Ruthenium-doped Ni(OH)2 to enhance the activity of methanol oxidation reaction and promote the efficiency of hydrogen production.

The coupling of the hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR) to produce clean hydrogen energy with value-added chemicals has attracted substantial attention. However, achieving high selectivity for formate production in the MOR and high faradaic efficiency for H2 evolution remain significant challenges. In light of this, this study constructs an Ru/Ni(OH)2/NF catalyst on nickel foam (NF) and evaluates its electrochemical performance in the MOR and HER under alkaline conditions. The results indicate that the synergistic effect of Ni(OH)2 and Ru can promote the catalytic activity. At an overpotential of only 42 mV, the current density for the HER reaches 10 mA cm-2. Moreover, in a KOH solution containing 1 M methanol, a potential of only 1.36 V vs. RHE is required to achieve an MOR current density of 10 mA cm-2. Using Ru/Ni(OH)2/NF as a bifunctional catalyst, employed as both the anode and cathode, an MOR-coupled HER electrolysis cell can achieve a current density of 10 mA cm-2 with a voltage of only 1.45 V. Importantly, the faradaic efficiency (FE) for the hydrogen production at the cathode and formate (HCOO-) production at the anode approaches 100%. Therefore, this study holds significant practical implications for the development of methanol electro-oxidation for formate-coupled water electrolysis hydrogen production technology.

PdAg Nanoparticles with Different Sizes: Facile One-Step Synthesis and High Electrocatalytic Activity for Formic Acid Oxidation.

Recently, direct formic acid fuel cells (DFAFCs) which possess superior advantages such as a low operating temperature, light environmental pollution and high energy density, have been considered as one of the power generation technologies with a bright prospect. Herein, bimetallic PdAg nanoparticles (NPs) with different particle sizes were successfully produced via an easy one-pot solvothermal co-reduction synthetic route and their electrocatalytic performance for formic acid oxidation (FAO) were further investigated. In our strategy, the size of PdAg NPs can be easily controlled by only varying the concentration of precursors. The larger sized PdAg alloy (9.5 nm, noted as PdAg-L) was obtained at a low concentration of precursors, while the smaller PdAg alloy (3.7 nm, named as PdAg-S) was separated from the reaction system with higher solubility by centrifugation. The electrocatalytic activity and stability of the obtained PdAg NPs could be well optimized when incorporated with carbon (C), which is owing to a synergetic effect. The PdAg-S/C exhibits the highest mass activity with around 1.6 times that of PdAg-L/C and 2 times that of commercial Pd/C, which can be attributed to its larger ECSA and lower adsorption energy of the intermediate to facilitate the direct oxidation of HCOOH molecule.

A self-supporting bimetallic Au@Pt core-shell nanoparticle electrocatalyst for the synergistic enhancement of methanol oxidation.

The morphology of Pt-Au bimetal nanostructures plays an important role in enhancing the catalytic capability, catalytic stability and utilization efficiency of the platinum. We designed and successfully prepared Au@Pt nanoparticles (NPs) through an economical, surfactant-free and efficient method of seed-mediated growth. The Au@Pt NPs displayed electrochemical performances superior to those of commercial Pt/C catalysts because their agglomeration was prevented and exhibited better long-term stability with respect to methanol oxidation in acidic media by efficiently removing intermediates. Among the obtained Au@Pt NPs, Au90@Pt10 NPs exhibited the most significantly enhanced catalytic performance for the methanol oxidation reaction (MOR). Their mass and electrochemically active surface area (ECSA)-normalized current densities are approximately 3.9 and 4.6 times higher than those of commercial Pt/C catalysts, respectively. The oxidation current densities of the Au90@Pt10 NPs are approximately 1.8 times higher than those of commercial Pt/C catalysts after 4000 s of continuous measurement because the small Pt NPs grown on the surface of the Au90@Pt10 NPs were effectively stabilized by the Au metal support. This approach may be a facile method for the synthesis of self-supported bimetallic nanostructures, which is of great significance for the development of high performance electrocatalysts and sensors.

