Search Results (741)

Low-molecular-weight gelators (LMWGs) have attracted growing attention as versatile alternatives to conventional polymeric thickeners and gelators, owing to their ability to form three-dimensional fibrillar networks through non-covalent self-assembly and to undergo reversible sol–gel transitions in response to external stimuli. Among the various stimuli that can be exploited, pH represents a particularly attractive trigger given its direct relevance to biological and physiological environments. This review focuses on three categories of pH-responsive LMWGs that have shown notable progress over the past decade yet remain relatively underexplored in the literature. First, N-oxide-type hydrogelators are discussed, with emphasis on amide amine oxide-based surfactants and pyridine-N-oxide frameworks. The pH-dependent protonation of the N-oxide moiety modulates intermolecular hydrogen bonding, thereby governing self-assembly and gel formation. The structural versatility of these gelators enables rational tuning of aggregate morphology and confers clear pH and temperature responsiveness. Second, recent advances in phenylboronic acid-based LMWGs are highlighted. Although boronic acid derivatives have long been studied as dynamic crosslinking units in polymeric hydrogels, 3-isobutoxyphenylboronic acid was recently identified as the first example of phenylboronic acid functioning as an LMWG, in which gelation is driven primarily by hydrogen bonding and pH responsiveness is exploited for stimuli-triggered gel disruption rather than gel formation. Third, pH-responsive orthogonal self-assembly systems are reviewed. Representative examples include multicomponent hybrid hydrogels combining pH-activated LMWGs with polymer gelators for controlled drug release, pH-triggered self-sorting of two LMWGs without any polymeric component, and bio-based orthogonal hydrogels composed of a glucolipid LMWG and cellulose nanocrystals. For each system, both advantages and remaining limitations are critically assessed. Collectively, this review aims to provide a timely overview of emerging trends in pH-responsive LMWG research and to offer perspectives on the rational design of next-generation stimuli-responsive soft materials. Full article

In this study, a cellulose nanocrystal (CNC)-supported Ag–ZnO nanocomposite was synthesized via a hydrothermal route as a polymeric photocatalyst for efficient UV-A light-driven dye degradation. The renewable CNC framework provides abundant hydroxyl functional groups for nanoparticle anchoring, enhancing dispersion and interfacial charge transfer. Structural (XRD, FTIR, TEM, PL, and XPS) and thermal (TGA and DTG) analyses confirm successful incorporation of Ag nanoparticles and retention of CNC crystallinity. The composite exhibits a reduced optical bandgap (3.02 eV) and demonstrates superior photocatalytic activity, achieving 96% methylene blue (MB) degradation within 120 min. Enhanced performance is attributed to the synergistic effect of Ag-induced plasmonic excitation and CNC-facilitated charge migration, effectively suppressing ZnO photocorrosion. Moreover, the optimization of the parameters was conducted and found to be pH 7, a catalyst dose of 0.3 g L⁻¹, and an initial MB concentration of 10 ppm, which shows the best photocatalytic degradation reaction. The CNC/Ag–ZnO catalyst maintains 87% activity after five reuse cycles, showing good stability and reusability. The photostability of the CNC/Ag–ZnO catalyst was evaluated by ICP-MS, which measured Zn²⁺ concentration in the aqueous solution. Additionally, the degraded MB compounds were identified using GC-MS/MS analysis. This work highlights the potential of polymer-based biogenic supports for sustainable photocatalyst design and bridges polymer science with environmental remediation technology. Full article

