Thin films of platinum deposited by physical vapor deposition (PVD) processes such as evaporation and sputtering are used in many academic and industrial settings, for example to provide metallization when tolerance to corrosive thermal cycling is desired, or in electrocatalysis research. In this review, various practical considerations for platinum (Pt) metallization on both Si and SiO2 are placed in context with a comprehensive data review of diffusion measurements. The relevance of diffusion phenomena to the development of microstructure during deposition as well as the effect of microstructure on the properties of deposited films are discussed with respect to the Pt–Si system. Since Pt and Si readily form silicides, diffusion barriers are essential components of Pt metallization on Si, and various failure modes for diffusion barriers between Pt and Si are clarified with images obtained by electron microscopy. Adhesion layers for Pt films deposited on SiO2 are also considered.

We present a general purpose Pt-Pt density-functional tight-binding (DFTB) parameter for Pt clusters as well as bulk, using a genetic algorithm (GA) to automatize the parameterization effort. First we quantify the improvement possible by only optimizing the repulsive potential alone, and second we investigate the effect of improving the electronic parameter as well. During both parameterization efforts we employed our own training set and test sets, with one set containing ∼20,000 spin-polarized DFT structures. We analyze the performance of our two DFTB Pt-Pt parameter sets against density functional theory (DFT) as well as an earlier DFTB Pt-Pt parameters. Our study sheds light on the role of both repulsive and electronic parameters with regards to DFTB performance.

Engineering the surface structure, together with the incorporation of a second metal, is an effective strategy for boosting the catalytic activities of Pt-based catalysts toward various reactions. Here, we report a facile approach to the synthesis of Pt–Ag octahedral and tetrahedral nanocrystals covered by concave surfaces. The presence of the Ag(I) precursor not only facilitated the reduction of the Pt(IV) precursor but also led to the formation of concaved facets on the Pt–Ag nanocrystals. Besides, poly(vinylpyrrolidone) (PVP) was demonstrated to serve as a co-reductant, in addition to its role as a colloidal stabilizer. Using PVP with different molecular weights, we were able to tune the size of the Pt–Ag nanocrystals in the range of 9–25 and 14–32 nm for the octahedral and tetrahedral shapes, respectively. The Pt–Ag nanocrystals exhibited 4.6- and 2.0-fold enhancements in terms of specific and mass activities, respectively, toward methanol oxidation, when benchmarked against the commercial Pt/C catalyst. After 1000 cycles of the accelerated tests, the specific and mass activities of the Pt–Ag nanocrystals were still 3.6 and 1.6 times as high as those of the original commercial Pt/C.

Nanosized Platinum (Pt) nanocrystals (NCs) have been extensively investigated in catalytic fields because of their high reactivity due to the unique electron structure. However, the rarity and the high cost of Pt limit its applications in industry. To reduce the usage of Pt in catalytic industry, research interests have been extended to Pt-based nanoalloys. Among various nanostructures, nanoframes (NFs) showed promising catalytic performance even with a lower metallic loading dose. Herein, we report a facile and robust method to transfer the Pt-Ni tetrahexahedral (THH) NCs into THH NFs in which carbon monoxide (CO) plays a role of the “etching reagent”. The driving force of the etching is a formation of gaseous metallic complex, Ni(CO)4, known as Mond Process, preferentially dealloying nickel atoms along <100> directions of the Pt-Ni THH NCs. It is determined that the resultant Pt-Ni THH NFs possess an open, stable and high-index preserved nanostructure, in which the outside atomic layers are composed of only Pt atoms with surface strains. Compared to a solution-based etching process, this approach requires less etching time and generates a well-defined structure. The associated thermal annealing operation also releases extra internal stress, making the NFs more stable with fewer surface defects. Such Pt-Ni THH NFs show interesting potentials in the improvement of stability and activity as advanced catalysts.

The synthesis of Platinum (Pt) nanoparticles by gamma irradiation is presented. The 0.1 M Pt solution of different concentration was prepared from K2PtCl4. The platinum aqueous solutions were irradiated by gamma radiation at a dose of 70, 90 and 120 kGy. The findings show the effect of irradiation on PtII solutions with different concentrations. The big black particles that are fairly agglomerated when the concentration was above 0.0050 M were observed. The UV-Vis spectrum of Pt of different concentrations shows a strong absorption peak at the wavelength 261 nm after irradiation, which indicates the presence of platinum nanoparticles. Furthermore, FTIR, XRD and HRTEM images also confirmed the presence of the nanoparticles produced by Radiolysis. The size of the Pt nanoparticles was found to be 7.39 nm.

