Intact water adsorption on Co(0001) at 100 K: transition from ordered bilayer to amorphous ice structures.

While cobalt metal is recognized as a versatile catalyst in various chemical reactions, such as Fischer-Tropsch synthesis, limited attention has been paid to understanding the detailed adsorptive interactions between water molecules and cobalt metal. In this study, we investigated the adsorption of water molecules on Co(0001) at 100 K using infrared reflection adsorption spectroscopy and low-energy electron diffraction. We experimentally revealed, for the first time, that DO adsorbed intact on the Co(0001) surface forms hexamer islands with coexisting D-up and D-down geometries, in line with the "ice bilayer" model.

Interaction of Gallium with a Copper Surface: Surface Alloying and Formation of Ordered Structures.

Alloys of gallium with transition metals have recently received considerable attention for their applications in microelectronics and catalysis. Here, we investigated the initial stages of the Ga-Cu alloy formation on Cu(111) and Cu(001) surfaces using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). The results show that Ga atoms deposited using physical vapor deposition readily intermix with the Cu surface, leading to a random distribution of the Ga and Cu atoms within the surface layer, on both terraces and monolayer-thick islands formed thereon.

Two-Dimensional Ultrathin Silica Films.

Two-dimensional (2D) ultrathin silica films have the potential to reach technological importance in electronics and catalysis. Several well-defined 2D-silica structures have been synthesized so far. The silica bilayer represents a 2D material with SiO stoichiometry.

CsPbBr microarrays with tunable periodicity, optoelectronic and field emission properties using self-assembled polystyrene template and co-evaporation method.

The booming growth of all inorganic cesium lead halide perovskites in optoelectronic applications has prompted extensive research interest in the fabrication of ordered nanostructures or microarrays for enhanced device performances. However, the high cost and complexity of commercial lithographic approaches impede the facile fabrication of perovskite microarrays. Herein, CsPbBr microarrays with tunable periodicities have been fabricated using a self-assembled polystyrene nanosphere template and a co-evaporation method.

Operando high-pressure investigation of size-controlled CuZn catalysts for the methanol synthesis reaction.

Although Cu/ZnO-based catalysts have been long used for the hydrogenation of CO to methanol, open questions still remain regarding the role and the dynamic nature of the active sites formed at the metal-oxide interface. Here, we apply high-pressure operando spectroscopy methods to well-defined Cu and CuZn nanoparticles supported on ZnO/AlO, γ-AlO and SiO to correlate their structure, composition and catalytic performance. We obtain similar activity and methanol selectivity for Cu/ZnO/AlO and CuZn/SiO, but the methanol yield decreases with time on stream for the latter sample.

Structural Evolution of Ga-Cu Model Catalysts for CO Hydrogenation Reactions.

We studied the initial stages of Ga interaction with the Cu(001) surface and environment-induced surface transformations in an attempt to elucidate the surface chemistry of the Cu-Ga catalysts recently proposed for CO hydrogenation to methanol. The results show that Ga readily intermixes with Cu upon deposition in vacuum. However, even traces of oxygen in the gas ambient cause Ga oxidation and the formation of two-dimensional ("monolayer") Ga oxide islands uniformly covering the Cu surface.

Interaction of Hydrogen with Ceria: Hydroxylation, Reduction, and Hydride Formation on the Surface and in the Bulk.

The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO ) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO (111) thin films and CeO powders, and theoretical calculations of CeO (111) surfaces with oxygen vacancies (O ) at the surface and in the bulk.

CORM-3 Regulates Microglia Activity, Prevents Neuronal Injury, and Improves Memory Function During Radiation-induced Brain Injury.

Objective: This study aims to explore in detail, the mechanism of the carbon monoxide releasing molecule-3 (CORM-3) in regulating the activity of microglia (MG) in the treatment of radiation brain injury (RBI).

Methods: The brain injury models of BV2 cells and Balb/C mice were established and randomly divided into three groups: the normal control group (CON), the single radiation group (RAD), and the radiation plus CORM-3 intervention group (RAD+CORM). Immunofluorescence was used to observe the effects on activation of the MG.

