Method for preparing hydrophilic carbon quantum dots based on polypropylene-containing medical waste materials

Abstract

The present application relates to the technical field of carbon quantum dots, and particularly relates to a method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene. The preparation method utilizes the characteristic that PP is sensitive to ultraviolet light, and places the cleaned medical waste materials containing PP under the irradiation of an ultraviolet lamp. Under the action of ultraviolet light, heat and wet oxygen, long chains of PP are decomposed into short chains, and even into organic monomers such as acids, ketones, aldehydes and esters. Then, the decomposition products are used as raw materials to synthesize hydrophilic carbon quantum dots with a diameter of less than 5 nm through a hydrothermal method or a microwave method. The preparation method provided by the present application has the advantages of wide raw material sources (including medical waste materials), simple and controllable process, good repeatability, low cost and the like. The method not only helps to recycle the medical waste materials, but also converts the waste materials into high-value hydrophilic carbon quantum dots, which have potential market value in the fields of biological imaging and photocatalysis.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon quantum dots, and in particular to a method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene. Background Art

[0002] Carbon quantum dots are a type of zero-dimensional carbon nanomaterial with remarkable fluorescence properties. 2 and sp 3 The physical properties of carbon quantum dots (CQDs), such as fluorescence, vary significantly with size.

[0003] CQDs have the advantages of excellent optical properties, good water solubility, low toxicity, environmental friendliness, wide availability of raw materials, low cost, and good biocompatibility. Their applications cover a wide range of fields, including medical imaging, environmental monitoring, chemical sensing, catalyst preparation, and energy development. They hold particular potential in biomedical imaging, drug delivery, and photodiagnostic agents.

[0004] In recent years, polymer recycling technology has continued to develop, but the recycling of disposable medical items (such as masks) still faces challenges. The current mainstream treatment methods include:

[0005] Incineration method: It realizes energy utilization through combustion. It is easy to operate but produces toxic gases (such as dioxins) and solid residues. It requires supporting tail gas treatment equipment and is prone to secondary pollution.

[0006] Physical and mechanical method: after disinfection, it can be regenerated into mask raw materials. The process is simple, but the added value of the product is low and the resource utilization rate is insufficient.

[0007] Chemical treatment: PP is converted into high-value chemicals through pretreatment methods such as sulfonation. However, this process is complex and the chemical reagents may pollute the environment. Furthermore, due to PP's stable structure, direct carbonization is difficult to produce carbon materials, and pretreatment further increases technical difficulty and environmental risks.

[0008] If medical waste materials containing PP can be efficiently converted into CQDs, it will not only improve resource utilization but also generate significant economic and social value. Summary of the Invention

[0009] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention aims to provide a method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene.

[0010] A method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene, wherein the hydrophilic carbon quantum dots are spherical and have a diameter of less than 5 nm;

[0011] The X-ray diffraction pattern of the hydrophilic carbon quantum dots has characteristic diffraction peaks at positions of 2θ of 28.7 to 29.1 degrees and 42.7 to 43.1 degrees;

[0012] The steps include:

[0013] S100, washing medical waste materials containing polypropylene with water, drying, shearing, placing them in a sealed glass reaction vessel, introducing water-containing oxygen, and irradiating the reaction system with ultraviolet light to decompose the long chains of polypropylene in the medical waste materials, thereby obtaining a raw material;

[0014] Wet oxygen is oxygen containing water, with a water content of >1g / m 3 ;

[0015] In the process of irradiating the reaction system with ultraviolet light, the wavelength of the ultraviolet light is 310nm to 370nm, and the irradiation time is 20 to 40h;

[0016] The raw materials are organic monomers and / or oligomers containing oxygen functional groups and / or olefins;

[0017] S200, adding water to the raw materials, and synthesizing hydrophilic carbon quantum dots by hydrothermal synthesis or microwave synthesis;

[0018] The reaction temperature of the hydrothermal synthesis method is 160°C to 200°C, and the reaction time is 8 to 12 hours.

