Using ultraviolet photoelectron spectroscopy, we provide direct experimental evidence that di-oxygen species are stable on anionic gold dimer and tetramer clusters at room temperature. The stabilization of molecular oxygen is crucial for the high activities of the low-temperature reactions on gold catalysts.

Plasmonic structures can provide deep-subwavelength electromagnetic fields that are useful for enhancing light–matter interactions. However, because these localized modes are also dissipative, structures that offer the best compromise between field confinement and loss have been sought. Metallic wedge waveguides were initially identified as an ideal candidate but have been largely abandoned because to date their experimental performance has been limited. We combine state-of-the-art metallic wedges with integrated reflectors and precisely placed colloidal quantum dots (down to the single-emitter level) and demonstrate quantum-plasmonic waveguides and resonators with performance approaching theoretical limits. By exploiting a nearly 10-fold improvement in wedge-plasmon propagation (19 μm at a vacuum wavelength, λvac, of 630 nm), efficient reflectors (93%), and effective coupling (estimated to be >70%) to highly emissive (∼90%) quantum dots, we obtain Ag plasmonic resonators at visible wavelengths with quality factors approaching 200 (3.3 nm line widths). As our structures offer modal volumes down to ∼0.004λvac3 in an exposed single-mode waveguide–resonator geometry, they provide advantages over both traditional photonic microcavities and localized-plasmonic resonators for enhancing light–matter interactions. Our results confirm the promise of wedges for creating plasmonic devices and for studying coherent quantum-plasmonic effects such as long-distance plasmon-mediated entanglement and strong plasmon–matter coupling.

Experimental evidences for the non-dissociative chemisorption of O 2 are presented on even-numbered free Au anion clusters (Au À n , n ¼ number of atoms) up to Au À 20 at room temperature. Our result indicates that the formation of the activated di-oxygen species is the key of the unusual catalytic activities of Au-based catalysts. No correlation between geometrical structures of Au À n and the activities towards O 2 adsorption was found, showing that site-specific chemistry disappears for Au-nanocatalysis. We demonstrate that interplay between cluster physics and surface chemistry is a promising strategy to unveil mechanisms of elementary steps in nanocatalysis.

Experimental and theoretical evidence is presented for the nondissociative chemisorption of O2 on free Au cluster anions (Aun-, n=number of atoms) with n=2, 4, 6 at room temperature, indicating that the stabilization of the activated di-oxygen species is the key for the unusual catalytic activities of Au-based catalysts. In contrast to Aun- with n=2, 4, 6, O2 adsorbs atomically on Au monomer anions. For the Au monomer neutral, calculations based on density functional theory reveal that oxygen should be molecularly bound. On Au dimer and tetramer neutrals, oxygen is molecularly bound with the O-O bond being less activated with respect to their anionic counterparts, suggesting that the excess electron in the anionic state plays a crucial role for the O-O activation. We demonstrate that interplay between experiments on gas phase clusters and theoretical approach can be a promising strategy to unveil mechanisms of elementary steps in nanocatalysis.

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To get access to the intrinsic properties of organic semiconductors, investigations on single crystals are essential. The authors report on far- and mid-infrared spectroscopies of the charge accumulation layer in an organic field-effect transistor fabricated on a rubrene single crystal. By charge modulation spectroscopy in the range between 70 and 4750cm−1, they were able to detect the Drude response of the accumulated charges in the channel. From this they can extract important intrinsic transport parameters such as the mobility, the plasma frequency, the effective mass, and the scattering rate.

enhancement of polymer-side-chain mobility at room temperature, and the saturation dose is largely dependent on film thickness. We also show that polymer rewriteability is directly correlated to the degree of photobleaching that occurs during writing. The very large birefringence and high optical transparency in the 650±1600 nm wavelength range is quite promising for integrated photonic device applications of photoaddressable polymer thin films. ExperimentalSample Preparation: Amorphous isotropic polymer films with thicknesses ranging from 160±780 nm were prepared by spinning PAP solutions in tetrahydrofuran on glass substrates. The sample thickness was determined with an Alpha-Step surface profiler, while the refractive index was measured with a spectroscopic ellipsometer.Optical Characterization: Film birefringence was quantified in situ using a standard experimental setup [7] where the reading source (633 nm HeNe or 670 nm diode) was polarized 45 with respect to the write source (488 nm line of the Ar + beam). Both beams are directed onto the sample surface in normal incidence (write diameter 1.4 mm, read diameter~0.5 mm), and subsequently pass through polarized beam splitters. The write beam and the perpendicular-polarized component of the read beam are then directed to germanium photodetectors to obtain intensity data for the calculation of photobleaching and birefringence, respectively.

We explored the isomerization of d-glucose into d-fructose using the simplest possible base catalyst, aqueous NaOH, to maintain a constant pH value during the reaction. Under the applied mild conditions (T 50–90 °C, pH 9.5–11.5), yields of d-fructose of up to 31% were observed. Selectivity-conversion plots were not significantly influenced by variation of the temperature, pH value or substrate concentration. A reaction network for kinetic modelling includes d-glucose-d-fructose interconversion, co-production of d-mannose and d-allulose (also known as d-psicose) as well as decomposition paths after deprotonation of the hexoses. All four hexoses were employed as substrates in the isomerization. Thermodynamic ionization constants of the saccharides were measured by means of potentiometric titration. In the kinetic studies, pH-independent rate constants as well as activation energies were determined. The obtained kinetic and thermodynamic results as well as selectivity-conversion correlations present a useful benchmark for soluble and solid base catalysts.