Preparation of long-life chitosan-based phosphorescent carbon dots and application of long-life chitosan-based phosphorescent carbon dots in anti-counterfeiting / food detection aspects
By modifying and compounding chitosan, long-life chitosan-based phosphorescent carbon dots were prepared, solving the problems of single luminescent color and short lifespan of chitosan-based carbon dots, and enabling their application in anti-counterfeiting and food testing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-04
- Publication Date
- 2026-03-20
AI Technical Summary
Existing chitosan-based carbon dots exhibit a single luminescent color, low quantum yield, and short phosphorescence lifetime, limiting their application in anti-counterfeiting and food inspection.
Functionalized chitosan was prepared by modifying chitosan and then compounded with different matrices to form long-life chitosan-based phosphorescent carbon dots. The surface groups were optimized by microwave reaction and alkaline solvent to extend the phosphorescence lifetime.
The prepared carbon dots have long luminescence time and phosphorescence lifetime, making them suitable for information encryption in the field of anti-counterfeiting. They have also been successfully used for food detection due to their sensitive response characteristics to water molecules and acid-base environments.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of new materials, and in particular relates to a method for preparing long-life chitosan-based phosphorescent carbon dots and their application in anti-counterfeiting / food detection. Background Technology
[0002] With the rapid development of the finished food market and people's increasing health awareness, the use of smart indicators for real-time food freshness detection has received increasing attention. Digital labels (CDs) are gaining popularity in food packaging and inspection due to their potential in anti-counterfeiting and traceability applications. Unlike traditional fluorescent labels that typically use expensive or toxic materials such as rare-earth fluorescent powders or inorganic quantum dots, CDs can be made from food or agricultural waste, exhibiting strong, stable fluorescence under ultraviolet light while remaining invisible under normal lighting. This makes them particularly suitable for labeling high-value or sensitive foods, including imported fruits, functional health foods, and premium seafood, where authenticity and traceability are paramount. CDs can be processed into inks for printing QR codes, hidden markings, or security patterns onto packaging materials.
[0003] In 2013, researchers combined CDs with polyvinyl alcohol (PVA) and achieved phosphorescence emission of CDs for the first time, successfully constructing CDs-based phosphorescent materials. Compared with fluorescent materials, phosphorescent materials have advantages such as long lifetime, no interference from background fluorescence and scattered light, and high sensitivity to the environment, showing great application potential in information encryption, anti-counterfeiting, and bioimaging. Compared with traditional organic RTP materials, CDs-based phosphorescent materials have advantages such as low toxicity, good photostability, and easy structural control, opening up new directions for the research and development of RTP materials.
[0004] Chitosan is a natural polysaccharide polymer derived from chitin, a widely distributed natural substance, through deacetylation. It possesses excellent film-forming properties, biocompatibility, and biodegradability, making it widely used in the biomedical field. As a natural polymer, chitosan is primarily composed of carbon, and its molecular chains are rich in amino groups, making it an excellent source of nitrogen and carbon for biomass. Due to the abundance of amino groups in the chitosan molecular chain, nitrogen self-doping can be achieved in the preparation of carbon dots. The abundant N and O heteroatoms enhance the spin-orbit coupling effect, facilitating the intersystem crossing process of electrons from singlet to triplet states, thus achieving phosphorescence emission. However, limited by its structural characteristics, carbon dots prepared from pure chitosan exhibit a single luminescent color, generally low quantum yield (<10%), and short luminescence time (less than 3 s) and low lifetime (less than 50 ms) in the constructed phosphorescent composite materials, significantly restricting their practical applications. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing long-life chitosan-based phosphorescent carbon dots and their application in anti-counterfeiting / food detection.
[0006] To achieve the above objectives, the technical solution adopted by this invention includes: the preparation of long-life chitosan-based phosphorescent carbon dots and their application in anti-counterfeiting / food detection, characterized in that: chitosan is used as a raw material, and it is first modified to obtain functionalized modified chitosan. The modified chitosan is dissolved in NaOH aqueous solution and reacted in a microwave reactor. The resulting product is filtered and dialyzed to obtain chitosan-based carbon quantum dots with different luminescence colors and characteristics. The chitosan-based carbon quantum dots are then combined with different matrices to obtain phosphorescent carbon quantum dot composite materials with room temperature phosphorescence properties, exhibiting long luminescence time and phosphorescence lifetime.
[0007] Based on the afterglow properties of phosphorescent carbon dots, they can be used in the field of anti-counterfeiting. Based on the sensitive response characteristics of phosphorescent carbon dots to water molecules and acid and alkaline environments, they have been successfully used in the field of food testing.
[0008] The advantages of this invention are:
[0009] (1) Using environmentally friendly chitosan as a nitrogen and carbon source, it is non-toxic, harmless, and low in cost, and can be used in the food industry.
[0010] (2) By modifying chitosan and introducing hydroxyl and amide bonds, the surface groups of carbon dots are optimized, effectively increasing the quantum yield. The addition of alkaline solvents helps to suppress fluorescence quenching, prolong phosphorescence lifetime, and expand its practical application range.
