Search

A novel type of functional graphene oxide nanosheets (GNs) modified with β-cyclodextrins (β-CDs) have been developed by coating dopamine-functionalized cyclodextrin (DACD) molecules on GNs for removing Bisphenol A (BPA) molecules from water. The DACD molecules with both β-CD groups for achieving adsorption property and dopamine (DA) groups for achieving adhesion property are synthesized by grafting DA onto carboxymethyl-β-cyclodextrin (CmβCD). The proposed DACD molecules can be firmly coated on the surfaces of various inorganic and organic substrates. Due to the large specific surface area of GNs, DACD-coated GNs (DACD@GNs) are proposed for efficient adsorption separation of BPA molecules from water. Due to the host-gust complexation between the BPA molecules in water and β-CDs on DACD@GNs, the fabricated DACD@GNs exhibit excellent adsorption performances. The adsorption kinetics can be explained via the pseudo-second-order model effectively. The experimental adsorption capacity of DACD@GNs is 11.29 mg·g−1 for BPA. Furthermore, after the adsorption process, the DACD@GNs can be easily separated from aqueous solutions via vacuum filtration with porous membranes, and then regenerated by simply washing with ethanol. The proposed strategy in this study can be used for effectively functionalizing the surfaces of various substrates with functional β-CDs, which is highly promising in applications in the field of adsorption separations, especially water treatments.

An unprecedented 19-membered allenic macrolide archangiumide (1) was discovered from the myxobacterium Archangium violaceum SDU8 by integrating NMR-based metabolic profiling and genome mining. Its biosynthesis pathway was proposed based on the architectural analysis of the encoding trans-AT PKS genes and validated by isotope labeling. The methodology of combing 2D NMR-based metabolic profiling and bioinformatics-aided structure prediction, as exemplified by this study, is anticipated to improve discovery efficiency of a broader range of microbial "dark matter".

Graphene oxide (GO) membranes have shown enormous promise in desalination and molecular/ionic sieving. However, the instability of GO membranes in aqueous solutions seriously hinders their practical applications. Herein, we report a novel and simple strategy to fabricate stable GO membranes in water-based environments through the insertion of various metal cations from metal foils (e.g., copper (Cu), iron (Fe), nickel (Ni), and zinc (Zn) foils) and natural deposition. Based on the cation-π, coordination, and electrostatic interaction between metal cations and GO nanosheets, the aqueous stability and mechanical strength of the membranes are significantly improved. The permeation rates for acetone, toluene, and p-xylene molecules across the GO membrane cross-linked by copper ions with a deposition time of 24 h are 0.966, 0.074, and 0.100 mol m-2 h-1, respectively. Moreover, this membrane displays excellent separation performance, and the separation factor of K+/Mg2+ is up to 68.8 in mono-/multivalent metal cation sieving, which indicate the effective molecular/ionic sieving performance. Meanwhile, the ionic sieving of the GO membrane cross-linked by copper ions has excellent repeatability and long-term stability. The versatility of this natural deposition strategy to fabricate GO membranes cross-linked by metal cations is investigated by using Fe foil, Zn foil, and Ni foil as well as other porous substrates such as polyvinylidene fluoride (PVDF), polyethersulfone (PES), and nylon membranes and filter paper. This fabrication strategy also enables low-cost preparation of large-area GO membranes. Therefore, GO membranes cross-linked by metal cations and prepared by this simple metal cation incorporation strategy have large potential application for molecular/ionic sieving in various solution systems.

A novel type of hybrid graphene oxide/laponite (GO/L) layered membrane is developed with stable two-dimensional (2D) nanochannels for efficient separations in aqueous environments. The electrostati...

The electronic and optical properties of graphane, silicane and MoS2 bilayers, as well as the graphane/MoS2 and silicane/MoS2 hetero-bilayers, are calculated by the first-principles method. The interlayer interactions of all the bilayer systems are shown to be mainly van der Waals. Both the graphane/MoS2 and silicane/MoS2 hetero-bilayers belong to the type-II heterostructure, which can be utilized in photo-voltaic devices due to the efficient spatial separation of electrons and holes. For optical properties, the distinctions for the imaginary parts of the dielectric function e 2 ( ω ) between the monolayer and bilayer systems for both the graphane and silicane are more evident in electric vector E||z. However, the differences between e 2 ( ω ) of the monolayer and bilayer MoS2 materials are more significant in E||x. Broader light absorption ranges of the hetero-bilayers are reached, which can also improve the charge separation of the electron-hole pairs.

