Self Assembly of Nanoparticles

Other Unique Engineering Ideas

Nanoparticles possess some amazing properties of strength and power and they are also delicate little things, when it comes to manipulating them for use in nanodevices. Many scientists consider that the most promising method of incorporating nanoparticles into functional structures is through their own self-assembly, an approach commonly attempted through different lithography techniques.

1. Description

2. Why: Self Assembly

3. How Does It Work

4. Future Trends

5. Related Links

 Useful links: Self-assembly, Molecular self-assembly

Description

Self-assembly is emerging as an elegant, "bottom-up" approach to fabricating nanostructured materials. Furthermore, by combining the ease and control of self-assembly based on organic materials with the special electronic, magnetic or photonic properties of inorganic components, powerful new functionality can be achieved.Two types of self-assembled systems.

  • Uniform, extended nanocrystal monolayer superlattices.
  • Copolymer-templated nanoparticle aggregates.

In the latter, control of the metal-metal and metal-polymer interactions can be used to produce either dense chains of closely-spaced but separate nanoparticles or continuous nanowires.

Why: Self Assembly

Arranging these particles by hand and/or scanning microscope tips is technologically impractical due to the unfeasible amount of time it would take. Therefore, nano engineers manipulate the nanoparticles’ properties by various treatments so that they can simply “dump” the particles in a treated area, whereby they automatically arrange themselves. This ability is, in a sense, the basis of all nanotechnology.It is possible to generate species of the same element, which behave differently or exhibit different chemical reactivity, depending on their spatial location. This way, one can have different functional structures by performing selective chemical reactions. The importance of self-assembly in nanotechnology is further emphasized by the fact that the nanostructures are prone to destruction by the conventional methods in semiconductor processing. For example, if we are to employ the quantum dots for applications, we should be able to interconnect them so that they can communicate to each other.

How Does it Work

The scientists used luminescent yttrium aluminum garnet (YAG) nanoparticles assembled on a silicon wafer, synthesizing the particles through doping and crystallization to determine their shape and composition.Before placing the particles on silicon wafers, the scientists pre-patterned the wafers using etching techniques based on a phenomenon called “atomic step movement.”Since atom-high steps innately exist on silicon surfaces, the scientists could move these steps during high-temperature treatments to fabricate a desired pattern.Chemical reactions (between the silicon, nitrogen and oxygen) caused very thin nitride linings to form in accordance with the atomic step boundaries, thereby pre-patterning the wafers. It is possible to achieve precise “nanoarchitecturing” involving many sorts of applications with the ability to assemble particles that have a particular wavelength or magnetic property by selectively activating or sensing such properties.The organization of inorganic nanostructures within self-assembled organic or biological templates is receiving the attention of scientists interested in developing functional hybrid materials. Previous efforts have concentrated on using such scaffolds to spatially arrange nanoscopic elements as a strategy for tailoring the electrical, magnetic or photonic properties of the material. 

Future Trends

The assembly of nanoparticles of two different materials into a binary nanoparticle superlattice is a promising way of synthesizing a large variety of materials metamaterials) with precisely controlled chemical composition and tight placement of the components. In theory only a few stable binary superlattice structures can assemble from hard spheres, potentially limiting this approach.Recent theoretical arguments have suggested that synergistic interactions between self-organizing particles and a self-assembling matrix material can lead to hierarchically ordered structures.Organization of both the polymeric and particulate entities is thus achieved without the use of external fields, opening a simple and general route for fabrication of nanostructured materials with hierarchical order. 

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