Method of forming nano-layered material using polysaccharide-containing dispersant

Abstract

This disclosure provides a method for forming nanolayered materials using a polysaccharide-containing dispersant. The method includes the following steps: mixing the polysaccharide-containing dispersant and a precursor bulk material in water to form a first mixed aqueous solution; and subjecting the first mixed aqueous solution to ultrasonic oscillation to form a second mixed aqueous solution, wherein the precursor bulk material forms nanolayered materials with dimensions smaller than the precursor bulk material.

Description

[Technical Field]

[0001] This disclosure relates to a method for forming nanolayered materials using a polysaccharide dispersant. [Previous Technology]

[0002] Two-dimensional nanomaterials have numerous applications, such as their use as catalysts. However, methods for preparing two-dimensional nanomaterials from precursor materials present many challenges. For example, traditionally, precursor materials are prepared into two-dimensional nanomaterials in organic solvents or acidic solutions. This process is not only complex but also poses significant risks to the environment and personnel. Furthermore, the yield may be low, and residual organic solvents or acidic solutions can easily remain, affecting the subsequent applications of the two-dimensional nanomaterials. Therefore, there is a need to develop a new method for preparing two-dimensional nanomaterials that is more environmentally friendly, easier to operate, lower in cost, safer, and more effective. [Summary of the Invention]

[0003] This disclosure provides a method for forming nanolayered materials using a polysaccharide dispersant. The method includes the following steps: mixing a polysaccharide dispersant and a precursor bulk material in water to form a first mixed aqueous solution; subjecting the first mixed aqueous solution to ultrasonic oscillation to form a second mixed aqueous solution, wherein the precursor bulk material forms nanolayered materials with dimensions smaller than the precursor bulk material.

[0004] In some embodiments, the polysaccharide dispersant includes dextran, carboxymethyl dextran, carboxymethyl dextran salts, carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof.

[0005] In some embodiments, the precursor bulk material includes graphite, graphene, boron nitride, tungsten disulfide, molybdenum disulfide, tungsten diselenide, molybdenum diselenide, molybdenum distelluride, or combinations thereof, and the nanolayered material includes graphite nanolayered material, graphene nanolayered material, boron nitride nanolayered material, tungsten disulfide nanolayered material, molybdenum disulfide nanolayered material, tungsten diselenide nanolayered material, molybdenum diselenide nanolayered material, molybdenum distelluride nanolayered material, or combinations thereof.

[0006] In some embodiments, the thickness of the nanolayer material is less than 10 nanometers, and the average number of layers of the nanolayer material is less than 10 layers.

[0007] In some embodiments, the precursor block is a micron-sized precursor block.

[0008] In some embodiments, the polysaccharide dispersant is soluble in water and has at least one hydrophilic group, so as to dissolve in the second aqueous solution and adsorb onto the nanolayer material.

[0009] In some embodiments, the weight ratio of the polysaccharide dispersant to the precursor bulk material in the first mixed aqueous solution is 0.001:1 to 1.2:1.

[0010] In some embodiments, the total oscillation time of the ultrasonic oscillation is at least 25 minutes.

[0011] In some embodiments, the method further includes centrifuging or vacuum filtering the second mixed aqueous solution to separate the nanolayered material from the remaining precursor bulk material.

[0012] In some embodiments, the polysaccharide dispersant is formed from a precursor polysaccharide compound via an operation including a carboxymethylation process, wherein the degree of substitution of the active groups on the precursor polysaccharide compound by carboxymethylation is at least 0.75.

Implementation Method

[0014] To make the description of this disclosure more complete, various aspects of the embodiments are described illustratively below, but this is not to limit the embodiments of this disclosure to the only form. The embodiments of this disclosure may be combined with or substituted for each other where advantageous, and other embodiments may be added without further explanation.

[0015] Spatial relative terms, such as above, below, etc., may be used in this disclosure to describe the relationship between one element (or feature) and another element (or feature). In addition to describing the direction, spatial relative terms are intended to cover different orientations of the device during use or operation. For example, the device may be oriented in other ways (e.g., rotated 90 degrees), and the spatial relative terms should be interpreted accordingly. In this disclosure, unless otherwise stated, the same element numbers in different figures are the same or similar elements formed of the same or similar materials by the same or similar methods.

[0016] The terms "approximately," "close to," "substantially," "truly," etc., used in this disclosure include the values ​​(or features) and deviations of the values ​​(or features) as understood by those skilled in the art. For example, taking into account errors in values ​​(or features), these terms may indicate values ​​within one or more standard deviations (e.g., values ​​within ±30%, ±20%, ±15%, ±10%, or ±5%), or may indicate deviations included in the practical operation of a feature (e.g., "truly parallel" may mean practically parallel rather than ideally perfectly parallel). Furthermore, an acceptable range of deviation may be selected based on the nature of the measurement or other properties, and a single range of deviation may not apply to all values ​​(or features).

[0017] This disclosure provides a method 100 for forming nanolayered materials using a polysaccharide dispersant, as shown in Figures 1 and 2. The method includes operations 101 and 102. Operation 101 includes mixing a polysaccharide dispersant and a precursor bulk material in water to form a first mixed aqueous solution 200. Operation 102 includes ultrasonically agitating the first mixed aqueous solution 200 to form a second mixed aqueous solution 300, wherein the precursor bulk material forms nanolayered materials with dimensions smaller than the precursor bulk material in the second mixed aqueous solution 300. The polysaccharide dispersant of this disclosure can assist the precursor bulk material in forming smaller nanolayered materials in water, and the polysaccharide dispersant also helps to keep the nanolayered materials dispersed and non-precipitated in water. The method 100 of this disclosure will now be described in detail with reference to some embodiments.

[0018] First, operation 101 is described, in which a polysaccharide dispersant and a precursor bulk are mixed in water to form a first mixed aqueous solution 200. In some embodiments, the polysaccharide dispersant is soluble in water, which is beneficial for helping the precursor bulk form a nanolayered material in water in subsequent operation 102 and for stabilizing the structure of the nanolayered material in water. Therefore, the present disclosure can substantially eliminate the use of organic solvents and / or acidic solutions when forming and storing nanolayered materials to avoid harm to the environment and / or operators, and also makes the operation easier and more cost-effective. In some embodiments, the polysaccharide dispersant has at least one hydrophilic group and / or a charged group, which is more conducive to adsorption onto the nanolayered material in water and stabilizing the structure of the nanolayered material. In some embodiments, preferred polysaccharide dispersants include dextran (e.g., dextran), carboxymethyl dextran (e.g., carboxymethyl dextran), carboxymethyl dextran salts (e.g., sodium carboxymethyl dextran, such as sodium carboxymethyl dextran), carboxymethyl chitosan, carboxymethyl chitosan salts (e.g., sodium carboxymethyl chitosan), or combinations thereof.

