Formation of Mercury Droplets at Ambient Conditions through the Interaction of Hg(II) with Graphene Quantum Dots

Abstract

Unlike other metals, Hg forms droplets at ambient conditions when a Hg(II) salt interacts with hydroxyl-enriched graphene quantum dots (HEGQDs). The hydroxylation of GQD surface is evident from FT-IR, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) techniques. The scanning electron microscopy images of Hg(II)-HEGQDs incubated for 0, 1, 24, and 168 h show Hg droplets with the size of 0.1, 0.3, 0.8, and 2 μm, respectively. The XPS studies confirm the presence of Hg(0) and also reveal a noticeable decline in the composition percentage of C−O, whereas a marked increase is observed in the CO composition percentage. The pathway for the formation of droplets induces immediate reduction of Hg(II) to Hg(0) by both hydroxyl groups and π electron cloud present on the surface of HEGQDs, followed by coalescence. The formed Hg( 0) is then strongly adsorbed on the hollow sites of graphene and acts as a nucleation site for the growth of droplets. The kinetics of the reaction obeys LaMer Burst nucleation followed by coalescent growth in addition to autocatalytic reduction and finally follows the Oswald ripening mechanism. The internal pressure of Hg droplets gradually decreases as the radius of the drop increases over the incubation time and liquid−rhombohedral transformation is likely to take place at a radius of 0.8 nm.

Direct Synthesis of Sulfur-Decorating PAMAM Dendrimer/Mesoporous Silica for Enhanced Hg(II) and Cd(II) Adsorption

“…After adsorption Hg(II), the Hg 4f, Hg 4d 5/2 , and Hg 4d 3/2 peaks can be found in the spectrum of G1.0-S-1/2 at about 100.75, 359.20, and 380.06 eV in Figure 7a. 58,59 While the peak of Cd 3d is observed at 401.22 eV after adsorption. 60 It can be observed from Figure 7e, f, the CO peak moves from 531.52 eV to 531.86 and 532.08 eV after uptake Hg(II) and Cd(II).…”

Synthesis, Applications, and Prospects of Graphene Quantum Dots: A Comprehensive Review

“…The addition of GQDs prevented the aggregation of MWCNTs, enabling a higher dispersibility and stability in water for electrochemical measurements. Recently, Kappen et al [272] observed an unusual galvanic reaction (GR) between a GQD-stabilized silver nanoparticles (Ag-GQD)-modified glassy carbon (GC) surface and Hg(II), which resulted in the complete dissolution of the silver nanoparticles (AgNPs) followed by the growth of flower-like Hg(0) on the GQDs surface. The expectation was to observe the formation of a Hg−Ag amalgam/coreshell structure, as the typical outcome of the GR between bulk Ag/AgNPs and Hg(II).…”

Selective Sensing of Epinephrine by Phenylboronic Acid Tethered Carbon Dot

“…Both the heteroatom doping and surface functionality can alter the optical (fluorescence and absorbance) properties of the CDs. [23,24] The doped heteroatoms effects the intrinsic properties of carbon dots, along with their electronic properties, optical properties, and surface reactivity. Recently, sensing of Cu 2 + and D-PA (D-penicillamine) has been establisted by Zhou et al using N-doped Ti 3 C 2 MXene quantum dots.…”

“…Convertible optical property has bestowed carbon dot a prominent role in sensing many different types of analytes. Both the heteroatom doping and surface functionality can alter the optical (fluorescence and absorbance) properties of the CDs [23,24] …”