makes sample structure denser; however, after the fire temperature effect, sample structure is less dense when using carbon fiber. The results of both these investigations could be within the margin of error. Insignificant sample structure density rise was confirmed with water absorption research, which during the 1% carbon fiber usage case was lower by 4.3%. It was found that up to 1% carbon fiber usage instead of mix cellulose fiber creates a dense structure of autoclaved fiber cement samples, and the carbon fiber in the microstructure influences the mechanical properties of the autoclaved fiber cement samples. After using carbon fiber in ambient temperature, the sample compressive strength and bending strength increased. However, the results of mechanical properties were completely different after experiencing fire temperature effect. Scanning electron microscopy research showed that the bond between the carbon fiber and the cement matrix was not resistant to high temperature effect, due to which the structure of the samples with carbon fiber weakened. Research showed that carbon fiber lowers the mechanical properties of the autoclaved fiber cement samples after high temperature effect. After analyzing the density, ultrasound speed spreading, water absorption, microstructure and macrostructure, compressive strength, and bending strength, the authors determined the main CF usage for AFK dependencies: 1. CF usage up to 1% replacing MCF makes the AFK structure more dense up to 1.5%, and lowers the water absorption up to 4.3%; 2. CF incorporates itself densely into the AFC microstructure; 3. CF usage up to replacing MCF improves the AFK strength properties up to until the fire temperature effect. Compression strength increases up 7.3% while bending strength increases up to 14.9%. 4. AFK hydrate amount on CF surface is lower than on MCF; 5. Fire temperature effect on AFK with CF causes dehydration by removing water vapor from the microstructure, resulting in a lot of microcracks due to stress; 6. The CF and cement matrix contact zone is not resistant to fire temperature effect. SEM experiments were used to determine the CF "self-removing" effect; 7. Due to complex changes happening in the AFK during fire temperature effect, CF usage does not improve strength properties in the microstructure. Compression strength decreases to 66.7% while bending strength decreases to 20% when compared with E samples.

Flexible Substrate of Cellulose Fiber/Structured Plasmonic Silver Nanoparticles Applied for Label-Free SERS Detection of Malathion

Surface-enhanced Raman scattering (SERS) is considered an efficient technique providing high sensitivity and fingerprint specificity for the detection of pesticide residues. Recent developments in SERS-based detection aim to create flexible plasmonic substrates that meet the requirements for non-destructive analysis of contaminants on curved surfaces by simply wrapping or wiping. Herein, we reported a flexible SERS substrate based on cellulose fiber (CF) modified with silver nanostructures (AgNS). A silver film was fabricated on the membrane surface with an in situ silver mirror reaction leading to the formation of a AgNS-CF substrate. Then, the substrate was decorated through in situ synthesis of raspberry-like silver nanostructures (rAgNS). The SERS performance of the prepared substrate was tested using 4-mercaptobenzoic acid (4-MBA) as a Raman probe and compared with that of the CF-based plasmonic substrates. The sensitivity of the rAgNS/AgNS-CF substrate was evaluated by determining the detection limit of 4-MBA and an analytical enhancement factor, which were 10 nM and ~10⁷, respectively. Further, the proposed flexible rAgNS/AgNS-CF substrate was applied for SERS detection of malathion. The detection limit for malathion reached 0.15 mg/L, which meets the requirements about its maximum residue level in food. Thus, the characteristics of the rAgNS/AgNS-CF substrate demonstrate the potential of its application as a label-free and ready-to-use sensing platform for the SERS detection of trace hazardous substances.

