Catalytic four-electron oxidation of water by intramolecular coupling of the oxo ligands of a bis(ruthenium-bipyridine) complex

A bis(ruthenium-bipyridine) complex bridged by 1,8-bis(2,2':6',2'-terpyrid-4'-yl)anthracene (btpyan), [Ru(2)(μ-Cl)(bpy)(2)(btpyan)](BF(4))(3) ([1](BF(4))(3); bpy = 2,2'-bipyridine), was prepared. The cyclic voltammogram of [1](BF(4))(3) in water at pH?1.0 displayed two reversible [Ru(II),Ru(II)](3+)/[Ru(II),Ru(III)](4+) and [Ru(II),Ru(III)](4+)/[Ru(III),Ru(III)](5+) redox couples at E(1/2)(1) = +0.61 and E(1/2)(2) = +0.80?V (vs. Ag/AgCl), respectively, and an irreversible anodic peak at around E = +1.2?V followed by a strong anodic currents as a result of the oxidation of water. The controlled potential electrolysis of [1](3+) ions at E = +1.60?V in water at pH?2.6 (buffered with H(3)PO(4)/NaH(2)PO(4)) catalytically evolved dioxygen. Immediately after the electrolysis of the [1](3+) ion in H(2)(16)O at E = +1.40?V, the resultant solution displayed two resonance Raman bands at nu = 442 and 824?cm(-1). These bands shifted to nu = 426 and 780?cm(-1), respectively, when the same electrolysis was conducted in H(2)(18)O. The chemical oxidation of the [1](3+) ion by using a Ce(IV) species in H(2)(16)O and H(2)(18)O also exhibited the same resonance Raman spectra. The observed isotope frequency shifts (Δnu = 16 and 44?cm(-1)) fully fit the calculated ones based on the Ru-O and O-O stretching modes, respectively. The first successful identification of the metal-O-O-metal stretching band in the oxidation of water indicates that the oxygen-oxygen bond at the stage prior to the evolution of O(2) is formed through the intramolecular coupling of two Ru-oxo groups derived from the [1](3+) ion.     

Direct observation of optical excitation transfer based on resonant optical near-field interaction

This article reports the direct observation of long-distance optical excitation transfer based on resonant optical near-field interactions in randomly distributed quantum dots (QDs). We fabricated optical excitation transfer paths based on randomly distributed QDs by using CdSe/ZnS core?Cshell QDs and succeeded for the first time in obtaining output signals resulting from a unidirectional optical excitation transfer length of 2.4???m. Furthermore, we demonstrate that the optical excitation transfer occurs via the resonant excited levels of the QDs with a comparative experiment using non-resonant QDs. This excitation-transfer mechanism allows for intersecting, non-interacting nano-optical wires.     

Si homojunction structured near-infrared laser based on a phonon-assisted process

We fabricated several near-infrared Si laser devices (wavelength ～1300 nm) showing continuous-wave oscillation at room temperature by using a phonon-assisted process induced by dressed photons. Their optical resonators were formed of ridge waveguides with a width of 10 μm and a thickness of 2 μm, with two cleaved facets, and the resonator lengths were 250–1000 μm. The oscillation threshold currents of these Si lasers were 50–60 mA. From near-field and far-field images of the optical radiation pattern, we observed the high directivity which is characteristic of a laser beam. Typical values of the threshold current density for laser oscillation, the ratio of powers in the TE polarization and TM polarization during oscillation, the optical output power at a current of 60 mA, and the external differential quantum efficiency were 1.1–2.0 kA/cm², 8:1, 50 μW, and 1 %, respectively.     

Electroless Nickel Plating under Continuous Ultrasonic Irradiation to Fabricate a Near-Field Probe Whose Metal Coat Decreases in Thickness toward the Tip

This paper describes a size-dependent electroless plating method to fabricate a new type of probe with a locally decreasing thickness of metal and a tiny tip size for a combined high resolution shear-force and near-field optical microscope. In this method, the tip size and decreasing thickness profile, which affect the resolution capabilities of the microscopes, are controlled by adding a continuous ultrasonic wave with a frequency of 1 MHz to a nickel plating bath. The probe with a tip radius of curvature of 25 nm was successfully fabricated at an ultrasonic power density of 1.6 W cm⁻², its metal thickness gradually decreased from 850 to 20 nm toward the distal tip.     

