Anchored Pt-Co Nanoparticles on Honeycombed Graphene as Highly Durable Catalysts for the Oxygen Reduction Reaction.

Durability is an important factor in evaluating the performance of a catalyst. In this work, the spatial protection of the carrier to nanoparticles was considered to improve the durability of the catalyst. It is found that a honeycombed graphene with a three-dimensional (3D)-hierarchical porous structure (3D HPG) can help to reduce the shedding of Pt-Co nanoparticles (Pt-Co NPs) because 3D HPG can form a protective layer to reduce the direct erosion of Pt-Co NPs on the interface by an electrolyte. Then, appropriate oxygen groups were introduced on the 3D reduced hierarchical porous graphene oxide (3D rHPGO) to improve the dispersion of Pt-Co NPs on the surface of the carrier. It was found that the Pt d-band of the catalyst was anchored by π sites of carbonyl of an oxygen group. After optimization, the catalyst (referred to as Pt-Co/3D rHPGO) achieved a 2-fold enhancement in mass activity than that of a commercial Pt/C catalyst. More importantly, after the accelerated durability test (ADT) of 20 000 cycles, the Pt-Co/3D rHPGO catalyst can almost sustain this level of performance, whereas other catalysts showed a comparatively large loss of activity. According to the results, the high durability of Pt-Co/3D rHPGO was attributed to spatial protection of Pt-Co NPs and the defects on the surface allowed the electrolyte to enter. In addition, oxygen groups provided an anchoring effect on nanoparticles. Thus, the Pt-Co/3D rHPGO electrocatalyst exhibited splendid durability, holding a potential to be applied in PEMFC for long-term work.

SERRS Detection on Silver Nanoparticles Supported on Acid-Treated Melamine-Resin Microspheres.

Melamine-resin microspheres were synthesized at a pH of 4.0 for 20 min and used as silver nanoparticle (AgNP) carriers for surface enhanced resonant Raman scattering (SERRS) detection. An acetic acid-treatment reaction was introduced into the fabrication of the final substrate. The SERRS performance of the substrate was effectively optimized by regulating excess formaldehyde and experimental parameters, such as acidity, number of treatments and reaction temperature in the acid-treatment reaction. Based on the SERRS detection, it was declared that a trace amount of oligomers with a certain degree of polymerization is necessary for the construction of SERRS hotspots. In addition, it is important to remove excess oligomers with reference to the synthetic reaction of the polymer materials, given the special role of oligomers and the wide application of polymer materials in SERRS detection.

Microporous Layer Containing CeO2-Doped 3D Graphene Foam for Proton Exchange Membrane Fuel Cells at Varying Operating Conditions.

To improve the interfacial mass-transfer efficiency, microporous layers (MPLs) containing CeO2 nanorods and the CeO2 nano-network were prepared for proton exchange membrane fuel cells (PEMFCs). In order to minimize the contact resistance, the three-dimensional (3D) graphene foam (3D-GF) was used as the carrier for the deposition of CeO2 nanorods and the nano-network. The CeO2-doped 3D-GF anchored at the interface between the catalyst layer and microporous layer manufactured several novel functional protrusions. To evaluate the electrochemical property, the normal MPL, the MPL containing raw 3D-GF, and MPLs containing different kinds of CeO2-doped 3D-GF were used to assemble the membrane electrode assemblies (MEAs). Measurements show that the CeO2-doped 3D-GF improved the reaction kinetics of the cathode effectively. In addition, the hydrophilic CeO2-doped 3D-GF worked as the water receiver to prevent the dehydration of MEAs at dry operating condition. Besides, at a high current density or humid operating condition, the CeO2-doped 3D-GF provided the pathway for water removal. Compared with the CeO2 nanorods, the CeO2 nano-network on 3D-GF revealed a higher adaptability at varying operating conditions. Hence, such composition and structure design of MPL is a promising strategy for the optimization of high-performance PEMFCs.

Microporous Layers with Different Decorative Patterns for Polymer Electrolyte Membrane Fuel Cells.

To optimize the interface of the catalyst layer (CL) and gas diffusion layer (GDL) in polymer electrolyte membrane fuel cells (PEMFCs), microporous layers (MPLs) with different decorative patterns were prepared. Carbon paper treated with polytetrafluoroethylene was used as a substrate for the coating of MPLs. To accelerate water removal and gas permeation, ammonium chloride was utilized to improve the porous structure of MPLs. Owing to the recrystallization and pyrolysis of ammonium chloride with different contents, the surface of MPLs exhibited point-, line-, and flowerlike patterns. Membrane electrode assemblies (MEAs) were assembled to evaluate the performance of MPLs with different decorative patterns. From measurements, an MEA containing a porosity-graded MPL (MPL-G) with a flowerlike pattern exhibited the best electrochemical performance. It is because that graded porosity accelerates the removal of excessive water. The flowerlike pattern facilitates the diffusion of the reactant gas at the interface of the catalyst layer and MPL. With the measurement of segmented cell technology, such MEAs revealed an improved redispersion of reactant gases. Furthermore, the produced water was compressed to the gas outlet, providing a larger active region for reaction. These results indicate that pattern design of MPLs is a promising strategy to improve the mass-transfer efficiency at the interface of the catalyst layer and gas diffusion layer.

Controlling reactive pathways in complex one-pot reactions using a novel shape-selective catalyst with multifunctional active-sites.

A new kind of composite zeolite catalyst containing multi-functional reactive-sites located in different nanopores with individual shape-selectivity was successfully applied to two complex one-pot (including both sequential and parallel) reactions. Every kind of reactant molecule was exactly catalyzed only for its desired reaction, thus the reactive pathways were effectively controlled.

