Abdelilah Safir

Selective self-assembly at room temperature of individual freestanding Ag2Ga alloy nanoneedles

Liquid gallium drops placed on thick Ag films at room temperature spontaneously form faceted nanoneedles of Ag2Ga alloy oriented nearly normal to the surface. This observation suggests that single nanoneedles can be selectively grown by drawing silver-coated microcantilevers from gallium. Needles from 25 nm to microns in diameter and up to 33μm long were grown by this method. These metal-tipped cantilevers have been used to perform atomic force microscopy (AFM) and AFM voltage lithography.

Interaction of hybrid nanowire–nanoparticle structures with carbon monoxide

A gas-phase sensor based on a GaN nanowire mat decorated with Au nanoparticles was studied both experimentally and theoretically. The sensor is responsive to CO and H(2) and could be used to study the water-gas-shift reaction, which involves combining CO and H(2)O to produce H(2). It was shown that for catalyzing this reaction using support Au nanoparticles, the sequence in which the reactants are exposed to the catalyst surface is critical. To quantitatively evaluate the sensor response to gas exposure a depletion model was developed that considered the Au nanoparticle-semiconductor interface as a nano-Schottky barrier where variation in the depletion region caused changes in the electrical conductivity of the nanowires.

Fabrication of an insulated probe on a self-assembled metallic nanowire for electrochemical probing in cells

Conductive nanowire probes that are stiff enough too be inserted inside individual cells could provide unprecedented detail in real-time about the chemistry of living cells and cell compartments including cell membranes, cytosolic organelles and the nucleus. Localization also requires that the probe is insulated except at its end. To enable simple interconnection to an experimental apparatus, the nanowire would need to be attached to a larger platform, e.g. a MEMS device or cantilever (such as used in atomic force microscopes-AFM.) Such a device with 100 nm or less diameter can be fabricated with only a few processing steps by taking advantage of a previously reported technique for self-assembling metal alloy nanowires at selected locations and with desired orientations with respect to the surface [1]. In this report such a concept device and its fabrication process is reported. All steps have been individually demonstrated, although the complete fabrication from end-to-end has yet to be demonstrated at the time of this writing.