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The intermetallic alloy Al5Co2 structure was studied by X-ray photoelectron diffraction and applying the standard software MSCD that shows a (1 × 1) termination. The reliability factor indicated the best termination belongs to the Al-rich surface layer.

DFT calculations and solid-state NMR spectroscopy are a powerful combination to provide a detailed characterization of phosphorus-containing graphene oxides with outstanding properties for diverse applications.

The present work reports on a comprehensive surface atomic structure investigation on a Pt/Cr2O3/Ag(111) model catalyst.

This work aimed to evidence the potential use of tannin-based carbon xerogel as a co-catalyst in photocatalytic processes based on solar light. Specifically, the tin (IV) oxide/carbon xerogel photo...

Monolayer hexagonal boron–nitrogen–carbon (h-BNC) is considered a prominent candidate for the next generation of semiconductor electronic devices. Nevertheless, experimental evidence of h-BNC forma...

Considering the ever-increasing need for efficient wastewater treatment, this study focused on the development of new kraft lignin-based carbon xerogel/zinc oxide (XCL/ZnO w) photocatalysts. The inclusion of the carbon xerogel is expected to cause an improvement in charge transfer throughout the photoactivation process, consequently enhancing its overall photocatalytic efficiency. Characterization shows that the materials developed are composed of both zinc oxide and carbon xerogel. The addition of the lignin-based carbon xerogel caused a significant morphological modification to the composite materials, resulting in a greater specific surface area. Regarding the photocatalytic efficiency, the optimized composite (XCL/ZnO 1.0) displayed superior efficiency to the pure zinc oxide, especially when calcined at 700 °C, with an increase of 20% in the overall photodegradation capacity for the 4-chlorophenol (4CP) molecule. The XCL/ZnO 1.0 also displayed better performance than its tannin counterpart, previously reported in the literature, obtaining a 60% increase in the apparent reaction rate constant. The XCL/ZnO 1.0 also displayed better performance for the simultaneous hexavalent chrome (Cr (VI)) reduction/4CP oxidation reaction. Salinity and system pH had a significant influence on the efficiency of the 4CP photodegradation, as higher values of salinity and lower pHs caused a decrease in the overall efficiency of the process. At last, chronoamperometry and open-circuit potential tests confirmed the superiority of the XCL/ZnO 1.0 over the pure ZnO, highlighting the beneficial impact of the carbon xerogel on the charge transport dynamics of the composite.

Metal adatoms play a key role in surface diffusion, adsorption conformation, and self-assembly of porphyrin molecules on metal surfaces. Herein, we study the specific influence of coadsorption of F...

Surface diffusion, molecular conformation, and on-surface coupling reactions are key processes for building tailored molecular nanostructures such as graphene nanoribbons, polycyclic aromatic hydrocarbons, and one-dimensional/two-dimensional (2D) polymers. Here, we study the surface diffusion and coupling in situ of a chlorinated porphyrin, namely 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (Cl4TPP), using a combined scanning tunneling microscopy (STM), density functional theory (DFT), and X-ray photoelectron spectroscopy approach. Using STM, we obtain surface migration and rotation barriers ΔE of 0.77 ± 0.09 and 0.93 ± 0.28 eV, respectively, indicative of covalent binding to the surface. In fact, we find that the precursors as well as all the reaction species exclusively (≈100%) adopt a peculiar “inverted” conformation covalently bonded to Cu(111). Using DFT, we have mapped two coupling reaction pathways: direct dechlorination and Cu adatom-mediated Ullmann coupling. We find that the latter is essential...

