Thymine Functionalized Graphene Oxide for Fluorescence “Turn-off-on” Sensing of Hg²⁺ and I^– in Aqueous Medium

Abstract

Selective detection of either mercury (Hg2+) or iodide (I-) ion using fluorescence turn-on or turn-off processes is an important area of research. In spite of intensive research, simultaneous detection of both mercury and iodide using fluorescence turn-off-on processes, high sensitivity and theoretical support concerning the mechanisms are still lacking. In the present work, graphene oxide is functionalized by thymine to realize simultaneous detection of both Hg2+ and I- selectively using fluorescence turn-off-on mechanism. Ultra high sensitivity to the extent of ppb level exploiting large surface area of graphene is achieved. DFT calculations also assist to realize the detailed mechanisms involving this PL quenching and also its regain during sensing of these ions in aqueous solution.

Fluorescence and Sensing Applications of Graphene Oxide and Graphene Quantum Dots: A Review

“…A similar sensor platform has been used for I − detection, as shown in Figure 7 (c). [27] As the binding constant [28] for Hg 2+ and I − is >10 29 , much larger than that for Hg 2+ and thymine which is ≈10 6 , HgI 2 is preferentially formed and pulls the Hg 2+ ions away from the GO surface, leading to recovery of the quenched fluorescence and allowing I − to be detected. In addition, the GO sensor platform based on charge transfer has been successfully applied for various other environmental and agricultural pollutants detection such as Au 3+ , Fe 3+ , Fe 2+ , Co 2+ , Ni 2+ , Cd 2+ , HCl, et al [15d,e, 29] …”

Highly luminescent N-doped carbon quantum dots from lemon juice with porphyrin-like structures surrounded by graphitic network for sensing applications

“…from waste water. [21][22][23][24][25] In the context of materials synthesis it is highly desirable to explore new carbon source for simple, economical, and green synthesis of such CQDs and currently, a broad series of synthesis routes are being used to synthesize CQD-based materials, 23,26,27 however, efficient one-step strategy for the fabrication of biocompatible uores-cent CQDs on a large scale is still a challenge. Direct synthesis of CQDs from food products mainly from natural food items is one of the promising strategies.…”

A carbonothioate‐based highly selective fluorescent probe with a large Stokes shift for detection of Hg2+

“…Many methodologies have been used to detect Hg 2+ , such as atomic absorption spectroscopy, electrochemical analysis, inductively coupled plasma mass spectrometry, optical probes and so on . Among these methods, optical probes might be the most attractive method due to their high selectivity, sensitivity, quick response and relatively low‐cost .…”

“…[10] Many methodologies have been used to detect Hg 2+ , such as atomic absorption spectroscopy, electrochemical analysis, inductively coupled plasma mass spectrometry, optical probes and so on. [11][12][13][14][15] Among these methods, optical probes might be the most attractive method due to their high selectivity, sensitivity, quick response and relatively low-cost. [16][17][18][19][20][21][22] Despite reports on Hg 2+ detection, some shortcomings still existed, such as longer response time, bad water solubility, a smaller Stokes shift, and poor selectivity ( Table 1).…”