Physico-Chemical Nanomaterials Science

Synthesis from aqueous solutions and optical properties 
of Ag–In–S quantum dots
Lopushanska B.V.1, Azhniuk Yu.M.1,2, Lopushansky V.V.2, Molnar Sh.B.1, 
Studenyak I.P.1, Selyshchev O.3, Zahn D.R.T.3 
1 Uzhhorod National University, 46 Pidhirna Str., 88000, Uzhhorod, Ukraine
E-mail: yu.azhniuk@gmail.com 
2 Institute of Electron Physics, Ukr. Nat. Acad. Sci., 21 Universytetska Str., 88017, Uzhhorod, Ukraine
3 Semiconductor Physics, Chemnitz University of Technology, Chemnitz, Germany
In recent years, stoichiometric and non-stoichiometric semiconductor quantum dots (QDs) of I–III–VI compounds have become an object of intense scientific interest due to the possibilities of broad variation of their bandgap with size and composition, high luminescence efficiency, and mild synthesis conditions with non-toxic components being employed [1]. Here we report on size-selected non-stoichiometric Ag–In–S QDs and Ag–In–S/ZnS core/shell nanoparticles synthesised from AgNO3, InCl3, and Na2S aqueous solutions in the presence of mercaptoacetic acid (MAA). ZnS shells were formed by addition of zinc acetate and MAA at the second stage of reaction. The nanoparticle size selection was performed by repeated rotary fractioning of the colloidal solutions at 4000 rpm with a non-solvent as described earlier [1].
The colloidal solutions of the Ag–In–S and Ag–In–S/ZnS QDs obtained as well as the QDs embedded in gelatine films were characterised by optical absorption (Cary 50), photoluminescence (Shimadzu RF–6000), and Raman (LabRAM, exc = 325 nm) spectroscopy. The optical absorption edge and photoluminescence maxima exhibit a clear size-dependent shift. The effect of the [Ag+]:[In3+]:[S2–] component ratio as well as of the ZnS shell on the optical properties of the QDs obtained is discussed.  

1.	Raevskaya A., Lesnyak V., Haubold D., Dzhagan V., Stroyuk O., Gaponik N., Zahn D.R.T., Eychmüller A. A fine size selection of brightly luminescent water-soluble Ag−In−S and Ag−In−S/ZnS quantum dots // J. Phys. Chem. C – 2017. – 121. – P. 9032–9042.