C2 production with conventional metal complex catalysts
has been a significant challenge. Here, we present the electrochemical
reduction of CO2 into C2 products such as ethylene
and ethanol with high selectivity using a self-assembled cuprous coordination
polymer nanoparticle (Cu-SCP). The features
of the Cu-SCP catalyst are the arrangement of Cu atoms in close proximity,
similar to that in metallic Cu, and a stable Cu(I) oxidation state
throughout the reaction due to the coordination of ligands with Cu
atoms, which inhibits conversion into Cu metal particles. The Cu-SCP
also exhibits activity for C2 production that is superior
to that of a Cu metal electrode, without modification of the carbon
particles and/or ionomers or continuous flow of the highly alkaline
electrolyte, which will simplify the fabrication of a CO2 electrolyzer. The Cu-SCP can be synthesized by a facile process
that utilizes a heterogeneous reaction, and the product selectivity
can be changed by replacement of the organic ligands, which should
open up possibilities for the design of other CO2 reduction
catalysts.
Kinetics and thermodynamics of triplex formation between 9-mer homopyrimidine PNA (HN-Lys-TCTCCTCCC-CONH) and double-stranded RNA (dsRNA, 5'-AGAGGAGGG-3'/3'-UCUCCUCCC-5') at acidic pH were studied by means of a stopped-flow technique and isothermal titration calorimetry (ITC). These results revealed the following main findings: (i) the stable PNA-dsRNA triplex formation mostly originated from the large association rate constant (k), which was dominated by both the charge neutral PNA backbone and the protonation level of the PNA cytosine. (ii) The temperature dependence of the enthalpy change (ΔH) and k suggested that the association phase of the PNA-dsRNA triplex formation comprised a non-directional nucleation-zipping mechanism that was coupled with the conformational transition of the unbound PNA. (iii) The destabilization by a mismatch in the dsRNA sequence mainly resulted from the decreased magnitude of both k and ΔH. (iv) There was sequence and position dependence of the mismatch on ΔH and the activation energy (E), which illustrated the importance of base pairing in the middle of the sequence. Our results for the first time revealed an association mechanism for the PNA-dsRNA triplex formation. A set of the kinetic and thermodynamic data we reported here will also expand the scope of understanding for nucleic acid recognition by PNA.
Core–dual‐shell‐type hybridized nanoparticles (NPs) having Au‐core/dye‐doped silica inner shell/Au outer shell are successfully fabricated by developing a biphasic process that is a kind of so‐called “one‐pot” method. The resulting hybridized NPs exhibit evidently about 20‐fold enhancement of fluorescence intensity, increase in fluorescence quantum yield, and decrease in fluorescence lifetime. These effects depend on the metal nanostructure being optimized, compared with the reference hybridized NPs with neither a Au‐core nor a Au outer shell, due to the gap‐mode effect induced by localized surface plasmon resonance in the core–dual‐shell‐type MIM‐like nanostructure. More detailed elucidation concerning the enhancement mechanism will provide the possibility of photonic device application, for example as a high‐performance point light source, nanolaser, or sensor for bioimaging in the visible region in the near future.
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