Cs:WO3 NCs were synthesized using standard Schlenk line techniques under inert atmosphere, as previously described. The synthesis involves the injection of tungsten oleate into a hot solution of cesium oleate at 300°C. The two metal oleates were prepared separately by the reaction of tungsten (IV) chloride or cesium chloride with oleic acid. After injection, the reaction was allowed to proceed for 10 minutes, then the dark blue mixture was cooled quickly to stop the reaction. The NCs were purified after synthesis by precipitating them out of the reaction mixture with isopropanol acting as an antisolvent. The NCs were centrifuged to separate the precipitated NC product and the supernatant was discarded. The mixture was redispersed in toluene and washed again by addition of antisolvent and subsequent centrifugation. The final NC colloid was prepared by redispersing the product in hexane with an approximate concentration of 20 mg/mL. The colloidal NC dispersion was concentrated to 50 mg/mL and used to spin-coat thin films on conductive, tin-doped indium oxide coated glass substrates at 1500 rpm.