Preparation method and application of novel biomass carbon dots

Abstract

The invention discloses a preparation method and application of novel biomass carbon dots. The preparation method comprises the following steps: S1, adding apple branch powder into water, and uniformly mixing to obtain a mixed solution; and S2, putting the mixed solution obtained in S1 into a microwave oven for microwave treatment to obtain a reactant. S3, taking out reactants, cooling the reactants to room temperature, and adding water for centrifugal filtration treatment. And S4, collecting a supernatant obtained by treatment in S3, and purifying the supernatant. And S5, drying the purified product obtained in S4 to obtain the biomass carbon dots, and storing the prepared biomass carbon dots in an environment with a constant temperature of 4 DEG C for later use. Apple branches are used as precursors, the biomass carbon dots are synthesized through a microwave method, biocompatibility is good, toxicity is low, high-selectivity and high-sensitivity detection of Cr < 6 + > and riboflavin can be achieved, the synthesis process is economical, environmentally friendly, rapid, simple and convenient, and a new scheme is provided for the environment-friendly detection technology.

Description

Technical Field

[0001] This invention relates to the field of biomass carbon dot technology, specifically to a novel method for preparing biomass carbon dots, and also to the application of biomass carbon dots prepared by the method. Background Technology

[0002] Chromium, as a transition metal element, is widely present in industrial production and the natural environment. 6+ Due to its strong oxidizing properties and high toxicity, Cr poses a serious threat to the ecological environment and human health. 6+ Chromium can enter organisms through water, soil, and air. Long-term exposure can cause serious consequences such as DNA damage and cancer, and it is an internationally recognized Group 1 carcinogen. However, in appropriate amounts, chromium is an essential trace element for the human body, participating in the metabolism of carbohydrates and lipids. Therefore, industrial wastewater and the environment contain high levels of chromium. 6+ Monitoring is of great significance.

[0003] Riboflavin (vitamin B2) is a water-soluble vitamin that plays a crucial role in biological metabolism. As a precursor to flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), riboflavin participates in redox reactions and has irreplaceable functions in energy metabolism and the electron transport chain. Furthermore, riboflavin acts as a coenzyme in the catalytic processes of various enzymes, and is essential for maintaining cellular respiration, fatty acid metabolism, and the antioxidant defense system. Insufficient riboflavin intake can lead to deficiency disorders such as angular cheilitis, glossitis, and seborrheic dermatitis, and may even affect visual health. Therefore, the detection of riboflavin content in food and medicine is of great significance.

[0004] In recent years, fluorescent carbon dots have been widely used as fluorescent probes in fields such as environmental monitoring and food testing. Traditional preparation of fluorescent carbon dots usually involves highly toxic chemical reagents, which are expensive and can also cause environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a novel method for preparing biomass carbon dots and its application, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a novel method for preparing biomass carbon dots, comprising the following steps: S1. Add apple twig powder to water and mix well to obtain a mixture; S2 involves placing the mixture obtained in S1 into a microwave oven for microwave treatment to obtain the reactants; S3 Take out the reactants, let them cool to room temperature, add water and centrifuge and filter them; S4 collects the supernatant obtained after treatment in S3 and purifies the supernatant; S5 drying the purified product obtained in S4 to obtain biomass carbon dots, and the prepared biomass carbon dots are stored in a constant-temperature 4℃ environment for standby use.

[0007] As a further improvement of the above scheme, in S1, the solid-liquid ratio of the apple branch powder and water is 0.25~1.25g:10mL; after the apple branch powder is added into water, mixing is performed under the action of magnetic stirring for 5~15min.

[0008] As a further improvement of the above scheme, the solid-liquid ratio of the apple branch powder and water is 0.05gmL -1 .

[0009] As a further improvement of the above scheme, in S2, the microwave power of the microwave treatment is 180~900W, and the microwave time is 4~12min, to obtain a dark brown solid reaction product.

[0010] As a further improvement of the above scheme, the microwave power of the microwave treatment is 900W, and the microwave time is 10min.

[0011] As a further improvement of the above scheme, in S3, the reaction product is added into water, and uniform mixing is performed to obtain a brown liquid, the brown liquid is transferred into a centrifuge, centrifugation is performed at a centrifugal speed of 2000~4000rpm for 5~20min, and then filtration is performed using a 0.22m filter membrane, and the supernatant is reserved.

