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

Abstract

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.

Electroless Nanoplating of Pd−Pt Alloy Nanotube Networks: Catalysts with Full Compositional Control for the Methanol Oxidation Reaction

“…[2] Pd/Pt nanostructures are employed for catalyzing a large variety of chemical reactions. We chose the methanol electrooxidation, which is of tremendous interest for fuel cell applications, [1,5,9,18,21,[35][36][37][38] as a model reaction for investigating the composition-dependent catalytic properties of our NT networks. Pt catalysts employed in the oxidation of small organic molecules are susceptible to poisoning through intermediates such as CO, which strongly bind to the active sites.…”

“…This challenge is commonly overcome by using template-guided metal depositions. [1,2,[6][7][8][9]12,[35][36][37][38] The conventional electroless plating of macroscopic template components advanced to metal deposition onto nanostructured templates. For instance, it is possible to reliably and independently control the density, diameter, interconnectivity and shape of the template pores and thus the morphology of the resulting NTs through ion-track-etching technology.…”

“…[1,2,7,8] Among various synthesis routes to prepare PdÀ Pt catalysts for catalytic applications, [39][40][41][42][43][44] electroless plating represents a facile solution deposition method with excellent scalability and conformity, making it a very promising tool for nanofabrication. [1,2,[6][7][8][9]12,[35][36][37][38] In contrast to other deposition methods such as electrodeposition or evaporation, it requires neither complex instrumentation nor specific template properties (e. g., conductivity or heat-resistance). Furthermore, due to its excellent conformity, it is compatible with complex shaped substrates and recessed surfaces.…”

Dual Metastability in Electroless Plating: Complex Inertness Enabling the Deposition of Composition‐Tunable Platinum Copper Alloy Nanostructures

“…The final plating baths featured a constant en content of 245 m m . Ion‐track etched polycarbonate membranes were used as model substrates for the template‐assisted synthesis of 1D nanostructures . These membranes incorporate channel‐shaped pores of high aspect ratio, and therefore represent an excellent platform for testing the nanoscale homogeneity and conformity of the deposit.…”

“…These membranes incorporate channel‐shaped pores of high aspect ratio, and therefore represent an excellent platform for testing the nanoscale homogeneity and conformity of the deposit. Being intrinsically inactive, polymer membranes have to be decorated with catalytic metal nanoparticles like Ag or Pd prior to plating in order to initiate metallization . Opposed to the autocatalytic deposition of pure copper [Eq.…”