Hydroxamic acid-functionalized graphene thin films as nanocatalysts towards organophosphate degradation

Abstract

Herein we describe the covalent functionalization of graphene oxide with hydroxamic acid groups (GOHD) anchored directly on the carboxylate groups. The functionalization was confirmed by several characterization techniques, such as infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and Raman spectroscopy. The anchored groups have many potential applications, but we focused on its catalytic activity towards organophosphate (OPs) degradation, a serious environmental and health worldwide issue. The material was applied as nanocatalysts towards the degradation of the organophosphate of diethyl 2,4-dinitrophenyl phosphate and the real-life pesticide dimethyl 4-nitrophenyl phosphate (Paraoxon). High catalytic increments were obtained up to 108 fold (Paraoxon). Thus, reactions that would take over millions of years are reduced to a couple of days. Overall, the nanocatalyst shows potential as efficient detoxifying agents to eliminate chemical warfare stocks and pesticides by employing a practical material that can be deposited on any substrate and even over large areas.

Neighboring Effects on the Selective Bifunctionalization of Graphene Oxide for Nanocatalytic Organophosphate Neutralization

“…Indeed, weight losses are higher in the region related to the anchored functional groups (250–400 °C), and weight losses related to the oxygenated groups decreased more for the bifunctionalized materials than the monofunctionalized ones. Furthermore, the TGA results indicated that the route used for obtaining GOSHIMZ2 was more efficient for group incorporation, i.e., with consecutive addition of the reagents API and CA, in contrast to their simultaneous addition (GOSHIMZ1). , Finally, the functionalized materials also show increased thermal stability in contrast to GO, as a result of the anchored groups (see the detailed table in the Supporting Information, SI) . Regarding the final residue, this can be attributed to a permanganate residue, from the Hummers oxidation.…”

“…Among the several applications of functionalized GO, nanocatalysis stands out, in particular, in the neutralization of toxic organophosphates. , These compounds comprise many agrochemicals and chemical warfare agents; hence, there is an increasing interest in their neutralization (e.g., undesired stocks) and monitoring (e.g., to alert attack and misuses) . Some of our previous studies ,, report targeted monofunctionalization on GO linking thiol, imidazole, or hydroxamic acid groups via amidation. These materials were employed as nanocatalysts toward the degradation of organophosphates and showed high catalytic efficiency.…”

“…20,21 These compounds comprise many agrochemicals and chemical warfare agents; hence, there is an increasing interest in their neutralization (e.g., undesired stocks) and monitoring (e.g., to alert attack and misuses). 22 Some of our previous studies 20,21,23 report targeted monofunctionalization on GO linking thiol, imidazole, or hydroxamic acid groups via amidation. These materials were employed as nanocatalysts toward the degradation of organophosphates and showed high catalytic efficiency.…”

Liquid–liquid interfaces: a unique and advantageous environment to prepare and process thin films of complex materials

“…chemical functionalization) of different materials, resulting in thin films of chemically-functionalized materials. [127][128][129] The chemical functionalization of materials' surfaces has been a very common approach to add new functionalities and modify materials' properties. The L/L interface can be considered a novel environment to perform some well-known functionalization reactions, or to create novel pathways to surface modification, in one single-process in which both the surface functionalization and the functionalized-material processing as thin films are solved together.…”

“…Most interesting is the combination of both functionalities of the nanocomposite thin film, acting as both a catalyst for the organophosphate degradation and SERS sensor for the detection of the product of the same reaction, which means that one single film can both act as a detoxifying agent and sensor to determine if all the toxic compounds were already destroyed. 127 The EDC/NHS methodology has been also used by us to anchor different functional groups at the GO surface, such as imidazole 128 or hydroxamic acid, 129 yielding GO-functionalized thin films at the L/L interface, looking for efficient heterogeneous catalysts for organophosphate and pesticide degradation. Both the imidazole-and hydroxamic acid-functionalized GO materials were demonstrated to be very efficient materials for this purpose, figuring among the best catalysts for the degradation of the pesticide Paraxon or the organophosphate diethyl 2,4-dinitrophenyl phosphate (DEDNPP), showing better performance than similar homogeneous catalysis experiments.…”