[0019] In some embodiments, the weight-average molecular weight of the polysaccharide dispersant is preferably from 19 kDa to 300 kDa, such as 19 kDa, 50 kDa, 100 kDa, 150 kDa, 200 kDa, 250 kDa, or 300 kDa, more preferably from 100 kDa to 300 kDa, to avoid excessively large molecular weight which may reduce water solubility and excessively small molecular weight which may reduce the number of functional groups adsorbed on the nanolayered material. In some embodiments, the dispersion degree of the polysaccharide dispersant is preferably from 1.1 to 1.5, such as 1.1, 1.2, 1.3, 1.4, or 1.5, to have a sufficiently uniform monomer dispersion to uniformly disperse the nanolayered material and avoid precipitation. In some embodiments, the proportion of linearly bonded monomers in the polysaccharide dispersant is preferably 92.5% to 100%, such as 92.5%, 95%, 97.5% or 100%, and the proportion of branched bonds is preferably 0% to 7.5%, such as 0%, 2.5%, 5% or 7.5%, to disperse the nanolayered material with a preferred polymer configuration.

[0020] In some embodiments, the preferred polysaccharide dispersant includes carboxymethyl dextran, carboxymethyl dextran salts, carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof. In some embodiments, when the polysaccharide dispersant includes carboxymethyl dextran, carboxymethyl dextran salts, carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof, the 1H NMR spectrum (using D₂O as solvent) of the polysaccharide dispersant preferably includes characteristic peaks between 3.90 ppm and 4.45 ppm, for example, 3.90 ppm, 4.00 ppm, 4.10 ppm, 4.15 ppm, 4.20 ppm, 4.30 ppm, or 4.45 ppm, to ensure that a sufficient amount of carboxymethyl and / or carboxymethyl salts are present as hydrophilic and / or charged groups to disperse and adsorb the nanolayered material. In some embodiments, when the polysaccharide dispersant includes carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof, the 1H NMR spectrum of the polysaccharide dispersant (using D₂O as solvent) preferably includes characteristic peaks between 3.05 ppm and 3.60 ppm, such as 3.05 ppm, 3.15 ppm, 3.30 ppm, 3.40 ppm, 3.50 ppm, or 3.60 ppm, to ensure that a sufficient amount of carboxymethyl and / or carboxymethyl salts are present as hydrophilic and / or charged groups to disperse and adsorb the nanolayered material. In some embodiments, when the polysaccharide dispersant includes carboxymethyl dextran, carboxymethyl dextran salts, carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof, the carbon NMR spectrum (using D₂O as solvent) of the polysaccharide dispersant preferably includes characteristic peaks between 160 ppm and 190 ppm, such as 160 ppm, 165 ppm, 170 ppm, 175 ppm, 180 ppm, 185 ppm, or 190 ppm, to ensure that a sufficient amount of carboxymethyl and / or carboxymethyl salts are present as hydrophilic and / or charged groups to disperse and adsorb the nanolayered material. In some embodiments, when the polysaccharide dispersant includes carboxymethyl dextran, carboxymethyl dextran salts, carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof, the Fourier transform infrared spectrum of the polysaccharide dispersant preferably includes characteristic peaks between 1500 cm⁻¹ and 1650 cm⁻¹ (e.g., 1500 cm⁻¹, 1550 cm⁻¹, 1600 cm⁻¹, or 1650 cm⁻¹) and between 1380 cm⁻¹ and 1450 cm⁻¹ (e.g., 1380 cm⁻¹, 1400 cm⁻¹, 1420 cm⁻¹, or 1450 cm⁻¹) to ensure that a sufficient number of carboxymethyl and / or carboxymethyl salts are present as hydrophilic and / or charged groups to disperse and adsorb the nanolayered material.In some embodiments, when the polysaccharide dispersant includes carboxymethyl dextran salts, carboxymethyl chitosan salts, or combinations thereof, the polysaccharide dispersant forms microcells in water, and the particle size (or diameter) of the microcells is preferably 50 nanometers to 130 nanometers, for example 50 nanometers, 60 nanometers, 80 nanometers, 90 nanometers, 120 nanometers, or 130 nanometers, to ensure that a sufficient number of carboxymethyl salts not only act as hydrophilic and / or charged groups to disperse and adsorb the nanolayered material, but also form microcells of the corresponding size due to sufficient electrostatic forces. In some embodiments, when the polysaccharide dispersant includes carboxymethyl dextran salts, carboxymethyl chitosan salts, or combinations thereof, the surface of the polysaccharide dispersant in water is negatively charged, and the zeta potential is preferably -20 mV to -55 mV, for example -20 mV, -25 mV, -35 mV, -40 mV, -45 mV, or -55 mV, to ensure that there is a sufficient quantity of carboxymethyl salts to not only make the surface of the polysaccharide dispersant in water negatively charged but also to have a sufficiently large absolute value of the zeta potential to prevent the nanolayered materials in the water from easily precipitating due to aggregation.

