Nanoscale structures are the building blocks of much of the world around us. They are responsible for the strength and stiffness of materials, the electrical and optical properties of semiconductors, and the mechanical, chemical, and biological behavior of substances at the nanometer scale.
A nanostructure is any structure with at least one dimension measuring less than 100 nanometers (nm). This size range includes objects as small as a single atom or molecule and extends up to about 100 nm, which is still very small compared to most everyday objects. The term “nanostructure” was first coined in 1974 by Professor Norio Taniguchi from Tokyo University, who defined it as follows: “Structures with at least one linear dimension ranging from 1-100 nm or 1/1000th of a micrometer (μm)”. In other words, nanostructures are simply very small structures.
The study of nanoscale phenomena is known as “nanoscience”. It is an interdisciplinary field that draws on knowledge from many different disciplines including physics, chemistry, materials science, engineering, biology, and medicine. Due to their tiny size, nanostructures often exhibit unique physical, chemical, and optical properties that differ from those of larger objects made from the same material. For example, nanoparticles of gold are red because they absorb light in the blue part of the visible spectrum. Similarly, carbon nano tubes are extremely strong yet lightweight because their cylindrical shape makes them ideal for withstanding stress. These unusual properties have led to many new applications for nanomaterials in fields such as electronics, energy storage, healthcare, and environmental remediation.
Most manufactured nanomaterials today are produced using top-down methods such as lithography, which involves carving or etching away material to create features on a surface. However it is also possible to build up complex three-dimensional nanostructures using bottom-up approaches such as self-assembly, where smaller components spontaneously arrange themselves into larger patterns or shapes according to specific interactions between their molecules (e.g., hydrogen bonding or van der Waals forces). Nanoprinting techniques that combine both top-down and bottom-up processes are also being developed. These allow for greater control over the shape and size of final nanoobjects while also reducing waste material. Ultimately though, all manufacturing methods must be able to produce reliable results on a large scale if commercial products are to be made from nano materials.
Assembling individual atoms or molecules into desired structures is challenging enough but making these structures interact with each other in useful ways is an even bigger challenge. One way to overcome this challenge is by using DNA origami. This method uses long strands of DNA (the genetic material found in all living organisms) like scaffolding upon which smaller molecules can be assembled in predetermined patterns. Another promising method under development involves directed self-assembly. This approach takes advantage not only attractive interactions between molecules but also repulsive ones (e.g., electrostatic forces). By carefully controlling these different types interactions it should be possible to guide molecular assemblies into desired shapes or arrangements.[23