[0019] In the microwave synthesis method, microwave heating is performed with a power of 800-1200 W and the addition time is 6-10 minutes.

[0020] PP ([C3H6] n The tertiary carbon atoms in the main chain of PP readily absorb photons, inducing C-H bond cleavage to form alkyl radicals. These alkyl radicals react with oxygen to form alkoxy radicals, which are further oxidized to form oxygen-containing functional groups such as ketones, aldehydes, and carboxyls. This process breaks PP into monomers or oligomers containing olefins, ketones, aldehydes, and carboxylates. Subsequently, carbon quantum dots are prepared through polymerization between oxygen-containing functional groups via a bottom-up approach (i.e., assembling nanomaterials from molecular units). This introduces oxygen into the carbon quantum dots, imparting them with excellent hydrophilic properties.

[0021] The preparation method provided by this invention offers advantages such as a broad source of raw materials (including medical waste materials), a simple and controllable process, good reproducibility, and low cost. Furthermore, the process produces fewer byproducts that are harmful to humans or pollute the environment. This method not only facilitates the recycling of disposable medical waste materials, reducing the spread of viruses and bacteria and environmental pollution, but also converts waste into high-value hydrophilic carbon quantum dots.

[0022] Hydrophilic carbon quantum dots with a diameter of less than 5 nm have a wide range of applications due to their size-dependent optical properties, surface modifiability and low toxicity, covering the fields of biomedicine, environment and energy, optoelectronics and real technology, as well as industry and materials science.

[0023] Furthermore, the oxygen-containing functional group in step S100 includes one or more of a ketone group, an aldehyde group, a carboxyl group, a hydroxyl group and an ether bond.

[0024] Furthermore, the method further comprises the following steps of purifying the hydrophilic carbon quantum dots:

[0025] S300, filtering the aqueous solution of hydrophilic quantum dots obtained in step S200 through a 0.2-0.45 µm water filter membrane to obtain a filtrate;

[0026] S400, transferring the filtrate to a semipermeable membrane container with a molecular weight cut-off of 1000 to 3500 Da, and dialyzing the filtrate with deionized water to obtain a dialysate containing purified hydrophilic carbon quantum dots.

[0027] Furthermore, the method further comprises the following steps:

[0028] S500, freeze-drying the dialysate to obtain the hydrophilic carbon quantum dot powder.

[0029] Furthermore, the freeze-drying temperature is -84 to -94°C, and the time is 12 to 36 hours.

[0030] Furthermore, the diameter of the hydrophilic carbon quantum dots is 1.2 to 4.8 nm.

[0031] Furthermore, the diameter of the hydrophilic carbon quantum dots is 3.0 to 3.2 nm.

[0032] Furthermore, the hydrophilic carbon quantum dots have an interlayer spacing of 0.309 nm when 2θ is 28.9 degrees; and an interlayer spacing of 0.211 nm when 2θ is 42.9 degrees.

[0033] Furthermore, it is used for the recycling of medical waste materials containing polypropylene.

[0034] Furthermore, the medical waste materials containing polypropylene include one or more of disposable medical masks, medical infusion bags, disposable medical protective clothing and disposable medical examination pads.

[0035] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0036] The present invention provides a method for preparing hydrophilic carbon quantum dots from medical waste materials containing polypropylene. Utilizing the ultraviolet sensitivity of polypropylene, the cleaned PP-containing medical waste is exposed to ultraviolet light. Under the influence of ultraviolet light, heat, and moist oxygen, the long PP chains decompose into short chains, and even into organic monomers such as acids, ketones, aldehydes, and esters. These decomposition products are then used as raw materials to synthesize hydrophilic carbon quantum dots with a diameter of less than 5 nm through a bottom-up method (hydrothermal or microwave).

[0037] The preparation method provided by this invention offers advantages such as a broad source of raw materials (including medical waste materials), a simple and controllable process, good reproducibility, and low cost. Furthermore, the process produces fewer byproducts that are harmful to humans or pollute the environment. This method not only facilitates the recycling of disposable medical waste materials, reducing the spread of viruses and bacteria and environmental pollution, but also converts waste into high-value hydrophilic carbon quantum dots, which have potential market value in fields such as bioimaging and photocatalysis.

