Rapid Construction of Vinyl Indomorphans by Rhenium Catalysis.

Here, an efficient route for accessing the vinylindomorphan skeleton is achieved by rhenium(I) catalysis. This transformation involves the condensation of indoles and alkyne-linked cyclohexanones, followed by intramolecular annulation to build the [3.3.1] bicyclic structure. This protocol complements the synthesis of the structurally complex heterocycles bearing a vinyl indole moiety. In addition, the selected products exhibited moderate cytotoxicity toward human A549 cells.

Valorization of Boehmeria nivea stalk towards multipurpose fractionation: furfural, pulp, and phenolic monomers.

BACKGROUND: As one of the most abundant bioresource in nature, the value-added utilization of lignocellulosic biomass is limited due to its inherent stubbornness. Pretreatment is a necessary step to break down the recalcitrance of cell walls and achieve an efficient separation of three main components (cellulose, hemicelluloses, and lignin). RESULTS: In this study, hemicelluloses and lignin in Boehmeria nivea stalks were selectively extracted with a recyclable acid hydrotrope, an aqueous solution of P-toluenesulfonic acid (p-TsOH). 79.86% of hemicelluloses and 90.24% of lignin were removed under a mild pretreatment condition, C80T80t20, (acid concentration of 80 wt%, pretreatment temperature and time of 80 °C and 20 min, respectively). After ultrasonic treatment for 10 s, the residual cellulose-rich solid was directly converted into pulp. Subsequently, the latter was utilized to produce paper via mixing with softwood pulp. The prepared handsheets with a pulp addition of 15 wt% displayed higher tear strength (8.31 mN m2/g) and tensile strength (8.03 Nm/g) than that of pure softwood pulp. What's more, the hydrolysates of hemicelluloses and the extracted lignin were transformed to furfural and phenolic monomers with yields of 54.67% and 65.3%, respectively. CONCLUSIONS: The lignocellulosic biomass, Boehmeria nivea stalks, were valorized to pulp, furfural, and phenolic monomers, successfully. And a potential solution of comprehensive utilization of Boehmeria nivea stalks was provided in this paper.

pH-Triggered Charge Reversible Fluorescent Probe for Simultaneous Imaging of Lipid Droplets and Nucleoli in Living Cells.

Cooperation between organelles is essential to maintain the normal functions of cells. Lipid droplets (LDs) and nucleoli, as important organelles, play an important role in the normal activities of cells. However, due to the lack of appropriate tools, in situ observation of the interaction between them has been rarely reported. In this work, taking into full consideration the pH and charge differences between LDs and nucleoli, a pH-triggered charge reversible fluorescent probe (LD-Nu) was constructed based on a cyclization-ring-opening mechanism. The in vitro pH titration experiment and 1H NMR showed that LD-Nu gradually transferred from the charged form to the electroneutral form with the increase of pH, and thus, the conjugate plane was reduced and its fluorescence blue-shifted. Most importantly, the physical contact between LDs and nucleoli was visualized for the first time. Meanwhile, the relationship between LDs and nucleoli was also further investigated, and the results showed that their interaction was more liable to be affected by the abnormality of LDs than those of nucleoli. Moreover, the cell imaging results displayed that the LDs both in the cytoplasm and nucleus were observed using the probe LD-Nu, and interestingly, the LDs in the cytoplasm were more susceptible to external stimuli than those in the nucleus. In a word, the probe LD-Nu can serve as a powerful tool for further exploration of the interaction mechanism between LDs and nucleoli in living cells.

A Skin-Inspired Design Integrating Mechano-Chemical-Thermal Robustness into Superhydrophobic Coatings.

Designing scalable coatings with a wide spectrum of functions such as liquid repellency, anticorrosion, and antiflaming and a high level of mechano-chemical-thermal robustness is crucial in real-life applications. However, these individual functionalities and robustness are coupled together or even have conflicting requirements on the interfacial or bulky properties of materials, and thus, simultaneously integrating all these individual features into one coating has proved challenging. Herein, an integral skin-inspired triple-layered coating (STC) that resolves conflicting demands imposed by individual features on the structural, chemical, mechanical, and thermal properties of materials is proposed. Specifically, the rational design of multiple gradients in roughness, wetting, strength, and flame retardancy and the formation of continuous interfaces along its triple layers endow a sustained liquid repellency, anticorrosion, and flame retardancy even under harsh environments, as well as strong antiabrasion on surfaces and adhesion with the substrate. Such an all-in-one design enhances the durability and lifetime of coatings and reduces the maintenance and repair, thereby contributing to cost and energy saving. Together with a facile spraying fabrication process, this STC provides a feasible and sustainable strategy for constructing energy and resource-saving materials.

