Cellulose nanocrystals/ZnO as a bifunctional reinforcing nanocomposite for poly(vinyl alcohol)/chitosan blend films: fabrication, characterization and properties

Tunable Construction of Chiral Nematic Cellulose Nanocrystals/ZnO Films for Ultra-Sensitive, Recyclable Sensing of Humidity and Ethanol

The investigation of functional materials derived from sustainable and eco-friendly bioresources has generated significant attention. Herein, nanocomposite films based on chiral nematic cellulose crystals (CNCs) were developed by incorporating xylose and biocompatible ZnO nanoparticles (NPs) via evaporation-induced self-assembly (EISA). The nanocomposite films exhibited iridescent color changes that corresponded to the birefringence phenomenon under polarized light, which was attributed to the formation of cholesteric structures. ZnO nanoparticles were proved to successfully adjust the helical pitches of the chiral arrangements of the CNCs, resulting in tunable optical light with shifted wavelength bands. Furthermore, the nanocomposite films showed fast humidity and ethanol stimuli response properties, exhibiting the potential of stimuli sensors of the CNC-based sustainable materials.

Synthesis of carboxylated cellulose nanocrystal/ZnO nanohybrids using Oxytenanthera abyssinica cellulose and zinc nitrate hexahydrate for radical scavenging, photocatalytic, and antibacterial activities

The extremely low antioxidant, photocatalytic, and antibacterial properties of cellulose limit its application in the biomedical and environmental sectors. To improve these properties, nanohybrides were prepared by mixing carboxylated cellulose nanocrystals (CCNCs) and zinc nitrate hexahydrate. Data from FTIR, XRD, DLS, and SEM spectra showed that, ZnO nanoparticles, with a size ranging from 94 to 351 nm and the smallest nanoparticle size of 164.18 nm, were loaded onto CCNCs. CCNCs/ZnO1 nanohybrids demonstrated superior antibacterial, photocatalytic, and antioxidant performance. More considerable antibacterial activity was shown with a zone of inhibition ranging from 26.00 ± 1.00 to 40.33 ± 2.08 mm and from 31.66 ± 3.51 to 41.33 ± 1.15 mm against Gram-positive and Gram-negative bacteria, respectively. Regarding photodegradation properties, the maximum value (∼91.52 %) of photocatalytic methylene blue degradation was observed after 75 min exposure to a UV lamp. At a concentration of 125.00 μm/ml of the CCNC/ZnO1 nanohybrids sample, 53.15 ± 1.03 % DPPH scavenging activity was obtained with an IC50 value of 117.66 μm/ml. A facile, cost-effective, one-step synthesis technique was applied to fabricate CCNCs/ZnO nanohybrids at mild temperature using Oxytenanthera abyssinica carboxylated cellulose nanocrystals as biotemplate. The result showed that CCNCs/ZnO nanohybrids possess potential applications in developing advanced functional materials for dye removal and antibacterial and antioxidant applications.

Strong double networked hybrid cellulosic foam for passive cooling

Up to now, energy conservation, emission reduction, and environmental protection are still the goals that humanity continuously pursues. Passive radiative cooling is a zero-consumption cooling technology, which gains more and more attention. However, the contraction between mechanical strength and cooling performance of traditional radiative cooling materials still limits their scalable production. In this work, we developed a strong double-networked hybrid cellulosic foam via crosslinking recyclable CNF and PVA with a silane coupling agent in the freeze-drying process. Meanwhile, nano zinc oxide and MOF were added to improve the mechanical and solar scattering of foam. Benefiting from the synergistic solar scattering of ZnO and MOF and the stable double crosslinking network, the as-prepared hybrid cellulosic foam exhibits high solar reflectivity of 0.965, high IR emissivity of 0.94, ultrahigh mechanical strength of and low thermal conductivity. Based on above results, the hybrid cellulosic foam shows high-performance daytime cooling efficiency of 7.5 °C under direct sunlight in the hot region (Nanjing, China), which can serve as outdoor thermal-regulation materials. This work demonstrates that biomass materials possess the enormous potential of in thermal regulating materials, and also provides great possibilities for their applications in energy conservation, environmental protection and green building materials.

