Energy efficient facile extraction process of cellulose nanofibres and their dimensional characterization using light scattering techniques

Thermal Insulation Mechanism, Preparation, and Modification of Nanocellulose Aerogels: A Review

Energy problems have become increasingly prominent. The use of thermal insulation materials is an effective measure to save energy. As an efficient energy-saving material, nanocellulose aerogels have broad application prospects. However, nanocellulose aerogels have problems such as poor mechanical properties, high flammability, and they easily absorbs water from the environment. These defects restrict their thermal insulation performance and severely limit their application. This review analyzes the thermal insulation mechanism of nanocellulose aerogels and summarizes the methods of preparing them from biomass raw materials. In addition, aiming at the inherent defects of nanocellulose aerogels, this review focuses on the methods used to improve their mechanical properties, flame retardancy, and hydrophobicity in order to prepare high-performance thermal insulation materials in line with the concept of sustainable development, thereby promoting energy conservation, rational use, and expanding the application of nanocellulose aerogels.

Insights into thermal degradation kinetics and liquid crystalline behavior of cellulose nanocrystals from the waste of Cajanus cajan (pigeon pea)

Cellulose nanocrystals (CNCs) are essential for advancing nanotechnology and modern science. This work used the Cajanus cajan stem, an agricultural waste, as a lignocellulosic mass, which can serve as a supply of CNCs. After extraction from the Cajanus cajan stem, CNCs have been thoroughly characterized. FTIR (Infrared Spectroscopy) and ssNMR (solid-state Nuclear Magnetic Resonance) successfully validated eliminating additional components from the waste stem. The ssNMR and XRD (X-ray diffraction) were utilized to compare the crystallinity index. For structural analysis, the XRD of cellulose I_β was simulated to compare with the extracted CNCs. Various mathematical models inferred thermal stability and its degradation kinetics to ensure its high-end applications. Surface analysis established the rod-like shape of the CNCs. Rheological measurements were performed to gauge the liquid crystalline properties of CNC. The anisotropic liquid crystalline CNCs' birefringence proves that the Cajanus cajan stem is a promising resource for making CNCs for cutting-edge applications.

Surfactant Assisted In Situ Synthesis of Nanofibrillated Cellulose/Polymethylsilsesquioxane Aerogel for Tuning Its Thermal Performance

Nanofibrillated cellulose (NFC) and polymethylsilsesquioxane (PMSQ) based aerogel are prepared by the sol-gel method. The objective of this work is to study the impact of surfactant and base catalyst on the thermal and mechanical performance of the corresponding aerogel. The rheological premonitory assists in predicting the bulk properties of the aerogel. The chemical structure of the aerogel is studied by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and solid-state nuclear magnetic resonance (NMR). X-ray microtomographic (XMT) analysis confirms the homogeneous and monolithic structure of the aerogel. The lowest thermal conductivity is achieved as 23.21 mW m^-1 K^-1 with V-0 and HBF rating through UL-94 test. Thermal performance of aerogels is cross-verified through modeling and simulation in COMSOL multiphysics platform. The mechanical properties of aerogel are evaluated by monolithic compression test in axial and radial compression test up to 90% strain, cyclic compression loading-unloading, and reloading test, flexural test, and dynamic mechanical analysis. The time-temperature analysis has shown around 5 °C temperature difference in the middle of the room after using the aerogel panel at the exposed surface, which assists in the practical application of the synthesized aerogel panel.

Switchable Photonic Bio-Adhesive Materials

A soft photonic bio-adhesive material is designed with real-time colorimetrical monitoring of switchable adhesion by integrating a responsive bio-photonic matrix with mobile hydrogen-binding networking. Synergetic materials sequencing creates a unique iridescent appearance directly coupled with both adhesive ability and shearing strength, in a highly reversible manner. The responsive photonic materials, having a physically hydrogen-bonded chiral nematic organization, vary their adhesion strength due to a transition in cohesive and interfacial failure mechanism in humid surroundings. The bright color appearance shifts from blue to red to transparent and back due to a change in pitch length of the chiral helicoidal organization that also triggers coupled changes in both mechanical strength and interfacial adhesion. Such reversible strength-adhesion-iridescence triple-coupling phenomenon is further explored for design of super-strong switchable bio-adhesives for synthetic/biological surfaces with quick remotely triggered sticky-to-nonsticky transitions, removable conformal soft stickers, and wound dressings with visual monitoring of the healing process, to colorimetric stickers for contaminated respiratory masks.

