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Cyclic voltammetry and spectroelectrochemistry studies are reported for the tetramethyl- tetrapyridinoporphyrazine complexes N,N′,N″,N‴-tetramethyltetra-2,3-pyridinoporphyrazine palladium(II) (1a), N,N′,N″,N‴-tetramethyltetra-3,4-pyridinoporphyrazine palladium(II) (1b), N,N′,N″,N‴-tetramethyltetra-2,3-pyridinoporphyrazine platinum(II) (2a) and N,N′,N″,N‴-tetramethyltetra-3,4-pyridinoporphyrazine platinum(II) (2b). Cyclic voltammetry on Pt disc electrodes showed two reductions. The first reduction was assigned to one-electron transfer to the ring with the formation of a monoanion species. All the tetramethyltetrapyridinoporphyrazine complexes are readily reduced to the monoanion species in the presence of histidine or cysteine. The rate constants for the interaction of complexes 1a, 1b, 2a and 2b with histidine and cysteine range from ~2 × 10⁻³ to 0.26 dm³mol⁻¹s⁻¹.

The reaction of zinc tetrakis(3-pyridyloxy)phthalocyanine (1) with NH₄[PtNH₃Cl₃] leads to zinc tetrakis(cis-[3-oxypyridyl]-N]amminedichloroplatinum(II))phthalocyanine (2), while the reaction of 1 with cis-Pt(DMSO)₂Cl₂ or 2 with DMSO forms zinc tetrakis(cis-[(3-oxypyridyl)-N]dichloro[sulfinylbis(methane)-S]platinum (II))phthalocyanine (3). The new phthalocyanines 2 and 3, with potentially combined photodynamic activity and cytotoxicity, have been characterized by means of electronic, ¹H NMR and IR spectroscopies.

Structural optimization of ternary Pd_mPt${}_{(13-m)}$Ag${}_{42}$ nanoalloys was performed using the basin-hopping algorithm, and the Gupta many-body potential was adopted to model interatomic interaction. The optimization results show that all compositions have a structure based on icosahedron with a core–shell segregation. While the Ag atoms prefer to segregate to the surface, Pd and Pt atoms were located at the core of the cluster due to the higher surface and cohesive energy. The single platinum atom with the highest cohesive energy in Pd${}_{12}$Pt₁Ag${}_{42}$ nanoalloy was located at the center of the cluster. Also in all other compositions except Pd${}_{13}$Ag${}_{42}$, Pd atoms occupy the second shell position of the icosahedron structure. We used classical molecular dynamics (MD) simulations in canonical ensemble conditions (NVT) to investigate the melting temperatures of ternary Pd_mPt${}_{(13-m)}$Ag${}_{42}$ nanoalloys with the interatomic interactions modeled by the same potential with optimizations. The icosahedral structures were taken as the initial configurations for MD simulations. We obtained caloric curves and Lindemann indexes to investigate the melting transitions. The simulation results showed that varying the composition gives rise to a fluctuation in melting temperatures. The highest melting temperature belongs to the Pd₉Pt₄Ag${}_{42}$ nanoalloy cluster within the other compositions. However, the relative stability investigation indicates the Pd₈Pt₅Ag${}_{42}$ nanoalloy cluster as the most stable composition. The Lindemann indexes obtained for the second and third shell of icosahedral structures show that the melting takes place as a whole without any surface premelting.

Using basin-hopping algorithm within the quantum corrected Sutton-Chen (Q-SC) many-body potential, a systematic investigation has been performed for the best chemical ordering structures of 38-atom trimetallic Pd_nPt${}_{(32-n)}$Rh₆ nanoalloys with truncated octahedral (TO) geometry. The atomic mixing degrees of Pd, Pt and Rh atoms were investigated by using order parameter ($R_A$). The results show that demixing is energetically favorable for the investigated structures, where the number of Rh atoms fixed at 6. The only compositions with the number of hetero bonds lower than the homo bonds are Pt${}_{32}$Rh₆, Pd₁Pt${}_{31}$Rh₆, Pd${}_{16}$Pt${}_{16}$Rh₆ and Pd${}_{32}$Rh₆ which make segregation energetically favorable. The surface segregation of Pd atoms is explained by the lower cohesive energy of Pd atoms than Pt and Rh. The segregation of Pd atoms to the surface is also associated with the smaller surface energies compared with Pt and Rh atoms. Due to the comparable cohesive energies of Rh and Pt atoms, a computation occurs for filling the octahedral core between two kinds.

