Double-shelling AgInS 2 nanocrystals with GaS x /ZnS to make them emit bright and stable excitonic luminescence.

This paper presents the successful synthesis of AgInS 2 nanocrystals (NCs) double-shelled with GaS x and ZnS for emitting bright and narrow excitonic luminescence from AgInS 2 core NCs. Additionally, the AgInS 2/ GaS x /ZnS NCs with a core/double-shell structure have demonstrated high chemical and photochemical stability. The AgInS 2/ GaS x /ZnS NCs were prepared via three steps: (i) synthesis of AgInS 2 core NCs by solvothermal method at 200 °C for 30 min, (ii) shelling GaS x on AgInS 2 core NCs at 280 °C for 60 min to produce the AgInS 2 /GaS x core/shell structure, and (iii) the outermost ZnS shelling at 140 °C for 10 min. The synthesized NCs were characterized in detail by using appropriate techniques such as x-ray diffraction, transmission electron microscopy, and optical spectroscopies. The luminescence evolution of the synthesized NCs is as follows: from the broad spectrum (peaking at 756 nm) of the AgInS 2 core NCs to become the narrow excitonic emission (at 575 nm) prominent beside the broad one after shelling with GaS x , then only the bright excitonic luminescence (at 575 nm) without broad emission after double-shelling with GaS x /ZnS. The double-shell has made the AgInS 2 /GaS x /ZnS NCs not only remarkably enhance their luminescence quantum yield (QY) up to ∼60% but also maintain the narrow excitonic emission stably for a long-term storage over 12 months. The outermost ZnS shell is believed to play a key role in enhancing QY and protecting AgInS 2 and AgInS 2 /GaS x from certain damage.