A hydrotrope pretreatment for stabilized lignin extraction and high titer ethanol production.

The biomass pretreatment strategies using organic acids facilitate lignin removal and enhance the enzymatic digestion of cellulose. However, lignin always suffers a severe and irreversible condensation. The newly generated C-C bonds dramatically affect its further upgrading. In this study, we used a recyclable hydrotrope (p-Toluenessulfonic acid, p-TsOH) to dissolve lignin under mild condition and stabilized lignin with a quenching agent (formaldehyde, FA) during extraction, achieving both value-added lignin extraction and efficient enzymatic saccharification of cellulose. Approximately 63.7% of lignin was dissolved by 80% (wt. %) p-TsOH with 1.5% FA addition at 80 °C, 30 min. The obtained lignin was characterized by FTIR spectroscopy, TGA, 2D HSQC NMR spectroscopy, and GPC. The results indicated that the extracted lignin exhibited excellent properties, such as light color, a low molecular weight (Mw, 5371 g/mol), and a narrow polydispersity (Mw/Mn, 1.63). The pretreated substrate was converted to ethanol via a quasi-simultaneous saccharification and fermentation process (Q-SSF). After fermentation of 60 h, the ethanol concentration reached 38.7 ± 3.3 g/L which was equivalent to a theoretical ethanol yield of 82.9 ± 2.2% based on the glucan content, while the residual glucose concentration was only 4.69 ± 1.4 g/L. In short, this pretreatment strategy protected lignin to form new C-C linkages and improved the enzymatic saccharification of glucan for high-titer ethanol production.

Enhanced photostability of aggregation induced emission by hydrophobic groups.

Since the aggregation induced emission (AIE) phenomenon was reported, many research groups have used this unique AIE effect to develop chemo- or bio-sensors for detecting ions, gases, explosives, proteins, and enzymes. Most of these sensors work in their aggregate state, therefore, fluorescence stability has become one of the important problem, and unfortunately, as far as we know, there is no paper to discuss what factors can improve the fluorescence stability of AIE compounds in the aggregate state, if the fluorescence stability of the sensors are poor, there will seriously affect the detection result. In this article, we found that compounds with hydrophobic long alkyl substituents can maintain stable fluorescence intensity for a long time in the aggregate state. In addition, cyclohexane is introduced as a hydrophobic substituent. Therefore, the fluorescence stability of the aggregates also increased by 90% within 1800s. The aggregation solutions of CB-3 and CSB-2 were left for two weeks, and no significant changes were found in the fluorescence intensity. Molecular dynamics simulation (MDS) shows that the presence of hydrophobic substituents in compounds cause the molecules to be closely interspersed with each other, hence, making it difficult to change the optical properties, microstructure and stacking mode of the AIE aggregates by external stimulations. The introduction of hydrophobic substituents improves the fluorescence stability of AIE compounds, and makes the AIE phenomenon more valuable in the fields of biological/chemical sensing and imaging.

Biomass-based superhydrophobic coating with tunable colors and excellent robustness.

Multicolored superhydrophobic coating with high durability has been receiving tremendous attention in decorative applications. Herein, a facile method to fabricate multicolored superhydrophobic coating with excellent robustness has been developed by using cellulose and chitosan. The multicolored coatings can be obtained through single dyeing or mixed dyeing based on three primary dyes. The coating can be applied on hard substrates (e.g. glass, aluminum sheet) and soft substrates (e.g. cotton fabric) by diverse methods including spraying, dip-coating and painting. The colorful coating firmly adheres to the substrates due to the multiple interactions (siloxane covalent bonds and hydrogen bonds). The colorful coating exhibits water-repellant behaviors and can withstand sandpaper abrasion, tape-peeling cycles, water impact, salt spray test and UV environments. Furthermore, the multicolored coating can be used as a new type of pigment for painting on different substrates and is expected to have a huge potential application in technological design or decoration.

Tunable Electric and Magnetic Properties of Transition Metal@Nx Cy -Graphene Materials by Different Metal and Defect Types.

Transition metal@Nx Cy -graphene (TM@Nx Cy -GR) materials have been widely used as redox reaction catalysts in the field of fuel cells due to their low cost and high performance. In the present work, we systematically investigate the effect of different metal and defect types on the electro-magnetic properties of TM@Nx Cy -GR materials using first principles calculations. Our simulations show that TM@N3 -GR (the minimum defect size) and TM@N7 -GR (the maximum defect size) materials always possess metallic property regardless the metal type. However, doping different TM can regulate the medium defects (TM@N2 C2 -GR-I and TM@N2 C2 -GR-II) among metallicity, half-metallicity and semi-conductivity. In addition, we found that different TM and defect type largely affects the magnetic moment. The spin density and projected density of state calculations show that the net charges of the defect structure are mainly located near the hole, and the magnetic regulation comes from the coupling of TM-d orbital with carbon (nitrogen)-s(p) orbitals. The present study provides abundant valuable information for the TM@Nx Cy -GR materials designs and applicants in the future.

