Manipulating Crystal Growth and Secondary Phase PbI2 to Enable Efficient and Stable Perovskite Solar Cells with Natural Additives.

In perovskite solar cells (PSCs), the inherent defects of perovskite film and the random distribution of excess lead iodide (PbI2) prevent the improvement of efficiency and stability. Herein, natural cellulose is used as the raw material to design a series of cellulose derivatives for perovskite crystallization engineering. The cationic cellulose derivative C-Im-CN with cyano-imidazolium (Im-CN) cation and chloride anion prominently promotes the crystallization process, grain growth, and directional orientation of perovskite. Meanwhile, excess PbI2 is transferred to the surface of perovskite grains or formed plate-like crystallites in local domains. These effects result in suppressing defect formation, decreasing grain boundaries, enhancing carrier extraction, inhibiting non-radiative recombination, and dramatically prolonging carrier lifetimes. Thus, the PSCs exhibit a high power conversion efficiency of 24.71%. Moreover, C-Im-CN has multiple interaction sites and polymer skeleton, so the unencapsulated PSCs maintain above 91.3% of their initial efficiencies after 3000 h of continuous operation in a conventional air atmosphere and have good stability under high humidity conditions. The utilization of biopolymers with excellent structure-designability to manage the perovskite opens a state-of-the-art avenue for manufacturing and improving PSCs.

Strength and Microscopic Mechanism of Cement-Fly Ash-Slag-Desulfurization Gypsum Solidified Mica Schist Weathered Soil.

Mica schist weathered soil possesses a number of poor engineering characteristics, which make it difficult to use as a subgrade material for resource utilization. Therefore, in this study, a new type of curing agent, CFSD (cement-fly ash-slag-desulfurized gypsum), is proposed for this soil. The effects of different curing agent dosages, age of preservation, and confining pressure on the stress-strain curves were analyzed via the uniaxial compression test and triaxial compression test, while the micromorphological characteristics of cured soil were analyzed via X-ray diffraction analysis and the SEM test combined with Image J software. In this paper, we also establish a microscopic mechanism model to determine how curing agents increase the strength of mica schists. The results reveal that the compressive strength of solidified soil increases rapidly within 28 days; the CFSD dosage of 4% at 7 d increased by 103.23% by 28 d. After 28 d, the trend of compressive strength growth was flat. The CFSD dosage of 4% at 7 d increased by 128.34% by 90 d; with the increase in the dosage, the curve transformed from flat to steep. These results suggest that the CFSD dosage is positively correlated with the damage strain and damage bias stress of solidified soil. The curves for the strain softening type with a 4% dosage as the initial effective confining pressure increased from 50 kPa to 300 kPa; the failure stress and failure strain increased by 202.09% and 90.85%, respectively. With the increase in curing agent dosage and maintenance age, the pore size of 2~5 µm, >5 µm interval decreased from 56.46% to 27.92%, the porosity decreased from 12.51% to 4.6%, and the hydrate produced by the curing agent cemented and filled up the pore space between the loose particles of the soil body. Thus, the large pore space became microporous, and the pore structure densification was greatly improved.

Damage Model of Steel Fiber-Reinforced Coal Gangue Concrete under Freeze-Thaw Cycles Based on Weibull Distribution.

In order to improve the utilization rate of coal gangue and expand the application range of coal gangue concrete (CGC), a certain proportion of steel fiber was added to the concrete, and the freeze-thaw cycles (FTCs) and flexural tests were used to explore the effects of different mass replacement rates of coal gangue (0%, 25%, 50%, 75%, and 100%) and different proportions of the volumetric blending of the steel fiber (0%, 0.8%, 1.0%, and 1.2%) on the frost resistance of steel fiber-reinforced CGC (SCGC). The governing laws of mass loss rate, relative dynamic elastic modulus and load-midspan deflection curve were obtained on the base of the analysis of testing results. The damage mechanisms of the SCGC under the FTCs were analyzed using the results of scanning electron microscopy (SEM). Based on the Lemaitre's strain equivalence principle and Krajcinovic's vector damage theory, a damage evolution model of the SCGC under the FTCs was established by introducing the damage variable of the SCGC satisfying Weibull distribution. The results show an increasing mass loss rate of the SCGC and a decreasing relative dynamic elastic modulus with an increasing mass replacement rate of coal gangue. The proper content of the steel fiber can reduce the mass loss rate of concrete by 10~40% and the relative loss rate of dynamic elastic modulus of concrete by 2~8%, thus significantly improving the ductility and toughness of the concrete. The established damage evolution model is well validated by the experimental results, which further help to improve the modelling accuracy. This study provides key experimental data and a theoretical basis for a wider range of proper utilization of coal gangue in cold regions.