Organic compounds are widely used in both industry and daily life, and composite bilayer films with organic compound-triggered bending properties are promising for applications of transducers, soft robotics, and so on. Here, a universal and straightforward strategy to generate composite bilayer films with organic compound-triggered bending properties is demonstrated. The composite bilayer films with organic compound-triggered bending properties are designed with bilayer structures, in which one layer is a porous polymeric membrane with appropriate solubility parameter that matches the value of organic solvents in order to produce prominent affinity to the solvent molecules, and the other layer is reduced graphene oxide membrane stacked on the porous polymeric membrane as an inert layer for restraining the swelling of the polymeric membrane on one side. Guided by matching the solubility parameters between solvent and polymer, a significant bending curvature of 27.3 cm−1 is obtained in acetone vapor. The results in this study will provide valuable guidance for designing and developing functional composite materials with significant organic compound-triggered bending properties.

The hydrophilicity of smart additives thermodynamically and kinetically affects the degree and velocity of the phase separation of casting solution, together with their distribution on the membranes, which ultimately affects the microstructure and properties of smart membrane. However, the reasonable design and successful preparation of additives with different hydrophilicity, as well as the observation of their migration during membrane formation process and final distribution on/in the membranes remain challenges. The three kinds of thermo-responsive submicrogels with similar chemical structures and different hydrophilicity were successfully fabricated and blended into poly(ether sulfone) (PES) as functional gates to prepare smart membranes via vapor-induced phase separation (VIPS). The hydrophilicity of poly(N-n-propylacrylamide) (PNN), poly(N-isopropylacrylamide) (PNI) and poly(N-isopropylmethacrylamide) (PNM) submicrogels were quantitively measured; their diameters and thermo-responsive factors in water were similar. Moreover, the effects of the hydrophilicity of submicrogels on the microstructures and properties of as-prepared smart membranes were systematically investigated and the results were elucidated in principle. The results showed the velocity of phase separation of casting solution, the pore size of membranes and the number of submicrogels distributed on membranes increased whereas the stability of submicrogels on membranes decreased with the enhancement of hydrophilicity of submicrogels. The membrane blended with PNI submicrogels with optimal hydrophilicity, which was provided with both a large number of submicrogels stably distributed on the membrane pores as smart gates and appropriate pore size, exhibited excellent permeability and thermo-responsiveness. The maximum water flux through this membrane was 26271 kg m−2 h−1 bar−1, and its maximum normalized thermo-responsive coefficient N value reached to 28.7. The results will provide valuable guidance for understanding the mechanism of phase separation and further development of smart membranes with satisfactory performances.

Cell wall components and structure impact the physical and mechanical properties of plants, thereby affecting wood applications. Lignin is the most abundant biopolymer after cellulose in the wood cell wall and can be modified by certain lignin biosynthesis enzymes. 4-Coumarate: coenzyme A ligase(4CL) is an important lignin biosynthesis enzyme. To demonstrate the impact of the regulation of Pto4CL1 from poplar on wood properties, we analyzed the composition and anatomy of 5-year-old Pto4CL1-modified poplar cell walls, assessing the density, strength, volume shrinkage, and impact toughness of the transgenic trees. These results showed that the up-regulation of Pto4CL1 increased the lignin content to 46.65% from 33.11% in the control plants, while hydrophilic polysaccharides such as cellulose, hemi-cellulose, and pectin decreased. In contrast, the down-regulation of Pto4CL1 resulted in a reduction in lignin content to 27.39%, and the content of cellulose and hemi-cellulose showed compensatory variation. Raman spectroscopy showed that the change in lignin in the transgenic events was embodied in the deposition and concentration of lignin in the secondary cell wall. Moreover, the increased lignin content caused significantly increased wood strength and slightly increased wood density. In contrast, a reduction in lignin content resulted in a significant decrease in wood strength and a slight decrease in wood density. However, the Pto4CL1-modified trees had similar stiffness to the control group. We also found a significant decrease in volume shrinkage and increase in impact toughness in the low-lignin events. These results indicate that Pto4CL1 regulation alters the chemical composition of plant cell walls and these changes affect the physical and mechanical properties of the wood.