Charge-Dependent Strategy Enables a Single Fluorescent Probe to Study the Interaction Relationship between Mitochondria and Lipid Droplets.

Cooperation between organelles is essential to maintain the normal operation of the cell. A lipid droplet (LD), a dynamic organelle, is specialized in lipid storage and can interact physically with mitochondria in several cell types. However, an appropriate method for in situ studying the interaction relationships of mitochondria-LDs is still lacking. Herein, a charge-dependent strategy is proposed for the first time by considering adequately the charge difference between mitochondria and LDs. According to the novel strategy, we have developed a unique fluorescent probe Mito-LD based on the cyclization and ring-opening conversion. Mito-LD could simultaneously stain mitochondria and LDs and emit a red and green fluorescence, respectively. More importantly, with the probe Mito-LD, the in situ interaction relationships of mitochondria-LDs were investigated in detail from LD accumulation, mitochondrial dysfunction, lower environmental temperatures, and four aspects of apoptosis. The experimental results showed that mitochondria played an important role in LD accumulation, and the numbers and size of LDs would increase after mitochondrial dysfunction that may be due to excess liposomes. In addition, as an energy storage organelle, LDs played an important role in helping to coordinate mitochondrial energy supply in response to cold. In addition, the Mito-LD revealed that the polarity of mitochondria was higher than that of LDs. In a word, the probe Mito-LD could serve as a potential tool for further exploring mitochondria-LD interaction mechanisms, and importantly, the charge-dependent strategy is valuable for designing robust new probes in imaging multiple organelles.

New barbituric acid derivatives for data encryption and decryption based on the mechanochromic fluorescence effect.

Two barbituric acid derivatives CB-Ph and CB-Me were synthesized, both of which show a strong aggregation induced emission (AIE) effect. It was found that these two compounds show almost the same absorption and emission spectra. As a result, they show the same yellow color in daylight and the same yellow-green color under UV at 365 nm. Upon grinding, CB-Ph exhibits superior mechanochromic fluorescence (MCF) properties, with its fluorescence color from yellow-green (555 nm) to brown (580 nm) and its emission intensity decreases by 93%. However, neither the fluorescence peak wavelength nor the intensity of CB-Me shows observable changes after being ground, indicating no MCF effect. The X-ray diffraction (XRD) data indicate that the CB-Ph powder changes from the crystalline to amorphous state after being ground, whereas CB-Me remains in its crystalline state. Molecular dynamics simulation (MDS) shows that CB-Ph takes a 3D conformation due to three phenyl groups on the periphery of the molecule, which hinders the molecules from aggregating closely and results in the change of the microstructure by external force stimuli. However, CB-Me aggregated more closely due to its better planarity and hydrophobic n-hexane group, which make it difficult to change the microstructure upon being ground. Based on the unique optical properties of CB-Ph and CB-Me, a new data encryption-decryption technology is developed. CB-Ph is used as cryptographic ink due to its excellent MCF effect upon grinding. CB-Me is used as a camouflage material as it shows the same color as CB-Ph in the daylight and under UV-365 nm; furthermore, its colors remain unchanged after being ground.

A novel TiO2@stearic acid/chitosan coating with reversible wettability for controllable oil/water and emulsions separation.

Intelligent responsive materials with switchable wettability surfaces are of great importance in the field of oil/water separation. Here, a distinctive pH-responsive bio-based oil/water separation material was prepared. A low-cost titanium dioxide (TiO2) and environmentally friendly chitosan (CS) were used to combine with stearic acid (SA) to form the superhydrophobic TiO2@SA/CS coating. The coated materials (cotton fabric, sponge and filter paper) can be converted from superhydrophobicity to superhydrophilicity under ammonia treatment, and the superhydrophobicity can be restored again after heating treatment. The stimuli-responsive surface of the material was applied for the separation of oil/water/oil ternary mixtures and for the effective separation of various surfactant-stabilized water-in-oil emulsions and oil-in-water emulsions before and after wettability conversion. These results may provide a new prospect for the development of intelligent responsive oil/water separation materials with controllable wettability.

Multi-purpose barbituric acid derivatives with aggregation induced emission.

