Preparation of sub 3 nm copper nanoparticles by microwave irradiation in the presence of triethylene tetramin

Molecular Dynamics Simulation of Bulk Cu Material under Various Factors

In this paper, the molecular dynamics (MD) method was used to study the influence of factors of bulk Cu material, such as the effect of the number of atoms (N) at temperature (T), T = 300 K, temperature T, and annealing time (t) with Cu5324 on the structure properties, phase transition, and glass temperature Tg of the bulk Cu material. The obtained results showed that the glass transition temperature (Tg) of the bulk Cu material was Tg = 652 K; the length of the link for Cu-Cu had a negligible change; r = 2.475 Å; and four types of structures, FCC, HCP, BCC, Amor, always existed. With increasing the temperature the FCC, HCP, and BCC decrease, and Amorphous (Amor) increases. With an increasing number of atoms and annealing time, the FCC, HCP, and BCC increased, and Amor decreased. The simulated results showed that there was a great influence of factors on the structure found the gradient change, phase transition, and successful determination of the glass temperature point above Tg of the bulk Cu material. On the basis of these results, essential support will be provided for future studies on mechanical, optical, and electronic properties.

A facile route to transfer Cu nanoparticles to organic medium for better stabilization and improved photocatalytic activity towards N-formylation reaction

Cu nanoparticles were prepared in an aqueous phase by means of a simple reduction-route using sodium borohydride as the reducing agent in the presence of ascorbic acid and polyvinylpyrrolidone (PVP). The hydrosol of the Cu nanoparticles deteriorated within a day. It compelled to initiate a scheme to stabilize the nanoparticles for a long period of time. Phase transfer to organic solvents using Benzyldimethylstearylammonium chloride (BDSAC) as a phase transfer agent was found to be an effective path in this respect. BDSAC performed the dual role of dragging the Cu nanoparticles from water to organic solvent and also acted as a capping agent along with PVP for better stabilization of Cu nanoparticles. The organosol of the Cu nanoparticles exhibited excellent stability and promising catalytic activity towards N-formylation reactions on a number of amine substrates in presence of visible green LED light. The yield and reusability of the catalyst were promising. All the samples were thoroughly characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive analysis of x-rays, x-ray photoelectron spectroscopy and thermo gravimetric analysis.

Melting and Recrystallization of Copper Nanoparticles Prepared by Microwave-Assisted Reduction in the Presence of Triethylenetetramine

The small sized copper nanoparticles (Cu-NPs), prepared in the presence of triethylene tetramine (TETA) and assisted with microwave irradiation, have an extremely low melting temperature. Melting of the small sizezd Cu-NPs can be triggered by the heat generated from the e-beam irradiation during SEM and TEM image construction. The dispersed Cu atoms around the agglomerated big Cu particles can undergo recrystallization immediately due to the strong driving force of the huge temperature difference to normal melting temperature (T_m = 1085 °C). Some of the Cu-NPs with bigger sizes also recrystallize and agglomerate into dense, big particles. According to X-ray diffraction patterns, these particles can agglomerate into compact, ordered Cu crystals in less than five minutes at 60 °C. The melting and recrystallization related endothermic and exothermic phase transitions of Cu-NPs can be found from differential scanning calorimeter (DSC) thermograms and optical microscopic pictures.