Brownian dynamics simulation of two‐dimensional nanosheets under biaxial extensional flow

The morphology dynamics of two‐dimensional nanosheets under extensional flow are investigated using a coarse‐grained model. Nanosheets (graphene, BNNS, MX₂) are promising materials for a variety of materials and electronics applications. Extensional flow fields are often present during dispersion processing, such as spin coating. Both nanosheet properties (e.g., moduli, size) and processing parameters (e.g., extension rate) can have a significant impact on the nanosheet morphology and thus, the structure and properties of the bulk material. Our previously developed dimensionless Brownian dynamics methodology is used to explore biaxial extensional flow. Nanosheets exhibit a flat conformation under extensional flow for high bending moduli and an extended “washrag” conformation for low bending moduli. Intrinsic extensional viscosity increases with strain before reaching a plateau. The intrinsic viscosity exhibits a weak power law with nanosheet molecular weight. These simulation results allow for experimental control over morphology as a function of nanosheet properties and flow type and strength. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1247–1253     

Two dimensional patterning of fluorescent proteins in hydrogels

This work describes the successful micropatterning of hybrid systems consisting of hydrogel-dispersed optically active and controllable proteins on solid surfaces without degradation of the photophysical properties of the light-emitting biomolecules. It demonstrates the preservation of the luminescence properties of proteins entrapped into isolated microstructures of poly(acrylamide) gel. This way we can exploit both the structural and function-preserving properties of the hydrogels and the functionality of light-emitting proteins. We believe that this approach can open the way to the realization of nanopatterned optical memories based on photochromic biomolecules.     

Two dimensional nanomaterial‐based separation membranes

Two dimensional nanomaterials including graphene, hexagonal boron‐nitride, molybdenum disulfide, etc., provide immense potentials for separation applications. However, the tradeoff between selectivity and permeability in choosing 2D nanomaterial‐based membrane is inevitable, limiting the progress on separation efficiency for mass industrial applications. To target these issues, versatile strategies such as the rational design of predefined interlayer channels, membrane nanopores, and reasonable functionalization, as well as new mechanisms have been emerged. In this review, we introduce the recent progress on separation mechanisms of 2D nanomaterial‐based membranes with different structures (including the interlayer channels type and the membrane nanopores type) and their inner surface functionalization. Moreover, the interface designs are discussed, in terms of employing dynamic liquid–liquid/liquid–gas interfaces, to advance the selectivity and permeability of the membranes. We further discuss the variety of separation applications based on 2D nanomaterial‐based membranes. The authors hope this review will inspire the active interest of many scientists in the area of the development and application of membrane science.     

Exfoliated nanosheets as a new strong solid acid catalyst

Two-dimensional metal oxide sheets in HTiNbO(5) and HSr(2)Nb(3)O(10), cation-exchangeable layered metal oxides, were examined as solid acid catalysts. Exfoliation of HTiNbO(5) and HSr(2)Nb(3)O(10) in aqueous solutions formed colloidal single-crystal TiNbO(5)(-) and Sr(2)Nb(3)O(10)(-) nanosheets, which precipitated under an acidic condition to form aggregates of HTiNbO(5) nanosheets and HSr(2)Nb(3)O(10) nanosheets. Although esterification of acetic acid, cracking of cumene, and dehydration of 2-propanol were not catalyzed by original HTiNbO(5) because of the narrow interlayer distance, which prevents the insertion of organic molecules, HTiNbO(5) nanosheets functioned as a strong solid acid catalyst for the reactions. Nanosheets of HSr(2)Nb(3)O(10) exhibited no or slight catalytic activity for these reactions. NH(3) temperature-programmed desorption and (1)H magic-angle spinning nuclear magnetic resonance spectroscopy revealed that HTiNbO(5) nanosheets have strong Br?nsted acid sites, whereas HSr(2)Nb(3)O(10) nanosheets do not.     

