Graphene-Rhodamine Nanoprobe for Colorimetric and Fluorimetric Hg²⁺ Ion Assay

Abstract

This article reveals the first ever prospective application of Graphene-Rhodamine array (GRH) as a colorimetric and fluorimetric sensor for Hg(2+) ions. The duality of Graphene to undergo π-π and dispersive interactions with Rhodamine as well as to act as a selective adsorbent for Hg(2+) is conceptualized in this study. These interactions lead to decrease in absorbance of the dye in the presence of graphene, which is restored when kept in contact with Hg(2+) ions. The feasibility of the mechanism has been proved using EDTA as the coordinating ligand. It is noteworthy that all the optical variations occurred in the visible scale of the electromagnetic spectrum. The GRH array exhibited higher sensitivity toward the target ion with a limit of detection of 2 ppb. A perfect linear variation of absorbance at 554 nm with Hg(2+) concentration was observed in 0-1000 nM range, enabling the use of the system as a quantitative sensor for the test ion. The commendable selectivity of the array toward Hg(2+) ion has been investigated by observing the optical response in the presence of other environmentally relevant metal ions. A reversible turn off and turn on INHIBIT logic gate has been proposed which extends the scope of the designed array for the development of automated chemical systems. The fluorescence resonance energy transfer (FRET) ability of graphene paves the backbone for the fluorimetric detection. Fluorimetric strategy yielded a much lower limit of detection of 380 ppt using this probe, which makes a significant advance in trace detection of Hg(2+) ions.

A ratiometric and colorimetric probe for detecting Hg2+ based on naphthalimide–rhodamine and its staining function in cell imaging

“…So far, studies on Hg 2+ probes have been mainly focused on using uorescence intensity as an identifying signal. [11][12][13][14][15] However, these intensity-based probes have a range of disadvantages because intrinsic and extrinsic factors may affect the measurement of uorescence intensity during the test.…”

Fluorescence- and FRET-based mercury (II) sensor

“…Practically, an effective sensor should react to a specific analyte at once; otherwise the detection procedure will have error [25]. Therefore, selectivity is a significant parameter to assess the applicability of the sensor [3][4].…”

“…Hg 2+ in the contaminated natural water with its deleterious effect on human health offers the scientific community a challenging task of developing rapid, cost-effective, environmentally friendly, sensitive and selective Hg 2+ detection methods to detect this harmful pollutant in aqueous environment. Therefore, the topic regarding detection of Hg 2+ in aqueous environments has assumed a serious significance in the scientific mind so that its resultant health complications could be avoided [25][26][27].…”

“…These are mainly a single fluorescence signal based sensors, where, the signal may be readily disturbed by environmental perturbations e.g. pH, temperature, solvent, excitation source fluctuation, sensor concentration etc [25][26][27]. This can be overcome by employing ratiometric FRET based fluorescence sensing system, where, two fluorescence signals are used.…”

Highly selective, colorimetric detection of Hg2+ based on three color changes of AuNPs solution from red through sandy beige to celandine green

“…But all of these analytical methods are carried out by means of expensive instrument and complicated sample preparation processes in certain cases. Recently, rhodamine [8] and metal nanoparticles [9][10][11] ions using aggregated AuNPs and a DNA-based machine with a limit of detection (LOD) of 10 nM and 1 nM, respectively. [12] This aggregation can trigger a color change from red to blue owing to the interparticle coupled plasmon excitons in the aggregated states.…”