[0038] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a Transmission Electron Microscopy (TEM) image of the carbon quantum dot powder provided in Example 1 of the present invention.

[0040] Figure 2 This is a high-resolution transmission electron microscopy (HRTEM) image of the carbon quantum dot powder provided in Example 1 of the present invention.

[0041] Figure 3 This is a statistical diagram of the particle size distribution of the carbon quantum dot powder provided in Example 1 of the present invention.

[0042] Figure 4 This is the X-ray diffraction (XRD) pattern of the carbon quantum dot powder provided in Example 1 of the present invention.

[0043] Figure 5 This is the full spectrum of the X-ray photoelectron spectroscopy (XPS) of the carbon quantum dot powder provided in Example 1 of the present invention.

[0044] Figure 6 This is a C1s high-resolution XPS image of the carbon quantum dot powder provided in Example 1 of the present invention.

[0045] Figure 7 This is an O1s high-resolution XPS image of the carbon quantum dot powder provided in Example 1 of the present invention.

[0046] Figure 8 This is a Fourier Transform Infrared Spectroscopy (FTIR) graph of the carbon quantum dot powder provided in Example 1 of the present invention.

[0047] Figure 9 This is a diagram showing the hydrophilic effect of the carbon quantum dots before and after freeze-drying provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0048] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0049] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used are all commercially available unless otherwise specified.

[0050] Example 1

[0051] The hydrophilic carbon quantum dots were prepared using disposable medical masks containing PP. The process is as follows:

[0052] After cleaning the disposable medical mask (containing PP) with deionized water, place it in a blast oven to dry, then use scissors to remove the adhesive parts on the outer edge of the medical mask, the nose pads and the ear straps, leaving the remaining main body layered for later use; transfer the remaining main body to a sealed glass container and lay it flat, and introduce wet oxygen (the water content of oxygen is 1.5g / m 3 ) and placed it under an ultraviolet (wavelength of 310nm) lamp for 40 hours, and then waited for the glass container to cool to room temperature, and deionized water (30ml) was added to the glass container to clean the container wall and collect the reaction sample after light treatment to obtain the pretreated sample aqueous solution.

[0053] The sample aqueous solution obtained above was transferred to a 100 ml high-pressure reactor and hydrothermally treated in a high-temperature blast oven at 180°C. After the hydrothermal reaction for 7 hours, a hydrothermal product was obtained. The hydrothermal product was filtered with a 0.22 µm water filter membrane to remove large particle size impurities in the solution, thereby obtaining a pre-solution containing carbon quantum dots with uniform particle size.

[0054] The carbon quantum dot pre-solution was transferred to a biological dialysis bag with a molecular weight cutoff of 1000Da and dialyzed with deionized water to obtain a purified carbon quantum dot solution. The carbon quantum dot solution was divided into culture dishes and pre-frozen. A freeze dryer was then used to remove the frozen sample water. The freeze drying temperature was set to -85°C. After drying for 12 hours, carbon quantum dot powder was obtained. The characterization results are as follows:

[0055] 1. Its TEM image, such as Figure 1 As shown in the figure, it can be seen that the carbon quantum dots are spherical and well dispersed.

[0056] Second, its HRTEM image, such as Figure 2 As shown in the figure, it can be seen that the lattice structure of a single carbon quantum dot is complete, the lattice fringes are clearly visible, and the interlayer spacing is 0.21 nm, which is a typical graphite phase (100) plane.

[0057] 3. After measuring the diameters of more than 90 carbon quantum dots using Nano measurer software, the diameter distribution diagram of the carbon quantum dots was obtained, as shown in the figure below. Figure 3 As shown in the figure, the particle size of the carbon quantum dots is relatively uniform, ranging from 1.2 to 4.8 nm, with an average diameter of 3.09 nm. This result shows that the carbon quantum dots have a high degree of graphitization and a uniform particle size distribution.

