CN103833004A - Method for preparing water-soluble fluorescent carbon nanoparticle dots - Google Patents

Abstract

A method for preparing water-soluble fluorescent carbon nanoparticle dots, characterized in that: using pentosan extracted from bleached broad-leaved pulp with alkali method as raw material, after high-temperature and high-pressure hydrothermal treatment, light yellow liquid products and dark brown solids are filtered The product, in which the solid product is used as a high-performance adsorbent to adsorb heavy metal ions Pb (II) and Cd (II), the light yellow liquid product is centrifuged at high speed, the centrifugation speed and time are controlled, the insoluble solid is removed, and the unreacted sugar and dialysis bag are removed. Salt and other ingredients are then concentrated to obtain water-soluble fluorescent carbon nanoparticle dots. The main feature of this operation process is that pentosan extracted from the by-products of pulping and papermaking is used as raw material, which is environmentally friendly, cheap and easy to obtain, and the reaction does not need to add passivators such as acid-base salts. The reaction process is simple in operation and low in cost.

Description

A method for preparing water-soluble fluorescent carbon nanoparticle dots

Technical field:

The invention relates to the field of nanomaterial preparation, in particular to a method for preparing water-soluble fluorescent carbon nanoparticle dots. the

Background technique:

The annual output value of papermaking in the world reaches 400 million tons, and tens of thousands of adult wood are consumed every year, but the actual utilization rate is very low, and a large amount of raw materials become waste and are abandoned. As an important intermediate product in the papermaking process, bleached hardwood pulp has low cost and high yield, and it is rich in hemicellulose mixture, including ribose, xylose, arabinose, etc. In the actual production process, these pentosans are usually removed after treatment to further obtain high-quality paper, and the treated pentosans are directly discarded without further utilization, resulting in a large amount of waste. the

Fluorescent nanoparticles are widely used as metal probes, biomarkers, and light sensors due to their unique optical properties, excellent electrical properties, and good biocompatibility. Traditional fluorescent nanoparticles are mainly semiconductor particles, but they can release heavy metal ions such as Cd and Pb during use, making them highly toxic and unsuitable for large-scale production. Metallic fluorescent nanoparticles, such as gold and silver nanoparticles, have strong photostability and overcome toxic defects, but the cost is high, which is not conducive to wide application. the

US patent (US7829772B2) introduces a method of laser ablation of graphite powder in the presence of water vapor to obtain nano-sized carbon particles, but the particles have no fluorescent effect even after acid treatment, and then mixed with PEG _1500N After 72 hours at 120°C, carbon particles with surface passivation and a particle size distribution of 5-10 nm were obtained, showing good fluorescence effect. The fluorescent particles obtained by this method have a fluorescence efficiency of 5% to 10%. The reaction involves laser ablation, strong nitric acid treatment, and passivation with a passivating agent, which takes a long time and increases the reaction cost.

US patent (WO021620A1) introduces a method of directly burning benzene, toluene, xylene and other aromatic solvents in the air to prepare fluorescent carbon nanoparticles. The carbon particles have a wide particle size distribution of 10-60nm. Dispersed in ethanol, it has a strong fluorescence response when the excitation wavelength is 475nm, and the quantum efficiency reaches 12-13%. However, the water solubility is poor, and the required raw materials are all organic reagents, the cost is high, and the environmental load is large. the

The Chinese patent with the publication number CN103011126 introduces a preparation process of water-soluble fluorescent carbon quantum dots. In this method, glucose and dihexyl malonate are mixed, refluxed at 140-160°C and cooled to room temperature, and the product is vacuumed at 100-120°C. After drying for 2 hours, it was dissolved in distilled water, and the target fluorescent carbon dots were obtained after centrifugation and freeze-drying. The particle size of the product was 2-4nm, and the fluorescence efficiency reached 24%. Although this method improves the quantum efficiency, the organic solvent used in the reaction is expensive and the process is cumbersome. the

The Chinese patent whose publication number is CN102849724 introduces a preparation method of water-soluble carbon quantum dots. In this method, the graphite impurities produced during the preparation of single-walled carbon nanotubes by the electric arc method are added to an aqueous solution containing a surfactant to disperse and centrifuge to obtain Graphite particles with a narrow size react with a strong oxidant, and then obtain water-soluble carbon quantum dots through alkali neutralization and dialysis bag separation. Although this method obtains quantum dots with different particle sizes, the reaction involves concentrated sulfuric acid, concentrated nitric acid, high Potassium manganate and other strong oxidants will cause equipment corrosion and environmental pollution, which is not conducive to large-scale commercial production. the

The Chinese patent with the publication number CN102071019 introduces a method for preparing a water-soluble carbon nanoparticle material with fluorescent properties. The method uses aqueous glucose solution as a precursor solution, and after adding additives, 300W power is ultrasonicated for 4 to 6 hours to adjust the pH to medium. Recrystallization treatment after deactivation to obtain carbon nanoparticles. The ultrasonic method is simple to operate, but the reaction also involves a strong oxidant of hydrochloric acid, and the requirements for the reaction vessel are relatively high, which increases the reaction cost. the

