We present scanning tunneling microscopy results which reveal the existence of two distinct hydrogen dimer states on graphite basal planes. Density functional theory calculations allow us to identify the atomic structure of these states and to determine their recombination and desorption pathways. Direct recombination is only possible from one of the two dimer states. This results in increased stability of one dimer species and explains the puzzling double peak structure observed in temperature programmed desorption spectra for hydrogen on graphite.

We present scanning tunneling microscopy experiments and density functional theory calculations which reveal a unique mechanism for the formation of hydrogen adsorbate clusters on graphite surfaces. Our results show that diffusion of hydrogen atoms is largely inactive and that clustering is a consequence of preferential sticking into specific adsorbate structures. These surprising findings are caused by reduced or even vanishing adsorption barriers for hydrogen in the vicinity of already adsorbed H atoms on the surface and point to a possible novel route to interstellar H2 formation.

Nonsymmetrical organic molecules adsorbed on solid surfaces may assemble into random networks, thereby providing model systems for organic glasses that can be directly observed by scanning tunneling microscopy (STM). We investigated the structure of a disordered cytosine network on a gold(111) surface created by thermal quenching, to temperatures below 150 K, of the two-dimensional fluid present on the surface at room temperature. Comparison of STM images to density functional theory calculations allowed us to identify three elementary structural motifs (zigzag filaments and five- and six-membered rings) that underlie the whole supramolecular random network. The identification of elementary structural motifs may provide a new framework for understanding medium-range order in amorphous and glassy systems.

On-surface C-C coupling reactions of molecular precursors with alkynyl functional groups demonstrate great potential for the controllable fabrication of low-dimensional carbon nanostructures/nanomaterials, such as carbyne, graphyne, and graphdiyne, which demand the incorporation of highly active sp-hybridized carbons. Recently, through a dehydrogenative homocoupling reaction of alkynes, the possibility was presented to fabricate surface nanostructures involving acetylenic linkages, while problems lie in the fact that different byproducts are inevitably formed when triggering the reactions at elevated temperatures. In this work, by delicately designing the molecular precursors with terminal alkynyl bromide, we introduce the dehalogenative homocoupling reactions on the surface. As a result, we successfully achieve the formation of dimer structures, one-dimensional molecular wires and two-dimensional molecular networks with acetylenic scaffoldings on an inert Au(111) surface, where the unexpected C-Au-C organometallic intermediates are also observed. This study further supplements the database of on-surface dehalogenative C-C coupling reactions, and more importantly, it provides us an alternative efficient way for incorporating the acetylenic scaffolding into low-dimensional surface nanostructures.

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Oxygen quenching of [Ru(Ph2phen)3]Cl2 (Ph2phen = 4,7-diphenyl-1,10-phenanthroline) has been studied in a diverse series of polymers, most with a common poly-(dimethylsiloxane) (PDMS) component. Systematic variations in the polymer properties have been made in order to delineate the structural features important for satisfactory use of supports for oxygen sensors. Most measurements were made using homo- or copolymers containing a PDMS region, although some measurements were made on small ring siloxane polymers. In particular, quenching behavior was examined as a function of polymer structure as well as the type of and amount of polar copolymer cross-linkers. Cross-linkers were added to enhance the solubility of oxygen probes in an otherwise nonpolar polymer. In addition, hydrophobic silica was added to alter quenching properties. Domain models are used to explain the variations in oxygen quenching properties as a function of additives and cross-linkers. These considerations have led to the most sensitive ruthenium-based sensor reported to date. The relative affinity of the different domains for the complex and the efficacy of the domains for oxygen quenching control the overall behavior of the sensing response. Guidelines for design of suitable polymer supports for oxygen sensors are proposed.

The electron conductivity of electrode material has always been a problem that hinders the practical application of supercapacitor. In this contribution, we report a facile synthesis of highly conductive nickel cobalt oxide-single wall carbon nanotube (NiCo2O4–SWCNT) nanocomposite by controlled hydrolysis process in ethanol–water mixed solvent. Ultrafine NiCo2O4 nanocrystals with a diameter around 6–10 nm are formed on the functionalized SWCNT bundles. This novel material not only exhibits a high specific capacitance of 1642 F g–1 within a 0.45 V potential range but also shows an excellent cycling stability of 94.1% retention after 2000 cycles at high mass loading. Our method provides a promising facile and high-performance strategy for supercapacitor electrode application.

Through the interplay of high-resolution scanning tunneling microscopy (STM) imaging/manipulation and density functional theory (DFT) calculations, we have demonstrated that an unprecedented selective aryl-aryl coupling via direct C-H bond activation can be successfully achieved on Cu(110). These findings present a simple and generalized route for preparing low dimensional carbon nanomaterials.