KR101580211B1 - Method for manufacturing MoS2 nanosheet, agent for the same, and MoS2 nanosheet manufactured by the same - Google Patents

Abstract

Mixing a bulk molybdenum disulfide (MoS2) powder into an organic solvent containing a release promoter composed of an alkali metal or an alkaline earth metal and a hydroxyl group; And subjecting the mixed bulk molybdenum disulfide (MoS2) powder to ultrasonic treatment to prepare a molybdenum disulfide (MoS2) nanosheet. The molybdenum disulfide (MoS2) nanosheet is produced by a process comprising the steps of:

Description

[0001] The present invention relates to a molybdenum disulfide nanosheet, a molybdenum disulfide nanosheet, and a molybdenum disulfide nanosheet,

The present invention relates to a process for producing a molybdenum disulfide nanosheet, a removing solution for the same, and a molybdenum disulfide nanosheet produced thereby. More particularly, the present invention relates to a molybdenum disulfide nanosheet having improved yields of molybdenum disulfide (MoS2) nanosheet, And a molybdenum disulfide nanosheet produced by the method. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molybdenum disulfide nanosheet.

2D layered nanomaterials are of great interest for a new approach to low-dimensional systems. The transition metal dicalcogenide (MX ₂ (M = Mo, W; X = S, Se, Te)) belongs to a family of layered structures whose covalent bond XMX monolayers, like graphite, are bonded by van der Waals forces It is piled up.

Each monolayer consists of two chalcogen (X) atomic layers and a metal atomic layer, with a layer of metal atoms inserted in two layers of chalcogen. J. Radiovic, J. Brivio, V. Giacometti and A. Kis, Nat . Nanotechnol ., 2011, 6 , 147., KF Mak, C. Lee, J. Hone, J. Shan TF Heinz, Phys. Rev. Lett ., 2010, 105, 136805, KK Kam and BA Parkinson, J. Phys. Chem., 1982, 86, 463.) MX 2 has a band gap of 1.1 eV ~ 2.0 eV in . In the case of molybdenum disulfide (MoS ₂ ), there is a transition from a single layer to a direct bandgap (1.8 eV) at an indirect bandgap (1.2 eV) in the bulk state and, therefore, an energy storage device, Application to various fields is being studied.

However, MoS ₂ is not only an insoluble compound but also is nonvolatile, so it is known that it is very difficult to prepare in a thin film state. A mechanical method using Scotch-tape was used for stable single layer MX ₂ extraction. In addition, a technique for peeling a three-dimensional structure into a two-dimensional nanosheet in a liquid phase has also been introduced, and this liquid-phase separation method is one of the most efficient methods for mass production of MX ₂ nanosheets (JN Coleman, M. Lotya , A. O'Neill, SD Bergin, PJ King, U. Khan, K. Young, A. Gaucher, S. De, RJ Smith, IV Shvets, SK Arora, G. Stanton, H.-Y. Kim, K JM Perkins, EM Grieveson, K. Theuwissen, DW McComb, PD JJ Wang, JJ Donegan, JC Grunlan, G. Moriarty, A. Shmeliov, RJ Nicholls, JM Perkins, Nellist and V. Nicolosi, Science, 2011 , 331, 568. HSSR Matte, A. Gomathi,. AK Manna, DJ Late, R. Datta, SK Pati and CNR Rao, Angew. Chem. Int. Ed, 2010, 49, 4059. G. Eda, H. Yamaguchi, D. Voiry, T. Fujita, M. Chen and M. Chowalla, Nano . Lett ., 2011, 11, 5111)

Li-intercalation in the MoS2 peeling technique is a useful method for peeling. However, this method is very sensitive to ambient environmental conditions, which makes it difficult to control the process. There is also a problem that the phase transition of the original MoS ₂ occurs due to lithium-intercalation. Recently, a technique for producing a _{3 to} 12 nm thick MoS ₂ dispersion by direct separation from an organic solvent through ultrasonic treatment has been disclosed. Only Hiza has a problem that this method also shows a low yield and requires a long ultrasonic treatment time to improve the concentration.

