Sorting out at nanoscale

A combinatorial library of polyelemental nanoparticles was developed using Dip-Pen Nanolithography, opening up a new field of nanocombinatorics for rapid screening of nanomaterials for a multitude of properties. Credit: Peng-Cheng Chen/James Hedrick

When we pick up an object it may feel smooth, sticky and if we are observing its properties with an instrument we might discover it has magnetic properties, it may be an insulator or a conductor and so on. These characteristics are the result of the trillions of atoms composing the object and their mutual interactions.

If we were to look at clusters of atoms at the nanoscale, lets say tens to thousands atoms, we will also see different properties but these will depend more from the shape of the cluster than from the actual composition: the form is what generate specific characteristics. As an example the quantum dots, now being used in some advanced (not yet in the mass market) display, create a luminescenze whose color (wavelength) depends on the "size" of the dot. By changing it we can change the color of the light emitted.

The problem is how to pick up the right size of a nano particle to get the desired characteristics. We can produce million of nano particles with different sizes but sorting them out to find the one with the right size to match our need is extremely complex and time consuming.

Here is where this news coming from Northwestern University can make a difference.

A team of researchers have developed a tool that allows the ordered deposition of nanoparticles on a chip like surface and creates a library of nano particles. The approach is similar to the one used by gene-chips to sort out the codons or detect specific molecules (including viruses). The gene chip performs thousands of chemical reactions in parallel and singles out the one(s) that yield a specific result. 

They are using five metallic elements, gold, silver, cobalt, nichel and copper, in various sizes, from 1 to 100nm, and use these are reference points. Some of these compositions, and sizes, exist in Nature, but over half of them do not exist, are artificially created. They are building combinatorial libraries with billions of particles and let scientists study their characteristics as well as selecting the ones with given, desired, characteristics.

This can really be a game changer. The wonder of nano-tech is in its capability to create structures starting from the desired properties. This tool may indeed open a Pandora box for a brand new approach to smart material design in the next decade.

Author - Roberto Saracco

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