Density Functional Theory Investigation of Graphene Functionalization with Activated Carbenes and Its Application in the Sensing of Heavy Metallic Cations

Abstract

Anthropogenic activities presently generate undesirable industrial and house waste byproducts such as heavy metallic cations (HMCs), which are then often released into the environment, despite being harmful to human beings. Developing new materials that can detect and capture HMCs is therefore highly desirable for wastewater remediation, especially if using cheap starting raw materials such as carbon. To shed theoretical light in this direction, we use density functional theory simulations to study the functionalization of pristine graphene with prototypical carbenes, RC(O)CH, with R = −OCH 3 (2a), −OH (2b), −ONa (2c), and −Ph (2d), and explore their use in sensing and capturing toxic HMCs (here, we focus on the most common and harmful ones: Cd 2+ , Hg 2+ , and Pb 2+ ). We first demonstrate that, starting from activated diazomethanes, RC(O)CHN 2 (1a−d), and graphene as precursors, it is possible to yield substituted cyclopropanes tethered to graphene, here modeled as a 6 × 6 supercell (g6×6), via a [2 + 1]cycloaddition reaction. Projected density of states and band structure calculations show that the cycloaddition reaction induces a band gap opening of the graphene, which can be used to tune it for electronic sensing devices. These nanomaterials (g6×6/3a−d) favorably interact with the metallic cations through coordination bonds with interaction energies varying from −1.18 to −2.75 eV. Differences in the electronic charge density following HMC adsorption reveal regions of electron depletion or gain induced by these interactions. Based on energetic and electronic structure analysis, we suggest that g6×6/3b−d are good candidates to detect HMCs. All the four nanomaterials show a higher affinity toward Pb 2+ , as rationalized by a synergic interaction with the graphene substrate, suggesting that they can be used for Pb 2+ sensing and removal. Notably, we demonstrate that once and only once the proper computational approach is employed, the accuracy of our predictions of a larger interaction strength of Pb 2+ with respect to Cd 2+ is validated via the agreement with available experimental data on g6×6/3b. Finally, we predict that by varying the pH, the g6×6/3b,c pair can be employed to differentially sense Cd 2+ and Hg 2+ cations.

σ‐Hole intermolecular interactions between carbon oxides and dihalogens: Ab‐initio investigations

“…46 Starting from Gaussian optimized complexes, the structures were centered into a cube (10 Â 10 Â 10 Å 3 ), then the electronic density was computed and from which the different properties were derived. 47,48 CCSD(T) 49 reference energies were calculated and used to benchmark the density functionalsωB97X-D, 50 M06-2X 51 and Cam-B3LYP 52 and HF ab-initio second, and fourth-order Møller-Plesset MP2 53,54 and MP4 53,55 methods. Each functional was tested with the following basis set: cc-pVDZ, cc-pVTZ, aug-cc-pVDZ and aug-cc-pVTZ.…”

“…Band structure, DOS, PDOS and differences of electronic density were computed using Quantum ESPRESSO 6.1 44 using PBE functional 45 and Rappe‐Rabe‐Kaxiras‐Joannopoulos ultrasoft pseudo potentials 46 . Starting from Gaussian optimized complexes, the structures were centered into a cube (10 × 10 × 10 Å 3 ), then the electronic density was computed and from which the different properties were derived 47,48 …”

Efficient and Superstable Mineralization of Toxic Cd2+ Ions through Defect Engineering in Layered Double Hydroxide Nanosheets

“…Cadmium (Cd) is a heavy metal with high toxicity . Wastewater and agricultural soils polluted with Cd 2+ ions have become a global issue, owing to the fact that cadmium can accumulate in organisms throughout the food chain and a serious threat to ecosystems and human health. − Recently, a wide range of methods have been explored for cadmium removal from water and soils including adsorption, chemical precipitation, membrane filtration, ion exchange, electro-kinetic extraction, solidification, phytoremediation, and soil washing. − However, their large-scale application is limited due to their high cost, stability, and operational difficulties in practical settings. − Accordingly, adsorbent materials such as carbon-based materials, zeolites, and metal–organic frameworks remain the preferred materials for Cd 2+ capture and remediation. − However, the cadmium adsorption capacity and stability of current adsorbents are still not satisfactory, motivating the search for novel adsorbents that can selectively immobilize cadmium ions with very high adsorption capacities …”

Au3-Decorated graphene as a sensing platform for O2 adsorption and desorption kinetics

“…Graphene has been investigated extensively for gas sensing applications because of its high sensitivity to adsorbed particles, 15 which can be further improved by functionalization, 16 introducing defects, 17 or by forming composites with polymers or metal oxides. [18][19][20] It has been shown that different adsorbed molecules have a different effect on the noise spectrum of graphene, allowing to use graphene as a selective sensor.…”