Antimony-platinum bilayers were prepared on titanium substrates by the two-step electrodeposition in the usual baths, and then surface alloys were formed by the atom diffusion in the solid phase. The simple antimony layer was little influenced by the substrate in both the measurements of X-ray diffraction and the i - E characteristic in a sulfuric acid solution. Regarding the bilayers, the catalytic activity in hydrogen evolution reaction was very sensitive to the presence of platinum, while the hydrogen adsorbability was quite insensitive. An interaction between antimony and platinum was confirmed by the appearance of a new dissolution wave in the electrochemical measurement and the occurrence of a new diffraction in the X-ray diffraction pattern after the heat-treatment of about 400°C. Although the new diffraction disagreed with any of the reported alloys, clear diffraction pattern of PtSb₂ alloy was observed, when the bilayers were heat-treated at about 600°C for one hour. Considering the penetration depth of X-ray, the alloying of antimony and platinum seems to occur also at low temperatures at least at the top surface.

Ultra-thin platinum (Pt) films were deposited on Si(100) substrates at 160°C by magnetron sputtering and subsequently annealed to form silicides. The thickness of the Pt_xSi films was found to be approximately 4 nm as determined by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) analysis shows that these films consist of PtSi and Pt₂Si phases, and a multi-layer configuration of SiO_x/PtSi/Pt₂ Si/Si was detected by angle-resolved XPS. However, the Pt₃Si phase was not detected by X-ray diffraction (XRD).

Various properties of substitutional alloys formed from aluminium and the platinum group metals (PGMs) are examined using density functional (D-F) theory and show strong variations depending on metal type. A similar pattern for the binary alloys is observed using molecular dynamics modeling employing Sutton Chen potentials. All results suggest that several of the PGMs could have superior properties to the presently used Ni₃Al alloy for high temperature applications. Some phases are predicted to be stable with extremely high melting temperatures (MTs).

Using Monte Carlo Basin-hopping algorithm within the Gupta potential, a systematic investigation has been performed for the best chemical ordering structures of 19-atom trimetallic ${\mathrm{\text{Pd}}}_n{\mathrm{\text{Ag}}}_{(17-n)}{\mathrm{\text{Pt}}}_2$ nanoclusters with double icosahedral geometry. The structures with the lowest energy at Gupta level are then re-optimized by DFT relaxations and the DFT relaxations confirmed the lowest energy structures obtained at the Gupta level indicating the double icosahedron structure is favorable for 19-atom ${\mathrm{\text{Pd}}}_n{\mathrm{\text{Ag}}}_{(17-n)}{\mathrm{\text{Pt}}}_2$ nanoclusters. It was observed that the caloric curves exhibit a smoother transition with structural isomerizations other than a sharp jump behavior.

A systematic theoretical investigation of structural and energetic behaviors of 55-atom Pt–Ag–Au ternary nanoalloys has been performed in two different composition systems. We have performed Gupta and Density Functional Theory (DFT) approaches on chosen systems. The Basin-Hopping algorithm is used for structural optimizations of Pt_nAg${}_{13-n}$Au${}_{42}$ ($n=0$–13) and Pt_nAu${}_{13-n}$Ag${}_{42}$ ($n=0$–13) ternary nanoalloys with Gupta many-body potential to model interatomic interactions. Local optimization results show that while the tendency of Au atoms to be located varies according to the composition system, the tendency of Pt and Ag atoms to be located does not change in both. For all compositions of Pt–Ag–Au nanoalloys, the structures with the best chemical ordering were then reoptimized by DFT relaxations and the mixing energies of the Gupta and DFT levels were compared. Our mixing energy analysis showed that Pt_nAg${}_{13-n}$Au${}_{42}$ ($n=0$–13) nanoalloys are not energetically suitable for mixing at both Gupta and DFT level. Also, mixing energy variations of Pt_nAu${}_{13-n}$Ag${}_{42}$ ($n=0$–13) nanoalloys obtained at Gupta level does not agree with the one obtained at DFT level. In addition, it has been found that the minimization energy changes when an atom in the central site is exchanging by an atom in the second shell and surface.

The alpha decay half-lives of even–even and even–odd Platinum (Pt) nuclei have been studied within the Coulomb and proximity potential model (CPPM). The present study is restricted to even–even nuclei with $A=166$–198. The results are compared with other calculations such as the Semi-empirical formula (SemFIS) from Poenaru et al. based on fission theory of alpha decay, the Viola–Seaborg (VS), Royer (R) and Brown formulae. Also, the alpha decay half-lives have been calculated using the Scaling law of Brown (SLB), the Universal Decay Law (UDL) of Qi et al., the Scaling Law of Horoi et al. (SLH), and Akrawy–Dorin formula (ADF) of Akrawy and Poenaru, which are the Royer modified formula for alpha decay half-live by adding asymmetry term.

