Large-Scale, Highly Efficient, and Green Liquid-Exfoliation of Black Phosphorus in Ionic Liquids

Abstract

We developed a facile, large-scale, and environmentally friendly liquid-exfoliation method to produce stable and high-concentration dispersions of mono- to few-layer black phosphorus (BP) nanosheets from bulk BP using nine ionic liquids. The prepared suspensions can stabilize without any obvious sedimentation and aggregation in ambient air for one month. In particular, the concentration (up to 0.95 mg mL(-1)) of BP nanoflakes obtained in 1-hydroxyethyl-3-methylimidazolium trifluoromethansulfonate ([HOEMIM][TfO]) is the highest reported for BP nanosheets dispersions. This work provides new opportunities for preparing atomically thin BP nanosheets in green, large-scale, and highly concentrated processes and achieving its in situ application.

Efficient Production of Phosphorene Nanosheets via Shear Stress Mediated Exfoliation for Low‐Temperature Perovskite Solar Cells

“…This is not surprising since i) the sample was prepared on an oxidized Si substrate and ii) the fact that phosphorene flakes have been shown to readily react in air to form an oxide . The lattice spacing of our phosphorene sheet was measured to be 0.25 nm, which is in agreement with previous literature (Figure i) …”

“…The transmission electron microscopy (TEM) image illustrated in Figure e reveals that our phosphorene is an ultrathin nanosheet. Selected area electron diffraction (SAED) was further used to confirm the high‐quality single‐crystal structure of our phosphorene (see Figure e inset), which is consistent with previous reports . The elemental mapping in Figure f–h indicates that our sample consists of mainly phosphorus with a slight amount of oxygen.…”

“…The histogram of heights was obtained from a large number of measurements from multiple AFM images (a total of 459 measurements) and is shown in the inset of Figure d. The average thickness of our phosphorene nanosheets was 4.3 ± 0.4 nm, which is a very narrow thickness distribution as compared to the previous solution processed phosphorene samples prepared using other LPE methods . Considering the thickness of monolayer phosphorene is ≈0.85 nm, the measured thicknesses of our nanosheets suggest that the average layer number of our phosphorene is four to six layers, which is consistent with the layer number calculated from the Raman data.…”

Emerging Trends in Phosphorene Fabrication towards Next Generation Devices

“…ILs are presented by researchers for efficient exfoliation of 2D materials to obtain a stable yield with a high concentration of the suspended nanoflakes 200, 201, 202, 203. ILs exhibit viscosities that are 1−3 orders of magnitude more than those of conventional organic solvents; this influences the rate of mass transport within the solution by preventing the BP nanosheets from restacking 198, 200.…”

Optical and Optoelectronic Properties of Black Phosphorus and Recent Photonic and Optoelectronic Applications

“…For the latter, several organic solvents such as N ‐methyl pyrrolidone (NMP), N , N ‐dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and cumyl hydroperoxide (CHP) have been utilized to prepare BP nanosheets on a large scale. To be environmentally friendly, ionic liquids have been used in lieu of these solvents, and large concentrations of BP nanosheets (≈0.95 mg mL −1 ) with stability under ambient conditions have been produced . Guo et al reported that the addition of a proper amount of alkali (NaOH) to NMP could boost the yield and improve the stability of BP nanosheets .…”