For the first time the development of an electrochemical method for simultaneous quantification of Zn

3D printing is the most popular form of additive manufacturing, and conductive 3D-printed platforms have been recognized as an emerging class of devices with high potential for electrochemistry. Nevertheless, as-printed electrodes provide poor conductivity due to the presence of high amounts of insulating thermoplastic material, requiring surface post-treatments to enhance their electrochemical performance. Such treatments often employ non-eco-friendly, costly, and time-consuming protocols. In this regard, we propose, for the first time, a sub-minute (around 50 s) and reagentless surface treatment of carbon-black/PLA-based 3D-printed electrodes using a Photo-Thermal approach by a CO2 laser. After the proposed treatment (optimized conditions: the power of 6.2%, the scan rate of 20 mm s−1, and height of 10 mm), a marked improvement in the electrochemical electrode response (current increase and peak-to-peak separation) was achieved towards the detection of catechol, ascorbic and uric acids, paracetamol, hexaammineruthenium(III) chloride, and Ferri/ferrocyanide redox couple. The enhanced simultaneous determination of Cd2+, Pb2+, and Cu2+ was also demonstrated. As a proof-of-concept, the quantification of the adulterant paracetamol in a real seized cocaine sample was performed using a fully 3D-printed electrochemical system, and a good recovery value of 97.8% was acquired. To explain all the improved results, the electrode was carefully characterized by imaging, spectroscopic and electrochemical techniques. Additionally, the between-measurement % relative standard deviation (%RSD) was 6.8% (n = 12), while the between-device %RSD was 7.5% (n = 6) at the 1 µmol L-1 paracetamol, indicating adequate manufacturing reproducibility. Thus, the strategies developed here open up new possibilities for applications of carbon-based 3D-printed electrodes in analytical electrochemistry.

For the first time the development of an electrochemical method for simultaneous quantification of Zn2+ and uric acid (UA) in sweat is described using an electrochemically treated 3D-printed working electrode. Sweat analysis can provide important information about metabolites that are valuable indicators of biological processes. Improved performance of the 3D-printed electrode was achieved after electrochemical treatment of its surface in an alkaline medium. This treatment promotes the PLA removal (insulating layer) and exposes carbon black (CB) conductive sites. The pH and the square-wave anodic stripping voltammetry technique were carefully adjusted to optimize the method. The peaks for Zn2+ and UA were well-defined at around − 1.1 V and + 0.45 V (vs. CB/PLA pseudo-reference), respectively, using the treated surface under optimized conditions. The calibration curve showed a linear range of 1 to 70 µg L−1 and 1 to 70 µmol L−1 for Zn2+ and UA, respectively. Relative standard deviation values were estimated as 4.8% (n = 10, 30 µg L−1) and 6.1% (n = 10, 30 µmol L−1) for Zn2+ and UA, respectively. The detection limits for Zn2+ and UA were 0.10 µg L−1 and 0.28 µmol L−1, respectively. Both species were determined simultaneously in real sweat samples, and the achieved recovery percentages were between 95 and 106% for Zn2+ and 82 and 108% for UA.

We study the interaction and metalation reaction of a free base 5,10,15,20‐terakis(4‐cyanophenyl)porphyrin (2HTCNPP) with post‐deposited Zn atoms and the targeted reaction product Zn‐5,10,15,20‐terakis(4‐cyanophenyl)porphyrin (ZnTCNPP) on a Ag(111) surface. The investigations are performed with scanning tunneling microscopy at room temperature after Zn deposition and subsequent heating. The goal is to obtain further insights in the metalation reaction and the influence of the cyanogroups on this reaction. The interaction of 2HTCNPP with post‐deposited Zn leads to the formation of three different 2D ordered island types that coexist on the surface. All contain a new species with a bright appearance, which increases with the amount of post‐deposited Zn. We attribute this to metastable SAT (“sitting atop”) complexes formed by Zn and the macrocycle, that is, an intermediate in the metalation reaction to ZnTCNPP, which occurs upon heating to 500 K. Interestingly, the activation barrier for the successive reaction of the SAT complex to the metalated ZnTCNPP species can also be overcome by a voltage pulse applied to the STM tip., Metalation with zinc: Post‐deposition of Zn onto 2HTCNPP leads to the formation of a SAT complex, which reacts to ZnTCNPP upon heating or application of a voltage pulse.