Multifunctional Cellulosic Natural Rubber and Silver Nanoparticle Films with Superior Chemical Resistance and Antibacterial Properties

Composite films of natural rubber/cellulose fiber/silver nanoparticle were synthesized in a green route via the latex solution process. Hybrid cellulose filler containing carboxymethyl cellulose and cellulose microfibers was used to facilitate facile and fast preparation and to improve mechanical strength to the composites, respectively. All the composites possessed a high tensile strength of ~120 MPa, a high heat resistance of nearly 300 °C, and more than 20% biodegradability in soil in two weeks. Chemical resistance and antibacterial activity of the composite was enhanced depending on sizes and concentrations of silver nanoparticles (AgNPs). The composites containing 0.033-0.1% w/w AgNPs retarded toluene uptake to less than 12% throughout 8 h, whereas the composite containing 0.067-0.1% w/w AgNPs exhibited excellent antibacterial activities against Escherichia coli and Staphylococcus aureus. In comparison, 50 nm-AgNPs presented higher antibacterial activities than 100 nm-AgNPs. In vitro cytotoxicity test assessed after incubation for 24 h and 48 h revealed that almost all AgNPs-composite films exhibited non/weak and moderate cytotoxicity, respectively, to HaCaT keratinocyte cells.

Optimization of Cellulosic Fiber Extraction from Parsley Stalks and Utilization as Filler in Composite Biobased Films

Food waste is an abundant source of cellulose which can be extracted via mild alkali treatment. The extraction conditions of cellulose fibers can be optimized for reduced chemical and energy use and optimal functionality. This study focused on the optimization of alkali extraction of lignocellulosic fiber from parsley stalks by building an experimental design with the response surface method with alkali concentration (2, 6, and 10%, w/v), fiber:alkali ratio (0.02, 0.035, and 0.05; w/v) and extraction temperature (40, 70, and 100 °C) as independent variables, in order to evaluate the effects of extraction conditions on fiber yield and composition of parsley stalks extract (PSE). Following the optimization, PSE and untreated fibers (PF) were incorporated as filler into gum Arabic-sodium alginate-based films, and film properties such as water vapor permeability, optical and thermal properties, Fourier transform infrared spectra and surface morphology of the films were analyzed for evaluating the compatibility of these fillers with the composite film matrix. The optimal extraction conditions were determined as 2% alkali, sample:alkali ratio of 0.0276 and extraction temperature of 40 °C. PSE extracted at optimal conditions was added to the composite films, and water vapor permeability and optical properties were improved by up to 10% PSE compared to films with PF.

Biomimetic Robust Starch Composite Films with Super-Hydrophobicity and Vivid Structural Colors

The starch composite films (SCFs) will be one of the best alternative packaging materials to petroleum based plastic films, which mitigates white pollution and energy consumption. However, weak mechanical stability, water resistance, and dyeability has hindered the application of SCFs. Herein, a bioinspired robust SCFs with super-hydrophobicity and excellent structural colors were prepared by fiber-reinforcement and assembling SiO₂/Polydimethylsiloxane (PDMS) amorphous arrays on the surface of SCFs. The properties of the designed SCFs were investigated by various methods including scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), a tensile test, contact angle (CA) test, and an optical test. The results showed that the obtained SCFs possessed a higher tensile strength (55.17 MPa) attributed to the formed abundant hydrogen bonds between the molecular chains of the starch, cellulose fiber, and polyvinyl alcohol. Benefiting from the nanostructure with rough surface which were modified by materials with low surface free energy, the contact angle and sliding angle of the film reached up to 154° and 2°, respectively. The colors which were produced by the constructive interference of the coherent scattered light could cover all of the visible regions by tuning the diameters of the SiO₂ nanoparticles. The strategy in the present study not only reinforces the mechanical strength and water resistance of SCFs but also provides an environmentally friendly way to color the them, which shows unprecedented application potential in packaging materials of the starch composite films.