Here gelatin biotemplated platinum aerogels were prepared from gelatin hydrogels equilibrated in K2PtCl4 solutions ranging from 1-250 mM and reduced with sodium borohydride before supercritical drying in liquid CO2. Scanning electron microscopy revealed an average ligament diameter of 40.6 ± 9.7 nm and a pore size range of ∼10 – 200 nm. Thermogravimetric analysis correlated the ratio of metal content to biotemplate mass as a function of equilibrated platinum ion solution, and X-ray diffractometry indicated platinum metal with no detectable oxide phases. Electrochemical impedance spectroscopy indicated a specific capacitance of 1.92 F/g, with a corresponding specific electrochemical accessible surface area of 6.39 m2/g. Cyclic voltammetry performed in H2SO4 demonstrated biotemplated platinum aerogel potential for catalytic and energy storage applications.

Microstructural, chemical, and electrochemical property measurements results, for (111) crystallographically oriented Pt100-xMx (M = V, Zr; 3 < xv < 14; and 4 < xZr < 35, At.%) sputtered thin films are presented, with electronic structure calculations. These Pt-based alloys were prepared to investigate early transition metal (ETM), late-transition-metal (LTM) alloys as potential electrode materials in hydrogen-air polymer-electrolyte-membrane fuel cells (PEMFCs). The Pt100-xMx oxygen-reduction-reaction (ORR) currents peak for 8 < x < 10 atomic percent, so local chemical-short-range-order, may exist; as the peak in ORR activity is commensurate with the strong ordering in Pt8M (M = Ti, V, Zr). The hydrogen under potential deposition (Hupd) at Pt active area, and ORR reaction kinetics, on the alloyed surfaces are composition dependent, suggesting three possible effects: 1) charge transfer from V-(3d)3 [or Zr- (4d)2] states, to the hole in the top of the Pt-(5d)9 band alters the electronic structure at the Fermi energy; 2) alloying Pt with the ETM elements introduces a bi-functional character to the electrode surface, and 3) or the presence of short range chemical order induces a Fermi energy shift. To confirm the 1st and 3rd hypotheses, the electronic structure of Pt8Ti, Pt8V, and Pt8Zr, were calculated using the WIEN2k program package. The electronic structure calculations for ordered Pt8M give strong confirmation of the hypotheses, as they reveal that the Pt8M Fermi energy lies within the Pt-5d anti-bonding band, and also falls into a pseudogap in between the Md bonding and anti-bonding bands. In addition, the Pt8M DOS calculations confirm the presence of a deep pseudogap formed across the Fermi energy for both the Pt-sp and M-sp electrons. These experimental and theoretical results motivate additional studies of the novel Pt8M phases.

SnO2 doped with Sb and Nb has been investigated for its use as catalyst support materials replacing carbon to enhance PEM fuel cells stability. Nanostructured powders of various doping levels were prepared by flame spray pyrolysis (FSP). The specific requirements of surface area >50 m2g-1 and electronic conductivity >0.01 Scm-1 were obtained, and pore sizes ranging mainly from 10 to 100 nm. Pt particles (9-20 wt.% in loading targeted) of ∼1 nm well dispersed in Sb-doped SnO2 was prepared by a one-step FSP procedure providing microstructures of high interest for further investigations as cathode in PEM fuel cells.

PtCu nanoparticles were synthesized with different pH and support conditionsusing radiochemical process. The nanoparticle structures were characterized bytransmission electron microscopy, inductively coupled plasma atomic emissionspectrometry, X-ray absorption spectroscopy, and X-ray diffraction techniques.The nanoparticle structure was relevant to the pH of the precursor solutions.The lattice parameter of PtCu alloy increased in high pH samples, whichindicates the critical effect of metal ion adsorption in precursor solution onnanoparticle structure.

This review essay critically examines the evolution of scholarly literature on Brazil's Partido dos Trabalhadores since the PT's founding in 1980. We periodise the relevant literature into four phases, examining the foundation of the PT, the party's early experience in subnational government, its transformation and moderation in the late 1990s, and finally its experiences in national government since capturing the presidency in 2002. After detailing strengths and weaknesses of this research, we also examine the trajectory of the PT in light of recent comparative work on the so-called ‘left turn’ in Latin America. We conclude by offering an agenda for future research on the PT.

