Electrical properties and aquatic ecotoxicity effects of ZnS nanocrystals

Abstract

A new synthesis method of ZnS colloidal nanocrystals is presented in this work, and this novel approach allows one to produce Zinc sulfide nanocrystals owing to a modified polyol process that makes use of 1.3-propanediol as a solvent. The structure and morphology of the nanoparticles were characterized by high-resolution transmission electron microscopy, transmission electron microscopy, X-ray diffraction and spectroscopy photoluminescence. The results showed that quasi-spherical ZnS nanocrystals with sizes in the range 3–5 nm were formed. Their morphology, size and colloidal stability are driven by the polyol solvent. Under UV excitation, a strong visible PL emission, due to the radiative recombinations of the electron–hole pairs photo-generated in the ZnS nanoparticles, was observed. In order to study the environmental risk of ZnS, mussels Mytilus galloprovincialis were exposed to ZnS C1 $$=$$ 0.1 mg/L, ZnS C2 $$=$$ 1 mg/L and ZnS C3 $$=$$ 10 mg/L. Superoxide dismutase, catalase activities and protein thiols density were determined in the gill of treated and untreated mussels. No significant effects were detected in the gills of exposed mussels after 14 days of exposure compared to control. Optical property of the new nanomaterial, together with the easy synthesis process, makes the ZnS nanocrystals a promising candidate for applications optoelectronics and photocatalyst. The frequency-dependent impedance and AC conductivity have been investigated in this context. Impedance and modulus plane plots from 10 to $$10^{7}$$ Hz show the presence of bulk and grain boundary phases in ZnS at each measurement temperature from 125 to $$225\,^{\circ }\hbox {C}$$ . The activation energy was calculated from the temperature variation of DC conductivity. Studies of frequency and temperature dependence of electrical data of the compound suggest that conduction process in the material is thermally activated. Environmental risk assessment results constitute a scientific support for considering the use of this nonmaterial on various applications after further complementary studies in order to ensure the safety of these NPs.