[0058] 4. Its XRD pattern, such as Figure 4 As shown in the figure, it can be seen that the carbon quantum dots have two strong diffraction peaks centered at 2θ=28.9° and 42.9°, respectively. According to the Bragg equation, their corresponding interlayer spacing is 、 , corresponding to the (002) of the graphite structure

[133] Crystal plane and (100)

[132] This is consistent with the conclusion drawn from TEM image analysis that carbon quantum dots have a highly graphitic crystal structure. In addition, compared with the (002) crystal plane at 2θ=26.4° and the (100) crystal plane at 2θ=42.2° of the graphite phase, the characteristic peaks of carbon quantum dots have shifted to the right, which may be caused by the abundant surface defect sites or functional groups such as -COOH and -OH.

[0059] 5. Its full spectrum of XPS, such as Figure 5 As shown in the figure, it can be seen that the surface of carbon quantum dots is composed of only two elements, C and O.

[0060] 6. Its C1s and O1s high-resolution XPS images, such as Figure 6 and Figure 7 As shown. Figure 6 Three fitting peaks can be seen, corresponding to CC / C=C (284.8 eV), COC / C-OH (286.0 eV) and carboxyl group (-COOH, 288.5 eV); Figure 7 Two fitting peaks can be seen, corresponding to C=O (531.6 eV) and CO (532.5 eV). This result indicates that the surface of carbon quantum dots is rich in oxygen-containing functional groups, such as carboxyl and hydroxyl groups. Carboxyl and hydroxyl groups have strong hydrophilicity, so the prepared carbon quantum dots have excellent dispersibility in water.

[0061] 7. Fourier Transform Infrared Spectroscopy (FTIR), such as Figure 8 As shown in the figure, it can be seen that the surface of carbon quantum dots is mainly composed of oxygen-containing functional groups, including C=O (1653cm -1 ) and COC (1185cm -1 ) stretching vibration peak. Located at 4000~1810cm -1 The broad peak at 1561cm corresponds to the stretching vibration of the -OH group. The high intensity of the peak and the tendency of the peak to shift to lower wavenumbers indicate that hydrogen bonding occurs within the -OH group. This result shows that the oxygen element is successfully introduced into the carbon quantum dots in the form of various oxygen-containing functional groups through UV irradiation pretreatment, which gives the carbon quantum dots extremely strong hydrophilicity. In addition, the peak at 1561cm -1 The peak at 1403 cm corresponds to the stretching vibration of C=C. -1 and 1357cm -1 The doublet at 910-500 cm corresponds to the bending vibration of CH in methyl / methylene, while -1 The IR spectrum data showed that the disposable medical mask containing PP was pretreated with ultraviolet light to introduce oxygen elements. These oxygen elements exist in the form of oxygen-containing functional groups in monomers or oligomers and become the opportunity for condensation into carbon quantum dots. The carbon quantum dots finally formed have SP in the internal carbon core. 2 / SP 3 The hybrid structure carries abundant oxygen-containing functional groups on the surface, such as hydroxyl, carboxyl, carbonyl, ether, etc., which is consistent with the test results in XPS.

[0062] The hydrophilicity test results of carbon quantum dots before and after freezing, such as Figure 9 As shown in the figure, it can be seen that the carbon quantum dots before freeze-drying are in the form of yellow powder, and the carbon quantum dots after freeze-drying immediately absorb water and adhere to the surface of the culture dish in a transparent state. This result shows that the carbon quantum dots provided by the present invention have strong hydrophilic properties.

[0063] Example 2

[0064] The hydrophilic carbon quantum dots were prepared using disposable surgical gowns made of spunbond nonwoven fabrics (including PP). The process is as follows:

[0065] After cleaning the disposable surgical gown with deionized water, place it in an oven and dry it at 65℃, then cut it into small pieces for later use; transfer the pieces to a sealed glass container and lay them flat, then introduce wet oxygen (the water content of oxygen is 1g / m 3 ), and placed it under ultraviolet light (wavelength of 370nm) for 24 hours. After the glass container cooled to room temperature, deionized water (30ml) was added to clean the container wall to obtain the pretreated sample aqueous solution.