Accordingly, a problem to be solved by the present invention is to provide a method for producing molybdenum disulfide (MoS2) nanosheet which improves the yield of molybdenum disulfide (MoS2) nanosheet and reduces the ultrasonic treatment time to improve the economical efficiency, And a molybdenum disulfide (MoS2) nanosheet produced.

In order to solve the above-described problems, the present invention provides a method for manufacturing a semiconductor device, comprising: mixing bulk molybdenum disulfide (MoS2) powder into an organic solvent containing a release promoter composed of an alkali metal or an alkaline earth metal and a hydroxyl group; And subjecting the mixed bulk molybdenum disulfide (MoS2) powder to ultrasonic treatment to prepare a molybdenum disulfide (MoS2) nanosheet. The molybdenum disulfide (MoS2)

In one embodiment of the present invention, the organic solvent is N-methyl pyrrolidone (NMP), and the production yield of the molybdenum disulfide (MoS2) nanosheet increases with the ultrasonic treatment time.

In one embodiment of the present invention, the release promoter is sodium hydroxide.

The present invention also provides a molybdenum disulfide (MoS2) nanosheet prepared by the above-described method, wherein the molybdenum disulfide (MoS2) nanosheet has one to three nanosheets of at least 85% of the total nanosheets.

The present invention also relates to a release promoter composed of an alkali metal or an alkaline earth metal and a hydroxyl group; And an organic solvent, wherein the organic solvent is N-methyl pyrrolidone (NMP), and the exfoliation promoter is sodium hydroxide.

According to the present invention, MoS2 peeling is possible with a remarkably short ultrasonic decomposition time and MoS2 nanosheet yield is about 6 times when ultrasonic treatment is performed by incorporating MoS2 into a peeling solution to which a basic solution is added to an organic solvent. MoS2 can be produced in an economical and efficient manner. In addition, through the exfoliation solution and the process according to the present invention, MoS ₂ Nanosheets can be produced in large quantities.

Figure 1 A) SEM showing the results of the case where the original MoS2 SEM image showing a powder of a SEM image (B) effect of the addition to the pattern diagram (C) NaOH in the structure of MoS ₂ (right, Embodiment) anji not adding NaOH Image (left, comparative).
FIG. 2A is a SEM image of a UV-vis and photoluminescence spectrum (inset: photographic image of dispersed MoS ₂ ) and 2B of MoS2 nanosheet peeled by adding NaOH to NMP.
3A to E are TEM images of MoS ₂ nanosheets, 3F is a tapping-mode AFM image, and 3G is a corresponding line scan result of a MoS2 nanosheet on a silicon substrate.
FIG. 4 (A) Raman spectrum, (B) XPS spectrum of Mo 3d and (C) S 2p of a MoS2 nanosheet film on a SiO ₂ / Si substrate. (D) MoS2 bulk powder, MoS2 nanosheet with NaOH added, and nanosheet without NaOH.
FIG. 5 (A) is a graph showing the charge-discharge curve and (B) the capacity of Coulomb efficiency and cycle number.

The following experimental examples are provided as examples so that those skilled in the art can sufficiently convey the ideas of the present invention. Therefore, the present invention is not limited to the experimental examples described below, but may be embodied in other forms. In addition, abbreviations displayed throughout this specification should be interpreted to the extent that they are known and used in the art unless otherwise indicated herein.

DISCLOSURE OF THE INVENTION The present inventors have made efforts to solve the problems of the above-described conventional techniques, and to provide a high-yield molybdenum disulfide (MoS2) nano-sheet peeling solution which does not cause problems of workability and phase transition in the surrounding environment, The present invention provides a method for producing a MoS2 nanosheet.