Durability of Cellulosic-Fiber-Reinforced Geopolymers: A Review

Geopolymers have high early strength, fast hardening speed and wide sources of raw materials, and have good durability properties such as high temperature resistance and corrosion resistance. On the other hand, there are abundant sources of plant or cellulose fibers, and it has the advantages of having a low cost, a light weight, strong adhesion and biodegradability. In this context, the geopolymer sector is considering cellulose fibers as a sustainable reinforcement for developing composites. Cellulosic-fiber-reinforced geopolymer composites have broad development prospects. This paper presents a review of the literature research on the durability of cellulosic-fiber-reinforced geopolymer composites in recent years. In this paper, the typical properties of cellulose fibers are summarized, and the polymerization mechanism of geopolymers is briefly discussed. The factors influencing the durability of cellulosic-fiber-reinforced geopolymer composites were summarized and analyzed, including the degradation of fibers in a geopolymer matrix, the toughness of fiber against matrix cracking, the acid resistance, and resistance to chloride ion penetration, high temperature resistance, etc. Finally, the influence of nanomaterials on the properties of geopolymer composites and the chemical modification of fibers are analyzed, and the research on cellulosic-fiber-reinforced geopolymer composites is summarized.

Methyl Orange-Doped Polypyrrole Promoting Growth of ZIF-8 on Cellulose Fiber with Tunable Tribopolarity for Triboelectric Nanogenerator

Cellulose fiber (CelF) is a biodegradable and renewable material with excellent performance but negligible triboelectric polarizability. Methods to enhance and rationally tune the triboelectric properties of CelF are needed to further its application for energy harvesting. In this work, methyl-orange-doped polypyrrole (MO-PPy) was in situ coated on CelF as a mediating layer to promote the growth of metal–organic framework ZIF-8 and to construct a cellulose-based triboelectric nanogenerator (TENG). The results showed that a small amount of MO-PPy generated in situ significantly promoted the growth of ZIF-8 on CelF, and the ZIF-8 deposition ratio was able to increase from 7.8% (ZIF-8/CelF) to 31.8% (ZIF-8/MO-PPy@CelF). ZIF-8/MO-PPy@CelF remained electrically conductive and became triboelectrically positive, and the triboelectricity’s positivity was improved with the increase in the ZIF-8 deposition ratio. The cellulose-based TENG constructed with ZIF-8/MO-PPy@CelF (31.8% ZIF-8 deposition ratio) and polytetrafluoroethylene (PTFE) could generate a transfer charge of 47.4 nC, open-circuit voltage of 129 V and short-circuit current of 6.8 μA—about 4 times higher than those of ZIF-8/CelF (7.8% ZIF-8 deposition ratio)—and had excellent cycling stability (open-circuit voltage remained almost constant after 10,000 cycles). MO-PPy not only greatly facilitated the growth of ZIF-8 on CelF, but also acted as an electrode active phase for TENG. The novel TENG based on ZIF-8/MO-PPy@CelF composite has cheerful prospects in many applications, such as self-powered supercapacitors, sensors and monitors, smart pianos, ping-pong tables, floor mats, etc.

A Facile Green Fabrication and Characterization of Cellulose-Silver Nanoparticle Composite Sheets for an Antimicrobial Food Packaging

The present study focused on a facile and green approach for the one-step synthesis of silver nanoparticles (AgNPs) embedded in hard wood bleached kraft fiber. The hydroxyl groups on the cellulose chain induced ionic silver reduction with additional hydrothermal energy, allowing for the in situ formation and deposition of AgNPs on the cellulose fiber. The white color of the bleached fiber transformed to yellow due to the formation of AgNPs. UV-Vis spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy revealed that the AgNPs were uniformly distributed across the surface of the obtained cellulose fibers. The results indicated that the formation and distribution of AgNPs on surface of cellulose fibers was significantly influenced by the amount and concentration of silver nitrate (AgNO3). The antimicrobial activity of the cellulose-AgNP composite sheet against Escherichia coli was found to be inhibiting. These findings imply that cellulose-AgNP composite sheets can be feasibly used as antimicrobial paper for food packaging.