Efficient photocatalytic remediation of lerui acid brilliant blue dye using radiation- prepared carboxymethyl cellulose/acrylic acid hydrogel supported by ZnO@Ag

Organic dye pollution from textiles and other industries presents a substantial risk to people and aquatic life. The use of photocatalysis to decolorize water using the strength of UV light is one of the most important remediation techniques. In the present study, a novel nanocomposites hydrogel including carboxymethyl cellulose (CMC), acrylic acid (AAc), Zinc oxide (ZnO), and silver (Ag) nanoparticles was produced using an eco-friendly γ-irradiation technique for photocatalytic decolorization applications. ZnO and Ag nanoparticles were distributed in the CMC/AAc hydrogel matrix without significant aggregation. SEM, XRD, EDX, TEM, and FTIR analyses were used to assess the physicochemical characteristics of the nanocomposite samples. Carboxymethyl cellulose/acrylic acid/Zinc oxide doped silver (CMC/PAAc/ZnO@Ag) nanocomposite hydrogels were developed and utilized in the photocatalytic decolorization of the lerui acid brilliant blue dye (LABB) when exposed to ultraviolet (UV) radiation. UV- Vis spectrophotometry was utilized to analyze the optical properties of the produced nanostructure. Regarding the decolorization of the LABB, the impacts of operational variables were investigated. The optimum conditions for decolorization (93 %) were an initial concentration of 50 mg/L, pH = 4, catalyst dosage of 50 g/L, and exposure time of 90 min. The results illustrated that the LABB acidic dye from wastewater was remarkably decolored.

Enhancement of Visible Light Antibacterial Activities of Cellulose Fibers from Lotus Petiole Decorated ZnO Nanoparticles

Cellulose/ZnO (CZ) nanocomposites are promising antimicrobial materials known for their antibiotic-free nature, biocompatibility, and environmental friendliness. In this study, cellulose fibers extracted from lotus petioles were utilized as a substrate and decorated with various shapes of ZnO nanoparticles (NPs), including small bean, hexagonal ingot-like, long cylindrical, and hexagonal cylinder-shaped NPs. Increasing zinc salt molar concentration resulted in highly crystalline ZnO NPs forming and enhanced interactions between ZnO NPs and -OH groups of cellulose. The thermal stability and UV-visible absorption properties of the CZ samples were influenced by ZnO concentration. Notably, at a ZnO molar ratio of 0.1, the CZ 0.1 sample demonstrated the lowest weight loss, while the optical band gap gradually decreased from 3.0 to 2.45 eV from the CZ 0.01 to CZ 1.0 samples. The CZ nanocomposites exhibited remarkable antibacterial activity against both Staphylococcus aureus (S. aureus, Gram-positive) and Escherichia coli (E. coli, Gram-negative) bacteria under visible light conditions, with a minimum inhibitory concentration (MIC) of 0.005 mg/mL for both bacterial strains. The bactericidal effects increased with higher concentrations of ZnO NPs, even achieving 100% inhibition. Incorporating ZnO NPs onto cellulose fibers derived from lotus plants presents a promising avenue for developing environmentally friendly materials with broad applications in antibacterial and environmental fields.

Manipulation of crystallization nucleation and thermal degradation of PLA films by multi-morphologies CNC-ZnO nanoparticles

Currently, the quest for more renewable and biodegradable materials is a scientific priority to address the problems of petroleum-based plastics are difficult to degrade. In this work, cellulose nanocrystals (CNC) have been used as a template and four morphologies of CNC-ZnO nanocomposites were prepared via a hydrothermal method, and CNC-ZnO/polylactic acid (PLA) composite films were obtained by solution casting. We find that CNC-ZnO nanocomposites as heterogeneous nucleating agents improved the crystallinity and the film with flower-like CNC-ZnO was improved by 2.4 %. Ea required for thermal degradation of the PLA films decreased to 66-81 % of that of neat PLA, calculated by the Kissinger method, the Friedman method, and the Flynn-Wall-Ozawa (FWO) method. The R2 model was the solid degradation mechanism of the PLA films, analyzed through the Coats-Redfern method and the Criado method. The H-bond content of the composite films was significantly reduced after thermal aging at 150 °C. We found that three-dimensional CNC-ZnO (ZnO-3) made more prominent contributions to the crystallization, thermal degradation, and thermal aging of PLA films than other dimensional. The thermal properties can be regulated by the dimension, size, and apparent morphology of CNC-ZnO nanoparticles.

