Physico-Chemical nanomaterials science 

The influence of carboxyl-containing ligands on the preparation and optical properties of MnS nanoparticles

Pylypko V.G. and Shcherbak  L. P.
Yuriy Fedkovych Chernivtsi National University,
Kotsyubinsky str., 2, Chernivtsi-58012, Ukraine.
E-mail: v.pylypko@chnu.edu.ua

        As typical wide-band semiconductor nanosized MnS attracted interest for the potential applications in the fields of short wavelength optoelectronics and lithium ion batteries, as a photoluminescent component, and contrast agent for magnetic resonance imaging in biology and medicine [1]. Aminoacid L-cysteine used often as capping agent or sulfur source even in MnS nanoparticles (NPs) synthesis. It is considered usually that thiol groups of the cysteine molecules bind to the surfaces of the initial formed the MnS NPs demonstrating a capping action. 
Herein, we present results of comparing investigation of three possible stabilizers action for MnS NPs synthesized at the same thermodynamic conditions. Namely, we choosed two SH-containing acids (L-cysteine HO2CCH(NH2)CH2SH and thioglycolic acid (TGA) HSCH2CO2H) and SH-free citrate trianion C3H5O(COO)3−.
Manganese chloride tetrahydrate MnCl2*4H2O, L-cysteine, TGA, Trisodium citrate dihydrate Na3C6H5O7*2H2O and Sodium sulfide Na2S*9H2O of high chemical grade were used for the synthesis. Mn-ions: stabilizer: sulfide-ions molar ratio was fixed as 1:2:2 at 0.05 M the MnCl2 stock solution. All syntheses were performed simultaneously.
Pink-peach MnS/L-Cys, peach MnS/Citrate and greenish MnS/TGA precipitates were filtered and analyzed by EDX. All specimens contained Mn and S that confirmed formation the MnS NPs effectively capped by carboxylate-group of the citrate-ions. Extracted by isopropanol from the filtrates the NPs demonstrated high photoluminescence especially in the MnS/L-Cys case. 
Absorbance spectra of all aqua solutions are multimodal probably due to various MnS NPs crystallographic form creations. According to the absorbance spectra data the smallest particles formed in the citrate-ions presence and the largest in L-Cys one at the same the synthesis time. 
 
1.	Ferretti A. M., Mondini S., and Ponti A. Manganese Sulfide (MnS) Nanocrystals: Synthesis, Properties, and Applications // Advances in Colloid Science. (2016). doi:10.5772/65092 .