Spatially Selective Metal Nanoparticle Deposition via Cathodic Corrosion of an Ultramicroelectrode Surface Probe

Spatially selective electrodeposition of metal nanoparticles has been achieved by controlled cathodic corrosion of a scanning electrochemical microscopy probe tip. A platinum (Pt) ultramicroelectrode (UME) positioned close to a substrate was cathodically corroded in neutral pH aqueous solutions to effect electrochemical "sputtering" of metal nanoparticles onto a preselected spot on the substrate. The high cathodic current densities attainable with UMEs enabled the generation of a highly alkaline layer near the tip to facilitate cathodic corrosion. The resultant Pt nanoparticles were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected area electron diffraction. Electrodeposition of these nanoparticles onto a variety of different substrates, including Si wafers, glass microscope slides, and PMMA acrylic sheets, was demonstrated, highlighting the viability of this patterning approach toward insulating substrates and showing that the Pt nanoparticles natively adhered to a variety of substrate types. The size and morphologies of the nanoparticles were affected by the flux of Pt from the ultramicroelectrode probes. Resolution of the features coated with electrochemically sputtered Pt nanoparticles was affected by the position of the probe relative to that of the substrate. In total, this work represents a new method to rapidly and deterministically introduce metal nanoparticles onto arbitrary substrates without the need for a conductive substrate, caustic solutions, or substrate mask.