Water-Assisted Homolytic Dissociation of Propyne on a Reduced Ceria Surface.

The emergence of ceria (CeO ) as an efficient catalyst for the selective hydrogenation of alkynes has attracted great attention. Intensive research effort has been devoted to understanding the underlying catalytic mechanism, in particular the H -CeO interaction. Herein, we show that the adsorption of propyne (C H ) on ceria, another key aspect in the hydrogenation of propyne to propene, strongly depends on the degree of reduction of the ceria surface and hydroxylation of the surface, as well as the presence of water.

Isolating the Roles of Hydrogen Exposure and Trace Carbon Contamination on the Formation of Active Catalyst Populations for Carbon Nanotube Growth.

Limited understanding of the factors influencing the yield of carbon nanotubes (CNTs) relative to the number of catalyst particles remains an important barrier to their large-scale production with high quality, and to tailoring CNT properties for applications. This lack of understanding is evident in the frequent use of Edisonian approaches to give high-yield CNT growth, and in the sometimes-confusing influence of trace residues on the reactor walls. In order to create conditions wherein CNT yield is reproducible and to enable large-scale and reliable CNT synthesis, it is imperative to understand-fundamentally-how these common practices impact catalytic activity and thus CNT number density.

Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems.

The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy.

Probing the effect of the Pt-Ni-Pt(111) bimetallic surface electronic structures on the ammonia decomposition reaction.

We report a detailed investigation of elementary catalytic decomposition of ammonia on the Pt-Ni-Pt(111) bimetallic surface using in situ near ambient pressure X-ray photoelectron spectroscopy. Under the near ambient pressure (0.6 mbar) reaction conditions, a different dehydrogenation pathway with a reduced activation energy barrier for recombinative nitrogen desorption on the Pt-Ni-Pt(111) bimetallic surface is observed.

Reversible Tuning of Interfacial and Intramolecular Charge Transfer in Individual MnPc Molecules.

The reversible selective hydrogenation and dehydrogenation of individual manganese phthalocyanine (MnPc) molecules has been investigated using photoelectron spectroscopy (PES), low-temperature scanning tunneling microscopy (LT-STM), synchrotron-based near edge X-ray absorption fine structure (NEXAFS) measurements, and supported by density functional theory (DFT) calculations. It is shown conclusively that interfacial and intramolecular charge transfer arises during the hydrogenation process. The electronic energetics upon hydrogenation is identified, enabling a greater understanding of interfacial and intramolecular charge transportation in the field of single-molecule electronics.

Single-molecule imaging of activated nitrogen adsorption on individual manganese phthalocyanine.

An atomic-scale understanding of gas adsorption mechanisms on metal-porphyrins or metal-phthalocyanines is essential for their practical application in biological processes, gas sensing, and catalysis. Intensive research efforts have been devoted to the study of coordinative bonding with relatively active small molecules such as CO, NO, NH3, O2, and H2. However, the binding of single nitrogen atoms has never been addressed, which is both of fundamental interest and indeed essential for revealing the elementary chemical binding mechanism in nitrogen reduction processes.

Towards single molecule switches.

The concept of using single molecules as key building blocks for logic gates, diodes and transistors to perform basic functions of digital electronic devices at the molecular scale has been explored over the past decades. However, in addition to mimicking the basic functions of current silicon devices, molecules often possess unique properties that have no parallel in conventional materials and promise new hybrid devices with novel functions that cannot be achieved with equivalent solid-state devices. The most appealing example is the molecular switch.

Rational design of two-dimensional molecular donor-acceptor nanostructure arrays.

The construction of long-range ordered organic donor-acceptor nanostructure arrays over microscopic areas supported on solid substrates is one of the most challenging tasks towards the realization of molecular nanodevices. They can also be used as ideal model systems to understand light induced charge transfer, charge separation and energy conversion processes and mechanisms at the nanometer scale. The aim of this paper is to highlight recent advances and progress in this topic.