Optimizing Melamine Resin Microspheres with Excess Formaldehyde for the SERS Substrate.

Influence of the excess monomer within the synthetic reaction solution of melamine resin microspheres (MFMSs) on the surface-enhanced Raman spectroscopy (SERS) enhancement from Rhodamine 6G (R6G) was investigated, where the R6G was adsorbed on the silver nanoparticles (AgNPs) that were loaded on the MFMSs. Surface characteristics of the MFMSs were modified by the excess monomer (i.e., the excessive melamine or formaldehyde) through its terminal overreaction, which can be simply controlled by some of the synthetic reaction conditions, thus further allowing us to optimize the assembly of the loaded AgNPs for the SERS detection. These SERS substrates incorporating the optimized MFMSs with the excess formaldehyde can also be used for tracing analyses of more environmental and food contaminants.

Ag-nanoparticles on UF-microsphere as an ultrasensitive SERS substrate with unique features for rhodamine 6G detection.

Urea and formaldehyde (UF) microsphere (MS) adsorbing Ag nanoparticles (NPs) was employed as a surface enhanced Raman scattering (SERS) substrate for rhodamine 6G (R6G) detection. The UF MSs and citrate-reduced Ag colloid supplying Ag NPs are synthesized separately and all the subsequent fabrication procedure is then implemented within 2 mL centrifuge tube. Influences of the composition and drying temperature of the UF MSs and the drying method and modification of AgNP/UFMS on the final SERS performance have first been reported. Excess formaldehyde useful in the formation of UF MSs again plays an important role in the SERS detection. Some interesting phenomena in the approach, such as swelling/deswelling of UF MSs and R6G diffusion within hydrophilic environment of UF MSs, are found to be of variable factors affecting the SERS performance. The substrate AgNP/UFMS confidently achieves a detection limit of 10(-13) M R6G and can be used as a simple and effective platform in the SERS spectroscopy.

Role of the excess monomer in the growth of urea and formaldehyde resin deposit particles.

The role of excess monomer (i.e., Urea (U) or Formaldehyde (F)) in UF precipitation reaction was investigated at 28°C. The maximum output of the UF resin deposit was found around the U:F molar ratio 1.0:1.0 and this output decreased if excessive urea (or formaldehyde) was used in the reaction system. The excess monomer was considered to decrease the polymerization degree of UF resin deposit and increased the bonding saturation of its copolymerization monomer as well as the solubility of the UF resin deposit. The Influence of the excess monomer on the lamellar crystallinity of the resultant deposit, involving the polymerization degree and bonding saturation of the monomer, was examined. Three different dynamic regions containing excess monomers were revealed according to the behaviors of the deposit nucleation. The density and water absorption of the UF resin particles were finally demonstrated relative to the dynamic regions in their nucleation reactions.

A seeded synthetic strategy for uniform polymer and carbon nanospheres with tunable sizes for high performance electrochemical energy storage.

We established a novel and facile strategy to synthesize uniform polymer and carbon nanospheres, the diameters of which can be precisely programmed between 35-105 and 30-90 nm, respectively, via time-controlled formation of colloidal seeds. The carbon nanospheres show promising prospects in high rate performance electrochemical energy storage.

Supramolecular core-shell nanosilica@liposome nanocapsules for drug delivery.

The fabrication of core-shell structural nanosilica@liposome nanocapsules as a drug delivery vehicle is reported. SiO(2) nanoparticles are encapsulated within liposomes by a W/O/W emulsion approach to form supramolecular assemblies with a core of colloidal particles enveloped by a lipid bilayer shell. A nanosilica core provides charge compensation and architectural support for the lipid bilayer, which significantly improves their physical stability. A preliminary application of these core-shell nanocapsules for hemoglobin (Hb) delivery is described. Through the H-bonding interaction between the hydroxyl groups on nanosilicas and the amino nitrogens of Hb, Hb-SiO(2) nanocomplexes in which the saturated adsorption amount of Hb on SiO(2) is 0.47 g g(-1) are coated with lipids to generate core-shell Hb-SiO(2)@liposome nanocapsules with mean diameters of 60-500 nm and Hb encapsulation efficiency of 48.4-87.9%. Hb-SiO(2)@liposome supramolecular nanovehicles create a mode of delivery that stabilizes the encapsulated Hb and achieves long-lasting release, thereby improving the efficacy of the drug. Compared with liposome-encapsulated Hb and Hb-loaded SiO(2) particles, such core-shell nanovehicles show substantially enhanced release performance of Hb in vitro. This finding opens up a new window of liposome-based formulations as drug delivery nanovehicles for widespread pharmaceutical applications.

A novel liposome-encapsulated hemoglobin/silica nanoparticle as an oxygen carrier.

A novel liposome-encapsulated hemoglobin/silica nanoparticle (LEHSN) was fabricated by a water-in-oil-in-water (W/O/W) double emulsion approach. Bovine hemoglobin (Hb) was first adsorbed onto the surfaces of silica nanoparticles (SNs), and then the complex of Hb/SNs was encapsulated by liposome to form LEHSN which has a core-shell supramolecular structure. On the one hand, liposomes built a cell membrane-like environment for the controlled release of Hb. On the other hand, SNs which act as rigid core provide a supported framework for lecithin membrane, and enhance the stability of liposomes. In comparison with liposome-encapsulated Hb (LEH), LEHSN shows substantially enhanced stability and improved release property of Hb in vitro. This study highlights the potential of the novel LEHSN as an oxygen carrier for pharmaceutical applications.