Photodynamic therapy (PDT) has already gained immense attention in the anti-tumor field due to its low toxicity and non-invasiveness compared to traditional treatment methods. Therefore, the development of efficient photosensitizers is crucial for the advancement of photodynamic therapy. Although phthalocyanines (Pcs) have attracted huge attention as efficient photosensitizers, their clinical applications are hindered by poor solubility and a tendency to aggregate. Herein, two different Pcs that have different polarities were loaded into bacterial cellulose nanoparticles via non-covalent interactions. The aggregation behaviors and singlet oxygen production efficiencies were studied, as well as the influence of the Pc polarity on loading ratios. It was observed that octa-propylsulfonyl phthalocyanine ZnPc(SO₂Pr)₈, which has a more polar structure, loaded more on bacterial cellulose nanocrystal. Also, singlet oxygen generation efficiency of ZnPc(SO₂Pr)₈ was harmoniously increased with the loading ratio. The result indicated that both of the phthalocyanine/bacterial cellulose nanocrystal (Pc/BCNs) systems produced singlet oxygen and could be used as potential photosensitizers in PDT, especially ZnPc(SO₂Pr)_8, due to the high loading ratio. Full article

It is limited to use cellulose nanocrystals (CNCs) as green lubricant nanoadditives due to their high biodegradability. A promising solution is to convert CNCs into biocarbon. Herein, a multi-layer biocarbon (MLC) was prepared by carbonizing CNCs with an ionic liquids–thermal method. MLC was characterized comprehensively and then dispersed into rapeseed oil for use as a nanoadditive. The tribological performance of the MLC nanoadditive was evaluated using a ball-on-disc tribometer. The lubrication mechanism of the MLC nanoadditive was elucidated according to wear analysis of the worn surfaces and wear residues. It was found that MLC had a high carbon content of 77 at% and showed a two-dimensional multi-layered morphology. Each layer was composed of amorphous carbon nanosheets embedded with many crystalline carbon dots. The MLC nanoadditive was of excellent dispersibility and stability in rapeseed oil. Tribological experiments showed that the MLC nanoadditive, with a concentration of merely 0.04 wt%, led to a decrease in the frictional coefficient by 12.4% and the wear volume by 50.7%, having higher efficacy than the CNC nanoadditive. The exceptional lubrication effect of the MLC nanoadditive was mainly attributable to its interfacial deposition behavior and its subsequent fragmenting behavior. This work develops a novel method for biocarbon preparation and showcases its significant potential in lubrication applications. Full article

Expanded polystyrene (EPS) waste is a major environmental concern, yet practical routes to upgrade it into higher value-added materials remain limited. Here, post-consumer EPS was dissolved in ethyl acetate and solvent-cast into films containing cellulose nanocrystals (CNCs) and a sunflower oil. Three formulations were produced: F-EPS (100% EPS), F-EPS + CEL (80% EPS/20% CNC), and F-EPS + CEL + OIL (80% EPS/15% CNC/5% oil). CNC markedly enhanced optical shielding, reducing transmittance at 400 nm from ≈58% (F-EPS) to ≈18% (CNC containing films). All films remained hydrophobic, showed negligible water uptake, and exhibited low mass loss after 30 days of accelerated weathering ($\Delta M=1$–$3\%$). Tensile testing showed that F-EPS had the highest UTS and elongation at break (10.0 ± 0.6 MPa and 10.5 ± 0.4%), whereas adding cellulose increased the elastic modulus (249.5 ± 29.0 MPa to 358.4 ± 64.8 MPa) but reduced UTS and elongation (8.2 ± 0.2 MPa and 5.4 ± 2.5%). Oil addition led to a further reduction in UTS and elongation (6.2 ± 0.4 MPa and 3.6 ± 0.0%), while the modulus returned to a value statistically similar to neat F-EPS. FTIR and XRD confirmed preservation of the EPS chemical fingerprint and a predominantly amorphous structure ($2\theta \approx 20$–30°). Overall, EPS + CNC + OIL films combine hydrophobicity, UV-screening, and elastic modulus similar to neat F-EPS, supporting their use as moisture-resistant, UV screening protective topcoats for non-food-contact paperboard packaging. Full article

