A novel PtPd@Pt core/satellite nanoassemblies with a PtPd bimetallic core and a dendritic Pt shell was fabricated via a simple yet efficient L-glutamic acid derived self-assembly method. The obtained PtPd@Pt nanoassemblies exhibit the reinforced catalytic performance in the aspect of activity and stability for the oxygen reduction reaction relative to the commercial Pt black.

Carbon-based materials have recently received increased attention as very promising anode materials for rechargeable lithium-ion batteries (LIBs) because of their non-toxicity, low cost, and excellent performances. Nanostructure engineering has been demonstrated as an effective approach to improve the electrochemical performance of electrode materials. Here, we present a facile and scalable synthesis of two-dimensional (2D) porous graphitic carbon nanosheets embedded by numerous homogeneously dispersed Ni nanoparticles. With both structural and compositional advantages, the as-synthesized nanohybrid manifests a very stable high reversible capacity of 740 mA h g−1 after 100 cycles at a current density of 100 mA g−1, and also excellent rate capability and cycling stability. We believe that the synthetic strategy outlined here can be extended to other rationally designed anode materials with high performances in LIBs.

•High-quality Pt/CeO2/CNTs nanohybrids are synthesized via layer-by-layer assembly.•Pt and CeO2 nanoparticles are homogenously deposited on the CNTs surface.•Pt/CeO2/CNTs exhibit enhanced electrocatalytic activity for methanol oxidation.We successfully synthesize carbon nanotubes (CNTs) supported cerium dioxide and platinum (Pt/CeO2/CNTs) nanohybrids via layer-by-layer assembly. The composition, morphology and structure of the as-prepared Pt/CeO2/CNTs nanohybrids are characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometer (EDX), selected-area electron diffraction (SAED), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission spectrometry (ICP-AES). By comparison of the electrocatalytic properties of the Pt/CeO2/CNTs with the Pt/CNTs, we systematically investigate the promotion effect of CeO2 on the Pt/CeO2/CNTs catalysts towards methanol oxidation. It is found that the introduction of CeO2 not only enhances the electrocatalytic activity and stability of the Pt/CeO2/CNTs catalyst for methanol oxidation but also minimizes the CO poisoning, probably accounting for the good oxygen carrying capacity of CeO2 and its high stability in acidic solution.

Three-dimensional coral-like Pt nanochains (Pt-3DCNCs) are synthesized in high yields by a simple hydrothermal reduction using HCHO as a reductant agent in the presence of NaI but without any other templates or surfactants. The size, composition, and structure of Pt-3DCNCs are inspected by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The controlled experiment show the introduction of NaI is the key influential factor for the formation of the specific structure of Pt-3DCNCs. The as-prepared Pt-3DCNCs show superior electrocatalytic activity and long-term stability towards oxygen reduction reaction, which can be ascribed to their unique structure and the low hydroxyl surface coverage.

•In situ growth of Pd–Pt alloy nanoflowers on reduced graphene oxide is developed.•One-pot polyallylamine hydrochloride-assisted co–chemical reduction is applied.•The supported hybrid nanocatalysts exhibit enhanced performance for methanol oxidation.•Proposed protocol gives insight to design of in situ growth of supported catalysts.In situ growth of Pd–Pt alloy nanoflowers on host reduced graphene oxide (Pd–Pt ANFs/RGO) nanosheets by one–pot polyallylamine hydrochloride-assisted co–chemical reduction method, is developed. Compared with the common approaches to assembly of nanocatalysts in selected substrates based on pre-synthesized catalyst nanoparticles, the in situ fabrication is more facile, cost-effective and environment-friendly, allowing effective control of the location, distribution and uniformity of the supported Pd–Pt nanoflowers through the entire matrix. The detailed morphology, composition and structure of Pd–Pt ANFs/RGO nanocomposites are investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), selected-area electron diffraction (SAED), energy dispersive spectrum (EDS), and nitrogen adsorption–desorption isotherms (SADI). TEM images show that Pd–Pt ANFs are directly grown on RGO with porous structure and good dispersion. Against commercial Pd/C catalyst, Pd–Pt ANFs/RGO nanocomposites show superior electrocatalytic activity, stability and satisfactory CO tolerance towards methanol oxidation reaction in basic electrolyte.Evenly-spread porous Pd–Pt alloy nanoflowers on reduced graphene oxide nanosheets, in situ grown by one-pot polyallylamine hydrochloride-assisted co–chemical reduction method, display markedly enhanced electrocatalytic activity for methanol oxidation towards DMFCs applications.

We report a one-pot hydrothermal route for the successful preparation of three-dimensional (3D) Pd nanochain networks by an arginine-assisted self-assembly process, which show higher electrocatalytic activity and stability than commercial Pd black for the borohydride oxidation reaction due to the unique 3D network structure.