Amyloid‐like Nanofibrillation of Metal‐Organic Complex Arrays Ruled by Their Precisely Designed Metal Sequences

Self‐assembly of a series of dimetallic sequences constructed on a backbone with two successive tyrosine moieties ( Fmoc‐M ¹ ‐M ² ‐CO₂H ) revealed that the resultant morphology is clearly dependent on the metal sequence, where Re‐containing sequences such as homometallic Fmoc‐Re‐Re‐CO₂H specifically afforded amyloid‐like nanofibers. These findings further allowed to achieve the fibrillation of a longer metal sequence containing three different metals ( Fmoc‐Rh‐Pt‐Re‐Re‐CO₂H ). Cyclic voltammetry of the fibrillated Fmoc‐Re‐Re‐CO₂H demonstrated that the redox activity of the metal complexes in the sequence is preserved in the nanofibrous forms.     

Evaluating the Quantum Confinement Effect of Isolated ZnO Nanorod Single-Quantum-Well Structures Using Near-Field Ultraviolet Photoluminescence Spectroscopy

Using low-temperature near-field spectroscopy, we obtained spatially and spectrally resolved photoluminescence (PL) images of individual ZnO nanorod single-quantum-well structures (SQWs) with a spatial resolution of 20 nm. We observed the dependence of the quantum confinement effect of the PL peak on the well width (L _aw), from which the linewidths of near-field PL spectra of ZnO nanorod SQWs (L _aw = 2.5 and 3.75 nm) were determined to be as narrow as 3 meV. However, near-field PL spectra of individual SQWs with L _aw = 5.0 nm exhibited two PL peaks, presumably due to strains or defects in the ZnMgO in the nanorod SQWs. Since the exciton in a quantum structure is an ideal two-level system with long coherence times, our results provide criteria for designing nanophotonic devices.     

Near-field optical chemical vapor deposition using Zn(acac)2 with a non-adiabatic photochemical process

We succeeded in depositing nanometric Zn dots using near-field optical chemical vapor deposition (NFO-CVD). Conventional optical CVD is based on an adiabatic photochemical process and requires UV light to excite molecules from the ground electronic state to the excited state for dissociation. By contrast, in near-field optical CVD (NFO-CVD), non-adiabatic photodissociation takes place, even with visible light, as a consequence of the steep spatial gradient of the optical power of an optical near field. This non-adiabatic process, which can be explained using the exciton–phonon polariton model, enables the photodissociation of optically inactive Zn(acac)₂. We discuss experimental results using the exciton–phonon polariton model. PACS 33.80.Gj; 82.50.-m; 81.16.Be     

Multivariable RBF-ARX model-based robust MPC approach and application to thermal power plant

For a class of smooth nonlinear multivariable systems whose working-points vary with time and the future working-points knowledge are unknown, a combination of a local linearization and a polytopic uncertain linear parameter-varying (LPV) state-space model is built to approximate the present and the future system’s nonlinear behavior, respectively. The combination models are constructed on the basis of a matrix polynomial multi-input multi-output (MIMO) RBF-ARX model identified offline for representing the underlying nonlinear system. A min–max robust MPC strategy is designed to achieve the systems’ output-tracking control based on the approximate models proposed. The closed loop stability of the MPC algorithm is guaranteed by the use of time-varying parameter-dependent Lyapunov function and the feasibility of the linear matrix inequalities (LMIs). The effectiveness of the modeling and control methods proposed in this paper is illustrated by a case study of a thermal power plant simulator.     

Highly efficient and broadband Si homojunction structured near-infrared light emitting diodes based on the phonon-assisted optical near-field process

We fabricated a highly efficient, broadband light emitting diode driven by an optical near field generated at the inhomogeneous domain boundary of a dopant in a homojunction bulk Si crystal and evaluated its performance. To fabricate this device, a forward current was made to flow through a Si p–n junction to anneal it. During this process, the device was irradiated with near-infrared light, producing stimulated-emission light using a two-step phonon-assisted process triggered by the optical near field, and the annealing rate was controlled in a self-organized manner. The device emitted light in a wide photon energy region of 0.73–1.24 eV (wavelength 1.00–1.70 μm). The total power of the emitted light with 11 W of electrical input power was as high as 1.1 W. The external power conversion efficiency of the emitted light was 1.3%, the differential external power conversion efficiency was 5.0%, the external quantum efficiency was 15%, and the differential external quantum efficiency was 40%. The dependency of the emitted light power density on the injected current density clearly showed a characteristic reflecting the two-step phonon-assisted transition process.