Fast and Controlled Decorating of Metallic Nanoparticles Using Wall‐jet Configuration

A new method to decorate metallic nanoparticles (NPs) based on the wall‐jet configuration was developed. A homemade wall‐jet amperometric cell coupled to an electronic micropipette was used to decorate Pt NPs with Sb and Sn hydrodynamically through the injection of metallic precursor solutions onto an electrode modified with NPs under applied potential. The method allows the control of the coverage degree (θ) by changing easy handling parameters such as injection flow rate, injected volume and concentration of precursors. The decoration procedure is fast, reproducible, simple and economic, since it only uses a few microlitres of precursors to prepare each electrode composition. It is possible to prepare an average of 1000 electrodes using the same amount of precursors for each one prepared by a conventional method using a typical three‐electrode cell. Sb‐ and Sn‐decorated Pt/C NPs were first evaluated towards diluted glucose electrooxidation in buffer solution. These first insights reveal that the output current density increases with θ_Sb and θ_Sn; Sb‐decorated Pt/C shows the greatest improvement.     

Ordered PdCu‐Based Nanoparticles as Bifunctional Oxygen‐Reduction and Ethanol‐Oxidation Electrocatalysts

The development of superior non‐platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen‐reduction reaction (ORR) and liquid fuel oxidation reaction is very important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu‐based nanoparticles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol‐oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni.     

Visible‐Light Photocatalytic Hydrogen Production Activity of ZnIn2S4 Microspheres Using Carbon Quantum Dots and Platinum as Dual Co‐catalysts

ZnIn₂S₄ microspheres (ZIS MSs) were for the first time decorated with carbon quantum dots (CQDs) and platinum nanoparticles (NPs) as dual co‐catalysts of for photocatalytic H₂ production. The ZIS MSs co‐loaded with CQDs and Pt exhibited a high photocatalytic H₂ production rate of 1032.2 μmol h^?1 g^?1 with an apparent quantum efficiency of 2.2 % (420 nm) in triethanolamine aqueous solution under visible‐light irradiation, which was much higher than the respective photocatalytic rates of pure ZIS, Pt loaded ZIS, and CQDs‐decorated ZIS. Such a great enhancement was attributed to the integrative effect of good crystallization, enhanced light absorption, high electrical conductivity of CQDs, and the vectorial electron transfer from ZIS to CQDs and Pt NPs (ZIS→CQDs→Pt).     

Trimetallic Au@PdPt core-shell nanoparticles with ultrathin PdPt skin as highly stable electrocatalysts for the oxygen reduction reaction in acid solution

To design efficient and low-cost core-shell electrocatalysts with an ultrathin platinum shell, the balance between platinum dosage and durability in acid solution is of great importance. In the present work, trimetallic Au@PdPt core-shell nanoparticles(NPs)with Pd/Pt molar ratios ranging from 0.31:1 to 4.20:1 were synthesized based on the Au catalytic reduction strategy and the subsequent metallic replacement reaction. When the Pd/Pt molar ratio is 1.19:1(designated as Au@Pd_(1.19) Pt_1 NPs), the superior electrochemical activity and stability were achieved for oxygen reduction reaction(ORR) in acid solution. Especially, the specific and mass activities of Au@Pd_(1.19) Pt_1 NPs are 1.31 and 6.09 times higher than those of commercial Pt/C catalyst. In addition, the Au@Pd_(1.19) Pt_1 NPs presented a good durability in acid solution. After 3000 potential cycles between 0.1 and 0.7 V(vs. Ag/AgCl), the oxygen reduction activity is almost unchanged. This study provides a simple strategy to synthesize highperformance trimetallic ORR electrocatalyst for fuel cells.     