Seashell-Inspired Switchable Waterborne Coatings with Complete Biodegradability, Intrinsic Flame-Retardance, and High Transparency.

Inspired by the "brick-and-mortar" structure and the whole lifecycle eco-friendliness of seashells, we have constructed a proof-of-concept and environmentally friendly coating with switchable aqueous processability, complete biodegradability, intrinsic flame retardance, and high transparency, via using natural biomass and montmorillonite (MMT). We first designed and synthesized cationic cellulose derivatives (CCD) as the macromolecular surfactants, which effectively exfoliated MMT to obtain nano-MMT/CCD aqueous dispersions. Subsequently, via a simple spray-coating process and a post-treatment process with a salt aqueous solution, the transparent, hydrophobic, and flame-retardant coating was fabricated with a "brick-and-mortar" structure. The resultant coating exhibited an extremely low peak heat release rate (PHRR) of only 17.3 W/g, which is 6.3% of cellulose PHRR. Moreover, it formed a lamellar and porous structure once ignited. Thus, this coating could effectively protect combustible materials from fire. In addition, the coating had a high transparency (>90%) in the range of 400-800 nm. After use, the water-resistant coating was converted into a water-soluble material by using a hydrophilic salt aqueous solution, which then could be easily removed by water. Furthermore, the CCD/nano-MMT coating was completely degradable and nontoxic. Such a switchable and multifunctional coating with whole lifecycle environmental-friendliness exhibits huge application potential.

Cellulose-Based Ultralong Room-Temperature Phosphorescence Nanomaterials with Tunable Color and High Quantum Yield via Nano-Surface Confining Effect.

How to achieve multicolor organic room-temperature phosphorescence (RTP) is still challenging and striking. Herein, we discovered a new principle to construct eco-friendly color-tunable RTP nanomaterials based on the nano-surface confining effect. Cellulose nanocrystal (CNC) immobilized cellulose derivatives (CX) containing aromatic substituents via hydrogen-bonding interactions, which effectively inhibit the motion of cellulose chains and luminescent groups to suppress the nonradiative transitions. Meanwhile, CNC with a strong hydrogen-bonding network can isolate oxygen. CX with different aromatic substituents regulate the phosphorescent emission. After mixing CNC and CX directly, a series of polychromatic ultralong RTP nanomaterials were obtained. The RTP emission of the resultant CX@CNC can be finely adjusted through the introduction of various CX and the regulation of the CX/CNC ratio. Such a universal, facile, and effective strategy can be used to fabricate various colorful RTP materials with wide color gamut. Because of the complete biodegradability of cellulose, the multicolor phosphorescent CX@CNC nanomaterials can be used as eco-friendly security inks to fabricate disposable anticounterfeiting labels and information-storage patterns via conventional printing and writing processes.

Immobilization of laccase on chitosan functionalized halloysite nanotubes for degradation of Bisphenol A in aqueous solution: degradation mechanism and mineralization pathway.

As a hazardous organic chemical raw material, Bisphenol A (BPA) has attracted a great deal of scientific and public attention. In this study, the chitosan functionalized halloysite nanotubes immobilized laccase (lac@CS-HNTs) was prepared by simultaneous adsorption-covalent binding method to remove BPA for the first time. We optimized the preparation of lac@CS-NHTs by controlling one-factor variable method and response surface methodology (RSM). The cubic polynomial regression model via Design-Expert 12 was developed to describe the optimal preparation conditions of immobilized laccase. Under the optimal conditions, lac@CS-NHTs obtained the maximum enzyme activity, and the enzyme loading was as high as 60.10 mg/g. The results of batch removal experiment of BPA showed that under the optimum treatment condition, the BPA removal rate of lac@CS-NHTs, FL and heat-inactivated lac@CS-NHTs was 87.31 %, 60.89 % and 24.54 %, respectively, which indicated that the contribution of biodegradation was greater than adsorption. In addition, the relative activity of lac@CS-NHTs dropped to about 44.24 % after 8 cycles of BPA removal, which demonstrated that lac@CS-NHTs have the potential to reduce costs in practical applications. Finally, the possible degradation mechanism and mineralization pathway of BPA were given via High-performance liquid chromatography (HPLC) analysis and gas chromatography-mass spectrometry (GC-MS) analysis.

Click Modification for Polysaccharides via Novel Tunnel Transmission Phenomenon in Ionic Liquids.