Nanocellulose materials (CNMs), encompassing cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial nanocellulose (BNC), have emerged as a versatile and sustainable class of bio-based nanomaterials with significant promise for applications in mechanical engineering. This review systematically examines the processing of nanocellulose via mechanical, chemical, and enzymatic routes, alongside surface modification strategies that enhance performance and address scalability challenges. A principal advantage of CNMs lies in their exceptional mechanical properties, including superior strength, stiffness, and toughness, which position them as high-performance, sustainable reinforcement agents for advanced composites. Beyond mechanical reinforcement, CNMs exhibit a suite of functional properties critical for engineering design, such as thermal stability, tunable conductivity, effective gas/moisture barrier performance, and improved tribological behavior. These characteristics enable their use in diverse high-value applications, including lightweight composites, protective coatings, energy storage devices, sensors, actuators, and intelligent material systems. Furthermore, the inherent renewability, biodegradability, and recyclability of nanocellulose align closely with the principles of a circular economy and green engineering. However, the successful integration of CNMs into mainstream manufacturing requires overcoming key challenges. These include the energy intensity of certain production processes, inherent moisture sensitivity, long-term stability under operational conditions, and compatibility with established industrial techniques. Life-cycle analyses reveal important environmental trade-offs that must be navigated. Overall, nanocellulose represents a renewable, multi-functional material platform whose unique combination of mechanical performance, functional versatility, and environmental benefits is poised to drive innovation in next-generation engineering materials. Full article

Cadmium contamination of water resources represents a serious environmental and public health challenge, with conventional treatment methods often proving inadequate for industrial-level remediation. In this study, we present a novel, sustainable composite material, functionalized cellulose nanocrystal polyvinyl alcohol zinc oxide ferric chloride (CNC-PVA-ZnOFe) beads for the efficient removal of cadmium from contaminated water. The material integrates adsorption, coagulation, and flocculation mechanisms within a single hybrid platform, with coagulation–flocculation serving as the dominant mechanism given the material’s macroporous structure and limited surface area (1.2–3.3 m²/g). Functionalized cellulose nanocrystals provide supporting adsorptive sites for metal binding, while a PVA matrix incorporating ZnOFe improves structural integrity, mechanical stability, and coagulation performance. Characterization confirmed successful functionalization, enhanced thermal stability, and a macroporous structure (12–52 nm pores) conducive to floc entrapment, though with limited surface area (1.2–3.3 m²/g) for conventional adsorption. Under optimized conditions (pH 7–10, initial Cd²⁺ concentration of 100 mg/L, coagulant dose of 0.1 g, and sedimentation time of 60 min), the functionalized CNC-PVA-ZnOFe beads achieved a cadmium removal efficiency of 78%, achieving significantly higher cadmium removal efficiency than traditional coagulants, such as aluminum sulfate (69%). The beads also demonstrated good reusability, retaining 85% removal efficiency after five regeneration cycles. This work presents a scalable, eco-friendly material for cadmium removal under controlled laboratory conditions using synthetic solutions. However, further evaluation in real wastewater matrices containing competing ions and organic matter is necessary to establish practical applicability for water treatment applications. The study highlights the combined potential of multifunctional hybrid materials while acknowledging the need for validation under environmentally relevant conditions. While the results indicate successful integration of multiple removal mechanisms, direct validation of synergistic interactions through techniques such as zeta potential and XPS analysis remains an important direction for future research. Full article

Conventional paints pose major environmental and health concerns due to their reliance on heavy-metal pigments and volatile organic compound (VOC)-emitting binders, emphasizing the need for sustainable alternatives. Previous formulations of biologic paints that combined bacteria-derived dsRED pigment protein and casein-based binders, while devoid of toxic components, suffered from prolonged drying times (~16 min), limiting their practical applicability. The present study addresses this key limitation by incorporating cellulose nanocrystals (CNC) and chitosan as biologic additives to enhance drying kinetics. Paint formulations containing 2%, 5%, and 10% of each additive were tested under controlled environmental conditions (20 °C, 60% relative humidity) following the GB/T 1728–2020 standard. Both CNC and chitosan significantly reduced drying time in a concentration-dependent manner (p < 0.001). The 10% CNC and 10% chitosan formulations achieved 61% and 44% reductions in drying time, respectively, relative to the unmodified biologic paint (12.96 ± 1.07 min at baseline). Regression analyses indicated that each 1% increase in CNC or chitosan concentration reduced drying time by 0.77 min and 0.58 min, respectively. The optimized paints exhibited acceptable drying times (5–7 min). These findings demonstrate an advancement in the development of biologically derived coatings, providing a feasible pathway toward safe and sustainable alternatives to conventional synthetic paints. Full article

