Giant Phospholipid Folds on Air-Water Surface: Structure Details, Formation Pathway, and Possible Recycle Mechanism.

In vitro mimics recognized that the propensity of a negatively charged phospholipid, DPPS, monolayers to self-aggregate to three-dimensional (3D) giant folds under overcompression at an air-water interface. Time elapsing microscopical observations confirmed that such giant folds were able to float stably on the air-water interface for weeks or even longer. Ex situ atomic force microscopy (AFM) and transmission electronic microscopy (TEM) characterizations pointed out that such giant folds were composed of compactly stacked lipid layers. Phospholipase A2 (PLA2), a principal bactericide in human and animal tear secretion, was chosen to drive the in situ lipid giant folds disassembly on water and supported substrate surfaces, respectively. Our experimental results confirmed the layer-by-layer structures of the giant folds. It is noteworthy that the defect-rich areas of the giant lipid folds were eliminated quickly by PLA2 while defect-free lipid zones were left untouched, suggesting that PLA2 may serve as a highly effective and selective regenerator/cleaner of lipid aggregates in the physiological circumstance of certain organs.

In Situ Fabrication of Defective CoNx Single Clusters on Reduced Graphene Oxide Sheets with Excellent Electrocatalytic Activity for Oxygen Reduction.

A facile one-step strategy for anchoring defective CoNx single clusters on partly reduced graphene oxide (RGO) is constructed to significantly improve the catalytic performance of non-noble metal complexes toward oxygen reduction reaction (ORR). Sequent loading with trace amounts of metal-free porphyrin and Co2+ in RGO can dramatically enhance both the half-wave potential and the peak current density. Intriguingly, the RGO/P/2Co single cluster exhibits the best ORR catalytic performance with the half-wave potential of 0.834 V, extremely approaching that of commercial Pt/C (0.836 V). This half-wave potential surpasses most of the reported half-wave potentials of RGO supported non-noble metal ORR catalysts through low-temperature synthesis. Furthermore, the as-prepared RGO/P/2Co delivers a peak current density of 1.3 times higher than that of Pt/C at the same loading, together with a high mass activity of 2.76 A mgCo-1. During the durability test, a cathodic current loss less than 10% is recorded after 8000 continuous potential cycles. Insights into this successful example will be conducive to the development of elegant routes for constructing metal nitrogen (MN)-based ORR catalysts with high efficiency, outstanding stability, and excellent selectivity.

Architecture of CoNx single clusters on nanocarbon as excellent oxygen reduction catalysts with high-efficient atomic utilization.

A new strategy to fabricate CoNx single cluster supported nanocarbon catalysts (C/P/2Co600) with enhanced atomic utilization towards the oxygen reduction reaction (ORR) is reported. N-Coordination protection and low-temperature pyrolysis are the two key factors for the formation of CoNx single clusters on nanocarbon supports. Morphological and structural identification confirmed the simultaneous anchoring of homo-dispersed CoNx single clusters and N-doping on the nanocarbon under relatively mild thermal treatment conditions. Expectedly, the obtained single cluster catalyst with a trace amount of metal atoms exhibited excellent ORR performance including a positive half-wave potential (0.846 V), a high mass activity (0.98 A mgCo-1, ampere per milligram of cobalt) and outstanding chemical durability after 8000 potential cycles. We believe that our findings provide a new route for the rational design of low-cost and highly active ORR catalytic materials.

In situ hybridization of CoOX nanoparticles on N-doped graphene through one step mineralization of co-responsive hydrogels.

The in situ hydrothermal mineralization for a mixture of graphene oxide (GO) and Co-responsive supramolecular hydrogels led to a hybrid graphene aerogel, doped with Co and N elements. The as-prepared aerogels exhibited a competitive half-wave potential (0.840 V, versus RHE) and peak current density (2.35 mA cm-2) to that of Pt/C (0.836 V, 2.23 mA cm-2, respectively). Furthermore, they demonstrated a significantly perfect catalytic efficiency (nearly 100% of 4e- ORR) toward the oxygen reduction reaction (ORR). Insight into the structural details of the hybrid aerogels indicates that the CoOX active sites anchored on the graphene matrix play a central role in the upgrading of the catalytic performance of graphene aerogels.

