We have developed a periodic nucleation and growth mechanism for nanoparticle-aggregated structure based on electron tunneling process that occurs in chemical replacement reactions. This electron tunneling process, which is a fundamental physical phenomenon, successfully explains the repeated formation of nanoparticles that has been observed in the experiment. Using the nanoparticle-mediated progress, we have interpreted the origin of layer-by-layer nanoparticle stacking polycrystalline nanostructures and mesocrystal in chemical reductions.
Pt decorated yolk-shell Cu2O cubes are obtained using a surfactant-free and multiple-step method. Porous yolk-shell cubic structures, together with synergistic effects between Pt and Cu2O, endow the yolk-shell Pt-Cu2O based nonenzymatic H2O2 sensors with enhanced sensing performance.
Contacts of atomic dimensions exhibit properties which are significantly different from the familiar behavior of macroscopic materials. We demonstrate a facile mechanical method using a clock and two silver wires to achieve capture atomic-scale silver contacts at ambient air conditions. One wire was fixed to the hour hand and contacted the other immovable wire slowly with the hour hand movement. The voltages versus time curves were recorded by Tektronix DPO 4034 oscillograph, and corresponding conductance were calculated and exhibited by Origin software. The experiment results show that most individual conductance plateaus are close to integer multiples of the fundamental conductance unit (G 0 ) but definite deviations are also present. It indicates that conductance plateau of atomic contact can be captured by oscillograph with clock movement. If the silver wires are coated with organic molecular, this method has the potential of applying to single molecular switches.
The cation-π interaction is of importance in many chemical and biological processes such as those involving protein geometries and functionals and ion channels. In this study, to understand the cation-π interaction between essential ions and protein in the water-aqueous environment, geometries, electronic structures, bonding properties, and dynamic stabilities of hydrated Na+-phenylalanine clusters Na+(Phe)(H2O)n (n = 0-6) were studied using density functional theory calculations and ab initio molecular dynamics simulations. After the addition of water molecules, Na+(Phe)(H2O)n structures change from a tridentate complex to quadridentate or pentadentate complexes while the cation-π interaction always exists. The fluctuation between quadridentate and pentadentate complexes results from the competition between cation-O bonding and hydrogen bonding. The charge analysis reveals that the positive charge is mainly located on the Na ion, whereas the further addition of water reduces the binding energy of water, electron affinity, and ionization potential. As the number of water molecules increases, the bonding interactions between the sodium ion and the remaining phenylalanine-water complex increase and correlate with the coordination number, in which the electrostatic interaction contributes more than the orbital interaction. The important orbital interaction terms come from the donation of the carboxyl and amino groups and water to the Na+ ion. Molecular dynamic simulations revealed that Na+(Phe)(H2O)6 is stable at 300 K.
We have systematically investigated the crystal-facet-dependent effect of polyhedral Cu2O microcrystals exposed with different-index facets on photodegradation of methyl orange, which provides the convincing evidence that the performance of catalysts can be enhanced by high-index facets tailoring.
This paper presents an in situ chemical vapor reaction in a molten salt (KOH–NaOH, MS) for the synthesis of Pt nanosheets. Unlike conventional solution phase synthesis of nanoparticles in organic and aqueous solutions, no organic surfactant or capping agent was used. The surfactant-free Pt nanosheets were used directly to prepare oxygen reduction electrocatalysts without carbon supports and showed little loss of electrochemical surface area in the accelerated durability test. As the MS has a low vapor pressure under ambient pressure, this approach should also have environmental benefits because of reduced risk for releasing toxic gases from volatile organic solvents (VOCs).
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