Hollow metallic nanospheres with specific composition in different sizes and shapes have drawn enormous interest due to their strong catalytic activity. In this work, we present an efficient method for facile synthesis of monodispersed Pt hollow nanospheres (Pt-HNSs) using colloidal silica nanoparticles as a sacrificial template. Two steps were involved in the fabrication process. At first, a uniform durable thin layer of anionic PtCl62− was grown on a solid surface of freshly-made polyelectrolyte-modified nano-silica, which has evenly-spread positive charges in the outmost surface, as a result of the sequential adsorption in the order of cationic PDDA [poly(diallyldimethylammonium chloride)], anionic PSS [poly(sodium 4-styrenesulfonate)] and PDDA through electrostatic interaction by a layer by layer (LBL) self assembly. Then, the PtCl62− species were chemically reduced by NaBH4 in the presence of trisodium citrate dehydrate as a complex agent, followed by the chemically removing of the template. The composition, structural morphology and electrocatalytical properties of the as-prepared Pt-HNSs were thoroughly characterized by techniques, such as high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and cyclic voltammetry (CV). The results show that the as-prepared well-dispersed Pt-HNSs with narrow size distribution, exhibit significant catalytic activity to the oxidation of methanol, when compared with that of commercial Pt-black.

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.

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.

•A water-soluble and pH sensitive copolymer of poly(methacrylic acid-co-acrylamide) is used to functionalize carbon nanotubes.•The functionalized carbon nanotubes show good biocompatibility for immobilized redox protein.•The immobilized myoglobin exhibit excellent biocatalytic activity to the electro-reduction of H2O2.•The proposed protocol holds promise as an attractive immobilization method for various copolymer-based biosensors.Poly(methacrylic acid-co-acrylamide) (P(MAA-co-AAM)), noncovalently attached on the surface of multiwalled carbon nanotubes (MWCNTs) through hydrophobic interactions, hydrogen bonding or electrostatic attraction, was employed for the first time as a novel matrix for enzyme immobilization to develop highly sensitive amperometric biosensors. The effective interaction between P(MAA-co-AAM) and MWCNTs, and the structural morphology of the as-prepared P(MAA-co-AAM)–MWCNTs nanocomposite were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Further experimental results show that the solubility and stability of as-prepared P(MAA-co-AAM)–MWCNTs nanocomposites in water are better than that of pristine MWCNTs, and no significant electronic and structural change was observed after functionalization. When myoglobin (Mb) was selected as a model protein, studies by Ultraviolet–visible (UV–vis) and Circular dichroism (CD) spectroscopy indicate that the encapsulated Mb in the as-prepared P(MAA-co-AAM)–MWCNTs nanocomposites, was kept in a near-native state, indicating the P(MAA-co-AAM)–MWCNTs nanocomposites have good biocompatibility for protein/enzyme immobilization. The fabricated electrochemical biosensor based on the immobilized Mb reveals fast response of less than 3 s, wide linear range from 1.47 × 10−6 M to 4.76 × 10−3 M and good detection limit as low as 7.60 × 10−7 M toward the electro-determination of hydrogen peroxide (H2O2) under optimal experimental conditions.Poly(methacrylic acid-co-acrylamide) was employed for noncovalent functionalization of carbon nanotubes. The obtained nanocomposites behave well for myoglobin immobilization with good biocompatibility.

Nanostructured polyurethane (PU) synthesized by an emulsion polymerization with narrow size distribution was employed for the first time directly as a novel matrix for enzyme immobilization to develop sensitively amperometric biosensors. When Microperoxidase-11 (MP-11) was selected as a model protein, the resulting hydrogen peroxide (H2O2) biosensor exhibited improved sensitivity of 29.6 μA mM−1 cm−2 with quite good response time of (1.3 ± 0.4) s and remarkable limit of detection as low as 10 pM (S/N 3) over existing protocols. A linear calibration curve for hydrogen peroxide was obtained up to 1.3 μM under the optimized conditions with a relative low calculated Michaelis–Menten constant (KMapp) (1.87 ± 0.05) μM, which indicated the enhanced enzymatic affinity of MP-11 to H2O2 via PU. The possible interferents had negligible effect on the response current and time of the prepared biosensor. Results suggest that the PU nanoparticles (PU-NPs) with good biocompatibility and sufficient interfacial adhesion hold promise as an attractive support material for construction of ultrasensitive amperometric biosensor.

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.

Hollow metallic nanospheres with specific composition in different sizes and shapes have drawn enormous interest due to their strong catalytic activity. In this work, we present an efficient method for facile synthesis of monodispersed Pt hollow nanospheres (Pt-HNSs) using colloidal silica nanoparticles as a sacrificial template. Two steps were involved in the fabrication process. At first, a uniform durable thin layer of anionic PtCl62− was grown on a solid surface of freshly-made polyelectrolyte-modified nano-silica, which has evenly-spread positive charges in the outmost surface, as a result of the sequential adsorption in the order of cationic PDDA [poly(diallyldimethylammonium chloride)], anionic PSS [poly(sodium 4-styrenesulfonate)] and PDDA through electrostatic interaction by a layer by layer (LBL) self assembly. Then, the PtCl62− species were chemically reduced by NaBH4 in the presence of trisodium citrate dehydrate as a complex agent, followed by the chemically removing of the template. The composition, structural morphology and electrocatalytical properties of the as-prepared Pt-HNSs were thoroughly characterized by techniques, such as high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and cyclic voltammetry (CV). The results show that the as-prepared well-dispersed Pt-HNSs with narrow size distribution, exhibit significant catalytic activity to the oxidation of methanol, when compared with that of commercial Pt-black.

A novel PtPd@Pt core/satellite nanoassemblies with a PtPd bimetallic core and a dendritic Pt shell was fabricated via a simple yet efficient L-glutamic acid derived self-assembly method. The obtained PtPd@Pt nanoassemblies exhibit the reinforced catalytic performance in the aspect of activity and stability for the oxygen reduction reaction relative to the commercial Pt black.

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.