Co-reducing Agent Research Articles

PH and Temperature-Responsive Silk Sericin/N-Isopropyl Acrylamide Interpenetrating Network Gel and Viscose Non-Woven Cross-Linked Composite Dressing

A gel (SNA-Ag) loaded with nanoscale silver particles and a pH-responsive agent was prepared using N-isopropyl acrylamide (NIPAAm) as the first network structure, silk sericin (SS) as the second network structure and reducing agent, alizarin as the pH indicator and co-reducing agent, N, N-methylene bisacrylamide (BIS) as the crosslinking agent, ammonium persulfate (APS) as the initiator and N, N, N, N-tetramethylethylenediamine (TEMED) as co-initiator. To improve the breaking strength of the gel, the temperature and pH-responsive antibacterial (V/SNA-Ag) composite dressing was prepared by crosslinking the SNA-Ag gel with viscose non-woven fabric using glutaraldehyde as the crosslinking agent. Fourier transform infrared spectrometer (FTIR) and scanning electron microscopy (SEM) showed that the SNA-Ag hydrogel was successfully crosslinked with the viscose non-woven fabric. Meanwhile, a gel coating was formed on the fabric, and the coating thickness increased when the crosslinking time was extended. Differential Scanning Calorimetry (DSC) and pH response tests confirmed that the dressing was temperature sensitive, and the Lower Critical Solution Temperature (LCST) of the dressing was about 35 °C. When the pH of the dressing was changed from acidic to alkaline, its color was changed from yellow to purple, indicating that its color presented pH response characteristics. The dressing not only had excellent swelling performance but also had outstanding antibacterial activity; the antibacterial degree for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was up to 99%. A cytotoxicity test suggested that the survival degree of mouse cells after incubation for 96 h was more than 75%, proving that it was safe and nontoxic. In addition, compared with viscose non-woven fabric, the breaking strength of composite dressing was increased, and the air permeability was decreased. In conclusion, we suggest that V/SNA-Ag composite dressings have great potential for monitoring and treating wounds.

Dendritic quinary PtRhMoCoFe high-entropy alloy as a robust immunosensing nanoplatform for ultrasensitive detection of biomarker

Recently, high-entropy alloys have superior physicochemical properties as compared to conventional alloys for their glamorous “cocktail effect”. Nevertheless, they are scarcely applied to electrochemical immunoassays until now. Herein, uniform PtRhMoCoFe high-entropy alloyed nanodendrites (HEANDs) were synthesized by a wet-chemical co-reduction method, where glucose and oleylamine behaved as the co-reducing agents. Then, a series of characterizations were conducted to illustrate the synergistic effect among multiple metals and fascinating structural characteristics of PtRhMoCoFe HEANDs. The obtained high-entropy alloy was adopted to build a electrochemical label-free biosensor for ultrasensitive bioassay of biomarker cTnI. In the optimized analytical system, the resultant sensor exhibited a dynamic linear range of 0.0001–200 ng mL−1 and a low detection limit of 0.0095 pg mL−1 (S/N = 3). Eventually, this sensing platform was further explored in serum samples with satisfied recovery (102.0 %). This research renders some constructive insights for synthesis of high-entropy alloys and their expanded applications in bioassays and bio-devices.

Ag-Cu Nanoparticles as Cathodic Catalysts for an Anion Exchange Membrane Fuel Cell

In this work, the synthesis of bimetallic Ag and Cu particles on carbon vulcan (AgCu/C) is reported, synthesized by a simple galvanic displacement method using citrate tribasic hydrate as a co-reducing agent and a commercial material based on Cu/C as a template. The materials were characterized by several physicochemical techniques, including TGA, ICP-OES, XRD, SEM, and BET. The catalysts were evaluated as cathodic catalysts for the oxygen reduction reaction (ORR) and were used for the preparation of membrane electrode assemblies for evaluation in an Anion Exchange Membrane Fuel Cell (AEMFC). The results were compared with the commercial Ag/C and Cu/C catalysts; the bimetallic catalyst obtained a higher power density, which was attributed to a synergistic effect between Ag and Cu particles.