Three D-π-A barbituric acid derivatives with simple structure and intramolecular charge transfer (ICT) mechanisms were synthesized. Molecular dynamics simulations have successfully explained that CB-1 exhibits the best aggregate induced emission (AIE) activity due to the electron-deficient barbituric acid and the electron-rich carbazole exhibit a conformation which similar to π-π stacking, resulting in a strong electrostatic attraction between the molecules, meanwhile the N-atom substituent of the carbazole is n-propane plays a hydrophobic role. At the same time, barbituric acid derivatives also have mechanochromic fluorescent properties. In addition, CB-1 and CB-3 exhibited outstanding fluorescence stability than CB-2 in aggregation state which can be used to detect nitroaromatic explosives in aqueous media. The Stern-Volmer quenching constant (Ksv) of CB-1 and CB-3 is 6.6 × 104 and 1 × 105 M-1, respectively.

Detection of nitroaromatics based on aggregation induced emission of barbituric acid derivatives.

Barbituric acid derivatives with typical aggregation induced emission (AIE) are reported. Their emission wavelengths varied with water fraction of their solution. UV-visible absorption spectroscopy and theoretical calculations revealed the intramolecular charge transfer (ICT) possibility from donor to acceptor and the mechanism was confirmed as a restriction of intramolecular motion (RIM). The AIE properties were affected by the different substituents on barbituric acid. When the molecular volume increased, the AIE effect decreased. Fluorescent quenching mechanism was applied to detect nitroaromatic explosives. For 2,4,6-trinitrophenol (PA), one of the derivatives 5-(4-diphenylamino styrene)-1,3-diphenyl-barbituric acid in THF/H2O mixture (1:9, v/v), showed amplified fluorescence quenching with a maximum Stern-Volmer quenching constant of 4.1 × 104 M-1. The solid phase paper test based on 5-(4-diphenylamino styrene)-1,3-diphenyl-barbituric acid also showed a superior sensitivity toward PA both in vapor and solution.

Preparation and physicochemistry properties of smart edible films based on gelatin-starch nanoparticles.

BACKGROUND: Among the natural polymers able to form edible films, starch and gelatin (Gel) are potential sources. Corn starch is a polysaccharide widely produced around the world, and gelatin differs from other hydrocolloids as a fully digestible protein, containing nearly all the essential amino acids, except tryptophan. Based on this, with advantages such as abundance, relatively low cost, biodegradability, and edibility, studies considering alternative systems for food protection that utilize biopolymers have increased significantly in recent years. RESULTS: A novel macromolecular crosslinker starch-BTCAD-NHS (starch-butanetetracarboxylic acid dianhydride-N-hydroxysuccinimide, SBN) was successfully prepared to modify gelatin film. Compared with the blank gelatin films, the resulting SBN-Gel films exhibited improved surface hydrophobicity, higher tense strength and elongation-at-break, lower Young's modulus values, greater opacity, poorer water vapour uptake properties and better anti-degradation capacity. CONCLUSION: The modified gelatin film material with advanced properties obtained in this work was safe, stable eco-friendly and biorefractory, and was an ideal choice to form packaging in the food industry. Also, the crosslinking SBN-Gel coating was effective in reducing corruption and extending the shelf life of peeled apple substantially. © 2018 Society of Chemical Industry.

Cellulose-based film modified by succinic anhydride for the controlled release of domperidone.

Succinic anhydride (SAD) modified microcrystalline cellulose (MCC) films was prepared and used for the controlled release of the drug domperidone (dom). The morphology and chemical structure of the modified materials were characterized by SEM, FTIR, XRD and TG/DSC techniques. The physical properties, such as water uptake and swelling, light barrier properties, mechanical testing, in vitro degradation behavior, have been investigated. Results showed that the modified cellulose membranes exhibited good anti-UV properties, higher water uptake values, improved mechanical capacity and anti-biodegradability. In addition, the modified MCC films (MS) as the drug carrier indicated the controlled release of domperidone and the release mechanism was proposed using Korsmeyer-Peppas equation at pH 7.4. The developed drug delivery system possessed the profound significance in improving pharmacodynamics and bioavailability of drugs.

Evaluation of nitriloacetic acid modified cellulose film on adsorption of methylene blue.

A novel composite film (MCαN) based on microcrystalline cellulose (MCC) and nitrilotriacetic acid anhydride (NTAA) was prepared via casting method for the adsorption of methylene blue (MB) from aqueous solution. FT-IR, XRD, elemental analysis and TGA analysis demonstrated the success of modification. The swelling behavior, mechanical properties and MB adsorption performance of the modified MCαN films were improved obviously. The recycling study illustrated that MC2N film could be recycled and exhibited constant adsorption performance for five successful runs. In addition, mechanism study found that adsorption behavior of the composite films was better consistent with the pseudo-second order kinetic model and the Langmuir model. All the results suggested that the MCαN films could be considered as a promising candidate for dye wastewater treatment.

