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Making functional nanoparticle assemblies through programmable stacking

(Nanowerk News) Inspired by suprabiomolecular assembly governed by stacking interactions, researchers have developed a versatile strategy to assemble nanoparticles of diverse sizes and compositions into nanoparticle pillars with tailorable internal nanoparticle configurations.
As the scientists report in ACS Nano ("Supra-Nanoparticle Functional Assemblies through Programmable Stacking"), the number, position, size, and composition of the nanoparticles can be rationally regulated in this process.
Self-assembly of a supra-nanoparticle pillar
Self-assembly of the supra-nanoparticle pillar, (3 + 3). (a) Assembly schematic of the pillar (3 + 3). Three gold nanoparticle binding sites are designed on the top and bottom of the DNA origami tile. Each binding site consists of three identical anchoring strands, which are labeled as circles with each color representing a unique DNA sequence. The clusters A and B are mixed and annealed to create a pillar (3 + 3). TEM images of the negative stained (b) cluster A (3 + 3), (c) cluster B (3 + 3), and (d) pillar (3 + 3). The red arrow points to the defect position, where two nanoparticles in one cluster are shared by three DNA tiles. (e) The histogram on the number of layers per pillar, obtained from 117 pillars (3 + 3). (© ACS) (click on image to enlarge)
Supra-biomolecular assemblies provide a vivid illustration of structural complexity achieved through the combination of the molecule's architecture and the interactions of its different parts.
One of the broadly observed morphologies is the linear assembly of small biomolecules, which is commonly used by nature for a variety of biofunctions, including protein signaling and mechanical support and transport. Despite the linear character of this assembly, these structures exhibit a wide variety of architectures such as cylinders and tubes, flat and twisted ribbons, and others, depending on the molecular details.
In this present work, the authors explore adapting the supramolecular design principles for assembly of nanomaterials in a desired linear configuration.
By combining programmable stacking interactions and the modularity of assembled planar nanoparticle clusters, they achieve supra-nanoparticle assembly of well-defined linear, pillar-like, morphology with a tailorable structure and composition.
Detailed structural characterization using electron microscopy and X-ray scattering methods reveals that the assembled architectures are in a close correspondence with the designs, thus demonstrating the strength of this approach.
Moreover, the modularity permits the assembly of both homoand heteroparticle structures.
The proposed assembly scheme, as the researchers show, can be used for the control of optical responses of nanostructures and, potentially, in molecular electronics and energy transfer.
They used these assembled pillars to study the collective plasmon resonance for metal nanostructures, and the measured electrical transport properties of these pillared metal nanostructures may enable their application in molecular electronics.
"Our developed assembly approach offers a general method of creating layered, pillared heterostructures with controllable linear morphology and nanoparticle configurations, and it may be used potentially for creation of future nanoparticle-based functional materials," the authors conclude.
By Michael is author of two books by the Royal Society of Chemistry: Nano-Society: Pushing the Boundaries of Technology and Nanotechnology: The Future is Tiny.
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