Evaluating the Exfoliation Efficiency of Quasi-2D Metal Diboride Nanosheets Using Hansen Solubility Parameters

Abstract

Non-van der Waals (non-vdW) solids are emerging sources of two-dimensional (2D) nanosheets that can be produced via liquid-phase exfoliation (LPE), and are beginning to expand our understanding of 2D and quasi-2D materials. Recently, nanosheets formed by LPE processing of bulk metal diborides, a diverse family of layered non-vdW ceramic materials, have been reported. However, detailed knowledge of the exfoliation efficiency of these nanomaterials is lacking, and is important for their effective solution-phase processing and for understanding their fundamental surface chemistry, since they have significant differences from more conventional nanosheets produced from layered vdW compounds. Here in this paper we use Hansen solubility theory to investigate nanosheets of the metal borides CrB2 and MgB2 derived from LPE. By preparing dispersions in 33 different solvents, we determine Hansen solubility parameters (δ D, δ P, δ H) for both these metal diborides. We find that they exhibit notably higher δ P and δ H values compared to conventional vdW materials such as graphene and MoS2, likely as a result of the types of bonds broken in such materials from exfoliation which allows for more favorable interactions with more polar and hydrogen-bonding solvents. We apply the solubility parameters to identify cosolvent blends suitable for CrB2 and MgB2 that produce dispersions with concentrations that match or exceed those of the top-performing individual solvents for each material and that have markedly higher stability compared to the constituent solvents of the blends alone. This work provides insight into the exfoliation effectiveness of different solvents for preparation of nanosheets from metal diborides and non-vdW materials in general. Such knowledge will be crucial for developing liquid-phase exfoliation strategies for incorporating these materials in applications such as nanocomposites, inks, and coatings.

Ultra-Robust Thermoconductive Films Made from Aramid Nanofiber and Boron Nitride Nanosheet for Thermal Management Application

“…In the top-down approach, the liquid-phase exfoliation method was the most widely used because of its low cost, simple process, and the possibility of further improvement [ 38 , 39 , 40 , 41 ]. In Figure 1 a, the process of exfoliation of h-BN into BNNS and attachment of AgNP on its surface is shown.…”

“…The reason for the increasing trend from 5:0 to 2:3 was that the BNNS dispersed better due to the addition of IPA, and the ultrasonic cavitation effect of IPA was better than that of H 2 O because the surface tension of IPA (21.7 dyn/cm) was less than that of H 2 O (72.7 dyn/cm) [ 19 ]. A possible explanation for the downward trend of yield after 2:3 was that when IPA:H 2 O = 2:3, the mixed solvent had the best Hansen solubility parameters and the most suitable solvent viscosity, which was beneficial to the dispersion stability of BNNS [ 38 ].…”

2D boron nanosheet architectonics: opening new territories by smart functionalization

“…5(a)]. [83][84][85] This means that boron nanosheets exfoliated in different solvents could show different properties. The functional groups introduced by different organic solvents, such as alcohol, amide, dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO), usually exhibit a combination of -O, -OH, -NH 2 , -S]O, alkyl, alkoxy groups, etc., which can lead to broad application but at the same time give rise to difficulty in understanding the individual effect of each functional group.…”

“…Alcohols are efficient solvents that aid in producing boron nanosheets in high yield. 83 Alcohols can tune the band gap of boron nanosheets and borophene due to -OH and -H groups, and the resultant boron nanosheets have been tested for catalysts and optical devices. 21,86 Sun et al prepared boron nanosheets in isopropanol (IPA) and found that the prepared boron nanosheets can effectively catalyze the nitrogen reduction reaction (NRR) with a high faradaic efficiency of 4.04% and a high NH 3 yield of 13.22 mg h À1 mg cat À1 at À0.80 V. 21 The active sites were determined to be the oxidized and H-deactivated B atoms [Fig.…”

Hansen Solubility Parameter Analysis on Dispersion of Oleylamine-Capped Silver Nanoinks and their Sintered Film Morphology

“…Based on the HSP approach, we can quantitatively predict solute solubility in a given solvent. Recently, the HSP sphere has been extended to the prediction of particle dispersion in solvents, including carbon, metal oxides, and metal nanoparticles [16][17][18][19][20][21][22][23][24][25][26]. The particle's HSP sphere was based on particle dispersibility experiments of various solvents (high/low dispersibility).…”