Researchers at the University of California in San Diego have created metallic nano-articles that can self assemble into larger aggregates to form materials with specific properties.
The research is in the new field of nanoplasmonics: the goal is to develop materials using particles that are smaller than the wavelength of light and that can be used to manipulate a beam of light (or react to it). In the case of this research, the nano particle have the shape of cubes (not “tubes” as we have learn to know). Each nano cube is smaller than 0.1 microns (one thousandth the size of a human hair).
By carefully assembling them it is possible to intercept specific wavelength and change the direction of the beam of light. This makes them ideal for developing very precise antennas or to create lens.
In turns, the creation of antennas and lenses makes it possible to develop chemical and biological sensors (since light interacts with molecules in different ways and the nano antenna would be able to pick up, hence detect, very specific types of interaction and therefore “sense” the presence of a certain molecule. They can also be used to create optical circuits to switch light as needed, therefore creating a sort of optical computer.
The problem, as with all nano particles, is to find a way for self assembling structures: each nano particle is so tiny that on the one hand its manipulation is difficult and takes time, whilst on the other hand the assembling of billions of nano particles results in a lengthy process.
In this case the self assembly is obtained by creating slightly different nano particles depending on what is the goal of the final product. The different geometry leads to a spontaneous self assembly in the exact form required.
Each nano cube (of different size, to create different self assembling units) is made of silver. The resulting product can be used as a sensor that not just detect the presence of a specific molecule but it is also able to monitor a single molecule, see how it moves, reacts and changes over time. This can provide new insight in studying the working “inside” a cell.
To determine the exact size of the cubes needed to develop a material having the desired property the researchers use simulation tools on the computer and once they are satisfied with the result they produce them.
In a demonstration they have been able to create two different “films” of nano particle that although all composed of silver cubes have different reflectivity and transmission properties depending on the wavelength of light.
We can expect by the end of this decade to have even better sensors based on plasmonics and in turns these will improve our understanding of the environment and of our inner work clock.