For some years it has been known that a number of catalytic reactions, under specified steady operating conditions, exhibit oscillations, in the rate of product formation. These are often related to beautiful spatiotemporal patterns, including targets and spirals, on the metal surface.

These examples of self-organizational phenomena have attracted considerable interest, because they are proving to be theoretically amenable.

Here we review different approximations to model heterogeneous surface chemical reactions, which exhibit oscillatory behavior.

A focal point is the use of a detailed knowledge of the dynamics of surface structural phase transition for modeling kinetic oscillations, which represent a severe test of our understanding of chemical processes at surfaces.

Advantages and disadvantages of the Monte Carlo approach are presented to model heterogeneous oscillatory chemical reactions, with special emphasis if a Monte Carlo method is going to be applied to study the time evolution of a surface chemical reaction, as there should be a linear relationship between the time unit called the Monte Carlo step (MCS) and actual time. We conclude that special care must be taken when two or more processes are included in a simulation, because now overall MCS should be compatible with every individual process.

The mean field approach (MFA) takes into account only reaction processes and completely neglects spatial correlation and fluctuations. Therefore, this approach is not adequate for describing the rich variety of spatial patterns that are experimentally observed. On the other hand, Monte Carlo approaches are severely limited by computational capabilities. To overcome MFA limitations we propose to extend the earlier work of King and coworkers [J. Chem. Phys.100, 14417 (1996)], which did not include spatial dependence, by adding diffusion processes and gas global coupling to the coupled reaction equations.

The extended MFA can now be used as a new tool for the analysis of pattern formation in surface chemistry.

The oxidation of the single crystal stepped Pt₃Ti(510) surface at oxygen pressures below 10^-5 mbar and at a temperature of 770 K was studied by means of X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) and low energy electron diffraction (LEED). Scanning tunneling microscopy (STM) was used to follow the evolution of the surface morphology on the atomic scale. The clean surface studied in ultrahigh vacuum conditions was found by LEIS to be composed of platinum only in the outermost surface plane. LEED and STM indicate that the clean Pt₃Ti(510) surface consists of (100) terraces separated by double atomic steps. The exposure of the clean surface to oxygen at pressures in the range of 10^-7–10^-5 mbar leads to the growth of a titanium oxide layer (with a composition close to TiO) which covers completely the substrate surface. The TiO film has long range order and exhibits complex LEED patterns. The STM measurements indicate that the ordered array of steps is kept in the early stages of the oxide film growth, whereas a change of the step morphology and step orientation is observed during the oxidation process.

In this paper we apply a model of surface chemical reactions to describe pattern formation in the CO oxidation on Pt(100). The model is an extended mean field approximation (EMFA), where two coupling processes are included: gas global coupling (to take into account the mass chemical reaction balance) and CO diffusion. The surface is divided into M×M cells; inside each of them the mean field approximation (MFA) is fulfilled. Anisotropic diffusion between nearest neighbor cells and gas coupling among all cells are also allowed.

The EMFA goes beyond the traditional reaction–diffusion approaches with Fickian terms, in favor of a more general mass balance equation that consistently incorporates the coupling between CO diffusion and the nonlinear phase transition of the substrate.

In this paper we study three different cases: (a) homogeneous coverage oscillations — when CO and O₂ partial pressures are kept constant and the whole set of M×M cells have the same value of partial coverages and phase fractions; in this case the system exhibits self-oscillations, such as those experimentally observed; (b) inhomogeneous coverage oscillations — when CO and O₂ partial pressures are kept constant and inhomogeneities of coverage are present; the system evolves by CO diffusion between nearest neighbor cells; (c) gas global coupling — when gas global coupling is allowed and inhomogeneities of coverage are present, there are oscillations in the gas phase that follow the surface evolution.

A modeling analysis of the growth mode of submonolayer amounts of Pt on Cu(111) and Cu on Pt(111) for different coverages and temperatures reproduces the known experimental behavior. An atom-by-atom analysis of the energetics using the BFS method for alloys provides a simple explanation of the underlying mechanisms leading to the observed behavior.

The powerful RHEED technique has been demonstrated for the structural determination of the nano-crystals grown on metal and oxide substrate surfaces. Pt was electrochemically deposited onto a electrode, while Pb and cobalt were vapor deposited onto Ag(111) and oxide film/NiAl(100), respectively under UHV conditions. At any Pt coverage, 3D-clusters develop for which the Pt clusters grow in (311) orientation on the substrate surface, where the atomic rows of the (311) facet are parallel to the atomic rows of the surface. Due to the strong bonding at Pb/Ag(111) interface, the Pb deposit grows in 2D-islands with a phase (Θ < 1 ML). On the other hand, the β-crystallites of ≈ 1 nm in diameter with inclusion of smaller-sized particles (D < 1 nm) are observed on Θ-Al₂O₃ after Co deposition at room temperature. Annealing at 900 K Co clusters (≈ 3 nm) grow larger at expense of small particles on thin oxide film on NiAl(100) and become better ordered, where the [110] axis of the Co(001) facet is parallel to the [100] direction of the (001)-oxide surface. The in-plane lattice constant of Co clusters is ca. 4 larger than that of bulk Co, yielding less strain at the (001)-oxide surface. These results demonstrate that both orientation and phase of metal nano-clusters are governed by surface structure of the substrate.