One-Pot Synthesis of Pt High Index Facets Catalysts for Electrocatalytic Oxidation of Ethanol.

Direct ethanol fuel cell (DEFC) has attracted wide attention due to its wide range of fuel sources, cleanliness, and high efficiency. However, the problems of low catalytic efficiency and poor catalyst stability still exist in DEFC catalysts, which restrict its rapid development. With chloroplatinic acid (H2PtCl6·6H2O) as the precursor, Polyvinylpyrrolidone (PVP) plays the role of surfactant, stabilizer, and reducing agent in the experiment. Glycine is the surface control agent and co-reducing agent. Pt high-index facets nanocatalyst was prepared with the one-pot hydrothermal method by adjusting the amount of PVP and glycine. X-Ray Diffraction (XRD), transmission electron microscope (TEM), and scanning electron microscope (SEM) were used to characterize the micro-structure of the nanocatalyst, and the influence of PVP and glycine on the synthesis of high-index facets catalyst was studied. The electrocatalytic performance of the catalyst was tested with an electrochemical workstation, and it was found that the performance of the prepared catalyst was better than that of the commercial catalyst. When the mass ratio of PVP and Pt was 50:1 and the molar ratio of glycine and Pt was 24:1, Pt nanocatalysts with {310}, {520} and {830} high exponential facets were prepared. The electrochemical test results showed that the peak current density of ethanol oxidation was 2.194 m2/g, and the steady-state current density was 0.241 mA/cm2, which was 5.7 times higher than that of commercial catalyst. The results of this paper show that due to the defects such as steps and kinks on the surface of the high-index facets, the active sites are increased, thus showing excellent electrocatalytic performance. This study provides a theoretical basis for the development and commercial application of high index facets nanocatalysts.

Palladium-Catalysed Reductive Aminocarbonylation of Aryl Bromides and Iodides with Nitroarenes

AbstractAmide functional groups are a structural feature in a vast array of beneficial organic molecules. This has resulted in a surge in new methodologies developed to enable access to this functional group using a broad range of coupling partners. Herein, we report a palladium-catalysed reductive aminocarbonylation of aryl bromides and iodides with nitroarenes to afford the respective amide products. The developed protocol employs Mo(CO)6 as a carbonyl source and a combination of Zn and TMSCl as co-reducing agents. For most substrates, the anticipated amide products were obtained in modest to high amide product yields.

Formation of multishell Au@Ag@Pt nanoparticles by coreduction method: a microscopic study

Metallic nanoparticles of Ag–Pt double-shell on Au-core (Au@Ag@Pt core@multishell NPs) with a hollow-granular shell structure were synthesized by coreduction method, a combination of galvanic replacement reaction with a coreducing agent. Their nanostructures were examined in detail at different reduction reaction periods to gain insights into the mechanism of Ag–Pt double-shell formation on Au-core, as well as the competitive role of each reduction reaction. The multishell NPs were found to contain a degree of hollows with the inner surface composed of both Ag and Pt, while the outer surface composed of granular Pt. The coreduction method contributed to the success of increasing Pt surface area that will further benefit catalytic applications of the NPs.

Efficient air epoxidation of cycloalkenes over bimetal-organic framework ZnCo-MOF materials

To date, it was difficult to develop catalytic systems for activating O2 in the absence of initiator and sacrificial co-reductant for high-efficiency epoxidation of olefins under mild conditions. Herein, different compositions of ZnCo-MOF have been prepared via a dry-gel crystallization method, which were used to catalyze the epoxidation of α-pinene with air at 90 °C. Zn0.1Co1-MOF-D2-24 performed the best catalysis activity to give 95.5 % α-pinene conversion and 96.7 % epoxide selectivity. The epoxidation results showed that Zn and Co could effectively activate air to epoxidize α-pinene in high efficiency. This bimetal catalytic effect was assigned to the contribution of interacted lattice Zn and Co ions embedded into crystalline MOF framework with similar electronic structure and ion radius, which avoided the use of organic peroxide initiators and other co-reducing agents. Under anhydrous conditions, Zn0.1Co1-MOF-D2-24 showed stable catalytic activity in the epoxidation of α-pinene with air by at least six recycles.

