Fabrication, annealing, and electrocatalytic properties of platinum nanoparticles supported on self-organized TiO_2 nanotubes

The platinum nanoparticles supported on self-organized TiO2 nanotubes （Pt-TiO2/Ti） were prepared using electrochemical anodic oxidation followed by cathodic reduction. The structure and chemical nature of the Pt-TiO2/Ti electrocatalyst were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Both XRD and SEM results indicate the presence of platinum on nanotubular TiO2. The stability of the Pt deposits was also investigated in 0.5 mol/L H2SO4 solution by cyclic voltammetry. The electrocatalytic activity of the Pt-TiO2/Ti catalyst exhibits enhancement effect during electro-oxidation of methanol when annealed to anatase. Successive cyclic voltam- mograms of methanol oxidation on the Pt-TiO2/Ti electrocatalyst shows unique electrocatalytic characteristics when compared to methanol oxidation on the bulk Pt catalyst. This is because of further quick oxidation of adsorbed CO by Pt （111） facets of Pt particles on self-organized TiO2 nanotubes when the formation of an electroactive film onto the working catalyst surface occurs.

Mesoporous silica decorated with platinum nanoparticles for drug delivery and synergistic electrodynamic-chemotherapy

Electrodynamic therapy(EDT)is a conceptually new cancer treatment approach recently proposed by our group.During EDT,the electro-driven catalytic reaction would occur on the surface of platinum nanoparticles(PtNPs)to produce reactive oxygen species(ROS)under the direct current(DC)or square-wave alternating current(AC)electric field.To further extend the potential of EDT,we hereby designed mesoporous silica-based nanocomposites decorated with PtNPs and loaded with anticancer drug doxorubicin(DOX)for synergistic electrodynamic-chemotherapy.Such silica-based nanocomposites could enable homogenous killing of large-sized tumors(over 500 mm^3)and realize remarkable tumor destruction efficacy at a relatively low quantity of electricity.To our best knowledge,this is the first study to combine EDT and chemotherapy to develop a synergetic nanoplatform,openning a new dimension for the design of other EDT-based anticancer strategies.

Electrochemical determination of quercetin by self-assembled platinum nanoparticles/poly(hydroxymethylated-3,4-ethylenedioxylthiophene) nanocomposite modified glassy carbon electrode

A simple and sensitive platinum nanoparticles/poly（hydroxymethylated-3,4-ethylenedioxylthiophene） nanocomposite （PtNPs/PEDOT-MeOH） modified glassy carbon electrode （GCE） was successfully developed for the electrochemical determination of quercetin. Scanning electron microscopy and energy dispersive X-ray spectroscopy results indicated that the PtNPs were inserted into the PEDOT- MeOH layer. Compared with the bare GCE and poly（3,4-ethylenedioxythiophene） （PEDOT） electrodes, the PtNPs/PEDOT-MeOH/GCE modified electrode exhibited a higher electrocatalytic ability toward the oxidation of quercetin due to the synergic effects of the electrocatalytic activity and strong adsorption ability of PtNPs together with the good water solubility and high conductivity of PEDOT-MeOH. The electrochemical sensor can be applied to the quantification of quercetin with a linear range covering 0.04-91μmol L-1 and a low detection limit of 5.2 nmol L-1. Furthermore, the modified electrode also exhibited good reoroducibilitv and long-term stability, as well as high selectivity.

Platinum nanoparticles promote breast cancer cell metastasis by disrupting endothelial barrier and inducing intravasation and extravasation

Breast cancer is a common malignancy in women with disappointing prognosis especially the triple-negative subtype.Recently,nanomedicine becomes a promising therapeutic strategy for breast cancer,such as platinum nanoparticles(PtNPs).Despite the promising anticancer effects of PtNPs,the safety of PtNPs remains to be fully evaluated.Herein,a series of cell and animal experiments demonstrate that PtNPs facilitate breast cancer metastasis by damaging the vascular endothelial barrier.PtNPs disrupt endothelial cell proliferation,migration and tube-like structure formation,destruct endothelial adhesions junctions and induce endothelial barrier leakiness in vitro most likely by stimulating intracellular reactive oxygen species(ROS)generation and altering the expression and conformation of endothelial junctional proteins,thus promoting intravasation and extravasation of the implanted 4T1 breast cancer cells and leading to cancer metastasis in female BALB/c nude mice in vivo.In addition,smaller PtNPs(5 nm)are more potent than larger PtNPs(70 nm)in exerting the above effects.The study provides the first evidence that PtNPs can promote breast cancer metastasis by damaging endothelial barrier.The unexpected detrimental effects of PtNPs should be considered in future nanomedicine designs for the treatment of breast cancer.

