Expanding the boundaries of metal deposition: High aspect ratio silver nanoplatelets created by merging nanobelts

Electron Beam Induced Enhancement of the Catalytic Properties of Ion-Track Membranes Supported Copper Nanotubes in the Reaction of the P-Nitrophenol Reduction

This study considers the effect of various doses of electron irradiation on the crystal structure and properties of composite catalysts based on polyethylene terephthalate track-etched membranes and copper nanotubes. Copper nanotubes were obtained by electroless template synthesis and irradiated with electrons with 3.8 MeV energy in the dose range of 100–250 kGy in increments of 50 kGy. The original and irradiated samples of composites were investigated by X-ray diffraction technique (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The improved catalytic activity of composite membranes with copper nanotubes was demonstrated by the example of the reduction reaction of p-nitrophenol in the presence of sodium borohydride. Irradiation with electrons at doses of 100 and 150 kGy led to reaction rate constant increases by 35 and 59%, respectively, compared to the non-irradiated sample. This enhancing catalytic activity could be attributed to the changing of the crystallite size of copper, as well as the surface roughness of the composite membrane.

Shape-Selective Electroless Plating within Expanding Template Pores: Etching-Assisted Deposition of Spiky Nickel Nanotube Networks

Nano-objects are favored structures for applications such as catalysis and sensing. Although they already provide a large surface-to-volume ratio, this ratio can be further increased by shape-selective plating of the nanostructure surfaces. This process combines the conformity of autocatalytic deposition with the defined nucleation and growth characteristics of colloidal nanoparticle syntheses. However, many aspects of such reactions are still not fully understood. In this study, we investigate in detail the growth of spiky nickel nanotubes in polycarbonate template membranes. One distinctive feature of our synthesis is the simultaneous growth of nanospikes on both the inside and outside of nanotubes while the tubes are still embedded in the polymer. This is achieved by combining the plating process with locally enhanced in situ etching of the poylmer template, for which we propose a theory. Electron microscopy investigations reveal twinning defects as the driving force for the growth of crystalline nanospikes. Deposit crystallinity is ensured by the reducing agent hydrazine. Iminodiacetic acid is not only used as a complexing agent during synthesis but apparently also acts as a capping agent and limits random nucleation on the spike facets. Finally, we apply our synthesis to templates with interconnected pores to obtain free-standing spiky nickel nanotube networks, demonstrating its ability to homogeneously coat substrates with extended inner surfaces and to operate in nanoscale confinement.

Nucleation-Controlled Solution Deposition of Silver Nanoplate Architectures for Facile Derivatization and Catalytic Applications

Due to their distinctive electronic, optical, and chemical properties, metal nanoplates represent important building blocks for creating functional superstructures. Here, a general deposition method for synthesizing Ag nanoplate architectures, which is compatible with a wide substrate range (flexible, curved, or recessed; consisting of carbon, silicon, metals, oxides, or polymers) is reported. By adjusting the reaction conditions, nucleation can be triggered in the bulk solution, on seeds and by electrodeposition, allowing the production of nanoplate suspensions as well as direct surface modification with open-porous nanoplate films. The latter are fully percolated, possess a large, easily accessible surface, a defined nanostructure with {111} basal planes, and expose defect-rich, particularly reactive edges in high density, making them compelling platforms for heterogeneous catalysis, and electro- and flow chemistry. This potential is showcased by exploring the catalytic performance of the nanoplates in the reduction of carbon dioxide, 4-nitrophenol, and hydrogen peroxide, devising two types of microreactors, and by tuning the nanoplate functionality with derivatization reactions.

The Mixed-Electrode Concept for Understanding Growth and Aggregation Behavior of Metal Nanoparticles in Colloidal Solution

The growth and aggregation behavior of metal nanoparticles can be modulated by surfactants and different other additives. Here the concept of how open-circuit mixed electrodes helps to understand the electrical aspects of nanoparticle growth and the consequences for the particle geometries is discussed. A key issue is the self-polarization effect of non-spherical metal nanoparticles, which causes a local decoupling of anodic and partial processes and asymmetry in the local rates of metal deposition. These asymmetries can contribute to deciding to the growth of particles with high aspect ratios. The interpretation of electrochemical reasons for particle growth and behavior is supported by experimental results of nanoparticle syntheses supported by microfluidics which can supply high yields of non-spherical nanoparticles and colloidal product solutions of high homogeneity.

One-step green synthesis of silver nanobelts assisted by sodium carboxymethylcellulose for catalytic reduction of 4-nitrophenol

Large-scale, ultra-long AgNBs were prepared via a green approach assisted by CMC for the highly efficient catalytic reduction of 4-nitrophenol.