Immunogenicity and structural efficacy of P41 of Plasmodium sp. as potential cross-species blood-stage malaria vaccine

Vaccine based strategies offer a promising future in malaria control by generating protective immunity against natural infection. However, vaccine development is hindered by the Plasmodium sp. genetic diversity. Previously, we have shown P41 protein from 6-Cysteine shared by Plasmodium sp. and could be used for cross-species anti-malaria vaccines. Two different approaches, ancestral, and consensus sequence, could produce a single target for all human-infecting Plasmodium. In this study, we investigated the efficacy of ancestral and consensus of P41 protein. Phylogenetic and time tree reconstruction was conducted by RAXML and BEAST2 package to determine the relationship of known P41 sequences. Ancestral and consensus sequences were reconstructed by the GRASP server and Unipro Ugene software, respectively. The structural prediction was made using the Psipred and Rosetta program. The protein characteristic was analyzed by assessing hydrophobicity and Post-Translational Modification sites. Meanwhile, the immunogenicity score for B-cell, T-cell, and MHC was determined using an immunoinformatic approach. The result suggests that ancestral and consensus have a distinct protein characteristic with high immunogenicity scores for all immune cells. We found one shared conserved epitope with phosphorylation modification from the ancestral sequence to target the cross-species vaccine. Thus, this study provides detailed insight into P41 efficacy for the cross-species anti-malaria blood-stage vaccine.     

Enhancing the photodynamic therapy efficacy of black phosphorus nanosheets by covalently grafting fullerene C60

Few-layer black phosphorus (BP) nanosheets show potential application in biomedicine such as photodynamic therapy (PDT), and are therefore commonly used in anticancer therapy and nanomedicine due to being relatively less invasive. However, they suffer from low ambient stability and poor therapeutic efficacy. Herein, C₆₀ was covalently grafted onto the edges of BP nanosheets, and the resultant BP-C₆₀ hybrid was applied as a novel endocytosing photosensitizer, resulting in not only significantly enhanced PDT efficacy relative to that of the pristine BP nanosheets, but also drastically improved stability in a physiological environment, as confirmed by both in vitro and in vivo studies. Such improved stability was due to shielding effect of the stable hydrophobic C₆₀ molecules. The enhanced PDT efficacy is interpreted from the photoinduced electron transfer from BP to C₆₀, leading to the promoted generation of ˙OH radicals, acting as a reactive oxygen species (ROS) that is effective in killing tumor cells. Furthermore, the BP-C₆₀ hybrid exhibited low systemic toxicity in the major organs of mice. The BP-C₆₀ hybrid represents the first BP-fullerene hybrid nanomaterial fulfilling promoted ROS generation and consequently enhanced PDT efficacy.

Covalently grafting C₆₀ molecules onto black phosphorus (BP) nanosheets improves their tumor inhibition rate from 36.6% to 88.2%.     

Two dimensional self-assembly of bis-acylureas having various functional end groups

We present the synthesis and morphology study of thirteen bis-acylurea molecules with various functional end groups. The bis-acylureas have two acylurea groups, -NH-CO-NH-CO-, divided by a pentamethylene spacer, -(CH(2))(5)-, and two symmetric functional end groups, such as, aliphatic, benzyl, mono- and bi-thiophenyl, sulfur-containing, and propargyl (HC[triple bond]CCH(2)-) moieties. The bis-acylureas were synthesized by the coupling reactions of ureas with pimeloyl chloride or pimelic acid. Upon cooling from hot isotropic solutions, the bis-acylureas spontaneously form supermolecules. In the cases of aliphatic, benzyl, mono- and bi-thiophenyl functional groups, two dimensional supramolecular structures with molecularly flat surfaces were formed. Single crystal X-ray diffraction results demonstrate that each bis-acylurea molecule forms biaxial hydrogen bonds with four adjacent molecules forming a grid-like crystalline structure. Among the bis-acylureas with sulfur-containing end groups, those with sulfide (-S-) and disulfide (-SS-) moieties self-organize into two dimensional superstructures, while those with thiol (-SH) and bulky protecting group (-S-trityl) precipitate with irregular shapes. The bis-acylurea with propargyl end groups form superstructures of low order possibly due to the steric effect between the rigid moieties. However, the derivatives prepared by click reactions have lamellar molecular packing similar to those of bis-acylureas forming multilayered nanosheet structures.     

