Highly fluorescent and color tunable AgInS 2 (AIS) and (AgInS 2 )x(ZnS) 1-x (AIZS) quantum dots (QDs) were prepared via a facile aqueous-phase synthesis using AgNO 3 , In(NO 3 ) 3 , Zn(OAc) 2 and Na 2 S as precursors and 3-mercaptopropionic acid (3-MPA) as ligand. Produced AIZS QDs exhibit a small diameter (ca. 2.1 nm) and a cubic structure. Ag-3-MPA and In-3-MPA complexes formed during the preparation of AIS cores were found to play a key role on the fate of the reaction and an atypical blue-shift of the PL emission was observed with the increase of the Ag/In ratio. The photoluminescence quantum yield (PL QY) of AIS QDs is modest but increased markedly after the alloying and shelling with ZnS (up to 65%). Size and composition-selective precipitations allowed to separate up to 13 fractions of AIZS QDs with exceptionally high PL QYs (up to 78%), which is the highest value reported to date for AIZS QDs prepared in aqueous phase. These high PL QYs combined to their good colloidal stability and photostability make AIZS QDs of high potential as cadmium-free fluorescent probes for various applications like bio-imaging or sensing.

The effects of the zinc salt precursors, the reaction temperature and the alkaline ratio b (b = [OH-]/[Zn 2+ ]) on the aqueous synthesis of ZnO nanocrystals were investigated. Depending on the type of the zinc precursor, Zn 5 (OH) 8 Cl 2 ·H 2 O or Zn 5 (OH) 8 (NO 3 ) 2 .2H 2 O lamellar phases were obtained at room temperature (20°C) when the alkaline ratio is lower (0.5 £ b £ 1, 6 £ pH £ 6.4). When the reaction temperature increased to 95°C, zinc hydroxide chloride monohydrate was obtained in one case whereas zinc oxide was formed in the other, and no lamellar phase of Zn 5 (OH) 8 (NO 3 ) 2 .2H 2 O was obtained. Thermal decomposition of the two lamellar phases was carried out and mainly showed that Zn 5 (OH) 8 (NO 3 ) 2 .2H 2 O was completely decomposed to ZnO when the annealed temperature reached~250°C while Zn 5 (OH) 8 Cl 2 ·H 2 O was totally transformed to ZnO at about 400°C, a higher comparative temperature that confirms the better thermal stability of the zinc hydroxide chloride monohydrate. Figure 8 FTIR spectra of lamellar phases: (A) CLP: at room temperature, (a) CLP after annealing up to 400°C. (B) NLP: at room temperature, (a) NLP after annealing up to 250 °C.

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