Enhanced interfacial interaction between modified cellulose nanocrystals and epoxidized natural rubber via ultraviolet irradiation

Green and sustainable smart wooden system integrated with cellulose nanowhiskers-supported polyvinyl alcohol and anthocyanin biomolecules to monitor food freshness

Smart packaging materials have been used to protect human health from environmental hazards by sending real-time colorimetric signals for changes in the food packaging environment. However, the colorimetric material sensors use synthetic sensor dyes, which are toxic, expensive, non-biodegradable, and difficult to prepare. Herein, a simple strategy is presented for the development of an environmentally-friendly halochromic wood able to change color upon exposure to spoilage of food. A combination of anthocyanin (Ac)/aluminum (Al) mordant (Ac/Al) nanoparticles and cellulose nanowhiskers (CNW)-reinforced polyvinyl alcohol (PVA) was infiltrated into a delignified wood to produce a translucent wood with halochromic properties. CNW were employed as reinforcement agent to improve the mechanical performance of PVA. Additionally, CNW function as a dispersing agent to prevent agglomeration of Ac/Al nanoparticles. The diameters of CNW are in the range of 12-19 nm, whereas Ac/Al particles showed diameters of 9-22 nm. The smart wood changed color from purplish to colorless when exposed to food spoilage. A hypsochromic change from 539 nm to 370 nm was shown by the anthocyanin receptor when the spoilage level of food increased. This could be attributed to the pH-driven molecular switching of anthocyanin, leading to charge delocalization.

Effect of Modified and Unmodified Oak Bark (Quercus Cortex) on the Cross-Linking Process and Mechanical, Anti-Aging, and Hydrophobic Properties of Biocomposites Produced from Natural Rubber (NR)

The study explores the novel use of oak bark (Quercus cortex) as a bio-filler in elastomeric composites, aligning with the global trend of plant-based biocomposites. Both modified and unmodified oak bark were investigated for their impact on the physicochemical properties of natural rubber (NR) composites. The bio-filler modified with n-octadecyltrimethoxysilane exhibited enhanced dispersion and reduced aggregates in the elastomeric matrix. NR composites containing more than 20 phr of unmodified and modified oak bark demonstrated an increased degree of cross-linking (αc > 0.21). Mechanical properties were optimal at 10-15 phr of oak bark and the sample with modified bio-filler (10 phr) achieved the highest tensile strength (15.8 MPa). Silanization and the addition of the bio-filler increased the hardness of vulcanizates. The incorporation of oak bark improved aging resistance at least two-fold due to phenolic derivatives with antioxidant properties. Hydrophobicity decreased with added bark, but silanization reversed the trend, making samples with a high content of oak bark the most hydrophobic (contact angle: 129°). Overall, oak bark shows promise as an eco-friendly, anti-aging filler in elastomeric composites, with modification enhancing compatibility and hydrophobicity.

Preparation of UV-cured cellulose nanocrystal-filled epoxidized natural rubber and its application in a triboelectric nanogenerator

Cellulose nanocrystal (CNC) is an abundant biopolymer possessing high strength and biodegradability. In the present work, the extraction of CNCs from Napier grass stems was carried out. The CNCs were subsequently modified by maleic anhydride, called M-CNC, before being incorporated into the epoxidized natural rubber (ENR). The compounds were later cured by ultraviolet (UV) irradiation under various conditions. The obtained optimum condition was then used to fabricate the biocomposites filled with various CNC and M-CNC loadings for triboelectric nanogenerator (TENG) performance measurements. Output voltage and current increased continuously with increasing filler loading. Regardless of the filler type, an increase in filler loading enhanced TENG output. ENR/M-CNC exhibited a superior TENG output to ENR/CNC due to the greater electron transfer capability of the biocomposites, as proven by the reduction in the ionization potential (IP) value obtained from the quantum calculation. In this study, ENR/M-CNC5 exhibited the maximum output voltage (80.3 V), current (7.4 μA), and power density (1.32 W/m2) at a load resistance of 9 MΩ.

Characterization and Application in Natural Rubber of Leucaena Leaf and Its Extracted Products

Leucaena is a fast-growing tree in the legume family. Its leaf contains a significant amount of protein and is thus widely used as fodder for cattle. To broaden its application in the rubber field, the effects of Leucaena leaf powder and its extracted products on the cure characteristics and mechanical properties of natural rubber were investigated. The extraction of Leucaena leaf was carried out by using a proteolytic enzyme at 60 °C. The digested protein was separated from the residue by centrifugation. Both digested protein and residue were then dried and ground into powder, namely digested protein powder and residual powder, respectively, before being characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction, particle size determination, and protein analysis. After being added to natural rubber at 3 parts per hundred rubber, they significantly reduced both the scorch time and the optimum cure time of the rubber compounds, probably due to the presence of nitrogen-containing substances, without a significant sacrifice of the mechanical properties. For instance, the optimum cure time decreased by approximately 25.5, 35.4, and 54.9% for Leucaena leaf powder, residual powder, and digested protein powder, respectively. Thus, they can be used as green and sustainable fillers with a cure-activation effect in rubber compounding.

