Catalytic Activity of Ni Nanotubes Covered with Nanostructured Gold

Ni nanotubes (NTs) were produced by the template method in the pores of ion-track membranes and then were successfully functionalized with gold nanoparticles (Ni@Au NTs) using electroless wet-chemical deposition with the aim to demonstrate their high catalytic activity. The fabricated NTs were characterized using a variety of techniques in order to determine their morphology and dimensions, crystalline structure, and magnetic properties. The morphology of Au coating depended on the concentration of gold chloride aqueous solution used for Au deposition. The catalytic activity was evaluated by a model reaction of the reduction of 4-nitrophenol by borohydride ions in the presence of Ni and Ni@Au NTs. The reaction was monitored spectrophotometrically in real time by detecting the decrease in the absorption peaks. It was found that gold coating with needle-like structure formed at a higher Au-ions concentration had the strongest catalytic effect, while bare Ni NTs had little effect. The presence of a magnetic core allowed the extraction of the catalyst with the help of a magnetic field for reusable applications.

Structuring Free-Standing Foils for Laser-Driven Particle Acceleration Experiments

The recent development of petawatt-class laser systems sets a focus on the development of ultra-thin free-standing targets to access enhanced particle acceleration schemes vital for future applications, such as, medical and laser-driven nuclear physics. Specific strategies are required to improve the laser-to-particle energy conversion efficiency and increase the maximum particle energy. One of the promising approaches is based on the target design optimization; either by tuning key parameters which will strongly affect the laser-matter interaction process (e.g., material, composition, density, thickness, lateral dimensions, and shape) or by using micro/nanostructures on the target surface. At ELI-NP, considerable efforts are dedicated to extend the target capabilities beyond simple planar target design and develop complex targets with tailored properties suitable for high-power laser-plasma interaction experiments, as well as for studies with gamma and positrons beams. The paper provides an overview of the manufacturing capabilities currently available within ELI-NP Targets Laboratory for providing users with certain types of solid targets, specifically micro/nanostructured gold and copper foils and microns thick, porous anodized alumina. Also, optimization studies of alternative patterns (micro/nanodots) on silicon substrate are presented for future implementation on metallic free-standing thin foils.

Adsorption/Desorption Behaviors and SERS Chemical Enhancement of 6-Mercaptopurine on a Nanostructured Gold Surface: The Au20 Cluster Model

Computational approaches are employed to elucidate the binding mechanism and the SERS phenomenon of 6-mercaptopurine (6MP) adsorbed on the tetrahedral Au20 cluster as a simple model for a nanostructured gold surface. Computations are carried out in both vacuum and aqueous environments using a continuum model. In the gaseous phase and neutral conditions, interaction of 6MP with the gold cluster is mostly dominated by a covalent Au−S bond and partially stabilized by the Au⋅⋅⋅H−N coupling. However, in acidic solution, the nonconventional Au⋅⋅⋅H−S hydrogen-bond becomes the most favorable binding mode. The 6MP affinity for gold clusters decreases in the order of vacuum > neutral solution > acidic medium. During the adsorption, the energy gap of Au20 substantially declines, leading to an increase in its electrical conductivity, which can be converted to an electrical noise. Moreover, such interaction is likely a reversible process and triggered by either the low pH in sick tissues or the presence of cysteine residues in protein matrices. While N−H bending and stretching vibrations play major roles in the SERS phenomenon of 6MP on gold surfaces in neutral solution, the strongest enhancement in acidic environment is mostly due to an Au⋅⋅⋅H−S coupling, rather than an aromatic ring-gold surface π overlap as previously proposed.

Trends in Sustainable Synthesis of Organics by Gold Nanoparticles Embedded in Polymer Matrices

Gold nanoparticles (AuNPs) have emerged in recent decades as attractive and selective catalysts for sustainable organic synthesis. Nanostructured gold is indeed environmentally friendly and benign for human health; at the same time, it is active, under different morphologies, in a large variety of oxidation and reduction reactions of interest for the chemical industry. To stabilize the AuNPs and optimize the chemical environment of the catalytic sites, a wide library of natural and synthetic polymers has been proposed. This review describes the main routes for the preparation of AuNPs supported/embedded in synthetic organic polymers and compares the performances of these catalysts with those of the most popular AuNPs supported onto inorganic materials applied in hydrogenation and oxidation reactions. Some examples of cascade coupling reactions are also discussed where the polymer-supported AuNPs allow for the attainment of remarkable activity and selectivity.

Preparation, Functionalization, Modification, and Applications of Nanostructured Gold: A Critical Review

Gold nanoparticles (Au NPs) play a significant role in science and technology because of their unique size, shape, properties and broad range of potential applications. This review focuses on the various approaches employed for the synthesis, modification and functionalization of nanostructured Au. The potential catalytic applications and their enhancement upon modification of Au nanostructures have also been discussed in detail. The present analysis also offers brief summaries of the major Au nanomaterials synthetic procedures, such as hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, sonochemical deposition, electrochemical deposition, microwave and laser pyrolysis. Among the various strategies used for improving the catalytic performance of nanostructured Au, the modification and functionalization of nanostructured Au produced better results. Therefore, various synthesis, modification and functionalization methods employed for better catalytic outcomes of nanostructured Au have been summarized in this review.