[0021] In some embodiments, the polysaccharide-containing dispersants described above, including carboxymethyl dextran, carboxymethyl dextran salts, carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof, can be prepared from a precursor polysaccharide compound via an optional operation 1001 including a carboxymethylation process (however, the polysaccharide-containing dispersants of this disclosure are not limited to being prepared by optional operation 1001; any polysaccharide-containing dispersant having the characteristics described above is a polysaccharide-containing dispersant to be covered by this disclosure). Therefore, method 100 may further include performing the optional operation 1001 for preparing the polysaccharide-containing dispersant prior to operation 101. In some embodiments, optional operation 1001 includes dissolving the precursor polysaccharide compound in an organic solvent (e.g., isopropanol) to form a first solution, wherein the organic solvent facilitates subsequent reactions; adding an alkaline solution (e.g., a 40% aqueous sodium hydroxide solution) to the first solution to form a second solution, wherein the active groups (e.g., hydroxyl (-OH), amino groups (e.g., -NH₂), or combinations thereof) on the precursor polysaccharide compound are deprotonated to facilitate the grafting of carboxymethyl groups in the subsequent carboxymethylation process; and adding methyl chloroacetate to the second solution to form a third solution, wherein carboxymethyl groups are grafted onto the deprotonated active groups to form a polysaccharide dispersant comprising carboxymethyl dextran, carboxymethyl chitosan, or combinations thereof. In some embodiments, optional operation 1001 further includes adding an alkaline salt solution (e.g., a 40% aqueous sodium hydroxide solution) to the third solution after the carboxymethylation process to carry out a hydrolysis reaction to form a polysaccharide dispersant further comprising carboxymethyl dextran salts, carboxymethyl chitosan salts, or combinations thereof. In some embodiments, the degree of substitution of the active group on the precursor polysaccharide compound with carboxymethyl groups is at least 0.75, or more preferably at least 0.80, to ensure that the polysaccharide dispersant has a sufficient number of hydrophilic and / or charged carboxymethyl groups or carboxymethyl salts to help assist the precursor bulk material in forming nanolayers in water and stabilize the structure of the nanolayers in water.

[0022] In some embodiments, the precursor polysaccharide compound includes dextran (e.g., dextran), chitosan, or a combination thereof, wherein in some embodiments, the dextran is used directly as a polysaccharide-containing dispersant without optional operation 1001. In some embodiments, regardless of whether the dextran is used as a precursor polysaccharide compound or a polysaccharide-containing dispersant, when the dextran is dextran, it preferably has the structure of the following formula (1): Formula (1), wherein the dashed lines indicate the connection of monomers, the monomers are glucose monomers, and the monomers are connected by linear α-1,6 glycosidic bonds via C1→C6 on the sugar ring and by branched α-1,3 glycosidic bonds via C1→C3 on the sugar ring. In some embodiments, chitosan is insoluble in water and has the structure of formula (2): Formula (2), where the dashed lines indicate the connection of monomers, which are randomly distributed aminoglucose monomers and N-acetylglucosamine monomers, and the monomers are linked by linear β-1,4 glycosidic bonds on the sugar ring via C1→C4. In some embodiments, the glucan in the precursor polysaccharide compound can be a natural glucan, such as natural dextran from dental plaque. In some embodiments, the chitosan in the precursor polysaccharide compound can be a natural chitosan, such as that from crustaceans. When the precursor polysaccharide compound is derived from a natural polymer, the polysaccharide dispersant is made from the natural polymer and has structural features based on the natural polymer, thus the process is not only more environmentally friendly, but may also result in products that are more biodegradable, less biotoxic, and more biocompatible.

[0023] In some embodiments, when the polysaccharide dispersant is prepared by optional operation 1001 from formula (1), the carboxymethyl groups in the carboxymethylation process are grafted onto the active groups on C2, C3, C4, or combinations thereof on the sugar ring of formula (1). Therefore, those skilled in the art will understand that the structure of the polysaccharide dispersant includes the substitution of -OH groups on C2, C3, C4, or combinations thereof on the sugar ring of formula (1) with -OCH2COOH or salts of -OCH2COOH (e.g., -OCH2COONa). It should be noted that this disclosure does not limit the polysaccharide dispersant to be prepared by optional operation 1001. As long as the compound has formula (1) and the -OH groups on C2, C3, C4, or combinations thereof on the sugar ring are substituted with -OCH2COOH or salts of -OCH2COOH, it is a polysaccharide dispersant to be covered by this disclosure. In some embodiments, when the polysaccharide dispersant is made from formula (2) via optional operation 1001, the carboxymethyl groups in the carboxymethylation process are grafted onto the active groups on C2, C3, C6, or combinations thereof on the sugar ring of formula (2). Therefore, those skilled in the art will understand that the structure of the polysaccharide dispersant includes the substitution of -OH and / or -NH2 on C2, C3, C6, or combinations thereof on the sugar ring of formula (2) with salts of -OCH2COOH, -OCH2COOH (e.g., -OCH2COONa), -NHCH2COOH, -N(CH2COOH)2, -NHCH2COOH (e.g., -NHCH2COONa), or -N(CH2COOH)2 (e.g., -N(CH2COONa)2). It should be noted that this disclosure does not limit the polysaccharide dispersant to be made by optional operation 1001. As long as the compound has formula (2) and the -OH and / or -NH2 on C2, C3, C6, or combinations thereof on the sugar ring are replaced by -OCH2COOH, the salt form of -OCH2COOH, -NHCH2COOH, -N(CH2COOH)2, the salt form of -NHCH2COOH, or the salt form of -N(CH2COOH)2, it is a polysaccharide dispersant to be covered by this disclosure.

[0024] In some embodiments, the precursor bulk material preferably includes graphite, graphene, boron nitride (e.g., hexagonal boron nitride), tungsten disulfide, molybdenum disulfide, tungsten diselenide, molybdenum diselenide, molybdenum distelluride, or combinations thereof, to correspondingly form graphite nanolayers, graphene nanolayers, boron nitride nanolayers (e.g., hexagonal boron nitride nanolayers), tungsten disulfide nanolayers, molybdenum disulfide nanolayers, tungsten diselenide nanolayers, molybdenum diselenide nanolayers, molybdenum distelluride nanolayers, or combinations thereof, having a variety of applications in operation 102. In some embodiments, the precursor bulk material is a micron-sized precursor bulk material, for example, with a length, width, and thickness independently ranging from 0.5 microns to 15 microns, such as 0.5 microns, 1 micron, 2 microns, 5 microns, 10 microns, or 15 microns.

