Tailored gold nanostructure arrays as catalysts for oxygen reduction in alkaline media and a single molecule SERS platform

Abstract

Although plenty of functional nanomaterials are widely applied in science and technology, cost-efficient, controlled and reproducible fabrication of metallic nanostructures is a considerable challenge. Automated electrorefining by scanning electrochemical microscopy (SECM) provides an effective approach to circumvent some drawbacks of traditional homogeneous syntheses of nanoparticles, providing precise control over the amount, time and place of reactant delivery. The precursor is just a raw metal, which is the most economically viable source. This approach ensures reproducibility and the opportunity for fabrication of micropatterns, which can be rapidly analyzed by scanning probe techniques. Here, a cost-effective methodology for the preparation of naked (ligand-free) metallic nanostructures, from polycrystalline gold using a moving microelectrode, is presented. Automated micropatterning of bare gold on indium tin oxide (ITO) demonstrates the versatility of this method to tune the size and shape of the nanostructures. The morphology of the obtained materials and thus their catalytic and plasmonic properties can be tuned using the electrorefining parameters. Programmable fabrication of sample microarrays by microprinting followed by comparative SECM studies or spectroscopic analysis allows quick optimization and characterization for specific purposes. Electrocatalytic oxygen reduction in alkaline media and surface-enhanced Raman spectroscopy (SERS) of single porphycene molecules are presented as model examples.

Spectroscopy and Tautomerization Studies of Porphycenes

“…Not only fluorescence but also surface-enhanced resonance Raman spectra (SERRS) of single molecules could be recorded for porphycene 1 placed on gold and silver nanostructures. , In a few cases, Raman spectra collected consecutively at 0.3-ns intervals exhibited spectral changes that were explained as being due to the transient, short-time presence of the cis1 tautomeric species (Figure ). As discussed in the next section, the metal support might indeed induce the trans–cis1 conversion.…”

Scanning Probe Microscopy for Nanoscale Electrochemical Imaging

“…A nanopipet filled with an organic phase (benzotrifluoride (BTF)) was used as a SECM tip to detect superoxide anion . Programmable fabrication of sample microarrays by microprinting followed by comparative SECM was investigated for quick optimization and characterization for specific purposes …”

“…63 Programmable fabrication of sample microarrays by microprinting followed by comparative SECM was investigated for quick optimization and characterization for specific purposes. 64 SG-TC SECM was employed for studying HER at the surface of AZ31 as a model Mg alloy. 65 Jamali et al characterized the active and passive domains on AZ31 using different modes of SECM.…”

Patterning Cu nanostructures tailored for CO2 reduction to electrooxidizable fuels and oxygen reduction in alkaline media

“…Such an approach allows simple preparation of multiple patterns of nanostructures deposited on a single support sample under various conditions inuencing the catalytic properties of the obtained nanomaterials. This enables rapid scanning electron microscopy (SEM) and microscale SECM analyses [79][80][81][82] and optimization of the experimental parameters of the electrorening process. The morphology and thus the electrocatalytic properties of CuNSs are tuned by adjusting the electrolyte composition, electrodeposition potential and Cu source translation rate.…”