Radical sensitivity and selectivity in the electrochemical sensing of cadmium ions in water by polyaniline-derived nitrogen-doped graphene quantum dots

Abstract

In the present work, the sensing capability of nitrogen-doped graphene quantum dots (N-GQDs) was explored for the first time toward hazardous heavy metal ions and they were found to be able to selectively detect cadmium ions (Cd(ii)).

Metal ion sensing with graphene quantum dots: detection of harmful contaminants and biorelevant species

“…12,15 One of the most extensively employed strategies is the doping of GQDs with nitrogen atoms (N-doping), 4 which has been shown to greatly enhance luminescence and electrical conductivity. 9,12,[16][17][18] The available choice and control of fabrication conditions enables GQDs to be utilised in the development of selective and sensitive fluorescent, electrochemical, colorimetric and hybrid sensors, which typically allow detection of analytes through static or dynamic PL quenching. 6,11,[19][20][21] Detection of metal ions using GQDs is a rapidly growing field of research, 12,[22][23][24] which aims to address the significant issue of increased environmental contamination, 6 whereby soil and water sources are polluted with the accumulation of toxic metal ions.…”

“…3,28 The development of novel sensors for metal ions that are facile, low cost and can be produced through 'green' pathways has been a major focus in recent times. 16 Detection of metal ions using GQD-based sensors relies on a range of mechanisms that can either quench or enhance fluorescence intensity. 23,29 Comprehension of these mechanisms is necessary to better understand how GQDs may selectively detect specific metal ions in the presence of other ions.…”

“…50,99 The application of cadmium in many industrial fields has led to increased water pollution, high levels of which have been associated with pathogenesis of cancers, heart disease, and DNA and central nervous system damage. 16,65,116,117 There is relatively little literature that explores the potential of GQDs for selective detection of Cd 2+ . Table 5 summarises the recent works that have attempted to detect Cd 2+ using GQD based platforms.…”

“…These GQDs are similar to those used in the detection of Pb 2+ and Ag + , where Cd 2+ selectivity is not an inherent property of the unmodified GQDs. 5,16,65,116 N-GQDs have been employed to catalyze reactions that result in colorimetric changes 5 or to oxidise Cd 2+ for further voltammetric stripping analysis, 65 yet these methods have not afforded a great degree of sensitivity or selectivity. This lack of selectivity is most likely due to a reliance of non-specific metal ion interactions with nitrogen and oxygen containing functional groups on the surface of N-GQDs.…”

“…5,65 Recently, an extremely low LOD (8.897 Â 10 À5 nM) was achieved for the highly selective detection of Cd 2+ by using a novel N-GQD modified electrochemical sensor. 16 GQDmodified electrochemical sensors have been shown to display extremely high sensitivities for metal ions in comparison to fluorescence-based GQD sensors, while still providing facile means of detection and offer a promising method for extremely low LODs. 118,119 This high degree of sensitivity is generally attributed to the large surface area to volume ratio of GQDs used to modify electrodes of electrochemical sensors.…”