Performances of Transcritical Power Cycles with CO2-Based Mixtures for the Waste Heat Recovery of ICE.

In the waste heat recovery of the internal combustion engine (ICE), the transcritical CO2 power cycle still faces the high operation pressure and difficulty in condensation. To overcome these challenges, CO2 is mixed with organic fluids to form zeotropic mixtures. Thus, in this work, five organic fluids, namely R290, R600a, R600, R601a, and R601, are mixed with CO2. Mixture performance in the waste heat recovery of ICE is evaluated, based on two transcritical power cycles, namely the recuperative cycle and split cycle. The results show that the split cycle always has better performance than the recuperative cycle. Under design conditions, CO2/R290(0.3/0.7) has the best performance in the split cycle. The corresponding net work and cycle efficiency are respectively 21.05 kW and 20.44%. Furthermore, effects of key parameters such as turbine inlet temperature, turbine inlet pressure, and split ratio on the cycle performance are studied. With the increase of turbine inlet temperature, the net works of the recuperative cycle and split cycle firstly increase and then decrease. There exist peak values of net work in both cycles. Meanwhile, the net work of the split cycle firstly increases and then decreases with the increase of the split ratio. Thereafter, with the target of maximizing net work, these key parameters are optimized at different mass fractions of CO2. The optimization results show that CO2/R600 obtains the highest net work of 27.43 kW at the CO2 mass fraction 0.9 in the split cycle.

Self-healing cellulose nanocrystal-stabilized droplets for water collection under oil.

The removal of small water droplets from oils is imperative because oils can easily be contaminated or deteriorated by water during transportation, storage and usage. Here, we report superhydrophobic magnetic cellulose nanocrystal (CNC) nanoparticles, which are capable of removing tiny water droplets from oil by forming under oil particle-stabilized droplets. These particle-stabilized droplets can be collected and moved by a magnetic force, and self-healed upon damage by an external force.

Development of Biocompatible Mussel-Inspired Cellulose-Based Underwater Adhesives.

Conventional adhesives have poor underwater adhesion and harm to human health and the environment during their use, which largely limits their practical applications. Herein, we synthesized cellulose-based adhesives with underwater adhesion and biocompatibility by grafting N-(3,4-dihydroxyphenethyl)methacrylamide into the cellulose chain via atom transfer radical polymerization (ATRP). FTIR, 1H NMR, and XPS analyses ensured the successful preparation of the cellulose-based adhesive polymers. The different properties of the prepared adhesives, including swelling ratio, adhesion strength, and biocompatibility are examined. Results found that the lap shear strength is enhanced by increasing the catechol content. When catechol content is 27.2 mol %, cellulose-based adhesive with the addition of Fe3+ possesses a strong lap shear strength of 2.13 MPa in a dry environment, 0.10 MPa underwater, and 0.16 MPa under seawater for iron substrate, respectively. In addition, the cell culture test demonstrated that the prepared adhesives have outstanding biocompatibility. The cellulose-based adhesives with underwater adhesion and biocompatibility have potential applications in biomedicine, electronic engineering, and construction fields.

Recent advances in TEMPO-oxidized cellulose nanofibers: Oxidation mechanism, characterization, properties and applications.

Cellulose is the richest renewable polymer source on the earth. TEMPO-mediated oxidized cellulose nanofibers are deduced from enormously available wood biomass and functionalized with carboxyl groups. The preparation procedure of TOCNFs is more environmentally friendly compared to other cellulose, for example, MFC and CNCs. Due to the presence of functional carboxyl groups, TOCNF-based materials have been studied widely in different fields, including biomedicine, wastewater treatment, bioelectronics and others. In this review, the TEMPO oxidation mechanism, the properties and applications of TOCNFs are elaborated. Most importantly, the recent advanced applications and the beneficial role of TOCNFs in the various abovementioned fields are discussed. Furthermore, the performances and research progress on the fabrication of TOCNFs are summarized. It is expected that this timely review will help further research on the invention of novel material from TOCNFs and its applications in different advanced fields, including biomedicine, bioelectronics, wastewater treatment, and the energy sector.

Biocompatible, Injectable, and Self-Healing Poly(N-vinylpyrrolidone)/Carboxymethyl Cellulose Hydrogel for Drug Release.

