Synthesis of Cu2SnTe3 Nanocrystals. The Cu2SnTe3 nanoparticles with cubic
structure were prepared by the reaction of copper, tin salts with tellurium (IV) oxide
in the presence of OAm and DDT. In a typical synthesis, stoichiometric amounts of
Cu(II)(acac)2 (0.1 mmoL) and Ph4Sn (0.05 mmoL) in the presence of OAm (5.0 mL)
were added in a three-neck flask. The solution was magnetically stirred and heated to
130 °C for 30 min under an argon atmosphere to remove water and other low-boiling
point impurities. Meanwhile, a tellurium precursor solution was prepared by
dissolving TeO2 (1.5 mmoL) in 10 mL DDT in a three-neck flask under an argon
atmosphere, which was preheated to 110 °C for 60 min until the TeO2 completely
dissolved. After that, the Cu (I) and Sn (IV) complexes were heated to 210 °C. Then
the 1.0 mL Te-DDT solution was immediately injected into the above solution and the
reaction mixture was kept at 210 °C for 90 minutes with continuous stirring. The
reaction was allowed to cool to room temperature naturally. Finally, the product was
collected by centrifugation and washed several times with absolute ethanol and
toluene. The product obtained in this case was cubic phase Cu2SnTe3 nanoparticles
with nearly monodisperse and uniform size (see Figure S1).