A purposefully engineered bimetallic graphene oxide nanosphere composite for visible light-driven eradication of organic fluorescent dyes†

Abstract

Water pollution of natural water sources has been rapidly augmented because of the continuous discharge of wastewater as a result of industrial globalization. However, conventional tools and technologies for wastewater treatment are insufficient to remediate the pollutants. Thus, we devised a simple and efficient neodymium-doped zinc sulfide (ZnS)-anchored graphene oxide (GO) nanosphere (Nd@ZnS:GO-NS) composite via co-precipitation and sonochemical techniques. Nd@ZnS:GO-NSs were tailored via surface charge-induced strained wrapping phenomenon by rolling up of annealed GO nanosheets, and the diameters were mostly in the range of 50–200 nm. These Nd@ZnS:GO-NSs were employed for the photodegradation of the cationic organic dyes (CODs) methyl orange (MO) and Coomassie brilliant blue red (BBR). Complete (100%) photodegradation of MO and BBR was observed with Nd@ZnS (3.50 h and 3.00 h, respectively) and Nd@ZnS:GO-NSs (180 min and 80 min, respectively). Optimized conditions of pH = 8, COD dosage = 20 mgL⁻¹, and Nd@ZnS:GO-NS dosage = 20 mg showed excellent degradation activities. Although both Nd@ZnS and Nd@ZnS:GO-NSs served as photocatalysts, among them, Nd@ZnS:GO-NSs showed excellent photosensor activities owing to their fast charge mobility, superior electronic conductivity, and improved surface activity, supplementing the role of 2D-GO in multicyclic reusability. Moreover, the negative (e⁻) hole pairs generated from Nd@ZnS:GO-NSs interfaced for a longer time with MO dye (with a stronger azo (–NN–) group and one SO₃⁻ group) than with BBR dye (with two SO₃⁻ groups and a quaternary nitrogen (N⁺–) group). Nd@ZnS:GO-NSs may open up new opportunities for the rational construction of effective photocatalysts for fundamental research and other applications. This strategic bifurcation of nanomaterials can be extended to doping with other nanomaterials, thereby advancing the development of nanostructures to the next level.