Superionic conductor Ag2Se modulated CoSe2 nanosheets prepared via monometallic cation release for efficient pH-universal water electrolysis into hydrogen.

Superionic conductors regulated transition metal chalcogenides are the newly emerged electrocatalyst in water electrolysis into clean hydrogen and oxygen. However, there is still much room for the development of structural design, electronic modulation and heterogeneous interface construction to improve the overall water splitting performance in pH-universal solutions, especially in alkaline and neutral mediums. Herein, using ß-cyclodextrin (ß-CD) and citric acid (CA) organics with abundant hydroxyl (-OH) and carboxyl (-COOH), a special Ag2Se nanoparticles-decorated CoSe2 flower-like nanosheets loaded on porous and conductive nickel foam substrate (Ag2Se-CoSe2/NF) was successfully constructed by a new method of monometallic cation release of coordinated cobalt. The Ag2Se phase exerts the nature characteristics of superionic conductors to modulate the morphological and electronic structures of CoSe2 as well as improve its conductivity. The generated rich active interfaces and abundant Se vacancy defects facilitate numerous active sites exposure to accelerate the hydrogen ion transport and charge transfer. Compared to the single-phase Ag2Se/NF-8 and CoSe2/NF, the prepared Ag2Se-CoSe2/NF-8 with a two-phase synergistic effect achieves an outstanding pH-universal electrocatalytic hydrogen production performance by water electrolysis, as evidenced by a lower overpotential (60 mV, 212 mV and 85 mV vs RHE at 10 mA cm-2 for pH = 0.36, 7.00 and 13.70, respectively). Only a voltage of 1.55 V at 10 mA cm-2 is required to implement the overall water splitting in an alkaline electrolyzer. This work provides significant guidance for the future designation and practical development of transition metal chalcogenides with superionic conductors applied in the electrocatalytic field.

Chiral induction in a novel self-assembled supramolecular system composed of α-cyclodextrin porous liquids, chiral silver nanoparticles and planar conjugated molecules.

The newly developed porous liquids known as liquids with permanent microporosity, have considerable application potential in many unknown areas. Herein, a supramolecular system composed of α-cyclodextrin porous liquid, chiral silver nanoparticles and planar conjugated molecules (methylene blue and indigo carmine) was designed and the induced chirality of the system was observed. It was found that the induced chirality can be easily tuned by changing the pH value of the mixture solution. The induced chiral signal of methylene blue in the developed self-assembled supramolecular system occurred when the pH was between 8 and 10, and furthermore the induced chirality of indigo carmine was found when the pH was between 6.5 and 7.5. The intensity of induced chirality decreases upon increasing temperatures and ionic strength. This study may offer a new approach for the creation of a chiral supramolecular system based on host-guest and electrostatic interaction and make cyclodextrin porous liquids promising candidates for applications in chiral induction.

Cyclodextrin Porous Liquid Materials for Efficient Chiral Recognition and Separation of Nucleosides.

Porous liquids are porous materials that have exhibited unique properties in various fields. Herein, we developed a method to synthesize the type I porous liquids via liquefaction of cyclodextrins by chemical modification. The cyclodextrin porous liquids were characterized by Fourier-transform infrared (FTIR) spectroscopy, NMR, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS), circular dichroism (CD), and UV-vis spectroscopy. The measured ionic conductivity of the γ-cyclodextrin porous liquid was 500 times as great as that of its reactants, which was found to be the first instance with such great conductivity for a type I porous liquid. What is more, the γ-cyclodextrin porous liquid had been demonstrated experimentally to have outstanding chiral recognition ability toward pyrimidine nucleosides in water, which was further confirmed by computational simulations. Additionally, enantiomeric excess of the extracted nucleoside was achieved up to 84.81% by convenient extraction from the mixture of racemic nucleosides and γ-cyclodextrin porous liquid. The great features of the novel cyclodextrin porous liquids could bring opportunities in many fields, including the preparation of chiral separation materials, development of new drug screening mechanisms, and construction of chiral response materials.

Copper(II)-ß-cyclodextrin and CuO functionalized graphene oxide composite for fast removal of thiophenic sulfides with high efficiency.

