Remote Control of Electron Transfer Reaction by Microwave Irradiation: Kinetic Demonstration of Reduction of Bipyridine Derivatives on Surface of Nickel Particle.

Microwave irradiation has great potential to control chemical reactions remotely, particularly reactions that involve electron transfer. In this study, we found that the reduction reaction of bipyridine derivatives on metal nickel particles was accelerated or decelerated by 2.45 GHz microwaves without an alteration of the reaction temperature.

Enhancement of Fixed-bed Flow Reactions under Microwave Irradiation by Local Heating at the Vicinal Contact Points of Catalyst Particles.

The formation of local high temperature regions, or so-called "hot spots", in heterogeneous reaction systems has been suggested as a critical factor in the enhancement of chemical reactions using microwave heating. In this paper, we report the generation of local high temperature regions between catalyst particles under microwave heating. First, we demonstrated that reaction rate of the dehydrogenation of 2-propanol over a magnetite catalyst was enhanced 17- (250 °C) to 38- (200 °C) fold when heated with microwave irradiation rather than an electrical furnace.

Construction of Highly Hierarchical Layered Structure Consisting of Titanate Nanosheets, Tungstate Nanosheets, Ru(bpy), and Pt(terpy) for Vectorial Photoinduced Z-Scheme Electron Transfer.

To imitate the precisely ordered structure of the photoantennas and electron mediators in the natural photosynthesis system, we have constructed the Ru(bpy)-intercalated alternate-layered structure of titanate nanosheets and tungstate nanosheets via thiol-ene click reaction. Before nanosheet stacking, Pt(terpy) was immobilized at the edge of the titanate nanosheets. The visible-light-induced vectorial Z-scheme electron transfer reaction from the valence band of tungstate to the conduction band of titanate via the photoexcited Ru(bpy) was demonstrated by the following two evidences: (1) From the results of the fluorescence decay of Ru(bpy), the rate of the forward electron transfer from the photoexcited Ru(bpy) to the conduction band of titanate was estimated as 1.

Hysteresis-free perovskite solar cells made of potassium-doped organometal halide perovskite.

Potassium-doped organometal halide perovskite solar cells (PSCs) of more than 20% power conversion efficiency (PCE) without I-V hysteresis were constructed. The crystal lattice of the organometal halide perovskite was expanded with increasing of the potassium ratio, where both absorption and photoluminescence spectra shifted to the longer wavelength, suggesting that the optical band gap decreased. In the case of the perovskite with the 5% K, the conduction band minimum (CBM) became similar to the CBM level of the TiO-Li.

Smelting Magnesium Metal using a Microwave Pidgeon Method.

Magnesium (Mg) is a lightweight metal with applications in transportation and sustainable battery technologies, but its current production through ore reduction using the conventional Pidgeon process emits large amounts of CO and particulate matter (PM2.5). In this work, a novel Pidgeon process driven by microwaves has been developed to produce Mg metal with less energy consumption and no direct CO emission.

Microwave Effects on Co-Pi Cocatalysts Deposited on α-FeO for Application to Photocatalytic Oxygen Evolution.

We analyze the effects of microwave applied in the process of photoelectrochemical deposition of cobalt-based cocatalysts, Co-Pi, onto well-orientated flat α-FeO thin films, which were fabricated by pulsed laser deposition. As compared with conventional heating, microwave significantly affects the morphology, chemical composition, and photocatalytic activity of Co-Pi/α-FeO composite. A significant enhancement in photocurrent related to photocatalytic water oxidation is achieved by the Co-Pi catalyst prepared under microwave irradiation.

Enhancement of anodic current attributed to oxygen evolution on α-FeO electrode by microwave oscillating electric field.

Various microwave effects on chemical reactions have been observed, reported and compared to those carried out under conventional heating. These effects are classified into thermal effects, which arise from the temperature rise caused by microwaves, and non-thermal effects, which are attributed to interactions between substances and the oscillating electromagnetic fields of microwaves. However, there have been no direct or intrinsic demonstrations of the non-thermal effects based on physical insights.

In situ temperature measurements of reaction spaces under microwave irradiation using photoluminescent probes.

We demonstrate two novel methods for the measurement of the temperatures of reaction spaces locally heated by microwaves, which have been applied here to two example systems, i.e., BaTiO3 particles covered with a SiO2 shell (BaTiO3-SiO2) and layered tungstate particles.