To this end, the present invention uses an organic solvent containing a compound consisting of an alkali metal or an alkaline earth metal and a hydroxyl group (hereinafter referred to as a release promoter) as a peeling liquid, and a molybdenum disulfide (MoS2) powder in a bulk state is mixed in the peeling liquid, The molybdenum disulfide (MoS2) nanosheet was prepared by ultrasonic treatment. In particular, when a solvent having a high dielectric strength to MoS2 such as N-methylpyrrolidone (NMP) and a peel accelerator containing a hydroxyl group and an alkali metal or an alkaline earth metal such as NaOH are mixedly used The present invention provides an economical method for separating nanosheets of MoS2 from the novel fact that Na + and OH- ions are easily permeated into the space inside the MoS2 layer.

MoS2  Nanosheet dispersion

First, NaOH (5 g) was dissolved in NMP (20 mL) and MoS2 bulk powder (20 mg) was added to the NaOH solution. The mixture was sonicated in an ultrasonic instrument for 2 hours. For the control experiment, a mixture of NaOH and NaOH was used.

Experiment result

Figure 1 A) SEM showing the results of the case where the original MoS2 SEM image showing a powder of a SEM image (B) effect of the addition to the pattern diagram (C) NaOH in the structure of MoS ₂ (right, Embodiment) anji not adding NaOH Image (left, comparative).

In this experiment, the mixed solution was sonicated for 2 hours in a bath sonicator, and a peeling solution in which no basic solution such as NaOH was added was used in the comparative example.

After the ultrasonic treatment for 2 hours, the exfoliation solution of the Example or Comparative Example was centrifuged at 2000 rpm for 30 minutes using a centrifuge (Hanil Industrial Co., Ltd., Combi 514R), and the precipitate was MoS ₂ or Thrown away to remove thick pieces.

With respect to the third one supernatants of MoS ₂ separation membrane obtained in the positive electrode aluminum oxide (anodic aluminium oxide, AAO) ( Anodisc 47, 0.025 ㎛ pores, Whatman) the inner layer area of the MoS ₂ nanosheets with a vacuum filter for use Respectively. The remaining supernatant with or without NaOH was centrifuged at 9000 rpm for 45 minutes, the supernatant discarded and fresh NMP solvent added.

The solution was then sonicated for 3 minutes and centrifuged at 9000 rpm for 45 minutes to remove most of the NaOH. The washing procedure was repeated several times to obtain a clean solution with NaOH. The pH of the supernatant was measured using a pH test paper to confirm the removal of NaOH after each centrifugation. After centrifugation, the volume of the precipitate to which NaOH was added was much greater than that without addition of NaOH (Fig. 1 (C)). Compared with the peeling solution of the comparative example, the yield of the MoS2 nanosheet in the peeling solution of the Example was increased to about 6 times. From the above results, it can be seen that under the ultrasonic process, NaOH added to the exfoliation solution contributes to exfoliation of the MoS ₂ layers, and as a result, the concentration of the exfoliated MoS ₂ sheet is significantly improved. The concentration of MoS ₂ added with NaOH was very high when the ultrasonic decomposition time was prolonged. This also means that NaOH facilitates peeling of the MoS ₂ bulk pieces.

After the washing, additional sonication was performed for 40 minutes to prepare the final MoS ₂ dispersion. The final yield solution between 2000 rpm and 9000 rpm was dark green and remained stable for several days without agglomeration.

To the characterization of the final solution by UV-vis spectrophotometer, it was used for the SiO ₂ / Si substrate according to the drop casting method to prepare a MoS2 film, and analyzed the characteristics of the nano-sheet by SEM and photoluminescence.

FIG. 2A is a SEM image of a UV-vis and photoluminescence spectrum (inset: photographic image of dispersed MoS ₂ ) and 2B of MoS2 nanosheet peeled by adding NaOH to NMP.

Referring to FIG. 2A, the spectrum of the MoS2 nanosheet dispersed using the release agent according to the present invention shows two peaks (A and B) between 600 nm and 700 nm, and a broad band near 450 nm having a shoulder at 399 nm Also shown. The A and B peaks are characteristic of 2H-MoS ₂ nanosheets and represent the least direct transition. At this time, the peak positions for the excitons of A and B are 670 nm (1.85 eV) and 607 nm (2.04 eV), with an energy difference of 0.19 eV. Emissary values show blue shift compared to known data for bulk powder (748 nm (1.66 eV)). The blue shift is due to the quantum-size confinement, which is consistent with previous studies.