Developing advanced functional materials requires the synergistic integration of nanoscale reinforcements with tailored properties. In this work, composite films of cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and reduced graphene oxide (rGO) were synthesized using a combination of solution casting, high shear homogenization, vacuum filtration, and environmentally friendly chemical reduction. The resulting CNC/CNF/rGO films exhibited a robust hierarchical structure with strong interfacial interactions, enabling exceptional mechanical properties, specifically a tensile strength of 215 MPa and a Young’s modulus of 18 GPa, alongside a continuous conductive network confirmed by frequency-independent electrical conductivity up to 30 kHz. Comprehensive dielectric characterization revealed frequency-dependent permittivity and low dielectric loss, aligning with Maxwell–Wagner theoretical predictions for heterogeneous composites. The composites also demonstrated thermal stability, with electrical conductivity increasing monotonically from 0 °C to 200 °C. These findings highlighted the CNC/CNF/rGO films’ suitability for applications in flexible electronics, electromagnetic shielding, packaging, and high-performance structural materials. Future optimization and modeling approaches, including fractional calculus, are recommended to further enhance multifunctionality and exploit the unique synergistic interactions intrinsic to nanocellulose–graphene oxide platforms. Full article

This study reports the valorization of oil palm empty fruit bunches into cellulose nanocrystals (CNCs) for the removal of the chemical oxygen demand (COD) from industrial wastewater generated by the same processing sector. Cellulose I_β was first isolated through sequential bleaching, delignification, and mercerization, and two hydrolysis routes were evaluated to obtain CNCs: a concentrated acid route (60% v/v H₂SO₄, 50 °C, 60 min) for CNCs-1 and a low-acid, long-duration route (1% v/v H₂SO₄, 80 °C, 12 h) for CNCs-2. Rietveld refinement of the X-ray diffractograms confirmed the polymorphic transition, assigning cellulose I_β to the intermediate materials and cellulose II to the CNC samples, with crystallite sizes of 4.99 nm for CNCs-1 and 5.43 nm for CNCs-2. Attenuated Total Reflectance–Fourier Transform Infrared (ATR-FTIR) spectroscopy analysis showed the progressive removal of lignin and hemicellulose and supported the cellulose I_β to II transition through changes in hydroxyl bonding and crystallinity-related bands. Preliminary adsorption tests showed better COD removal with CNCs-2, which were therefore selected for optimization using a Box–Behnken design with the adsorbent mass, pH, and contact time as variables. The quadratic model was significant (R² = 0.9675; predicted R² = 0.8908), and the maximum COD removal reached 91.47%, decreasing the COD concentration from 2459.0 to 209.85 mg L⁻¹ under the optimum conditions of 0.09 g CNCs-2, pH 3, and 20 min. These results highlight cellulose II nanocrystals derived from oil palm waste as a promising and scalable adsorbent for industrial wastewater treatment. Full article

