Pd Nanoparticle Films Research Articles

Thickness-dependent L10 ordering behavior in polycrystalline Fe–Pd nanoparticle films on glass substrates

The dependence of the L10 ordering, magnetic properties and microstructure on film thickness of the Fe51Pd49 nanoparticle films deposited at 800 °C was investigated. The L10 ordered phase and hard magnetic properties were found for the samples with the thickness less than 30 nm. As the thickness was increased to 45 nm and thicker, the samples exhibited the A1 disordered phase and soft magnetic properties. The lack of heterogeneous nucleation sites is responsible for the A1 disordered phase in the thicker FePd samples, which was confirmed by the results of microstructural and crystallographic analyses. The long term re-annealing at a lower temperature (600 °C for 8 h) can induce the L10 ordering of the large size FePd nanoparticles originally composed of the A1 phase, which also supports the statement that the heterogeneous nucleation sites play an important role on L10 ordering of the FePd films.

Pd Nanoparticle Film on a Polymer Substrate for Transparent and Flexible Hydrogen Sensors.

Alongside the rise in fully automated equipment and wearable devices, there is currently a high demand for optically transparent and flexible gas sensors operating at room temperature. Nanoparticle films are ideal H2-sensing materials that can be coupled with flexible substrates because of their discrete nanogranular structure and unique interparticle electrical responsiveness. In this work, we present an optically transparent and flexible H2 sensor based on a Pd nanoparticle film, prepared on a polyethylene terephthalate sheet using a straightforward nanocluster deposition technique. Hundreds of bending cycles demonstrated that the sensor has good electrical stability and mechanical robustness without significant degradation in H2-sensing performance. The H2-sensing behaviors under bent state were systematically evaluated. The loading of tensile and compressive strains under bent state produced a positive and negative influence, respectively, on the sensing performances. The possible influence mechanism of the tensile and compressive strains on the H2-sensing performance was attributed to the changes in the percolation network topology and the interparticle space induced by the strains. The ability to detect a H2 concentration as low as 15 ppm, dynamic response range as wide as 0-10%, and sub-10 s response time was achieved. In addition, the sensor can be operated in the relative humidity range of 0-90% at room temperature. These results demonstrate that the sensor exhibits significant potential for next-generation transparent and flexible H2 detectors.

Ultrahigh methanol electro-oxidation activity from gas phase synthesized palladium nanoparticles optimized with three-dimensional carbon nanostructured supports

Pd nanoparticles with a mean diameter of 6.7nm are prepared by gas phase cluster beam deposition. The Pd nanoparticle films exhibit excellent catalytic activity and stability for methanol oxidation. 3D hybrid nanostructures combined with multi-walled carbon nanotubes and few-layer graphene sheets are used as supports to further enhance the methanol electro-oxidation activity of the Pd nanoparticle catalysts by a factor of more than 2.7. The catalytic activity towards methanol electro-oxidation is characterized with cyclic voltammetry measurements. An ultrahigh electrochemical active surface area (ECSA) as large as 311m2g−1pd and a mass specific current corresponding to methanol oxidation levels as high as 4038mAmg−1pd are realized. These results can be attributed to the high electrochemical activity of the Pd nanoparticles and the unique conductive structure of the multi-walled carbon nanotubes/few-layer graphene sheets.

Detection of hydrogen peroxide at a palladium nanoparticle-bilayer graphene hybrid-modified electrode

We report a nonenzymatic H2O2 sensor based on a glassy carbon electrode modified with bilayer graphene films (BGFs) that were decorated with well-defined Pd nanoparticles. The BGFs were synthesized with a chemical vapor deposition process, and the Pd nanoparticle films were produced by gas phase cluster beam deposition. The BGFs provide great accessible active surface area and excellent conductive interfaces for electron transfer, which largely enhance the electrocatalytic performance of the modified electrodes. A rapid response time of less than 3s and a wide linear range from 4μM to 13.5mM was exhibited in the amperometric detection of H2O2.

Palladium nanoparticle-based surface acoustic wave hydrogen sensor.

Palladium (Pd) nanoparticles (5-20 nm) are used as the sensing layer on surface acoustic wave (SAW) devices for detecting H2. The interaction with hydrogen modifies the conductivity of the Pd nanoparticle film, producing measurable changes in acoustic wave propagation, which allows for the detection of this explosive gas. The nanoparticle-based SAW sensor responds rapidly and reversibly at room temperature.

