250 C. A decrease in temperature of 20Β±30 C was observed. The solution was then allowed to stabilize at 250 C and was heated for 45 min at this temperature. The solution was cooled to approximately 70 C, and after an excess of methanol was added, a flocculant precipitate formed. The solid was separated by centrifugation, washed with methanol, and redispersed in toluene. The toluene was removed under a vacuum to give pale yellow TOPO-capped CuSe nanoparticles. The particles were washed three times with methanol and redissolved in toluene. Size-selective precipitation was then carried out on the particles to obtain four fractions of varying average particle size.
Preparation of CuInSe 2 Quantum Dots: TOPO (20 g) was heated to 100 C, followed by degassing and flushing with nitrogen. An equimolar solution of InCl 3 (2.20 g, 0.01 mol) and CuCl (1.0 g, 0.01 mol) in TOP (15 mL) was injected into the hot TOPO at 100 C. The colorless TOPO turned bright yellow after injection, and the temperature dropped to 80 C. The reaction was allowed to proceed for 1 h, after which the temperature was increased to 250 C, and then 1.0 M TOPSe (20 mL) was injected into the TOPO solution. After an initial drop in temperature to 220 C, the reaction was stabilized at 250 C and allowed to proceed for 24 h. The reaction mixture was cooled to 60 C, followed by the addition of excess methanol to flocculate the particles. There was no immediate visible precipitation on the addition of methanol. A fine precipitate did appear after stirring overnight and was separated by centrifugation. The precipitate was washed with methanol to remove the excess TOPO and then dissolved in toluene.