The interaction of Fe deposited on graphene grown on Ir(111) was studied in detail to better understand the growth, intercalation, and oxidation of Fe ultrathin films on and under graphene. The stu...

We report the development of flexible self-supported metal-free electrodes based on non-oxidized graphene multilayer (MLG) paper, utilized to assemble bendable electrochemical supercapacitors. Using a simplified production method various electrodes exhibiting high conductivity were prepared and its structural, morphological, chemical and electrical properties characterized. Measurements in supercapacitors assembled from MLG electrodes and PANI-coated MLG electrodes show excellent electrochemical characteristics, with specific capacitances of 58 mF cm−2 and 451 F g−1 with 84% and 103% of capacitance retention after 1000 cycles, respectively. The energy and power density obtained for the PANI/MLG flexible supercapacitor reached 17.0 Wh g−1 and 3.61 kW kg−1, respectively. Moreover, in bending tests, the supercapacitors displayed an excellent mechanical and electrochemical stability. As an important result of this study, MLG electrodes appear as an interesting material for flexible high performance energy storage devices.

Made available in DSpace on 2018-12-11T17:36:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The production of large-area interfaces and the use of scalable methods to build up designed nanostructures generating advanced functional properties are of high interest for many materials science applications. Nevertheless, large-area coverage remains a major problem even for pristine graphene, and here we present a hybrid, composite graphene-like material soluble in water that can be exploited in many areas such as energy storage, electrodes fabrication, selective membranes and biosensing. Graphene oxide (GO) was produced by the traditional Hummers’ method being further reduced in the presence of poly(styrene sulfonate) sodium salt (PSS), thus creating stable reduced graphene oxide (rGO) nanoplatelets wrapped by PSS (GPSS). Molecular dynamics simulations were carried out to further clarify the interactions between PSS molecules and rGO nanoplatelets, with calculations supported by Fourier transform infrared spectroscopy analysis. The intermolecular forces between rGO nanoplatelets and PSS lead to the formation of a hybrid material (GPSS) stabilized by van der Waals forces, allowing the fabrication of high-quality layer-by-layer (LbL) films with poly(allylamine hydrochloride) (PAH). Raman and electrical characterizations corroborated the successful modifications in the electronic structures from GO to GPSS after the chemical treatment, resulting in (PAH/GPSS) LbL films four orders of magnitude more conductive than (PAH/GO). POSMAT – Programa de Pós-Graduação em Ciência e Tecnologia de Materiais UNESP – Univ Estadual Paulista Universidade Federal de São Carlos – DFQM Faculdade de Engenharia de Sorocaba – FACENS Applied Physics Department State University of Campinas UNESP – Univ Estadual Paulista Centro Universitário Central Paulista – UNICEP Instituto de Física de São Carlos – USP POSMAT – Programa de Pós-Graduação em Ciência e Tecnologia de Materiais UNESP – Univ Estadual Paulista UNESP – Univ Estadual Paulista FAPESP: 2010/13033-6 FAPESP: 2012/01484-9 FAPESP: 2015/14703-9 FAPESP: 2016/00023-9 FAPESP: 2016/12340-9