Fast response characteristics of hydrogen sensors based on Pd nanoparticle films with controlled coverage

The response time of the quantum conductance-based hydrogen sensor fabricated from films consisting of closely spaced palladium nanoparticles formed with cluster beam deposition was investigated. The dependence of the response time on the coverage-regulated nanoparticle size, as well as the hydrogen pressure, was determined. At low hydrogen pressure, the response time is dominated by the hydriding time of the larger Pd nanoparticles. Fast response as short as 3 s to 1,000 Pa H2 could be realized with the lower coverage nanoparticle film, with a sensitive change of the relative conductance as high as 70 %. At 10 kPa hydrogen pressure, subsecond hydrogen response could be realized. With the increase of the hydrogen pressure, the response time of the devices becomes longer and longer as determined by the hydriding time of the Pd nanoparticles involved in the smaller size population of the size distribution, and approaches the same value for the hydrogen sensors with different nanoparticle coverages. The abnormal increase of the response time accompanied by the formation of the α + β coexistence phase of PdHx was also investigated.

Optimizing Hydrogen Sensing Behavior by Controlling the Coverage in Pd Nanoparticle Films

The response of quantum-conductance-based hydrogen sensors fabricated by controllable deposition of closely spaced Pd nanoparticle films between interdigital electrodes was investigated. Three typical response regions with different conductance–hydrogen pressure correlations were observed. The response characteristics of the devices were found to depend strongly on the nanoparticle coverage. In the low H2 pressure region, higher coverage gives higher sensitivity. In the high H2 pressure region, quantitative sensing can only be realized with low nanoparticle coverage. Optimizing the coverage allows the attainment of highly sensitive hydrogen sensors with a very wide quantitative working range, extending far beyond the hydrogen pressure region associated with the α-to-β phase transition of Pd.

Simple preparation method of Pd nanoparticles on an Au electrode and its catalysis for dioxygen reductionElectronic supplementary information (ESI) available: XRD pattern of an evaporated Au electrode and CVs for the reduction of O2 on a bare Au(111) electrode or a Pd-nanoparticle-film-modified electrode. See: http://www.rsc.org/suppdata/nj/b3/b300566f/

A simple method for the fabrication of Pd nanoparticles is described. The three-dimensional Pd nanoparticle films are directly formed on a gold electrode surface by simple electrodeposition at −200 mV from a solution of 1 M H2SO4+0.01 mM K2PdCl4. X-Ray photoelectron spectroscopy verifies the constant composition of the Pd nanoparticle films. Atomic force microscopy proves that the as-prepared Pd nanoparticles are uniformly distributed with an average particle diameter of 45–60 nm. It is confirmed that the morphology of the Pd nanoparticle films are correlated with the electrodeposition time and the state of the Au substrate. The resulting Pd-nanoparticle-film-modified electrode possesses high catalytic activity for the reduction of dissolved oxygen in 0.1 M KCl solution. Freshly prepared Pd nanoparticles can catalyze the reduction of O2 by a 4-electron process at −200 mV in 0.1 M KCl, but this system is not very stable. The cathodic peaks corresponding to the reduction of O2 gradually decrease with potential cycling and at last reach a steady state. Then two well-defined reduction peaks are observed at −390 and −600 mV vs. Ag/AgCl/KCl (sat.). Those two peaks correspond to a 2-step process for the 4-electron reduction pathway of O2 in this neutral medium. The former peak is ascribable to the 2-electron reduction of O2 to H2O2, while the latter is assigned to the reduction of H2O2 to H2O. The observed electrocatalysis for the reduction of O2 is attributable to the extraordinary catalytic activity of the Pd nanoparticles over the bulk gold electrode.

Preparation of palladium nanoparticles functionalized with biferrocene thiol derivatives and their electro-oxidative deposition

The first preparation of functional molecule-modified Pd nanoparticles was performed by an exchange reaction of octyl thiolate-covered Pd nanoparticles of diameter d = 3.8 ± 0.8 nm with the biferrocene-terminated alkanethiol, (η5-C5H5)Fe(C10H8)Fe (η5-C5H4CO(CH2)7SH). The biferrocene-modified Pd nanoparticles underwent two-step one-electron oxidation in aprotic solvents. By electrochemical oxidation of the biferrocene moieties, a redox-active Pd nanoparticle film was formed on the electrode. The STM image revealed that the electrodeposition of Pd nanoparticles constructs a moderately flat film.