Fluorescence Quenching and Highly Selective Adsorption of Ag⁺ Using N-Doped Graphene Quantum Dots/Poly(vinyl alcohol) Composite Membrane

Abstract

Fabrication of composite adsorbents with exceptional fluorescence performance has attracted increasing attention. In this study, a nitrogen-doped graphene quantum dots (NGQDs)/poly(vinyl alcohol) (PVA) composite membrane (NGQDs-PVA) with high adsorption selectivity and fluorescence quenching for Ag + was prepared via simple cross-linking. The SEM characterization showed that the NGQDs were uniformly distributed in PVA, indicating that the material exhibited fluorescence characteristics of quantum dots. C−O, −COOH, −NH 2 , and −OH functional groups in NGQDs-PVA complexed with a great amount of Ag + , and −NH− reduced a small amount of Ag + to Ag 0 . The pseudo-firstorder kinetic and Langmuir models were used to describe the adsorption process of heavy metals using the composite. The maximum adsorption capacity was 317.35 mg/g (Langmuir model fitting, pH = 4, T = 40 °C). When the fluorescence of NGQDs-PVA was quenched as the number of Ag + adsorbed increased, the change in fluorescence intensity was used to qualitatively quantify the adsorption process.

Engineering functionalization and properties of graphene quantum dots (GQDs) with controllable synthesis for energy and display applications

“…75 Recent research by Wang et al reported the effective adsorption of heavy metal Ag using NGQD-PVA composites, where nitrogen and oxygen functional groups were introduced. 76 It's worth noting that GQDs can exhibit different electron behaviors when covalently or non-covalently bonded with other substances. Han et al reported that when GQDs chemically adsorbed onto metal oxide films, they demonstrated enhanced donor–acceptor binding strength and approximately double the interfacial electron transfer rate compared with physical adsorption.…”

Nanostructural Characterization of Luminescent Polyvinyl Alcohol/Graphene Quantum Dots Nanocomposite Films

“…For decades, various fillers have been incorporated into PVA films and their structure-property relationship has been investigated. GQDs have also been used as fillers in PVA matrices and the enhancement of their luminescence properties has been explored [ 2 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ].…”

“…In addition, the SPM data have been significantly related to photoluminescence (PL) emission results, which is of extreme relevance. Although the photoluminescence of GQD fillers within PVA matrices has already garnered significant interest [ 2 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ], a thorough investigation of the nanostructural modifications occurring at the surface of PVA/GQD nanocomposites is still lacking. Understanding and manipulating the nanostructure of these films is crucial for tailoring their properties, constituting a fundamental step toward harnessing the full potential of these materials for practical use.…”