[0011] (3) The carbon dots prepared by this invention can be combined with various matrices such as SiO2, Urea, PVA, boric acid, and sodium carboxymethyl cellulose to form room temperature phosphorescent carbon dots, which have extremely strong versatility.
[0012] (4) The present invention has the advantages of long-life chitosan-based phosphorescent carbon dots, such as environmental friendliness, low cost and biocompatibility, and has good applications in anti-counterfeiting, food testing and other fields. Attached Figure Description
[0013] Figure 1 Infrared spectra of chitosan before and after modification in Case Study 1. (1710 cm⁻¹ is shown in the figure.) -1 The peak at the position corresponds to the C=O bond in the carboxyl group.
[0014] Figure 2 The fluorescence image of the fluorescent carbon dots in Case 1 under 254 nm ultraviolet light irradiation.
[0015] Figure 3 The afterglow photograph of the phosphorescent material used in Case 1.
[0016] Figure 4The lifetime diagram of the phosphorescent material in Case 1 is shown.
[0017] Figure 5 The diagram illustrates the application of anti-counterfeiting encryption for phosphorescent materials in Case 1.
[0018] Figure 6 The diagram illustrates the application of phosphorescent materials in detecting moisture content in food, as shown in Case 1. Detailed Implementation
[0019] The embodiments of the present invention will be described in further detail below:
[0020] A method for preparing long-life chitosan-based phosphorescent carbon dots and their application in anti-counterfeiting / food detection is disclosed. The method is characterized by: using chitosan as a raw material, first modifying it to obtain functionalized chitosan. The modified chitosan is dissolved in an aqueous NaOH solution and reacted in a microwave reactor. The resulting product is filtered and dialyzed to obtain chitosan-based carbon quantum dots with different luminescence colors and properties. These chitosan-based carbon quantum dots are then composited with different matrices to obtain phosphorescent carbon quantum dot composite materials with room-temperature phosphorescence properties, exhibiting long luminescence time and phosphorescence lifetime. Based on the afterglow characteristics of the phosphorescent carbon dots, they can be used in the anti-counterfeiting field. Based on the sensitive response characteristics of the phosphorescent carbon dots to water molecules and acid / alkaline environments, they have been successfully applied in the food detection field.
[0021] The present invention will now be further described with reference to embodiments, but it is not limited to any one of these embodiments or similar examples.
[0022] Example 1
[0023] A certain amount of chitosan was added to a dimethyl sulfoxide (DMSO) solution, followed by succinic anhydride (chitosan to succinic anhydride mass ratio of 1:2). The mixture was stirred until completely dissolved, and then heated and stirred in a 65°C water bath for 6 hours. After cooling to room temperature, the pH of the mixture was adjusted to 5.5, and the precipitate was collected by filtration. The precipitate was deposited in deionized water, and the pH was adjusted to 11 to form a colloidal solution. Recrystallization in acetone yielded modified chitosan. The degree of substitution of succinic anhydride was calculated to be 0.56.
[0024] A certain amount of modified chitosan was weighed and dissolved in NaOH aqueous solution (the mass ratio of modified chitosan to NaOH was 1:0.5). After ultrasonic dissolution, the mixed hot solution was transferred to a microwave hydrothermal parallel synthesizer and reacted at 180 °C for 6 h at a power of 600 W. After the reaction was completed, the concentrated particles were removed by filtration through a 0.22 μm membrane. After dialyzing through a 1000 Da molecular weight dialysis membrane, liquid carbon dots were obtained, which showed a yellow-green color under ultraviolet light irradiation and had a fluorescence quantum yield of 28%.
[0025] The carbon dots prepared above were combined with a PVA film to prepare a CDs@PVA composite material: 6 g of polyvinyl alcohol (PVA) was transferred to a 100 mL beaker, and 54 mL of deionized water was added. The mixture was stirred in a water bath for 6 h at 85 °C until the PVA was completely dissolved. 2 mL of CDs solution and 18 mL of PVA solution were added to the beakers respectively, and gently stirred to ensure complete dispersion of CDs without bubble formation. After thorough mixing, the solution was dropped into a petri dish, evenly covered, and placed in an 80 °C oven for 30 min. After film formation and cooling, the CDs@PVA composite material was obtained. After irradiation with a 254 nm wavelength ultraviolet lamp, a 5 s phosphorescence afterglow phenomenon was observed, with a yellow-green emission color and a phosphorescence lifetime of 103.98 ms.
[0026] Based on the difference in phosphorescence time between modified and unmodified carbon dots, this technology can be used for information anti-counterfeiting and encryption. The carbon dots are bonded to PVA via hydrogen bonds, exhibiting a sensitive response to moisture. As the moisture content increases, the phosphorescence weakens and eventually quenches, making it suitable for detecting trace moisture content in food.