At present, selective and efficient removal of cesium ions (Cs+) from nuclear waste is of significant importance but still challenging. In this study, an easy-to-get and low-cost hydrogel adsorbent has been developed for effective adsorption and removal of Cs+ from aqueous environment. The novel Cs+-recognizable poly(acrylic acid-co-benzo-18-crown-6-acrylamide) (poly(AAc-co-B18C6Am)) hydrogel is specifically designed with a synergistic effect, in which the AAc units are designed to attract Cs+ via electrostatic attraction and the B18C6Am units are designed to capture the attracted Cs+ by forming stable 2:1 "sandwich" complexes. The poly(AAc-co-B18C6Am) hydrogels are simply synthesized by thermally initiated free-radical copolymerization and display excellent Cs+ adsorption from commonly coexisting metal ions. Important parameters affecting the adsorption are investigated comprehensively, and the adsorption kinetics and adsorption isotherms are also discussed systematically. The poly(AAc-co-B18C6Am) hydrogels exhibit rapid Cs+ adsorption within 30min and the adsorption process is governed by the pseudo-second order model. Adsorption isotherm results demonstrate that the equilibrium data are well fitted by the Langmuir isotherm model, indicating that the Cs+ adsorption is probably a monolayer adsorption process. Such Cs+-recognizable hydrogel materials based on the host-guest complexation are promising as efficient and feasible candidates for adsorption and removal of radioactive Cs+ from nuclear contaminants.

Graphene oxide (GO) membranes become emerging efficient filters for molecular or ionic separation due to their well-defined two-dimensional nanochannels formed by closely spaced GO sheets and tunable physicochemical properties. The stability of GO membranes in aqueous solutions is a prerequisite for their applications. Here we show a novel and easy strategy for fabricating GO membranes with strong stability in aqueous solutions and controllable lamellar spacing by simply doping with partially reduced graphene oxide (prGO) sheets. With our prGO-doping strategy, the interlayer stabilizing force in GO membranes is enhanced due to the weakened repulsive hydration and enhanced π-π attraction between GO sheets; as a result, the fabricated GO membranes are featured with controllable lamellar spacing and extraordinary stability in water or even strong acid and base solutions as well as strong mechanical properties, which will expand the application scope of GO membranes and provide ever better performances in their applications with aqueous solution environments.

Improving both nitrogen utilization and peanut kernel quality (after removing peanuts shell) through water management is a growing concern for farmers. To explore the role of supplemental irrigation in nitrogen transformation between ‘source’ and ‘sink’, a split-plot experiment was conducted to evaluate the effects of water (rain-fed irrigation as IRI; supplemental irrigation as ISI) and nitrogen (0 kg∙ha―1 as N0; 40 kg∙ha―1 as N1; 60 kg∙ha―1 as N2 and 80 kg∙ha―1 as N3) coupling on soil nitrate nitrogen content, nitrogen accumulation and kernel quality of peanuts. We determined the dry matter weight per plant at peanut maturity as 64.66—74.92 g and 71.65—92.81 g for IRIN0 and ISIN3, respectively. ISIN2 significantly increased nitrogen accumulation, yield and water productivity. Furthermore, the ISI treatment prolonged the nitrogen uptake accumulation time of leaves, thus enhancing the nitrogen transfer from the leaves to the pods. Thus, the ISI treatment significantly increased the nitrogen harvest index by 2.13% and the nitrogen agronomic efficiency by 78.57% compared to the IRI treatment. In addition, the essential amino acid content in the fruits was within the range of 5.57—6.08%, while the content of non-essential amino acids was 16.43 to 17.46%. N1 was able to significantly increase the content of non-essential and essential amino acids, while ISI reduced the content of essential amino acids. Post-harvest soil nitrate nitrogen was principally distributed in the 0—40 cm soil layer, accounting for 77.75% of the 0—60 cm soil layer. Although the supplemental irrigation is associated with an increased risk of the nitrogen moving deeper into the soil, it greatly enhances nitrogen transfer from leaves to the pods at nitrogen application rates of 40—60 kg ha―1.