Ternary Palladium-Boron-Phosphorus Alloy Mesoporous Nanospheres for Highly Efficient Electrocatalysis.

Alloying palladium (Pd) catalysts with various metalloid and nonmetal elements can improve their catalytic performance in different chemical reactions. However, current nanosynthesis methods can only generate Pd alloys containing one metalloid or nonmetal, which limits the types of element combinations that may be used to improve Pd-based nanocatalysts. Herein, we report a simple soft-templating synthetic strategy to co-alloy Pd with the metalloid boron (B) and the nonmetal phosphorus (P) to generate ternary PdBP mesoporous nanospheres (MSs) with three-dimensional dendritic frameworks. We use a one-step aqueous synthesis method where dimethylamine borane and sodium hypophosphite serve as the B and P sources, respectively, as well as the co-reducing agents to drive the nucleation and growth of ternary PdBP alloy on a sacrificial dioctadecyldimethylammonium chloride template. The concentration of metalloid to nonmetal and the diameters of dendritic MSs can be tailored. The synthetic protocol is also extended to other multicomponent PdMBP alloy MSs to generate different types of dendritic mesoporous frameworks. Boron and phosphorus are known to accelerate the kinetics of the electrochemical oxygen reduction reaction (ORR) and alcohol oxidation reactions (AORs), because their alloys promote the decomposition of oxygen-containing intermediates on Pd surfaces. The dendritic mesoporous morphology of the ternary PdBP MSs also accelerates electron/mass transfer and exposes numerous active sites, enabling better performance in the ORR and AORs. Extending the surfactant-templating synthetic route to multiple types of elements will enable the generation of libraries of multicomponent metal-metalloid-nonmetal alloy nanostructures with functions that are suitable for various targeted applications.

Highly active Pt3Rh/C nanoparticles towards ethanol electrooxidation. Influence of the catalyst structure

The electrochemical oxidation of ethanol results in the formation of strongly adsorbed intermediates. Pt–Rh catalysts are proposed as alternatives since they easy the CC bond breaking. However, the effect of the Pt–Rh structure on the catalytic activity and selectivity to CO2 is not well understood. Here, we synthesised Pt/C and two different Pt–Rh/C catalyst architectures, an alloy (Pt3Rh/C) and a bimetallic mixture (Pt3–Rh/C) to study the effect of catalyst structure on its catalytic activity and on the products formed during the ethanol oxidation in acid media. The nanoparticles were prepared by a modified polyol reduction method using ethylene glycol as a co-reducing agent and Pb as a material of sacrifice, to obtain very small and well-dispersed nanoparticles on the carbon support. Fourier transform infrared spectroscopy and derivative voltammetry was used to give insights about the ethanol oxidation mechanism occurring at the developed catalysts. The samples characterised by X-ray diffraction analysis showed distortions in the Pt lattice parameters for the Pt-Rh alloy structure due to the presence of Rh in the catalyst’s composition. Transmission electron microscopy analyses indicate that nanoparticles were well-dispersed on a carbon support, with spherical shapes and small particle sizes (2–3 nm). in situ X-ray absorption spectroscopy data evidence that Pt–Rh interactions produce changes in the Pt 5d band vacancy. The electronic effect is maximized when Pt forms an alloy with Rh, resulting in the highest d-band vacancy of the Pt3Rh/C. The Pt3Rh/C catalyst showed the highest activity towards ethanol oxidation, presenting current densities in a quasi-steady-state condition (measured at 600 mV) around 5.2 times higher than the commercial Pt/C (Alfa Aesar). Moreover, the onset potential for ethanol oxidation shifts to more negative potentials (110 mV lower taken at 1 mA cm–2) was also observed. In situ FTIR data revealed that Pt/C catalyst favours the formation of acetic acid. The synergistic effect between Rh and the alloy structure results in an easier CC bond breaking for Pt3Rh/C, in comparison to Pt3–Rh mixture, thus favouring CO2 formation at lower potentials.

