Self Assembly and Nanoparticles
By: Stephanie Ng
For nanoparticles, self assembly is a useful procedure since it will improve the speed at which they can assemble into a well-defined configuration. Self assembly involves the spontaneous interaction of individual components of a system to form a larger functional unit. In nanoparticles, the well-defined configuration is important for forming units in a compact space, allowing more information to be stored. Self assembly will also provide a way for nanoparticles to form more complex structures to be used for a variety of different purposes.
Overall, self assembly relies on the idea that the fully assembled components are in equilibrium with the individual components, minimizing the Gibbs free energy. At a molecular level, the particles will gather into a stable structure due to intermolecular forces between the individual particles. In effect, it is desirable to a minimization of repulsive forces while having maximization of attractive forces between the particles. The most common forces that are in play for self assembly are van der Waals forces, hydrogen bonds, or weak polar forces. Self assembly will continue occurring until the lowest energy configuration is found, making the structure stable in nature.
The use of self assembly in nanoparticles makes it easier to form different products, such as electronic parts or technology with regards to drug delivery or other biological applications. As the technological field advances, nanoparticles develop more functions, making self assembly an important process in reference to size and time used to make items. In addition, self assembly can occur with a variety of materials, potentially even with a mix of nanoparticle type materials. For example, the formation of binary nanoparticle superlattices (BNSLs) can lead to a general and inexpensive path to many metamaterials, allowing for precise chemical composition and tight component placement. These superlattices may possess different combinations of stabilizing forces, contributing to their huge variety.
In their practical aspect, nanoparticles can be used to form nanoparticle or nanowire based devices, amongst other technologies. One such method involves the use of electrostatic interactions, which yields a few advantages. First, the method can be long-range, which may be difficult in other investigated self assembly areas such as protein recognition or DNA hybridization. Furthermore, this method is non-material specific, leading to trapping of any particle type. After formation, these nanowires can be placed in various electronics. Therefore, the process of self assembly helps make product creation more efficient.
Citations:
1. Shevchenko, E.V. et al., Structural diversity in binary nanoparticle superlattices. Nature. [Online] 2006, 439, 55-59 www.nature.com/nature/journal/v439/n7072/full/nature04414.html (accessed June 28, 2016).
2. Barry, CR, Hoon, CJ, Jacobs, HO., Approaching Programmable Self-Assembly from Nanoparticle -Based Devices to Integrated Circuits. Foundations of Nanoscience. [Online] 2004, 21-23 www.researchgate.net/publication/228716565_Approaching_Programmable_Self-Assembly_from_Nanoparticle-Based_Devices_to_Integrated_Circuits (accessed June 28, 2016).
