A method for preparing photoluminescent carbon nanoparticles containing diamond structure using low-rank coal

Abstract

The present invention provides a method for preparing photoluminescent carbon nanoparticles containing diamond structure by using low-rank coal, including a method for preparing carbon nanoparticles containing nano-diamond structure by using low-rank coal, characterized in that it comprises: step S1, ball-milling and sieving the low-rank coal to obtain coal powder; step S2, mixing the coal powder with a hydrogen peroxide solution in a certain proportion, stirring at a certain temperature and heating at normal pressure for reaction; step S3, filtering the solution after the reaction; step S4, drying the filtrate after the filtration to obtain carbon nanoparticles containing nano-diamond structure. The method of the present invention is simple, and the luminescent effect of the prepared carbon nanoparticles is simple and adjustable.

Description

Technical Field

[0001] The invention relates to the technical field of carbon nanomaterials, and in particular to a method for preparing photoluminescent carbon nanoparticles containing diamond structures by utilizing low-rank coal. Background Art

[0002] Nano Diamonds (NDs) are a new type of carbon nanomaterial with a size less than 100nm. They were first discovered in the 1960s. They not only have the excellent properties of diamond bulk materials such as high hardness, high elastic modulus, high thermal conductivity and low friction coefficient, but also have the advantages of low-dimensional materials, such as: small size effect, surface effect, quantum effect and structural adjustability. At the same time, the unique fluorescence properties of nano diamonds give it a broader application prospect in biomedicine, optoelectronic sensing, environmental testing and other fields.

[0003] At present, the main synthetic methods for preparing nanodiamonds include high temperature and high pressure method, detonation method, crushing method, laser shock method; other preparation methods, such as catalytic reduction method, plasma electrolysis method, chemical vapor deposition method, etc., have also been studied. The main basic principle is that under certain conditions, the graphite phase is transformed into the diamond phase.

[0004] In recent years, the research on carbon nanoparticles, especially photoluminescent carbon nanoparticles, has aroused widespread interest among scientists. However, there is little research in the prior art on how to prepare carbon nanoparticles with nanodiamond structure to form photoluminescent carbon nanoparticles with a new structure. Summary of the invention

[0005] The present invention aims to provide a method for simply preparing photoluminescent carbon nanoparticles containing nano-diamond structures. The obtained product not only realizes the controllable preparation of carbon nanoparticles containing nano-diamond structures, but also can regulate the fluorescence properties thereof.

[0006] Therefore, the present invention provides the following technical solutions:

[0007] A method for preparing carbon nanoparticles containing nano-diamond structures by using low-rank coal, characterized by comprising:

[0008] Step S1, ball-milling and sieving low-rank coal to obtain coal powder;

[0009] Step S2, mixing the coal powder and the hydrogen peroxide solution in a certain proportion, and performing a stirring and normal pressure heating reaction with condensation reflux at a certain temperature;

[0010] Step S3, filtering the solution after the reaction;

[0011] Step S4, drying the filtrate after filtration to obtain carbon nanoparticles containing nano-diamond structure.

[0012] Optionally, the low-rank coal is one or more of low-metamorphosis bituminous coal, weakly sticky coal, non-sticky coal, long flame coal, and lignite.

[0013] Optionally, an alkaline substance may be added during the stirring and normal pressure heating reaction to promote the depolymerization of the coal powder, and the alkaline substance is preferably NaOH or KOH.

[0014] Optionally, the concentration of the hydrogen peroxide solution is 10-30wt%, preferably 20wt%; the liquid-solid ratio of the hydrogen peroxide solution to the coal powder is 50:1-400:1mL / g, preferably 200:1mL / g.

[0015] Optionally, the heating reaction temperature is 40-100° C.; the heating reaction time is 3-24 h.

[0016] Optionally, the drying treatment is freeze drying at -50 to -140°C or rotary evaporation at 40 to 80°C.

[0017] Furthermore, the present invention also provides a carbon nanoparticle containing a nano-diamond structure, wherein the carbon nanoparticle exhibits the strongest excitation at 340 nm and the maximum emission wavelength is 450 nm±10 nm.

