Systematic synthesis of different-sized AgInS2/GaSx nanocrystals for emitting the strong and narrow excitonic luminescence

This paper presents for the first time the systematic synthesis of AgInS2 (AIS) nanocrystals (NCs) with different sizes of 2.6 - 6.8 nm just by controlling only the reaction temperature. The synthesis of AIS core NCs was carried out in 2 steps: (i) synthesis of Ag2S NCs and then (ii) partial exchange of Ag+ with In3+ in the template Ag2S NCs. For step (i), Ag2S NCs of different sizes were synthesized by reaction of the Ag and S precursors at different temperatures of 30 oC to 130 oC, for the same reaction time of 30 min. For step (ii), AIS NCs were created by the exchange of Ag+ with In3+ at 120 oC for 60 min. Finally, GaSx was shelled on AIS core NCs to produce the AgInS2/GaSx core/shell structures. The synthesized AIS/GaSx NCs demonstrate the clear excitonic absorptions and strong, narrow excitonic luminescence peaking at 530 - 606 nm depending on the size of AIS core NCs.