Structural-Defect-Mediated Grafting of Alkylamine on Few-Layer MoS2 and Its Potential for Enhancement of Tribological Properties

Sangita Kumari; Ajay Chouhan; Om P Sharma; Sruthi Kuriakose; Sherif Abdulkader Tawfik; Michelle J S Spencer; Sumeet Walia; Hiroyuki Sugimura; Om P Khatri

doi:10.1021/acsami.0c08307

Structural-Defect-Mediated Grafting of Alkylamine on Few-Layer MoS₂ and Its Potential for Enhancement of Tribological Properties

ACS Appl Mater Interfaces. 2020 Jul 8;12(27):30720-30730. doi: 10.1021/acsami.0c08307. Epub 2020 Jun 26.

Authors

Sangita Kumari^{1

2

3}, Ajay Chouhan^{1

2}, Om P Sharma¹, Sruthi Kuriakose^{3

4}, Sherif Abdulkader Tawfik⁵, Michelle J S Spencer⁵, Sumeet Walia^{3

4}, Hiroyuki Sugimura⁶, Om P Khatri^{1

2}

Affiliations

¹ CSIR-Indian Institute of Petroleum, Dehradun 248005, India.
² Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
³ School of Engineering, RMIT University, Melbourne, VIC 3000, Australia.
⁴ Functional Materials and Microsystems Research Group and MicroNano Research Facility, RMIT University, Melbourne, VIC 3000, Australia.
⁵ School of Science, RMIT University, GPO Box 2476, Melbourne, VIC 3001, Australia.
⁶ Department of Materials Science and Engineering, Kyoto University, Kyoto 6068501, Japan.

PMID: 32524815
DOI: 10.1021/acsami.0c08307

Abstract

Two-dimensional transition-metal dichalcogenides possess inherent structural characteristics that can be harnessed for enhancement of tribological properties by making them dispersible in lube media. Here, we present a hydrothermal approach to preparing MoS₂ nanosheets comprising 4-10 molecular lamellae. A structural-defect-mediated route for grafting of octadecylamine (ODA) on MoS₂ nanosheets is outlined. The unsaturated d orbitals of Mo at the sulfur vacancies on the MoS₂ surface are coupled with the electron-rich nitrogen center of ODA and yield ODA-functionalized MoS₂ (MoS₂-ODA). The MoS₂-ODA nanosheets exhibit good dispersibility in lube base oil and are used as an additive (optimized dose: 0.1 mg·mL^-1) to mineral oil. It is shown that even at low concentration, MoS₂-ODA nanosheets significantly reduce the friction (48%) and wear (44%). Microscopy (field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM)) and spectroscopy (Raman and elemental mapping) analyses of worn scars revealed the formation of MoS₂-based protective thin films for lowering of friction and wear. This work, therefore, presents a pathway for low-friction lubricants by deploying functionalized low-dimensional material systems.

Keywords: DFT calculations; chemical functionalization; dispersion; lubrication mechanism; molybdenum disulfide; surface analyses.