Enhancement of the Structure, Thermal, Linear/Nonlinear Optical Properties, and Antibacterial Activity of Poly (vinyl alcohol)/Chitosan/ZnO Nanocomposites for Eco-Friendly Applications

The preparation of poly (vinyl alcohol)/chitosan/ZnO (PVA/Cs/ZnO) nanocomposite films as bioactive nanocomposites was implemented through an environmentally friendly approach that included mixing, solution pouring, and solvent evaporation. The nanocomposite films were characterized using various techniques such as X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and UV-Vis spectroscopy. The XRD study revealed the encapsulation of nanoparticles by the PVA/Cs blend matrix. The DSC results showed that the addition of ZnO NPs increased glass transition and melting temperature values of the PVA/Cs blend. ATR-FTIR spectra detected an irregular shift (either red or blue) in some of the characteristic bands of the PVA/Cs nanocomposite, indicating the existence of intra/intermolecular hydrogen bonding creating an interaction between the OH groups of PVA/Cs and ZnO nanoparticles. A thermogravimetric (TGA) analysis demonstrated that the nanocomposites achieved better thermal resistance than a pure PVA/Cs blend and its thermal stability was enhanced with increasing concentration of ZnO nanoparticles. UV analysis showed that with an increase in the content of ZnO NPs, the optical bandgap of PVA/Cs was decreased from 4.43 eV to 3.55 eV and linear and nonlinear parameters were enhanced. Our optical results suggest the use of PVA/Cs/ZnO nanocomposite films for various optoelectronics applications. PVA/Cs/ZnO nanocomposites exhibited significant antibacterial activity against Gram-positive and Gram-negative bacteria. It was found that nanocomposite samples were more effective against Gram-positive compared to Gram-negative bacteria.

Antimicrobial Nano-Zinc Oxide Biocomposites for Wound Healing Applications: A Review

Chronic wounds are a major concern for global health, affecting millions of individuals worldwide. As their occurrence is correlated with age and age-related comorbidities, their incidence in the population is set to increase in the forthcoming years. This burden is further worsened by the rise of antimicrobial resistance (AMR), which causes wound infections that are increasingly hard to treat with current antibiotics. Antimicrobial bionanocomposites are an emerging class of materials that combine the biocompatibility and tissue-mimicking properties of biomacromolecules with the antimicrobial activity of metal or metal oxide nanoparticles. Among these nanostructured agents, zinc oxide (ZnO) is one of the most promising for its microbicidal effects and its anti-inflammatory properties, and as a source of essential zinc ions. This review analyses the most recent developments in the field of nano-ZnO–bionanocomposite (nZnO-BNC) materials—mainly in the form of films, but also hydrogel or electrospun bandages—from the different preparation techniques to their properties and antibacterial and wound-healing performances. The effect of nanostructured ZnO on the mechanical, water and gas barrier, swelling, optical, thermal, water affinity, and drug-release properties are examined and linked to the preparation methods. Antimicrobial assays over a wide range of bacterial strains are extensively surveyed, and wound-healing studies are finally considered to provide a comprehensive assessment framework. While early results are promising, a systematic and standardised testing procedure for the comparison of antibacterial properties is still lacking, partly because of a not-yet fully understood antimicrobial mechanism. This work, therefore, allowed, on one hand, the determination of the best strategies for the design, engineering, and application of n-ZnO-BNC, and, on the other hand, the identification of the current challenges and opportunities for future research.

