Blue phosphorene on Au(111): theoretical, spectroscopic and diffraction analysis reveal the role of single Au adatoms.

In investigating the monoatomic layers of P, several stable two-dimensional (2D) allotropes have been theoretically predicted. Among them, single-layer blue phosphorus (BlueP) appears to deliver promising properties. After initial success, where the structure of BlueP triangular patches on Au(111) was conceived on the basis of scanning tunneling microscopy (STM) and density functional theory (DFT), the surface structure model was revisited multiple times with increasing accuracy and insight of theoretical calculations and experimental datasets.

Catalytic Ozonation of Polluter Benzene from -20 to >50 °C with High Conversion Efficiency and Selectivity on Mullite YMnO.

Catalytic decomposition of aromatic polluters at room temperature represents a green route for air purification but is currently challenged by the difficulty of generating reactive oxygen species (ROS) on catalysts. Herein, we develop a mullite catalyst YMnO (YMO) with dual active sites of Mn and Mn and use ozone to produce a highly reactive O* upon YMO. Such a strong oxidant species on YMO shows complete removal of benzene from -20 to >50 °C with a high CO selectivity (>90%) through the generated reactive species O* on the catalyst surface (60 000 mL g h).

Carbide coating on nickel to enhance the stability of supported metal nanoclusters.

The influence on the growth of cobalt (Co)-based nanostructures of a surface carbide (NiC) layer formed at the Ni(100) surface is revealed complementary scanning tunneling microscopy (STM) measurements and first-principles calculations. On clean Ni(100) below 200 °C in the sub-monolayer regime, Co forms randomly distributed two-dimensional (2D) islands, while on NiC it grows in the direction perpendicular to the surface as well, thus forming two-atomic-layers high islands. We present a simple yet powerful model that explains the different Co growth modes for the two surfaces.

Mechanism of CO Intercalation through the Graphene/Ni(111) Interface and Effect of Doping.

Molecules intercalate at the graphene/metal interface even though defect-free graphene is impermeable to any atomic and molecular species in the gas and liquid phase, except hydrogen. The mechanism of molecular intercalation is still a big open question. In this Letter, by means of a combined experimental (STM, XPS, and LEED) and theoretical (DFT) study, we present a proof of how CO molecules succeed in permeating the graphene layer and get into the confined zone between graphene and the Ni(111) surface.

Doping of epitaxial graphene by direct incorporation of nickel adatoms.

Direct incorporation of Ni adatoms during graphene growth on Ni(111) is evidenced by scanning tunneling microscopy. The structure and energetics of the observed defects is thoroughly characterized at the atomic level on the basis of density functional theory calculations. Our results show the feasibility of a simple scalable method, which could be potentially used for the realization of macroscopic practical devices, to dope graphene with a transition metal.

Prediction of self-assembly of adenosine analogues in solution: a computational approach validated by isothermal titration calorimetry.

The recent discovery of the role of adenosine-analogues as neuroprotectants and cognitive enhancers has sparked interest in these molecules as new therapeutic drugs. Understanding the behavior of these molecules in solution and predicting their ability to self-assemble will accelerate new discoveries. We propose a computational approach based on density functional theory, a polarizable continuum solvation description of the aqueous environment, and an efficient search procedure to probe the potential energy surface, to determine the structure and thermodynamic stability of molecular clusters of adenosine analogues in solution, using caffeine as a model.

Substrate- to Laterally-Driven Self-Assembly Steered by Cu Nanoclusters: The Case of FePcs on an Ultrathin Alumina Film.

We show that, for the formation of a metallorganic monolayer, it is possible to artificially divert from substrate- to laterally-driven self-assembly mechanisms by properly tailoring the corrugation of the potential energy surface of the growth template. By exploiting the capability of an ultrathin alumina film to host metallic nanoparticle seeds, we tune the symmetry of a iron phthalocyanine (FePc) two-dimensional crystal, thus showing that it is possible to switch from trans to lateral dominating interactions in the controlled growth of an organic/inorganic heterostack. Finally, by selecting the size of the metallic clusters, we can also control the FePc-metal interaction strength.

Real-time imaging of adatom-promoted graphene growth on nickel.

Single adatoms are expected to participate in many processes occurring at solid surfaces, such as the growth of graphene on metals. We demonstrate, both experimentally and theoretically, the catalytic role played by single metal adatoms during the technologically relevant process of graphene growth on nickel (Ni). The catalytic action of individual Ni atoms at the edges of a growing graphene flake was directly captured by scanning tunneling microscopy imaging at the millisecond time scale, while force field molecular dynamics and density functional theory calculations rationalize the experimental observations.

Tunability of the CO adsorption energy on a Ni/Cu surface: Site change and coverage effects.

The adsorption energy of carbon monoxide on Ni ad-islands and ultra-thin films grown on the Cu(110) surface can be finely tuned via a complex interplay among diffusion, site change mechanisms, and coverage effects. The observed features of CO desorption can be explained in terms of migration of CO molecules from Cu to Ni islands, competition between bridge and on-top adsorption sites, and repulsive lateral adsorbate-adsorbate interactions. While the CO adsorption energy on clean Cu(110) is of the order of 0.

