Researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have devised a technique whereby self-assembling nanoparticle arrays can form a highly ordered thin film over macroscopic distances in just one minute.
Inducing nanoparticles to self-assemble into complex structures and hierarchical patterns, similar to what nature does with proteins, would enable mass-production of devices a thousand times smaller those used in today’s microtechnology, according to the researchers.
The researchers combined supramolecules based on block copolymers with gold nanoparticles to create nanocomposites that under solvent annealing quickly self-assembled into hierarchically-structured thin films spanning an area of several square centimeters.
The technique is compatible with current nanomanufacturing processes and has the potential to generate new families of optical coatings for applications in a wide number of areas including solar energy, nanoelectronics and computer memory storage.
“Our technique can rapidly generate amazing nanoparticle assemblies over areas as large as a silicon wafer,” said Ting Xu, a polymer scientist “You can think of it as pancake batter that you can spread over a griddle, wait one minute and you have a pancake ready to eat,” said researcher Ting Xu, a polymer scientist.
Xu and her colleagues incorporated arrays of gold nanoparticles into solutions of supramolecules to form 200nm thick films. The group found that by optimizing the amount of solvent the assembly kinetics could be precisely tailored to produce hierarchically structured thin films in a single minute. “We added only a very small amount of solvent, about 30-percent of the fraction of a 200 nanometer thick film,” said Xu.
Through solvent annealing, with chloroform as the solvent, the nanoparticle arrays organized into three-dimensional cylindrical microdomains packed into distorted hexagonal lattices in parallel orientation with the surface.
Xu said that their process presents a viable alternative to lithography for making metamaterials, adding “we should be able to create a library of nanoparticle assemblies engineered for light manipulation and other properties using a technique that is compatible with today’s most widely used nanomanufacturing processes, including blade coating, ink-jet printing and dynamic zone annealing.”
Xu’s team has described their process in Nature Communications. This research was funded by the DOE Office of Science and made use of the Advanced Photon Source at Argonne National Laboratory.
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