A sustainable and efficient strategy for stable three-layered borophene fabrication

Abstract

Borophene, a promising two-dimensional material with unique properties, has garnered substantial interest in the realms of nanotechnology and materials science. Despite its potential applications, complex synthesis methods hinder extensive exploration. This study aims to establish a sustainable and scalable fabrication route by employing biocompatible intercalants (sodium cholate, sodium chloride, and urea) in a ball mill, coupled with ultrasound-assisted liquid phase exfoliation (UA-LPE) in water as a medium. Sodium cholate (SC) proved the most efficient, yielding 4-layer borophene at optimal ball-milling conditions (450 rpm for 6 h). What is more, the influence of the weight ratio of SC and bulk boron (B) on the efficiency of exfoliation has been examined. The combination of ball milling and UA-LPE in water achieved a tuned borophene thickness of 3 layers. The air-stability of 3- and 4-layered borophene samples demonstrated resistance to long-term oxidation, affirming their chemical resilience. The proposed mechanism elucidates the process of mechanical exfoliation using SC boosted by UA-LPE. This two-step strategy offers a scalable, facile, efficient, and environmentally friendly approach to obtaining bulk-scale and stable 3-layered borophene samples, facilitating practical applications in line with theoretical studies.