A strategy for fabricating porous PdNi@Pt core-shell nanostructures and their enhanced activity and durability for the methanol electrooxidation.

Three-dimensionally (3D) porous morphology of nanostructures can effectively improve their electrocatalytic activity and durability for various electrochemical reactions owing to big surface area and interconnected structure. Cyanogel, a jelly-like inorganic polymer, can be used to synthesize various three-dimensionally (3D) porous alloy nanomaterials owing to its double-metal property and particular 3D backbone. Here, 3D porous PdNi@Pt core-shell nanostructures (CSNSs) are facilely synthesized by first preparing the Pd-Ni alloy networks (Pd-Ni ANWs) core via cyanogel-reduction method followed by a galvanic displacement reaction to generate the Pt-rich shell. The as-synthesized PdNi@Pt CSNSs exhibit a much improved catalytic activity and durability for the methanol oxidation reaction (MOR) in the acidic media compared to the commercial used Pt black because of their specific structural characteristics. The facile and mild method described herein is highly attractive for the synthisis of 3D porous core-shell nanostructures.

Cyanogel-derived formation of 3 D nanoporous SnO2-MxOy (M=Ni, Fe, Co) hybrid networks for high-performance lithium storage.

Three-dimensional (3 D) nanoporous SnO2 -Mx Oy (M=Fe, Co, Ni, Cu, etc.) hybrid networks possess unique compositional and structural features that are beneficial to lithium storage and are thus anticipated to meet the performance requirements of advanced lithium-ion batteries for transportation and stationary energy storage. Herein, a facile, scalable, and versatile cyanogel-derived method for the construction of 3 D nanoporous SnO2 -Mx Oy hybrid networks was developed for the first time. The formation of 3 D nanoporous SnO2 -NiO, SnO2 -α-Fe2 O3 , and SnO2 -NiO-Co3 O4 hybrid networks was illustrated by using Sn-M cyanogels as precursors. Moreover, the anodic performance of the 3 D nanoporous SnO2 -NiO hybrid network was examined to demonstrate proof of concept. After coating with polypyrrole-derived carbon, the SnO2 -NiO@C hybrid network exhibited superior lithium-storage capabilities in terms of specific capacity, cycling stability, and rate capability.

Arginine-assisted synthesis and catalytic properties of single-crystalline palladium tetrapods.

Noble metallic nanocrystals (NMNCs) with highly branched morphologies are an exciting new class of nanomaterials because of their great potential application in catalysis, sensing, optics, and electronics originating from their unique structures. Herein, we report a facile water-based method to synthesize high-quality palladium (Pd) tetrapods with the assistance of arginine molecule, which is more economical and environmentally friendly than the previous reported carbon monoxide (CO)-assisted synthesis in the organic system. During the synthesis, arginine molecule plays an essential role in controlling the tetrapod-like morphology. The as-synthesized Pd tetrapods have a potential application in the formic acid (HCOOH)-induced reduction of highly toxic hexavalent chromium (Cr(VI)) owing to their improved catalytic performance for the HCOOH decomposition.

MTX/LDHs hybrids synthesized from reverse microemulsions: particle control and bioassay study.

Reverse microemulsions have been used to control the growth of methotrexatum intercalated layered double hydroxides (MTX/LDHs) hybrids, and the influence of reaction temperature, water content (noted as ω) and MTX content (noted as R) on the properties of MTX/LDHs was systematically investigated. The synthesized hybrids were then characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and atomic force microscopy (AFM), etc. XRD and FTIR investigations manifest the successful intercalation of MTX anions into the interlayer of LDHs. The process of particle control has been explored emphatically, and it was found that temperature, water content, and addition of solutes can determine the structural evolution as well as the size of the "water pools" in the reverse microemulsions, while ω plays a critical role in the particle growth. Then in vitro release tests of all hybrids in pH 7.4 phosphate buffered saline (PBS) were explored, and the parabolic diffusion model simulate the release progress best, showing that the release process belongs to multi phase diffusion process via ion exchange. At last, the anticancer efficacy of all MTX/LDHs hybrids was also estimated by MTT assay with the human lung cancer (A549). It is found for the first time that the drug efficacy is closely associated with dispersion coefficient (noted as ϵ).

Hydrothermal synthesis of Pt-Ag alloy nano-octahedra and their enhanced electrocatalytic activity for the methanol oxidation reaction.

The high-quality Pt48Ag52 alloy nano-octahedra are synthesized via one-pot hydrothermal method. The catalytic growth of Ag(0) atoms on Pt nuclei and selective oxidative etching on the Ag(0) atoms contribute to the formation of alloy nano-octahedra. Pt48Ag52 alloy nano-octahedra show excellent electrocatalytic activity and durability for the methanol oxidation reaction (MOR).