Self‐Assembly of Amphiphilic Drug–Dye Conjugates into Nanoparticles for Imaging and Chemotherapy

An amphiphilic drug–dye conjugate ( PTX‐Pt‐BDP ) was designed and synthesized with a platinum compound as the hydrophilic head. The precursor of PTX‐Pt‐BDP was obtained under mild conditions by means of a three‐component Passerini reaction. PTX‐Pt‐BDP could self‐assemble into nanoparticles ( PTX‐Pt‐BDP NPs) in aqueous solution via a nanoprecipitation method. The obtained nanoparticles exhibited favorable structural stability in both water and physiological environment. PTX‐Pt‐BDP NPs could be endocytosed by cancer cells as revealed by confocal laser scanning microscopy and exert potent cytotoxicity. This work highlights the potential of nanomedicines from amphiphilic drug–dye conjugates for cancer cell imaging and chemotherapy.     

Reduced Graphene Oxide/Pt Nanoparticles/Zn‐MOF‐74 Nanomaterial for a Glucose Biosensor Construction

In this study, a new glucose biosensor was fabricated by immobilizing glucose oxidase (GOx) on platinum nanoparticles (Pt NPs) decorated reduced graphene oxide (rGO)/Zn‐MOF‐74 hybrid nanomaterial. Herein, the biosensor fused the advantages of rGO with those of porous Zn‐MOF and conductive Pt NPs. This has not only enlarged the surface area and porosity for the efficient GOx immobilization and faster mass transport, but also provided favorable electrochemical features such as high current density, remarkable electron mobility through metal nanoparticles, and improved electron transfer between the components. The GOx‐rGO/Pt NPs@Zn‐MOF‐74 coated electrode displayed a linear measurement range for glucose from 0.006 to 6 mM, with a detection limit of 1.8 μM (S/N: 3) and sensitivity of 64.51 μA mM^?1 cm^?2. The amperometric response of the enzyme biosensor demonstrated the typical behavior of Michaelis‐Menten kinetics. The obtained satisfying sensitivity and measurement range enabled fast and accurate glucose measurement in cherry juice using the fabricated biosensor. The water‐stable Zn‐MOF‐74 demonstrated higher enzyme loading capacity and can be potent supporting material for biosensor construction.     

Low‐Pt Loaded on a Vanadium Nitride/Graphitic Carbon Composite as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

The high cost of platinum electrocatalysts for the oxygen reduction reaction (ORR) has hindered the commercialization of fuel cells. An effective support can reduce the usage of Pt and improve the reactivity of Pt through synergistic effects. Herein, the vanadium nitride/graphitic carbon (VN/GC) nanocomposites, which act as an enhanced carrier of Pt nanoparticles (NPs) towards ORR, have been synthesized for the first time. In the synthesis, the VN/GC composite could be obtained by introducing VO₃^? and [Fe(CN)₆]^4? ions into the polyacrylic weak‐acid anion‐exchanged resin (PWAR) through an in‐situ anion‐exchanged route, followed by carbonization and a subsequent nitridation process. After loading only 10 % Pt NPs, the resulting Pt‐VN/GC catalyst demonstrates a more positive onset potential (1.01 V), higher mass activity (137.2 mA mg^?1), and better cyclic stability (99 % electrochemical active surface area (ECSA) retention after 2000 cycles) towards ORR than the commercial 20 % Pt/C. Importantly, the Pt‐VN/GC catalyst mainly exhibits a 4 e^?‐transfer mechanism and a low yield of peroxide species, suggesting its potential application as a low‐cost and highly efficient ORR catalyst in fuel cells.     

Polymerization of graphene oxide nanosheet by using of aminoclay: Electrocatalytic activity of its platinum nanohybrids

This study describes the polymerization of graphene oxide (GO) nanosheet to reduced‐GO‐aminoclay (RGC) by covalent functionalization of chemically reactive epoxy groups on the basal planes of GO with amine groups of magnesium phyllosilicate clay (known as aminoclay). The resulting RGC sheets were characterized and applied to support platinum nanostructures at toluene/water interface. Pt nanoparticles (NPs) with diameters about several nanometers were adhered to RGC sheets by chemical reduction of [PtCl₂(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) complex. Catalytic activity of Pt NPs thin films were investigated in the methanol oxidation reaction. Cyclic voltammetry results exhibit that the Pt/reduced‐GO (RGO) and Pt/RGC thin films showed improved catalytic activity in methanol oxidation reaction in comparison to other Pt NPs thin films, demonstrating that the prepared Pt/RGO and Pt/RGC thin films are promising catalysts for direct methanol fuel cell.     