[0012] As a further improvement of the above scheme, in S4, the supernatant is dialyzed using a dialysis bag with a molecular weight cut-off of 1000Da, and the dialysis time is 60~80h.

[0013] As a further improvement of the above scheme, in S5, the purified product is freeze-dried under vacuum, and the obtained biomass carbon dots are brown-yellow powders.

[0014] As a further improvement of the above scheme, the fluorescence of the biomass carbon dots can be quenched by Cr 6+ and riboflavin.

[0015] As a further improvement of the above scheme, in the range of a Cr 6+ concentration of 5~50M, the fluorescence response of the biomass carbon dots has a good linear correlation with the Cr 6+ concentration.

[0016] As a further improvement of the above scheme, in the range of a riboflavin concentration of 5~40M, the fluorescence response of the biomass carbon dots has a good linear correlation with the riboflavin concentration.

[0017] A biomass carbon dot prepared by the preparation method has a good linear correlation with the Cr 6+Applications in detection.

[0018] Application of biomass carbon dots prepared by the method described above in riboflavin detection.

[0019] Compared with existing technologies, the beneficial effects of this invention are: the preparation process of biomass carbon dots is green, economical, simple, and rapid; the synthesized biomass carbon dots have advantages such as low toxicity and low cost; and the fluorescence of the synthesized biomass carbon dots can be detected by Cr. 6+ And riboflavin quenching can achieve Cr in the aquatic environment 6+ And the highly selective and sensitive detection of riboflavin. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the biomass carbon dots characterization obtained in Example 1 of the present invention, wherein A is a TEM image, B is a particle size distribution statistics, C is an XRD spectrum, D is an FTIR spectrum, E is a full-scan XPS energy spectrum, F is a C1s high-resolution XPS spectrum, G is an N1s high-resolution XPS spectrum, H is an O1s high-resolution XPS spectrum, and I is an S2p high-resolution XPS spectrum.

[0021] Figure 2 This is a schematic diagram illustrating the optical properties and metal ion selectivity of the biomass carbon dots prepared in Example 1 of the present invention. In the diagram, A represents the UV-Vis absorption spectrum, fluorescence excitation spectrum, and emission spectrum; B represents the fluorescence emission spectrum at different excitation wavelengths; C represents the stability of the fluorescent carbon dots under UV lamp irradiation; D represents the selectivity of the carbon dots for metal ions; and E represents the selectivity of different Cr... 6+ Fluorescence spectrum at concentration F, where F is Cr 6+ The linear relationship between concentration and fluorescence intensity of biomass carbon dots, where F0 and F represent the concentration of biomass carbon dots in Cr... 6+ Fluorescence intensity in the presence and absence of fluorescence.

[0022] Figure 3 This is a schematic diagram of the amino acid selectivity of biomass carbon dots prepared in Example 1 of the present invention. In this diagram, A represents the selectivity of carbon dots for amino acids, B represents the fluorescence spectrum at different riboflavin concentrations, C represents the linear relationship between riboflavin concentration and fluorescence intensity of biomass carbon dots, and F0 and F represent the fluorescence intensity of biomass carbon dots in the presence and absence of riboflavin, respectively.

[0023] Figure 4This diagram illustrates the optimization of biomass carbon dot preparation conditions according to the present invention. In the diagram, A represents the fluorescence spectrum of biomass carbon dots prepared with different amounts of apple twigs added; B represents the fluorescence intensity of biomass carbon dots prepared with different amounts of apple twigs added; C represents the fluorescence spectrum of biomass carbon dots prepared with different microwave powers; D represents the fluorescence intensity of biomass carbon dots prepared with different microwave powers; E represents the fluorescence spectrum of biomass carbon dots prepared with different microwave times; and F represents the fluorescence intensity of biomass carbon dots prepared with different microwave times. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and not intended to limit the invention.

[0025] The specific embodiments of the present invention will be described in detail below.

[0026] Example 1 This embodiment provides a novel method for preparing biomass carbon dots, the specific operation of which is as follows: 0.50g of apple branch powder is weighed and added to 10mL of ultrapure water. The mixture is stirred magnetically for 10min. The resulting mixture is placed in a household microwave oven and microwaved at 900W for 10min to obtain a dark brown solid. After cooling to room temperature, 10mL of ultrapure water is added and mixed to obtain a brown liquid. The brown solution is centrifuged at 3000rpm for 10min and then filtered through a 0.22m filter membrane. The supernatant is further purified in a dialysis bag with a molecular weight cutoff of 1000Da for 72h to obtain N,S-BCDs. Then, the supernatant is freeze-dried under vacuum to obtain brownish-yellow biomass carbon dot powder. The obtained powder is stored in a refrigerator at a constant temperature of 4℃ for later use.

