Ag ₂ S Nanoparticles Evolved into Luminescent AgInS ₂ @In ₂ S ₃ Heteronanoparticles through Dual Formation Mechanism

A deep understanding of the growth kinetics and mechanism of metal sulfide nanostructure is helpful in preparing nanomaterials with controllable structures. This study reports a facile synthetic protocol for the luminescent AgInS2@In2S3 core@shell heteronanoparticles through the reaction of preformed Ag2S nanoparticles with excess [(C4H9)2NCS2]3In in dodecanethiol. A dual formation mechanism for the orthorhombic AgInS2 (o-AgInS2) component is proposed, that is, the cation exchange of partial Ag+ in Ag2S nanoparticle by In3+ to produce the metastable AgInS2 and alloying of the In2S3 formed through direct decomposition of [(C4H9)2NCS2]3In with Ag2S nanoparticles to produce AgInS2. Following the dual formation mechanism, the Ag2S nanoparticle first evolves into the intermediate Ag2−3δInδS/o-AgInS2 Janus heteronanoparticle without band-edge emission of o-AgInS2, then converts to the o-AgInS2 nanoparticle, and finally transforms to the o-AgInS2@In2S3 core@shell heteronanoparticle with band-edge emission of o-AgInS2. The appearance of band-edge emission might be attributed to the removal of the surface defects of the o-AgInS2 core by coating the In2S3 shell. This study would provide a facile protocol for the synthesis of IB-IIIA-VIA2 nanomaterials with controlled architecture and benefit the development of monochromatic luminescent apparatus.