Referring also to Figure 2B, the MoS ₂ thin film on the SiO ₂ / Si substrate clearly shows that the 2D slices have a base plate and an edge.

The inventors investigated the dispersion of MoS ₂ nanosheets through TEM analysis. FIG. 3 shows TEM images of several layers of MoS ₂ nanosheets on a Holy carbon TEM grid.

Referring to FIG. 3, TEM images of MoS ₂ nanosheets generally appear as partially folded corrugated sheets, such as graphene sheets, and HRTEM images of MoS ₂ nanosheets (see FIG. 3E) show a very clear edge.

This was obtained with the black circles as shown in the lower left of FIG. 3D, and the embedded portion of FIG. 3E shows a typical electron diffraction pattern of the exfoliated MoS ₂ .

The AFM image provides additional information on the thickness of the single layer and the efficient removal of MoS ₂ nanosheets. Through AFM analysis, the inventors have found a correlation between the morphology and the thickness of the nanosheet film.

Figures 3F and G show AFM images and layer heights of a single layer of MoS ₂ nanosheets on a SiO ₂ / Si substrate.

Referring to Figures 3F and G, the layer height of the nanosheets was measured to be 1.2 nm. This thickness is quite consistent with previous studies on single layer MoS ₂ in liquid phase stripping.

According to the TEM and AFM images obtained from the above results, it can be seen that the side dimensions of the nanosheets range from 50 nm to 1 μm. In addition, a single layer of MoS ₂ nanosheets represents side lengths less than 300 nm.

Raman spectra provide easy and qualitative characterization of MoS ₂ nanosheets.

FIG. 4 (A) Raman spectrum, (B) XPS spectrum of Mo 3d and (C) S 2p of a MoS2 nanosheet film on a SiO ₂ / Si substrate. (D) MoS2 bulk powder, MoS2 nanosheet with NaOH added, and nanosheet without NaOH.

Referring to Figure 4, 385.6 cm ^- typical peak known as E ¹ _2g peak at ¹ is a is derived from the vibration plane of the Mo-S A _1g peak near 408 cm ^-1 is non-planar vibration is observed. The original MoS ₂ powder spectrum shows peaks at 383 and 409 cm ^-1 . Peak difference between E ¹ and A _{2g 1g} are 26 cm for the original MoS ₂ ^{- 1,} but is for a MoS ₂ dispersion made in accordance with the present invention 22.4 cm ^-1. That is, the numerical value of the MoS ₂ dispersion according to the present invention is smaller than that of the original MoS ₂ powder. This peak differences may be used to measure the number of layers MoS _2, MoS ₂ dispersion of 22.4 cm in accordance with the present ^invention that peak ¹ corresponds to the difference MoS2 three-layer structure. In addition, the line widths (6 to 7 cm ^-1 ) for MoS 2 dispersions according to the invention are greater than the known data (2 to 6 cm ^-1 ) for MoS ₂ single crystals by mechanical stripping methods. The line broadening is due to smaller crystal size and larger defects than the MoS ₂ single crystals of previous studies, including the liquid phase stripping method.

The MoS ₂ nanosheet of the three-layer structure is clearly seen in the PL spectrum of FIG. 2 (A) (red line). The PL spectrum consists of one major peak at 665 nm (1.86 eV) and one shoulder peak at 614 nm. And it matches the excitation energy directly from the bandgap PL, which is in good agreement with known data.

Thereafter, the present inventor performed an XPS measurement, which is shown in Figs. 4 (B) to 4 (D).

In Figure 4 (B), Mo 3d peaks corresponds to the value of ^{Mo 4 + 3d5 / 2 (229.3} eV) and ^{Mo 4 + 3d3 / 2 (232.6} eV) expected for Mo ^{4 +} in MoS _2. Corresponding S 2p peak is composed of a doublet of 2p ^1/2 (163.4 eV) and S 2p3 / 2 (162.3 eV) . This S ² MoS ₂ on ^- is equivalent to the type. This shows a small peak around 236 eV and corresponds to Mo ^{6 +} 3d 5/2 of Mo oxidation.