[0025] In some embodiments, the weight ratio or concentration ratio of the polysaccharide dispersant to the precursor bulk material in the first mixed aqueous solution 200 is preferably 0.001:1 to 1.2:1, for example 0.001:1, 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.5:1, 0.9:1 or 1.2:1, with a preference for 0.01 to 0.9:1, to avoid insufficient polysaccharide dispersant which may fail to assist the precursor bulk material in forming nanolayered materials and / or stabilize the nanolayered materials in water to prevent aggregation, and to avoid excessive polysaccharide dispersant which may fail to stabilize the nanolayered materials in water for a long time due to polymer characteristics. The aforementioned weight ratio or concentration ratio also helps the precursor bulk material form nanolayered materials with sufficient yield or solid content and / or expected size (see the following description of nanolayered materials for details, and the absorption spectra of the examples demonstrate that the weight ratio or concentration ratio helps to affect the size of the nanolayered materials). In some embodiments, the concentration of the polysaccharide dispersant in the first mixed aqueous solution 200 is preferably from 0.005 mg / mL to 10 mg / mL, for example, 0.005 mg / mL, 0.01 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 3 mg / mL, 7 mg / mL, or 10 mg / mL. This is to avoid insufficient polysaccharide dispersant, which may fail to assist the precursor bulk in forming nanolayered materials and / or stabilize the nanolayered materials from agglomeration in water, and to avoid excessive polysaccharide dispersant, which may prevent the nanolayered materials from agglomerating in water for an extended period due to polymer properties. In some embodiments, the solvent in the first mixed aqueous solution 200 substantially consists only of water and does not include organic solvents and / or is an acidic solution.

[0026] Next, operation 102 is described, in which the first mixed aqueous solution 200 is ultrasonically oscillated to form a second mixed aqueous solution 300, wherein the precursor bulk material is formed into a nano-layered material with a size smaller than that of the precursor bulk material. The bubbles generated by the ultrasonic oscillation expand in the solution due to low wave pressure and then burst due to high wave pressure, thus generating a high-energy cavitation effect to impact the precursor bulk material in the solution to form a nano-layered material with a smaller size and a layered structure. A polysaccharide dispersant is adsorbed onto the nano-layered material to prevent the nano-layered material from re-aggregating and to uniformly disperse the nano-layered material in the aqueous solution, and to further promote the exfoliation of the precursor bulk material into the nano-layered material. In some embodiments, the layered structure of the nanolayered material is a single layer or a multilayered stacked structure, for example, the average number of layers is preferably less than 10 layers and greater than or equal to 1 layer, which helps to increase the active sites on the nanolayered material and thus improve the applicability of the nanolayered material, wherein the polysaccharide dispersant is adsorbed on the surface of the layers and / or between the layers. In some embodiments, the thickness of the nanolayered material is preferably less than 10 nanometers and greater than or equal to 0.25 nanometers, for example less than 10 nanometers and greater than or equal to 0.4 nanometers, and the thickness of each layer is preferably from 0.25 nanometers to 1 nanometer, for example 0.25 nanometers, 0.4 nanometers, 0.5 nanometers, 0.8 nanometers or 1 nanometer, so that the energy level range corresponding to the size of the nanolayered material may have a better and / or wider range of applications, for example, it can be used as a photocatalyst in the following examples. In some embodiments, the length of the nanolayered material is preferably 50 nm to 400 nm, such as 50 nm, 70 nm, 100 nm, 200 nm, 300 nm, or 400 nm, and the width is preferably 50 nm to 300 nm, such as 50 nm, 70 nm, 100 nm, 200 nm, or 300 nm, so that the energy level range corresponding to the size of the nanolayered material may have a better and / or wider range of applications. In some embodiments, the nanolayered material is non-covalently bonded to the polysaccharide dispersant. In some embodiments, the total oscillation time of the ultrasonic oscillation is preferably at least 25 minutes and less than 60 minutes, such as at least 30 minutes and less than 60 minutes, to potentially effectively perform liquid-phase exfoliation of the precursor bulk material. In some embodiments, the ultrasonic oscillation power is preferably from 500 W to 1000 W, such as 500 W, 600 W, 700 W, 800 W, 900 W, or 1000 W, to potentially effectively perform liquid-phase stripping of the precursor material. In some embodiments, the ultrasonic oscillation frequency is preferably from 5 kHz to 35 kHz, such as 5 kHz, 10 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, or 35 kHz, to potentially effectively perform liquid-phase stripping of the precursor material.In some embodiments, ultrasonic oscillation is performed by cycling through pulses providing ultrasound for several seconds (e.g., less than 10 seconds) and pulses providing ultrasound for several seconds (e.g., less than 10 seconds) to potentially effectively perform liquid-phase exfoliation of the precursor material. In some embodiments, ultrasonic oscillation is performed by placing the first mixed aqueous solution 200 in an ice-water bath (e.g., water containing ice or at approximately 4 °C) to avoid excessive energy from the ultrasonic oscillation causing a reduction in the water content of the first mixed aqueous solution 200. In some embodiments, after performing operation 102, the second mixed aqueous solution 300 has a high solids content of the nanolayered material, for example, from 0.10 mg / mL to 2.50 mg / mL, such as 0.10 mg / mL, 0.30 mg / mL, 0.40 mg / mL, 1.00 mg / mL, 1.50 mg / mL, 2.20 mg / mL, or 2.50 mg / mL, to ensure a sufficient quantity of nanolayered material for subsequent applications. In some embodiments, the formation of nanolayered materials from precursor bulk materials in operation 102 has a high yield, for example, at least 10% to 35%. In some embodiments, the solvent in the second mixed aqueous solution 300 substantially consists only of water and does not include organic solvents and / or is an acidic solution.

[0027] In some embodiments, method 100 further includes an optional operation 1002 of centrifuging the second mixed aqueous solution 300 or an optional operation 1003 of vacuum filtration to separate the nanolayered material from any remaining precursor bulk material. In some embodiments, the centrifugation speed is preferably from 2000 rpm to 10000 rpm, such as 2000 rpm, 3000 rpm, 5000 rpm, 7000 rpm, 9000 rpm, or 10000 rpm. In some embodiments, centrifugation includes performing a first centrifugation followed by a second centrifugation, wherein the speed of the second centrifugation (e.g., 6000 rpm to 10000 rpm) is greater than the speed of the first centrifugation (e.g., 2000 rpm to 6000 rpm) to obtain a more homogeneous nanolayered material to enhance the activity of the nanolayered material. In some embodiments, method 100 further includes an optional operation 1004, following optional operation 1002 or optional operation 1003, to freeze-dry the supernatant after centrifugation or the solution after vacuum filtration, in order to dry and preserve the nanolayered material. In some embodiments, the nanolayered material preserved via optional operation 1004 can be easily restored to its state in the second mixed aqueous solution 300 by resolution in water after long-term preservation, without further operations such as ultrasonic vibration.

[0028] The following detailed embodiments are provided to enable those skilled in the art to better understand the present disclosure. The provision of detailed embodiments is not intended to limit the scope of the present disclosure to the description of the embodiments.