Experimental and Theoretical Investigation of the Restructuring Process Induced by CO at Near Ambient Pressure: Pt Nanoclusters on Graphene/Ir(111).

The adsorption of CO on Pt nanoclusters grown in a regular array on a template provided by the graphene/Ir(111) Moiré was investigated by means of infrared-visible sum frequency generation vibronic spectroscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy from ultrahigh vacuum to near-ambient pressure, and ab initio simulations. Both terminally and bridge bonded CO species populate nonequivalent sites of the clusters, spanning from first to second-layer terraces to borders and edges, depending on the particle size and morphology and on the adsorption conditions. By combining experimental information and the results of the simulations, we observe a significant restructuring of the clusters.

Correction: Study of structures and thermodynamics of CuNi nanoalloys using a new DFT-fitted atomistic potential.

Correction for 'Study of structures and thermodynamics of CuNi nanoalloys using a new DFT-fitted atomistic potential' by Emanuele Panizon et al., Phys. Chem.

Trapping of Charged Gold Adatoms by Dimethyl Sulfoxide on a Gold Surface.

We report the formation of dimethyl sulfoxide (DMSO) molecular complexes on Au(111) enabled by native gold adatoms unusually linking the molecules via a bonding of ionic nature, yielding a mutual stabilization between molecules and adatom(s). DMSO is a widely used polar, aprotic solvent whose interaction with metal surfaces is not fully understood. By combining X-ray photoelectron spectroscopy, low temperature scanning tunneling microscopy, and density functional theory (DFT) calculations, we show that DMSO molecules form complexes made by up to four molecules arranged with adjacent oxygen terminations.

Towards optimal seeding for the synthesis of ordered nanoparticle arrays on alumina/Ni₃Al(111).

The adsorption and the nucleation of different transition metals (Fe, Co, Ni, Cu, Pd, Ag, and Au) on alumina/Ni3Al(111) have been studied to shed light on the first stages of the synthesis of supported nanoparticles, focusing in particular on the possibility of producing ordered arrays. Affinity for oxygen, atomic radii, electronic properties and kinetics have been taken into account to rationalize the different behavior. In agreement with empirical findings, Pd is confirmed to be the best choice for a highly ordered nucleation following the "dot" superstructure of the alumina, due to a remarkable preference for the corresponding adsorption sites (holes) with respect to others, and for a rather strong binding.

Study of structures and thermodynamics of CuNi nanoalloys using a new DFT-fitted atomistic potential.

Shape, stability and chemical ordering patterns of CuNi nanoalloys are studied as a function of size, composition and temperature. A new parametrization of an atomistic potential for CuNi is developed on the basis of ab initio calculations. The potential is validated against experimental bulk properties, and ab initio results for nanoalloys of sizes up to 147 atoms and for surface alloys.

Temperature-driven changes of the graphene edge structure on Ni(111): substrate vs hydrogen passivation.

Atomic-scale description of the structure of graphene edges on Ni(111), both during and post growth, is obtained by scanning tunneling microscopy (STM) in combination with density functional theory (DFT). During growth, at 470 °C, fast STM images (250 ms/image) evidence graphene flakes anchored to the substrate, with the edges exhibiting zigzag or Klein structure depending on the orientation. If growth is frozen, the flake edges hydrogenate and detach from the substrate, with hydrogen reconstructing the Klein edges.

Self-seeded nucleation of Cu nanoclusters on Al2O3/Ni3Al(111): an ab initio investigation.

The mechanisms of seeding and nucleation of Cu nanoclusters onto an ultrathin alumina template supported on Ni3Al(111) has been investigated by means of ab initio calculations. Single Cu ad-atom diffusion on the oxide film is effective at room temperature, allowing preferential occupation of the defective sites of the so-called "dot" structure, where the adsorption is much stronger than in the "network" or any other surface site of the oxide. After the adsorption of the first Cu atom, further nucleation at the "dot" sites proceeds with the formation of multi-atomic seeds (with up to 6 atoms contained in the defect) that offer stiff anchoring for larger clusters.

Atomic Scale Identification of Coexisting Graphene Structures on Ni(111).

Through a combined scanning tunneling microscopy (STM) and density functional theory (DFT) approach, we provide a full characterization of the different chemisorbed configurations of epitaxial graphene coexisting on the Ni(111) single crystal surface. Top-fcc, top-hcp, and top-bridge are found to be stable structures with comparable adsorption energy. By comparison of experiments and simulations, we solve an existing debate, unambiguously distinguishing these configurations in high-resolution STM images and characterizing the transitions between adjacent domains.

Tailoring bimetallic alloy surface properties by kinetic control of self-diffusion processes at the nanoscale.

Achieving control of the nanoscale structure of binary alloys is of paramount importance for the design of novel materials with specific properties, leading to, for example, improved reaction rates and selectivity in catalysis, tailored magnetic behavior in electronics, and controlled growth of nanostructured materials such as graphene. By means of a combined experimental and theoretical approach, we show that the complex self-diffusion mechanisms determining these key properties can be mostly defined by kinetic rather than energetic effects. We explain how in the Ni-Cu system nanoscale control of self-diffusion and segregation processes close to the surface can be achieved by finely tuning the relative concentration of the alloy constituents.