Effect of Micropores of a Porous Coordination Polymer on the Product Selectivity in RuII Complex-catalyzed CO2 Reduction

To develop an efficient CO2 reduction catalyst, hybridizing a molecular catalyst and a porous coordination polymer (PCP) is a promising strategy because it can combine both advantages of the precise reactivity control of the former and the CO2 adsorption property of the latter. Although several PCP hybrid catalysts have been reported to date, the CO2 sorption behavior and the CO2 reduction reactivity have been investigated separately, and the CO2 enrichment during the catalysis is still unclear. We report CO2 photoreduction under different temperatures and pressures using a PCP-RuII complex hybrid catalyst. The product selectivity (CO or HCOOH) varied depending on the reaction conditions. The altered selectivity could be interpreted in terms of the CO2 capture in the micropores of a PCP.     

Development of a voltage-applicable heating specimen holder for in situ observations of solid oxide fuel cells with an environmental transmission electron microscope

A voltage-applicable heating specimen holder is developed to observe solid oxide fuel cells (SOFCs) in an environmental transmission electron microscope. An SOFC specimen can be heated and has a voltage applied in an oxygen gas atmosphere using the holder. Oxygen ion migration and redox reactions in the specimen could also be realized. The heating unit, which consists of nickel–chromium alloy mounted on the tip of the developed specimen holder, can heat the specimen up to 1200 K in an oxygen gas atmosphere. A specimen preparation method for the SOFC structure is also established using a focused ion beam technique. The holder has high stability for high-resolution imaging and electron energy loss spectroscopy under the in situ condition. The mechanical and electrical stabilities are estimated from high-resolution images and electron energy loss spectra of the heated and voltage-applied specimen in an oxygen gas atmosphere. The developed holder is a powerful tool to reveal the microstructural and electronic structural changes that occur by electrochemical reactions at the interfaces of an SOFC.     

A Technical Critique of Some Parts of the Free Energy Principle

We summarize the original formulation of the free energy principle and highlight some technical issues. We discuss how these issues affect related results involving generalised coordinates and, where appropriate, mention consequences for and reveal, up to now unacknowledged, differences from newer formulations of the free energy principle. In particular, we reveal that various definitions of the “Markov blanket” proposed in different works are not equivalent. We show that crucial steps in the free energy argument, which involve rewriting the equations of motion of systems with Markov blankets, are not generally correct without additional (previously unstated) assumptions. We prove by counterexamples that the original free energy lemma, when taken at face value, is wrong. We show further that this free energy lemma, when it does hold, implies the equality of variational density and ergodic conditional density. The interpretation in terms of Bayesian inference hinges on this point, and we hence conclude that it is not sufficiently justified. Additionally, we highlight that the variational densities presented in newer formulations of the free energy principle and lemma are parametrised by different variables than in older works, leading to a substantially different interpretation of the theory. Note that we only highlight some specific problems in the discussed publications. These problems do not rule out conclusively that the general ideas behind the free energy principle are worth pursuing.     

Photocatalytic Activity of Radial Rutile Titanium(IV) Oxide Microspheres for Aerobic Oxidation of Organics

Radial rutile TiO₂ nanorod homomesocrystals (TiO₂-NR HOMCs) or the so-called “sea urchin-like TiO₂ microspheres” were synthesized by using a hydrothermal method. TiO₂-NR HOMCs show photocatalytic activity for aerobic oxidative degradation of 2-naphthol under irradiation of UV- and visible light. Furthermore, extremely small iron oxide clusters were formed on the surface of TiO₂-NR HOMCs (FeO_x/TiO₂-NR HOMCs) by the chemisorption-calcination technique to reduce the band gap. The FeO_x-surface modification gives rise to drastic enhancement of the UV- and visible-light activity. Reversed double-beam photoacoustic spectroscopy measurements were performed for TiO₂-NR HOMCs and FeO_x/TiO₂-NR HOMCs to obtain the ERDT (energy-resolved distribution of electron traps)/CBB (conduction-band bottom) patterns. The ERDT/CBB pattern of TiO₂-NR HOMCs consists of two components derived from rutile (C1) and amorphous TiO₂ (C2). In the pattern, the surface electron traps in C2 exist near the CBB to be removed by the FeO_x-surface modification. By taking this finding into consideration, the striking surface modification effect is ascribable to the electrocatalytic activity (or the action as an electron reservoir) of the FeO_x clusters for multiple ORR, the suppression of recombination, and the increase in the visible-light harvesting efficiency.     

Effects of orientation and degree of polymerization on tensile properties in the cellulose sheets using hierarchical structure of wood

Cellulose - Structural control is essential for further development of cellulosic materials. Here, we demonstrated the significance of the orientation and degree of polymerization in the integrated...     

