Fabrication of microfibrillated cellulose from biomass by use of carbon nitride with high nitrogen/carbon ratio.

Microfibrillated cellulose (MFC) as an attractive green bio-based material has attracted widespread attention in recent years due to its non-toxicity, degradability, excellent performance, and high aspect ratio. In this study, the g-C3N5 with a high nitrogen/carbon ratio was prepared as a catalyst through the self-polymerization of a nitrogen-rich precursor. The triazole groups at the edges of g-C3N5 were proven to exhibit strong adsorption to biomass and strong alkalinity. In a low-acidic aqueous system with g-C3N5, MFC with diameters of 100-200 nm and lengths up to 100 µm was fabricated from various biomasses within 5 min under microwave radiation. The ultimate yield of the MFC produced from viscose reached 90 %. Young's modulus of the MFC reaches 3.7 GPa. This work provides a particular method with high efficiency to prepare MFC with excellent properties from biomass by chemical method.

Fabrication of a Nanosized g-C3N4-Loaded Cellulose Microfiber Bundle to Induce Highly Efficient Water Treatment via Photodegradation .

Graphite carbon nitride (g-C3N4) with a suitable structure and strong amine activity is designed and prepared to serve as a hydrogen bond donor for the microfibrilization of corncob cellulose to form a cellulose microfiber (CMF) bundle. Simultaneously, well-dispersed nanosized g-C3N4 is loaded into the bundle to form a photocatalyst for efficient photodegradation of rhodamine B (Rh B) in water. Under the optimal preparation conditions at 165 °C, 10 min, and 0.08 mol/L H2SO4, the yield of g-C3N4-functionalized cellulose microfibers (CMF-g-C3N4) reaches to the highest over 70%. The catalytic rate of CMF-g-C3N4 is 3.3 times larger than that of pure g-C3N4. The degradation rate of Rh B is maintained at over 90% in 10 cycles of photocatalytic degradation. The obtained CMF-g-C3N4 also has good thermal stability and mechanical properties. This research suggests a particularly simple way to transform cellulose into a highly efficient photocatalyst for water treatment.

Cellulose-based fluorescent materials fabricated in CO2 switchable solvent for freshness monitoring.

Herein, a novel cellulose-based fluorescent material with amine-responsive property was developed in a CO2 switchable solvent for the contactless, real-time, and visual monitoring of the freshness of shrimp, crab, and fish. A nucleophilic cellulose carbonate intermediate is in-situ formed upon dissolution of cellulose in the CO2 switchable solvent, which is adopted for the highly effective grafting of poly(l-lactic acid) and amine-responsive fluorescent reagent 7-amino-4-(trifluoromethyl) coumarin onto the cellulose backbone via ring opening polymerization and nucleophilic substitution reaction, respectively. The product has good processibility, and sensitive and reversible fluorescent responsive towards ammonia. The fluorescent intensity of the material decreased significantly and its fluorescent color changed from blue to cyan, when the aquatic products got spoiled. This study indicates that the CO2 switchable solvent has great potential for the modification of cellulose with various functionality by taking advantage of the highly active nucleophilic cellulose carbonate intermediate.

Using Cellulose-graft-Poly(L-lactide) Copolymers as Effective Compatibilizers for the Preparation of Cellulose/Poly(L-lactide) Composites with Enhanced Interfacial Compatibility.

Cellulose-grafte-poly(L-lactide) (C-g-PLLA) copolymers synthesized in a CO2-switchable solvent are proposed for use as effective compatibilizers for the preparation of cellulose-PLLA composites with enhanced interfacial compatibility. The effect of the molar substitution (MSPLLA) of the grafted PLLA side chain in the C-g-PLLA copolymer and the feeding amount of this copolymer on the mechanical and thermal properties and hydrophilicity of the composites was investigated. The composites had a largely increased impact strength with the incorporation of the compatibilizer. With the increasing of MSPLLA and the feeding amount of the copolymer, the resulting composites had an increased impact strength. When 5 wt% C-g-PLLA with MSPLLA of 4.46 was used as a compatibilizer, the obtained composite containing 20 wt% cellulose presented an impact strength equal to that obtained for the neat PLLA. The composites had a slightly decreased melting temperature and thermal decomposition temperature, but increased hydrophilicity due to the incorporation of the compatibilizer. This work suggests an effective method to improve the interfacial compatibility between cellulose and PLLA for the fabrication of fully bio-based composites with high performance.

Dual modification of cellulose with esterification and carbonation in DMSO/DBU/CO2 system as fluorescent additive for pH detection.

