التشخيص العملي والنظري لخصائص التراكيب النانوية لكبريتيد الزنك

Experimental and Theoretical Investigations of Zinc Sulfide Nanostructur Features

Zinc sulfide nanoparticles were prepared successfully using the chemical precipitation method. The growth process of ZnS nanoparticles was controlled by optimizing parameters such as the reaction time, the concentration of starting materials, the reaction temperature, and the pH of the solution. The formation of zinc sulfide nanoparticles in the absent and presence of PEG4000 was confirmed through Field emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier transform infrared (FT-IR), X-Ray Diffraction (XRD), and Transmission Electron Microscopy(TEM). The UV-visible spectrum was used to estimate the band gap energy and it turned out to be 4.2 eV and 4.5 eV for both uncapped ZnS and PEG-capped ZnS nanoparticles, respectively. Suggesting, the effect of quantum confinement which is believed to appear as the particle’s size gets smaller. The optical properties of the prepared nanomaterials covered with the polymer and not covered were also studied, and then the theoretical part of this work was moved using the special program GaussianView 6.0 Gaussian 09W Chem Draw professional 15.0, and linking the results of the practical part with the theoretical one. Molecular geometry structures were accurately optimized to low convergence energy thresholds for the Zn3S3 cluster before and after adding Polyethylene Glycol (PEG4000). Density functional theory DFT/ B3LYP calculations with 6-113G (d, p) basis set were employed to investigate structural and electronic properties of Zn3S3-PEG4000 composite. Complete vibrational modes frequencies were systematically analyzed on the distribution basis of potential energy. An agreement of FTIR spectra of titled molecules was evaluated between experimental and theoretical findings of the active peaks of O–H, C–H, C=O, C–O–C and Zn–S functional groups. Frontier high occupied and low unoccupied molecular orbitals (HOMO&LUMO) were calculated and plotted to obtain the energy gap (E𝒈) resulting from the difference between those orbitals. The promising indicator was obtained at increasing E𝒈 from (4.031 to 4.459) eV after adding PEG4000, pointing out the effect of polymer on the ZnS surface as a capping agent. Additionally, electronic features of mentioned structures such as: Ionization potential (IP), Fermi energy level (Ef), Electron affinity (EA), Ef, Energy Gap (𝑬𝒈), Chemical Potential (𝑪𝒑), Electronegativity (χ), Global Hardness (η), Chemical Softness (S), Electrophilicity (𝛚) and Nucleophilicity (ε), were calculated in addition to the molecular electrostatic potential isosurface and contour diagram of Zn3S3 and Zn3S3_PEG4000