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Converting CO₂to value‐added chemicals,e. g., CH₃OH, is highly desirable in terms of the carbon cycling while reducing CO₂emission from fossil fuel combustion. Cu‐based nanocatalysts are among the most efficient for selective CO₂‐to‐CH₃OH transformation; this conversion, however, suffers from low reactivity especially in the thermodynamically favored low temperature range. We herein report ultrasmall copper (Cu) nanocatalysts supported on crystalline, mesoporous zinc oxide nanoplate (Cu@mZnO) with notable activity and selectivity of CO₂‐to‐CH₃OH in the low temperature range of 200–250 °C. Cu@mZnO nanoplates are prepared based on the crystal‐crystal transition of mixed Cu and Zn basic carbonates to mesoporous metal oxides and subsequent hydrogen reduction. Under the nanoconfinement of mesopores in crystalline ZnO frameworks, ultrasmall Cu nanoparticles with an average diameter of 2.5 nm are produced. Cu@mZnO catalysts have a peak CH₃OH formation rate of 1.13 mol h⁻¹per 1 kg under ambient pressure at 246 °C, about 25 °C lower as compared to that of the benchmark catalyst of Cu−Zn−Al oxides. Our new synthetic strategy sheds some valuable insights into the design of porous catalysts for the important conversion of CO₂‐to‐CH₃OH.

 

Metal nanoparticles (NPs) tethered by synthetic polymers are of broad interest for self-assembly, nanomedicine and catalysis. The binding motifs in polymer ligands usually as the end functional groups of polymers are mostly limited to thiolates. Since the binding motif only represents a tiny fraction of many repeating units in polymers, its importance is often ignored. We herein report the uniqueness of polymeric N-heterocyclic carbene (NHC) ligands in providing oxidative stability and promoting the catalytic activity of noble metal NPs. Two “grafting to” methods were developed for polymer NHCs for pre-synthesized metal NPs in various solvents and with different sizes. Remarkably, imidazolium-terminated polystyrene can modify gold NPs (AuNPs) within 2 min while reaching a similar grafting density to polystyrene-thiol (SH) requiring 6 h modification. We demonstrate that polymer NHCs are extremely stable at high temperature in air. Interestingly, the binding motifs of polymer ligands dominate the catalytic activity of metal NPs. Polymer NHC modified metal NPs showed improved activity regardless of the surface crowdedness. In the case of AuNPs, AuNPs modified with polystyrene NHCs are approximately 5.2 times more active than citrate-capped ones and 22 times more active than those modified with polystyrene thiolates. In view of ligand-controlled catalytic properties of metal NPs, our results illustrate the importance of binding motifs that has been overlooked in the past. 

Janus nanoparticles (NPs) containing two chemically distinct materials in one system are of great significance for catalysis in terms of harnessing catalytic synergies that are not exist in either component. We herein present a novel synthetic method of two Janus-type MnOx-Ag and MnOx-AgI NPs for efficient photochemical water oxidation. The synthesis of Janus-type MnOx-AgI NPs is based on the oxidative nucleation and growth of Ag domains on MnO first and the subsequent iodization of Ag. A mild and non-disruptive iodization strategy is developed to yield Janus MnOx-AgI NPs, in which converting Ag to AgI domains with iodomethane (CH3I) is achieved through the partial iodization. Simultaneously, Mn2+ species in the primary MnO octahedrons are oxidized during the growth of Ag NPs, leading to the formation of amorphous p-type MnOx domains. Therefore, as-resultant Janus-type MnOx-AgI NPs combining two semiconductors into an integrated nanostructure can be used as an efficient photocatalyst for visible light-driven water oxidation. Janus MnOx-AgI NPs show an expected photocatalytic activity even in the absence of Ru(bpy)3Cl2 as an electron mediator. This intriguing synthesis may open up a new opportunity to develop asymmetric nanostructures of two semiconductors that will potentially be efficient photocatalysts for solar-driven water splitting. 

Transcranial magnetic stimulation (TMS) is widely used for noninvasive brain stimulation. However, existing TMS tools cannot deliver targeted neural stimulation to deep brain regions, even though many important neurological disorders originate from there. To design TMS tools capable of delivering deep and focused stimulation, we have developed both electric and magnetic field probes to evaluate and improve new designs and calibrate products. Previous works related to magnetic field measurement had no detailed description of probe design or optimization. In this work, we demonstrated a magnetic field probe made of a cylindrical inductor and an electrical field probe modified from Rogowski coil structure. Both have much smaller size and higher directivity than commercial dipole probes. Using probe, we can calibrate and monitor any new types of TMS coil or array design and verify measured results with the other probe. We mathematically analyze their characteristics and performance and obtained a two-dimensional vector plot of the induced electric field, which matched the measured results from the second type of probe. A commercial circular coil and a figure-8 coil, with relatively complex vector field distribution, were used as examples to demonstrate the high-resolution and accurate measurement capability of our probes.