New starch ester/gelatin based films: Developed and physicochemical characterization.

A new starch-based ester Starch-EDTAD-NHS (SEN) was successful prepared firstly and used to modify gelatin films by amidation. 1H NMR, FTIR spectra, XRD curves, elemental analysis and Van Slyke method verified the synthesis and confirmed the crosslinking procedure. The properties of the composite SEN-Gel film, such as mechanical test, surface hydrophobicity, light barrier performance, water uptake studies, morphology and solubility behavior were studied. The results of water contact angle showed the hydrophobicity of the films, and the obtained transparency values indicated that the films were opaque. Finally, the modified films with better surface hydrophobicity, more flexible and pliable, improved light barrier performances and low solubility were obtained. All the results above illustrated that the composite films obtained in this work maybe have potential applications in many fields.

Honeycomb structural composite polymer network of gelatin and functional cellulose ester for controlled release of omeprazole.

The functionalized cellulose ester MCN was firstly synthesized and used to cross-link gelatin by amidation between -NH2 in gelatin and active ester groups in MCN to form a composite polymer network Gel-MCN, which was confirmed by Van Slyke method, FTIR, XRD and TGA-DTG spectra. The model drug omeprazole was loaded in Gel-MCN composites mainly by electrostatic interaction and hydrogen bonds, which were certified by FTIR, XRD and TGA-DSC. Thermal stability, anti-biodegradability, mechanical property and surface hydrophobicity of the composites with different cross-linking extents and drug loading were systematically investigated. SEM images demonstrated the honeycomb structural cells of cross-linked gelatin networks and this ensured drug entrapment. The drug release mechanism was dominated by a combined effect of diffusion and degradation, and the release rate decreased with cross-linking degree increased. The developed drug delivery system had profound significance in improving pesticide effect and bioavailability of drugs.

Eco-friendly biorefractory films of gelatin and TEMPO-oxidized cellulose ester for food packaging application.

BACKGROUND: In recent years, many types of food-packaging films and composites have been prepared using gelatin because of its good film-forming ability, non-toxic nature and cost-effectiveness. However, the relatively weak thermal stability, poor mechanical properties and easily-degradable quality limit the potential application of gelatin as a practical material. Microcrystalline cellulose (MCC), which comprises one of the most abundant biomass resources, has been regarded as a safe and reliable food additive because it has the same ingredients as the cellulose in people's daily intake. Food-packaging films with the excellent properties provided by gelatin and oxidized-cellulose represent a topic of great interest. RESULTS: MCC was modified by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation and chosen as the base of the macromolecule cross-linker (TMN). After modification of gelatin film by TMN, the minimum amount of free -NH2 in solution was 4.8 × 10-4 mol g-1 ). The thermal property obviously increased (from 322.31 o C to 352.63 o C) and was crucial for usage in the food industry. The highest water contact value 123.09° (η = 25%) indicated a better surface hydrophobicity. The higher Eab (58.88%) and lower Em (77.16%) demonstrated that a more flexible and shatter-proof material was obtained. Water vapor uptake studies suggested increased moisture absorption and greater swelling ability. CONCLUSION: The film material obtained in the present study was safe, stable, eco-friendly and biorefractory and could also be decomposed completely by the environment after disposal as a result of the properties of the ingredients gelatin and cellulose. The incorporation of a cellulosic cross-linker to gelatin-based films was an ideal choice with respect to developing a packaging for the food industry. © 2016 Society of Chemical Industry.

Preparation and antibacterial properties of gelatin grafted with an epoxy silicone quaternary ammonium salt.

Gelatin (GE) was modified with epoxy silicone quaternary ammonium salt (EPSiQA) under alkaline conditions (pH 10-11). Silyl and quaternary ammonium groups were linked to gelatin skeleton simultaneously. It was illustrated by XRD and DSC that the short-range order of GE is destroyed and the glass transition temperature (Tg) of GE drops 10 °C after modification. The measured contact angles and surface free energy calculated by Owens-Wendt equation showed that the surface energy of modified gelatin EPSiQA-GE is mainly contributed by the dispersive component of non-polarity silicone groups, the hydrophobility of EPSiQA-GE increases with the increase of grafted silicone units in gelatin. The results of minimum inhibitory concentration indicated that EPSiQA-GE has bactericidal property against Gram-positive bacteria, Gram-negative bacteria and has no antibacterial effect on mold.