Synthesis and Properties of the Self-Assembly of Gold-Copper Nanoparticles into Nanoribbons.

We report the efficient wet-chemical production of self-assembled gold-copper bimetallic nanoparticles (diameter of ∼2 nm) into two-dimensional flexible ribbonlike nanostructures. The direct observation of a layered arrangement of particles into nanoribbons was provided through high-resolution transmission electron microscopy and electron tomography. These nanoribbons showed photoluminesce and efficient photocatalytic activity for the conversion of 4-nitrophenol. The thermal stability of the nanoribbons was also measured by in situ heat treatment in the electron microscope, confirming that the self-assembled gold-copper nanoribbons efficiently supported up to 350 °C. The final morphology of the nanoparticles and their ability to self-assemble into flexible nanoribbons were dependent on concentration and the ratio of precursors. Therefore, these experimental factors were discussed. Remarkably, the presence of copper was found to be critical to triggering the self-assembly of nanoparticles into ordered layered structures. These results for the synthesis and stability of self-assemblies of metallic nanoparticles present a potential extension of the method to producing materials with catalytic applications.

Helical Growth of Ultrathin Gold-Copper Nanowires.

In this work, we report the synthesis and detailed structural characterization of novel helical gold-copper nanowires. The nanowires possess the Boerdijk-Coxeter-Bernal structure, based on the pile up of octahedral, icosahedral, and/or decahedral seeds. They are self-assembled into a coiled manner as individual wires or into a parallel-ordering way as groups of wires. The helical nanowires are ultrathin with a diameter of less than 10 nm and variable length of several micrometers, presenting a high density of twin boundaries and stacking faults. To the best of our knowledge, such gold-copper nanowires have never been reported previously.

PDDA induced step-pyramidal growth of nickel-platinum (Ni-Pt) nanoparticles for enhanced 4-nitrophenol reduction.

Herein, we report the synthesis of novel platinum-based nanoparticles with step-pyramidal growth induced by poly(diallyldimethylammonium chloride) (PDDA). The complex stepped pyramidal shape became the central point for outstanding catalytic reduction of 4-nitrophenol, overcoming the activity of bare Pt nanoparticles. These results are valuable for the catalytic degradation of reactive molecules.

Structural and Electronic Characterization Through Spectroscopy Analysis of Gd-Gd2O3 Nanoparticles.

Based on the new necessity of residual dispensing of heavy metals (or even more, rare earths) that are part of the composition of multiple electronic components as the cellular phones or computers; this work reports the use of physical processes for taking advantage of elements from the electronic residues. Recycling and processing to generate nanomaterials is an attractive option, because the economic and ecologic perspectives. In this work, Gd-Gd2O3 nanoparticles (through a sonic-chemical method at room temperature assisted with Tannic acid as reduction agent), is reported. The structure characterization was performed over the samples using complementary techniques such as transmission electron microscopy, X-ray diffraction, Raman and infrared spectroscopies. The obtained results are related to self-assembling mechanisms. As a complement, Ultraviolet-visible absorbance data was used to determine some electronic properties such as band structure. Therefore, this work has demonstrated the possibility of synthesizing lanthanide nanoparticles without burning the samples.

Gold-copper nanostars as photo-thermal agents: synthesis and advanced electron microscopy characterization.

Nanoalloys have emerged as multi-functional nanoparticles with applications in biomedicine and catalysis. This work reports the efficient production and the advanced transmission electron microscopy characterization of gold-copper pentagonal nanostars. The morphology of the branches is controlled by the adequate choice of the capping agent. When oleylamine is used rounded nanostars are produced, while pointed nanostars are obtained by using hexadecylamine. Both types of nanostars were proved to be thermally stable and could therefore be used as therapeutic agents in photo-thermal therapies as confirmed by the near-infrared absorption spectra.