Carbonized Cellulose Nanofibril with Individualized Fibrous Morphology: toward Multifunctional Applications in Polycaprolactone Conductive Composites

Drying cellulose nanofibril (CNF) from aqueous suspensions often leads to aggregated fibril morphology, negatively affecting its performance in ensuing applications. In this work, we introduced a new solvent drying approach to acquire dry CNF from aqueous suspensions and subsequently pyrolyzed the CNF precursor to obtain carbonized CNF (CCNF) without loss of its fibrous morphology. The fibrous CCNF was dispersed homogeneously in polycaprolactone (PCL) thermoplastic resin, greatly enhancing PCL composite tensile performance. After being further mixed with carbon black (CB), the CCNF helped to minimize CB aggregation due to formation of interconnected three-dimensional (3D) structures. The CCNF/CB/PCL composite exhibited superior electrical conductivity ascribed to electrons transporting more efficiently among CB aggregates. The composite is also suitable for applications such as 3D printed electromagnetic interference (EMI) shielding and deformation sensing. Specifically, the 3D printed EMI shielding composite efficiently absorbed EM radiation in the frequency range of 4-26 GHz, and the 3D printed deformation sensor exhibited excellent sensitivity, durability, and flexibility in monitoring mechanical distortions. Herein, this study sheds light on the development of multifunctional conductive composites embedded with fibrous CCNF from sustainable resources.

TEMPO-oxidized cellulose fibers from wheat straw: Effect of ultrasonic pretreatment and concentration on structure and rheological properties of suspensions

Cellulose and TEMPO-oxidized cellulose fibers (TOCF) from the wheat straw were prepared with ultrasonic and chemical treatments to investigate structure and functionalities. Sol-gel transition of TOCF suspensions has been investigated using rheology to unveil the roles of ultrasonic pretreatment and temperature at various concentration. It was found that TOCF extracted with or without ultrasonic pretreatment exhibit similar functional groups in FTIR. However, different crystal structures and thermal stabilities were revealed in XRD and TGA, respectively. The gelation was independent of the ultrasonic pretreatment, while the rheological properties were highly infuenced by the concentration and temperature of the TOCF suspensions. TOCF suspensions presented a strain thinning behavior in large amplitude oscillatory shear tests. Lissajous curves showed that the elastoplastic behavior was predominantly modulated by the fiber concentration and strain amplitude other than the ultrasonic pretreatment. These results could improve the understanding of the relationships between TOCF structure and rheological properties.

Microdesigned Nanocellulose-Based Flexible Antibacterial Aerogel Architectures Impregnated with Bioactive Cinnamomum cassia

This work is strategically premeditated to study the potential of a herbal medicinal product as a natural bioactive ingredient to generate nanocellulose-based antibacterial architectures. In situ fibrillation of purified cellulose was done in cinnamon extract (ciE) to obtain microfibrillated cellulose (MFC). To this MFC suspension, carboxylated cellulose nanocrystals (cCNCs) were homogeneously mixed and the viscous gel thus obtained was freeze-dried to obtain lightweight and flexible composite aerogel architectures impregnated with ciE, namely, ciMFC/cCNCs. At an optimal concentration of 0.3 wt % cCNCs (i.e., for ciMFC/cCNCs_0.3), an improvement of around 106% in compressive strength and 175% increment in modulus were achieved as compared to pristine MFC architecture. The efficient loading and interaction of ciE components, specifically cinnamaldehyde, with MFC and cCNCs resulted in developing competent antibacterial surfaces with dense and uniform microstructures. Excellent and long-term antimicrobial activity of the optimized architectures (ciMFC/cCNCs_0.3) was confirmed through various antibacterial assays like the zone inhibition method, bacterial growth observation at OD₆₀₀, minimum inhibitory concentration (MIC, here 1 mg/mL), minimum bactericidal concentration (MBC, here 3-5 mg/mL), and Live/Dead BacLight viability tests. The changes in the bacterial morphology with a disrupted membrane were further confirmed through various imaging techniques like confocal laser scanning microscopy, FESEM, AFM, and 3D digital microscopy. The dry composite architecture showed the persuasive capability of suppressing the growth of airborne bacteria, which in combination with antibacterial efficiency in the wet state is considered as an imperative aspect for a material to act as the novel biomaterial. Furthermore, these architectures demonstrated excellent antibacterial performance under real "in use" contamination prone conditions. Hence, this work provides avenues for the application of crude natural extracts in developing novel forms of advanced functional biomaterials that can be used for assorted biological/healthcare applications such as wound care and antimicrobial filtering units.