Two dimensional nucleation and growth—Impedance/frequency response

The impedance spectra due to two dimensional nucleation and growth have been calculated.     

Synthesis of vanadium oxides nanosheets as anode material for asymmetric supercapacitor

Vanadium oxides (V₂O₅) have been intensely investigated for advanced supercapacitors due to its extensive multifunctional properties of typical layered structure and multiple stable oxide states of vanadium in its oxides. In this study, V₂O₅ nanosheets are synthesized via V₂O₅ xerogel solvothermal reaction in ethanol solvent at 200 °C for 12 h. The V₂O₅ nanosheets facilitate the easy accessibility of ions and can provide more area available for electrochemical reactions. We have achieved the highest specific capacitance of 298 F/g and good rate discharge for V₂O₅ electrodes. Notably, the capacitance still retains a high retention rate of 85% after 10,000 cycles at 200 mV/s. Furthermore, asymmetric supercapacitors is assembled based on V₂O₅ nanosheets and active carbon electrode, and a specific capacitance of 13.2 F/g is obtained at 1 A/g, with a energy density of 4.7 Wh/kg at a power density of 0.798 kW/kg and remains 2.28 Wh/kg at 7.992 kW/kg. Based on these results, the asymmetric supercapacitor exhibits a good cycle life with 77.3% capacitance retention after 3000 cycles. It suggests that the V₂O₅ nanosheets are promising electrode material for electrochemical supercapacitors.     

Ultrathin NiFeS nanosheets as highly active electrocatalysts for oxygen evolution reaction

The development of efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts is crucial for clean energy conversion and storage devices, such as water-splitting, CO₂ reduction, and metal-air batteries. Herein, we report an efficient 2-dimensional OER catalyst of ultrathin nickel-iron sulfide nanosheets (NiFeS-NS). Dodecanethiol is employed in the synthesis, which prohibits the growth along the Z-axis, thus a nanosheet is obtained. The NiFeS-NS shows high OER catalytic activity, which only requires a small overpotential of 273 mV to achieve the OER current density of 10 mA/cm² in alkaline electrolyte, and almost no decay after 150 h of chronopotentiometry test. The high performance is attributed to the 2-dimensional structure, the synergistic effect from the Ni and Fe components which promotes the formation of the high valence Ni species, and the tuning effect from the in-situ generated sulfate doping. This work demonstrates the advantages of the 2-dimensional sulfides in electrocatalysis.     

Dual-targeting conjugates designed to improve the efficacy of radiolabeled peptides

Radiolabeled regulatory peptides are useful tools in nuclear medicine for the diagnosis (imaging) and therapy of cancer. The specificity of the peptides towards GPC receptors, which are overexpressed by cancer cells, and their favorable pharmacokinetic profile make them ideal vectors to transport conjugated radionuclides to tumors and metastases. However, after internalization of the radiopeptide into cancer cells and tumors, a rapid washout of a substantial fraction of the delivered radioactivity is often observed. This phenomenon may represent a limitation of radiopeptides for clinical applications. Here, we report the synthesis, radiolabeling, stability, and in vitro evaluation of a novel, dual-targeting peptide radioconjugate designed to enhance the cellular retention of radioactivity. The described trifunctional conjugate is comprised of a Tc-99m SPECT reporter probe, a cell membrane receptor-specific peptide, and a second targeting entity directed towards mitochondria. While the specificity of the first generation of dual-targeting conjugates towards its extracellular target was demonstrated, intracellular targeting could not be confirmed probably due to non-specific binding or hindered passage through the membrane of the organelle. The work presented describes a novel approach with potential to improve the efficacy of radiopharmaceuticals by enhancing the intracellular retention of radioactivity.     

