The Nann group has worked on a variety of quantum dots over the years: ranging from toxic cadmium chalcogenides to more benign copper indium disulphide and indium phosphide quantum dots.
Quantum dots are nanocrystals made out of semiconductor materials, grown at such small
sizes that they become electronically confined in all three spatial dimensions.
This causes the crystals to become fluorescent when they are excited by absorbed light,
and that confined electrical energy can be harnessed to drive a number of
interesting photochemical devices.
While using fluorescent materials as light harvesters (i.e. dye-sensitized solar cells) is
not new, quantum dots allow for these devices to have much longer lifetimes, as they
don’t bleach over time like dyes. These materials also display size-dependent emission:
the smaller the size of the crystal, the greater the electronic confinement, and the higher
the energy of emission.
This allows for the materials to be tuneable for specific energies – something advantageous
to our work in energy storage catalysis. By changing the size, we can change the placement of the conduction band edge and therefore select for specific reaction potentials. In this way one material, such as indium phosphide, could be used to promote water splitting, CO2 reduction, or to improve solar and fuel cell efficiencies.