Chemically tunable photoresponse of ultrathin polypyrrole.

Building a complex structure system of conductive polymers without a complicated fabricating process is a long-awaited goal to improving the functional photoresponse properties of conductive polymers. In this study, we demonstrate that the photoresponse of polypyrrole (PPy)-based photodetector devices with an ultrathin polymer layer can be chemically modulated by simply immersing the devices into an alkaline solution. After alkaline treatment, the pyrrole unit transforms into a quinoid structure. Characteristics of current-voltage reveal an increased photosensitivity with several orders of magnitude when decreasing the applied bias voltage. Furthermore, ultrathin PPy belts with a width of 100 nm exhibit ultra-high photosensitivites of roughly 1000 (unit) and photoresponsivities of 54.3 A W-1 due to the high surface area ratio of the nanobelts.

Designed self-assembled hybrid Au@CdS core-shell nanoparticles with negative charge and their application as highly selective biosensors.

A novel and general strategy for the synthesis of a monodispersed Au@CdS core-shell structure with uniform morphology and size through a self-assembly process is proposed here. The obtained negatively charged Au@CdS hybrid core-shell nanoparticles (NPs) are highly selective to dopamine (DA), in the presence of oxidation of ascorbic acid (AA) and uric acid (UA), based on electrostatic interaction. The fabricated biosensor shows a wide linear range from 0.002 to 800 µmol L-1, with a lower detection limit of 0.55 nmol L-1 (n = 5, S/N = 3), revealing the high-sensitivity properties. Electrostatic charge plays an important role in the selective electrocatalytic activity of Au@CdS hybrid core-shell nanoparticles, that is the formation of an electrostatic system between the negatively charged Au@CdS hybrid core-shell NPs and the DA cation. The modified electrode is used to achieve the real-time quantitative detection of DA for biological applications, and satisfactory results are obtained. Due to the advantages of the biosensor, its selectivity, sensitivity and stability, it will have a bright future in the field of medical diagnosis.

Fabrication of metal-organic single crystalline nanowires and reduced graphene oxide enhancement for an ultrasensitive electrochemical biosensor.

A novel strategy is first presented here to design and construct a good selective and highly sensitive dopamine (DA) biosensor based on single-crystalline CuPc nanowires with a reduced graphene oxide-Nafion film (rGON/CuPcNWs). Metal-organic semiconductor single-crystalline CuPc nanowires with excellent electronic properties and large surface-to-volume ratios were prepared using a physical vapor transport technique and modified onto a glassy carbon electrode (GCE), and exhibited high electrocatalytic activity for DA detection by immobilizing it onto a GCE with a film of the rGON composite. The introduction of a rGO-Nafion film can significantly improve the electrochemical signal of the CuPcNWs. The relevant detection limit toward dopamine is 0.3 nM with a wide linear range from 0.001 µM to 200 µM. The results of the demonstrated biosensor could provide important enlightenment for the design of more sensitive electrochemical biosensors.

Critical thresholds in flocking hydrodynamics with non-local alignment.

We study the large-time behaviour of Eulerian systems augmented with non-local alignment. Such systems arise as hydrodynamic descriptions of agent-based models for self-organized dynamics, e.g. Cucker & Smale (2007 IEEE Trans. Autom. Control 52, 852-862. (doi:10.1109/TAC.2007.895842)) and Motsch & Tadmor (2011 J. Stat. Phys. 144, 923-947. (doi:10.1007/s10955-011-0285-9)) models. We prove that, in analogy with the agent-based models, the presence of non-local alignment enforces strong solutions to self-organize into a macroscopic flock. This then raises the question of existence of such strong solutions. We address this question in one- and two-dimensional set-ups, proving global regularity for subcritical initial data. Indeed, we show that there exist critical thresholds in the phase space of the initial configuration which dictate the global regularity versus a finite-time blow-up. In particular, we explore the regularity of non-local alignment in the presence of vacuum.