An easy and effective way to synthesize dual-functionalized cellulose derivatives with processability and fluorescence functionality by one-pot modification of successive esterification and carbonation under mild condition is established with the use of DMSO/DBU/CO2 system. Accordingly, four kinds of dual-functionalized cellulose derivatives with rather good fluorescent response are obtained. After blending the synthesized dual-functionalized cellulose derivative with cellulose acetate as functional additive in solution, cast film with the elastic modulus, stress and strain reaches to 2.2 GPa, 34.1 MPa and 5.7% is prepared. Besides, the cast film also exhibits the ability to detect the pH value at 12-14 with detection accuracy of 0.4 through the change of fluorescent color. This research shows a simple but effective way to prepare dual-functionalized cellulose derivatives for the high-quality applications in field of detection.

Alendronate-Decorated Nanoparticles as Bone-Targeted Alendronate Carriers for Potential Osteoporosis Treatment.

Osteoporosis is a skeletal disorder characterized by a low bone mass and density. Alendronate (Alen), a second-generation bisphosphonate drug, was indicated as the first-line regimen for the treatment of osteoporosis. However, the use of Alen has been limited due to its low bioavailability and gastrointestinal side effects. Herein, Alen-decorated nanoparticles were prepared through ionic cross-linking between poly (lactic-co-glycolic acid), ß-cyclodextrin-modified chitosan (PLGA-CS-CD), and Alen-modified alginate (ALG-Alen) for Alen loading and bone-targeted delivery. Alen was selected as a therapeutic drug and a bone-targeting ligand. The nanoparticles have negatively charged surfaces, and sustained release of Alen from the nanoparticles can be observed. Cytotoxicity detected using cell counting kit-8 (CCK-8) assay and lactate dehydrogenase release test on MC3T3 cells showed that the nanoparticles had good cytocompatibility. A hemolysis test showed that the hemolysis ratios of nanoparticles were <5%, indicating that the nanoparticles had no significant hemolysis effect. Moreover, the Alen-decorated nanoparticles exhibited enhanced binding affinity to the hydroxyapatite (HAp) disks compared with that of nanoparticles without Alen modification. Thus, the Alen-decorated nanoparticles might be developed as promising bone-targeted carriers for the treatment of osteoporosis.

Utilization of Hydroxyl-Enriched Glucose-Based Carbonaceous Sphere (HEGCS) as a Catalytic Accelerator to Enhance the Hydrolysis of Cellulose to Sugar.

In this work, hydroxyl-enriched glucose-based carbonaceous sphere (HEGCS) is prepared by hydrothermal method as an accelerator to enhance the hydrolytic efficiency of the treated cellulose to sugar in low-acidic aqueous system under microwave radiation. Due to the strong affinity of HEGCS to cellulose, during the hydrolysis, the treated cellulose can be flaked into small fragments by HEGCS, which is like a "microball milling", and accordingly, the hydrolytic accessibility of cellulose is extremely improved. Highly efficient hydrolysis of cellulose to sugar is finally achieved in HEGCS containing 0.02 mol/L sulfuric acid. One hundred percent conversion of cellulose and 96.0 ± 4.0% total reducing sugar (TRS) yield was obtained within 15 min under microwave radiation. The average content of glucose in sugar products is over 70%. Our research not only obtains a catalytic accelerator to establish an effective method for hydrolyzing treated cellulose to sugar but also provides the idea for regulating cellulose accessibility during hydrolysis to achieve high efficiency in the hydrolysis of cellulose.

Highly efficient microwave driven assisted hydrolysis of cellulose to sugar with the utilization of ZrO2 to inhibit recrystallization of cellulose.

Following the main idea of a two-step method, microcrystalline cellulose is firstly pretreated to prepare regenerated cellulose (RC) with low crystallinity. Then, RC is continuously hydrolyzed to sugar in aqueous system by microwave driving. With the establishment of ZrO2 contained low acid catalytic system, an advanced route driven by microwave radiation to induce highly efficient hydrolysis of RC to sugar is formed. Due to the effect of ZrO2 on the molecular chain of cellulose, the recrystallization of RC is obviously weakened, and higher hydrolysis reactivity is achieved. Under the optimal conditions, the average conversion of RC and the yield of total reducing sugar highly reach 98.4 ±â€¯0.5% and 97.9 ±â€¯0.6%, respectively. The result is extremely superior to the efficiency of hydrolysis initiated only by pure acid. As a result, a novel and simple thinking to establish an advanced two-step methodology to hydrolyze cellulose to sugar with high efficiency is achieved.

Revealing the importance of non-thermal effect to strengthen hydrolysis of cellulose by synchronous cooling assisted microwave driving.

Non-thermal effect of microwave is precisely revealed as an important factor to strengthen the hydrolysis of cellulose to sugar by a new method of synchronous cooling assisted microwave driving. Using this particular method, the thermal effect is mandatorily removed from the hydrolysis of cellulose. After systematic analysis of the hydrolysis of low crystalline regenerated cellulose (RC), the non-thermal effect of microwave is proved to strengthen hydrolysis. The enhancement of non-thermal effect effectively weaken the interaction between the hydroxyl groups of -O(2)H and -O(6)H, as well as strengthen interaction between the hydroxyl groups of -O(3)H and -O(5)H within one single molecular chain. It leads to the reduction of regularity of molecular chain and thus inhibits the recrystallization of RC. As a result, the efficiency of hydrolysis is greatly improved. This research provides an important theoretical support and technical guidance to construct new microwave driven hydrolysis with high efficiency in the future.