The optical and electronic properties of graphane and silicane are studied by a first-principles method based on density functional theory, employing both the hybrid (HSE06) and the Perdew–Burke–Ernzerhof (PBE) functionals. Our HSE06 results show that graphane has a direct band gap of 4.49 eV, while silicane has an indirect band gap of 2.94 eV. In graphane, the imaginary part of dielectric function e 2 ( ω ) has two peaks at 7.70 and 15.03 eV for E||z, while for E||x, there are three peaks lying at 11.56, 13.25 and 14.33 eV. In silicane, e 2 ( ω ) has a main peak at 8.68 eV for E||z, while there are two peaks at 4.56 and 8.55 eV for E||x. In graphane, the peaks in e 2 ( ω ) are mainly due to the transitions from C 2p and H 1s states to C 2s and 2p ones; while in silicane, the peaks are primarily originated from the transitions from Si 3p and H 1s states to Si 3s and 3p as well as H 1s states.

In-depth investigations of the specific ion-responsive characteristics based on 2:1 "sandwich" structures and effects of crown ether cavity sizes on the metal-ion/crown-ether complexation are systematically performed with a series of PNIPAM-based responsive copolymers containing similar contents of crown ether units with different cavity dimensions (12-crown-4 (12C4), 15-crown-5 (15C5), 18-crown-6 (18C6)). The lower critical solution temperature (LCST) values of copolymers in deionized water shift to lower temperatures gradually when the crown ether contents increase or the ring sizes decrease from 18C6 to 12C4. With increasing the concentrations of alkali metal ions (Na(+), K(+), Cs(+)) or the contents of pendent crown ether groups, the copolymers with different crown ether cavity sizes exhibit higher selectivity and sensitivity to corresponding cations. Importantly, the ion sensitivities of the copolymers in response to corresponding alkali metal ions increase dramatically with an increase in the crown ether cavity size. Interestingly, a linear relationship between the crown ether cavity size and the diameter of corresponding cation for the formation of stable 2:1 "sandwich" complexes is found for the first time, from which the size of metal ions or other guests that able to form 2:1 "sandwich" complexes with crown ethers can be deduced. The results in this work are valuable and useful for further developments and practical applications of various crown-ether-based smart materials.

Facilitated transport of K+ ions through membranes is of great significance in both science and technology for the efficient and selective separation of potassium ions. Here, a novel membrane with ion-recognizable copolymers in graphene-based nanochannels is developed for facilitated transport of potassium ions. The poly(N-isopropylacrylamide-co-benzo-15-crown-5-acrylamide) (PNB) copolymers are fixed in the lamellate spacings between the partially reduced graphene oxide (prGO) nanosheets. The K+ permeability of the fabricated prGO-PNB membrane remarkably increases at around the lower critical solution temperature (LCST) of the PNB copolymer, because of the dynamic complexation between B15C5 units and K+ ions at around the LCST. The selectivity of K+/Na+ increases with increasing the content of PNB copolymers in the membrane. The proposed membrane shows good stability in water and K+ separation performance. Due to the uniform channels and facilitated transport mechanism of the prGO-PNB membrane, the comprehensive performance of selectivity and permeability of the K+ ions is better than that of previously reported polymer-based nanofiltration membranes, polymer-based facilitated transport membranes and graphene-based membranes. The proposed strategy of this prGO-PNB membrane that combining graphene-based sheets as “skeleton” and substance-recognizable copolymers as “facilitators” is also applicable to fabricate membranes for facilitated transport of other ions or molecules.

Gossypol is an attractive therapeutic anti-tumor agent as an apoptosis inducer and is being evaluated in preclinical tests. However, the molecular mechanisms underlying apoptosis induction by gossypol in malignant cells have not been completely enunciated. Here we investigate the alterations of Bcl-2/Bcl-xL/Mcl-1 protein levels and Bcl-2 phosphorylation in gossypol-induced apoptosis in human leukemia HL-60 cells. We found that gossypol treatment inhibited cell growth and induced apoptosis in HL-60 cells. Bcl-2/Bcl-xL/Mcl-1 protein levels were slightly reduced and phosphorylation of Bcl-2 at threonine 56 (phospho T56) was not altered. However, phosphorylation of Bcl-2 at serine 70 (phospho S70) was strikingly down-regulated in gossypol-exposed cells. This reduction was found to be not only in both dose- and time-dependent fashion but also obviated by phorbol l2,13-dibutyrate (PDBu), an activator of protein kinase C (PKC). In addition, pre-treatment of PDBu partially prevented gossypol-induced apoptosis in HL-60 cells. Collectively, gossypol treatment can reduce phosphorylation of Bcl-2 at serine 70 in leukemia HL-60 cells and gossypol may be a promising therapeutical candidate for leukemia patients especially expressing phosphorylated Bcl-2 at Ser70.