Seed-assisted synthesis of Pd@Au core-shell nanotetrapods and their optical and catalytic properties.

The synthesis of noble metal nanostructures with special morphology, structure, composition, and size has been an attractive research area because of their valuable applications in various fields, including optics, electronics, sensing and catalysis. In this work, the first Pd@Au core-shell nanotetrapods (Pd@Au CSNTPs) were synthesized through a facile seeded growth method. Specifically, Pd nanotetrapods were utilized as the substrate for Au coating through chemically reducing HAuCl4 with ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The morphology, composition, and structure of Pd@Au CSNTPs were fully characterized by scanning and transmission electron microscopy, energy dispersive spectroscopy element mapping, X-ray powder diffraction, X-ray photoelectron spectroscopy techniques, etc. Different from conventional spherical Au nanoparticles, the Pd@Au CSNTPs had a very wide surface plasmon resonance (SPR) absorption band in the visible and near-infrared regions (500-1400 nm), showing special SPR absorption features. Meanwhile, the Pd@Au CSNTPs exhibited remarkably enhanced catalytic activity for the hydrogenation reduction of nitro functional groups and the C=N bond because of their specific structural characteristics.

Nitrogen-doped carbon-wrapped porous single-crystalline CoO nanocubes for high-performance lithium storage.

Herein, we have designed and synthesized a novel type of nitrogen-doped carbon-supported CoO nanohybrids, i.e., nitrogen-doped carbon-wrapped porous single-crystalline CoO nanocubes (CoO@N-C nanocubes), by using Co3O4 nanocubes as precursors. Owing to its unique structural features, the as-synthesized CoO@N-C nanocubes demonstrate markedly enhanced anodic performance in terms of reversible capacity, cycling stability, and rate capability, facilitating its application as a high-capacity, long-life, and high-rate anode for advanced lithium-ion batteries.

Highly branched platinum nanolance assemblies by polyallylamine functionalization as superior active, stable, and alcohol-tolerant oxygen reduction electrocatalysts.

The chemical functionalization of platinum (Pt) nanostructures is becoming a new trend in electrocatalysts designs. Meanwhile, highly branched Pt nanostructures are highly exciting electrocatalysts with high activity and stability owing to their specific physical and chemical properties. In this work, the polyallylamine (PAH) functionalized Pt nanolance assemblies (Pt NLAs) have been successfully synthesized by chemical reduction of PAH-Pt(II) complex using formaldehyde (HCHO) in a two-phase water-complex system. The as-prepared Pt NLAs are highly branched and three-dimensionally (3D) interconnected nanostructures, which are composed of many long Pt nanolances in various directions. PAH functionalization improves the electrocatalytic activity of the Pt NLAs for an oxygen reduction reaction (ORR) because of high interface proton concentration on the Pt surface and excellent anti-oxidation ability of the Pt nanolances. Meanwhile, the PAH molecules bound on the Pt NLAs surface act as barrier networks to restrain accessibility of alcohol, exhibiting a high ORR selectivity. In addition, the PAH functionalized Pt NLAs show excellent durability for the ORR due to their particular 3D interconnected structure. The work demonstrates that the PAH functionalized Pt NLAs are indeed promising cathodic electrocatalysts for practical application in direct alcohol fuel cells.

Autocatalysis and selective oxidative etching induced synthesis of platinum-copper bimetallic alloy nanodendrites electrocatalysts.

The controllable synthesis of noble metal alloy nanostructures with highly branched morphology has attracted much attention because of their specific physical and chemical properties. This article reports the synthesis of platinum-copper bimetallic alloy nanodendrites (Pt-Cu BANDs) by a facile, one-pot, templateless, and seedless hydrothermal method in the presence of poly(allylamine hydrochloride) (PAH) and formaldehyde (HCHO). The morphology, composition, and structure of Pt-Cu BANDs are fully characterized by various physical techniques, demonstrating Pt-Cu BANDs are highly alloying, porous, and self-supported nanostructures. The formation/growth mechanism of Pt-Cu BANDs is explored and discussed based on the experimental observations. The autocatalytic growth and interdiffusion are responsible for the formation of Pt-Cu alloy whereas selective oxidative etching results in dendritic morphology of Pt-Cu alloy nanostructures. In addition, the electrocatalytic activity and stability of Pt-Cu BANDs for the methanol oxidation reaction (MOR) are investigated by various electrochemical techniques. The synthesized Pt-Cu BANDs show higher electrocatalytic activity and stability than commercially available Pt black.

