Vertical arrays of gold nanorods achieved
(a) Illustration of the experimental setup. The micropatterned substrate is placed in the centre of an Eppendorf tube and immersed in a concentrated colloidal solution of GNR’s. The substrate is left to dry under isothermal conditions. b) Schematic representation of the formation of standing arrays of GNR’s on a template upon solvent evaporation.
Transmission SAXS pattern recorded on a 100 μm × 250 μm section. Gray lines indicate the positions of the hcp reflections (labels are Miller indices (hk) for the reflections; not all are shown for clarity). The inset shows the associated diffraction pattern.
Fabrication of novel self-assembly metallic nanostructures shows great potential for applications in biosensing, optical analysis, computing and solar energy conversion.
Working collaboratively with Instrument Manager Matteo Altissimo, Thibaut Thai of Monash University has combined bottom-up self-assembly processes with top-down techniques to generate vertical arrays of gold nanorods on patterned substrates.
Gold nanorods (GNRs) are of particular interest to researchers as they display unique yet highly variable optical properties. One such property is their remarkable sensing ability, which is exploited during Surface Enhancement Raman Spectroscopy (SERS). During this process GNR’s are closely packed together in a hexaganol-type arrangement forming high density “hot- spots”. If a molecule is within this “hot-spot”, its Raman signal will be greatly amplified.
The Raman signal then acts as a molecular fingerprint and is key in characterising a materials’ chemical structure, temperature or frequency mode.
In past research, controlling the self-assembly process has been a challenge due to the anisotropic nature of the nanorods.
Using a method developed at MCN, researchers were able to control the orientation of the assembly and select a precise location to express the desired features. The mask aligner, reactive ion etching process, electron-beam evaporator and scanning electron microscope were all critical components during the fabrication process.
The accuracy of the micro-patterns was confirmed using small-angle X-ray scattering (SAXS), a characterisation process undertaken using the SAXS beamline at the Australian Synchrotron National Research Facility.
In addition to showcasing the vast array of fabrication and characterisation tools available within MCN, the work highlights the unique relationship between the Australian Synchrotron and MCN, acting in unison as a hub for world-class research.