Size-controlled deposition of Ag nanoparticles on alumina with the assistance of a photo-induced chromic reaction, and study of their catalytic properties

This paper describes a promising method to synthesize supported metal catalysts based on a photochromic reaction. Highly dispersed Ag nanoparticles (NPs) with a mean diameter of ca. 10 nm stabilized by 3-mercaptopropionic acid (3-MPA) were prepared as a colloidal precursor solution. The zeta electric potential was found to be negatively charged in the region of pH higher than 5 due to the presence of dissociated carboxylate ions (-COO(-)), which led to electric repulsion between Ag NPs and kept the solution in a highly dispersed colloidal state. In the presence of photochromic molecules, trans-2-hydroxychalcone, the photo-irradiation gradually decreased the electric charge on the nanoparticles owing to the formation of flavylium cations, which induced the assembly of Ag NPs. Such photo-induced assembly-dispersion control of Ag NPs enables size selective deposition on a catalyst support, which is controlled by varying the photo-irradiation time.     

Reversible Sodium Metal Electrodes: Is Fluorine an Essential Interphasial Component?

Alkaline metals are an ideal negative electrode for rechargeable batteries. Forming a fluorine‐rich interphase by a fluorinated electrolyte is recognized as key to utilizing lithium metal electrodes, and the same strategy is being applied to sodium metal electrodes. However, their reversible plating/stripping reactions have yet to be achieved. Herein, we report a contrary concept of fluorine‐free electrolytes for sodium metal batteries. A sodium tetraphenylborate/monoglyme electrolyte enables reversible sodium plating/stripping at an average Coulombic efficiency of 99.85 % over 300 cycles. Importantly, the interphase is composed mainly of carbon, oxygen, and sodium elements with a negligible presence of fluorine, but it has both high stability and extremely low resistance. This work suggests a new direction for stabilizing sodium metal electrodes via fluorine‐free interphases.     

Extended Fluorochromism of Anthracene Trimers with a meta‐Substituted Triphenylamine or Triphenylphosphine Core

Combining meta‐triphenylamine or triphenylphosphine with three anthracene fluorophores gives rise to fluorescent non‐planar triskelions 1 and 2 . The emissive properties of 1 are highly solvatochromic, yielding blue to pale green and even pale yellow fluorescence, whereas the blue emission of 2 is solvent‐insensitive. Anthracene trimers 1 and 2 are both emissive in the solid state, displaying yellow and pale green fluorescence, respectively, with moderate quantum yields.     

Direct Near Infrared Light–Activatable Phthalocyanine Catalysts

The high penetration of near-infrared (NIR) light makes it effective for use in selective reactions under light-shielded conditions, such as in sealed reactors and deep tissues. Herein, we report the development of phthalocyanine catalysts directly activated by NIR light to transform small organic molecules. The desired photocatalytic properties were achieved in the phthalocyanines by introducing the appropriate peripheral substituents and central metal. These phthalocyanine photocatalysts promote cross-dehydrogenative-coupling (CDC) under irradiation with 810 nm NIR light. The choice of solvent is important, and a mixture of a reaction-accelerating (pyridine) and -decelerating (methanol) solvents was particularly effective. Moreover, we demonstrate photoreactions under visible-light-shielded conditions through the transmission of NIR light. A combined experimental and computational mechanistic analysis revealed that this NIR reaction does not involve a photoredox-type mechanism with electron transfer, but instead a singlet-oxygen-mediated mechanism with energy transfer.     

Changes of electrochemical responses of the bulk solution species by thermotropic permeability of liquid crystalline membranes coated on electrodes

Liquid crystalline/polymer composite membrane-coated electrodes were prepared by casting a 1,2-dichloroethane solution of N-(4-ethoxybenzylidene)-4′-n-butylaniline (EBBA) and polycarbonate (PC) on an electrode surface. The temperature-dependence of the permeability of the EBBA/PC composite membrane on electrodes to Fe(CN)^3?₆ ion as a solution-phase redox ion was investigated by means of hydrodynamic voltammetry at a rotating disk electrode. The permeability changed with temperature over the range of the crystalline-nematic-phase transition temperature of EBBA. It is demonstrated that the observed temperature-dependence of the permeability reflects the thermotropic properties of EBBA in the EBBA/PC composite membrane. Furthermore, the dependence of the limiting current of the steady-state current-potential curves for the reduction of Fe(CN)^—₆ at the EBBA/PC composite membrane-coated electrode upon the membrane thickness, the blend ratio of EBBA and PC and the concentration of Fe(CN)^3?₆ in a bulk solution was examined in order to understand the transport process of Fe(CN)^?3₆ through the EBBA/PC composite membrane from the membrane/solution interface to the electrode/membrane interface. The transport process of Fe(CN)^3?₆ within the membrane was found to obey Fick's Law.