Accelerating the granulation of anammox sludge in wastewater treatment with the drive of "micro-nuclei": A review

Anammox granule sludge (AnGS) has great potential in the field of wastewater nitrogen removal, but its development and promotion have been limited by the slow granulation speed and fragile operating stability. Based on the reviews about the AnGS formation mechanism in this paper, "micro-nuclei" was found to play an important role in the granulation of AnGS, and adding "micro-nuclei" directly into the reactor may be an efficient way to accelerate the formation of AnGS. Then, accelerating AnGS granulation with inert particles, multivalent positive ions, and broken granule sludge as "micro-nuclei" was summarized and discussed. Among inert particles, iron-based particles may be a more advantageous candidate for "micro-nuclei" due to their ability to provide attachment sites and release ferric/ferrous ions. The precipitations of multivalent positive ions are also a potential option for "micro-nuclei" that can be generated in-situ, but a suitable dosing strategy is necessary. About broken granular sludge, the broken active AnGS may have advantages in terms of anaerobic ammonium oxidation bacteria-affinity and granulation speed, while using inactive granular sludge as "micro-nuclei" can avoid interfering bacterial invasion and has a higher cost performance than broken active AnGS. In addition, possible research directions for accelerating the formation of AnGS by dosing "micro-nuclei" were highlighted. This paper is intended to provide a possible pathway for the rapid start-up of AnGS systems, and references for the optimization and promotion of the AnGS process.

Facile preparation of cellulose nanocrystals/ZnO hybrids using acidified ZnCl2 as cellulose hydrolytic media and ZnO precursor

Hybridization of nanocellulose with zinc oxide nanoparticles can improve the dispersibility of the zinc oxide and bring new functions to the bio-based products. In this study, cellulose nanocrystal/zinc oxide (CNC/ZnO) nanohybrids with reinforcing and antibacterial properties were prepared via a facile one-pot route. Microcrystalline cellulose (MCC) was first treated with acidified zinc chloride and hydrolyzed into CNCs, which then served as a stabilizing and supporting agent for the in-situ growth of ZnO nanoparticles during subsequent chemical precipitation. The acidified ZnCl₂ solution played a dual role, acting both as cellulose hydrolytic media and as ZnO precursor. By adjusting the pH of the zinc precursor solution (pH = 9-12), well-dispersed rod-like (length: 137.0-468.0 nm, width: 54.1-154.1 nm) and flower-like (average diameter: 179.6 nm) ZnO nanoparticles with hexagonal wurtzite structure were obtained. CNC/ZnO nanohybrids were incorporated into waterborne polyurethane (WPU) films. The Young's modulus and tensile strength of the nanocomposite films increased gradually from 154.8 to 509.0 MPa and from 16.5 to 29.9 MPa, respectively, with increasing CNC/ZnO nanofiller content up to 10 wt%. The 10 % CNC/ZnO composites showed inhibition rates to both E. coli and S. aureus above 88.8 %.

Preparation of Novel Composites of Polyvinyl Alcohol Containing Hesperidin Loaded ZnO Nanoparticles and Determination of Their Biological and Thermal Properties

Hesperidin (HSP) is considered to be the most effective antimicrobial agent against SARS-CoV2 virus. The HSP was loaded onto ZnO nanoparticles that were successfully incorporated, via the hydrothermal method, into polyvinyl alcohol (PVA) for use as food packaging material. The hydrothermal method enabled the bioactive ZnO-HSP to be homogeneously dispersed in the PVA, which significantly increased the thermal stability of the matrix, while decreasing the softening temperature. The water holding capacity and water solubility of the obtained nanocomposites was reduced compared to the PVA. Finally, the ZnO-HSP antimicrobial agent contributed important antibacterial properties to the PVA and increased its antioxidant capacity against Staphylococcus aureus and Escherichia coli pathogens. In addition, the nanocomposites had no cytotoxic/proliferative effects on cancer cells. All results showed promise that the PVA/ZnO-HSP nanocomposites would be an excellent alternative for food packaging applications.