Designing isometrical gel precursors to identify the gelation pathway for nickel-selective metallohydrogels.

Two novel multi-responsive metallohydrogels, namely, 2-PF-Ni and 3-PF-Ni, were successfully constructed from phenylalanine derivatives. The 2-PF gelator shows specific responses to Ni2+; particularly, 2-PF-Ni is lavender colored, which has been rarely reported among hydrogels triggered by Ni2+. 3-PF-Ni is light green and exhibits perfect thixotropy. This paper provides insights into the gelation mechanisms of these two metallogels.

Cation Tuning toward the Inference of the Gelation Behavior of Supramolecular Gels.

We serendipitously discovered that the tripeptide Asp-Phe-Phe trifluoroacetic acid salt (hereafter abbreviated as ß-AspFF) formed a reversible thermotropic gel in chloroform solution (at temperatures higher than the boiling point of chloroform), and a stable gel in toluene solution (at equal to or lower than the room temperature). Experimental results indicate that doping metal ions into ß-AspFF toluene gels can trigger morphological variations in the gel skeleton, thereby increasing gel volume and inducing the collapse of organogels. Investigation on the cation-tuned gelation behavior of ß-AspFF can be used to elucidate heating-induced gel collapse (of normal gel) or reverse thermotropic gelation as well as select carbamide and acetamide as activators of ß-AspFF gels in chloroform solution at room temperature.

Correction: A Co(2+)-selective and chirality-sensitive supermolecular metallohydrogel with a nanofiber network skeleton.

Correction for 'A Co(2+)-selective and chirality-sensitive supermolecular metallohydrogel with a nanofiber network skeleton' by Xiaojuan Wang et al., Nanoscale, 2016, DOI: 10.1039/c6nr00822d.

A Co²âº-selective and chirality-sensitive supermolecular metallohydrogel with a nanofiber network skeleton.

This paper introduces a new metallohydrogel precursor that offers a peculiar gelation response to Co(2+) at pH 7-8. It is notable that the stability of this metallohydrogel is significantly dependent on its enantiomeric purity. In addition to the expected multi-stimuli responsive properties, including thixotropy, as well as re-assembly properties on adding HCl, this metallohydrogel possesses excellent self-healing behavior, which is uncommon in low-molecular-weight gelators. Electron microscopy (EM) studies revealed that the cryodried remains of this gel presented as well an organized three dimensional (3D) network of fibrils. This interesting metallohydrogel shows potential for developing new soft materials with drug delivery and catalysis properties.

The in situ synthesis of Ag/amino acid biopolymer hydrogels as mouldable wound dressings.

This manuscript introduces a one-pot fabrication procedure for the preparation of supramolecular hybrid hydrogels from low-cost commercially available natural products through a "green" strategy. In particular, the hybrid hydrogels, which are developed with Fmoc-Glu-OMe, silver nanoparticles and chitosan, exhibit outstanding antibacterial properties and can be regarded as excellent mouldable wound healing biomaterials.

Dyes and Redox Couples with Matched Energy Levels: Elimination of the Dye-Regeneration Energy Loss in Dye-Sensitized Solar Cells.

In dye-sensitized solar cells (DSSCs), a significant dye-regeneration force (ΔG(reg)(0)≥0.5 eV) is usually required for effective dye regeneration, which results in a major energy loss and limits the energy-conversion efficiency of state-of-art DSSCs. We demonstrate that when dye molecules and redox couples that possess similar conjugated ligands are used, efficient dye regeneration occurs with zero or close-to-zero driving force. By using Ru(dcbpy)(bpy)2(2+) as the dye and Ru(bpy)2(MeIm)2(3+//2+) as the redox couple, a short-circuit current (J(sc)) of 4 mA cm(-2) and an open-circuit voltage (V(oc)) of 0.9 V were obtained with a ΔG(reg)(0) of 0.07 eV. The same was observed for the N3 dye and Ru(bpy)2(SCN)2(1+/0) (ΔG(reg)(0)=0.0 eV), which produced an J(sc) of 2.5 mA cm(-2) and V(oc) of 0.6 V. Charge recombination occurs at pinholes, limiting the performance of the cells. This proof-of-concept study demonstrates that high V(oc) values can be attained by significantly curtailing the dye-regeneration force.