The Chinese patent with the publication number CN102127431 introduces a method for making carbon quantum dots and a method for preparing photocatalysts using the quantum dots. In this method, ethanol and distilled water are mixed according to a certain volume ratio, and then an inorganic strong base is added to obtain an electrolyte solution that is put into electrolysis The tank uses graphite carbon rods as electrodes, and performs electrochemical reaction at a current density of 10-200mA/ ^cm2 for 2-4h, and finally adds a desiccant, and obtains carbon quantum dots through column chromatography. This method is performed in two steps. One electrolysis and one column chromatography separation, the reaction is complicated and the damage to the instrument is great.

In summary, traditional methods such as ion radiation, laser ablation, ultrasound, electrochemical oxidation, and combustion have high losses, complex reactions, pollute the environment, and require passivators such as strong acids and bases. The present invention uses a hydrothermal method to prepare fluorescent carbon Nanoparticles, the reaction uses water as a solvent, and is carried out under high temperature and high pressure. The conditions are mild and the equipment is easy to operate. Compared with traditional methods, the reaction temperature can be lowered and the reaction time can be shortened. It is a fast, simple and effective method for preparing fluorescent carbon nanoparticles. method, the prepared carbon nanoparticles have high fluorescence efficiency. the

Invention content:

The object of the present invention is to provide a method for preparing water-soluble fluorescent carbon nanoparticle dots. the

In order to achieve the above object, the technical scheme adopted by the present invention includes: a method for preparing water-soluble fluorescent carbon nanoparticle dots, which is characterized in that: using pentosan extracted from bleached broad-leaved pulp with alkaline method as raw material, high temperature and high pressure hydrothermal method After treatment, a light yellow liquid product and a dark brown solid product are obtained by filtration. The solid product is used as a high-performance adsorbent to adsorb heavy metal ions Pb(II) and Cd(II). The light yellow liquid product is centrifuged at high speed, and the centrifugation speed and time are controlled. Remove insoluble solids, remove unreacted sugars and salts with a dialysis bag, and then concentrate to obtain water-soluble fluorescent carbon nanoparticle dots. the

The advantages of the present invention are:

1. Using pentosan extracted from bleached broad-leaved pulp as raw material, making full use of the by-products of the paper industry, the raw material is abundant, cheap and easy to obtain. As a complex of several five-carbon monosaccharides, pentosan is environmentally friendly, natural and pollution-free. The carbonization rate is higher after heat treatment. the

2. The present invention overcomes the deficiencies in the prior art, changes the traditional production process, uses hydrothermal reaction, uses water as a solvent, does not need pretreatment of raw materials, reduces reaction temperature, shortens reaction time, mild reaction conditions, and easy process operation Simple, low production cost and high yield. the

3. The present invention simultaneously obtains solid products and liquid products. The solid products can effectively absorb heavy metal ions in sewage, and the liquid products have good fluorescence effects, increasing their market application prospects and economic benefits. the

4. In the reaction of the present invention, passivators such as acid-base salts are not added, no additional treatment is required, and the environment is not polluted. The product is water-soluble and shows sensitivity to pH. Using quinine sulfate as a reference material, the quantum The efficiency can reach 42%.

Description of drawings

Figure 1 is a transmission electron microscope image of water-soluble fluorescent carbon nanoparticle dots. the

Detailed ways:

The implementation of the present invention is described in further detail below:

A method for preparing water-soluble fluorescent carbon nanoparticle dots, characterized in that: using pentosan extracted from bleached broad-leaved pulp with alkali method as raw material, after high-temperature and high-pressure hydrothermal treatment, light yellow liquid products and dark brown solids are filtered The product, in which the solid product is used as a high-performance adsorbent to adsorb heavy metal ions Pb (II) and Cd (II), the light yellow liquid product is centrifuged at high speed, the centrifugation speed and time are controlled, the insoluble solid is removed, and the unreacted sugar and dialysis bag are removed. Salt and other ingredients are then concentrated to obtain water-soluble fluorescent carbon nanoparticle dots. the

Hereinafter, the present invention will be further described with examples, but it is not limited to any one of these examples or similar examples. the

Example 1:

Add 250ml of 1.5mol/L KOH solution to 20g of bleached broadleaf pulp with a brightness of 88%, stir and extract at room temperature for 30 hours, filter, adjust the pH of the filtrate to 2-3 with 2mol/L HCl, add ethanol to precipitate the solid, and the volume of ethanol is 3 times the volume of the liquid, the precipitate was filtered and washed to neutrality to obtain pentosan with a yield of 12.5%. the