Immobilization of Hemoglobin on Platinum Nanoparticles-Modified Glassy Carbon Electrode for H_2O_2 Sensing

This work described an amperometric hydrogen peroxide （H2O2） biosensor based on immobilization of hemoglobin （Hb） on a glassy carbon （GC） electrode modified by platinum nanoparticles, which was prepared by an in situ chemical reductive growth method. The electrochemical impedance measurements confirmed that the Hb was immobilized on the platinum nanoparticles-modified glassy carbon surface and has a synergistic effect with platinum nanoparti- cles in improving the catalytic reduction of H2O2. The Hb immobi- lized platinum nanoparticles-modified GC （Hb/Pt/GC） electrode displays an effective catalytic response to the reduction of H2O2. A linear dependence of the catalytic current versus H2O2 concentration was obtained in the range of 5.0×10 6 to 4.5×10^-4 mol·L^-1 with a detection limit （S/N=3） of 7.4×10^-7 mol·L-1.

Elaboration and Properties of Nanocomposite Structures Based on Crown Modified Platinum Nanoparticles

1 Results This paper presents the development of platinum nanocomposites structures based on organically modified c.a.2 nm core platinum nanoparticles.The chemical modification of the 4-mercaptoaniline functionalized particles by various in coming molecules is evidenced and precisely quantified.The particles can be dissolved like molecules in various solvents depending on the features of the new crown and X-rays shows that the interparticle distance is affected by the crown modification.These platinum n...

Preparation of Multiwall Carbon Nanotubes-supported High Loading Platinum for Vehicular PEMFC Application

Multiwall carbon nanotube-supported Pt （Pt/MWNTs） catalysts with high dispersion and high loading of Pt were prepared by chemical reduction method and the loading of Pt got to 40 wt%. The average diameter of Pt nanoparticles on MWNTs was about 3.5 nm. When the hydrogen and air were used as reactant gases for PEMFC, Pt/MWNTs catalysts showed significantly higher performance than the Pt/XC-72 （carbon black） catalysts.

Porous Pt nanoparticles for cancer photothermal therapy

OBJECTIVE Plasmonic nanostructures act as a type of promising candidate for cancer photothermal therapy.These photothermal agents with good biocompatibility and high photothermal conversion efficiency are highly desirable.In the present study,we synthesized poly(diallyldimethylammonium chloride)(PDDAC)coated porous platinum(Pt)nanoparticles for photothermal therapy.METHODS Biocompatibility and cellular uptake of Pt nanoparticles were studied in human glioblastoma U-87 MG cells.Cell viability was evaluated by ATP assay and calcein AM staining.The photothermal therapeutic effect of the Pt nanoparticles was studied under 808-nm laser irradiation.In addition,the synergistic anti-cancer effect of the Pt nanoparticle-based photothermal therapy and doxorubicinwas investigated.RESULTS The as-prepared Pt nanoparticles exhibited considerable photothermal conversion efficiency under 809 nm and 980 nm laser irradiation.In vitro study indicated that the Pt nanoparticles displayed good biocompatibility and high cellular uptake efficiency.In the presence of the Pt nanoparticles,808-nm laser irradiation at 8.4 W·cm-2for3 min induces significant cytotoxicity,and cell necrosis is involved in the photothermal injury.Furthermore,simultaneousapplication of photothermal therapy synergistically enhances the cytotoxicity of anticancer drug doxorubicin.CONCLUSION Therefore,PDADMAC-coated Pt nanoparticles will have great potential in cancer photothermal therapy.