Construction of a Chitosan/ZnO-Based Light-Resistant Coating System to Protect Dyed Wood from Ultraviolet Irradiation via Layer-by-Layer Self-Assembly

Wood dyeing is an effective way to alleviate the supply-demand imbalance of valuable wood and improve the surface decoration of fast-growing wood. However, applications of dyed wood are limited due to the susceptibility of dyes and wood to photo-discolor and degrade under light irradiation. Thus, the improved weather resistance of dyed wood is crucial. To prevent photochromic discoloration of dyed wood, an anti-photochromic coating structure was constructed via layer-by-layer self-assembly (LbL) using chitosan and zinc oxide (ZnO). The results showed that the surface color difference of treated dyed wood was reduced by approximately 84.6% after the first 2 h of irradiation under the following conditions °C: temperature (50 °C), relative humidity (55%), and irradiation intensity (550 W/m²). However, the color of untreated dyed wood drastically changed at this stage. The reason for the decrease was that the redness and yellowness of treated dye wood were significantly reduced. The deposition of ZnO onto treated dyed wood helped to protect the wood from UV light irradiation. Chitosan bridged the dyes and complexed ZnO to enhance UV resistance. This study provides valuable information for the protection of dyed wood against light discoloration that can be used as an interior and exterior decorative material.

Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review

Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles' characteristics and the membrane's composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.

Antimicrobial, antioxidant, and pH-sensitive polyvinyl alcohol/chitosan-based composite films with aronia extract, cellulose nanocrystals, and grapefruit seed extract

Aronia or black chokeberry (Aronia melanocarpa), cellulose nanocrystals (CNCs), and grapefruit seed extract (GSE) were used for the preparation of multifunctional polyvinyl alcohol/chitosan (PVA/CS) composite films with pH-sensitivity, antimicrobial, antioxidant, and UV-barrier properties. Aronia extract showed total phenolic content of 297 ± 0.5 μg GAE/mg aronia extract, potent antioxidant activity, and high color-response efficiency. Isolated CNCs showed a needle-like structure with a length of 470 nm and a width of 35 nm. The tensile strength of the PVA/CS composite film increased by 74% after the incorporation of CNCs, whereas the film flexibility was enhanced by 75% after adding GSE. The PVA/CS-A (aronia extract) composite film showed a significant color change at different pHs and potent antioxidant activity. At the same time, the PVA/CS-G (GSE) showed the highest antimicrobial activity against Escherichia coli (Gram-negative) and Listeria monocytogenes (Gram-positive) bacteria. The PVA/CS-CGA composite film, reinforced with CNCs/GSE/Aronia extract, showed the highest UV-barrier (95.5%), highest antioxidant activity (95%), potent antimicrobial activity, pH-sensitivity, lowest water vapor permeability (WVP), and desirable mechanical properties. The multifunctional properties of the produced composite films encourage their use as active and intelligent food packaging films to extend shelf life and monitor food quality.

Dye degradation, antibacterial and in-silico analysis of Mg/cellulose-doped ZnO nanoparticles

Various concentrations of Mg into fixed amount of cellulose nanocrystals (CNC)-doped ZnO were synthesized using facile chemical precipitation. The aim of present study is to remove dye degradation of methylene blue (MB) and bactericidal behavior with synthesized product. Phase constitution, functional group analysis, optical behavior, elemental composition, morphology and microstructure were examined using XRD, FTIR, UV-Vis spectrophotometer, EDS and HR-TEM. Highly efficient photocatalytic performance was observed in basic medium (98%) relative to neutral (65%), and acidic (83%) was observed upon Mg and CNC co-doping. Significant bactericidal activity of doped ZnO nanoparticles depicted inhibition zones for G -ve and +ve bacteria ranging (2.20 - 4.25 mm) and (5.80-7.25 mm) for E. coli and (1.05 - 2.75 mm) and (2.80 - 4.75 mm) for S. aureus at low and high doses, respectively. Overall, doped nanostructures showed significant (P < 0.05) bactericidal efficacy against G +ve relative to G -ve. Furthermore, the molecular docking studies were employed to rationalize possible mechanism behind these in vitro bactericidal activities. In silico findings suggested CNC doped ZnO nanocomposites as possible inhibitors of β-lactamase (Binding score: -7.936 kcal/mol), DHFR (Binding score: -5.691 kcal/mol) and FabI (Binding score: -8.673 kcal/mol).

