Original Article:
Anchored CoCO3 on peeled graphite sheets toward high-capacity lithium-ion battery anode
Ravi Kumar, et al.
Materials Chemistry and Physics, 2020, 240, 121922.
10.1007/s10853-021-05933-y
Toxic gases such as ammonia produced in industrial and production processes can have harmful effects on human skin, respiratory system, etc. Many methods and materials have been developed to detect these toxic gases, such as metal oxides, conductive polymers, carbon nanotubes, graphene, and various composite materials. Among them, the disadvantages of pristine graphene are poor selectivity and aggregation tendency, which can be modified by functionalization to improve the sensitivity response and selectivity for ammonia detection. The current challenge of gas sensing materials lies in the need to develop high-efficiency gas sensors that operate at room temperature, are stable, and have enhanced selectivity.
Past studies have reported many materials for graphene functionalization, including heteroaryl/aniline functionalization, doxylamine and ethylenediamine functionalization, and fluorinated graphene oxide, etc. In this work, the authors utilized the esterification reaction between graphene oxide (GO) and m-toluic acid (MTA) to functionalize GO with MTA.
Synthetic Route of m-Toluic Acid Functionalized GO
In this study, the covalent coupling of m-toluic acid and GO was achieved through an esterification reaction. During the synthesis of functionalized GO, dicyclohexylcarboimide (DCC) and hydroxybenzotriazole (HOBt) were introduced as reaction catalysts. These two catalysts act as coupling agents for ester formation. MTA with a carboxyl group (-COOH) reacts with GO with a hydroxyl group (-OH) to form an ester group for functionalization.
1. Disperse GO in DMF and sonicate at room temperature to obtain homogeneous dispersion of GO.
2. Prepare homogeneous solution of MTA in DMF by sonication at room temperature.
3. Stir and mix the above two solutions under heating conditions.
4. Add DCC and HOBt in powder form to the mixture with constant stirring.
5. After the reaction was completed, the MTA-functionalized GO samples were obtained by centrifugation and washing.
Schematic diagram of coupling m-toluic acid on GO surface by esterification reaction
Ammonia Sensing Mechanism of m-Toluic Acid Functionalized GO
The gas sensor has the advantages of working at room temperature, wide detection range, no purge gas, and recovery without ultraviolet irradiation. There may be multiple possibilities for the interaction of ammonia with MTA-functionalized GO, resulting in possible physisorption and dissociation mechanisms for ammonia molecules including:
- NH3 molecules are physically adsorbed on the top bridging carbon or functionalized GO hollow sites.
- The opening of the epoxide ring on the GO surface can generate oxygen and carbon sites, which may chemisorb dissociated NH2 and H molecules.
- The dissociated NH3 molecules may adsorb on the carbon defect sites on the surface of MTA-functionalized GO and form σ bonds with carbon atoms, thereby forming adjacent C-NH2 and C-H bonds.
- The ammonia molecule can interact with the oxygen atom of the ester group through the hydrogen bond of the H atom of NH3 to form a H2NH·O bond configuration.
Chemicals Related in the Paper:
| Catalog Number | Product Name | Structure | CAS Number | Price |
|---|---|---|---|---|
| ACM9947 | M-Toluic Acid |  |
99-4-7 | Price |
| ACM99947 | m-Toluic acid |  |
99-94-7 | Price |
