Shape and stoichiometry control of bismuth selenide nanocrystals in colloidal synthesis

Three kinds of Bi-Se nanocrystals (Bi2Se3, Bi8Se9 and Bi1.007Se0.993) have been synthesized via a hot-injection approach. The colloid morphology, from hexagonal to octahedron, strongly depends on the injection temperature. The growth mechanism of Bi-Se nanocrystals is revealed here. A higher temperature could cause the reduction reaction from Bi3+ to Bi, and accelerate the reaction speed of Bi-Se, thus causing a difference of monomer concentration in bulk solution, which impacts the shapes of bismuth selenide nanocrystals as well as the composition. The three Bi-Se nanocrystals also show different optical and photoelectrocatalyst performance.