Role of Hybrid Nano-Zinc Oxide and Cellulose Nanocrystals on the Mechanical, Thermal, and Flammability Properties of Poly (Lactic Acid) Polymer

Biopolymers with universal accessibility and inherent biodegradability can offer an appealing sustainable platform to supersede petroleum-based polymers. In this research, a hybrid system derived from cellulose nanocrystals (CNCs) and zinc oxide (ZnO) nanoparticles was added into poly (lactic acid) (PLA) to improve its mechanical, thermal, and flame resistance properties. The ZnO-overlaid CNCs were prepared via the solvent casting method and added to PLA through the melt-blending extrusion process. The composite properties were evaluated using SEM, a dynamic mechanical analyzer (DMA), FTIR TGA, and horizontal burning tests. The results demonstrated that the incorporation of 1.5% nano-CNC-overlaid ZnO nanoparticles into PLA enhanced the mechanical and thermal characteristics and the flame resistance of the PLA matrix. Oxidative combustion of CNC-ZnO promoted char formation and flame reduction. The shielding effect from the ZnO-CNC blend served as an insulator and resulted in noncontinuous burning, which increased the fire retardancy of nanocomposites. By contrast, the addition of ZnO into PLA accelerated the polymer degradation at higher temperature and shifted the maximum degradation to lower temperature in comparison with pure PLA. For PLA composites reinforced by ZnO, the storage modulus decreased with ZnO content possibly due to the scissoring effect of ZnO in the PLA matrix, which resulted in lower molecular weight.

Cellulose from sources to nanocellulose and an overview of synthesis and properties of nanocellulose/zinc oxide nanocomposite materials

Recently, environmental and ecological concerns are increasing due to the usage of petroleum-based products so the synthesis of ultra-fine chemicals and functional materials from natural resources is drawing a tremendous level of attention. Nanocellulose, a unique and promising natural material extracted from native cellulose, may prove to be most ecofriendly materials that are technically and economically feasible in modern times, minimizing the pollution generation. Nanocellulose has gained tremendous attention for its use in various applications, due to its excellent special surface chemistry, physical properties, and remarkable biological properties (biodegradability, biocompatibility, and non-toxicity). Various types of nanocellulose, viz. cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC), are deeply introduced and compared in this work in terms of sources, production, structures and properties. The metal and metal oxides especially zinc oxide nanoparticles (ZnO-NPs) are broadly used in various fields due to the diversity of functional properties such as antimicrobial and ultraviolet (UV) properties. Thus, the advancement of nanocellulose and zinc oxide nanoparticles (ZnO-NPs)-based composites materials are summarized in this article in terms of the preparation methods and remarkable properties with the help of recent knowledge and significant findings (especially from the past six years reports). The nanocellulose materials complement zinc oxide nanoparticles, where they impart their functional properties to the nanoparticle composites. As a result hybrid nanocomposite containing nanocellulose/zinc oxide composite has shown excellent mechanical, UV barrier, and antibacterial properties. The nanocellulose based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics. Thus the functional composite materials containing nanocellulose and zinc oxide will determine the potential biomedical application for nanocellulose.

Multifunctional nanocellulose/metal and metal oxide nanoparticle hybrid nanomaterials

Nanocellulose materials are derived from cellulose, the most abundant biopolymer on the earth. Nanocellulose have been extensively used in the field of food packaging materials, wastewater treatment, drug delivery, tissue engineering, hydrogels, aerogels, sensors, pharmaceuticals, and electronic sectors due to their unique chemical structure and excellent mechanical properties. On the other hand, metal and metal oxide nanoparticles (NP) such as Ag NP, ZnO NP, CuO NP, and Fe₃O₄ NP have a variety of functional properties such as UV-barrier, antimicrobial, and magnetic properties. Recently, nanocelluloses materials have been used as a green template for producing metal or metal oxide nanoparticles. As a result, multifunctional nanocellulose/metal or metal oxide hybrid nanomaterials with high antibacterial properties, ultraviolet barrier properties, and mechanical properties were prepared. This review emphasized recent information on the synthesis, properties, and potential applications of multifunctional nanocellulose-based hybrid nanomaterials with metal or metal oxides such as Ag NP, ZnO NP, CuO NP, and Fe₃O₄ NP. The nanocellulose-based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics.