Triphenyl benzene-bridged fluorescent silsesquioxane: shape-controlled hybrid silicas by hydrolytic conditions.

A new silsesquioxane molecule was synthesized, in which triphenyl benzene was connected with three Si(OC2H5)3 groups using three urea groups as the bridge. The molecule could self-assemble through the intermolecular H-bonding among urea groups and pi-pi interaction of triphenyl benzene core in the solution and it could also be transferred into hybrid silicas by hydrolysis. When the non-preorganized silsesquioxane was hydrolyzed, isolated spherical hybrid silica was gained. However, when the silsesquioxane was preorganized before the hydrolyzation uniform interconnected spherical hybrid silica and intertwined nanofibrous one could be generated under acidic and basic conditions, respectively. The photoluminescence (PL) spectra of the obtained hybrid silicas showed that they still kept the emission properties of their precursor silsesquioxane, and the shift of the emission bands was due to the pi-pi interaction of triphenyl benzene in the course of polycondensation.

Synthesis and self-assembly of dichalcone substituted carbazole-based low-molecular mass organogel.

We report the synthesis and self-assembly of a new pi-conjugated dichalcone substituted carbazole-based low molecular mass organogelator. It could form stable gels in most halogen-aromatic solvents. The transmission electron microscopy (TEM) images revealed that the gel formed fibrous structures with diameter of 50-100 nm, which consisted of several thinner fibers. The FT-IR, UV-vis and XRD results suggested that the H-bonds and pi-pi interactions were the main driving forces for the formation of the self-assembled gel, in which the U-shaped molecules were stacked into lamellar structures. The fluorescent spectra showed that the emission of the xerogel red-shifted markedly compared with the sol state, which resulted from the aggregation of the molecules.

Generation of CdS nano-necklaces and NiS nanotubes templated by sugar-appended hydrogel.

A new hydrogel based on glucose-appended Schiff base derivative has been employed as the template to synthesize CdS and NiS nanostructures with different morphologies. The FT-IR and UV-vis results revealed that H-bonding and pi-pi interaction played important roles in the formation of original hydrogel fibers. The study of mineralization mechanism suggested that the inorganic ions were firstly adsorbed at the surface of the hydrogel fibers due to the hydrophilic affinity with the hydrophilic glucose groups. With the penetration of H2S gas, the preformed CdS or NiS nanoparticles on the surface of the fibers acted as the growing points for the continuous growth. And the different adsorption abilities of the metal ions at the hydrogel fibers resulted in the formation of CdS nano-necklaces and NiS nanotubes.

Helical stacking tuned by alkoxy side chains in pi-conjugated triphenylbenzene discotic derivatives.

We report on the synthesis and self-assembly of a new series of discotic molecules containing triphenylbenzene as the core and alkoxy side chain with varying length. It was found that compounds 3 a-c, 4 b and 5 b could form stable gels in several apolar solvents. Transmission electron microscopy (TEM) images revealed that their morphologies were very different for the different alkoxy-substituted organogels. In toluene or hexane, 3 b and 3 c resulted in both left- and right-handed helical fibers, whereas 3 a resulted in straight rigid fibers; 4 b and 5 b resulted in most straight fibers with a few twisted fibers. The results from FT-IR and UV/Vis absorption spectroscopy indicated that the hydrogen bonding and pi-pi interactions were the main driving forces for the formation of the self-assembled gels. Further detailed analysis of their aggregation modes were conducted by UV-visible absorption spectra and X-ray diffraction (XRD) measurements. Based on these findings, the influence of these peripheral alkoxy substituents on the gel formation and the aggregation mode were discussed. The special enhanced fluorescent emissions, which resulted from aggregation, were also found in the gel phase.

