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.

Platinum Nanoparticles Supported on Graphite Nanofibers Prepared by Microwave Irradiation and Its Electrocatalytic Activity

Platinum nanoparticles supported on graphite nanofibers (GNFs) were prepared bymicrowave assistant heating polyol process. TEM images showed that microwave prepared Ptnanoparticles supported on GNFs were small and uniform, and the average diameter was about 3.4nm. Cyclic voltammetric test showed that Pt/GNFs exhibited very high electrocatalytic activity formethanol oxidation.

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 supported MoS2 nanosheet for simultaneous detection of dopamine and uric acid

Herein, platinum nanoparticles-decorated molybdenum disulfide （PtNPs@MoS2） nanocomposite has been synthesized via a microwave-assisted hydrothermal method, which was characterized by transmission electron microscopy （TEM） and powder X-ray diffraction （XRD）. This MoSz-based nanocomposite modified glass carbon electrode （PtNPs@MoSz/GCE） exhibited excellent electrocatalytic activity toward dopamine （DA） and uric acid （UA） due to their synergistic effect. Two well-defined oxidation peaks of DA and UA were obtained at PtNPs@MoS2/GCE with a large peak separation of 160 mV （DA-UA）, sug- gesting that the modified electrode could individually or simultaneously analyze DA and AA. Under the optimal conditions, the peak currents of DA and UA were linearly dependent on their concentrations in the range of 0.5-150 and 5-1000 gmol/L with detection limit of 0.17 and 0.98 gmol/L, respectively. The proposed MoSz-based sensor can also be employed to examine DA and UA in real samples with satisfactory results. Therefore, the PtNPs@MoS2 nanocomposite might offer a good possibil- ity for electrochemical sensing and other electrocatalytic applications.

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...

A glucose biosensor based on direct electrochemistry of glucose oxidase immobilized onto platinum nanoparticles modified graphene electrode

The platinum nanoparticles were adsorbed on graphene oxide sheets and played an important role in catalytic reduction of graphene oxide with hydrazine, leading to the formation of graphene-Pt nanoparticles. Because of their good electronic properties, biocompatibility and high surface area, graphene-Pt based composites achieved the direct electron transfer of redox enzyme and maintained their bioactivity well. The graphene-Pt nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED). The amperometric biosensor fabricated by depositing glucose oxidase over Nafion-solubilized graphene-Pt electrode retained its biocatalytic activity and has offered fast and sensitive glucose quantification.

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.

N-doped ordered mesoporous carbon as a multifunctional support of ultrafine Pt nanoparticles for hydrogenation of nitroarenes

Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content （9.58 wt%）, high surface area （417 m^2/g）, and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles （NPs）. The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs （about 1.0 ± 0.5 nm） to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger （4.4 ± 1.7 nm） and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity （conversion 100%） and selectivity （〉99%） in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst （conversion 89% and selectivity 90%）. This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.

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.

Electrocatalytic ammonia synthesis catalyzed by mesoporous nickel oxide nanosheets loaded with Pt nanoparticles

Owing to its cost‐effectiveness and adjustable eight‐electron distribution in the 3d orbital,nickel oxide(NiO)is considered an effective electrocatalyst for an ambient electrochemical nitrogen reduction reaction(NRR).However,because of the low conductivity of the transition metal oxide electrocatalyst,its application in this field is limited.In this study,we found that the doping of NiO nanosheets with a small amount(3–10 nm)of Pt nanoparticles(Pt/NiO‐NSs)leads to considerable improvements in the Faradaic efficiency(FE)and NH_(3) yield compared with those obtained using pure NiO,breaking the common perception that commercial Pt‐based electrocatalysts demonstrate little potential for NRR due to their high hydrogen evolution tendency.In a 0.1 mol/L Na_(2)SO_(4) solution at−0.2 V vs.RHE,a typical Pt/NiO‐2 sample exhibits an optimum electrochemical NH_(3) yield of 20.59μg h^(–1)mg^(–1)cat.and an FE of 15.56%,which are approximately 5 and 3 times greater,respectively,than those of pure NiO nanosheets at the same applied potential.X‐ray photoelectron spectroscopy analysis revealed that Pt in Pt/NiO‐NSs exist as Pt0,Pt^(2+),and Pt^(4+)and that high‐valence Pt ions are more electropositive,thereby favoring chemisorption and the activation of N2 molecules.Density function theory calculations showed that the d‐band of Pt nanoparticles supported on NiO is significantly tuned compared to that of pure Pt,affording a more favorable electronic structure for NRR.The results of this study show that Pt can be an effective NRR electrochemical catalyst when loaded on an appropriate substrate.Most importantly,it provides a new synthetic avenue for the fabrication of highly active Pt‐based NRR electrocatalysts.

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.

Composition-controlled synthesis of platinum and palladium nanoalloys as highly active electrocatalysts for methanol oxidation

Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesis environment.During the reaction,the feed molar ratio of the two precursors was carried over to the final products,which have a narrow size distribution with a mean size of approximately4nm.The catalytic activity for methanol oxidation reactions possible depends closely on the composition of as‐prepared PtPd alloy NPs,and the NPs with a Pt atomic percentage of approximately75%result in higher activity and stability with a mass specific activity that is7times greater than that of commercial Pt/C catalysts.The results indicate that through composition control,PtPd alloy NPs can improve the effectiveness of catalytic performance.

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.

One-step synthesis of Pt nanoparticles/reduced graphene oxide composite with enhanced electrochemical catalytic activity

A one-step electrochemical approach for synthesis of Pt nanoparticles/reduced graphene oxide （Pt/RGO） was demonstrated. Graphene oxide （GO） and chloroplatinic acid were reduced to RGO and Pt nanoparticles （Pt NPs） simultaneously, and Pt/RGO composite was deposited on the fluorine doped SnO2 glass during the electrochemical reduction. The Pt/RGO composite was characterized by field emission-scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy, which confirmed the reduction of GO and chloroplatinic acid and the formation of Pt/RGO composite. In comparison with Pt NPs and RGO electrodes obtained by the same method, results of cyclic voltammetry and electrochemical impedance spec- troscopy measurements showed that the composite electrode had higher catalytic activity and charge transfer rate. In addition, the composite electrode had proved to have better performance in DSSCs than the Pt NPs electrode, which showed the poten- tial application in energy conversion.

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.

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.