Applications of cellulose and chitin/chitosan derivatives and composites as antibacterial materials: current state and perspectives

The bacterial infections have always a serious problem to public health. Scientists are developing new antibacterial materials to overcome this problem. Polysaccharides are promising biopolymers due to their diverse biological functions, low toxicity, and high biodegradability. Chitin and chitosan have antibacterial properties due to their cationic nature, while cellulose/bacterial cellulose does not possess any antibacterial activity. Moreover, the insolubility of chitin in common solvents, the poor solubility of chitosan in water, and the low mechanical properties of chitosan have restricted their biomedical applications. In order to solve these problems, chemical modifications such as quaternization, carboxymethylation, cationization, or surface modification of these polymers with different antimicrobial agents, including metal and metal oxide nanoparticles, are carried out to obtain new materials with improved physiochemical and biological properties. This mini review describes the recent progress in such derivatives and composites with potential antibacterial applications.

Current advancements in chitosan-based film production for food technology; A review

Chitosan is obtained from chitin, which could be considered to be the most abundant polymer after cellulose. Owing to these properties, chitosan alone or chitosan-based composite film production is attaining huge attention in terms of applications from researchers and industrialists coming from divergent fields. To enhance the biological (mainly antimicrobial and antioxidant) and physiological (mainly mechanical, thermal and barrier) attributes of the chitosan-based films, a vast medley of plant extracts and supporting polymers has been blended into chitosan films. Considering the up to date literature reports based on chitosan film production and applications, it can be stated that still, the research ratio is low in this field. Chitosan blend/composite films with specific properties (superhydrophobicity, excellent mechanical strength, acceptable barrier properties) can be produced only for specific applications in food technology. In the current review, we tried to summarize the advancements made in the last 5-7 years in the field of chitosan film technology for its application in the food industry.

Performance of silver, zinc, and iron nanoparticles-doped cotton filters against airborne E. coli to minimize bioaerosol exposure

To overcome limitations of existing air-cleaning filters in capturing and deactivating aerosolized microorganisms, this study was embarked to evaluate novel Ag, Zn, and Fe nanoparticle-doped cotton filters (AgCt, ZnCt, FeCt), as biocidal filters for bioaerosol attenuation. To evaluate the biocidal activity of the nanocomposite filters, the survival of lab-generated E. coli after collection on each filter material was compared to collection on an undoped cotton control filter and in a BioSampler. Relative humidity (RH) affected the survival of bacteria on the filters, and the optimal RH was found to be 50 ± 5%. The physical removal efficiency (PRE) determined by an optical particle counter was 99.9 ± 0.7% for ZnCt, 97.4 ± 1.2% for AgCt, and 97.3 ± 0.6% for FeCt, where the control showed only 77.4 ± 6.3% for particles > 500 nm. The doped filters showed 100% viable removal efficiency (VRE). Importantly, the VRE of the nanocomposite filters after four cycles remained nearly 99% and was greater than the cotton control filter at 76.6 ± 3.2%. Adding to its benefits, the AgCt filters had a lower pressure drop than the FeCt and ZnCt filters and the cotton control. The permeability for the cotton control filter was 3.38 × 10-11 m2 while that for the AgCt filter was slightly higher (3.64 × 10-11 m2) than the other filters as well. Overall, these results suggest that nanocomposite-doped filter media, particularly AgCt, can provide effective protection against airborne pathogens with a lower pressure drop, elevated collection efficiency, and better disinfection capability as compared to untreated cotton filters, which are all important features for practical biocidal applications. Graphical abstract.