Energy level realignment in weakly interacting donor-acceptor binary molecular networks.

Understanding the effect of intermolecular and molecule-substrate interactions on molecular electronic states is key to revealing the energy level alignment mechanism at organic-organic heterojunctions or organic-inorganic interfaces. In this paper, we investigate the energy level alignment mechanism in weakly interacting donor-acceptor binary molecular superstructures, comprising copper hexadecafluorophthalocyanine (F16CuPc) intermixed with copper phthalocyanine (CuPc), or manganese phthalocynine (MnPc) on graphite. The molecular electronic structures have been systematically studied by in situ ultraviolet photoelectron spectroscopy (UPS) and low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS) experiments and corroborated by density functional theory (DFT) calculations.

Tissue culture-induced somaclonal variation of decreased pollen viability in torenia (Torenia fournieri Lind.).

Background: Phenotypic and genotypic variations, collectively called somaclonal variations, are induced during tissue culture.

Results: We studied the phenotypic variation in pollen viability of regenerants of torenia after subculturing for one to nine generations. We found that pollen viability of regenerants continuously decreased with increasing subculture time.

Tuning the Dirac point in CVD-grown graphene through solution processed n-type doping with 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole.

Controlling the Dirac point of graphene is essential for complementary circuits. Here, we describe the use of 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole (o-MeO-DMBI) as a strong n-type dopant for chemical-vapor-deposition (CVD) grown graphene. The Dirac point of graphene can be tuned significantly by spin-coating o-MeO-DMBI solutions on the graphene sheets at different concentrations.

The role of gap states in the energy level alignment at the organic-organic heterojunction interfaces.

The interface properties of organic-organic heterojunctions (OOHs), such as interface energy level alignment (ELA), interfacial charge transfer, interface nanostructuring, molecular orientation and so on, play an essential role in determining the device performance for some technologically important organic electronic devices, encompassing organic solar cells, bipolar organic field-effect-transistors, and organic light-emitting-diodes. The aim of this article is to provide a balanced assessment on the understanding of the ELA at the small-molecule based OOH interfaces with well-defined molecular orientation, with particular emphasis on the role of gap states in organic thin films. A generalized picture of gap states determined ELA at the OOH interfaces is provided and their implications in relevant organic electronic devices have been discussed.

CVD graphene as interfacial layer to engineer the organic donor-acceptor heterojunction interface properties.

We demonstrate the use of chemical-vapor-deposited (CVD) graphene as an effective indium-tin-oxide (ITO) electrode surface modifier to engineer the organic donor-acceptor heterojunction interface properties in an inverted organic solar cell device configuration. As revealed by in situ near-edge X-ray adsorption fine structure measurement, the organic donor-acceptor heterojunction, comprising copper-hexadecafluoro-phthalocyanine (F16CuPc) and copper phthalocyanine (CuPc), undergoes an obvious orientation transition from a standing configuration (molecular π-plane nearly perpendicular to the substrate surface) on the bare ITO electrode to a less standing configuration with the molecular π-plane stacking adopting a large projection along the direction perpendicular to the electrode surface on the CVD graphene-modified ITO electrode. Such templated less-standing configuration of the organic heterojunction could significantly enhance the efficiency of charge transport along the direction perpendicular to the electrode surface in the planar heterojunction-based devices.

Molecular-scale investigation of C60/p-sexiphenyl organic heterojunction interface.

In situ low-temperature scanning tunneling microscopy (LT-STM) and ultraviolet photoelectron spectroscopy (UPS) experiments have been carried out to investigate the interface properties at the C(60)∕p-sexiphenyl (6P) organic-organic heterojunction interface, including the interfacial energy level alignment and the supramolecular packing structures. As revealed by UPS measurements, the vacuum level is almost aligned at the C(60)∕6P interface, suggesting that the interface is dominated by weak intermolecular interactions, such as van der Waals and π-π interactions. In situ LT-STM experiments also indicate the formation of a molecularly sharp C(60)∕6P interface with hexagonally-close-packed C(60) layers nucleated atop 6P layer on graphite.