Nanotechnology - Why 'nano' ?

Along with bio, nano is the most popular scientific prefix of the moment. Why ? A nanometer, that is the size of a large molecule, a single unit cell of a crystal or some atoms on a row. In a world built of such atoms, the nanometer imposes a limit to downscaling, which shows its benefits in many areas, e.g. in micro-electronics where we can store more data with less material simply by making things smaller.

But this is not the only advantage of 'nano'. Nanomaterials are intrinsically different from their bulk counterparts. Their properties depend on their composition (as in bulk) but more importantly on their size and shape ! Gold crystals of a few nanometer in diameter are not yellow, but red ! Cadmium Selenide (CdSe) quantum dots emit light with a color that depends on their size (see Figure). But there is more ! Science at the nanoscale is an inevitable crossroad of physics, chemistry and biotech. Ideas and concepts from different fields have to be combined to study and understand the fascinating world at the extremes that is the nanoscale. This makes working in nanoscience a challenging but rewarding experience.

CdSe size series under UV excitation: largest crystals emit red, smallest emit blue lightLayer of nanocrystals deposited on TEM grid.Single core-shell nanocrystals (PbTe/CdTe)

Figure 1: (left) CdSe size series under UV excitation , (middle) ordered monolayer of PbS nanocrystals on a substrateand (right) high-resolution TEM image of single core/shell PbTe/CdTe nanocrystal. 

In our group, we focus on colloidal nanocrystals: nanometer sized (2-20 nm) pieces of crystalline material that make a colloidal dispersion in the appropriate solvent. Over the past twenty years, the synthesis of these materials has made tremendous progress, allowing us to use a wide range of metal, metal-oxide and semiconductors to fabricate nanostructures with varying size and shape. This is not only interesting from a chemistry point of view (how do you create this range of structures ?) but is also very relevant for real-life applications of the colloids. Such applications range from photodetection (solar cells, IR cameras, ..) to lighting (LEDs, remote phosphors) to integrated photonics (lasers, switches, sources, modulators, ...). A key element is the combination of the different nanocrystals into a 'nanocrystal solid' , much alike building a Lego structure out of small plastic blocks ! These solids posses new (collective) properties (e.g. enhanced absorption) resulting from interactions between he nanocrystals that built them !

Research in colloidal nanocrystals is chemistry. But it's also Applied Physics. And once in a while it's more biochemistry. But it's always exciting and it's long but finished ! So explore our research and that of our collaborators and join us in the exciting world of nanoscience, today !