Hydrogels have drawn intensive attention as fascinating materials for biomedicine. However, fabricating hydrogels with injectable and self-healing properties remains a challenge. Herein, we reported a biocompatible poly(N-vinylpyrrolidone)/carboxymethyl cellulose (PVP/CMC) hydrogel with excellent injectable and self-healing properties. The PVP/CMC hydrogel exhibits good biocompatible, injectable, and self-healing properties. The sol-gel transition of PVP/CMC hydrogels demonstrates an outstanding self-healing behavior, and the bisected hydrogels can self-heal within 30 s. The hydrogels have a good swelling ratio, and the swelling ratio increases with increasing amount of CMC in PVP and reaches a maximum of 2850% at a 1.0:1.5 PVP and CMC ratio. In addition, the hydrogel possesses excellent drug release capacity, and its drug release rate reaches 70%. Moreover, the release of 4-aminosalicylic acid (4-ASA) in the hydrogel can be controlled by adjusting the proportion of the hydrogel. The PVP/CMC hydrogel with excellent biocompatible, injectable, and self-healing properties has great potential for applications in drug release.

A review of cellulose-based catechol-containing functional materials for advanced applications.

With the increment in global energy consumption and severe environmental pollution, it is urgently needed to explore green and sustainable materials. Inspired by nature, catechol groups in mussel adhesion proteins have been successively understood and utilized as novel biomimetic materials. In parallel, cellulose presents a wide class of functional materials rating from macro-scale to nano-scale components. The cross-over among both research fields alters the introduction of impressive materials with potential engineering properties, where catechol-containing materials supply a general stage for the functionalization of cellulose or cellulose derivatives. In this review, the role of catechol groups in the modification of cellulose and cellulose derivatives is discussed. A broad variety of advanced applications of cellulose-based catechol-containing materials, including adhesives, hydrogels, aerogels, membranes, textiles, pulp and papermaking, composites, are presented. Furthermore, some critical remaining challenges and opportunities are studied to mount the way toward the rational purpose and applications of cellulose-based catechol-containing materials.

Kaempferol attenuates inflammation in lipopolysaccharide-induced gallbladder epithelial cells by inhibiting the MAPK/NF-κB signaling pathway.

Kaempferol (KPR), a flavonoid compound found in various plants and foods, has garnered attention for its anti-inflammatory, antioxidant, and anticancer properties. In preliminary studies, KPR can modulate several signaling pathways involved in inflammation, making it a candidate for treating cholecystitis. This study aimed to explore the effects and mechanisms of KPR on lipopolysaccharide (LPS)-induced human gallbladder epithelial cells (HGBECs). To assess the impact of KPR on HGBECs, the HGBECs were divided into control, KPR, LPS, LPS + KPR, and LPS + UDCA groups. Cell viability and cytotoxicity were evaluated by MTT assay and lactate dehydrogenase (LDH) assay, respectively, and concentrations of KPR (10-200 µM) were tested. LPS-induced inflammatory responses in HGBECs were to create an in vitro model of cholecystitis. The key inflammatory markers (IL-1ß, IL-6, and TNF-α) levels were quantified using ELISA, The modulation of the MAPK/NF-κB signaling pathway was measured by western blot using specific antibodies against pathway components (p-IκBα, IκBα, p-p65, p65, p-JNK, JNK, p-ERK, ERK, p-p38, and p38). The cell viability and LDH levels in HGBECs were not significantly affected by 50 µM KPR, thus it was selected as the optimal KPR intervention concentration. KPR increased the viability of LPS-induced HGBECs. Additionally, KPR inhibited the inflammatory factors level (IL-1ß, IL-6, and TNF-α) and protein expression (iNOS and COX-2) in LPS-induced HGBECs. Furthermore, KPR reversed LPS-induced elevation of p-IκBα/IκBα, p-p65/p65, p-JNK/JNK, p-ERK/ERK, and p-p38/p38 ratios. KPR attenuates the LPS-induced inflammatory response in HGBECs, possibly by inhibiting MAPK/NF-κB signaling.

Porous Scaffolds Based on Polydopamine/Chondroitin Sulfate/Polyvinyl Alcohol Composite Hydrogels.

In this paper, porous scaffolds based on composite hydrogels were fabricated using polydopamine (PDA), chondroitin sulfate (CS), and polyvinyl alcohol (PVA) via the freezing/thawing method. Different characteristics of the prepared composite hydrogels, including the pore sizes, compression strength, lap shear strength, mass loss, and cytocompatibility were investigated. Scanning electron microscope images (SEM) displayed the hydrogel pore sizes, ranging from 20 to 100 µm. The composite hydrogel exhibited excellent porosity of 95.1%, compression strength of 5.2 MPa, lap shear strength of 21 kPa on porcine skin, and mass loss of 16.0%. In addition, the composite hydrogel possessed good relative cell activity of 97%. The PDA/CS/PVA hydrogel is cytocompatible as a starting point, and it can be further investigated in tissue engineering.

Hydrogels with ultra-highly additive adjustable toughness under quasi-isochoric conditions.