Conductive 3D-printed platforms have been recognized an emerging class of materials with great potential to electrochemistry. However, such 3D-printed electrodes require a surface treatment to remove excess of polymer that hinders the electron transfer. We report a fast (2-min) and chemical-free protocol for the surface treatment of 3D-printed conductive electrodes based on reactive cold oxygen plasma. A dramatic improvement of electrochemical activity of 3D-printed carbon black-polylactic acid (CB-PLA) electrodes was verified by the decrease in the peak-to-peak separation of the voltammetric response for the [Fe(CN)6]3-/[Fe(CN)6]4- couple and in the resistance of change transfer. The O2-plasma treatment increased oxide groups and graphitic groups at the CB-PLA surface (verified by XPS) and provided higher rugosity (SEM images) thus higher exposure of conducting carbon sites and increased electroactive area in comparison with CO2-plasma, which explains the improved electrochemical performance using O2-plasma treated electrodes. This protocol is faster and provided improved electrochemical activity compared with electrochemical, chemical, or biological treatments. As proofs-of concept, the benefits of surface plasma treatment of the 3D-printed electrodes were demonstrated towards the electrochemical sensing of dopamine and nitrite, molecules of biological interest, including the analysis of human saliva. Values of sensitivity and detection limit were greatly improved when using O2-plasma treatment for both molecules (up to 100-fold increase in sensitivity for the voltammetric detection of dopamine), suggesting great promises for the development of highly-sensitive electrochemical sensors.

The reactive plasma technique is often employed to activate the surface of materials both chemically and physically. Considering that several parameters should be handled in a plasma treatment process, a multivariate experimental design of three factors in two levels was employed to define the plasma treatment configurations under which the MLG were submitted. Plasma intensity, partial pressure of oxygen and reaction time were employed in the experimental planning. The surface morphology, the generation of C–C bond defects, surface chemical composition, interfacial free energy, and electrochemical properties were analyzed for the MLG electrodes as a function of the plasma treatment parameters. The treatments effectively promoted the MLG electrode's surface activation, considering the results obtained, which showed a dependence on those plasma treatment variables. The results suggested that plasma treatment variable adjustments can be used to modulate specific surface properties and with potential applicability in electrochemical sensors and supercapacitors.

This study fabricated a portable, high-performance, and reagentless electrochemical devices using CO2 laser-scribing process, which allowed localized carbonization of a non-conductive and low-cost polymer platform, i.e., phenolic-paper. The carbonized material was extensively characterized by Raman spectroscopy, XPS, XRD, SEM, and electrochemical impedance spectroscopy. The carbon-based electrodes were obtained from the photothermal process induced by CO2 laser radiation and subsequently subjected to electrochemical treatment to fabricate a functional material with excellent conductivity and low charge-transfer resistance. Additionally, the laser-scribed electrodes presented a porous structure with graphene-like domains, thus indicating both potential for on-site electroanalytical applications and better performance than conventional carbon electrodes.

CoCrMo alloys have been used for several decades in implantable devices due to their favourable mechanical properties, low wear rate in addition to good biocompatibility and high corrosion resistance. These alloys are conventionally produced via casting and/or forging route, however additive manufacturing techniques being recently employed in their fabrication. In this work, CoCrMo samples were produced by direct metal laser sintering additive manufacturing process. The microstructure and surface composition were examined employing scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy (XPS). The corrosion resistance was measured in 0.14 M sodium chloride solution and in phosphate buffered solution (PBS) both with and without addition of albumin at pH 7.4 and 37 °C. For this, potentiodynamic tests in addition to electrochemical impedance spectroscopy were employed. The studied CoCrMo alloy exhibits a good corrosion resistance in solutions tested being the highest in PBS solution without albumin addition. The XPS analysis showed that the passive film composition and its thickness are not modified by the adsorbed layer. Microstructural analysis revealed occurrence of strain-induced martensitic transformation.

Neste projeto foram explorados aspectos fundamentais da adsorcao da molecula 5,10,15,20-(tetra-4-trifluoromethylphenyl)porphyrin (2H-FTPP) sobre Cu(111), tais como sua configuracao de adsorcao, mobilidade, variacao das especies quimicas presentes, pois se trata de uma molecula sem material literario. Atraves de espectros de XPS, foi observada a dehalogenacao da molecula atraves do aquecimento da amostra, que e uma das etapas para ocorrencia da reacao de Ullmann. Alem disso, ao final serao obtidas as energias de barreira de translacao e rotacao sobre o Cu(111).