This work aims to synthesize PtPd catalytic clusters and to study the effect of the particle size, the curvature and possible alloying on the catalytic activity for oxygen reduction reaction, electrochemical stability, the mass-transfer of redox active species toward catalytic sites and the electro-kinetic of the oxygen reduction reaction (ORR) process. The curvature and the chemical composition of the catalyst surface significantly influence the electrochemically active surface area and catalytic activity toward oxygen reduction, regardless the particle size. The best catalytic activity was accomplished for 45 nm clusters due to possible alloying that enhance the O2 adsorption and dissociation. The complementary impedance studies demonstrated that 45 nm cluster has also the shortest effective diffusion length and the highest reaction rate constant among all morphologies, indicating on superior reactant transport to the catalytic sites. In addition, the 45 nm clusters showed improved electrochemical stability that is believed to be the combined effect of alloying and the compactness of the structure.

This article provides a new interpretation of the changes that occur in party-civil society relations when progressive parties of mass-based origin gain state power by looking at the experience of the Brazilian Workers’ Party (PT) during the Lula administration. The need to preserve what is defined here as ‘social governability’ changes the nature of party-movement relationships when political parties move from opposition to government. The article shows how the PT in national executive public office, to a large extent, managed to secure social governability through reward-based linkages, such as the distribution of jobs in the state apparatus and the allocation of massive state subsidies.

Direct Methanol Fuel Cell, DMFC, technology, can be used for fabrication of sensors for volatile organic compounds like alcohols. A fundamental limitation in DMFC is methanol crossover. In this process methanol diffuses from the anode through the electrolyte to the cathode, where it reacts directly with the oxygen and produces no electrical current from the cell. This also results in poisoning of the cathode catalysts. The designed and fabrication of the sensor is by means of micro electro mechanical systems (MEMS) fabrication technology with electrochemical inputs. To achieve this we have used a passive mode design protocol using COMSOL Multiphysics. The design and simulation would involve optimization of various parameters, in the construction of the cell. We can optimize the overall power density and hence the sensitivity of the sensor by the modification of various parameters like the area of the working electrodes, separation distance and the electrode-electrolyte interface. A passive mode design protocol, for a cm cell area, using various parametric functions, and interfacing Darcy’s law of fluidic flow through a porous medium, under specific pressure and temperature, was applied. The designing involves the construction of gas diffusion layers using carbon cloth for anode and cathode with various parametric variations. Nafion membrane was selected as proton exchange membrane for the construction with different interface structure to analyze the sensor’s performance. Platinum and various alloy catalysts like Pt-Ru, Pt-Fe, Pt-Sn and Pt-Mo was chosen as the working catalysts. The parametric functions of the cell were optimized for ampherometric detection. It is proposed to design a MEMS based sensor with microfludic interconnects and its response characteristics will be studied.

The arrival of Luiz Inácio ‘Lula’ da Silva and the Partido dos Trabalhadores (Workers' Party, PT) at the helm of the Brazilian federal government in 2003 represented the culmination of a slow and deep-rooted process of party transformation. Attributable partly to the inevitable consequences of the party gradually inserting itself into governmental institutions, and partly to strategic decisions made by the dominant coalition that had controlled the PT since 1995, these transformations significantly changed the organisational features of the party, paving its way to the federal government. This article analyses these processes, and the subsequent changes throughout the Lula government, from an organisational perspective, linking exogenous challenges and the party's genetic model with the strategies consciously adopted by the petista leadership.

We explored the use of galvanostatic electrochemical deposition of Pt for cost-effective fabrication of interconnects in flexible implantable bio-medical devices. Initial studies were done on coupons diced from 200 mm Si wafers coated with PVD TiN. Based on the physical and chemical properties of the electrodeposited Pt films, optimal conditions were chosen for through-mask plating of centimeters long Pt lines on flexible, medical grade, releasable polyimide layers. Possibility for further up-scaling was considered with special emphasis on high throughput manufacturing of Pt interconnects with good adhesion to TiN/flexible substrates, low impurity content and resistivity, and acceptable roughness and uniformity.