De-Doped Polyaniline as a Mediating Layer Promoting In-Situ Growth of Metal-Organic Frameworks on Cellulose Fiber and Enhancing Adsorptive-Photocatalytic Removal of Ciprofloxacin

New kinds of inorganic–organic hybrid porous materials, metal–organic frameworks (MOFs), have shown great application potential in various fields, but their powdery nature limits their application to a certain extent. As a green and renewable biomass material in nature, cellulose fiber (CelF) has the advantages of biodegradability, recyclability and easy processing, and can be used as an excellent flexible substrate for MOFs. However, the efficient deposition of MOFs on CelF is still a great challenge for the development of this new material. Herein, polyaniline (PANI) and de-doped PANI (DPANI) with rich functional groups as a mediating layer was proposed to promote the in-situ growth and immobilization of some MOFs on CelF. The PANI (especially DPANI) layer greatly promoted the deposition of the four MOFs, and more encouragingly, significantly promoted the in-situ growth and nanocrystallization of MIL-100(Fe). MIL-100(Fe)@DPANI@CelF was selected as an adsorbent-photocatalyst to be used for the adsorptive-photocatalytic removal of ciprofloxacin (CIP) in water. The removal efficiency of CIP by MIL-100(Fe)@DPANI@CelF reached 82.78%, and the removal capacity of CIP was as high as 105.96 mg g⁻¹. The study found that DPANI had a synergistic effect on both the in-situ growth of MIL-100(Fe) on CelF and the adsorption-photocatalysis of CIP in water. The universal platform of PANI-mediated in-situ growth and immobilization of MOFs on CelF constructed in this study widens the road for the development of MOF@CelF composites.

Preparation of Breathable Cellulose Based Polymeric Membranes with Enhanced Water Resistance for the Building Industry

This study focuses on the development of advanced water-resistant bio-based membranes with enhanced vapour permeability for use within building envelopes. Building walls are vulnerable to moisture damage and mold growth due to water penetration, built-in moisture, and interstitial condensation. In this work, breathable composite membranes were prepared using micro-fibrillated cellulose fiber (CF) and polylactic acid (PLA). The chemical composition and physical structure of CF is responsible for its hydrophilic nature, which affects its compatibility with polymers and consequently its performance in the presence of excessive moisture conditions. To enhance the dispersibility of CF in the PLA polymer, the fibers were treated with an organic phosphoric acid ester-based surfactant. The hygroscopic properties of the PLA-CF composites were improved after surfactant treatment and the membranes were resistant to water yet permeable to vapor. Morphological examination of the surface showed better interfacial adhesion and enhanced dispersion of CF in the PLA matrix. Thermal analysis revealed that the surfactant treatment of CF enhanced the glass transition temperature and thermal stability of the composite samples. These bio-based membranes have immense potential as durable, eco-friendly, weather resistant barriers for the building industry as they can adapt to varying humidity conditions, thus allowing entrapped water vapor to pass through and escape the building, eventually prolonging the building life.

Superhydrophobic and Recyclable Cellulose-Fiber-Based Composites for High-Efficiency Passive Radiative Cooling

Passive daytime radiative cooling (PDRC) involves cooling down an object by simultaneously reflecting sunlight and thermally radiating heat to the cold outer space through the Earth's atmospheric window. However, for practical applications, current PDRC materials are facing unprecedented challenges such as complicated and expensive fabrication approaches and performance degradation arising from surface contamination. Herein, we develop scalable cellulose-fiber-based composites with excellent self-cleaning and self-cooling capabilities, through air-spraying ethanolic poly(tetrafluoroethylene) (PTFE) microparticle suspensions embedded partially within the microsized pores of the cellulose fiber to form a dual-layered structure with PTFE particles atop the paper. The formed superhydrophobic PTFE coating not only protects the cellulose-fiber-based paper from water wetting and dust contamination for real-life applications but also reinforces its solar reflectivity by sunlight backscattering. It results in a subambient cooling performance of 5 °C under a solar irradiance of 834 W/m² and a radiative cooling power of 104 W/m² under a solar intensity of 671 W/m². The self-cleaning surface of composites maintains their good cooling performance for outdoor applications, and the recyclability of the composites extends their life span after one life cycle. Additionally, dyed cellulose-fiber-based paper can absorb appropriate visible wavelengths to display specific colors and effectively reflect near-infrared lights to reduce solar heating, which synchronously achieves effective radiative cooling and esthetic varieties.