Three-dimensional interconnected network of graphene-wrapped porous silicon spheres: in situ magnesiothermic-reduction synthesis and enhanced lithium-storage capabilities.

A novel type of 3D porous Si-G micro/nanostructure (i.e., 3D interconnected network of graphene-wrapped porous silicon spheres, Si@G network) was constructed through layer-by-layer assembly and subsequent in situ magnesiothermic-reduction methodology. Compared with bare Si spheres, the as-synthesized Si@G network exhibits markedly enhanced anodic performance in terms of specific capacity, cycling stability, and rate capability, making it an ideal anode candidate for high-energy, long-life, and high-power lithium-ion batteries.

Multi-generation overgrowth induced synthesis of three-dimensional highly branched palladium tetrapods and their electrocatalytic activity for formic acid oxidation.

Highly branched noble metal nanostructures are highly attractive for catalytic applications owing to their specific physical and chemical properties. In this work, three-dimensional highly branched palladium tetrapods (Pd-THBTs) have been constructed in the presence of polyvinylpyrrolidone (PVP) through one-step hydrothermal reduction of ethylenediamine-tetramethylene phosphonate-palladium(II) (EDTMP-Pd(II)) by formaldehyde. The morphology and structure of the Pd-THBTs were fully characterized and the growth mechanism was explored and discussed based on the experimental observation. The concave Pd tetrahedra grew into highly branched Pd tetrapods consisting of four nanothorn-like branches with tetrahedral dimensions through interesting multi-generation nanocrystal overgrowth. The electrocatalytic activities of the as-synthesized Pd-THBTs toward formic acid oxidation were also studied by cyclic voltammetry and chronoamperometry. The Pd-THBTs showed higher catalytic activity and stability for formic acid oxidation than the commercial Pd black.

A ruthenium(iii) phosphonate complex on polyallylamine functionalized carbon nanotube multilayer films: self-assembly, direct electrochemistry, and electrocatalysis.

On the basis of the electrostatic and donor-acceptor interactions between carboxylated multiwalled carbon nanotubes (MWCNT-COOH) and polyallylamine hydrochloride (PAH), PAH functionalized MWCNT multilayer films ({PAH/MWCNT-COOH}n) were readily formed on a glassy carbon (GC) electrode surface through a layer-by-layer (LBL) self-assembly method. Then, the PAH functionalized MWCNT multilayer films were used as a functional interface to effectively immobilize the ruthenium(iii) ethylenediamine-tetramethylene phosphonate (EDTMP-RuIII) complex through the strong electrostatic and/or hydrogen bonding interactions between -NH2 and -PO3H2 groups. Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) mapping, and Raman measurements were used to characterize the self-assembly process, structure, composition and morphology of the EDTMP-RuIII/{PAH/MWCNT-COOH}n/GC electrode. In the EDTMP-RuIII/{PAH/MWCNT-COOH}n/GC electrode, the immobilized EDTMP-RuIII complex could directly exchange electrons with the substrate electrode and showed excellent electrocatalytic activity towards iodate reduction. Thus, the fabricated EDTMP-RuIII/{PAH/MWCNT-COOH}n/GC electrode could be used as an electrochemical sensor for iodate detection.

Layered graphene nanostructures functionalized with NH2-rich polyelectrolytes through self-assembly: construction and their application in trace Cu(ii) detection.

Layer-by-layer (LBL) self-assembled graphene nanosheets, noncovalently functionalized with evenly spread-NH2 groups attached on the linear polyelectrolyte of polyallylamine hydrochloride (PAH), were produced successfully. The fabrication process consisted of two steps. At first, completely exfoliated graphite oxide (GO) species were highly stacked on the surface of a pretreated glassy carbon electrode as a result of the sequential adsorption of the cationic layer of PAH and the anionic layer of oxygen-containing GO through electrostatic and/or hydrophobic interactions. Then, the GO species were chemically reduced by a strong reducing agent, NaBH4. The structural morphology and electrochemical properties of the as-prepared graphene-based multilayer LBL composite electrodes were thoroughly characterized by techniques such as ultraviolet visible (UV-vis) spectroscopy, high-resolution X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and cyclic voltammetry. Combined with differential pulse anodic stripping voltammetry (DPASV), the obtained -NH2 functional group modified nanocomposite electrodes with highly ordered multilayer superconductive graphene showed improved performance for trace detection of heavy metal ions such as Cu(ii), resulting in sensitive electrochemical sensors. A linear dynamic range from 0.5 to 50 µM for Cu(ii) was obtained under optimized conditions with a relatively low detection limit (S/N = 3) of around 0.35 µM. Our results provide valuable insight for the facile design of highly ordered graphene nanostructures with specific functionality of interest in a vast range, leading to a versatile nanoplatform for environmental or biomedical applications.