A novel copper(II)-ß-cyclodextrin and CuO functionalized graphene oxide composite (CD-CuO/NH2-GO) was successfully synthesized by reacting mono-6-O-toluenesulfonyl-copper(II)-ß-cyclodextrin with amino and CuO functionalized graphene oxide. The characterization results showed that the CD-CuO/NH2-GO was well-characterized and has a BET surface area of 746.5 m2 g-1 and good thermal stability, and CD and CuO were uniformly dispersed. The unique structure of CD-CuO/NH2-GO is conducive to the synergistic effect of the different components, especially for the inclusion ability of CD. Benefiting from that, CD-CuO/NH2-GO could quickly and efficiently remove the thiophenic sulfides, which are difficult to be economically removed by hydrodesulfurization. The removal efficiency for the three sulfides was in the order of benzothiophene > dibenzothiophene > thiophene. The desulfurization process of benzothiophene has the fastest desulfurization rate (0.121 g mg-1 min-1) and maximum sulfur capacity (12.75 mg S g-1). The different molecular inclusion ability of CD for the thiophenic sulfides demonstrates the difference in the desulfurization of CD-CuO/NH2-GO. The work highlights the synthesis and the potential application in fuel desulfurization of supramolecular GO composite nanomaterials.

New determination method for sulfonation degree of phthalic anhydride by RP-HPLC.

A novel method was developed to monitor the reaction process and evaluate the sulfonation level in the sulfonation of phthalic anhydride by reversed-phase high-performance liquid chromatography (RP-HPLC). The product peak was identified in chromatograms through product analysis and by comparing its retention time with that of standard compounds. By comparing the hydrolysis and alcoholysis methods, optimized pretreatment of the sample was found for RP-HPLC. Based on the determined percentages of phthalic anhydride and sulfonated phthalic anhydride in the mixture, the degree of sulfonation was calculated. When the sulfonation degree of phthalic anhydride was in the range of 2.8-71%, the recovery of 97-104% was achieved, and the procedure was rapid and accurate.

Short peptide-directed synthesis of one-dimensional platinum nanostructures with controllable morphologies.

Although one dimensional (1D) Pt nanostructures with well-defined sizes and shapes have fascinating physiochemical properties, their preparation remains a great challenge. Here we report an easy and novel synthesis of 1D Pt nanostructures with controllable morphologies, through the combination of designer self-assembling I3K and phage-displayed P7A peptides. The nanofibrils formed via I3K self-assembly acted as template. Pt precursors ((PtCl4)(2-) and (PtCl6)(2-)) were immobilized by electrostatic interaction on the positively charged template surface and subsequent reduction led to the formation of 1D Pt nanostructures. P7A was applied to tune the continuity of the Pt nanostructures. Here, the electrostatic repulsion between the deprotonated C-terminal carboxyl groups of P7A molecules was demonstrated to play a key role. We finally showed that continuous and ordered 1D Pt morphology had a significantly improved electrochemical performance for the hydrogen and methanol electro-oxidation in comparison with either 1D discrete Pt nanoparticle assemblies or isolated Pt nanoparticles.

Tuning of peptide assembly through force balance adjustment.

Controlled self-assembly of amphiphilic tripeptides into distinct nanostructures is achieved via a controlled design of the molecular architecture. The tripeptide Ac-Phe-Phe-Lys-CONH2 (FFK), hardly soluble in water, forms long amyloid-like tubular structures with the aid of ß-sheet hydrogen bonding and aromatic π-π stacking. Substitution of phenylalanine (F) with tyrosine (Y), that is, only a subtle structural variation in adding a hydroxyl group to the phenyl ring, results in great change in molecular self-assembly behavior. When one F is substituted with Y, the resulting molecules of FYK and YFK self-assemble into long thinner fibrils with high propensity for lateral association. When both Fs are substituted with Y, the resulting YYK molecule forms spherical aggregates. Introduction of hydroxyl groups into the molecule modifies aromatic interactions and introduces hydrogen bonding. Moreover, since the driving forces for peptide self-assembly including hydrogen bonding, electrostatic repulsion, and π-π stacking have high interdependence with each other, changes in aromatic interaction induce a Domino effect and cause a shift of force balance to a new state. This leads to significant variations in self-assembly behavior.

Immobilization of lipases on alkyl silane modified magnetic nanoparticles: effect of alkyl chain length on enzyme activity.