Cellulose nanocrystals (CNCs) are highly desirable nanomaterials for reinforcing biopolymer films. Coconut husks are generated in massive quantities after harvesting and processing, leading to waste management issues. This study isolated and characterized CNCs from young (y-CNCs) and mature (m-CNCs) coconut husks via acid hydrolysis (32% H₂SO₄, 50 °C, 5 h), comparing them with commercial CNCs (c-CNCs) to evaluate their performance in gelatin-based films. TEM confirmed rod-shaped morphology for all CNCs. Notably, m-CNCs exhibited a smaller particle size (199 nm), a higher surface charge (−46.8 mV), and superior crystallinity (63.98%), demonstrating properties comparable to c-CNCs. FTIR and XRD confirmed characteristic cellulose functional groups and crystalline structure, while TGA demonstrated excellent thermal stability above 300 °C for all samples. Incorporation of CNCs into gelatin films significantly improved tensile strength (from 15.63 to 24.93 MPa) and reduced water vapor permeability (from 2.65 to 2.43 × 10⁻¹⁰ g m m⁻² s⁻¹ Pa⁻¹; p < 0.05). These findings demonstrate how coconut husk residues can be upcycled into high-value nanomaterials fostering economic growth with innovation in sustainable manufacturing. This research also promotes responsible waste utilization, highlighting the benefits of biodegradability and a reduced carbon footprint for sustainable food packaging applications. Full article

Bio-based polymers are believed to often demonstrate insufficient barrier capacity and mechanical strength, especially in egg packaging processes. This current work attempted to improve the characteristics of chitosan (CS) films for egg packaging by incorporating cellulose nanocrystals (CNC) and sodium montmorillonite (MMT) nanoparticles. Such nanofillers added to the polymer matrix should reduce water vapor permeability and improve the mechanical properties of bio-nanocomposite films. Herein, coatings containing 5 wt% CNC or MMT incorporated into chitosan were applied to enhance the storability of fresh eggs over 5 weeks at ambient conditions. SEM images revealed that coatings were able to seal the eggshell pores, thereby minimizing mass transfer. After 5 weeks of storage, the Haugh unit (HU) of eggs treated with CS–CNC (67.1) and CS–MMT (64.8) appeared reasonably higher than that of control (35.2) and pure chitosan (52.1). The yolk index of eggs coated with CS–CNC (0.355) and CS–MMT (0.343) surpassed both control (0.263) and CS-coated eggs (0.308). However, pH levels in the albumen of eggs coated with CNC or MMT nanocomposite were significantly lower than others during storage. Potentially, chitosan-based nanocomposite coatings could be effective in preserving the internal quality of eggs, providing a somewhat efficient barrier against CO₂ loss with relative pH maintenance. Full article

The limited stability of anthocyanins restricts their application in the food industry, necessitating encapsulation to prevent degradation. This study fabricated an anthocyanin-rich acidic water-in-oil-in-water (W₁/O/W₂) emulsion system stabilized by cellulose nanocrystals (CNCs). Anthocyanins extracted from the by-product peels of ‘France’ Prunus domestica L. were incorporated into the inner aqueous phase (W₁). The internal phase (W₁/O) ratio was increased to 40% (w/w) to enhance anthocyanin loading capacity. CNCs were sonicated to reduce their size and improve their interfacial properties, thereby enhancing the emulsifying capacity. Sonicated CNCs combined with whey protein isolate (WPI) significantly improved double emulsion performance compared to the non-sonicated CNCs–WPI system: (1) reduced D₄₃ from 8.50 µm to 4.35 µm; (2) elevated ζ-potential from 7.49 ± 0.99 mV to 10.07 ± 1.50 mV; and (3) improved encapsulation efficiency from 52.96 ± 2.60% to 83.39 ± 0.96%. Furthermore, encapsulated anthocyanins exhibited significantly enhanced thermal stability compared to free anthocyanins, with the half-life at 50 °C increasing from 14.72 ± 0.35 h to 70.37 ± 0.51 h. This study demonstrates that modifying nanoparticle interfacial properties provides valuable insights for designing stable emulsions and enhancing anthocyanin stability. Full article