[0066] The sample aqueous solution obtained above was transferred to a microwave oven and heated using a microwave with a power of 1000 W for 8 minutes to obtain a pre-product solution; the pre-product solution was filtered using a 0.22 µm water filter membrane to obtain a carbon quantum dot pre-solution with uniform particle size.

[0067] The carbon quantum dot pre-solution was transferred to a biological dialysis bag with a molecular weight cutoff of 1000Da, and dialyzed with deionized water to obtain a purified carbon quantum dot solution. The carbon quantum dot solution was placed in a culture dish for pre-freezing, and then a freeze dryer was used to remove the frozen sample moisture. The freeze-drying temperature was set to -85°C and dried for 12 hours to obtain carbon quantum dot powder, which was characterized. The characterization results were consistent with the characterization results of the carbon quantum dot powder provided in Example 1.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene, characterized in that: The hydrophilic carbon quantum dots are spherical and have a diameter of less than 5 nm; The X-ray diffraction pattern of the hydrophilic carbon quantum dots has characteristic diffraction peaks at positions of 2θ of 28.7 to 29.1 degrees and 42.7 to 43.1 degrees; The steps include: S100, washing medical waste materials containing polypropylene with water, drying, shearing, placing the materials into a sealed glass reaction vessel, introducing wet oxygen, and irradiating the reaction system with ultraviolet light to decompose the long chains of polypropylene in the medical waste materials, thereby obtaining a raw material; Wet oxygen is oxygen containing water, with a water content of >1g / m 3 ; In the process of irradiating the reaction system with ultraviolet light, the wavelength of the ultraviolet light is 310nm to 370nm, and the irradiation time is 20 to 40h; The raw materials are organic monomers and / or oligomers containing oxygen functional groups and / or olefins; S200, adding water to the raw materials, and synthesizing hydrophilic carbon quantum dots by hydrothermal synthesis or microwave synthesis; The reaction temperature of the hydrothermal synthesis method is 160°C to 200°C, and the reaction time is 8 to 12 hours. In the microwave synthesis method, microwave heating is performed at a power of 800-1200 W and the addition time is 6-10 min; S300, filtering the aqueous solution of hydrophilic quantum dots obtained in step S200 through a 0.2-0.45 µm water filter membrane to obtain a filtrate; S400, transferring the filtrate to a semipermeable membrane container with a molecular weight cut-off of 1000 to 3500 Da, and dialyzing the filtrate with deionized water to obtain a dialysate containing purified hydrophilic carbon quantum dots; S500, freeze-drying the dialysate to obtain the hydrophilic carbon quantum dot powder; The freeze-drying temperature is -84 to -94°C, and the time is 12 to 36 hours.

2. The method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene according to claim 1, wherein: The oxygen-containing functional group in step S100 includes one or more of a ketone group, an aldehyde group, a carboxyl group, a hydroxyl group and an ether bond.

3. The method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene according to claim 1, wherein: The diameter of the hydrophilic carbon quantum dots is 1.2 to 4.8 nm.

4. The method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene according to claim 1, wherein: The diameter of the hydrophilic carbon quantum dots is 3.0-3.2 nm.

5. The method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene according to claim 1, wherein: When the 2θ value of the hydrophilic carbon quantum dots is 28.9 degrees, the interlayer spacing is 0.309 nm; when the 2θ value is 42.9 degrees, the interlayer spacing is 0.211 nm.

6. The method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene according to claim 1, wherein: Used in the recycling of medical waste materials containing polypropylene.

7. The method for preparing hydrophilic carbon quantum dots based on medical waste materials containing polypropylene according to claim 6, wherein: The medical waste materials containing polypropylene include one or more of disposable medical masks, medical infusion bags, disposable medical protective clothing and disposable medical examination pads.

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