Rapid Synthesis of D-A'-π-A Dyes through a One-Pot Three-Component Suzuki-Miyaura Coupling and an Evaluation of their Photovoltaic Properties for Use in Dye-Sensitized Solar Cells.

Twenty-four D-A'-π-A dyes were rapidly synthesized through a one-pot three-component Suzuki-Miyaura coupling reaction, which was assisted by microwave irradiation. We measured the absorption spectra, electrochemical properties, and solar-cell performance of all the synthesized dyes. The D5 πA4 dye contained our originally designed rigid and nonplanar donor and exerted the highest efficiency at 5.

Microwave-enhanced photocatalysis on CdS quantum dots--Evidence of acceleration of photoinduced electron transfer.

The rate of electron transfer is critical in determining the efficiency of photoenergy conversion systems and is controlled by changing the relative energy gap of components, their geometries, or surroundings. However, the rate of electron transfer has not been controlled by the remote input of an external field without changing the geometries or materials of the systems. We demonstrate here that an applied microwave field can enhance the photocatalytic reduction of bipyridinium ion using CdS quantum dots (QDs) by accelerating electron transfer.

Rapid Synthesis of Thiophene-Based, Organic Dyes for Dye-Sensitized Solar Cells (DSSCs) by a One-Pot, Four-Component Coupling Approach.

This one-pot, four-component coupling approach (Suzuki-Miyaura coupling/C-H direct arylation/Knoevenagel condensation) was developed for the rapid synthesis of thiophene-based organic dyes for dye-sensitized solar cells (DSSCs). Seven thiophene-based, organic dyes of various donor structures with/without the use of a 3,4-ethylenedioxythiophene (EDOT) moiety were successfully synthesized in good yields based on a readily available thiophene boronic acid pinacol ester scaffold (one-pot, 3-step, 35-61%). Evaluation of the photovoltaic properties of the solar cells that were prepared using the synthesized dyes revealed that the introduction of an EDOT structure beside a cyanoacrylic acid moiety improved the short-circuit current (Jsc) while decreasing the fill factor (FF).

Elucidating the structure-property relationships of donor-π-acceptor dyes for dye-sensitized solar cells (DSSCs) through rapid library synthesis by a one-pot procedure.

The creation of organic dyes with excellent high power conversion efficiency (PCE) is important for the further improvement of dye-sensitized solar cells. We wish to describe the rapid synthesis of a 112-membered donor-π-acceptor dye library by a one-pot procedure, evaluation of PCEs, and elucidation of structure-property relationships. No obvious correlations between ε, and the η were observed, whereas the HOMO and LUMO levels of the dyes were critical for η.

Visible-light-induced electron transfer between alternating stacked layers of tungstate and titanate mediated by excitation of intercalated dye molecules.

Visible-light-induced electron transfer from a tungstate to a titanate layer was demonstrated to be mediated by excited rhodamine B (RhB) intercalated by ion exchange between the two layers. The distance of only 1 nm between the layers provides a large contact area that enables the efficient mediation of electron transfer by RhB.

Collaborational effect of heterolytic layered configuration for enhancement of microwave heating.

Microwave irradiation efficiently heats up the microwave-inert materials in the range of applied frequencies when two microwave-inert materials are brought into contact in the layered configuration. This heating is applied for annealing TiO2 nanoporous films for dye-sensitized solar cells achieving a one order of magnitude more rapid annealing process for comparable performances.

Facile synthesis of bimetallic Cu-Ag nanoparticles under microwave irradiation and their oxidation resistance.

Air-stable bimetallic Cu-Ag nanoparticles in the range of 12-30 nm have been synthesized at gram scale by a facile alcohol reduction in the absence of surfactants with the assistance of microwave irradiation. The synthesized nanoparticles were analyzed by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning TEM, ultraviolet-visible spectroscopy, x-ray photoelectron spectroscopy and thermogravimetry (TG). The stability of the bimetallic nanoparticles against oxidation was examined by TG and in situ temperature-programmed XRD analyses in the atmosphere.

Sequential coupling approach to the synthesis of nickel(II) complexes with N-aryl-2-amino phenolates.