[0029] Experiment 1: Preparation of sodium carboxymethyl dextran. 2.5 g of dextran (e.g., dextran) and 30 mL of isopropanol were mixed in a round-bottom flask and stirred at room temperature for 1 hour. 10 mL of 40% sodium hydroxide aqueous solution was added to the round-bottom flask, and the flask was heated and stirred at 70 °C for 1 day under nitrogen purging. After the reaction was complete, 10 mL of methyl chloroacetate and 20 mL of isopropanol were added to the round-bottom flask, and the flask was heated and stirred at 70 °C for 1 day under nitrogen purging. After the reaction was complete, the precipitate was washed out using a Buchner funnel and 5C filter paper. The filter cake formed by the precipitate was then placed in an oven for 1 day to remove residual solvent. The dried sample was then dissolved completely in 55 mL of 40% sodium hydroxide aqueous solution and stirred at room temperature for 1 day. Next, the sample was dialyzed for two days using a dialysis bag with a molecular weight cutoff of 25 kDa to remove residual sodium hydroxide and compounds with lower molecular weights. After dialyzing, the sample was frozen in liquid nitrogen, then freeze-dried to completely remove water, and finally placed in a vacuum oven for one day to ensure complete solvent removal. The final yield of the white, fluffy sodium carboxymethyl dextran was 77.28%. Sodium carboxymethyl dextran is normally stored in sealed sample vials in a desiccator.

[0030] Experiment 2: 1H NMR spectrum of sodium carboxymethyl dextran. The chemical structure of sodium carboxymethyl dextran from Experiment 1 was analyzed using 1H NMR spectroscopy and compared with the chemical structure of the dextran before the formation of sodium carboxymethyl dextran. The solvent was D₂O. When the dextran used in Experiment 1 was dextran, the comparison of the 1H NMR spectra before and after dextran carboxymethylation and sodium salt formation is shown in Figure 3. In the 1H NMR spectrum at the top of Figure 3, the hydrogen (H1) signal at the C1 position of the dextran sugar ring is located at 4.93 ppm and corresponds to the signal at the straight chain of the monomer connected by α-1,6 glycosidic bonds. The hydrogen (H2 to H6) signals at the C2 to C6 positions of the sugar ring are between 3.43 ppm and 4.03 ppm. The slight peak at 5.28 ppm corresponds to the signal at the branched chain of the monomer connected by α-1,3 glycosidic bonds (not shown in the chemical structure diagram of Figure 3). Therefore, by integrating and comparing the peaks at 4.93 ppm and 5.28 ppm, it can be seen that the branched chain ratio in the monomer bond is about 5% and the straight chain ratio is about 95%. In the proton NMR spectrum below Figure 3, the hydrogen (H1') signal at the C1' position of the sugar ring of dextran sodium after carboxymethylation and sodium salt formation is located at 5.11 ppm. However, there may still be monomers that have not been successfully grafted with carboxymethyl groups, which have the same signal as dextran at 4.93 ppm (labeled as H1). In addition, the hydrogen (H2' to H6') signals at the C2' to C6' positions of the sugar ring are similar to those of dextran, located between 3.30 ppm and 4.08 ppm. The signal between 4.08 ppm and 4.38 ppm (labeled as A) comes from the hydrogen signal on the methyl group (-CH 2) on the carboxymethyl group in the sodium salt form. Since the carboxymethyl group can be grafted onto C2', C3', C4', or combinations thereof (not all are shown in the chemical structure diagram in Figure 3), the peak shape between 4.08 ppm and 4.38 ppm shows a broad distribution. The proportion, or degree of substitution, of successfully grafted carboxymethyl monomers can be obtained by integrating the signal labeled A in the 1H NMR spectrum of sodium carboxymethyl dextran, dividing by 2, and then dividing by the sum of the integrals of the signals labeled H1 and H1'. The degree of carboxymethyl substitution of sodium carboxymethyl dextran obtained in Experiment 1 is approximately 0.86, or the proportion of monomers with carboxymethyl groups in sodium carboxymethyl dextran is approximately 0.86% of all monomers.

[0031] Experiment 3: Preparation of Tungsten Disulfide Nanolayered Material First, referring to Examples 1 to 6 in Table 1, a first mixed aqueous solution with different weight ratios or concentration ratios of sodium carboxymethyl dextran to tungsten disulfide precursor bulk material was prepared. Specifically, sodium carboxymethyl dextran (e.g., prepared from dextran anhydride) and 5 mg / mL tungsten disulfide precursor bulk material were added to 30 mL of water according to Examples 1 to 6 in Table 1. Next, the first mixed aqueous solution was ultrasonically vibrated in an ice-water bath using a probe-type ultrasonic vibrator (700 W, 20 kHz, and a cycle of pulse on for 4 seconds followed by 3 seconds off, continuing until the total pulse on time was 30 minutes) to form a second mixed aqueous solution, wherein the second mixed aqueous solution included tungsten disulfide nanolayered material, and each layer of the nanolayered material was well separated by sodium carboxymethyl dextran. Please refer to Table 1 for the solid content of the tungsten disulfide nanolayered material in the second mixed aqueous solution and its yield compared to the tungsten disulfide precursor bulk material content in the first mixed aqueous solution. The second mixed aqueous solution can be further centrifuged at 4000 rpm for 15 minutes to separate the tungsten disulfide precursor bulk material that is too large to form the expected nanolayered material from the supernatant. The supernatant can be further frozen with liquid nitrogen and then preserved as a solid sample after removing water using a freeze dryer.