Platinum‐Free Binary Co‐Ni Alloy Counter Electrodes for Efficient Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSSCs) have attracted growing interest because of their application in renewable energy technologies in developing modern low‐carbon economies. However, the commercial application of DSSCs has been hindered by the high expenses of platinum (Pt) counter electrodes (CEs). Here we use Pt‐free binary Co‐Ni alloys synthesized by a mild hydrothermal strategy as CE materials in efficient DSSCs. As a result of the rapid charge transfer, good electrical conduction, and reasonable electrocatalysis, the power conversion efficiencies of Co‐Ni‐based DSSCs are higher than those of Pt‐only CEs, and the fabrication expense is markedly reduced. The DSSCs based on a CoNi_0.25 alloy CE displays an impressive power conversion efficiency of 8.39 %, fast start‐up, multiple start/stop cycling, and good stability under extended irradiation.     

β‐Cyclodextrin‐Platinum Nanoparticles/Graphene Nanohybrids: Enhanced Sensitivity for Electrochemical Detection of Naphthol Isomers

Naphthol isomers, including α‐naphthol (α‐NAP) and β‐naphthol (β‐NAP), are used widely in various fields and are harmful to the environment and human health. The qualitative and quantitative determination of naphthol isomers is therefore of great significance. Herein, β‐cyclodextrin (β‐CD)‐platinum nanoparticles (Pt NPs)/graphene nanosheets (GNs) nanohybrids (β‐CD‐PtNPs/GNs) were prepared for the first time using a simple wet chemical method and characterized by atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and electrochemical methods, and then applied successfully in the ultrasensitive electrochemical detection of naphthol isomers. The results show that the oxidation peak currents of naphthol isomers obtained at the glassy carbon (GC) electrode modified with β‐CD‐PtNPs/GNs are much higher than those at the β‐CD/GNs/GC, PtNPs/GNs/GC, GNs/GC, and bare GC electrodes. Additionally, compared with other electrochemical sensors developed previously, the proposed electrode results in improved detection limits of about one order of magnitude for α‐NAP (0.23 nM ) and three orders of magnitude for β ‐NAP (0.37 nM ).     

Protein-associated water and secondary structure effect removal of blood proteins from metallic substrates

Removing adsorbed protein from metals has significant health and industrial consequences. There are numerous protein-adsorption studies using model self-assembled monolayers or polymeric substrates but hardly any high-resolution measurements of adsorption and removal of proteins on industrially relevant transition metals. Surgeons and ship owners desire clean metal surfaces to reduce transmission of disease via surgical instruments and minimize surface fouling (to reduce friction and corrosion), respectively. A major finding of this work is that, besides hydrophobic interaction adhesion energy, water content in an adsorbed protein layer and secondary structure of proteins determined the access and hence ability to remove adsorbed proteins from metal surfaces with a strong alkaline-surfactant solution (NaOH and 5 mg/mL SDS in PBS at pH 11). This is demonstrated with three blood proteins (bovine serum albumin, immunoglobulin, and fibrinogen) and four transition metal substrates and stainless steel (platinum (Pt), gold (Au), tungsten (W), titanium (Ti), and 316 grade stainless steel (SS)). All the metallic substrates were checked for chemical contaminations like carbon and sulfur and were characterized using X-ray photoelectron spectroscopy (XPS). While Pt and Au surfaces were oxide-free (fairly inert elements), W, Ti, and SS substrates were associated with native oxide. Difference measurements between a quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance spectroscopy (SPR) provided a measure of the water content in the protein-adsorbed layers. Hydrophobic adhesion forces, obtained with atomic force microscopy, between the proteins and the metals correlated with the amount of the adsorbed protein-water complex. Thus, the amount of protein adsorbed decreased with Pt, Au, W, Ti and SS, in this order. Neither sessile contact angle nor surface roughness of the metal substrates was useful as predictors here. All three globular proteins behaved similarly on addition of the alkaline-surfactant cleaning solution, in that platinum and gold exhibited an increase, while tungsten, titanium, and stainless steel showed a decrease in weight. According to dissipation measurements with the QCM-D, the adsorbed layer for platinum and gold was rigid, while that for the tungsten, titanium, and stainless steel was much more flexible. The removal efficiency of adsorbed-protein by alkaline solution of SDS depended on the water content of the adsorbed layers for W, Ti, and SS, while for Pt and Au, it depended on secondary structural content. When protein adsorption was high (Pt, Au), protein-protein interactions and protein-surface interactions were dominant and the removal of protein layers was limited. Water content of the adsorbed protein layer was the determining factor for how efficiently the layer was removed by alkaline SDS when protein adsorption was low. Hence, protein-protein and protein-surface interactions were minimal and protein structure was less perturbed in comparison with those for high protein adsorption. Secondary structural content determined the efficient removal of adsorbed protein for high adsorbed amount.     

