Mn-doped Cu-Zn-In-S/ZnS nanocrystals: optical properties and their use as time-gated fluorescence probes

In this work, Mn-doped Cu-Zn-In-S/ZnS nanocrystals ((Mn:CZIS/ZnS NCs, 3~5 nm in sizes) were prepared by varying the Cu and Mn level in synthesis, and their optical properties including optical spectra and fluorescence lifetimes were investigated. It is found that with a certain range of the Cu or Mn level, the NCs present fluorescence peaks at around 605 nm, but their fluorescence lifetimes do be affected by the Cu or Mn level. Significant NC fluorescence red-shift and lifetime drop-off are observed when the Cu level reaches a much high level. The possible role of Cu and its interaction with Mn in NC fluorescence mechanisms were discussed. The use of Mn:CZIS/ZnS NCs as highly sensitive time-gated probes was demonstrated through a biotin-avidin assay.