Rapid synthesis of Pd single‐atom/cluster as highly active catalysts for Suzuki coupling reactions

Palladium(Pd)‐based catalysts are essential to drive high‐performance Suzuki coupling reactions,which are powerful tools for the synthesis of functional organic compounds.Herein,we developed a solution‐rapid‐annealing process to stabilize nitrogen‐mesoporous carbon supported Pd single‐atom/cluster(Pd/NMC)material,which provided a catalyst with superior performance for Suzuki coupling reactions.In comparison with commercial palladium/carbon(Pd/C)catalysts,the Pd/NMC catalyst exhibited significantly boosted activity(100%selectivity and 95%yield)and excellent stability(almost no decay in activity after 10 reuse cycles)for the Suzuki coupling reactions of chlorobenzenes,together with superior yield and excellent selectivity in the fields of the board scope of the reactants.Moreover,our newly developed rapid annealing process of precursor solutions is applied as a generalized method to stabilize metal clusters(e.g.Pd,Pt,Ru),opening new possibilities in the construction of efficient highly dispersed metal atom and sub‐nanometer cluster catalysts with high performance.

A Silicon Cluster Based Single Electron Transistor with Potential Room-Temperature Switching

We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is deter- mined to be a Si 170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300meV, which is a result of the large capacitance of a small silicon quantum dot （-1.8 nm）. This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time.

A combinatorial descriptor for volcano relationships of electrochemical nitrogen reduction reaction

Though touted as a potential way to realize clean ammonia synthesis,electrochemical ammonia synthesis is currently limited by its catalytic efficiency.Great effort has been made to find catalysts with improved activity toward electrochemical nitrogen reduction reaction(eNRR).Rational screening of catalysts can be facilitated using the volcano relationship between catalytic activity and adsorption energy of an intermediate,namely,the activity descriptor.In this work,we proposeΔG^(*)_(NH_(2))+ΔG^(*)_(NNH)as a combinatorial descriptor,which shows better predictive power than traditional descriptors using the adsorption free energies of single intermediates.The volcano plots based on the combinatorial descriptor exhibits peak activity fixedly at the descriptor value corresponding to the formation free energy of NH3,regardless of the catalyst types;while the descriptor values correspond to the top activities for eNRR on volcano plots based on single descriptors usually vary with the types of catalysts.

Rational design of palladium single-atoms and clusters supported on silicoaluminophosphate-31 by a photochemical route for chemoselective hydrodeoxygenation of vanillin

Chemoselective hydrodeoxygenation of vanillin is of great importance in converting biomass into high value-added chemicals.Herein,we describe a facile photochemical route to access palladium single atoms and clusters supported on silicoaluminophosphate-31(SAPO-31)as a highly active,chemoselective,and reusable catalyst for hydrodeoxygenation of vanillin.Characterizations by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy,extended X-ray absorption fine structure measurement,and CO-absorbed diffuse reflectance infrared Fourier transform spectroscopy reveal the atomically dispersed palladium single atoms and clusters are loosely bonded and randomly dispersed,without forming strong palladium-palladium metallic bonding,over the SAPO-31 support.This catalyst,with a full metal availability to the reactants,exhibits exceptional catalytic activity(TOF:3,000 h^(−1),Yield:>99%)in the hydrodeoxygenation of vanillin toward 2-methoxy-4-methylphenol(MMP)under mild conditions(1 atm,80°C,30 min),along with excellent stability,scalability(up to 100-fold),and wide substrate scope.The superior catalytic performance can be attributed to the synergistic effect of the positively charged palladium single atoms and fully exposed clusters,as well as the strong metal-support interactions.This work may offer a new avenue for the design and synthesis of fully exposed metal catalysts with targeted functionalities.

Fast time-division color electroholography using a multiple-graphics processing unit cluster system with a single spatial light modulator

We demonstrate fast time-division color etectroholography using a multiple-graphics-processing-unit （GPU） cluster system with a spatial light modulator and a controller to switch the color of the reconstructing light. The controller comprises a universal serial bus module to drive the liquid crystal optical shutters. By using the controller, the computer-generated hologram （CGH） display node of the multiple-GPU cluster system synchronizes the display of the CGH with the color switching of the reconstructing light. Fast time-division color electroholography at 20 fps is realized for a three-dimensional object comprising 21,000 points per color when 13 GPUs are used in a multiple-GPU cluster system.

Specific detection and effective inhibition of a single bacterial species in situ using peptide mineralized Au cluster probes

Increasingly serious microbial infections call for the development of new simpler methods for the precise diagnosis and specific inhibition of such pathogens. In this work, a peptide mineralized Au cluster probe was applied as a new simplified strategy to both recognize and inhibit a single bacteria species of Staphylococcus aureus(S. aureus) simultaneously. The probes are composed of peptides and Au clusters. Moreover, the peptides specifically target S. aureus cells and the Au clusters provide fluorescent imaging and have an antibacterial effect. These new probes enable the simultaneous specific detection and effective destruction S. aureus cells in situ.