Wednesday, February 5, 2014

Nanostructures

A nanostructure is an object of intermediate size between microscopic and molecular structures.

In describing nanostructures it is necessary to differentiate between the number of dimensions on the nanoscale. Nanotextured surfaces have one dimension on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes have two dimensions on the nanoscale, i.e., the diameter of the tube is between 0.1 and 100 nm; its length could be much greater. Finally, spherical nanoparticles have three dimensions on the nanoscale, i.e., the particle is between 0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles (UFP) often are used synonymously although UFP can reach into the micrometre range. The term 'nanostructure' is often used when referring to magnetic technology.

Devices built from three-dimensional nanoarchitectures offer a number of advantages over those based on thin-film technology, such as larger surface area to enhance the sensitivity of sensors, to collect more sunlight to improve the efficiency of solar cells, and to supply higher density emitters for increased resolution in flat panel displays. Three-dimensional nanoscale assembly has already been used to generate many prototypes of devices and sensors, including piezoelectric nanogenerators based on ZnO nanowire arrays, photovoltaic devices based on silicon nanowire array p-n junctions, and highly sensitive gas sensors based on metal oxide nanowire arrays among others. 



A fantastic tinsel-like CdS nanostructure. The nanowires were created on Cd-coated copper foils via a solvothermal reaction combined with electroplating.
Credit: y Xiangmin Meng and co-workers at Hefei University of Technology and the Chinese Academy of Sciences.


ZnO nanoparticles obtained by hydrothermal synthesis using microwave heating.
Credit: FEI Company, FRANCISCO RANGEL


Gold Nanostructures
These feather-like nanostructures are made of gold. As gold particles get smaller in size they interact with light differently, producing different colors.


Crystalline nanostructures, known as metal organic frameworks (MOFs), should significantly extend the range of natural gas-powered vehicles.
Credit: Professor Yaghi (University of California, Berkeley).



3-dimensional Si composite nanostructure. The image was taken with a scanning electron microscope and is colour modified using the colour balance function in Adobe Photoshop. The material is both amorphous and crystalline in nature with dimensions less than 2 mm.
Credit: Ghim Wei Ho, University of Cambridge Nanoscale Science Laboratory