Sn-Fe cyanogels noncovalently grafted to carbon nanotubes in a versatile biointerface design: an efficient matrix and a facile platform for glucose oxidase immobilization.

Enzyme immobilization is a powerful strategy adapted to effectively maximize the bioactivity, specificity and stability of an isolated enzyme. In this study, we demonstrate a novel and scalable procedure for facile enzyme immobilization, in which three-dimensional porous Sn-Fe hydrogels were applied to incorporate the enzyme to construct a sensing interface for an amperometric biosensor. The process was initiated from the electrodeposition of Prussian Blue (PB) on multi-walled carbon nanotube (MWCNT)-modified gold electrodes, sequentially capped with tin tetrachloride (SnCl4) solution followed by the addition of a freshly-made homogeneous mixture of enzyme and potassium ferrocyanide solution, leading to instant formation of hydrated three-dimensional (3D) porous Sn-Fe cyanogel networks, deeply set outside the produced rough layer of the MWCNT-PB complexes, providing a desirable microenvironment for the entrapped enzyme. The structural morphology and electrochemical properties of the as-prepared Sn-Fe cyanogels noncovalently grafted to MWCNTs with functionalities of electrodeposited PB were well characterized by scanning electron microscopy (SEM), ultraviolet visible spectroscopy (UV-vis) and cyclic voltammetry. The results indicate that the modified electrode with a multilayer configuration was well-organized, as proposed, and exhibited good electrical conductivity and stable catalytic activity to H2O2 electro-reduction due to the functional layer of PB. When glucose oxidase (GOx) was selected as a model enzyme, the resulting glucose biosensor exhibited a relatively low detection limit of 0.1 µM (S/N 3) with a good sensitivity of 1.68 µA mM-1 cm-2 and improved stability. The results suggest that the Sn-Fe cyanogels, with sufficient interfacial adhesion, hold promise as an attractive support material.

Pt-Pd-Co trimetallic alloy network nanostructures with superior electrocatalytic activity towards the oxygen reduction reaction.

Pt alloy nanostructures show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. Herein, three-dimensional (3D) Pt-Pd-Co trimetallic network nanostructures (TNNs) with a high degree of alloying are synthesized through a room temperature wet chemical synthetic method by using K2 PtCl4 /K3 Co(CN)6 -K2 PdCl4 /K3 Co(CN)6 mixed cyanogels as the reaction precursor in the absence of surfactants and templates. The size, morphology, and surface composition of the Pt-Pd-Co TNNs are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), energy dispersive spectroscopy (EDS), EDS mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The 3D backbone structure, solid nature, and trimetallic properties of the mixed cyanogels are responsible for the 3D structure and high degree of alloying of the as-prepared products. Compared with commercially available Pt black, the Pt-Pd-Co TNNs exhibit superior electrocatalytic activity and stability towards the ORR, which is ascribed to their unique 3D structure, low hydroxyl surface coverage and alloy properties.

Direct electrochemistry of hemoglobin immobilized on the water-soluble phosphonate functionalized multi-walled carbon nanotubes and its application to nitric oxide biosensing.

The direct electron transfer and electrocatalysis of hemoglobin (Hb) immobilized on the phosphonate functionalized multi-walled carbon nanotubes (MWCNTs) are investigated. Fourier transform infrared (FT-IR) spectra, UV-vis spectra and cyclic voltammetry (CV) analyses reveal that the phosphonate functionalized MWCNTs have good biocompatibility for Hb immobilization, and promote the electron communication between Hb and electrode. The immobilized Hb shows a pair of redox peak with a formal potential of -406 ± 10 mV (vs. SCE) and the electrochemical behavior of Hb was a surface-controlled process in a pH 7.0 phosphate buffer solution. And the immobilized Hb can act in an electrocatalytic manner in the electrochemical reduction of nitric oxide (NO). Accordingly, an unmediated NO electrochemical biosensor is constructed. Under optimized experimental conditions, the NO electrochemical biosensor shows the fast response (less than 3s), the wide linear range (1.5 × 10(-7) to 2.7 × 10(-4)M) and the low detection limit (1.5 × 10(-8)M), which is attributed to the good mass transport, the large Hb loading per unit area and the fast electron transfer rate of Hb.

One-pot, water-based and high-yield synthesis of tetrahedral palladium nanocrystal decorated graphene.