BACKGROUND: Biocatalytic processes often require a full recycling of biocatalysts to optimize economic benefits and minimize waste disposal. Immobilization of biocatalysts onto particulate carriers has been widely explored as an option to meet these requirements. However, surface properties often affect the amount of biocatalysts immobilized, their bioactivity and stability, hampering their wide applications. The aim of this work is to explore how immobilization of lipases onto magnetite nanoparticles affects their biocatalytic performance under carefully controlled surface modification. METHODOLOGY/PRINCIPAL FINDINGS: Magnetite nanoparticles, prepared through a co-precipitation method, were coated with alkyl silanes of different alkyl chain lengths to modulate their surface hydrophobicity. Candida rugosa lipase was then directly immobilized onto the modified nanoparticles through hydrophobic interaction. Enzyme activity was assessed by catalytic hydrolysis of p-nitrophenyl acetate. The activity of immobilized lipases was found to increase with increasing chain length of the alkyl silane. Furthermore, the catalytic activities of lipases immobilized on trimethoxyl octadecyl silane (C18) modified Fe(3)O(4) were a factor of 2 or more than the values reported from other surface immobilized systems. After 7 recycles, the activities of the lipases immobilized on C18 modified nanoparticles retained 65%, indicating significant enhancement of stability as well through hydrophobic interaction. Lipase immobilized magnetic nanoparticles facilitated easy separation and recycling with high activity retaining. CONCLUSIONS/SIGNIFICANCE: The activity of immobilized lipases increased with increasing alkyl chain length of the alkyl trimethoxy silanes used in the surface modification of magnetite nanoparticles. Lipase stability was also improved through hydrophobic interaction. Alkyl silane modified magnetite nanoparticles are thus highly attractive carriers for enzyme immobilization enabling efficient enzyme recovery and recycling.

Effects of anions on nanostructuring of cationic amphiphilic peptides.

The effects of addition of a series of stoichiometric salts on the nanostructuring of cationic amphiphilic peptides have been investigated through the combination of atomic force microscopy (AFM), circular dichroism (CD), and turbidity measurements. The results revealed that anions had more pronounced effects than cations in tuning the nanostructures formed from these peptides. Addition of ClO(3)(-), NO(3)(-), and Br(-) could stabilize the primary nanostructures (nanostacks, nanospheres, or short nanorods) formed by A(9)K and I(3)K and effectively inhibit their growth into longer nanostructures (nanorods or nanotubes). In contrast, the anions of Cl(-), SO(4)(2-), HPO(4)(2-), PO(4)(3-), and C(6)H(5)O(7)(3-) (citrate) favored the axial growth of these peptides to form long intersecting nanofibrils and led to an increase in diameter and surface roughness, as well, clearly enhancing their propensity for nanostructuring. The efficiency of different anions in promoting the growth of peptide nanoaggregates into larger ones could be ordered as ClO(3)(-) < NO(3)(-) ≤ Br(-) < Cl(-) < SO(4)(2-) < HPO(4)(2-) < PO(4)(3-) < C(6)H(5)O(7)(3-), broadly consistent with the Hofmeister anion sequence. These observations were well rationalized by considering different aspects of direct interactions of the anions with the peptide molecules.

Self-assembly of short peptide amphiphiles: the cooperative effect of hydrophobic interaction and hydrogen bonding.

The interplay between hydrogen bonding, hydrophobic interaction and the molecular geometry of amino acid side-chains is crucial to the development of nanostructures of short peptide amphiphiles. An important step towards developing their practical use is to understand how different amino acid side-chains tune hydrophobic interaction and hydrogen bonding and how this process leads to the control of the size and shape of the nanostructures. In this study, we have designed and synthesized three sets of short amphiphilic peptides (I(3)K, LI(2)K and L(3)K; L(3)K, L(4)K and L(5)K; I(3)K, I(4)K and I(5)K) and investigated how I and L affected their self-assembly in aqueous solution. The results have demonstrated a strong tendency of I groups to promote the growth of ß-sheet hydrogen bonding and the subsequent formation of nanofibrillar shapes. All I(m)K (m = 3-5) peptides assembled into nanofibers with consistent ß-sheet conformation, whereas the nanofiber diameters decreased as m increased due to geometrical constraint in peptide chain packing. In contrast, L groups had a weak tendency to promote ß-sheet structuring and their hydrophobicity became dominant and resulted in globular micelles in L(3)K assembly. However, increase in the number of hydrophobic sequences to L(5)K induced ß-sheet conformation due to the cooperative hydrophobic effect and the consequent formation of long nanofibers. The assembly of L(4)K was, therefore, intermediate between L(3)K and L(5)K, similar to the case of LI(2)K within the set of L(3)K, LI(2)K and I(3)K, with a steady transition from the dominance of hydrophobic interaction to hydrogen bonding. Thus, changes in hydrophobic length and swapping of L and I can alter the size and shape of the self-assembled nanostructures from these simple peptide amphiphiles.