Customized Cellulose Fiber Paper Enabled by an In Situ Growth of Ultralong Hydroxyapatite Nanowires

Cellulose fiber (CF) paper is a low-cost, sustainable, and flexible substrate, which has gained increasing interest recently. Before practical usage, the functionalization of the pristine CF paper is indispensable to meet requirements of specific applications. Different from conventional surface modification or physical mixing methods, we report in situ growth of ultralong hydroxyapatite nanowires (HAPNWs) with lengths larger than 10 μm on the CF paper. HAPNWs are radially aligned on the surface of CFs, creating a micro/nanoscale hierarchical structure. By means of the excellent ion exchange ability of HAP and the hierarchical structure, the functions of the CF paper can be easily customized. As a proof-of-concept, we demonstrate two kinds of functional CF paper: (1) the photoluminescent CF paper by doping Eu³⁺ and Tb³⁺ ions into the crystal lattice of HAPNWs and (2) the superhydrophobic CF paper by coating poly(dimethylsiloxane) on the HAPNW hierarchical structure, which can be applied for self-cleaning and oil/water separation. It is expected that an in situ growth of ultralong HAPNWs will provide an instructive guideline for designing a CF paper with specific functions.

Coloration and Chromatic Sensing Behavior of Electrospun Cellulose Fibers with Curcumin

The effective approach for coloration and chromatic sensing of electrospun cellulose fabrics with a natural colorant, curcumin, is demonstrated. To achieve high surface area, the morphology of fiber was controlled to have rough and porous surface through an electrospinning of a cellulose acetate (CA) solution under optimized electrospinning parameters and solvent system. The resulting CA fibers were treated with a curcumin dye/NaOH ethanol solution, in which deacetylation of the CA fiber and high-quality coloration with curcumin were simultaneously achieved. As a control, a cotton fiber with similar diameter and smooth surface morphology was treated by the same method, resulting in poor coloration quality. The difference can be attributed to high surface area as well as trapping of dye molecules inside of cellulose fiber during deacetylation. Both fibers were further utilized for a chromatic sensing application for specific toxic gases. The incorporated curcumin dye responded to hydrogen chloride and ammonia gases reversibly via keto-enol tautomerism, and, as a consequence, the color was reversibly changed between reddish-brown and yellow colors. The cellulose fiber fabricated by the electrospinning showed ten times higher and two times quicker responsiveness compared to curcumin-colored cotton fiber sample prepared with the same immersion method.

Modulable properties of PVA/cellulose fiber composites

PURPOSE:

Development of PVA/cellulose fiber composite material with modulable properties, obtained through the increase of reinforcement and heat treatments in order to optimize the composite in terms of mechanical, thermal, and degradation properties.

METHODS:

The composite was designed selecting as matrix an experimental formulation based on water-soluble, biodegradable, polyvinyl alcohol (PVA) and microcrystalline cellulose (MCC), as reinforcement. Six different formulations, with increasing ratio of MCC content (from 0% to 55% w/w) in PVA, were developed and extruded by a co-rotating twin-screw extruder (TSA FSCM 21/40). Then, samples have been treated through two different thermal conditions (T1, T2) and characterized by scanning electron microscopy, tensile mechanical tests, thermogravimetric analysis, and water degradation tests to investigate, respectively, the influence of MCC ratios and heat treatment on morphological, mechanical, degradation, and thermal properties.