[0027] Example 2
[0028] A certain amount of chitosan was added to a dimethyl sulfoxide (DMSO) solution, followed by succinic anhydride (chitosan to succinic anhydride mass ratio of 1:6). The mixture was stirred until completely dissolved, and then heated and stirred in a 70°C water bath for 8 hours. After cooling to room temperature, the pH of the mixture was adjusted to 6, and the precipitate was collected by filtration. The precipitate was deposited in deionized water, and the pH was adjusted to 12 to form a colloidal solution. Recrystallization in acetone yielded modified chitosan. The degree of substitution of succinic anhydride was calculated to be 0.70.
[0029] A certain amount of modified chitosan was weighed and dissolved in NaOH aqueous solution (the mass ratio of modified chitosan to NaOH was 1:2). After ultrasonic dissolution, the mixed hot solution was transferred to a microwave hydrothermal parallel synthesizer and reacted at 200 °C for 4 h at a power of 700 W. After the reaction was completed, the concentrated particles were removed by filtration through a 0.22 μm membrane. After dialyzing through a 1000 Da molecular weight dialysis membrane, liquid carbon dots were obtained, which showed a yellow-green color under ultraviolet light irradiation and had a fluorescence quantum yield of 36%.
[0030] The carbon dots prepared above were combined with silica to prepare a CDs@SiO2 composite material: 0.015 g of solid CDs, 50 mL of deionized water, 8 mL of tetraethoxysilane, and 2 mL of ammonium hydroxide were added to a 100 mL flask, heated to 70 °C in an oil bath, and then refluxed and stirred for 5 h. The precipitate was then collected by centrifugation and vacuum dried in a 60 °C vacuum drying oven for 10 h to obtain the CDs@SiO2 precursor. After calcination at 700 °C for 90 min in a tube furnace, CDs@SiO2 composite phosphorescent carbon dots were obtained. After irradiation with a 254 nm wavelength ultraviolet lamp, a phosphorescent afterglow phenomenon of 6.5 s was observed, with a blue-green emission color and a phosphorescence lifetime of 132 ms.
[0031] Based on the difference in phosphorescence time between the modified and unmodified carbon dots, it can be used for information anti-counterfeiting encryption. The carbon dots form stable covalent bonds with SiO2, exhibiting sensitive response characteristics to different pH levels, and have been successfully used to detect apple ripeness.
Claims
1. A method for preparing long-life chitosan-based phosphorescent carbon dots and their application in anti-counterfeiting / food detection, characterized in that: Using chitosan as a raw material, it was first modified to obtain functionalized chitosan. The modified chitosan was dissolved in an aqueous NaOH solution and reacted in a microwave reactor. The resulting product was filtered and dialyzed to obtain chitosan-based carbon quantum dots with different luminescence colors and properties. These chitosan-based carbon quantum dots were then composited with different matrices to obtain phosphorescent carbon quantum dot composite materials with room-temperature phosphorescence properties, exhibiting long luminescence time and phosphorescence lifetime.
2. The preparation of a long-life chitosan-based phosphorescent carbon dot according to claim 1 and its application in anti-counterfeiting / food detection, characterized in that: The chitosan was modified with succinic anhydride, and the mass ratio of chitosan to succinic anhydride was 1:1-1:
8. The water bath reaction temperature was 50-100℃, and the reaction time was 2-8 h.
3. The preparation of a long-life chitosan-based phosphorescent carbon dot according to claim 1 and its application in anti-counterfeiting / food detection, characterized in that: During the modification process, the pH was adjusted to 3-7, and after the reaction, the pH was adjusted to 8-12 to form a gel-like solution. The modified chitosan was then recrystallized, with a succinic anhydride substitution degree of 0.25-0.
75.
4. The preparation of a long-life chitosan-based phosphorescent carbon dot according to claim 1 and its application in anti-counterfeiting / food detection, characterized in that: According to claim 1, the preparation of long-life chitosan-based phosphorescent carbon dots and their application in anti-counterfeiting / food detection are characterized in that the mass ratio of modified chitosan to NaOH is 1:1-1:6, the microwave reaction time is 4-7 h, the reaction power is 400-800 W, the reaction temperature is 160-210℃, the quantum yield of carbon quantum dots is 10%-43%, and the luminescence color ranges from blue to yellow-green.
5. The preparation of a long-life chitosan-based phosphorescent carbon dot according to claim 1 and its application in anti-counterfeiting / food detection, characterized in that: According to claim 1, the preparation of long-life chitosan-based phosphorescent carbon dots and their application in anti-counterfeiting / food detection are characterized in that the matrix can be any one of SiO2, urea, PVA, boric acid, and sodium carboxymethyl cellulose.
6. The preparation of a long-life chitosan-based phosphorescent carbon dot according to claim 1 and its application in anti-counterfeiting / food detection, characterized in that: The resulting phosphorescent emission colors ranged from blue to yellow-green, with emission times of 5.5-8 s and lifetimes of 73-158 ms.
7. The preparation of a long-life chitosan-based phosphorescent carbon dot according to claim 1 and its application in anti-counterfeiting / food detection, characterized in that: A long-life chitosan-based phosphorescent carbon dot has been successfully applied in the fields of anti-counterfeiting and food testing.