Graphene quantum dots functionalized Ce-ZnO nanofibers with enriched oxygen vacancy sites morphology to improve the efficiency of selective electrochemical detection of Hg (II)

Abstract

Herein, GQD functionalized Ce-ZnO hybrid nanofibers (GQD/Ce-ZnO NFs) towards selective Hg2+ ion detection through DPV technique was investigated. The hybrid NFs were synthesized via a facile electrospinning process and their physical properties were investigated through XRD, SEM-EDS, HR-TEM with SAED pattern, XPS, UV-DRS, and ESR techniques. Notably, the plane value, phase recognition, and purity of the GQD/Ce-ZnO NFs were examined through XRD analysis. The chemical states, chemical composition, and weight percentage of the elements were examined by the XPS and EDS analysis. Similarly, the width of the hybrid NFs and structural morphology were elucidated through SEM and HR-TEM analysis. The existence of oxygen vacancies (vo) was verified using UV-DRS and ESR techniques. The electrochemical characteristics of GQD/Ce-ZnO NFs-modified glassy carbon electrode (GCE) was investigated using diverse electrochemical methodologies like cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Remarkably, DPV studies depict that GQD/Ce-ZnO NFs modified GCE achieved high anodic peak current 3.48 × 10−4 A upon successive addition of Hg2+ (0.1–100 μM). The anodic peak current was directly proportional to the mercury ions concentration throughout a wide range of 0.1 × 10−6 to 100 × 10−6 M with a LOD of 267 nM in an optimized experimental condition. The GQD/Ce-ZnO NFs modified GCE showed remarkable reproducibility, with an RSD value of 1.81 %. Additionally, it maintained a strong current retention rate of 71.5 % over 12 days, indicating commendable long-term stability.