Removal of Cadmium and Chromium by Mixture of Silver Nanoparticles and Nano-Fibrillated Cellulose Isolated from Waste Peels of Citrus Sinensis

Nano-fibrillated cellulose (NFC) was extracted by a chemical method involving alkali and acid hydrolysis. The characterisation of the citrus sinensis fruit peel bran and nano-fibrillated cellulose was performed by XRD, FTIR, TEM, and FESEM. XRD confirmed the phase of NFC which showed monoclinic crystal with spherical to rod shape morphology with a size of 44-50 nm. The crystallinity index of treated NFC increased from 39% to 75%. FTIR showed the removal of lignin and hemicellulose from waste peels due to the alkaline treatment. Silver nanoparticles were also synthesised by utilizing extract of citrus sinensis skins as a reducing agent. Pharmaceutical effluent samples from an industrial area were tested by Atomic Absorption Spectrometry. Out of the four metals obtained, cadmium and chromium were remediated by silver nanoparticles with nano-fibrillated cellulose via simulated method in 100 mg/L metal-salt concentrations over a time period of 160 min. The highest removal efficiency was found for cadmium, i.e., 83%, by using silver and NFC together as adsorbents. The second highest was for chromium, i.e., 47%, but by using only NFC. The Langmuir and Freundlich isotherms were well fitted for the sorption of Cd (II) and Cr (II) with suitable high R2 values during kinetic simulation. Thus, the isolation of NFC and synthesis of silver nanoparticles proved efficient for heavy metal sorption by the reuse of waste skins.

Isolation and characterization of micro and nanocrystalline cellulose fibers from the walnut shell, corncob and sugarcane bagasse

The present study aims to extract and characterize the microcrystalline cellulose (MCC) present in different agro-industrial wastes such as walnut shells, corncob, and sugarcane bagasse. Moreover, it is also the aim of this study to convert MCCs to nanocrystalline cellulose fiber (NCCF), to demonstrate the difference in morphological, structural, thermal, and chemical natures. Corncob cellulose was observed to possess a loosely bounded linear bundle structure. Nanocrystalline cellulose fiber yield from walnut shell and sugarcane bagasse cellulose were higher than corncob cellulose. The thermal stability of cellulose was noted to be high for walnut shell NCCF. Nanocrystalline cellulose fiber of corncob and sugarcane bagasse was estimated to have a low thermal degradation temperature. All the MCCs and NCCFs produced from investigated cellulose sources were found to have type I cellulose. Functional group compositions of cellulose were observed to be intact for converted agro-based NCCF's.

Plant-based nanocellulose: A review of routine and recent preparation methods with current progress in its applications as rheology modifier and 3D bioprinting

"Nanocellulose" have captivated the topical sphere of sturdily escalating market for sustainable materials. The review focuses on the comprehensive understanding of the distinct surface chemistry and functionalities pertaining to the renovation of macro-cellulose at nanodimensional scale to provide an intuition of their processing-structure-function prospective. The abundant availability, cost effectiveness and diverse properties associated with plant-based resources have great economical perspective for developing sustainable cellulose nanomaterials. Hence, emphasis has been given on nanocellulose types obtained from plant-based sources. An overarching goal is to provide the recent advancement in the preparation routes of nanocellulose. Considering the excellent shear thinning/thixotropic/gel-like behavior, the review provids an assemblage of publications specifically dealing with its application as rheology modifier with emphasis on its use as bioink for 3D bioprinting for various biomedical applications. Altogether, this review has been oriented in a way to collocate a collective data starting from the historical perspective of cellulose discovery to modern cellulosic chemistry and its renovation as nanocellulose with recent technological hype for broad spanning applications.