Ascorbic acid assisted bio-synthesis of Pd-Pt nanoflowers with enhanced electrochemical properties.

Bimetallic Pd-Pt nanoflowers (Pd-Pt NFs) of varying sizes (20–60nm) were synthesized through the concurrent reduction of Pd(NO3)2 and K2PtCl4 using Cinnamomum camphora (C. camphora) leaf extract assisted by ascorbic acid (AA). C.Camphora acted as both a co-reducing agent and a green template in the synthesis protocol providing a fast, simple, green and cost-effective means of producing the Pd-Pt NFs. Characterization techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to confirm the Pd-Pt NFs formation. FT-IR analysis showed that biomolecules such as polyphenols and flavonoids were responsible for the reduction while stretching vibration bands from CH, CC, OH, and CO O acted as capping agents. The as-formed Pd-Pt NFs showed excellent performance and stability in the electro-oxidation of ethanol in alkaline media. Electro-catalytic performance increased with Pt content, while addition of Pd increased stability. The PdPt3 NFs presented the best performance with a mass activity of 1.43Amg−1metal, 5.72, 4.93, 2.27, 1.27, 11 and 4.6% higher than the Pd, Pt, Pd3Pt, and PdPt NFs, and commercial Pt and Pd-black respectively. However, it was more prone to poisoning, with an If/Ir value of 0.78 compared to 1.37 for Pd3Pt NFs.

Facile fabrication of high-quality Ag/PS coaxial nanocables based on the mixed mode of soft/hard templates.

A new kind of high-quality Ag/PS coaxial nanocables can be facilely synthesized by using soft/hard templates method. In order to effectively introduce Ag sources into porous polystyrene (PS) nanotubes which were trapped in porous anodic aluminum oxide (AAO) hard template, Pluronic F127 (F127) was used as guiding agent, soft template and reductant. Meanwhile, ethylene glycol solution was also used as solvent and co-reducing agent to assist in the formation of silver nanowires. The influences of concentration of F127 and reducing reaction time on the formation of Ag/PS coaxial nanocables were discussed. Results indicated that the high-quality Ag/PS coaxial nanocables can be obtained by the mixed mode of soft/hard templates under optimized conditions. This strategy is expected to be extended to design more metal/polymer coaxial nanocables for the benefit of creation of complex and functional nanoarchitectures and components.

Interlocked graphene–Prussian blue hybrid composites enable multifunctional electrochemical applications

There has been increasing interest recently in mixed-valence inorganic nanostructure functionalized graphene composites, represented by Prussian blue, because they can cost-effectively apply to biosensors and energy devices. In this work, we present a one-pot green method to synthesize interlocked graphene–Prussian Blue hybrid composites as high-performance materials for biosensors and supercapacitor electrodes. Given the fact that graphene oxide (GO) can act as an electron acceptor, we used iron(II) and glucose as co-reducing agents to reduce GO under mild reaction conditions without introducing toxic agents. High quality Prussian blue nanocubes with no or little coordinated water were generated simultaneously. Reduced graphene oxide (rGO) was thus functionalized by Prussian blue nanocubes via chemical bonding to form a kind of interlocked microstructure with high stability and good conductivity. The as-synthesized composites were tested for biosensing of hydrogen peroxide (H2O2) and as supercapacitor electrode materials. The specific capacitance of the microcomposite based electrodes can reach 428Fg−1, with good cycling stability. The microcomposite also displays high performance catalysis towards electroreduction of H2O2 with a high sensitivity of 1.5Acm−2M−1.

Characterization of CuSbSe2crystallites synthesized using a hot injection method

In this study, a novel and facile hot injection method for the synthesis of single phase CuSbSe2crystallites was developed by using low toxic triethylene glycol as both the solvent and reducing agent and triethylenetetramine as co-reducing agent.