Nanoarhitectonics of Inorganic-Organic Silica-Benzil Composites: Synthesis, Nanocrystal Morphology and Micro-Raman Analysis

The synthesis of nanosized organic benzil (C6H5CO)2 crystals within the mesoporous SiO2 host matrix was investigated via X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and ab initio lattice dynamics analysis. Combining these methods, we have proved that the main structural properties of benzil nanocrystals embedded into SiO2 host membranes with pore diameters of 6.0, 7.8, 9.4, and 13.0 nm are preserved compared to a bulk benzil crystal. Space confinement has an insignificant impact on the lattice vibrational properties of benzil crystals implanted into the host matrices. The ab initio lattice dynamics calculation of the phonon spectrum in the Brillouin zone center shows the mechanical and dynamical stability of benzil lattice, revealing very low optical frequency of 11 cm-1 at point Γ.

Second harmonic generation on crystalline organic nanoclusters under extreme nanoconfinement in functionalized silica-benzil composites

We demonstrate a series of organic-inorganic nanocomposite materials combining the mesoporous silica (PS) and benzil (BZL) nanocrystals embedded into its nanochannels (6.0-13.0 nm in diameter) by capillary crystallization. One aims to design novel, efficient nonlinear optical composite materials in which inactive amorphous host PS-matrix provides a tubular scaffold structure, whereas nonlinear optical functionality results from specific properties of the deposited guest BZL-nanocrystals. A considerable contraction of the BZL melt during its crystallization inside the silica nanochannels results in a formation of the texture consisting of (221)- and (003)-oriented BZL nanoclusters (22 nm in length), separated by voids. Specificity of the textural morphology similarly to the spatial confinement significantly influences the nonlinear optical features of composite PS:BZL materials being explored in the second harmonic generation (SHG) experiment. The light polarization anisotropy of the SHG response appears to be considerably reduced at channel diameters larger than 7 nm apparently due to the multiple scattering and depolarization of the light on randomly distributed and crystallographically oriented BZL-nanoclusters. The normalized SHG response decreases nonlinearly by more than one order of magnitude as the channel diameter decreases from 13.0 to 6.0 nm and vanishes when spatial cylindrical confinement approaches the sizes of a few molecular layers suggesting that the embedded BZL clusters indeed are not uniformly crystalline but are characterized by more complex morphology consisting of a disordered SHG-inactive amorphous shell, covering the channel wall, and SHG-active crystalline core. Understanding and controlling of the textural morphology in inorganic-organic nanocrystalline composites as well as its relationships with nonlinear optical properties can lead to the development of novel efficient nonlinear optical materials for the light energy conversion with prospective optoelectronic and photonic applications.

Thiol-Surface-Engineered Cellulose Nanocrystals in Favor of Copper Ion Uptake

Cellulose, the most abundant natural polymer on earth, has recently gained attention for a large spectrum of applications. At a nanoscale, nanocelluloses (mainly involving cellulose nanocrystals or cellulose nanofibrils) possess many predominant features, such as highly thermal and mechanical stability, renewability, biodegradability and non-toxicity. More importantly, the surface modification of such nanocelluloses can be efficiently obtained based on the native surface hydroxyl groups, acting as metal ions chelators. Taking into account this fact, in the present work, the sequential process involving chemical hydrolysis of cellulose and autocatalytic esterification using thioglycolic acid was performed to obtain thiol-functionalized cellulose nanocrystals. The change in chemical compositions was attributed to thiol-functionalized groups and explored via the degree of substitution using a back titration method, X-ray powder diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis. Cellulose nanocrystals were spherical in shape and ca. 50 nm in diameter as observed via transmission electron microscopy. The adsorption behavior of such a nanomaterial toward divalent copper ions from an aqueous solution was also assessed via isotherm and kinetic studies, elucidating a chemisorption mechanism (ion exchange, metal chelation and electrostatic force) and processing its operational parameters. In contrast to an inactive configure of unmodified cellulose, the maximum adsorption capacity of thiol-functionalized cellulose nanocrystals toward divalent copper ions from an aqueous solution was 4.244 mg g^-1 at a pH of 5 and at room temperature.

