Boosting Hydrogen Evolution at Visible Light Wavelengths by Using a Photocathode with Modal Strong Coupling between Plasmons and a Fabry-Pérot Nanocavity

Hot-hole injection from plasmonic metal nanoparticles to the valence band of p-type semiconductors and reduction by hot electrons should be improved for efficient and tuneable reduction to obtain beneficial chemical compounds. We employed the concept of modal strong coupling between plasmons and a Fabry-Pérot (FP) nanocavity to enhance the hot-hole injection efficiency. We fabricated a photocathode composed of gold nanoparticles (Au−NPs), p-type nickel oxide (NiO), and a platinum film (Pt film) (ANP). The ANP structure absorbs visible light over a broad wavelength range from 500 nm to 850 nm via hybrid modes based on the modal strong coupling between the plasmons of Au−NPs and the FP nanocavity of NiO on a Pt film. All wavelength regions of the hybrid modes of the modal strong coupling system promoted hot-hole injection from the Au−NPs to NiO and proton/water reduction by hot electrons. The incident photon-to-current efficiency based on H₂ evolution through water/proton reduction by hot electrons reached 0.2 % at 650 nm and 0.04 % at 800 nm.     

A Mechanistic Dichotomy in Two-Electron Reduction of Dioxygen Catalyzed by N,N’-Dimethylated Porphyrin Isomers

Selective two-electron reduction of dioxygen (O₂) to hydrogen peroxide (H₂O₂) has been achieved by two saddle-distorted N,N’-dimethylated porphyrin isomers, an N21,N’22-dimethylated porphyrin ( anti -Me₂P ) and an N21,N’23-dimethylated porphyrin ( syn -Me₂P ) as catalysts and ferrocene derivatives as electron donors in the presence of protic acids in acetonitrile. The higher catalytic performance in an oxygen reduction reaction (ORR) was achieved by anti -Me₂P with higher turnover number (TON=250 for 30 min) than that by syn -Me₂P (TON=218 for 60 min). The reactive intermediates in the catalytic ORR were confirmed to be the corresponding isophlorins ( anti -Me₂Iph or syn -Me₂Iph ) by spectroscopic measurements. The rate-determining step in the catalytic ORRs was concluded to be proton-coupled electron-transfer reduction of O₂ with isophlorins based on kinetic analysis. The ORR rate by anti -Me₂Iph was accelerated by external protons, judging from the dependence of the observed initial rates on acid concentrations. In contrast, no acceleration of the ORR rate with syn -Me₂Iph by external protons was observed. The different mechanisms in the O₂ reduction by the two isomers should be derived from that of the arrangement of hydrogen bonding of a O₂ with inner NH protons of the isophlorins.     

Discrete π Stack of a Tweezer-Shaped Naphthalenediimide–Anthracene Conjugate

The design and synthesis of a tweezer-shaped naphthalenediimide (NDI)–anthracene conjugate ( 2NDI ) are reported. In the structure of the closed form (π_NDI ⋅⋅⋅ π_NDI stack) of 2NDI , which was elucidated by single-crystal XRD, the existence of C−H ⋅⋅⋅ O hydrogen bonding involving the nearest carbonyl oxygen atom of an NDI unit was suggested. The tunability of π_NDI ⋅⋅⋅ π_NDI interactions was studied by means of UV/Vis absorption, fluorescence and NMR spectroscopy and molecular modelling. This revealed that the π_NDI ⋅⋅⋅ π_NDI interactions in 2NDI affect the absorption and emission properties depending on the temperature. Furthermore, in polar solvents, 2NDI prefers the stronger π_NDI ⋅⋅⋅ π_NDI stack, whereas the π_NDI ⋅⋅⋅ π_NDI interaction is diminished in nonpolar solvents. Importantly, the conformational variations of 2NDI can be reversibly switched by variation in temperature, and this suggests potential application for fluorogenic molecular switches upon temperature changes.     