The preparation and antibacterial activity of cellulose/ZnO composite: a review

The infectious diseases caused by various bacteria pose serious threat to human health. To solve this problem, antibacterial agents have been widely used in people’s daily life to deactivate or kill these bacteria. Among the antibacterial agents, ZnO is one of the most promising metal oxide antibacterial agents due to its non-toxic nature and safe properties. To expand its application, many composites of ZnO have been widely studied. Cellulose, as one of the most abundant biopolymers, has many merits like biodegradability, biocompatibility and low cost. Thus, many studies focus on synthesized cellulose/ZnO. The synthetic strategy includes both chemical and physical methods. Many of them have been shown that cellulose/ZnO composites have excellent antibacterial activity and are environment-friendly and have many applications for example food packing, antibacterial fibers and so on. This review mainly discusses the preparation methods of cellulose/ZnO and their effect on the morphology and properties.

ZnO nanoparticle-embedded silk fibroin–polyvinyl alcohol composite film: a potential dressing material for infected wounds

A highly effective composite film based on ZnO NPs, silk fibroin and PVA for an infected wound.

Cellulose nanocrystal (CNC)–inorganic hybrid systems: synthesis, properties and applications

Cellulose nanocrystal (CNC), a class of sustainable nanomaterial derived from forest and agro-biomass can serve as nature's storage for carbon dioxide.

Extraction of nanocellulose and in-situ casting of ZnO/cellulose nanocomposite with enhanced photocatalytic and antibacterial activity

Polymer hosted metallic nanostructures with diverse applications have become a prominent area of materials science, engineering and technology. In this study nanocellulose (NC) was synthesized from oil palm empty fruit bunches biomass via alkaline treatment and acid hydrolysis and characterized. The obtained NC was used as a host polymer for the synthesis of zinc oxide (ZnO) nanostructures through in-situ solution casting method. Alkaline treatment and acid hydrolysis increased the percentage crystalline index from 35.7% to 43.3% and 53.3% respectively. X-ray diffraction studies pointed to cellulose I, with a monoclinic structure. Zinc oxide/cellulose nanocomposite displayed more photocatalytic activity than pure ZnO nanostructures upon degradation of methylene blue, and also improved antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli.

Preparation and Characterization of Polyvinyl Alcohol-Chitosan Composite Films Reinforced with Cellulose Nanofiber

In this study microcrystalline cellulose (MCC) was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. The treated cellulose slurry was mechanically homogenized to form a transparent dispersion which consisted of individual cellulose nanofibers with uniform widths of 3–4 nm. Bio-nanocomposite films were then prepared from a polyvinyl alcohol (PVA)-chitosan (CS) polymeric blend with different TEMPO-oxidized cellulose nanofiber (TOCN) contents (0, 0.5, 1.0 and 1.5 wt %) via the solution casting method. The characterizations of pure PVA/CS and PVA/CS/TOCN films were performed in terms of field emission scanning electron microscopy (FESEM), tensile tests, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results from FESEM analysis justified that low loading levels of TOCNs were dispersed uniformly and homogeneously in the PVA-CS blend matrix. The tensile strength and thermal stability of the films were increased with the increased loading levels of TOCNs to a maximum level. The thermal study indicated a slight improvement of the thermal stability upon the reinforcement of TOCNs. As evidenced by the FTIR and XRD, PVA and CS were considered miscible and compatible owing to hydrogen bonding interaction. These analyses also revealed the good dispersion of TOCNs within the PVA/CS polymer matrix. The improved properties due to the reinforcement of TOCNs can be highly beneficial in numerous applications.

Editorial: biodegradable materials

This Special Issue “Biodegradable Materials” features research and review papers concerning recent advances on the development, synthesis, testing and characterisation of biomaterials. These biomaterials, derived from natural and renewable sources, offer a potential alternative to existing non-biodegradable materials with application to the food and biomedical industries amongst many others. In this Special Issue, the work is expanded to include the combined use of fillers that can enhance the properties of biomaterials prepared as films. The future application of these biomaterials could have an impact not only at the economic level, but also for the improvement of the environment.