Dicalcogenetos de metais de transicao (TMD) quando em monocamadas tem recebido forte atencao nos ultimos anos. Para isto, o metodo mais empregado e a esfoliacao mecânica, que nao permite produzir monocamadas de uma forma escalavel para producao industrial. Para tanto, faz-se necessario desenvolver metodos de crescimento de filmes finos de TMD utilizando tecnicas como a Molecular Beam Epitaxy - MBE. Este projeto se deteve na producao de filmes finos de MoTe? sobre Gr/Ir(111) pela tecnica de MBE, a posterior caracterizacao estrutural foi realizada por X-ray Photoelectron Spectroscopy - XPS e Scanning Tunneling Microscopy - STM. Os resultados indicam a intercalacao de Te entre o Gr/Ir(111), gerando regioes de menor corrugacao, e a formacao de nanoilhas de MoTe?.

This paper proposes an applied and innovative research for the development of Nb2O5 thin film on the Ti6Al4V alloy surface with great prospects of being used in the biomedical area. Thin films of Nb2O5 have been deposited on the Ti6Al4V alloy surface by using the reactive sputtering technique. The system was characterized morphologically and structurally via SEM/EDX, AFM, FTIR, Raman spectroscopy and XPS. Interfacial tension theory was used for the determination of the surface free energy and showed that the treated surface became more hydrophilic when compared to the bare material. The high-resolution X-ray photoelectron spectra from Nb 3d and O 1s core-levels demonstrate unequivocally the presence of a single-phase Nb2O5. Cytotoxicity and biocompatibility (VERO-CCL-81 cell line) tests as well as analyzes of inflammatory responses with Human blood leukocyte cells were also performed by showing that Nb2O5 coating reduced both Ti6Al4V alloy toxicity and its inflammation induction besides increasing the anti-inflammatory cytokine levels. Since the surface functionalization resulted in both higher biocompatibility and tolerance by immune cells besides low inflammatory levels concerning the base material, we present a superior material with wide spectra of usage in the biomedical area.

The plethora of new transition metal dichalcogenides (TMDs) materials have attracted a major attention during the last years due to a diversity of new possibilities of applications in different areas from electronic and photonic devices to new sensors and catalysts, as well as a large playground of 2D materials to explore new physical phenomena. Many efforts have been done to develop new growth techniques that can produce single-layer TMDs in large areas and with high quality (low density of defects). Another important issue for electronic device integration is how to perform electrical contacts that show a metallic behavior instead semiconductor junctions. In this work, we have systematically studied the epitaxial growth of MoS 2 on Ag(1 1 1) using the physical vapor deposition method (PVD). The results, based on a multiple technique approach, demonstrate that is possible to produce a single-layer 1 H - MoS 2 film on Ag(1 1 1). The material presents a metallic behavior due to an electronic hybridization between the MoS 2 states and the Ag(1 1 1) states as results of the strong TMD-substrate interaction at the interface. This metallic character is preserved even after exposure to atmosphere and hostile oxidation environment which indicates that silver is probably an excellent candidate to perform metal contacts on sulfur-based TMDs.

The photoelectron diffraction (PED) is an element and chemical selective technique, which have been used for surface structure determinations. Due the complexity phenomena of low-energy photoelectron diffraction, obtain the structure by holographic inversion method from the experimental data present difficulties which unfeasible the method. To perform a structure determination It s necessary use the comparative method between the experimental and theoretical data from a hypothetical structure in a try-and-error approach, which could spent high computational time. In this project we have developed a Particle Swarm Optimization (PSO) algorithm for structural determination using the PED technique.