It is extremely difficult to achieve a rapid and efficient modification of natural polysaccharides, due to the intrinsic strong hydrogen bonding networks and the slow mass transfer process during the reaction process. Herein, we found a fascinating anion-tunnel transmission phenomenon in the imidazolium-based ionic liquids with carboxylate anions. A novel click esterification of natural polysaccharides thus was demonstrated under a catalyst-free condition within a very short reaction time of 15 min at 0-80°C. Such a super-rapid and highly efficient modification strategy is available for various polysaccharides (cellulose, starch, inulin, pullulan, dextran, and xylan), different esterification reactions (acetification, propionation, benzoylation, and cyclohexyl formylation), and high concentrations, claiming a revolutionary potential in polysaccharide chemistry industries.

Irreversible Humidity-Responsive Phosphorescence Materials from Cellulose for Advanced Anti-Counterfeiting and Environmental Monitoring.

Organic phosphorescence materials have many unique advantages, such as a large Stokes shift, high signal-to-noise ratio, and no interference from background fluorescence and scattered light. But, they generally lack responsiveness. Herein, we developed a new type of biopolymer-based phosphorescence materials with excellent processability and irreversible humidity-responsiveness, via introducing the imidazolium cation to cellulose chain. In the resultant cellulose derivatives, the imidazolium cation promotes the intersystem crossing, meanwhile the cation, chloride anion, and hydroxyl group form multiple hydrogen bonding interactions and electrostatic attraction interactions, which successfully inhibit the nonradiative transitions. As a result, the ionic cellulose derivatives exhibit green phosphorescence at room temperature and can be processed into phosphorescent films, coatings, and patterns. More interestingly, their phosphorescence emission changes when the different processing solvents are used. The ionic cellulose derivatives processed with acetone have a negligible phosphorescence, while they give an irreversible humidity-responsive phosphorescence, which means that the ionic cellulose derivatives processed with acetone exhibit significantly enhanced phosphorescence once they meet water vapor. Such novel irreversible responsive phosphorescence materials have huge potential in advanced anticounterfeiting, information encryption, molecular logic gates, smart tags, and process monitoring.

Super-rapid and highly-efficient esterification of cellulose to achieve an accurate chromatographic analysis of its molecular weight.

Herein, a striking anion-tunnel transfer effect was demonstrated in 1-butyl-3-methylimidazolium benzoate (BmimPhCOO) ionic liquid, so a rapid, mild and efficient benzoylation of cellulose is accomplished under catalyst-free condition in BmimPhCOO. In a wide temperature range of 20-80 °C, the equilibrium of reaction is reached within only 15 min, which is much faster than the reported acylation of cellulose. Furthermore, the resultant cellulose tribenzoates have excellent solubility in conventional organic solvents, thus they can be used to accurately reflect the molecular weight and dispersity index of cellulose raw materials by gel permeation chromatography. This method is suitable for various cellulose. Therefore, we found a new principle to realize the extremely-rapid acylation of cellulose, and proposed an effective approach to accurately determine the molecular weight parameters of cellulose.

Confronting the Challenge of Cellulose Molecular Weight Measurement: An Accurate, Rapid, and Universal Method with Ionic Liquid as an Additive.

Molecular weight parameters are the key fundamental information of polymer materials, but the accurate characterization of the molecular weight of cellulose is extremely difficult due to its strong hydrogen bonding network. Herein, we demonstrated two new methods to accurately and rapidly measure the molecular weight parameters of cellulose by using 1-butyl-3-methylimidazolium acetate (BmimAc) ionic liquid (IL) as an additive. Cellulose is rapidly dissolved in BmimAc/DMSO (1:1, w/w) at room temperature at first. Then, DMAc is added to dilute the solution, and finally, the molecular weight and molecular weight distribution of cellulose samples are measured by the gel permeation chromatography (GPC) method with BmimAc/DMSO/DMAc (1:1:18, w/w) as the mobile phase. Such a simple method is suitable to all kinds of cellulose samples and exhibits an extremely high analytical efficiency which is 50 times higher than the previous GPC methods. In addition, a viscosity method that is available for industrial application was proposed by using the BmimAc/DMSO/DMAc (1:1:8, w/w) system with low viscosity. The relationship between the intrinsic viscosity of the cellulose/BmimAc/DMSO/DMAc solution and the molecular weight of cellulose is well established and is applicable to cellulose samples of Mw = 4.5 × 104 to 1.8 × 106, which is the widest applicable range among the reported viscosity methods. Overall, two new methods based on the use of BmimAc as an additive have many advantages, such as wide applicable range, simple preparation process, mild dissolution condition, no degradation or aggregation of cellulose, high accuracy, fast detection, and low IL consumption, overcoming the existing problems in the traditional methods. It is expected to be used as a standard procedure to characterize the molecular weight of cellulose in academia and industries.

