High-Yield Assembly of Gold Nanorod Pairs is Quicker, Cheaper

  • Published
  • By Heyward Burnette, AFRL/RX
  • Materials and Manufacturing
WRIGHT-PATTERSON AIR FORCE BASE, Ohio --  An Air Force Research Laboratory collaboration has developed a solvent-based method for assembling large quantities of gold nanorod pairs, significantly decreasing the time - and therefore cost - required by the traditional process of top-down electron beam lithography

The optical and electrical properties of gold nanostructures depend on the precise arrangement of the constituent nanoparticle building blocks. The ability to control self assembly and produce relevant quantities of gold nanostructures enables their application to technologies such as lasers and sensors. The new method also provides scientists with greatly improved techniques to investigate atomic scale phenomena.

Electron beam lithography (EBL) is the common method for creating gold nanorods. This method requires coating a thin film of gold with a layer that is sensitive to a focused electron beam. The focused electron beam writes a pattern in this coating, which is then removed to reveal a patterned gold layer. This process takes many hours to write nanoscopic features across macroscopic (100 mm2) surfaces.

AFRL scientists from the Materials & Manufacturing and the Air Force Office of Scientific focused on the interactions between nanoparticles in solution. By independently tuning the attractive and repulsive potentials between nanoparticles, they were able to precisely control their assembly process. Depending on the composition and concentration of the solution, a wide range of different nanorod assembles could be created, ranging from individual clusters consisting of rod pairs or triplets, to extended chains containing hundreds of nanorods. The bonding between the nanorods in the assemblies could be tailored so that additional purification or chemistry could be conducted

The conventional EBL approach would take approximately 344 days to produce the same number of stable nanorod pairs produced in seven hours by the new process. The large-volume and high-yield process shows great potential for future applications in areas such as imaging, lasers, chemical and biological sensors, and communication devices.