Cellulose nanocrystals (CNCs) possess outstanding mechanical properties and sustainability; however, their hydrophilic nature makes their dispersion challenging in hydrophobic bioplastic matrices. Surface modification of CNC is therefore inevitable for effective nanocomposite fabrication. In this study, CNC surface was modified using a green, water-based grafting-from method, enabling the growth of poly(2-hydroxyethyl methacrylate) (PHEMA) chains directly from its surface. This modification decreases intermolecular hydrogen bonding among CNCs and enhances their compatibility with poly(butylene adipate-co-terephthalate) (PBAT), a commercially available biodegradable aliphatic–aromatic copolyester widely used in sustainable packaging applications. The enhanced interfacial interaction arises from both the improved dispersion of CNCs within the PBAT matrix and the ability of PHEMA’s hydroxyl groups to form secondary interactions with PBAT. To examine how grafted polymer chain length influences CNC dispersion, PHEMA was grown from CNC surfaces at different grafting degrees. Additionally, PHEMA homopolymers were synthesized and melt-mixed with PBAT to evaluate the role of PHEMA in the absence of CNC. Neat and modified CNCs (mCNCs) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, water contact angle measurements, wettability tests, and thermogravimetric analysis. Nanocomposites containing 3 wt% neat CNCs, mCNCs, or PHEMA homopolymers were subsequently prepared using an internal melt mixer. Melt rheology, differential scanning calorimetry, and dynamic mechanical analysis were then used to characterize the final viscoelastic and thermomechanical behavior of the resulting nanocomposites. The increased storage modulus and complex viscosity of the nanocomposites confirmed that the CNCs grafted with an intermediate PHEMA chain length exhibited improved network formation and enhanced interfacial interaction with PBAT. Full article

Hydrogel-based products are used in many areas of biomedicine and healthcare. Recently, the incorporation of cellulose nanocrystals (CNC), a renewable and functional nanomaterial, into hydrogels has enhanced their functionality, particularly by imparting mechanical strength and structural integrity. This scoping review aims to appraise the types of biomedical models and assays that have been utilised to investigate the effects of CNC incorporation into hydrogels in tissue engineering, wound healing, medical implantation and drug delivery applications, and reports on the rationale for including these models and assays. A structured literature search was undertaken in major scientific databases (PubMed Central, PubMed, BioMed Central, ScienceDirect, Wiley and EBSCOhost), focusing on identifying primary research published between 2016 and 2024. From this process, fifteen studies providing biomedical analyses met the inclusion criteria. Most of these investigations employed in vitro cell-line models (n = 12), with a smaller number utilising in vivo experimental systems (n = 5). Across the included studies, CNC incorporation typically yielded measurable performance gains: reported compressive or storage modulus improvements of 20–40% over hydrogel-only controls, consistently high cell viability (>85%) across multiple human and murine cell types for up to 21 days, and sustained drug release profiles (days–weeks) in stent and antitumour contexts. Where quantified, functional outcomes in vivo included preserved graft volume (autologous fat grafts) and reduced intimal hyperplasia signals in vascular graft models. Critical gaps included heterogeneous CNC sources and surface chemistries, inconsistent reporting of CNC concentration and hydrogel formulation parameters, the limited duration and scope of biocompatibility testing, and minimal alignment with standard evaluation protocols, constraining reproducibility and cross-study comparability. To date, there are no human clinical trials of CNC-hydrogels. Translational readiness will require standardised ISO-compliant biocompatibility evaluations. Large-animal studies under relevant mechanical and physiological conditions, and rigorous long-term degradation and immunogenicity assessments to de-risk progression to human trials. We recommend standardised CNC sources and surface functionalisation reporting, concentration (wt%) ranges, hydrogel rheological characterisation (G′, G″, swelling), and consistent biological endpoints (viability, differentiation, inflammation panels) to enable robust meta-analyses and translational benchmarking. Distinct from prior nanocellulose reviews that emphasise material synthesis and properties, this analysis centres on the biomedical models and assays applied to CNC-incorporated hydrogels, identifying the methodological convergence and divergence that directly impact translational pathways. Full article