[0018] Furthermore, the present invention also provides the use of carbon nanoparticle powder containing nano-diamond structure in photovoltaic devices, biological imaging, or sensing.

[0019] The present invention selects low-rank coal as a carbon source, and directly heats and oxidizes it under hydrogen peroxide conditions under specific reaction conditions, and condenses and refluxes it during water bath stirring. During the reaction, the hydroxyl radicals generated by hydrogen peroxide destroy the weak bonds in the coal structure, thus obtaining water-soluble nanodiamonds. This method can achieve the regulation of product particle size and photoluminescence performance.

[0020] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0021] By using low-rank coal as raw material, low-quality raw materials can be fully utilized, which not only reduces the preparation cost but also effectively utilizes raw materials that are usually difficult to use to prepare high-value products. The preparation process only carries out heating, stirring, condensing and reflux reaction under normal pressure, and the preparation conditions are mild. Only using hydrogen peroxide as an oxidant can avoid environmental pollution and make the preparation process greener. The luminescence effect of carbon nanoparticles can be controlled by adjusting the heating temperature and the concentration of hydrogen peroxide (i.e., by controlling the degree of oxidation) or the concentration of later carbon nanoparticles. By adjusting the low-rank coal to lignite or low-grade bituminous coal, the luminescence effect of photoluminescent carbon nanoparticles can be controlled by adjusting the water bath heating temperature and the concentration of hydrogen peroxide (i.e., by controlling the degree of oxidation) or the concentration of later carbon dots. By using specific raw materials and matching specific process conditions, carbon nanoparticles containing nano-diamond structures are prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a flow chart for preparing photoluminescent carbon nanoparticles containing diamond structure according to the present invention;

[0024] Figure 2 The transmission electron microscope photo of the nanoparticles prepared in Example 1 of the present invention and its particle size distribution diagram;

[0025] Figure 3 TEM-EDS image of carbon nanoparticles prepared in Example 1 of the present invention;

[0026] Figure 4 TEM image of carbon nanoparticles prepared in Example 1 of the present invention;

[0027] Figure 5 The PL emission spectrum of the carbon nanoparticles prepared in Example 1 of the present invention at a concentration of 0.3 g / L;

[0028] Figure 6 PL luminescence spectrum of the carbon nanoparticles prepared in Example 1 of the present invention at a concentration of 0.15 g / L;

[0029] Figure 7 The PL emission spectrum of the carbon nanoparticles prepared in Example 1 of the present invention at a concentration of 0.07 g / L;

[0030] Figure 8These are digital photos of the luminescence phenomenon of carbon nanoparticle solutions of different concentrations under 365nm ultraviolet light conditions, wherein the concentration of (a) is 0.07g / L and the concentration of (b) is 1.5g / L. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clear, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] First, the washed long flame coal was ball-milled into powder, passed through a 200-mesh sieve, and dried overnight in an oven at 120°C. 1 g of long flame coal was weighed and placed in a 500 mL round-mouth flask, 200 mL of 20 wt% H2O2 solution was added, and the mixture was stirred and reacted for 9 h at 80°C in a water bath, and condensed and refluxed.

[0034] After the reaction is completed, wait for cooling to room temperature, filter with a 0.45 micron organic filter membrane, retain the supernatant, and successfully obtain carbon nanoparticles containing nano-diamond structure. The particle size is 1.75±1.00nm, that is, the average particle size is 1.75nm. The sample is freeze-dried or rotary evaporated to obtain a solid product.

[0035] In addition, the ultraviolet-visible light absorption spectrum of the carbon nanoparticles showed that its absorption spectrum wavelength was around 230±10nm, and the luminescence performance of the nanoparticle solution was characterized, proving that the sample obtained the strongest excitation at 340±20nm, and the emission peak in its emission spectrum was at 450±10nm; TEM image analysis of the carbon nanoparticles showed that it had a twin structure with a lattice size of 0.21nm, corresponding to the (111) or (002) crystal plane of the diamond structure, indicating that it has a diamond structure.