All-atom molecular simulation study of cellulose acetate: amorphous structure and the dissolution of small molecule

All-atom analysis was conducted for cellulose acetate (CA) using molecular dynamics simulation. The intermolecular interactions were elucidated at the amorphous state with degrees of acetyl substitution (DS) of 2, 2.5, and 3, and the energetics of dissolution was treated for H₂O, CO₂, and CH₄. It was observed for the CA amorphous that DS strongly affects the hydrogen bonding among the hydroxy groups of CA and that the short-range packing of pyranose rings becomes tighter with acetylation. The free energy of dissolution was computed by the energy-representation method of solvation. The dissolution into CA was more favorable in the order of H₂O?>?CO₂?>?CH₄, and the DS dependence of the dissolution free energy was evident only for H₂O between DS?=?2 and 2.5. The roles of the intermolecular interaction components were further addressed. It was seen that the electrostatic component brings the DS dependence of the dissolution free energy for H₂O as well as the difference in the affinity to CA between CO₂ and CH₄. The van der Waals component was still dominant for the nonpolar CO₂ and CH₄, and the summed contribution to it from the acetyl and main-chain groups of CA was weakly dependent on DS. The connection of the dissolution energetics with the underlying structures is also discussed.

Graphical abstract

     

Unzipping and scrambling reaction-induced sequence control of copolymer chains via temperature changes during cationic ring-opening copolymerization of cyclic acetals and cyclic esters

A temperature change-dependent sequence transformation of copolymer chains was demonstrated by a method based on tandem depolymerization and transacetalization reactions during the cationic ring-opening copolymerization of cyclic acetals and cyclic esters. In this study, the position of polymerization-depolymerization equilibrium was controlled by the reaction temperature rather than by the decrease in monomer concentration under vacuum conditions, as in our previous study. First, the conditions for efficient copolymerization were optimized, with a particular focus on the structures of cyclic acetals and cyclic esters. Subsequently, sequence transformation induced by temperature change was examined during the copolymerization of 2-methyl-1,3-dioxepane (generated in situ from 4-hydroxybutyl vinyl ether) and δ-valerolactone using EtSO₃H. The homosequence length of cyclic acetals decreased during depolymerization (unzipping) at the oxonium chain ends upon increasing the temperature from 30 to 90 °C, while transacetalization (scrambling) of the main chain transferred midchain cyclic acetal homosequences to the oxonium chain ends. As a result of the cycle of unzipping and scrambling reactions, an alternating-like copolymer was obtained. Interestingly, the possibility of reversible sequence transformation upon heating and cooling was also demonstrated.     

A single-molecule enzymatic assay in a directly accessible femtoliter droplet array

The enzyme assay in a femtoliter chamber array is a simple and efficient method for concentrating the reaction product; it greatly improves the detection sensitivity down to the single-molecule level. However, in previous methods, controlling the initiation and termination of the reaction in each chamber is difficult once enclosed. Furthermore, the recovery of the enzyme and product is also difficult. To overcome these drawbacks, we developed a femtoliter droplet array in which the individual droplets are fixed on the substrate and are directly accessible from outside. A hydrophilic-in-hydrophobic micropatterned surface was used for the preparation of the droplets. When the aqueous solution on the surface is exchanged with oil, the hydrophilic surface retains the aqueous solution, and more than 10(6) dome-shaped droplets that are usable for further assay can be prepared simultaneously. The curvature radius of the droplet obeys the Young-Laplace equation, and the volume can be precisely controlled by the micropipette, which applies pressure into the droplet. Changing the pressure makes the addition, collection, and exchange of the aqueous content for individual droplets possible. Using these advantages, we successfully measured the kinetic parameters of the single-molecule enzyme β-galactosidase and rotary motor protein F(1)-ATPase enclosed in a droplet.     

A Monomer‐Micelle Model for the Formation of Simple Taurocholate Micelles

A kinetic dialysis technique was used to validate a relationship between monomer taurocholate (TC) concentration and total TC concentration in TC solutions containing 0.15 M NaCl and 0.01 M buffer (pH = 7.4). Based on the experimental data and Mukerjee's equations, the number average degree and the weight average degree of TC aggregates were estimated to be nearly the same (～5), indicating that simple TC micelles were the only aggregates. Furthermore, the TC dimer concentration was quantified to be negligible. According to the validated relationship, aggregation number of 5 for simple TC micelles, and the definition of critical micelle concentration (CMC), a modified monomer‐micelle model was used for describing simple TC micelle formation. Moreover, the CMC value was estimated to be ～6.3 mM, which is consistent with the reported value of ～6.0 mM.