Physico-Chemical nanomaterials science

Synthesis of (Zn,Cd)xMn1-xS nanoparticles 
by an ion-exchange reaction  

Pylypko V.G.1, Krupko O.V.2, Shcherbak L.P.1
1Yuriy Fedkovych Chernivtsi National University, Kotsjubynskyi Str., 2, Chernivtsi  58012, Ukraine
2Bukovinian State Medical University, Theatralna sq., 2, Chernivtsi-58002, Ukraine
 E-mail: sunny_vik@ukr.net

Nanostructures of wide band-gap semiconductors MnS, ZnS and CdS have numerous potential applications in nano-electronics and nano-optoelectronics devices [1]. The continuous interest in the (Zn, Mn) and (Cd, Mn) chalcogenides as typical diluted magnetic semiconductors has also attracted attention to these mixed crystals. 
In this paper, we compare optical and structural properties of colloidal solutions obtained by introduction of certain content of Zn2+ (or Cd2+)-ions onto/into MnS/L-cysteine  nanoparticles  (NP) prepared at identical synthesis conditions. Initial Mn2+ and S2--ions molar ratio was 0,4:0,36; the doping impurity was introduced in the MnS/L-cys colloidal solution in the [Mn2+]:[Zn2+] (or [Cd2+]) ratio equal 1 : 0,1.  Besides, similar quantities of Mn2+ and Zn2+ (or Cd2+) ions and L-cysteine were used for co-precipitation of Mn, Zn (Cd) sulfides at the same pH value. 
Absorption and photoluminescence (PL) spectra were measured at room temperature by the Ocean Optics USB-2000 spectrophotometer.
It was concluded that the products’ composition is strongly pH-dependent. According to the initial bimodal absorption spectra data, both ZnS and CdS NPs formed in the MnS/L-cys–Zn2+ (Cd2+) system, probably, as core/shell structure followed by the transformation into mixed ZnxMn1-xS/L-cys or CdxMn1-xS/L-cys nanoparticles. The transformation occurs faster in MnS/L-cys–Cd2+ relatively to MnS/L-cys–Zn2+ system. Meanwhile ion-exchange by Zn2+-ions resulted in more intensive PL. 
Formation initially of two sulfides (minor ZnS/L-cys or CdS/L-cys and major MnS/L-cys) occurs during the co-precipitation process however PL spectra indicate similar picture for the obtained by both methods mixed nanoparticles after ripening during few hours. 
1.	Himadri B. Bohidar  and Kamla Rawat. Design of nanostructures: self-assembly of nanomaterials. Chapter 8. Metal Sulfide Nanoparticles. Wiley VCH. 2017.