CO and methanol adsorption on (2 × 1)Pt(110) and ion‐eroded Pt(111) model catalysts

Methanol adsorption on ion‐sputtered Pt(111) surface exhibiting high concentration of vacancy islands and on (2 × 1)Pt(110) single crystal were investigated by means of photoelectron spectroscopy (PES) and thermal desorption spectroscopy. The measurements showed that methanol adsorbed at low temperature on sputtered Pt(111) and on (2 × 1)Pt(110) surfaces decomposed upon heating. The PES data of methanol adsorption were compared to the data of CO adsorbed on the same Pt single crystal surfaces. In the case of the sputtered Pt(111) surface, the dehydrogenation of H_xCO intermediates is followed by the CO bond breakage. On the (2 × 1)Pt(110) surface, carbon monoxide, as product of methanol decomposition, desorbed molecularly without appearance of any traces of atomic carbon. By comparing both platinum surfaces we conclude that methanol decomposition occurs at higher temperature on sputtered Pt(111) than on (2 × 1)Pt(110). Copyright © 2010 John Wiley & Sons, Ltd.     

Small‐Sized Tungsten Nitride Particles Strongly Anchored on Carbon Nanotubes and their Use as Supports for Pt for Methanol Electro‐oxidation

The anchoring of small‐sized WN (tungsten nitride) nanoparticles (NPs) with good dispersion on carbon nanotubes (CNTs) offers an effective means of obtaining promising materials for use in electrocatalysis. Herein, an effective method based on grinding treatment followed by a nitridation process is proposed to realize this goal. In the synthesis, a solution containing H₄[SiO₄(W₃O₉)₄] (SiW₁₂) and CNTs modified with polyethylenimine (PEI‐CNTs) was ground to dryness. Small‐sized WN NPs were anchored onto the CNTs with good dispersion after calcination under NH₃. Under hydrothermal assembly conditions (absence of grinding), WN particles of larger size and with inferior dispersion were obtained, demonstrating the important role of the grinding process. The benefit of the small‐sized WN has been demonstrated by using WN/CNTs as a support for Pt to catalyze the methanol electro‐oxidation reaction. The mass activity of Pt‐WN/CNTs‐G‐70 (where G denotes the grinding treatment, and 70 is the loading amount (%) of WN in the WN/CNTs) was evaluated as about 817 mA mg^?1_Pt, better that those of commercial Pt/C (340 mA mg^?1_Pt) and Pt/CNTs (162 mA mg^?1_Pt). The Pt‐WN/CNTs‐G also displayed good CO tolerance. In contrast, Pt‐WN/CNTs prepared without the grinding process displayed an activity of 344 mA mg^?1_Pt, verifying the key role of grinding treatment in the preparation of WN/CNTs with good co‐catalytic effect.     