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The reaction rate of the self-metalation of free-base tetraphenylporphyrins (TPPs) on Cu(111) increases with the number of cyano groups (n=0, 1, 2, 4) attached at the para positions of the phenyl rings. The findings are based on isothermal scanning tunneling microscopy (STM) measurements. At room temperature, all investigated free-base TPP derivatives adsorb as individual molecules and are aligned with respect to densely packed Cu substrate rows. Annealing at 400 K leads to the formation of linear dimers and/or multimers via CN-Cu-CN bonds, accompanied by self-metalation of the free-base porphyrins following a first-order rate equation. When comparing the non-cyano-functionalized and the tetracyano-functionalized molecules, we find a decrease of the reaction rate by a factor of more than 20, corresponding to an increase of the activation energy from 1.48 to 1.59 eV. Density functional theory (DFT) calculations give insights into the influence of the peripheral electron-withdrawing cyano groups and explain the experimentally observed effects.

The growth and self-assembling properties of nickel-tetraphenyl porphyrins (NiTPP) on the Cu(111) surface are analysed via scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). For low coverage, STM results show that NiTPP molecules diffuse on the terrace until they reach the step edge of the copper surface forming a 1D system with disordered orientation along the step edges. The nucleation process into a 2D superstructure was observed to occur via the interaction of molecules attached to the already nucleated 1D structure, reorienting molecules. For monolayer range coverage a 2D nearly squared self-assembled array with the emergence of chiral domains was observed. The XPS results of the Ni 2p(3/2) core levels exhibit a 2.6 eV chemical shift between the mono- and multilayer configuration of NiTPP. DFT calculations show that the observed chemical shifts of Ni 2p(3/2) occur due to the interaction of 3d orbitals of Ni with the Cu(111) substrate.

We studied by soft X-ray absorption spectroscopy the magnetization axis in a 4 nm thin CoO (111) layer exchange-coupled to an ultra thin L 1 0 PtFe layer with perpendicular magnetic anisotropy. The angular dependence of the linear magnetic dichroism at 10 K and the relative variations of the spectral features provide a full description of the spin orientation in this antiferromagnetic layer. The spins are found in the film plane, pointing along the 110 direction. This results is discussed in relation to the film strain and the preferential occupation of t 2 g orbitals. The strong orthogonal coupling between Co and Fe spins should be at the origin of the robustness of the exchange bias effect found in this bilayer system.

Based on density functional theory calculations combined with experimental results, we report and discuss an extremely distorted, “inverted” adsorption geometry of free-base tetraphenylporphyrin on Cu(111). The current findings yield new insights into a well-studied system, shedding light on the peculiar molecule–substrate interaction and the resulting intramolecular conformation.

This work aims to investigate the chemical and biological responses of a-C:H films produced by PECVD technique onto substrate of Ti6Al4V alloy. The films produced were characterized morphologically and structurally by optical microscope (OM), SEM, AFM, EDX, FTIR Raman Spectroscopy (RS) and XPS. Afterwards, biocompatibility and cytotoxicity tests on osteoblastic cells and/or Human Peripheral Blood Mononuclear Cells (PBMCs) were performed on the Ti6Al4V alloy with coated and uncoated a-C:H film. The ID/IG ratio about 0.71 suggests a hydrogenated amorphous carbon film (a-C:H). The deconvoluted XPS spectra of C 1s peaks disclose the presence of three main components: C1 associated to C C bonds in one sp2 hybridization as well as C2 associated to sp3 hybridization. The impedance results showed that a-C:H film acts as a protective barrier against the corrosion process. Regardless of the cell population, when the total apoptosis of osteoblastic cells or PBMCs was evaluated, only cells cultured on the alloy without a-C:H had significant induction of the apoptotic process. Moreover, only PBMCs cultured on the alloy without a-C:H had significant induction of inflammatory and anti-inflammatory cytokines that characterize immune activation.

A detailed investigation concerning the atomic structure of Cr2O3 and Pd/Cr2O3 ultrathin films deposited on a Ag(111) single crystal is presented. The films were prepared by MBE (molecular beam epi...