Bioinspired smart hydrogels with additive-switchable mechanical properties have been attracting increasing attention in recent years. However, most existing hydrogel systems suffer from limited stiffening amplitude and dramatic volume change upon response to environmental triggers. Herein, we propose a novel strategy to prepare additive-responsive hydrogels with ultra-highly adjustable toughness under quasi-isochoric conditions. The key point lies in tuning the softening transition temperature of the hydrogels with non-covalent interactions between the polymer networks and additives, shifting the hydrogels from glassy to rubbery states. As a proof of concept, a variety of glassy hydrogels are prepared and exposed to additives to trigger responsive performances. Young's modulus of the same hydrogel demonstrates up to 36 000 times ultra-broad-range tunability, ranging from 0.0042 to 150 MPa in response to different additives. Meanwhile, negligible volume changes occur, keeping the hydrogels in quasi-isochoric conditions. Interestingly, the mechanical behaviors of the hydrogels manifest remarkable dependence on the additive type and concentration since both the Hofmeister effect and hydrophobicity of the additives play pivotal roles according to mechanism investigations. Furthermore, the regulation with additives reveals satisfactory reversibility and universality. Taken together, this simple and effective approach provides a novel strategy to fabricate hydrogels with highly tunable toughness for versatile applications, including spatially patterned conductive gels and anti-icing coatings.

Anti-mold, self-cleaning superhydrophobic bamboo fiber/polypropylene composites with mechanical durability.

Bamboo fiber/polypropylene composites (BPCs) have been widely used in buildings, interior decoration, and automobile components. However, pollutants and fungi can interact with the hydrophilic bamboo fibers on the surface of Bamboo fiber/polypropylene composites, degrading their appearance and mechanical properties. To improve their anti-fouling and anti-mildew properties, a superhydrophobic modified Bamboo fiber/polypropylene composite (BPC-TiO2-F) was fabricated by introducing titanium dioxide (TiO2) and poly(DOPAm-co-PFOEA) onto the surface of a Bamboo fiber/polypropylene composite. The morphology of BPC-TiO2-F was analyzed by XPS, FTIR, and SEM. The results showed that TiO2 particles covered on Bamboo fiber/polypropylene composite surface via complexation between phenolic hydroxyl groups and Ti atoms. Low-surface-energy fluorine-containing poly(DOPAm-co-PFOEA) was introduced onto the Bamboo fiber/polypropylene composite surface, forming a rough micro/nanostructure that endowed BPC-TiO2-F with superhydrophobicity (water contact angle = 151.0° ± 0.5°). The modified Bamboo fiber/polypropylene composite exhibited excellent self-cleaning properties, and a model contaminant, Fe3O4 powder, was rapidly removed from the surface by water drops. BPC-TiO2-F showed excellent anti-mold performance, and no mold was on its surface after 28 days. The superhydrophobic BPC-TiO2-F had good mechanical durability and could withstand sandpaper abrasion with a weight load of 50 g, finger wiping for 20 cycles, and tape adhesion abrasion for 40 cycles. BPC-TiO2-F showed good self-cleaning properties, mildew resistance, and mechanical resistance, giving it promising applications for automotive upholstery and building decoration.

Influence of water evaporation/absorption on the stability of glycerol-water marbles.

The porous shell structure of liquid marbles allows liquid vapor to enter in/out of the liquid marbles, leading to the deformation/collapse of liquid marbles, which limits their application as miniature reactors for long-term chemical reactions. In this study, to prevent volatilization and maintain long-term stability, stable liquid marbles were fabricated by encapsulating glycerol/water droplets using superhydrophobic cellulose nanocrystals. The influence of water evaporation and absorption on the stability of aqueous glycerol marbles at different relative humidities (RHs) was investigated. At the same RH, the evaporation/absorption rates of the liquid marbles decreased on increasing the glycerol concentration. For the liquid marbles with the same glycerol volume concentration, the evaporation rates decreased with the increase in RH. The liquid marbles exhibited higher evaporation/absorption resistance compared with pure naked liquid droplets.

Robust superhydrophobic and superoleophilic filter paper via atom transfer radical polymerization for oil/water separation.

Robust superhydrophobic and superoleophilic cellulose-g-PFOEMA filter paper membranes were fabricated via surface grafting of poly(perfluorooctylethyl methacrylate) (PFOEMA) using atom transfer radical polymerization (ATRP). The surface chemical compositions, morphologies and wettability of cellulose-g-PFOEMA with different degree of graft ratio (DG) were investigated using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and contact angle (CA) measurement. IR and XPS showed that PFOEMA were introduced into surface of filter paper. The superhydrophobicity of filter paper increased with amount of PFOEMA grafted. When DG of grafted PFOEMA was higher than 11.2%, the superhydrophobicity reached a steady state and the measured water contact angle was about 157°. The PFOEMA-grafted filter paper exhibited excellent chemical resistance toward a wide range of pH solution from 1 to 12. Cellulose-g-PFOEMA is convenient for oil/water separation with efficiency higher than 95%. The excellent reusability and stability make cellulose-g-PFOEMA filter paper membrane a promising candidate in the applications of oil spillage cleanup and the separation of oil/water mixture.