Platinum particles supported in zeolites are used as catalysts for hydrogenation/ dehydrogenation reactions. In this study in situ high energy synchrotron X-ray diffraction was used to study the Pt particle formation under calcination and reduction conditions using time resolved pair distribution function (PDF). Because these particles grow inside the pores of zeolite X, PDF is able to give insight to unique information at the short and medium interatomic distance range that cannot be readily obtained with other techniques. Among the information obtained are the Pt atom interactions during calcination and the evolvement of the Pt particle sizes and average Pt-Pt distances during reduction.

Electrode catalysts composed of carbon supported PtRu nanoparticles (PtRu/C) synthesized by radiochemical process were annealed to control the PtRu substructure to enhance catalytic activity. The substructure of the PtRu nanoparticles synthesized by using high-energy electron beam under acidic condition was Pt-rich core/Ru-rich shell type, reflecting the redox potentials of each precursor ions. The material characterization techniques revealed that the reductive annealing led to the mixing of PtRu both in the core and on the surface. The sample with annealing temperature of 300°C for 5 hour showed the highest methanol oxidation current, 2.3 times higher than that obtained with before annealing.

The considerable potential of model-type thin film electrodes for the investigation of oxygen exchange pathways is demonstrated for different electrode materials on yttria-stabilized zirconia (YSZ). In particular, a correlation of voltage-driven 18O tracer experiments and electrical ac and dc measurements has proven to be helpful when aiming at mechanistic conclusions. For Pt electrodes, two different parallel reaction pathways can be identified under equilibrium conditions. At lower temperatures, a diffusion limited path through the electrode is dominant, whereas at higher temperatures, an electrode surface path with oxygen incorporation at the three-phase boundary determines the electrochemical activity. In addition, for high cathodic polarization, an electrolyte surface path with electron transfer via YSZ outperforms both other pathways. The oxygen incorporation zones of the bulk path as well as the electrolyte surface path can be visualized by 18O tracer incorporation experiments in combination with time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis. A successful separation of surface and bulk path can also be obtained for La0.8Sr0.2MnO3−δ (LSM) electrodes by means of 18O tracer incorporation at different cathodic overpotentials. Under lower polarization, a surface path with oxygen incorporation at the three-phase boundary is dominant, whereas at higher cathodic overpotential, the bulk path becomes significantly more pronounced. These changes are discussed in terms of polarization-induced changes of the ionic conductivity in the LSM electrode. Measurements on the acceptor-doped perovskite-type materials La0.6Sr0.4CoO3−δ (LSC) and La0.6Sr0.4FeO3−δ (LSF) illustrate the limitations of the tracer incorporation method. In the case of highly active LSC electrodes with low polarization resistances, the tracer distribution is determined by the electrolyte, and thus the active sites of the electrodes can no longer be visualized. The effect of polarization-induced changes of the electrode's electronic conductivity is demonstrated for LSF. Only a region close to the current collector remains electrochemically active owing to limited lateral electron transport.

Degradation of the catalyst and catalyst support is an essential limitation of polymer electrolyte membrane (PEM) fuel cells containing commercial platinum on carbon catalysts. Catalysts based on platinum nanoparticles coated onto nanostructured TiO2 materials are presently investigated as a more stable and equally cost effective alternative. Reported here is the synthesis of two different Pt/Nb0.1Ti0.9O2 catalysts that were prepared by chemical reduction of H2PtCl6 with either sodium borohydride in ethanolic surfactant solution or ethylene glycol. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy confirmed the deposition of Pt nanoparticles on the surface of the nanofibers and revealed average sizes of 5.4 nm and 7.6 nm for reduction with ethylene glycol and sodium borohydride, respectively. The formation of smaller sized Pt nanoparticles in ethylene glycol is reasoned with the passivation of the nanoparticle surface by glycolic anions. Cyclic voltammetry measurements confirmed a higher electrochemical specific surface area (ESCA) of about 5.45 m2/gPt for the catalyst with smaller nanoparticles while the other catalyst reached only 4.96m2/gPt. Both catalysts retain about 60% of their electrochemically active surface area after 1000 voltammetric cycles in the range of 0.03 to 1.4 V vs. RHE. This relatively high value of activity retention is explained with a strong interaction between Pt nanoparticles and Nb0.1Ti0.9O2 support.