Preparation and modification of nanocellulose and its application to heavy metal adsorption: A review

Heavy metals are a notable pollutant in aquatic ecosystems that results in many deadly diseases of the human body after enrichment through the food chain. As an environmentally friendly renewable resource, nanocellulose can be competitive with other materials at removing heavy metal ions due to its large specific surface area, high mechanical strength, biocompatibility and low cost. In this review, the research status of modified nanocellulose for heavy metal adsorbents is primarily reviewed. Two primary forms of nanocellulose are cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs). The preparation process of nanocellulose was derived from natural plants, and the preparation process included noncellulosic constituent removal and extraction of nanocellulose. Focusing on heavy metal adsorption, the modification of nanocellulose was explored in depth, including direct modification methods, surface grafting modification methods based on free radical polymerization and physical activation. The adsorption principles of nanocellulose-based adsorbents when removing heavy metals are analyzed in detail. This review may further facilitate the application of the modified nanocellulose in the field of heavy metal removal.

Fabrication of untreated and silane-treated carboxylated cellulose nanocrystals and their reinforcement in natural rubber biocomposites

In this study, cellulose nanocrystal (CNC) was extracted from Napier grass stems and subsequently functionalized to carboxylated cellulose nanocrystal (XCNC) by using an environmentally friendly method, namely, the KMnO₄/oxalic acid redox reaction. The XCNC was subsequently modified with triethoxyvinylsilane (TEVS), called VCNC, by using ultrasound irradiation. The characterization of the prepared XCNC and VCNC was performed. The needle-like shape of XCNC was observed with an average diameter and length of 11.5 and 156 nm, respectively. XCNC had a carboxyl content of about 1.21 mmol g^-1. The silane treatment showed no significant effects on the diameter and length of XCNC. When incorporated into natural rubber (NR), both XCNC and VCNC showed very high reinforcement, as evidenced by the substantial increases in modulus and hardness of the biocomposites, even at very low filler loadings. However, due to the high polarity of XCNC, tensile strength was not significantly improved with increasing XCNC loading up to 2 phr, above which it decreased rapidly due to the filler agglomeration. For VCNC, the silane treatment reduced hydrophilicity and improved compatibility with NR. The highly reactive vinyl group on the VCNC's surface also takes part in sulfur vulcanization, leading to the strong covalent linkages between rubber and VCNC. Consequently, VCNC showed better reinforcement than XCNC, as evidenced by the markedly higher tensile strength and modulus, when compared at an equal filler loading. This study demonstrates the achievement in the preparation of a highly reinforcing bio-filler (VCNC) for NR from Napier grass using an environmentally friendly method and followed by a quick and simple sonochemical method.

Nanocellulose: A Fundamental Material for Science and Technology Applications

Recently, considerable interest has been focused on developing greener and biodegradable materials due to growing environmental concerns. Owing to their low cost, biodegradability, and good mechanical properties, plant fibers have substituted synthetic fibers in the preparation of composites. However, the poor interfacial adhesion due to the hydrophilic nature and high-water absorption limits the use of plant fibers as a reinforcing agent in polymer matrices. The hydrophilic nature of the plant fibers can be overcome by chemical treatments. Cellulose the most abundant natural polymer obtained from sources such as plants, wood, and bacteria has gained wider attention these days. Different methods, such as mechanical, chemical, and chemical treatments in combination with mechanical treatments, have been adopted by researchers for the extraction of cellulose from plants, bacteria, algae, etc. Cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), and microcrystalline cellulose (MCC) have been extracted and used for different applications such as food packaging, water purification, drug delivery, and in composites. In this review, updated information on the methods of isolation of nanocellulose, classification, characterization, and application of nanocellulose has been highlighted. The characteristics and the current status of cellulose-based fiber-reinforced polymer composites in the industry have also been discussed in detail.

Power Output Enhancement of Natural Rubber Based Triboelectric Nanogenerator with Cellulose Nanofibers and Activated Carbon

The growing demand for energy and environmental concern are crucial driving forces for the development of green and sustainable energy. The triboelectric nanogenerator (TENG) has emerged as a promising solution for harvesting mechanical energy from the environment. In this research, a natural rubber (NR)-based TENG has been developed with an enhanced power output from the incorporation of cellulose nanofibers (CNF) and activated carbon (AC) nanoparticles. The highest voltage output of 137 V, a current of 12.1 µA, and power density of 2.74 W/m2 were achieved from the fabricated NR-CNF-AC TENG. This is attributed to the synergistic effect of the electron-donating properties of cellulose material and the large specific surface area of AC materials. The enhancement of TENG performance paves the way for the application of natural-based materials to convert mechanical energy into electricity, as a clean and sustainable energy source.