Metal quantum dots are produced from a solution of the metal salt when the solution is passed through an electrostatic capillary nozzle (3) into a chamber (7). The nozzle (3) produces an aerosol of droplets (4) of the solution which is then irradiated using laser light (8). The solution evaporates from the droplets to form quantum dots of the metal element on a substrate 5 in the chamber 7.