Synthesis, spectral and thermal studies of pyridyl adducts of Zn(II) and Cd(II) dithiocarbamates, and their use as single source precursors for ZnS and CdS nanoparticles

The synthesis, spectroscopic characterisation, and thermal studies of pyridyl adducts of Zn(II) and Cd(II) complexes of N-ethyl-N-phenyl dithiocarbamate, represented as [ZnL2py] and [CdL2py2], are reported. Single-crystal X-ray structural analysis of the Zn compound showed that it is five-coordinate with four sulphurs from dithiocarbamate and one nitrogen from pyridine in a distorted square pyramidal geometry. The thermogravimetric studies indicate that the zinc and cadmium compounds undergo fast weight loss, and the temperature at maximum rate of decomposition is at 277 °C and 265 °C respectively, to give the metal (Zn or Cd) sulphide residues. These compounds were used as single molecule precursors to produce nanocrystalline MS (M = Zn, Cd) after thermolysis in hexadecylamine. The morphological and optical properties of the resulting MS nanocrystallites were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis absorption and photoluminescence (PL) spectroscopy, and powdered X-ray diffraction (XRD). By varying the growth time, the temporal evolution of the optical properties and morphology of the nanocrystals were investigated.National Research Foundation (NRF), South Africa, and North-West University, Potchefstroom, South Afric

Electric and Dielectric Properties of Au/ZnS-PVA/n-Si (MPS) Structures in the Frequency Range of 10-200 kHz

WOS: 000403016800064Pure polyvinyl alcohol (PVA) capped ZnS semiconductor nanocrystals were prepared by microwave-assisted method, and the optical and structural properties of the as-prepared materials were characterized by x-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) techniques. The XRD pattern shows the formation of ZnS nanocrystals, and the UV-Vis spectroscopy results show a blue shift of about 1.2 eV in its band gap due to the confinement of very small nanostructures. The concentration of donor atoms (N (D)), diffusion potential (V (D)), Fermi energy level (E (F)), and barrier height (I broken vertical bar(B) (C-V)) values were obtained from the reverse bias C (-2)-V plots for each frequency. The voltage dependent profile of series resistance (R (s)) and surface states (N (ss)) were also obtained using admittance and low-high frequency methods, respectively. R (s)-V and N (ss)-V plots both have distinctive peaks in the depletion region due to the spatial distribution charge at the surface states. The effect of R (s) and interfacial layer on the C-V and G/omega-V characteristics was found remarkable at high frequencies. Therefore, the high frequency C-V and G/omega-V plots were corrected to eliminate the effect of R (s). The real and imaginary parts of dielectric constant (epsilon' and epsilon aEuro(3)) and electric modulus (M' and MaEuro(3)), loss tangent (tan delta), and ac electrical conductivity (sigma (ac)) were also obtained using C and G/omega data and it was found that these parameters are indeed strong functions of frequency and applied bias voltage. Experimental results confirmed that the N (ss), R (s) , and interfacial layer of the MPS structure are important parameters that strongly influence both the electrical and dielectric properties. The low values of N (ss) (similar to 10(9) eV(-1) cm(-2)) and the value of dielectric constant (epsilon' = 1.3) of ZnS-PVA interfacial layer even at 10 kHz are very suitable for electronic devices when compared with the SiO2. These results confirmed that the ZnS-PVA considerably improves the performance of Au/n-Si (MS) structure and also allow it to work as a capacitor, which stores electric charges or energy