Influence of ovalbumin on CaCO3 precipitation during in vitro biomineralization.

As a major constituent of egg white matrix, ovalbumin has long been perceived to be implicated in the formation of avian eggshells, in particular, the mammillary layer. However, very little is known about the detailed mechanism by which this protein mediates shell calcification. By the combined studies of AFM, SEM, and TEM, we have investigated the influence of ovalbumin on CaCO(3) precipitation under in vitro mineralization conditions. We observed that the influence was multifold. This protein modified the morphology of calcite crystals through a distinct anisotropic process with respect to the four crystal step edges. AFM characterization revealed that the modification was initiated at the obtuse-obtuse step corner and propagated predominantly along the obtuse steps. Furthermore, the protein favored the existence of unstable phases such as amorphous calcium carbonate and crystalline vaterite. In contrast, lysozyme, another protein also present in the system, played a very different role in modifying calcite morphology. The mechanistic understanding gained from this study is clearly also of practical significance in developing advanced inorganic CaCO(3) materials with the aid of morphological manipulation of crystalline structures via different protein mediation.

Hydrophobic-region-induced transitions in self-assembled peptide nanostructures.

Peptide amphiphiles readily self-assemble into a variety of nanostructures, but how molecular architectures affect the size and shape of the nanoaggregates formed is not well understood. From a combined TEM and AFM study of a series of cationic peptide surfactants AmK (m = 3, 6, and 9), we show that structural transitions (sheets, fibers/ worm-like micelles, and short rods) can be induced by increasing the length of the hydrophobic peptide region. The trend can be interpreted using the molecular packing theory developed to describe surfactant structural transitions, but the entropic gain, decreased CAC, and increased electrostatic interaction associated with increasing the peptide hydrophobic chain need to be taken into account appropriately. Our analysis indicates that the trend in structural transitions observed from AmK peptide surfactants is opposite to that obtained from conventional monovalent ionic surfactants. The outcome reflects the dominant role of hydrophobic interaction between the side chains opposed by backbone hydrogen bonding and electrostatic repulsion between lysine side chains.

Role of ovalbumin in the stabilization of metastable vaterite in calcium carbonate biomineralization.

The role of proteins in biomineralization has been examined in this work by studying the effect of ovalbumin on the stabilization of metastable CaCO(3) phases. In the absence of ovalbumin, the mixing of Na(2)CO(3) with CaCl(2) in an aqueous solution led to the formation of metastable phases that swiftly transformed into stable calcite crystals within 4 h under the experimental conditions. However, ovalbumin was found to favor the formation and stabilization of spherical vaterites, and the effect was concentration dependent. In the presence of 2 g/L ovalbumin, for example, vaterite microspheres with diameters ranging from 0.9 to 3.0 mum, composed of much smaller nanosized particles, were produced and stabilized even after 24 h following the initial mixing. In addition, the influence of ovalbumin on the CaCO(3) mineralization process from the very beginning was carefully examined. Both amorphous calcium carbonate (ACC) and vaterite were favored with ovalbumin present, but the ACC phase formed predominantly at the initial stage of mixing followed by the vaterite formation. Vaterite could then be embedded further in the mineralization process and become stabilized many hours afterward. The stabilizing effect of ovalbumin could arise from the strong binding between carboxylate groups of ovalbumin and the calcium ions on the CaCO(3) surface, preventing the metastable CaCO(3) from transformation via dissolution-recrystallization processes. The strong ovalbumin adsorption on vaterite microspheres was revealed from transmission electron microscopy imaging and thermogravimetric analysis, thereby providing useful evidence to support the proposed stabilizing mechanism.

Solid base for hydrogen sulfide removal in light oil.

Three solid bases, with three kinds of activated carbon as supporters and alkaline materials as active components, were tested for hydrogen sulfide removal in light oil. The solid bases have high intensity and greater adsorption capacity for hydrogen sulfide removal and are more easily regenerated.