Micro‐/Mesoporous Platinum–SiCN Nanocomposite Catalysts (Pt@SiCN): From Design to Catalytic Applications

The synthesis, characterization, and catalytic studies of platinum (Pt) nanoparticles (NPs) supported by a polymer‐derived SiCN matrix are reported. In the first step and under mild conditions (110 °C), a block copolymer (BCP) based on hydroxyl‐group‐terminated linear polyethylene (PEOH) and a commercially available polysilazane (PSZ: HTT 1800) were synthesized. Afterwards, the BCP was microphase separated, modified with an aminopyridinato (Ap) ligand‐stabilized Pt complex, and cross‐linked. The green bodies thus obtained were pyrolyzed at 1000 °C under nitrogen and provided porous Pt@SiCN nanocomposite via decomposition of the PEOH block while Pt nanoparticles grew in situ within the SiCN matrix. Powder X‐ray diffraction (PXRD) studies confirmed the presence of the cubic Pt phase in the amorphous SiCN matrix whereas transmission electron microscopy (TEM) measurements revealed homogeneously distributed Pt nanoparticles in the size of 0.9 to 1.9 nm. N₂ sorption studies indicated the presence of micro‐ and mesopores. Pt@SiCN appears to be an active and robust catalyst in the hydrolysis of sodium borohydride under harsh conditions.     

Silver–platinum core–shell nanoparticles for surface-enhanced Raman spectroscopy

Core–shell Ag@Pt nanoparticles have been synthesised by the means of seed-growth reaction including reduction of PtCl₄²⁻ with silver and replacing Ag atoms with Pt. Surface-enhanced Raman scattering (SERS) spectra of pyridine (which gives slightly different spectra when interacting with various metals) adsorbed on synthesised Ag@Pt clusters were measured. SERS measurements have revealed that deposition of the platinum layer causes near elimination of the spectral interferences from pyridine directly interacting with the silver core. The average SERS enhancement factor for pyridine adsorbed on the Ag@Pt clusters was estimated as equal to about 10³–10⁴, significantly higher than the SERS enhancement factor achievable on the pure platinum nanostructures. Using the silver core (instead of the previously used gold cores) allows for measurement of strong SERS spectra on the Pt covered nanostructures for the wider range of the excitation radiation. This procedure of platinum deposition was tested with various silver nanoparticles – produced with borohydride, citrate and citrate/borohydride methods – which substantially differ in size distribution. The application of formed Ag@Pt structures for obtaining intense Raman spectra for molecules adsorbed on only slightly modified platinum surfaces is discussed.     

Designed Synthesis of Well‐Defined Pd@Pt Core–Shell Nanoparticles with Controlled Shell Thickness as Efficient Oxygen Reduction Electrocatalysts

Improving the electrocatalytic activity and durability of Pt‐based catalysts with low Pt content toward the oxygen reduction reaction (ORR) is one of the main challenges in advancing the performance of polymer electrolyte membrane fuel cells (PEMFCs). Herein, a designed synthesis of well‐defined Pd@Pt core–shell nanoparticles (NPs) with a controlled Pt shell thickness of 0.4–1.2 nm by a facile wet chemical method and their electrocatalytic performances for ORR as a function of shell thickness are reported. Pd@Pt NPs with predetermined structural parameters were prepared by in situ heteroepitaxial growth of Pt on as‐synthesized 6 nm Pd NPs without any sacrificial layers and intermediate workup processes, and thus the synthetic procedure for the production of Pd@Pt NPs with well‐defined sizes and shell thicknesses is greatly simplified. The Pt shell thickness could be precisely controlled by adjusting the molar ratio of Pt to Pd. The ORR performance of the Pd@Pt NPs strongly depended on the thickness of their Pt shells. The Pd@Pt NPs with 0.94 nm Pt shells exhibited enhanced specific activity and higher durability compared to other Pd@Pt NPs and commercial Pt/C catalysts. Testing Pd@Pt NPs with 0.94 nm Pt shells in a membrane electrode assembly revealed a single‐cell performance comparable with that of the Pt/C catalyst despite their lower Pt content, that is the present NP catalysts can facilitate low‐cost and high‐efficient applications of PEMFCs.     