[0032] Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Sodium carboxymethyl dextran concentration (mg / mL) 0.01 0.1 0.5 1 2 5 Tungsten disulfide Precursor block concentration (mg / mL) 5 5 5 5 5 5 Sodium carboxymethyl dextran and tungsten disulfide Forward block weight ratio or concentration ratio 0.002:1 0.02:1 0.1:1 0.2:1 0.4:1 1:1 Tungsten disulfide nano-layered materials Solid content (mg / mL) 0.52 1.48 1.57 1.23 1.27 1.02 Tungsten disulfide nano-layered materials Yield (%) 0.52 / 5 *100% =10.4 1.48 / 5 *100% =29.6 1.57 / 5 *100% =31.4 1.23 / 5 *100% =24.6 1.27 / 5 *100% =25.4 1.02 / 5 *100% =20.4

[0033] Experiment 4: Interfacial Potential Analysis of the Second Mixed Aqueous Solution The interfacial potentials of the second mixed aqueous solutions obtained in Examples 1 to 6 in Experiment 3 were compared with those of the sodium carboxymethyl dextran aqueous solution excluding tungsten disulfide nanolayered material. Table 2 shows that the sodium carboxymethyl dextran in the sodium carboxymethyl dextran aqueous solution carries a negative surface charge, and its good hydrophilicity due to the presence of carboxymethyl groups in sodium salt form enhances its stability in water, resulting in an interfacial potential of approximately -34.07 mV. The second mixed aqueous solutions of Examples 1 to 6 also have negative interfacial potentials due to the inclusion of sodium carboxymethyl dextran, indicating that the solute surface is also substantially negatively charged. Furthermore, the absolute values ​​of the interfacial potentials of the second mixed aqueous solutions of Examples 1 to 6 are all around 30 mV or higher, indicating that the second mixed aqueous solutions of Examples 1 to 6 also have good stability in water. Since Example 1 contains less sodium carboxymethyl dextran, the absolute value of the interfacial potential of Example 1 is smaller than that of Examples 2 to 6, suggesting potentially poorer stability in water. The second mixed aqueous solutions of Examples 1 to 6 were further observed after prolonged standing to determine if precipitation occurred. Referring to Table 2, Examples 2 to 6 exhibited high stability in water and did not completely precipitate even after at least 30 days. However, Example 6 may have shown partial precipitation due to a higher content of sodium carboxymethyl dextran polymer. Example 1, with a lower content of sodium carboxymethyl dextran, may have had a poorer effect on separating the nanolayered materials, resulting in complete precipitation starting on day 5. Furthermore, Example 3 showed the best stability in water, remaining precipitate-free for up to 270 days. In addition, the second mixed aqueous solutions of Examples 1 to 6 not only exhibited high stability in water, but the solid samples formed after centrifugation and freeze-drying in Experiment 3 could also be resoluble in water. After five cycles of freeze-drying and resolvation in water, they still possessed interface potentials similar to those in Table 2, indicating that the nanolayered materials formed in Examples 1 to 6 also had high processability.

[0034] Table 2 Sodium carboxymethyl dextran Aqueous solution Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Interfacial potential (mV) -34.07 -23.88 -34.98 -37.10 -30.01 -33.23 -39.46 Leave for 1 day N / A Unsettled Unsettled Unsettled Unsettled Unsettled part sediment Leave for 5 days N / A part sediment Unsettled Unsettled Unsettled Unsettled part sediment Store for 30 days N / A completely sediment Unsettled Unsettled Unsettled Unsettled part sediment

[0035] Experiment 5: Electron Micrographs of Tungsten Disulfide Nanolayers The size and morphology of the tungsten disulfide nanolayers obtained in Experiment 3 were analyzed using electron microscopy and compared with the size and morphology of the tungsten disulfide precursor block before the formation of the tungsten disulfide nanolayers. In Figure 4A, the tungsten disulfide precursor block has a near-hexagonal plate-like structure with a length of approximately 3 to 10 micrometers, a width of approximately 3 to 10 micrometers, and a thickness of approximately 1 micrometer. In Figure 4B, the morphology of the tungsten disulfide nanolayered material is a small, stacked structure compared to the tungsten disulfide precursor bulk material. It has a length of about 200 to 350 nanometers, a width of about 150 to 250 nanometers, and a thickness of about 6 to 8 nanometers. The average number of layers is about 5 to 7, and the thickness of each layer is about 0.7 nanometers.

[0036] Experiment 6: Absorption Spectra of Tungsten Disulfide Nanolayered Materials. The absorption spectra of the tungsten disulfide nanolayered materials obtained from Examples 1 to 6 in Experiment 3 are shown in Figure 5. Each includes characteristic peaks located between 627 nm and 635 nm, 528 nm, and 456 nm. The characteristic peak located between 627 nm and 635 nm blue-shifts towards shorter wavelengths as the concentration or weight of sodium carboxymethyl dextran added during the formation of the tungsten disulfide nanolayered materials in Experiment 3 increases. According to quantum effects, this indicates that the size of the tungsten disulfide nanolayered materials also decreases as the concentration or weight of sodium carboxymethyl dextran added in Experiment 3 increases.

[0037] Experiment 7: Application of Photocatalytic Degradation of Dyes The tungsten disulfide nanolayered material obtained in Experiment 3 was used as a catalyst for the degradation of methyl orange dye, and compared with the degradation of methyl orange dye using tungsten disulfide precursor bulk material as a catalyst. In Figure 6, when no catalyst was used, the degradation efficiency of methyl orange dye (the proportion of dye degraded per unit time) was almost 0%. When tungsten disulfide precursor bulk material was used as a catalyst, the degradation efficiency of methyl orange dye increased. When tungsten disulfide nanolayered material was used as a catalyst, due to its smaller size and more active sites, the degradation efficiency of methyl orange dye was significantly increased compared to using tungsten disulfide precursor bulk material, even reaching 100% degradation efficiency in a short time of 120 minutes.

[0038] Experiment 8: Application of Dye Adsorption The aqueous solution of tungsten disulfide nanolayered material and sodium carboxymethyl dextran (e.g., the second mixed aqueous solution or the aqueous solution of the solid sample after centrifugation and freeze-drying reconstituted in water) from Experiment 3 was used as an adsorbent to adsorb methylene blue dye, and compared with the adsorption of methylene blue dye using an aqueous solution of tungsten disulfide precursor bulk material as an adsorbent. In Figure 7, because the aqueous solution containing tungsten disulfide nanolayered material and sodium carboxymethyl dextran makes the solute surface negatively charged (see Experiment 4), it has a better adsorption efficiency (the proportion of dye adsorbed per unit time) compared to the aqueous solution of tungsten disulfide precursor bulk material when adsorbing cationic methylene blue dye. For example, it rapidly adsorbs 85.9% of the methylene blue dye within 10 minutes, with an adsorption rate greater than 7 times and an adsorption amount greater than 3 times compared to the aqueous solution of tungsten disulfide precursor bulk material.