Self-Healing Cellulose Nanocrystals-Containing Gels via Reshuffling of Thiuram Disulfide Bonds.

Self-healing gels based on reshuffling disulfide bonds have attracted great attention due to their ability to restore structure and mechanical properties after damage. In this work, self-healing gels with different cellulose nanocrystals (CNC) contents were prepared by embedding the thiuram disulfide bonds into gels via polyaddition. By the reshuffling of thiuram disulfide bonds, the CNC-containing gels repair the crack and recover mechanical properties rapidly under visible light in air. The thiuram disulfide-functionalized gels with a CNC content of 2.2% are highly stretchable and can be stretched approximately 42.6 times of their original length. Our results provide useful approaches for the preparation of dynamic CNC-containing gels with implications in many related engineering applications.

TEMPO-Oxidized Cellulose with High Degree of Oxidation.

In this paper, water-soluble 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose with a high degree of oxidation was prepared by a two-step process using bamboo dissolving pulp. The first step was to destroy the cellulose crystal I by NaOH/urea solution to obtain cellulose powder with decreased crystallinity. The second step was to oxidize the cellulose powder by TEMPO oxidation. The TEMPO-oxidized cellulose was analyzed by Fourier transform infrared spectroscopy (FTIR), conductimetry, X-ray diffraction (XRD), fiber analyzer, and transmission electron microscopy (TEM). FTIR showed that the hydroxymethyl groups in cellulose chains were converted into carboxyl groups. The degree of oxidation measured by conductimetry titration was as high as 91.0%. The TEMPO-oxidized cellulose was soluble in water for valuable polyelectrolytes and intermediates.

Superhydrophobic magnetic poly(DOPAm-co-PFOEA)/Fe3O4/cellulose microspheres for stable liquid marbles.

Novel magnetic superhydrophobic cellulose-based microspheres were fabricated using poly(DOPAm-co-PFOEA), which provide remarkable stability to liquid marbles with various liquids for liquid droplet transportation and manipulation.

Synergistic effects of guanidine-grafted CMC on enhancing antimicrobial activity and dry strength of paper.

In order to improve the strength property and antimicrobial activity of paper simultaneously, we prepared a novel multifunctional agent based on carboxymethyl cellulose (CMC) by a simple two-stage method. The first stage was the oxidation of CMC to obtain the dialdehyde CMC (DCMC), and the second stage was the graft of guanidine hydrochloride (GH) onto DCMC to obtain DCMC-GH polymer. The strength property and antimicrobial activity of DCMC-GH-coated copy paper have been studied by the tensile test and inhibition zone method, respectively. The results showed that the dry strength index could increase about 20% after the paper was coated with DCMC-GH. The coating of DCMC-GH on paper also resulted in excellent antimicrobial activities against Escherichia coli and Staphylococcus aureus, and the inhibition zone became larger as the GH content grafted on DCMC increased. The novel DCMC-GH polymer would be a multifunctional coating agent for food packaging paper.

Preparation of microfibrillated cellulose/chitosan-benzalkonium chloride biocomposite for enhancing antibacterium and strength of sodium alginate films.

The nonantibacterial and low strength properties of sodium alginate films negatively impact their application for food packaging. In order to improve these properties, a novel chitosan-benzalkonium chloride (C-BC) complex was prepared by ionic gelation using tripolyphosphate (TPP) as a coagulant, and a biocomposite obtained through the adsorption of C-BC complex on microfibrillated cellulose, MFC/C-BC, was then incorporated into a sodium alginate film. The TEM image showed that the C-BC nanoparticles were spherical in shape with a diameter of about 30 nm, and the adsorption equilibrium time of these nanoparticles on the surface of MFC was estimated to be 6 min under the driving forces of hydrogen bonds and electrostatic interactions. According to the disc diffusion method, the MFC/C-BC biocomposite-incorporated sodium alginate film exhibited remarkable antibacterial activity against Staphylococcus aureus and certain antibacterial activity against Escherichia coli . The strength tests indicated that the tensile strength of the composite sodium alginate film increased about 225% when the loading of MFC/C-BC biocomposite was 10 wt %. These results suggested that the MFC/C-BC biocomposite-incorporated sodium alginate film with excellent antibacterial and strength properties would be a promising material for food packaging, and the MFC/C-BC may also be a potential multifunctional biocomposite for other biodegradable materials.