Clinical efficacy of conjoint fascial sheath suspension and frontalis muscle suspension in treating moderate or severe congenital ptosis and the effects on ocular surface and refractive status

Clinical efficacy of conjoint fascial sheath suspension and frontalis muscle suspension was explored in treating moderate or severe congenital ptosis and their effects on ocular surface and refractive status. A total of 75 patients with moderate or severe ptosis (108 eyes) treated in Yidu Central hospital from June 2014 to June 2019 were enrolled in this study, and divided into group A and group B. Group A was treated with conjoint fascial sheath suspension (n=38, 55 eyes), while group B was treated with frontalis muscle suspension (n=37, 53 eyes). The following data of the two groups were compared: General baseline data, total correction efficiency, satisfaction, and ocular surface after surgery, refractive status, and complications at three months after surgery. The two groups showed no significant difference in general data (P>0.05), but group A showed higher total correction efficiency and satisfaction, and less complications than those in group B (all P<0.05). In addition, the two groups had no difference in terms of ocular surface, tear break-up time, or Schirmer test level after surgery (all P>0.05), and showed no refraction changes after surgery (P>0.05). In terms of refractive status and ocular surface, the two surgery methods are not very different, but in terms of efficacy, conjoint fascial sheath suspension is more advantageous than frontalis muscle suspension, and it brings less complications, and enjoys a higher satisfaction, so it is worthy of promotion.

Bio-extract amalgamated sodium alginate-cellulose nanofibres based 3D-sponges with interpenetrating BioPU coating as potential wound care scaffolds

In this work, sodium alginate (SA) based "all-natural" composite bio-sponges were designed for potential application as wound care scaffold. The composite bio-sponges were developed from the aqueous amalgamation of SA and cellulose nanofibres (CNFs) in bio-extracts like Rice water (Rw) and Giloy extract (Ge). These sponges were modified by employing a simple coating strategy using vegetable oil-based bio-polyurethane (BioPU) to tailor their physicochemical and biological properties so as to match the specific requirements of a wound care scaffold. Bio-sponges with shared interpenetrating polymeric network structures were attained at optimized BioPU coating formulation. The interpenetration of BioPU chains within the sponge construct resulted in the formation of numerous micro-networks in the interconnected microporous structure of sponges (porosity ≥75%). The coated sponge showed a superior mechanical strength (compressive strength ~3.8 MPa, compressive modulus ~35 MPa) with appreciable flexibility and recoverability under repeated compressive loading-unloading cycles. A tunable degradation behaviour was achieved by varying BioPU coating concentrations owing to the different degree of polymer chain entanglement within the sponge construct. The physical entanglement of BioPU chains with core structural components of sponge improved their structural stability by suppressing their full fragmentation in water-based medium without affecting its swelling behaviour (swelling ratio > 1000%). The coated sponge surface has provided a suitable moist-adherent physical environment to support the adhesion and growth of skin cells (HaCaT cells). The MTT (3-(4,5-dimethyl thiazolyl-2)-2,5-diphenyltetrazolium bromide) assay and hemolytic assay revealed the non-toxic and biocompatible nature of coated sponges in vitro. Moreover, no signs of skin erythema or edema were observed during in vivo dermal irritation and corrosion test performed on the skin of Sprague Dawley (SD) rats. Our initial observations revealed the credibility of these sponges as functional wound care scaffolds as well as its diverse potential as a suitable substrate for various tissue engineering applications.

Esterified superhydrophobic nanofibrillated cellulose based aerogel for oil spill treatment

The present work aims towards the structuring of a physically cross-linked aerogels based on nanofibrillated cellulose (NFC) and polyvinyl alcohol (PVA), i.e., NFC/PVA aerogels for oil spillage cleanup. Highly porous (98%) NFC/PVA aerogels having both meso-micro pores were achieved by freeze drying technique. To impart super-hydrophobicity to the composite aerogel, a simple dip coating process was adopted using stearic acid chloride (SAC) solution. The SAC conjugated aerogels combined both superhydrophobic and oleophilic characteristics showed a contact angle of ∼159° and ∼0° with water and oil respectively. FESEM and X-ray microtomography images revealed a self-assembled 3D porous cellular structure of the aerogels. The prepared aerogels were found to be very efficient in separating a series of oil/water mixtures and various organic solvents with excellent selectivity and recyclability. Absorption capacity of the aerogels was at least 35 times higher than their dry weight. Simple mechanical squeezing method was adopted for repetitive uses.