[0039] Experiment 9: Preparation of Graphite and Hexagonal Boron Nitride Nanolayered Materials Experiment 3 was repeated, but the tungsten disulfide precursor was replaced with graphite precursor and hexagonal boron nitride precursor, respectively, to obtain graphite nanolayered materials (corresponding to Example 7) and hexagonal boron nitride nanolayered materials (corresponding to Example 8), respectively. Specifically, in Experiment 9, the weight ratio or concentration ratio of sodium carboxymethyl dextran to graphite precursor in the first mixed aqueous solution and the weight ratio or concentration ratio of sodium carboxymethyl dextran to hexagonal boron nitride precursor in the first mixed aqueous solution were the same as in Example 3 (0.1:1). The operation of ultrasonic oscillation to form the second mixed aqueous solution was the same as in Experiment 3. The solid content of the obtained nanolayered materials and the yield compared to the precursor content in the first mixed aqueous solution are shown in Table 3. The second mixed aqueous solution can be centrifuged or freeze-dried again as in Experiment 3.

[0040] Table 3 Example 7 Example 8 Precursor Block graphite Hexagonal boron nitride Solid content of layered nanomaterials (mg / mL) 0.89 0.69 Yield of nano-layered materials (%) 16.8 13.8

[0041] Experiment 10: Preparation of Sodium Carboxymethyl Chitosan 2.5 g of chitosan was added to 30 mL of isopropanol and stirred at room temperature for 1 hour. Then, 10 mL of a 40 wt% sodium hydroxide aqueous solution was added, and the mixture was stirred at room temperature for another 12 hours. Next, 10 mL of methyl chloroacetate and 10 mL of isopropanol were added, and the mixture was stirred at 65 °C under nitrogen for 4 hours. The mixture was then filtered under vacuum, and the pale yellow solid remaining on the filter paper was placed in a vacuum oven for 24 hours to remove residual solvent. The dried solid was added to 80 mL of a 40 wt% sodium hydroxide aqueous solution and stirred at room temperature for 18 hours, at which point the solution appeared as a pale yellow colloidal substance. After stirring, 100 mL to 150 mL of deionized water was added, and dialysis was performed using a dialysis bag. After dialysis, the mixture was freeze-dried. After drying, a white, spongy solid sodium carboxymethyl chitosan sample was obtained.

[0042] Experiment 11: Preparation of Molybdenum Disulfide Nanolayered Material First, referring to Examples 9 to 11 in Table 4, a first mixed aqueous solution with different weight ratios or concentration ratios of sodium carboxymethyl chitosan and molybdenum disulfide precursor blocks was prepared. Next, the first mixed aqueous solution was ultrasonically agitated for 30 minutes using a probe-type ultrasonic nanodispersant to form a second mixed aqueous solution, wherein the second mixed aqueous solution included molybdenum disulfide nanolayered material, and each layer of the nanolayered material was well separated by sodium carboxymethyl chitosan. The solid content of the molybdenum disulfide nanolayered material in the second mixed aqueous solution and the interface potential of the second mixed aqueous solution are shown in Table 4. The second mixed aqueous solutions of Examples 9 to 11, due to the inclusion of sodium carboxymethyl chitosan, have a negative interface potential with an absolute value near or above 30 mV, indicating that the solute surface is substantially negatively charged and the solute has high stability in water. Referring to Figure 8, the transmittance of the second mixed aqueous solution of Examples 9 to 11 to 500 nm light over time was measured and compared with the aqueous solution of molybdenum disulfide precursor block excluding sodium carboxymethyl chitosan. Higher transmittance indicates lower stability of the solute in water, precipitation at the bottom of the solution and gradual clarification at the top. In Figure 8, the aqueous solution of molybdenum disulfide precursor block, lacking sodium carboxymethyl chitosan, caused rapid aggregation and precipitation of the molybdenum disulfide precursor block, achieving 100% transmittance within 5 days. In Example 11, the higher transmittance may be due to partial precipitation caused by the higher amount of sodium carboxymethyl chitosan polymer. In Examples 9 and 10, no precipitation occurred within 30 days and the transmittance was approximately 0%. After forming the molybdenum disulfide nanolayered material, the second mixed aqueous solution can be centrifuged again at 4000 rpm and then at 8000 rpm to separate the molybdenum disulfide precursor block that is too large to form the expected nanolayered material from the supernatant. Alternatively, the second mixed aqueous solution can be filtered by vacuum filtration to separate the molybdenum disulfide precursor block that is too large to form the expected nanolayered material from the solution. The supernatant obtained by centrifugation or the solution obtained by vacuum filtration can be frozen with liquid nitrogen and then preserved as a solid sample after water removal by a freeze dryer.

[0043] Table 4 Example 9 Example 10 Example 11 Sodium carboxymethyl chitosan and molybdenum disulfide precursor bulk material weight ratio or concentration ratio 0.2:1 0.33:1 1:1 Molybdenum disulfide nanolayered materials Solid content (mg / mL) 0.86 0.48 0.27 Interfacial potential (mV) -46.56 -37.14 -29.03

[0044] Experiment 12: Electron Microscopic Images of Molybdenum Disulfide Nanolayers The size and morphology of the molybdenum disulfide nanolayers obtained in Experiment 11 were analyzed using electron microscopy and compared with the size and morphology of the molybdenum disulfide precursor bulk material before the formation of the molybdenum disulfide nanolayers. In Figure 9A, the molybdenum disulfide precursor bulk material exhibits an irregular aggregated morphology with a size on the micrometer scale. In Figure 9B, the morphology of the molybdenum disulfide nanolayers, compared to the morphology of the molybdenum disulfide precursor bulk material, is a small, stacked structure, approximately 100 nm in length, 100 nm in width, and 2 to 3 nm in thickness, with an average of approximately 2 to 3 layers and a thickness of approximately 0.65 nm per layer.

[0045] Experiment 13: Absorption Spectrum of Molybdenum Disulfide Nanolayer Material The absorption spectra of the molybdenum disulfide nanolayer material obtained from Experiment 11 in Examples 9 to 11 are shown in Figure 10. Each of them includes characteristic peaks located at 674 nm and 621 nm. The characteristic peaks blue shift towards shorter wavelengths as the concentration or weight of sodium carboxymethyl chitosan added during the formation of the molybdenum disulfide nanolayer material in Experiment 11 increases. According to the quantum effect, it can be seen that the size of the molybdenum disulfide nanolayer material also decreases as the concentration or weight of sodium carboxymethyl chitosan added in Experiment 11 increases.

