Tunable near-infrared and visible-light transmittance in nanocrystal-in-glass composites

Glass windows let in light and keep out extreme heat and cold, but with the advance of the field of electrochromism the reversible change of optical transmittance in response to electrochemical charge and discharge they could do much more. Delia Milliron and co-workers have made a step towards producing windows that can greatly reduce lighting and heating costs with the demonstration of a composite film composed of tin-doped indium oxide nanocrystals embedded in a niobium oxide glass matrix. By varying an applied voltage over a 2.5-volt range, the charged nanocrystals selectively block near-infrared light, while the glass strongly modulates visible light owing to its reconstructed bonding near the nanocrystalglass interface. Practical 'smart windows' and other devices are still some way off, but this solution-processed nanocrystal-in-glass approach is modular and permits extensive tuning of structure and composition, and so provides a solid platform for further refinement.