Synthesis of Ultrafine Mesoporous Tungsten Carbide by High‐energy Ball Milling and Its Electrocatalytic Activity for Methanol Oxidation

Ultrafine mesoporous tungsten carbide (WC) was prepared from as‐synthesized mesoporous WC using high‐energy ball milling treatment. X‐ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption‐desorption techniques were used to characterize the samples. Brunauer‐Emmett‐Teller (BET) surface areas of WC samples increased with the increasing ball milling time and kept constant at 10–11 m²·g^?1 for over 9 h. The electrocatalytic properties of methanol electro‐oxidation at WC powder microelectrodes were investigated by cyclic voltammetry, chronoamperometry, and quasi‐steady‐state polarization techniques. The results reveal that ball‐milled WC exhibits higher activity for methanol electro‐oxidation than as‐synthesized mesoporous WC. The suitability of ball‐milled WC for methanol electro‐oxidation is better than platinum (Pt) micro‐disk, although the current peak is not as high as the Pt micro‐disk. Moreover, increasing the methanol concentration and reaction temperature promotes methanol electro‐oxidation on ultrafine mesoporous WC.     

The Influence of Surface Composition of Nanoparticles on their Interactions with Serum Albumin

Interactions between differently functionalised silver and gold nanoparticles (NPs) as well as polystyrene nanoparticles with bovine serum albumin (BSA) are studied using circular dichroism (CD) spectroscopy. It is found that the addition of NPs to the protein solution destroys part of the helical secondary structure of the protein as a result of surface adsorption. From the loss of free protein and hence the extent of their structural change adsorption equilibrium constants are derived. The results reveal that citrate‐coated gold and silver NPs exhibit much stronger interactions with BSA than polymeric or polymer‐coated metallic NPs. It is therefore concluded that for the particles considered, the influence of surface composition on the interaction behaviour dominates that of the core.     

Ultrafine Molybdenum Carbide Nanoparticles Composited with Carbon as a Highly Active Hydrogen‐Evolution Electrocatalyst

The replacement of platinum with non‐precious‐metal electrocatalysts with high efficiency and superior stability for the hydrogen‐evolution reaction (HER) remains a great challenge. Herein, we report the one‐step synthesis of uniform, ultrafine molybdenum carbide (Mo₂C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo₂C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1–3 layers) showed superior HER activity in acidic media, with a very low onset potential of ?6 mV, a small Tafel slope of 41 mV dec^?1, and a large exchange current density of 0.179 mA cm^?2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state‐of‐the‐art 20 % Pt/C and make the catalyst one of the most active acid‐stable electrocatalysts ever reported for HER.     

Synthesis of Silver and Gold Nanoparticles by a Novel Electrochemical Method

Spherical silver and gold nanoparticles with narrow size distributions were conveniently synthesized in aqueous solution by a novel electrochemical method. The technological keys to the electrochemical synthesis of monodispersed metallic nanoparticles lie in the choice of an ideal stabilizer for the metallic nanoclusters and the use of a rotating platinum cathode. Poly(N‐vinylpyrrolidone) (PVP) was chosen as the stabilizer for the silver and gold clusters. PVP not only protects metallic particles from agglomeration, but also promotes metal nucleation, which tends to produce small metal particles. Using a rotating platinum cathode effectively solves the technological difficulty of rapidly transferring the (electrochemically synthesized) metallic nanoparticles from the cathode vicinity to the bulk solution, avoiding the occurrence of flocculates in the vicinity of the cathode, and ensuring the monodispersity of the particles. The particle size and particle size distribution of the silver and gold nanoparticles were improved by adding sodium dodecyl benzene sulfonate (SDBS) to the electrolyte. The electrochemically synthesized nanoparticles were characterized by TEM and UV/Vis spectroscopy.