Ultralong phosphorescence cellulose with excellent anti-bacterial, water-resistant and ease-to-process performance.

Herein, we present a phosphorescent cationized cellulose derivative by simply introducing ionic structures, including cyanomethylimidazolium cations and chloride anions, into cellulose chains. The imidazolium cations with the cyano group and nitrogen element promote intersystem crossing. The cyano-containing cations, chloride anions and hydroxyl groups of cellulose form multiple hydrogen bonding interactions and electrostatic attraction interactions, effectively inhibiting the non-radiative transitions. The resultant cellulose-based RTP material is easily processed into phosphorescent films, fibers, coatings and patterns by using eco-friendly aqueous solution processing strategies. Furthermore, after we construct a cross-linking structure by adding a small amount of glutaraldehyde as the cross-linking agent, the as-fabricated phosphorescent patterns exhibit excellent antibacterial properties and water resistance. Therefore, considering the outstanding biodegradability and sustainability of cellulose materials, cellulose-based easy-to-process RTP materials can act as antibacterial, water-resistant, and eco-friendly phosphorescent patterns, coatings and bulk materials, which have enormous potential in advanced anti-counterfeiting, information encryption, disposable smart labels, etc.

The study of laccase immobilization optimization and stability improvement on CTAB-KOH modified biochar.

BACKGROUND: Although laccase has a good catalytic oxidation ability, free laccase shows a poor stability. Enzyme immobilization is a common method to improve enzyme stability and endow the enzyme with reusability. Adsorption is the simplest and common method. Modified biochar has attracted great attention due to its excellent performance. RESULTS: In this paper, cetyltrimethylammonium bromide (CTAB)-KOH modified biochar (CKMB) was used to immobilize laccase by adsorption method (laccase@CKMB). Based on the results of the single-factor experiments, the optimal loading conditions of laccase@CKMB were studied with the assistance of Design-Expert 12 and response surface methods. The predicted optimal experimental conditions were laccase dosage 1.78 mg/mL, pH 3.1 and 312 K. Under these conditions, the activity recovery of laccase@CKMB was the highest, reaching 61.78%. Then, the CKMB and laccase@CKMB were characterized by TGA, FT-IR, XRD, BET and SEM, and the results showed that laccase could be well immobilized on CKMB, the maximum enzyme loading could reach 57.5 mg/g. Compared to free laccase, the storage and pH stability of laccase@CKMB was improved greatly. The laccase@CKMB retained about 40% of relative activity (4 °C, 30 days) and more than 50% of relative activity at pH 2.0-6.0. In addition, the laccase@CKMB indicated the reusability up to 6 reaction cycles while retaining 45.1% of relative activity. Moreover, the thermal deactivation kinetic studies of laccase@CKMB showed a lower k value (0.00275 min- 1) and higher t1/2 values (252.0 min) than the k value (0.00573 min- 1) and t1/2 values (121.0 min) of free laccase. CONCLUSIONS: We explored scientific and reasonable immobilization conditions of laccase@CKMB, and the laccase@CKMB possessed relatively better stabilities, which gave the immobilization of laccase on this cheap and easily available carrier material the possibility of industrial applications.

Immobilization of Ionic Liquids with a New Cellulose Ester Containing Imidazolium Cation for High-Performance CO2 Separation Membranes.

CO2 gas separation is of significant importance to protect the environment and utilize the carbon resource. In this work, two kinds of new cellulose esters containing imidazolium cation, cellulose acetate (CA) 1-butyl-3-methylimidazolium chloride and CA 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (CA-BmimTf2 N), are designed and synthesized. The resultant cationized cellulose esters effectively lock various ionic liquids (ILs) via electrostatic interactions. Due to the strong attraction interactions, the obtained cellulose ester/ILs composite membranes are uniform, smooth, and highly transparent. Moreover, the added ILs with a long alkyl chain in the cation and a bis(trifluoromethane sulfonyl)imide anion remarkably improve the CO2 permeability of the cellulose ester/ILs membranes, because of the dramatic increase of the CO2 diffusion rate. The CA-BmimTf2 N/C10 mimTf2 N membranes exhibit the highest CO2 permeability, which is 3800% higher than that of CA membrane and 1700% higher than that of CA-BmimTf2 N membrane. More importantly, the CA-BmimTf2 N/C10 mimTf2 N membranes have good mechanical properties and thermal stability. Such high-performance CO2 separation membranes with high CO2 permeability, high transparency, and good mechanical property have a huge potential in the practical utilization for gas separation.