A sequential multicomponent coupling approach is a powerful method for the construction of combinatorial libraries because structurally complex and diverse molecules can be synthesized from simple materials in short steps. In this paper, an efficient synthesis of nickel(II) complexes with N-aryl-2-amino phenols via a sequential three-step coupling approach is described, for potential use in nonlinear optical materials, bioinspired catalytic systems, and near-infrared absorbing filters. Seventeen N-aryl-2-amino phenolates were successfully synthesized in high yields based on the coupling of 3,5-di-tert-butylbenzene-1,2-diol with a pivotal aromatic scaffold, 4-bromo-2-iodo-aniline, followed by sequential Suzuki-Miyaura coupling with aryl boronates.

Issues and challenges in vapor-deposited top metal contacts for molecule-based electronic devices.

Metal vapor deposition to form ohmic contacts is commonly used in the fabrication of organic electronic devices because of significant manufacturability advantages. In the case of single molecular layer devices, however, the extremely small thickness, typically ~1-2nm, presents serious challenges in achieving good contacts and device integrity. This review focuses on recent scientific aspects of metal vapor deposition on monolayer thickness molecular films, particularly self-assembled monolayers, ranging across mechanisms of metal nucleation, metal-molecular group interactions and chemical reactions, diffusion of metal atoms within and through organic films, and the correlations of these and other factors with device function.

Crossed-nanowire molecular junctions: a new multispectroscopy platform for conduction--structure correlations.

We report a crossed-nanowire molecular junction array platform that enables direct measurement of current-voltage-temperature characteristics simultaneously with inelastic electron tunneling and Raman vibrational spectra on the same junction. Measurements on dithiol-terminated oligo(phenylene-ethynylene) junctions show both spectroscopies interrogate the gap-confined molecules to reveal distinct molecular features. This versatile platform allows investigation of advanced phenomena such as molecular switching and cooperative effects with the flexible ability to scale both the junction geometries and array sizes.

Moth olfactory trichoid sensilla exhibit nanoscale-level heterogeneity in surface lipid properties.

Chemical force microscopy (CFM) based on tapping mode Atomic force microscopy (AFM) utilized with topographic and phase-shift analyses was used to investigate the topography and surface chemical properties, respectively, of the long trichoid sensilla on the antennae of male Helicoverpa zea. AFM topographic imaging revealed regular series of step-ridges along nearly the entire length of each sensillum, except for the basal ca. 1/3 portions, which were devoid of such ridges.

Nascent metal atom condensation in self-assembled monolayer matrices: coverage-driven morphology transitions from buried adlayers to electrically active metal atom nanofilaments to overlayer clusters during aluminum atom deposition on alkanethiolate/gold monolayers.

Al atom deposition with controlled coverages has been carried out on self-assembled monolayers (SAMs), prepared by assembly of HS(CH(2))(15)X, with X = -CH(3) (M-SAM) and -CO(2)CH(3) (ME-SAM), on Au {111} substrates, and the resulting structures and electrical properties analyzed in situ by ultrahigh-vacuum, multiple mode atomic force microscopy (contact, noncontact, and conducting probe) and infrared reflection spectroscopy. The M-SAM data clearly reveal a distinct morphology transition at approximately 3 Al atoms per adsorbate molecule (3 EL) from formation of a buried approximately 1:1 Al-Au adlayer at low coverages to metal overlayer cluster nucleation and the appearance of isolated metal nanofilaments with varied behaviors including Ohmic conduction, resistive switching (memristor), and vestiges of quantum-like conductance steps. The ME-SAM data confirm our earlier report of a highly efficient, 1:1 chemical trapping of initial nascent Al atoms by the terminal ester group while also revealing formation of isolated, conducting filaments, mainly at SAM defects, and the presence of an insulating overlayer up to approximately 5 EL.

Study of SERS chemical enhancement factors using buffer layer assisted growth of metal nanoparticles on self-assembled monolayers.

Highly controlled morphology Au nanoparticle films can be formed on the surfaces of self-assembled monolayers (SAMs) by vapor deposition at cryogenic temperatures (approximately 10 K) with intervening condensed Xe layers on the SAMs serving as a buffer to reduce the kinetic energy of the Au atoms impinging on the surface (buffer layer assisted growth or BLAG). Under these conditions pristine Au nanoparticles (AuNp) of a uniform shape and size were deposited onto two SAMs differing only by their terminal groups, 4-benzenedithiol (BDT) and 4-methylbenzenethiol (MBT), to form -S/Au and -CH(3)/Au interfaces with essentially identical AuNp overlayer morphologies. A surface enhanced Raman (SERS) enhancement factor ratio EF(BDT)/EF(MBT) of approximately 130 was observed uniformly across the surfaces (approximately <10% variation).