The experimental determination of composition-dependent molar extinction coefficient of nonstoichiometric Zn–Cu–In–S nanocrystals

In this study, the different compositions of Zn–Cu–In–S quantum dots (ZCIS QDs) were prepared by a facile synthetic approach. The compositions and particle sizes of ZCIS nanocrystals were precisely controlled. The composition-dependent molar extinction coefficient of nonstoichiometric ZCIS QDs has been determined by combination of ICP-MS with UV–vis absorption and TEM. The molar extinction coefficient values were found to comply with a power function with exponents of 3.6 and 1.8 with the variation of the content of Cu or Zn, respectively. The extinction coefficient of ZCIS QDs exhibited the composition dependency and seemed to be larger than that of CuInS2 for a given size. The determination of the extinction coefficient makes it feasible to calculate the concentration of ZCIS QDs in solution and promotes its further applications in bioanalysis.