RESULTS:

The PVA/MCC composite exhibited a good stress-strain behavior as well as a close correlation between MCC content on tensile, thermal, and degradation properties. The second part of the results includes the analysis of the effects that the thermal treatments (T1, T2) had on the composite. In fact, thermal treatments have allowed improving the thermal and water stability as well as a significant improvement in the considered mechanical parameters due to a possible crosslinking of the PVA matrix.

CONCLUSION:

The present work shows how the properties of the PVA/MCC composite can become modular with the aim of extending its range of application as a new sustainable solution in the field of consumer products.

An Intelligent Film Based on Cassia Gum Containing Bromothymol Blue-Anchored Cellulose Fibers for Real-Time Detection of Meat Freshness

To prepare intelligent cellulose fiber (ICF), cellulose fibers were modified by grafting hydroxypropyltriethylamine groups to which bromothymol blue (BTB) was anchored. The ICFs were incorporated into cassia gum (CG) to prepare a pH-sensitive intelligent film. The Fourier transform infrared results indicated that BTB has been introduced in the CG-ICF5 film. Scanning electronic microscopy indicated that the addition of ICF can loosen the structure of the film. The incorporation of ICF decreased light transmittance and water vapor permeability but did not significantly affect thermal stability. The mechanical properties were weakened with 3% ICF addition and were improved with 5% ICF addition. The release experiment indicated that 46.784% and 8.297% of BTB was released from the CG-ICF5 film under oscillating to 50% and 95% alcohol/water solution, respectively. The response of the intelligent films to triethylamine in environments with different relative humidities was investigated. A visible color change occurred in the triethylamine environment within 20 min. Pork and chicken spoilage experiments were performed to study the application of the intelligent film in monitoring meat freshness during spoilage. Obvious color changes appeared, demonstrating that the intelligent film has potential for use in real-time indication of meat spoilage.

Multi-Layer Filters: Adsorption and Filtration Mechanisms for Improved Separation

Filters made of cellulose fiber and perlite particles were prepared using a wet laying papermaking technique. Polyamide-amine-epichlorohydrin (PAE) was added to provide wet strength. Filters were prepared at two different total basis weights of 200 and 400 grams per square meter (gsm). Single and multi-layered filters were structured for each total basis weights. The effect of total basis weights and multi-layered structure on methylene blue adsorption and silicon dioxide (SiO₂) particle filtration was investigated. Methylene blue adsorption was performed in two modes: constant pressure and constant flow rate. In both operation modes, the adsorption capacity of multi-layered filters was significantly higher (16–100%) than for single-layer filters at the same overall weight. The effect of layer separation was also characterized using polypropylene separators and tested under constant flow rate operation. Separators provided more effective methylene blue adsorption by generating a well-distributed flow. Filtration performance was quantified with 0.5 μm silicon dioxide particles under constant pressure conditions; this is to mimic bacteria rejection. Filtration capability of SiO₂ particles was reduced slightly (12%) with decreasing individual filter layer thickness regardless of the multi-layered structure. Filtering polyethylene glycol (PEG) molecules with two different molecular weights was performed; however, no rejection was recorded. The filter internal pore structure was visualized by 3D-X ray computed tomography and the void fraction was quantified. 400 gsm single layer presented areas of low fiber density forming pores, while the pore volume decreased for thinner filter layers.

In-Situ pH-Sensitive Fibers via the Anchoring of Bromothymol Blue on Cellulose Grafted with Hydroxypropyltriethylamine Groups via Adsorption