Hydrolysis behavior of regenerated celluloses with different degree of polymerization under microwave radiation.

This work studied the hydrolysis behavior of regenerated celluloses (RCs) with different degree of polymerization (DP) by using the catalyst of dilute acid under microwave radiation. Results showed that the DP had a considerable influence on hydrolysis of cellulose. The reactivity of RCs was significantly improved when DP was lower than 51. The highest sugar yield of 59.2% was achieved from RC with lowest DP of 23 at 160 °C for 15 min. But the lowest yield of 32.6% was obtained when RC with highest DP of 132 was used. Recrystallization of cellulose was found to hinder the further hydrolysis particularly with the high DP. The effect of recrystallization can be reduced by the decrease of DP of RCs. This research demonstrates that the DP of RCs plays a crucial role on hydrolysis and it provides a preliminary guide based on DP to find a suitable pretreatment method for cellulose hydrolysis.

Activation of corn cellulose with alcohols to improve its dissolvability in fabricating ultrafine fibers via electrospinning.

Water and four small molecular alcohols are respectively used to activate corn cellulose (CN cellulose) with the aim to improve the dissolvability in DMAc/LiCl. Among all these activated agents, monohydric alcohols are found to produce the optimal effect of activation in the whole process including of activating, dissolving, and electrospinning of CN cellulose. Meanwhile, well distributed fibers with the diameter of 500nm-2µm are fabricated in electrospinning. Understanding the activation effect of monohydric alcohols with water and polyhydric alcohols, the most effective activated agent is ascertained with the characteristics of small molecular size, low viscosity, and single functionality. This work is definitely initiated to understand the critical principle of CN cellulose in dissolving. Accordingly, a feasible methodology is also established to prepare ultrafine cellulose fibers with good morphology in electrospinning.

Responsive behavior of regenerated cellulose in hydrolysis under microwave radiation.

This work studied the responsive behavior of regenerated cellulose (RC) in hydrolysis under microwave radiation. Four types of RC with different crystallinity (Cr) and degree of polymerization (DP) are produced to evaluate the reactivity of RC by step-by-step hydrolysis. Results show Cr is the key factor to affect the reactivity of RCs. With hydrolysis of amorphous region and the formation of recrystallization, the Cr of RC reaches a high value and thus weakens the reactivity. As a result, the increment of cellulose conversion and sugar yield gradually reduces. Decrease of the DP of RC is helpful to increase the speed at the onset of hydrolysis and produce high sugar yield. But, there is no direct influence with the reactivity of RC to prolong the time of pretreatment. This research provides an accurate understanding to guide the RC preparation for sugar formation with relative high efficiency under mild reaction conditions.

A novel facile two-step method for producing glucose from cellulose.

A two-step acid-catalyzed hydrolysis methodology is established to effectively hydrolyze cellulose to glucose with high yield and selectivity under mild conditions. In multi-steps hydrolysis, the difficulty of cellulose can be effectively reduced under mild conditions. In the first step, microcrystalline cellulose was depolymerized in phosphoric acid to cellulose oligomer at 50°C. Then the oligomer was precipitated by ethanol and hydrolyzed with dilute sulfuric acid in the second step. 87.7% total reducing sugars and 57.8% glucose was released from the two-step hydrolysis process. In addition, with the assistance of microwave in the second step, the yield and selectivity of glucose can be improved to 73.3% and 80.1% by only 5 min hydrolysis. The two-step hydrolysis exhibits an effective process to produce glucose in cellulose hydrolysis. The enhancement of hydrolysis reactivity is considered to be controlled with the decrease of crystallinity and degree of depolymerization of cellulose.

Measurement of adhesion work of electrospun polymer membrane by shaft-loaded blister test.

The work of adhesion at the interface of electrospun membrane and rigid substrate is measured by a shaft-loaded blister test (SLBT). Poly(vinylidene fluoride) (PVDF) were electrospun with an average fiber diameter of 333 ± 59 nm. Commercial cardboard with inorganic coating was used to provide a model substrate for adhesion tests. In SLBT, the elastic response PVDF was analyzed and its adhesion energy measured. The average value of the adhesion work is 206 ± 26 mJ/m(2). Elastic modulus of electrospun membrane obtained by SLBT is found to be 23.42 ± 2.69 MPa, which is consistent with the value obtained from standard tensile tests. The results show SLBT presented a viable methodology for evaluating the adhesion energy of electrospun polymer fabrics.