CdxHg(1−x)Te Alloy Colloidal Quantum Dots: Tuning Optical Properties from the Visible to Near-Infrared by Ion Exchange

The energy gap between valence and conduction levels in colloidal semiconductor quantum dots can be tuned via the nanoparticle diameter when this is comparable to or less than the Bohr radius. In materials such as cadmium mercury telluride, which readily forms a single phase ternary alloy, this quantum confi nement tuning can also be augmented by compositional tuning, which brings a further degree of freedom in the bandgap engineering. Here it is shown that compositional control of 2.3 nm diameter Cd x Hg (1− x ) Te nano crystals by exchange of Hg 2+ in place of Cd 2+ ions can be used to tune their optical properties across a technologically useful range, from 500 nm to almost 1200 nm. Data on composition-dependent changes in the optical properties are provided, including bandgap, extinction coeffi cient, emission energy and spectral shape, Stokes shift, quantum effi ciency, and radiative lifetimes as the exchange process occurs, which are highly relevant for those seeking to use these technologically important QD materials.