Agradecimentos: This work received financial support from FAPESP, CNPq, and CAPES from Brazil. XMCD measurements were done at LNLS under proposal #PGM12561. L.H.L. thanks CNPq for PhD studentship support. Authors thank Lucas Barreto and George G. Kleiman for discussion as well as LNLS staff for technical support during beamtime Abstract: The behavior of Co nanoparticles (NPs) grown on graphene/SiC(0001) after oxygen exposure and heating in ultrahigh vacuum is investigated. The results of photoelectron spectroscopy (XPS) show that, as grown, the metal is on the surface of the graphene/SiC and suffers oxidation forming a single phase CoO when exposed to O2, even at low doses. After heating in ultrahigh vacuum (UHV), there is a deoxidation of cobalt and intercalation between the graphene (G) and the buffer layer (BL), as indicated by scanning tunneling microscopy (STM) and XPS. Cobalt forms almost regular small 2D clusters between G and BL. Moreover, graphene acts as a barrier to oxidation, preserving the metallic and the magnetic character of the material even when exposed to O2. This paper shows a method for patterning chemically protected Co NPs on graphene/SiC(0001) which could be used in nanomagnetism based devices FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado

Metallic surfaces involving transition metals are widely used in the preparation of catalysts. The conversion rates and the selectivity can be improved, in many instances, by a surface alloy formed by a transition metal with a less reactive sp metal. Bimetallic systems based on Pd In have been shown to be efficient catalysts for methanol steam reforming and nitrate reduction in water. The catalytic reaction depends on both the electronic structure and the geometric arrangement of the surface alloy atoms. In and Pd have very limited miscibility in the bulk but can form ordered surface alloys. We have investigated the growth and the surface alloy formation of an ultra-thin film of In deposited on a Pd(111) single-crystal substrate surface. The electronic structure and the surface composition have been characterized by X-ray photoelectron spectroscopy (XPS), and the atomic surface structure has been determined by a combination of low energy electron diffraction (LEED) and X-ray photoelectron diffraction (XPD). Ultra-thin films of In having approximately 1 to 5 monolayers (ML) were deposited at room temperature, and then annealed at 500 K. Pd 3d and In 3d intensities obtained by XPS indicated the Stranski-Krastanov growth mode, i.e. flat bi-dimensional overlayers in the first layer followed by three-dimensional islands. For annealed In films having 0.33 to 2.5 ML, a ( 3 x 3 )R30° LEED pattern was observed. For a non-annealed In film having approximately 3 ML, a p(2 × 2) LEED pattern was observed, that changed to ( 3 x 3 )R30° upon annealing at 500 K. For a slightly higher coverage, about 3.6 ML, a (1 × 1) pattern was obtained after annealing. XPS results for the annealed ~3.6 ML film indicate the diffusion of In atoms into the outermost layers of the Pd(111) single-crystal. For the same In film, XPD indicated the formation of bidimensional In islands, with some bare patches of the substrate.

Two single crystalline surfaces of Au vicinal to the (111) plane were modified with Pt and studied using scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) in ultra-high vacuum environment. The vicinal surfaces studied are Au(332) and Au(887) and different Pt coverage (θPt) were deposited on each surface. From STM images we determine that Pt deposits on both surfaces as nanoislands with heights ranging from 1 ML to 3 ML depending on θPt. On both surfaces the early growth of Pt ad-islands occurs at the lower part of the step edge, with Pt ad-atoms being incorporated into the steps in some cases. XPS results indicate that partial alloying of Pt occurs at the interface at room temperature and at all coverage, as suggested by the negative chemical shift of Pt 4f core line, indicating an upward shift of the d-band center of the alloyed Pt. Also, the existence of a segregated Pt phase especially at higher coverage is detected by XPS. Sample annealing indicates that the temperature rise promotes a further incorporation of Pt atoms into the Au substrate as supported by STM and XPS results. Additionally, the catalytic activity of different PtAu systems reported in the literature for some electrochemical reactions is discussed considering our findings.