Matrix Method of Determining Optical Energy Bandgap of Natural Dye Extracts

Abstract

In this paper, a total of fourteen dye extracts from different plants’ parts (flowers and fruits) were extracted. Absorbance of light by dye extracts with 5%, 10% and 20%concentrationsweremeasured using a UV-Vis spectrophotometer at different wavelengths. A system of linear equations in terms of wavelength and absorbance without film thickness was developed and solved using MATLAB software. Also, optical energy bandgap (E_g) obtained experimentally are at range of 1.77- 2.76 eV. From the solutions of the system of equations, the (E_g) of the natural dyes were obtained. The results show all the dye extracts have (E_g) in the range 1.34-2.09 eV which falls within the range of UV and IR portions of the electromagnetic spectrum. Also, the results reveal that sunflower (Helianthus) dye has the smallest (E_g) of 1.34 eV and guava (Guajava) peel dye with the higher (E_g) of 2.09 eV. This means Helianthus dye absorbs more light over a wider part of the electromagnetic spectrum and the easier electron transfer from its valence band to the conduction band. The values obtained via matrix method are in agreement with the experimental values with slight deviation, hence this validates the matrix method of obtaining optical energy bandgaps.