Modified graphene quantum dots-zinc oxide nanocomposites for photocatalytic degradation of organic dyes and commercial herbicide

Abstract

The high crystallinity of graphene quantum dots-ZnO nanocomposites is considered to have a significant effect in improving the carrier lifetime for enhanced photocatalytic degradation. The graphene quantum dots-ZnO nanocomposites were synthesized by adding graphene quantum dots solution into starting precursors during the precipitation. Characterization was performed using various techniques. High crystallinity of graphene quantum dots-ZnO nanocomposites is obtained in terms of increased crystal size and decreased dislocation density. The improved crystallinity increases the carrier lifetime on the material surface for the functional improvement of photocatalytic material. Photocatalytic test of methylene blue and methyl orange was performed under UV irradiation. Degradation rate constant reaches the maximum value for both organic dyes for the appropriate preparing condition of graphene quantum dots-ZnO nanocomposites. The graphene quantum dots-ZnO nanocomposites were then applied to degrade commercial glyphosate herbicide contaminants for an agricultural wastewater treatment investigation. The investigation aims to demonstrate a facile useful way of herbicide contaminant reduction for the better health of farmers. The graphene quantum dots-ZnO nanocomposites show an enhancement of the photocatalytic process with improved degradation rate constant (23% increased) in comparison to pure ZnO. Therefore, this work demonstrates that graphene quantum dots-ZnO nanocomposites can be used as a photocatalytic material for degrading organic dyes and commercial herbicide contaminants owing to its low-cost and environmental-friendly properties.

High Visual Colorimetric Determination of F‐ Ions by Exploiting the Inhibition of Oxidase Mimicking Activity of FeMnO4@GQD Nanocomposite

“…High dislocation density may cause difficulties in carrier movement, resulting in carrier recombination in crystal [45] . On the other hand, low dislocation density will offer a facile situation of carrier movement in crystals [46] . The effect is considered a good parameter to improve the carrier life time at the nanocomposite surface for better photocatalytic application.…”

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“…( 5) [14]. αhν = A(hν − E g ) n (5) where α and A are constants, h is the Plank's constant,  is the frequency, and n is ½ for direct band gap semiconductors as for ZnO. For E g estimation, an extrapolation from the linear part up to the h-axis was fitted.…”

“…To improve the photocatalytic activity of ZnO, it has been demonstrated with several improvements in charge separations, lifetimes, and surface areas. Phopayu et al modified ZnO by using graphene quantum dots (GQDs) doping for extending the crystalline structure of the GQDs-ZnO nanocomposites [5]. The extended structure has reducing grain boundary density, thus causing a lower electron-hole pair recombination at the grain boundary.…”

Chemical waste and allied products

“…The findings suggest that a very high concentration of 5,000 and 60,000 mg/L COD may be found in stormwater runoff and silage discharges, respectively. The starting precursors were first added in the synthesis of the graphene quantum dots-ZnO nanocomposites with the graphene quantum dots solution (Phophayu, Pimpang, Wongrerkdee, Sujinnapram, & Wongrerkdee, 2020). The synthesis was performed during the process of precipitation.…”

“…The starting precursors were first added in the synthesis of the graphene quantum dots‐ZnO nanocomposites with the graphene quantum dots solution (Phophayu, Pimpang, Wongrerkdee, Sujinnapram, & Wongrerkdee, 2020). The synthesis was performed during the process of precipitation.…”