Cellulose-synthesizing machinery in bacteria

Cellulose - Cellulose is produced by all plants and a number of other organisms, including bacteria. The most representative cellulose-producing bacterial species is Gluconacetobacter xylinus, an...     

High oxygen-reduction activity of silk-derived activated carbon

Activated carbon prepared from silk fibroin, which is free of metal elements, showed a high catalytic activity for the oxygen-reduction reaction (ORR). The activated carbon had a very high onset potential of E_onset = 0.83 V (vs. RHE) in oxygen-saturated 0.5 M H₂SO₄ at 60 °C. The ORR on the activated carbon proceeded by a four-electron process in the high-electrode-potential region; this gradually decreased to a 3.5-electron reaction below about 0.6 V (vs. RHE). Only about 1% of nitrogen atoms (mostly quaternary) remained in the activated carbon by heat-treatment at up to 1200 °C are responsible for the high catalytic activity. The open circuit voltage of a polymer electrolyte fuel cell using the activated carbon as the cathode and a platinum/carbon black anode under pure oxygen and hydrogen gases, respectively, both at one atmosphere, was 0.96 V at 27 °C.     

Synthetic studies on cell surface glycans 3: Branching pentasaccharides of glycoprotein

Synthetic routes for the branching pentasaccharides 4 and 5 of glycoproteins are described in a regio- and stereo- controlled way.     

Total Synthesis of Proposed Structure of Yuremamine and All Diastereomers Using [3+2]‐Cycloaddition of Platinum‐Containing Azomethine Ylide

Total synthesis of the proposed structure of yuremamine has been achieved for the first time based on the intermolecular [3+2]‐cycloaddition reaction of the platinum‐containing azomethine ylide. All the possible diastereomers of yuremamine were also synthesized via the common intermediate. Through these syntheses, it was confirmed that the proposed structure of yuremamine and the diastereomers differ from the natural product.     

New determination methods of halides and cyanide ions by electrospray ionization mass spectrometry based on ternary complex formation

Determination methods of halide ions (X(-) = F(-), Cl(-), Br(-) and I(-)) by electrospray ionization mass spectrometry (ESIMS) were developed, where negative ions of the ternary complexes of group-13 elements, nitrilotriacetic acid (NTA), and halides were measured. In particular, these halides were simultaneously determined by measuring [InX(nta)](-), and the limits of detection (LODs) were 1.1 μmol dm(-3) for F(-), 0.32 μmol dm(-3) for Cl(-), 3.8 nmol dm(-3) for Br(-), and 1.6 nmol dm(-3) for I(-), respectively. This approach was extended to the determination of CN(-), where the ternary complex of Cu(II), CN(-) and 4-(2-pyridylazo)resorcinol (PAR), i.e., [(63)Cu(II)(CN)(par)](-) (m/z 302) was measured. The LOD for CN(-) was 20 nmol dm(-3).     

Conformational Dynamics of Monomer‐ versus Dimer‐like Features in a Naphthalenediimide‐Based Conjugated Cyclophane

The design and synthesis of an enantiomeric pair of 1,8‐diethynylanthracene‐bridged naphthalenediimide (NDI)‐based cyclophanes ( Cyclo‐NDI s) are reported. Each enantiomer of Cyclo‐NDI exhibits a circularly polarized luminescence signal with a relatively large luminescence dissymmetry factor (g_lum=±8×10^?3). We have further investigated the modulation of through‐space electronic communication between co‐facially oriented NDIs in a discrete Cyclo‐NDI with changes in the temperature. Tuning of the electronic communication results from the conformational transformation of monomer‐ versus dimer‐like features of Cyclo‐NDI , as confirmed by UV/Vis, fluorescence, circular dichroic, and NMR spectroscopic analysis. The temperature‐dependent optical response in the Cyclo‐NDI through the conformational transformation could be utilized as a highly sensitive and reversible optical thermometer in a wide temperature range (100 to ?80 °C).