In the peeling test according to the invention, NaOH facilitates the separation of MoS ₂ fragment, that is, in order to characterize the intercalation of NaOH in MoS ₂ nanosheets present inventors were the XRD (X-ray diffraction) Measuring the original MoS ₂ powder and that of the membrane peeled from the NMP without addition of NaOH, which can be seen in Figure 4 (D).

The XRD peak of the (002) crystal face of the re-deposited MoS ₂ film in the NaMP-free NMP solution has the same pattern as the peak of the (002) crystal face of the original MoS ₂ powder. This implies that the space of the inner layer of MoS ₂ was not changed by the treatment at the NMP and implies that the MoS ₂ inner layer does not affect the NMP molecule for the intercalation. However, the reconstituted film of MoS ₂ treated with NaOH shows that the peak of (002) crystal plane moves down at night. The peak indicates that the inner layer space of the film was partially expanded due to the addition of NaOH at a low diffraction angle of the (002) crystal plane peak. As mentioned in the XPS analysis for Mo oxidation, a small peak of Mo oxidation was analyzed with Na ₂ MoO ₄ in the XRD spectrum and no peak was found around 168 eV for the oxidized sulfur atom.

In conclusion, the peeled MoS ₂ nanosheets exhibited electrochemical properties of the oxidized electrode material of the sodium-ion battery.

FIG. 5 (A) is a graph showing the charge-discharge curve and (B) the capacity of Coulomb efficiency and cycle number.

Referring to FIG. 5, the charging and discharging curves are shown at a current density of 20 mA g ^-1 . In the first sodiation curve, two stabilizers appear at 0.94 V and 0.84 V, and four stabilizers are observed at 1.3, 1.6, 2.3, and 2.5 V in the first desodation curve. From the second cycle, the Sodiation and Desodiation curves are changed from the stable curve of the first curve to the curve with the gradient.

The sodiation capacity is gradually reduced as the cycle repeats, and after 45 cycles the capacity is 96 mA hg ^{- 1} . (Fig. 5 (B)).

As noted above, the present inventors have stripped the MoS2 monolayer sheet very quickly in an organic solvent such as NMP containing a release promoter. In particular, when a solvent having a high dielectric strength to MoS2 such as NMP and a peel accelerator containing a hydroxyl group and an alkali metal or an alkaline earth metal such as NaOH are mixedly used, Na + And the penetration of OH- ions becomes easy. As a result, in the ultrasonic condition, NaOH helps easy separation of the MoS2 layer, and a sufficient concentration of the MoS2 nanosheet dispersion can be obtained even though the reaction time is short. The obtained MoS2 sheet mainly has a thickness of a single layer or several layers. Accordingly, the present invention can produce an MoS2 nanosheet in an economical and efficient manner by promoting the exfoliation of MoS2 by using a basic solution such as NaOH mixed with an organic solvent such as NMP.

Claims (8)

Mixing a bulk molybdenum disulfide (MoS2) powder into an organic solvent containing a release promoter composed of an alkali metal or an alkaline earth metal and a hydroxyl group; And
(MoS2) nanosheet by sonicating the mixed bulk molybdenum disulfide (MoS2) powder, wherein the molybdenum disulfide (MoS2)
Wherein the organic solvent is N-methyl pyrrolidone (NMP), and the exfoliation promoter is sodium hydroxide. delete The method according to claim 1,
Wherein the molybdenum disulfide (MoS2) nanosheet increases the production yield according to the ultrasonic treatment time. delete delete delete A release promoter composed of an alkali metal or alkaline earth metal and a hydroxyl group; And
(MoS2) peeling solution comprising an organic solvent, wherein the organic solvent is N-methyl pyrrolidone (NMP), and the peeling accelerator is sodium hydroxide. The molybdenum disulfide (MoS2) liquid.
delete

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