Opuntia Ficus-Indica L. Miller (Palma Forrageira) as an Alternative Source of Cellulose for Production of Pharmaceutical Dosage Forms and Biomaterials: Extraction and Characterization

Cellulose is among the top 5 excipients used in the pharmaceutical industry. It has been considered one of the main diluents used in conventional and modern dosage forms. Therefore, different raw materials of plant origin have been evaluated as potential alternative sources of cellulose. In this context, Opuntia ficus-indica L. Miller (palma forrageira), a plant of the cactus family that has physiological mechanisms that provide greater productivity with reduced water requirements, is an interesting and unexplored alternative for extracting cellulose. By using this source, we aim to decrease the extraction stages and increase the yields, which might result in a decreased cost for the industry and consequently for the consumer. The aim of this work was to investigate the use of Opuntia ficus-indica L. Miller as a new source for cellulose extraction, therefore providing an efficient, straight forward and low-cost method of cellulose II production. The extraction method is based on the oxidation of the lignins. The obtained cellulose was identified and characterized by spectroscopic methods (FTIR and NMR), X-ray diffraction, thermal analysis (TGA-DTG and DSC) and scanning electron microscopy. The results confirmed the identity of cellulose and its fibrous nature, which are promising characteristics for its use in the industry and a reasonable substrate for chemical modifications for the synthesis of cellulose II derivatives with different physicochemical properties that might be used in the production of drug delivery systems and biomaterials.

Synergistic effect of cellulose nanofibres and bio- extracts for fabricating high strength sodium alginate based composite bio-sponges with antibacterial properties

This study investigates the synergistic potential of natural bio-extracts for preparing "all-natural" composite bio-sponges of sodium alginate (SA) with the reinforcement of a natural bio-nanomaterial i.e., cellulose nanofibres (CNFs). Aqueous suspensions of SA and CNFs in various combinations of bio-extracts (Rice water (Rw) and Giloy extract (Ge)) were freeze-dried to obtain the composite bio-sponges. Composites prepared using Rw resulted in structurally more stable samples with porosity above 75% that showed a compact honeycomb-like microstructure with interlocked CNFs network structures. A significant improvement in mechanical performance (400% increment in compressive strength and 800% increment in modulus) and thermal stability (decomposition temperature reaching up to 240 °C from 200 °C) for SA based composite bio-sponges was achieved due to the synergistic effect of Rw and CNFs as compared to conventionally prepared sponges in water. Additionally, the use of Ge has resulted in developing antimicrobial surfaces with up to 98% and 90% growth inhibition efficiency for gram-negative and gram-positive bacteria, respectively. Hence, CNFs and bio-extracts together played a competent role in effective tailoring of structural, thermo-mechanical and antibacterial properties of composite bio-sponges.

Extraction of nano cellulose fibers from the banana peel and bract for production of acetyl and lauroyl cellulose

The principal aim of the present study is to develop a method for the production of cellulose nanofibers, from the banana peel (BP) and bract (BB). It is also the aim of this study to produce cellulose-based biopolymers through acetyl and lauroyl modifications. The microwave digestion method and ball milling assisted ultra-sonication method was optimized for sustainable extraction of micro and nano cellulose fibers, respectively. The microwave digestion method was found to be effective in the removal of hemicellulose and lignin. Micro and nano cellulose fibers of BP and BB were found to contain type I cellulose structure. Thermal stability and crystallinity index of cellulose nanofibers were examined to be higher than it's native micro cellulose. Nano cellulose fibers were examined to be a potential source for production of acetyl and lauroyl cellulose, with a high degree of substitution and thermal stability. Hence, microwave digestion and ball milling assisted ultra-sonication method was proven to be effective in the extraction of nano cellulose fiber for development of cellulose-based polymers.