Effective blockage of the interfacial recombination process at TiO(2) nanowire array electrodes in dye-sensitized solar cells.

Effective blockage of recombination electron transfer of a fast electron transfer redox couple (ferrocenium/ferrocene or Fc(+)/Fc) at TiO2 nanowire array electrodes is achieved by silanization of the dye loaded TiO2 nanowire array. FT-IR clearly shows the formation of polysiloxane network at fluorine doped tin electrodes covered with TiO2 nanowire arrays and the dye molecules. Compared to the commonly used TiO2 nanoparticle film electrodes, the TiO2 nanowire array has a more spatially accessible structure, facilitating the formation of uniform polysiloxane films. Energy-dispersive X-ray spectroscopy (EDS) also reveals the presence of Si over multiple spots at the cross sections of the silanized TiO2 nanowire array electrodes. As a result, a rather high open-cell voltage Voc (0.69 V) and an enhanced efficiency (0.749 %) for DSSC with the Fc(+)/Fc couple were obtained. Contrary to the passivated TiO2 nanoparticle film electrodes at which a complex, biphasic dependence of electron lifetime on Voc was observed, we recorded a logarithm linear dependence of the lifetime on Voc after the silanization treatment. The nanowire arrays with optimal salinization treatments afford a useful surface for the study of electron recombination and photovoltaic generation in DSSCs.

Ferrocenoyl phenylalanine: a new strategy toward supramolecular hydrogels with multistimuli responsive properties.

In this paper we present a new paradigm for designing hydrogelators that exhibit sharp phase transitions in response to a series of disparate stimuli, including oxidation-reduction reactions (redox), guest-host interactions, and pH changes. We have serendipitously discovered that ferrocenoyl phenylalanine (Fc-F) monomers aggregate in water via a rapid self-assembly mechanism to form stable, multistimuli hydrogels. In comparison to other known mono- and multiresponsive gelators, Fc-F is unique because of its small size, economy of gel-forming components, and exceptionally simple molecular structure. Density functional theory (DFT) ab initio calculations suggest gel formation initially involves an antiparallel, noncovalent dimerization step wherein the ferrocenoyl moiety of one axe-like monomer conjoins with the phenyl group of the second monomer via a π-π stacking interaction to form brick-like dimers. This stacking creates a cavity in which the carboxylic acid groups of each monomer mutually interact via hydrogen bond formation, which affords additional stability to the dimer. On the basis of structural analysis via optical and electrical measurements and additional DFT calculations, we propose a possible stepwise hierachical assembly mechanism for fibril formation. Insights into the self-assembly pathway of Fc-F should prove useful for understanding gelation processes of more complex systems. We expect that Fc-F will serve as a helpful archetypical template for others to use when designing new, stimuli specific hydrogelation agents.

Sensitive immunosensor for tumor necrosis factor α based on dual signal amplification of ferrocene modified self-assembled peptide nanowire and glucose oxidase functionalized gold nanorod.

Sensitive electrochemical immunosensor for the detection of protein biomarker tumor necrosis factor α (TNF-α) was reported that uses ferrocene carboxylic acid (Fc) functionalized self-assembled peptide nanowire (Fc-PNW) as sensor platform and glucose oxidase (GOx) modified gold nanorod (GNR) as label. Greatly enhanced sensitivity is achieved based on a dual signal amplification strategy: first, the synthesized Fc-PNW used as the sensor platform increased the loading of primary anti-TNF-α antibody (Ab(1)) onto electrode surface due to its large surface area. At the same time, the Fc moiety on the nanowire is used as a mediator for GOx to catalyze the glucose reaction. Second, multiple GOx and secondary anti-TNF-α antibody (Ab(2)) molecules are bounded onto each GNR to increase the sensitivity of the immunosensor. After the preparation of the immunosensor based on the traditional sandwich protocol, the response of the immunosensor towards glucose was used as a signal to differentiate various concentrations of TNF-α. The resulting immunosensor has high sensitivity, wide linear range (0.005-10ng/mL) and good selectivity. This immunosensor preparation strategy is a promising platform for clinical screening of protein biomarkers.