The extracted pentosan was formulated into an aqueous solution with a concentration of 5%, and put into a polytetrafluoroethylene in a reaction kettle to ensure that the volume of the solution and the volume of the kettle were 7:8, and the temperature was raised to a target temperature of 190°C at a heating rate of 10°C/min. Constant temperature for 8 hours, cool down to room temperature, filter, collect the obtained light yellow liquid, centrifuge twice at 12000r/min to remove sediment, and dialyze the liquid for 3 days with a dialysis bag with a cutoff of 2000 to remove macromolecular products. After concentration, water-soluble fluorescent carbon nano-dots are obtained, with a particle size ranging from 10 to 50 nm (see Figure 1). the

Wash the brown solid product obtained by filtration with distilled water and 95% absolute ethanol until the filtrate is clear, and dry it in an oven at 80 °C. The obtained solid product has a spherical structure with a particle size of 150-1200 nm, and the surface contains 39.1 carboxyl functional groups. Test at room temperature The saturated adsorption values for Pb(Ⅱ) and Cd(Ⅱ) are 380.1mg/g and 100.8mg/g, respectively. the

Example 2:

Add 250ml of 3mol/L KOH solution to 20g of bleached broadleaf pulp with a brightness of 88%, stir and extract at room temperature for 25 hours, filter, adjust the pH of the filtrate to 2-3 with 2mol/L HCl, add ethanol to precipitate the solid, and the volume of ethanol is liquid 3 times the volume, the precipitate was filtered and washed to neutrality to obtain pentosan with a yield of 14%. the

The extracted pentosan was formulated into an aqueous solution with a concentration of 7%, and put into a polytetrafluoroethylene in a reaction kettle to ensure that the volume of the solution and the volume of the kettle were 9:10, and the temperature was raised to the target temperature of 240°C at a heating rate of 10°C/min. Constant temperature for 10 hours, cool down to room temperature, filter, collect the light yellow liquid obtained, centrifuge twice at 11000r/min to remove sediment, and dialyze the liquid for 3 days with a dialysis bag with a cutoff of 3000 to remove macromolecular products. After concentration, water-soluble fluorescent carbon nano-dots are obtained, and the particle size ranges from 20 to 40 nm. the

Wash the brown solid product obtained by filtration with distilled water and 95% absolute ethanol until the filtrate is clear, and dry it in an oven at 80°C. The obtained solid product has a spherical structure with a particle size of 300-900 nm, and the surface contains 36.5 carboxyl functional groups. Test at room temperature The saturated adsorption values for Pb(Ⅱ) and Cd(Ⅱ) are 353.1mg/g and 94.8mg/g, respectively. the

Claims (8)

1. prepare the method for water-soluble fluorescent carbon nano-particles point for one kind, it is characterized in that: to bleach piperylene that broad-leaved slurry alkaline process extracts as raw material, after High Temperature High Pressure hydro-thermal method is processed, filter to obtain light yellow liquid product and dark brown solid product, wherein solid product is as high-performance adsorbent Adsorption of Heavy Metal Ions Pb(II) and Cd(II), by light yellow liquid product high speed centrifugation, control centrifugal rotational speed and time, remove insoluble solids, remove the compositions such as unreacted sugar and salt with dialysis tubing, then obtain having water miscible fluorescent carbon nano-particles point through concentrating.

2. according to a kind of method of preparing water-soluble fluorescent carbon nano-particles point claimed in claim 1, it is characterized in that: the highly basic that alkaline process extracts piperylene employing is NaOH or KOH, and concentration of lye is 1.0～3.0mol/L, alkaline process extraction time is 15～30 hours.

3. according to a kind of method of preparing water-soluble fluorescent carbon nano-particles point claimed in claim 1, it is characterized in that: hydrothermal temperature is at 190～240 ℃, and the reaction times is 8～12 hours.

4. according to a kind of method of preparing water-soluble fluorescent carbon nano-particles point claimed in claim 1, it is characterized in that: the light yellow liquid product centrifugation rate of gained is 8000～15000rpm, and centrifugation time is min.

5. according to a kind of method of preparing water-soluble fluorescent carbon nano-particles point claimed in claim 1, it is characterized in that: hydro-thermal reaction material concentration is 2.5%～12.5%, solvent capacity is 9:10～3:5 with reaction capacity ratio.

6. according to a kind of method of preparing water-soluble fluorescent carbon nano-particles point claimed in claim 1, it is characterized in that: the molecular interception amount of dialysis tubing is 1000～5000.

7. according to a kind of method of preparing water-soluble fluorescent carbon nano-particles point claimed in claim 1, it is characterized in that: the fluorescence efficiency of the prepared water-soluble carbon nanoparticle point of hydrothermal method is 42.5%.

8. according to a kind of method of preparing water-soluble fluorescent carbon nano-particles point claimed in claim 1, it is characterized in that: the particle diameter of the prepared water-soluble carbon nanoparticle point of hydrothermal method is 10～40nm.

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