[0046] Experiment 14: Preparation of molybdenum diselenide and tungsten disulfide nanolayered materials. Experiment 11 was repeated, but the molybdenum disulfide precursor block was replaced with molybdenum diselenide precursor block and tungsten disulfide precursor block, respectively, to obtain molybdenum diselenide nanolayered materials (corresponding to Example 12) and tungsten disulfide nanolayered materials (corresponding to Example 13), respectively. In detail, the weight ratio or concentration ratio of sodium carboxymethyl chitosan to molybdenum diselenide precursor block in the first mixed aqueous solution in Experiment 14 was 0.33:1, and the weight ratio or concentration ratio of sodium carboxymethyl chitosan to tungsten disulfide precursor block in the first mixed aqueous solution was 0.2:1. The operation of ultrasonic oscillation to form the second mixed aqueous solution was the same as in Experiment 11. The solid content of the obtained nanolayered materials and the interface potential of the second mixed aqueous solution are shown in Table 5. The second mixed aqueous solution can be centrifuged (e.g., at 4000 rpm), filtered by vacuum, or freeze-dried again, just like in Experiment 11.

[0047] Table 5 Example 12 Example 13 Precursor Block Molybdenum diselenide Tungsten disulfide The weight ratio of sodium carboxymethyl chitosan to precursor bulk material or weight ratio 0.33:1 0.2:1 Solid content of layered nanomaterials (mg / mL) 1.96 1.14 Interfacial potential (mV) -49.76 -38.94

[0048] The method disclosed herein utilizes a polysaccharide dispersant in water to assist the formation of smaller nanolayered materials from precursor bulk materials. The polysaccharide dispersant also helps maintain the structural stability and uniform dispersion of the nanolayered materials in water over a long period, preventing sedimentation. Furthermore, the nanolayered materials formed by the method disclosed herein have a low average number of layers and sufficient surface area and active sites, enabling numerous applications, such as the removal of environmentally harmful dyes. In addition, the method disclosed herein is environmentally friendly, simple to operate, low-cost, safer, and has a high yield.

[0049] This disclosure describes some embodiments in considerable detail, but other embodiments may also be feasible. Therefore, the description of embodiments in this disclosure is not intended to limit the scope and spirit of the appended claims. Modifications and alterations to this disclosure may be made by those skilled in the art without departing from the scope and spirit of this disclosure. When such modifications and alterations fall within the scope and spirit of the appended claims, this disclosure is intended to cover such modifications and alterations. [Simplified Explanation of the Diagram]

[0013] When reading the figures in this disclosure, it is recommended to understand the various aspects of this disclosure from the following text. It should be noted that, according to industry standard practice, various feature dimensions may not be drawn to scale. Figures 1 and 2 are flowcharts and schematic diagrams, respectively, of a method for forming nanolayered materials using a polysaccharide dispersant according to some embodiments. Figure 3 is a comparison of the proton NMR spectra before and after dextran carboxymethylation and sodium salt formation according to some embodiments. Figures 4A and 4B are electron microscope images of a tungsten disulfide precursor bulk material and a tungsten disulfide nanolayered material according to some embodiments, respectively. Figure 5 is an absorption spectrum of the tungsten disulfide nanolayered material according to some embodiments. Figure 6 is an efficiency graph of the degradation of methyl orange dye by the tungsten disulfide nanolayered material according to some embodiments. Figure 7 is an efficiency graph of the adsorption of methylene blue dye by an aqueous solution including tungsten disulfide nanolayered material and sodium carboxymethyl dextran according to some embodiments. Figure 8 is a graph of the change in light transmittance of a second mixed aqueous solution over time according to some embodiments. Figures 9A and 9B are electron microscope images of a molybdenum disulfide precursor bulk material and a molybdenum disulfide nanolayered material according to some embodiments, respectively. Figure 10 is an absorption spectrum of the molybdenum disulfide nanolayered material according to some embodiments. [Biomaterial Storage]

[0051] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A method for forming nanolayered materials using a polysaccharide dispersant, comprising: A polysaccharide dispersant and a precursor bulk material are mixed in water to form a first mixed aqueous solution, wherein the polysaccharide dispersant includes dextran, carboxymethyl dextran, carboxymethyl dextran salts, carboxymethyl chitosan, carboxymethyl chitosan salts, or combinations thereof, and the precursor bulk material includes graphite, graphene, boron nitride, tungsten disulfide, molybdenum disulfide, tungsten diselenide, molybdenum diselenide, molybdenum distelluride, or combinations thereof, and the nanolayered material includes a graphite nanolayered material, a graphene nanolayered material, a boron nitride nanolayered material, a tungsten disulfide nanolayered material, a molybdenum disulfide nanolayered material, and a tungsten diselenide nanolayered material. The material, a molybdenum diselenide nanolayer material, a molybdenum distellide nanolayer material, or a combination thereof, wherein the weight ratio of the polysaccharide dispersant to the precursor bulk material in the first mixed aqueous solution is 0.001:1 to 1.2:1; and the first mixed aqueous solution is subjected to ultrasonic oscillation to form a second mixed aqueous solution, wherein the polysaccharide dispersant is formed from a precursor polysaccharide compound via an operation including a carboxymethylation process, and the degree of substitution of an active group on the precursor polysaccharide compound by a carboxymethyl group is at least 0.75, and the precursor bulk material forms a nanolayer material with a size smaller than the precursor bulk material.

2. The method as described in claim 1, wherein the thickness of the nanolayered material is less than 10 nanometers, and the average number of layers of the nanolayered material is less than 10 layers.

3. The method as described in claim 1, wherein the precursor block is a one-micrometer precursor block.

4. The method as claimed in claim 1, wherein the polysaccharide dispersant is soluble in water and has at least one hydrophilic group, so as to dissolve in the second mixed aqueous solution and adsorb onto the nanolayer material.

5. The method as described in claim 1, wherein the total oscillation time of the ultrasonic oscillation is at least 25 minutes.

6. The method as described in claim 1 further includes centrifuging or vacuum filtration of the second mixed aqueous solution to separate the nanolayered material from the remaining precursor bulk material.

7. The method as claimed in claim 1, wherein the first mixed aqueous solution comprises a solvent, and the solvent does not include organic solvents and / or acidic solutions.

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