Tribological properties of graphene nanosheets as an additive in calcium grease

The addition of graphene nanosheets (GNSs) in lubricating grease could significantly reduce the interfacial friction and improve the load-bearing capacity of the parts. Therefore, it has been considered as having great potential as lubricant additives. In this study, we synthesized GNSs that are prepared by a modified Hummer method, and investigated the effect of GNS with different concentration (0.5%, 1%, 2%, 3%, and 4?wt%) on the tribological properties of the calcium grease. The friction and wear experiments were performed using a four-ball tribometer. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to examine the GNS and the friction mechanisms. Results indicate that the friction reduction ability and anti-wear property of the base grease can be improved with the addition of GNS. It was also found that the friction reduction decreases by 61%, and the wear scar diameter (WSD) decreases by 45%, and the extreme-pressure (EP) properties increased 60% at 3?wt% GNS. It is clear that the GNS in grease easily forms protective deposited films to prevent the rubbing surfaces from coming into direct contact, thereby improving the entire tribological behavior of the grease.     

Electrochemical performance of graphene nanosheets as anode material for lithium-ion batteries

Graphene nanosheets (GNSs) were prepared from artificial graphite by oxidation, rapid expansion and ultrasonic treatment. The morphology, structure and electrochemical performance of GNSs as anode material for lithium-ion batteries were systematically investigated by high-resolution transmission electron microscope, scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy and a variety of electrochemical testing techniques. It was found that GNSs exhibited a relatively high reversible capacity of 672 mA h/g and fine cycle performance. The exchange current density of GNSs increased with the growth of cycle numbers exhibiting the peculiar electrochemical performance.     

Two dimensional multiple scattering in an absorbing medium: Preliminary experiments

Described in this paper are preliminary experimental results which characterizes two-dimensional multiple scattering with absorption. Parameters basic to the experiment are derived and the experiments used for their determination are discussed. Comparisons between theory and experiment are only fair.     

Two dimensional TLC determination of PAH in diluted automobile exhaust gases

A method is described for the determination of polycyclic aromatic hydrocarbons (PAH) in the diluted exhaust gas of diesel vehicles. Sampling is done by drawing off proportional streams from the dilution tunnel. The particulates deposited on filters are sublimed, and the sublimate is purified and prefractionated on silica gel. Further separation and quantitative determination of the PAH is performed by two dimensional TLC in conjunction with In situ fluorescence spectrometry. Results of theoretical considerations and experimental data on the distribution of the emitted PAH between particulate matter and the corresponding gas phase in diluted exhaust are presented. A modified Langmuir adsorption model is used to explain the effects of dilution ratio and sample temperature in the dilution tunnel. Comparison of the emission values for PAH obtained from diluted and undiluted exhaust shows good agreement. Furthermore, the PAH contents of the exhaust gas of several diesel-engined cars are also compared for various driving cycles.     

Lamellar carbon nanosheets function as templates for two-dimensional deposition of tubular titanate

A novel composite composed of tubular titanate-two dimensionally deposited carbon nanosheets was prepared with carbon nanosheets as templates through intercalation and hydrothermal treatment; this nanotube-based composite and its calcined products exhibit both excellent adsorptivity and high photocatalytic activity toward organic molecules.     

Ultrathin two-dimensional bimetal NiCo-based MOF nanosheets as ultralight interlayer in lithium-sulfur batteries

Lithium-sulfur batteries as one of the most promising next-generation high-energy storage system, the shuttle effect, the expansion of cathode and the slow electrode redox kinetics limit its further development. Herein, we report a two-dimensional, ultrathin and ultra-light bimetal-NiCo-organic framework as the interlayer for Li-S batteries. This kind of interlayer can effectively block polysulfides and accelerate the conversion with a thickness of only 1 μm and a load of 0.1 mg/cm². Because the MOF nanosheets with a thickness of a few nanometers have a large specific surface and a large number of exposed accessible active sites. At the same time, the intrinsic activity of each site is enhanced and the catalytic performance is improved due to the synergistic effect of mixed metals and the unique coordination environment around the active sites. So, 2D NiCo MOF/CNT totally meets the requirements for the lightweight and effective interlayer. The initial discharge capacity of cell with 2D NiCo MOF/CNT interlayer can reach 1132.7 mAh/g at 0.5 C. It remained 709.1 mAh/g after 300 cycles, showing good cycling stability and rate performance.