L-Tartaric acid assisted binary organogel system: strongly enhanced fluorescence induced by supramolecular assembly.

A new series of binary organogels, which showed good gelated capability and strongly enhanced fluorescence emission, were designed and prepared by simply mixing two components of L-tartaric acid and alkoxyl substituted stilbazoles. It was found that L-tartaric acid could not only introduce stilbazole with fluorescent property into the gel system, but also provided a main motif for the formation of the gel-phase via multiple hydrogen bonds. Meanwhile, pi-pi interactions between the complexes also played a key role in the gel formation. The decreased nonradiative process, suggested by the longer fluorescent lifetime of aggregates than that of monomers and the presence of the J-aggregation for the aggregated state, favored the enhanced fluorescence emission.

Novel CuS nanofibers using organogel as a template: controlled by binding sites.

A new cholesterol organogelator 1 was synthesized, which was confirmed as an effective gelator for various organic solvents and could self-assemble into network fibers in some organic solvents. Moreover, gelator 1 could act as templates for the synthesis of various CuS nanofibers with different helical pitches. For example, when H(2)S was used as the sulfur source, straight and bending helical CuS nanofibers with a pitch of 100-200 nm could be fabricated in butyl acetate and benzene-butanol gel systems, respectively, while bending CuS nanofibers with a similar helical pitch (ca. 50 nm) could be obtained when thioacetamide was used as the sulfur source in both gel systems. It was first found that the morphologies of inorganic nanofibers could be controlled by the binding sites between the inorganic precursor and the organogel.

Novel pearl-necklace porous CdS nanofiber templated by organogel.

A new cholesterol organogelator 4 was synthesized and its gelation property was evaluated. It was confirmed that 4 was an effective gelator for various organic solvents and could self-assemble into network fibers with a bilayer of folded conformation in some organic solvents. Moreover, organogelator 4 could act as a template for the synthesis of novel pearl-necklace porous CdS nanofibers. The transcription process of organogel fibers into CdS nanofibers was investigated, and it was found that Cd2+ ions were coated on the organogel fibers by the interaction with ester groups of 4, which might lead to the change of the arrangement of the organogelator and seemed to serve as nucleation sites for metalization. The further growth of CdS began with these nucleation sites along the organogel fibers. Meanwhile, parts of 4 free from organogel fibers have an effect on the formation of the CdS nanofibers consisting of the network and wormlike CdS particles.

Synthesis, self-assembly and characterization of a new glucoside-type hydrogel having a Schiff base on the aglycon.

A new hydrogel based on a substituted phenyl glucoside with a Schiff base in the aglycon was synthesized, and the self-assembling characteristics was studied. FTIR spectra, UV-vis absorption spectra and X-ray diffraction (XRD) revealed that pi-pi interactions between the Schiff base moieties, hydrogen bonds, and the interdigitated interactions between hydrophobic chains had effects on the formation of the self-assembling hydrogel. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) observation showed that the three-dimensional hydrogel network was constructed from nanotubes with inner diameters of ca. 75 nm and wall of ca. 20 nm.

Synthesis and characterization of nanostructural hydrogel and template for CdS nanofibers.

Hydrogels based on beta-D-glucopyranoside-substituent thiosemicarbazide derivatives were synthesized and used as template to fabricate netlike CdS nanofibers. The self-assembling properties of the hydrogels and their effect on the synthesis of CdS nanostructure were studied. Fourier transform infrared spectra, UV-visible absorption spectra and X-ray diffraction revealed that pi-pi stacking, hydrogen bonds and interdigitated interactions between hydrophobic chains had influence on the formation of self-assembled lamellar hydrogel. Transmission electron microscopic and electron diffraction observation showed the formation of hexagonal stacking nanofiber-based CdS semiconductor materials. The transmission electron microscopic pictures of the CdS nanostructure in difference growth stages revealed the growth mechanism of CdS nanofibers templated by hydrogel.