CATALYTIC PROPERTIES OF POLYMER-STABILIZED COLLOIDAL METAL NANOPARTICLES SYNTHESIZED BY MICROWAVE IRRADIATION

Catalytic properties of polymer-stabilized colloidal metal nanoparticles synthesized by microwave irradiationwere studied in the selective hydrogenation of unsaturated aldehydes,o-chloronitrobenzene and the hydrogenationof alkenes.The results show that nanosized metal particles synthesized by microwave irradiation have similar catalyticperformance in selective hydrogenation of unsaturated aldehydes,better selectivity to o-chloroaniline in hydrogenation ofo-chloronitrobenzene and higher catalytic activities in hydrogenation of alkenes,compared with metal clusters prepared byconventional heating.The same apparent activation energy(E_a=29 kJ mol^(-(?)) for hydrogenation of (?)-heptene catalyzed withplatinum nanoparticles prepared by both heating modes implied that the reaction followed the same mechanism.

Construction of Au@Pt core-satellite nanoparticles based on in-situ reduction of polymeric ionic liquid protected gold nanoparticles

A method of in-situ reduction to prepare Au@Pt core-satellite nanopar- ticles （NPs） is described by using Au NPs coating poly[1-methyl 3-（2-methacryloyloxy propylimidazolium bromine）] （PMMPImB-@-Au NPs） as the template. After electrostatic complex chloroplatinic acid with PMMPImB shell, the composite NP was directly reduced with N2H4 to produce Au@Pt core-satellite NPs. The characterization of composite and core-satellite NPs under different amounts of chloroplatinic acid were studied by DLS, UV-vis absorption spectrum and TEM. The satellite Pt NPs with a small size （-2 nm） dotted around Au core, and the resulting Au@Pt core-satellite NPs showed a red-shift surface plasmon resonance （SPR） and a good dispersion due to effectively electrostatic repulsion providing by the polymeric ionic liquid （PIL） shell. Finally, Au@Pt core-satellite NPs exhibit an enhanced catalytic activity and cycled catalytic capability for the reduction ofp- nitrophenol with NaBH4.

An acetic acid refluxing-electrochemistry combined strategy to activate supported-platinum electrocatalysts

Surfactant removal from the surface of platinum-based nanoparticles prepared using solution-based methods is a prerequisite to realize their high catalytic performance for electrochemical reactions. Herein, we report an effective approach combining acetic acid refluxing with an electrochemical process for the removal of amine- or thiol-based capping agents from the surface of supported-platinum nanoparticles. This strategy involves surfactant protonation by refluxing the supported-platinum particles in acetic acid followed by surfactant removal by subsequent electrochemical treatment at high potential. We demon- strate that this combined activation process is essential to enhance platinum particle performance in catalyzing direct methanol fuel cell reactions, including methanol oxidation and oxygen reduction reac- tions. The studies in this work show promise in electrocatalysis applications of solution-based materials synthesis.

Size contrast of Pt nanoparticles formed on neighboring domains within suspended and supported graphene

The relatively small size of thin （one or few layers） graphene flakes makes it extremely difficult to study the behavior of suspended graphene by characterization techniques other than the electron microscopies. Herein, we exploited the capability of spatially resolved photoemission in combination with high resolution transmission electron microscopy to investigate the interaction of thermally evaporated Pt atoms on suspended and supported graphene. Spectroscopic and microscopic analyses reveal that the nucleation of nanometer- sized Pt particles in these two regions exhibit different trends. While only small nanometer-sized islands are present on the supported graphene, relatively larger clusters of islands were also found on the suspended flakes. The X-ray photoemission C ls core levels acquired after the Pt deposition show an increase in the number of vacancies in the graphene sheets.

Denatured proteins as a novel template for the synthesis of well-defined,ultra-stable and water-soluble metal nanostructures for catalytic applications

The templated synthesis of noble metal nanoparticles using biomass,such as proteins and polysaccharides,has generated great interest in recent years.In this work,we report on denatured proteins as a novel template for the preparation of water-soluble metal nanoparticles with excellent stability even after high speed centrifugation or storage at room temperature for one year.Different noble metal nanoparticles including spherical gold and platinum nanoparticles as well as gold nanoflowers are obtained using sodium borohydride or ascorbic acid as the reducing agent.The particle size can be controlled by the concentration of the template.These metal nanoparticles are further used as catalysts for the hydrogenation reaction of p-nitrophenol to p-aminophenol.Especially,spherical gold nanoparticles with an average size of 2 nm show remarkable catalytic performance with a rate constant of 1.026×10^(-2) L s^(-1) mg^(-1).These metal nanoparticles with tunable size and shape have great potential for various applications such as catalysis,energy,sensing,and biomedicine.