The growth process of platinum on Ru(0001) near room temperature was characterized using photoelectron spectroscopy of high resolution. The binding energy position and intensity of the Pt 4f_7/2 and Ru 3d_5/2 core levels as well as the shape and structure of the valence band spectra corresponding to the different stages of the deposition were analyzed. Up to ca. two adsorbate monolayers, the intensity changes of the peaks indicated layer-by-layer growth mode. The surface core level shifts of Ru and Pt levels were evaluated as -0.33 and -0.476 eV, respectively. The valence band spectra show a rather weak interaction between the d-bands of Pt and Ru.

The interaction of hydrogen with a platinum (111) cluster using the atom superposition and electron delocalization–higher binding ASED-TB quantum calculation method was studied. The metal surface was represented by a Pt cluster of seven layers. The effect of hydrogen on this metal substrate was studied by the analysis of density of states and crystal orbital overlap populations curves. The energy surface plots allow us to find a possible diffusion path through the cluster from one side to the other. The Pt–Pt metal bond is weakened during H adsorption and diffusion. The main components in the Pt–H bond are the Pt 6s (31%), 6p (26%), and 5 d_xz (16%) orbitals.

The emissions of nitric oxide and carbon monoxide from internal combustion engines generate a large impact on the environment and on people's health. Catalytic reduction of these species using platinum group metals has already shown significant potential for emissions control. Since catalysts often use carbon monoxide to reduce nitric oxide in these devices, accurate models of their interaction are required to advance catalyst simulations in order to meet increasingly stringent emissions regulations. As a result, this paper reviews the literature of the NO–CO reaction over platinum in order to develop more precise detailed and global reaction mechanisms for use in exhaust after-treatment modeling activities. Moreover, it is found that the reaction between NO and CO over platinum yields carbon dioxide and nitrogen as main products and nitrous oxide as an important side product. Hence, this paper additionally describes the mechanism for nitrous oxide production in advance of greenhouse gas regulations.

The present article describes the synthesis of platinized TiO₂ nanocomposite and its photocatalytic activity. The surface modification of the catalyst was carried out by platinum metals adopting a modified photo-deposition method. The effect of platinum loadings, such as 0.5, 1.0, 1.5, 2.0, and 2.5 wt% on the photocatalytic activity of TiO₂ has been studied. The study showed that the activity of TiO₂ can be significantly enhanced by depositing an optimum concentration of platinum metals that help to prevent the electron hole–pair recombination which is a major energy wasting step in photocatalysis. The photocatalytic efficiency of various samples was tested by studying the photo-oxidation of a dye namely Methyl Orange as probe reaction.

This paper demonstrates the functionality of a simple and convenient microfluidic method in synthesizing a series of poly(vinylpyrrolidone) (PVP) stabilized nanoparticles (NPs) of various novel metals (Pt, Pd, Ru, Rh, Ag, and Au) with an average diameter of $<$2 nm. In this method, the use of microfluidic mixture provided a homogenous mixing of the metal precursors and reducing agent nearly at the molecular level, that yield monodispersed sub-nanosize NPs. Core diameters of the produced NPs determined by transmission electron microscopy (TEM), were $1.3\pm 0.3$, $1.6\pm 0.3$, $1.3\pm 0.2$, $1.7\pm 0.4$, $1.9\pm 0.4$ and $1.2\pm 0.2$nm for Pt, Pd, Ru, Rh, Ag and Au NPs, respectively. Of them, Pt NPs were detailed characterized. The obtained Pt NPs were found to have fcc crystal structure with 1.2 nm crystalline size which is very similar to the corresponding TEM result. The efficiency of the synthesis of NPs by micromixer was compared with batch/NaBH₄ reduction method for the Pt NPs. It was found that in batch method the as-prepared NPs decreased the reducing ability of NaBH₄ by catalytic degradation. In contrast, the micromixer could separate the produced metal NPs from the reaction system soon after the formation of NPs and enables feeding the fresh NaBH₄ solution throughout the synthesis. Fourier Transform Infrared (FTIR) spectrometry measurements of adsorbed ${}^{12}$CO molecules on Pt NPs showed that the NPs surface were negatively charged with a high population of edge and vertices atoms.