In-situ pH-sensitive cellulose fibers (IS-pH-SCF) were prepared by anchoring bromothymol blue (BTB) onto cellulose fibers (CF) modified with hydroxypropyltriethylamine (HPTTL) groups. Fourier transform infrared and X-ray photoelectron spectrum analyses demonstrated that the HPTTL groups were grafted onto the CF. X-ray diffraction proved that cellulose I in the CF transformed into cellulose II after quaternization. Scanning electron microscopy suggested that the quaternized CF (QCF) surface was clean and uniformly ridged. The adsorption of BTB onto QCF was carried out via batch adsorption experiments. A kinetic study illustrated that the adsorption was a spontaneous process and described well by pseudo-second-order, Freundlich and Temkin isotherms. The activation energy for the BTB adsorption onto QCF was 52.89 kJ/mol, which proved that the BTB adsorption onto QCFs was chemically controlled. The pH response demonstrated that the IS-pH-SCF was highly sensitive to pH, with an obvious color change for pH 4 to 8. The release tests showed that BTB was anchored on QCFs and that no BTB was released. IS-pH-SCF has a potential use for indicating pH changes in food.

Cellulose Fiber-Based Hierarchical Porous Bismuth Telluride for High-Performance Flexible and Tailorable Thermoelectrics

Porous modification is a general approach to endowing the rigid inorganic thermoelectric (TE) materials with considerable flexibility, however, by which the TE performances are severely sacrificed. Thus, there remains an ongoing struggle against the trade-off between TE properties and flexibility. Herein, we develop a novel strategy to combine Bi₂Te₃ thick film with ubiquitous cellulose fibers (CFs) via an unbalanced magnetron sputtering technique. Owing to the nano-micro hierarchical porous structures and the excellent resistance to crack propagation of the Bi₂Te₃/CF architectures, the obtained sample with a nominal Bi₂Te₃ deposition thickness of tens of micrometers exhibits excellent mechanically reliable flexibility, of which the bending deformation radius could be as small as a few millimeters. Furthermore, the Bi₂Te₃/CF with rational internal resistance and tailorable shapes and dimensions are successfully fabricated for practical use in TE devices. Enhanced Seebeck coefficients are observed in the Bi₂Te₃/CF as compared to the dense Bi₂Te₃ films, and the lattice thermal conductivity is remarkably reduced due to the strong phonon scattering effect. As a result, the TE figure of merit, ZT, is achieved as high as ∼0.38 at 473 K, which competes with the best flexible TEs and can be further improved by optimizing the carrier concentrations. We believe this developed technique not only opens up a new window to engineer flexible TE materials for practical applications but also promotes the robust development of the fields, such as paper-based flexible electronics and thin-film electronics.

Morphological, mechanical, barrier and properties of films based on acetylated starch and cellulose from barley

BACKGROUND

Biodegradable films of native or acetylated starches with different concentrations of cellulose fibers (0%, 10% and 20%) were prepared. The films were characterized by morphological, mechanical, barrier, and thermal properties.

RESULT

The tensile strength of the acetylated starch film was lower than those of the native starch film, without fibers. The addition of fibers increased the tensile strength and decreased the elongation and the moisture of native and acetylated starches films. The acetylated starch film showed higher water solubility when compared to native starch film. The addition of cellulose fibers reduced the water solubility of the acetylated starch film. The films reinforced with cellulose fiber exhibited a higher initial decomposition temperature and thermal stability.

CONCLUSION

The mechanical, barrier, solubility, and thermal properties are factors which direct the type of the film application in packaging for food products. The films elaborated with acetylated starches of low degree of substitution were not effective in a reduction of the water vapor permeability. The addition of the cellulose fiber in acetylated and native starches films can contribute to the development of more resistant films to be applied in food systems that need to maintain their integrity. © 2016 Society of Chemical Industry.