Facile synthesis of PtCu3alloy hexapods and hollow nanoframes as highly active electrocatalysts for methanol oxidation

PtCu alloy nanocrystals, especially for the PtCu3 component, hold great potential as catalysts in methanol oxidation reaction (MOR) owing to their promising catalytic properties arising from the bifunctional mechanism associated with Pt and Cu sites. However, Pt and Cu salt precursors are difficult to be co-reduced in a synthesis due to the large difference in their redox potential, because of which Pt or Cu nanocrystals are initially generated and then evolve into a PtCu alloy with remarkable variation of the PtCu component by underpotential deposition (UPD) and galvanic replacement, respectively. Here we report a facile method for the shape-controlled synthesis of PtCu3 alloy nanocrystals by co-reduction of Pt and Cu salt precursors using oleylamine (OAm) and N,N-dimethylformamide (DMF) as co-reducing agents at different temperatures. PtCu3 alloy hexapods with preferential overgrowth along the <100> direction are obtained at 220 °C through co-reduction reaction accompanied by Cl− ion induced underpotential deposition (UPD). Meanwhile, galvanic replacement between PtCu3 alloy nanocrystals and the Pt precursor co-exists with overgrowth induced by co-reduction reaction at 190 °C, eventually resulting in PtCu3 hollow nanoframes. Both the PtCu3 alloy hexapods and hollow nanoframes exhibit remarkably enhanced catalytic properties in terms of activity and stability towards MOR relative to the commercial Pt/C. Specifically, the PtCu3 alloy hexapods and hollow nanoframes show the highest specific (2.96 mA cm−2) activity and mass activity (1.861 mA μgPt−1) for MOR, respectively, which are 13.5 and 24.2 times higher than those of the commercial Pt/C. This enhancement can be attributed to their unique structures and the possible bifunctional mechanism between Pt and Cu.

In silico analysis of Clostridium acetobutylicum ATCC 824 metabolic response to an external electron supply.

The biological production of butanol has become an important research field and thanks to genome sequencing and annotation; genome-scale metabolic reconstructions have been developed for several Clostridium species. This work makes use of the iCAC490 model of Clostridium acetobutylicum ATCC 824 to analyze its metabolic capabilities and response to an external electron supply through a constraint-based approach using the Constraint-Based Reconstruction Analysis Toolbox. Several analyses were conducted, which included sensitivity, production envelope, and phenotypic phase planes. The model showed that the use of an external electron supply, which acts as co-reducing agent along with glucose-derived reducing power (electrofermentation), results in an increase in the butanol-specific productivity. However, a proportional increase in the butyrate uptake flux is required. Besides, the uptake of external butyrate leads to the coupling of butanol production and growth, which coincides with results reported in literature. Phenotypic phase planes showed that the reducing capacity becomes more limiting for growth at high butyrate uptake fluxes. An electron uptake flux allows the metabolism to reach the growth optimality line. Although the maximum butanol flux does not coincide with the growth optimality line, a butyrate uptake combined with an electron uptake flux would result in an increased butanol volumetric productivity, being a potential strategy to optimize the production of butanol by C. acetobutylicum ATCC 824.

Photoredox-Catalyzed Reductive Coupling of Aldehydes, Ketones, and Imines with Visible Light.

Ketyl radical and amino radical anions, valuable reactive intermediates for C-C bond-forming reactions, are accessible through a C=O/C=NR umpolung. However, their utilization in catalysis remains largely underdeveloped owing to the high reduction potential of carbonyl compounds and imines. In the context of photoredox catalysis, tertiary amines are commonly employed as sacrificial co-reducing agents. Herein, an additional role of the amine is proposed, in which it is essential for the organocatalytic substrate activation. The combination of photoredox catalysis and carbonyl/imine activation enables the reductive coupling of aldehydes, ketones, and imines under mild reaction conditions.