This paper reports a facile, water-based and one-pot synthesis of tetrahedral Pd nanocrystals (Pd-TNPs) with high yield and good size monodispersity supported on reduced graphene oxide (RGO) nanosheets via a co-chemical reduction method. The key synthetic strategy employed a positively charged polyallylamine-Pd(II) complex (PAH-Pd(II)) with un-coordinated amine groups as a linker molecule to immobilize Pd(II) species on the negatively charged graphene oxide (GO) surface through electrostatic interaction. As characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) techniques, well-defined Pd-TNPs with an average size of 9 nm were uniformly distributed on the RGO surface. The as-prepared Pd-TNPs/RGO nanohybrid with excellent colloidal stability in aqueous solution exhibits superior catalytic activity towards the degradation of methylene blue (MB) compared to both unsupported Pd-TNPs and Pd black. Thus, the resultant Pd-TNPs/RGO nanohybrid, as a promising heterogeneous catalyst, might have wide potential applications in water-based catalysis systems for the future.

An ultrasensitive iron(III)-complex based hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism.

In this communication, the first nonelectrocatalysis-type hydrogen peroxide electrochemical sensor is reported. The electroactive iron(III) diethylenetriaminepentaacetic acid (DTPA-Fe(III)) complex is immobilized on the cysteamine (cys) modified nanoporous gold (NPG) films by covalent method. The immobilized DTPA-Fe(III) complex quickly communicates an electron with the electrode. Upon addition of hydrogen peroxide, however, hydrogen peroxide inhibits the direct electron transfer of the DTPA-Fe(III) complex due to the generation of nonelectroactive DTPA-Fe(III)-H2O2 complex. Based on quenching mechanism, the first hydrogen peroxide electrochemical sensor based on a nonelectrocatalytic mechanism is developed. The novel hydrogen peroxide electrochemical sensor has the ultralow detection limit (1.0×10(-14) M) and wide linear range (1.0×10(-13) to 1.0×10(-8) M) with excellent reproducibility and stability.

Polyphosphonate induced coacervation of chitosan: encapsulation of proteins/enzymes and their biosensing.

Based on the polyphosphonate-assisted coacervation of chitosan, a simple and versatile procedure for the encapsulation of proteins/enzymes in chitosan-carbon nanotubes (CNTs) composites matrix was developed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrum (EDS) mapping demonstrated the hemoglobin (Hb) uniformly distributed into chitosan-CNTs composites matrix. Raman measurements indicated the CNTs in composites matrix retained the electronic and structural integrities of the pristine CNTs. Fourier transform infrared (FT-IR), ultraviolet-visible (UV-vis) and circular dichroism (CD) spectroscopy displayed the encapsulated Hb preserved their near-native structure, indicating the polyphosphonate-chitosan-CNTs composites possessed excellent biocompatibility for the encapsulation of proteins/enzymes. Electrochemical measurements indicated the encapsulated Hb could directly exchange electron with the substrate electrode. Moreover, the modified electrode showed excellent bioelectrocatalytic activity for the reduction of hydrogen peroxide. Under optimum experimental conditions, the fabricated electrochemical sensor displayed the fast response (less than 3s), wide linear range (7.0×10(-7) to 2.0×10(-3)M) and low detection limit (4.0×10(-7)M) for the determination of hydrogen peroxide. This newly developed protocol was simple and mild and would certainly find extensive applications in biocatalysis, biosensors, bioelectronics and biofuel cells.

Self-assembly of tetrakis (3-trifluoromethylphenoxy) phthalocyaninato cobalt(II) on multiwalled carbon nanotubes and their amperometric sensing application for nitrite.

In this work, the soluble cobalt phthalocyanine functionalized multiwalled carbon nanotubes (MWCNTs) are synthesized by π-π stacking interaction between tetrakis (3-trifluoromethylphenoxy) phthalocyaninato cobalt(II) (CoPcF) complex and MWCNTs. The physical properties of CoPcF-MWCNTs hybrids are evaluated using spectroscopy (UV-vis, XPS, and Raman) and electron microscopy (TEM and SEM). Subsequently, an amperometric nitrite electrochemical sensor is designed by immobilizing CoPcF-MWCNTs hybrids on the glassy carbon electrode. The immobilized CoPcF complex shows the fast electron transfer rate and excellent electrocatalytic activity for the oxidation of nitrite. Under optimum experimental conditions, the proposed nitrite electrochemical sensor shows the fast response (less than 2 s), wide linear range (9.6 × 10(-8) to 3.4 × 10(-4) M) and low detection limit (6.2 × 10(-8) M) because of the good mass transport, fast electron transfer rate, and excellent electrocatalytic activity.