Managing Ammonia Emissions From Screwworm Larval Rearing Media

Mass production, sterilization, and release of screwworms (Cochliomyia hominivorax (Coquerel)) that were competitive in the field significantly contributed to the successful application of the sterile insect technique for eradication of screwworms from continental North America. Metabolic byproducts resulting from protein-rich diets required for larval screwworms lead to ammonia liberation, sometimes at high levels, within the mass rearing facility. Until recently a sodium polyacrylate gel bulking agent was used for the larval media and adsorbed much of the ammonia. A need to replace the gel with an environmentally "friendly" bulking agent, while not increasing ammonia levels in the rearing facility, led to a series of experiments with the objective of developing procedures to reduce ammonia emissions from the larval media bulked with cellulose fiber. Additives of ammonia-converting bacteria, potassium permanganate, and Yucca schidigera Roezl ex Otrgies powder extract, previously reported to reduce ammonia levels in organic environments, were evaluated. Ammonia-converting bacteria did not have a positive effect. Addition of Y. schidigera powder extract (∼1% of total volume), potassium permanganate (∼250 ppm), and a combination of these two additives (at these same concentrations) kept ammonia at equivalent levels as when larval media was bulked with gel. Potassium permanganate also had sufficient antimicrobial properties that the use of formaldehyde in the diet was not necessary. Further testing is needed, at a mass rearing level, before full implementation into the screwworm eradication program.

Linking cellulose fiber sediment methyl mercury levels to organic matter decay and major element composition

Methylation of mercury (Hg) to highly toxic methyl Hg (MeHg), a process known to occur when organic matter (OM) decomposition leads to anoxia, is considered a worldwide threat to aquatic ecosystems and human health. We measured temporal and spatial variations in sediment MeHg, total Hg (THg), and major elements in a freshwater lagoon in Sweden polluted with Hg-laden cellulose fibers. Fiber decomposition, confined to a narrow surface layer, resulted in loss of carbon (C), uptake of nitrogen (N), phosphorus (P), and sulfur (S), and increased MeHg levels. Notably, fiber decomposition and subsequent erosion of fiber residues will cause buried contaminants to gradually come closer to the sediment-water interface. At an adjacent site where decomposed fiber accumulated, there was a gain in C and a loss of S when MeHg increased. As evidenced by correlation patterns and vertical chemical profiles, reduced S may have fueled C-fixation and Hg methylation at this site.

Solid phase extraction for the speciation and preconcentration of inorganic selenium in water samples: a review

Selenium is an essential element for the normal cellular function of living organisms. However, selenium is toxic at concentrations of only three to five times higher than the essential concentration. The inorganic forms (mainly selenite and selenate) present in environmental water generally exhibit higher toxicity (up to 40 times) than organic forms. Therefore, the determination of low levels of different inorganic selenium species in water is an analytical challenge. Solid-phase extraction has been used as a separation and/or preconcentration technique prior to the determination of selenium species due to the need for accurate measurements for Se species in water at extremely low levels. The present paper provides a critical review of the published methods for inorganic selenium speciation in water samples using solid phase extraction as a preconcentration procedure. On the basis of more than 75 references, the different speciation strategies used for this task have been highlighted and classified. The solid-phase extraction sorbents and the performance and analytical characteristics of the developed methods for Se speciation are also discussed.

3D-QSPR method of computational technique applied on red reactive dyes by using CoMFA strategy

Cellulose fiber is a tremendous natural resource that has broad application in various productions including the textile industry. The dyes, which are commonly used for cellulose printing, are "reactive dyes" because of their high wet fastness and brilliant colors. The interaction of various dyes with the cellulose fiber depends upon the physiochemical properties that are governed by specific features of the dye molecule. The binding pattern of the reactive dye with cellulose fiber is called the ligand-receptor concept. In the current study, the three dimensional quantitative structure property relationship (3D-QSPR) technique was applied to understand the red reactive dyes interactions with the cellulose by the Comparative Molecular Field Analysis (CoMFA) method. This method was successfully utilized to predict a reliable model. The predicted model gives satisfactory statistical results and in the light of these, it was further analyzed. Additionally, the graphical outcomes (contour maps) help us to understand the modification pattern and to correlate the structural changes with respect to the absorptivity. Furthermore, the final selected model has potential to assist in understanding the characteristics of the external test set. The study could be helpful to design new reactive dyes with better affinity and selectivity for the cellulose fiber.