A Simple Process for the Preparation of Copper (I) Oxide Nanoparticles by a Thermal Decomposition Process with Borane Tert-Butylamine Complex

To control the optical properties of Cu2O for a variety of application, we synthesized Cu2O in nanoscale without other treatments. Cu2O nanoparticles with an average size of 2.7 nm (sigma < or = 3.7%) were successfully synthesized in this study via a modified thermal decomposition process. Copper (II) acetylacetonate was used as a precursor, and oleylamine was used as a solvent, a surfactant and a reducing agent. The oleylamine-mediated synthesis allowed for the preparation of Cu2O nanoparticles with a narrower size distribution, and the nanoparticles were synthesized in the presence of a borane tert-butylamine (BTB) complex, where BTB was a strong co-reducing agent together with oleylamine. UV-vis spectroscopy analysis suggest that band gap energy of these Cu2O particles is enlarged from 2.1 eV in the bulk to 3.1 eV in the 2.7-nm nanoparticles, which is larger than most other reported value of Cu2O nanoparticles. Therefore, these nanoparticles could be used as a transparent material because of transformed optical property.

An approach to core–shell nanostructured materials with high colloidal and chemical stability: synthesis, characterization and mechanistic evaluation

Silver–polypyrrole (PPy) core–shell nanoparticles have been fabricated by a facile one-step “green” synthesis using silver nitrate as an oxidant and soluble starch as an environmentally benign stabilizer and co-reducing agent. The morphology and optical properties of the particles were significantly affected by the reaction temperature, soluble starch concentration, and ratio of pyrrole monomer to AgNO3 oxidant. The core–shell nanoparticles exhibited outstanding dispersive properties in deionized water due to residual starch, as compared with PPy nanoparticles in which starch was absent. The mechanism of core–shell nanoparticle formation was elucidated through TEM imaging vs. reaction time. The colloidal and chemical stability of the nanoparticles was demonstrated in a variety of solvents, including acids, bases, and ionic and organic solvents, through monitoring the localized surface plasmon resonance of the nanoparticles. Furthermore, the catalytic properties of these silver–PPy core–shell nanoparticles were also demonstrated.

Novel fabrication and catalytic application of poly(ethylenimine)-stabilized gold–silver alloy nanoparticles

Novel synthesis of amine-stabilized Au–Ag alloy nanoparticles with controlled composition has been devised using poly(ethylenimine) (PEI) as a reducing and a stabilizing agent simultaneously. The composition of Au–Ag alloy nanoparticles was readily controlled by varying the initial relative amount of HAuCl4 and AgNO3. Due to the presence of abundant amine functional groups in PEI, which could act as the dissolving ligand for AgCl, the precipitation problem of Ag+ in the presence of Cl− from the gold salt was avoided. On this basis, the relatively high concentrations of HAuCl4 and AgNO3 salts were used for the fabrication of Au–Ag alloy nanoparticles. The PEI thus plays triple roles in this study that include the co-reducing agents for HAuCl4 and AgNO3, the stabilizing agents for Au–Ag alloy nanoparticles, and even the dissolving agents for AgCl. As a novel material for use in catalysis, the Au–Ag alloy nanoparticles including pure Au and Ag samples were exploited as catalysts for the reduction of 4-nitrophenol in the presence of NaBH4. As the Au content was increased in the Au–Ag alloy nanoparticles, the rate constant of the reduction was exponentially increased from pure Ag to pure Au.

Antimicrobial finishing of cotton textile with nanosized silver colloids synthesized using polyethylene glycol

The bacterial inactivation of Escherichia coli and Staphylococcus aureus on antimicrobial cotton textiles was investigated under different experimental conditions with novel, stable Ag colloids fixed on cotton textiles, which were synthesized using short‐chain polyethylene glycol as a solvent and stabilizer, as well as a different coreducing agent. Transmission electron microscopy analysis showed that stable, spherical metal particles, 3–20 nm in diameter with a well‐crystallized structure, were obtained by using ascorbic acid as a coreducing agent. X‐ray photoelectron spectroscopy results indicated that only one state of silver was present on the surface of the antimicrobial textile. The antimicrobial test results showed that the treated textile has an excellent antimicrobial effect and laundering durability.