Effect of Al and Mg Doping on Optical Properties of ZnO Thin Films Prepared by Spin Coating

This paper investigated the influence of aluminum and magnesium doping on the optical and electrical properties of zinc oxide (ZnO) thin films for solar cell application. zinc acetate dehydrates was used as starting material. Aluminum chloride and tin chloride were added to each solution to serve as dopants. X-ray diffractions were analyzed by X-ray diffraction (XRD) which revealed crystalline and hexagonal wurtzite structure. All the films showed more than 80% transparency in the visible region. The optical band gap of undoped znO thin film was found to be 3.12ev while that of Al-doped and Mg-doped znO film was estimated to be 3.16eV and 3.26eV respectively. The resistivity of the films measured were 2.51×10–4Ω cm for Al-doped, 2.53×10–4Ω cm for mg-doped and 2.61×10-4Ω cm for undoped znO respectively. The quality of the films deposited in this work is a promising window layer component of a solar cell. The variation in the band gap observed in this work could be explained by Burstein–Moss effect which was fully explained in the discussion section of this work

Analysis of Heavy Metals in Soils around a Scrap Metal Recycling Company in Ile-Ife, Osun State, Southwestern Nigeria

Contamination of soils by heavy metals has severely increased over the last few decades due to industrial wastes and human activities. Contaminated soils can constitute sources of health hazard to humans globally. However, there is paucity of information on the level of heavy metal concentration in the study area. This study therefore made a pioneering effort in investigating the concentration of selected heavy metals (Cd, Cu, Pb, Zn and Fe) in soils around a scrap metal recycling company in Ile-Ife, Osun State, Nigeria. Thirty soil samples and solid wastes were collected from four sides of the scrap metal recycling company. The samples were air-dried, digested using standard method and analyzed for the selected heavy metals using a flame atomic absorption spectrometer. Results of the Atomic Absorption Spectrophotometric (AAS) analysis revealed that for heavy metals, the concentrations in the soils were below the background levels and permissible limits recommended for soils in some countries. The value of the mean concentration of the analyzed heavy metals in the soils around the scrap metal recycling company ranged from 0.0040 – 0.0140 mg/kg for Cd, 0.061 – 0.108 mg/kg for Fe, 0.037 – 0.047 mg/kg for Cu, 0.003 – 0.0064 mg/kg for Pb and 0.019 – 0.121 mg/kg for Zn. The results from the study indicated that the concentrations of heavy metals around the scrap metal recycling company did not appear to be of serious concern. The concentrations of all the heavy metals were below the background level proposed by the World Health Organization (WHO) residential soil standards. Keywords: Heavy metals, Contamination, Scrap metals, Recycling factory, Atomic Absorption Spectrometry (AAS