[0036] Table 1 Industrial analysis and chemical analysis of washed long flame coal

[0037]

[0038] Note: M, moisture; A, ash; V, volatile matter; FC, fixed carbon; ad, air-dried basis; S t，daf , dry ash-free full sulfur.

[0039] Example 2

[0040] First, the long flame coal was ball-milled into powder, passed through a 200-mesh sieve, and dried overnight in an oven at 120°C. 1g of long flame coal was weighed and placed in a 500mL round-mouth flask, 200mL of 20wt% H2O2 solution was added, and 1g of NaOH was added to promote the full depolymerization of the coal. The reaction was fully stirred in a water bath at 80°C for 6h, and condensed and refluxed.

[0041] After the reaction is completed, wait for cooling to room temperature, filter with a 0.45 micron organic filter membrane, retain the supernatant, and successfully obtain carbon nanoparticles containing nano-diamond structure. Freeze-dry or rotary evaporate the sample to obtain a solid product.

[0042] In addition, the ultraviolet visible light absorption spectrum of the carbon nanoparticles showed that its absorption spectrum wavelength was around 230±10nm, and the luminescence performance characterization of the nanoparticle solution proved that the sample obtained the strongest excitation at around 300±20nm, the emission peak in its emission spectrum was around 440±10nm, and its absolute quantum yield reached 5.6%.

[0043] Example 3

[0044] First, the long flame coal was ball-milled into powder, passed through a 200-mesh sieve, and dried overnight in an oven at 120°C. 1 g of long flame coal was weighed and placed in a 500 mL round-mouth flask, 200 mL of 20 wt% H2O2 solution was added, and the mixture was stirred and reacted for 9 h at 80°C in a water bath, and condensed and refluxed.

[0045] After the reaction is completed, wait for cooling to room temperature, filter with a 0.21 micron organic filter membrane, retain the supernatant, and successfully obtain carbon nanoparticles containing nano-diamond structure. The sample can be freeze-dried or rotary evaporated to obtain a solid product.

[0046] In addition, the carbon nanoparticles were measured by ultraviolet visible light absorption spectroscopy and the absorption spectrum wavelength was around 230±10nm. The luminescence performance of the nanoparticle solution was characterized and it was proved that the sample obtained the strongest excitation at 300±20nm, and the emission peak in its emission spectrum was at 440±10nm.

[0047] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing carbon nanoparticles containing nano-diamond structure using low-rank coal, characterized in that: include: Step S1, ball-milling and sieving low-rank coal to obtain coal powder; Step S2, mixing coal powder and hydrogen peroxide solution in a certain proportion, stirring and heating at a certain temperature and normal pressure for reaction; Step S3, filtering the solution after the reaction; Step S4, drying the filtrate after filtration to obtain carbon nanoparticles containing nano-diamond structure; The concentration of hydrogen peroxide solution is 20wt%; the liquid-solid ratio of hydrogen peroxide solution to coal powder is 200:1mL / g; The heating reaction temperature is 80°C; the heating reaction time is 6-9 h.

2. The method according to claim 1, characterized in that Low-rank coal is one or more of low-metamorphosis bituminous coal, weakly sticky coal, non-sticky coal, long flame coal, and lignite.

3. The method according to claim 1, characterized in that The stirring and normal pressure heating reaction is a stirring and heating reaction with condensation and reflux at a certain temperature; during the reaction, an alkaline substance is added to promote the depolymerization of the coal powder, and the alkaline substance is NaOH or KOH.

4. The method according to claim 1, characterized in that The drying process is freeze drying at -50 to -140°C or rotary evaporation at 40 to 80°C.

5. Carbon nanoparticles containing nano-diamond structures prepared by the method according to any one of claims 1 to 4, characterized in that: The carbon nanoparticle solution with a concentration of 0.07~0.3g / L showed the strongest excitation at 340 nm, and the maximum emission wavelength was located at 450±10 nm.

6. Use of the carbon nanoparticles containing nano-diamond structures prepared by the method according to any one of claims 1 to 4 or the carbon nanoparticles containing nano-diamond structures according to claim 5 in photovoltaic devices, biological imaging or sensing.

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