Erbium-doped nanoparticles/films for enhancing percentage photodegradation of direct red-31 dye

Abstract

Nowadays, the demand for synthetic dyes has grown manifold as there are being widely used in leather, textile, food industries. This paper reports Erbium doped ZnO nanostructured films were deposited on to the glass substrate by a sol–gel spin coating technique. Atomic weight percentage of Erbium was varied from 2.0, 2.5, 3.0, and 3.5 at.wt% namely EZ-1, EZ-2, EZ-3 and EZ-4 and the film characterization were carried out by means of X-Ray diffraction, FESEM, UV–Vis spectrophotometer, Raman spectroscopy, LCR and photoluminescence measurements. XRD result revealed the existence of Er2O3 and ZnO phases for varied Er concentration. FESEM reveals rod-shaped morphology of the film of the order of the size of 40–75 nm. Absorbance and optical band gap was obtained from UV–Vis spectrophotometer. This revealed optical band gap widening with a molar ratio in the range of 3.26–3.32 eV. Raman spectroscopy indicates the tensile stress in Er-doped ZnO films. Photoluminescence intensity near 594 nm indicates more oxygen vacancies which led to high photocatalytic performance. The prepared films were used for photodegradation of DR-31 dye. From the photocatalytic experiment, the degradation percentage was increased with increase in Er concentration up to a molar ratio of 3.0 at.wt%. Thus the optimum molar ratio of the prepared films (3.0 at.wt%) exhibits almost complete degradation of DR-31 dye only in 48 min under UV illumination. The kinetic study reveals the rate constant of nanospheres like particles is 0.07428 min−1. The Er-doped films with different molar ratio result in almost same photocatalytic performance after regular interval of the time. The comparative study of nanoparticles with the film will make for photodegradation of DR-31 dye under same experimental conditions. Despite kinetic study of prepared films were better as compared to bulk form (powder) but the percentage degradation of nanoparticles was found to be better than films.