[0027] In this embodiment, apple tree branches, a natural biomass resource, are used. These components are rich in cellulose, polysaccharides, and heteroatoms. These components achieve self-doping during the synthesis of biomass carbon dots, which is beneficial to improving the biocompatibility of biomass carbon dots. The resulting fluorescent carbon dot probe can achieve efficient detection and meet the requirements of sustainable development, providing a new idea for the development of environmentally friendly detection technologies.

[0028] The following methods were employed: High-resolution transmission electron microscopy (TEM, Talos F200X) was used to observe the shape, particle size distribution, and lattice spacing of N,S-BCDs; X-ray diffraction (XRD, D / MAX2500TC) was used to characterize the crystal form of N,S-BCDs; Fourier transform infrared spectroscopy (FTIR, FIR8900) was used to analyze the functional group structure present in N,S-BCDs; X-ray photoelectron spectroscopy (XPS, Escalab250Xi) was used to analyze the elemental composition and specific bonding of N,S-BCDs; and a double-beam ultraviolet-visible spectrophotometer (UV-Vis, TU-1950) and a fluorescence spectrophotometer (F-7000) were used to determine the optical properties of N,S-BCDs. The aforementioned characterization results are as follows: Figure 1 As shown, Figure 1 In the image, A is the TEM image, B is the particle size distribution statistics, C is the XRD spectrum, D is the FTIR spectrum, E is the full-scan XPS energy spectrum, F is the C1s high-resolution XPS spectrum, G is the N1s high-resolution XPS spectrum, H is the O1s high-resolution XPS spectrum, and I is the S2p high-resolution XPS spectrum.

[0029] TEM was used to characterize the morphology, size, and microstructure of N,S-BCDs. Figure 1 As shown in Figure A, the TEM image reveals that N,S-BCDs are uniformly dispersed in ultrapure water in a spherical shape, with a lattice fringe spacing of 0.19 nm. Figure 1 As shown in Figure B, the particle size distribution of N,S-BCDs ranges from 2.1 to 3.0 nm, with an average particle size of approximately 2.1 nm. (XRD pattern) Figure 1 C) shows that N,S-BCDs have two broad diffraction peaks at 2θ=20.4° and 2θ=43.4°, which are close to the graphite crystal structure, indicating that N,S-BCDs are mainly amorphous carbon structures. This suggests that N,S-BCDs have similar structures to other biomass-based CDs.

[0030] The surface functional groups contained in N,S-BCDs play a crucial role in their fluorescence properties and interactions with other substances. The FTIR characterization results of N,S-BCDs are as follows: Figure 1 As shown in D, at 3431cm -1 The absorption peak at 2938 cm⁻¹ is the stretching vibration peak of OH / NH. -1 and 1414cm -1 The absorption peaks at 1720 cm⁻¹ represent the stretching and bending vibration peaks of CH, respectively. -1 and 1605cm -1 The absorption peak at 1236 cm⁻¹ corresponds to the stretching vibration peak of C=O / C=N. -1 1053cm -1773cm -1 The corresponding peaks at these locations are the stretching vibration peaks of CN, the stretching vibration peak of CO, and the bending vibration peak of CS, respectively. FTIR analysis results indicate that the surface of N,S-BCDs contains abundant amino, carboxyl, hydroxyl, and sulfur-containing functional groups.

[0031] XPS characterization further determined the elemental composition and chemical bond structure of N,S-BCDs, as shown in the XPS total spectrum ( Figure 1 E) contains four characteristic peaks at 285 eV, 399 eV, 531 eV, and 169 eV, representing C1s, N1s, O1s, and S2p peaks, respectively. The elemental contents of C, N, O, and S in N,S-BCDs were detected to be 54.01%, 6.47%, 33.87%, and 5.42%, respectively. Figure 1 F, in the XPS spectrum of C1s, shows four peaks: CC (284.5 eV), CO / CN (286.08 eV), C=N (287.18 eV), and C=O (288.88 eV). For example... Figure 1 G, in the XPS spectrum of N1s, shows only two peaks: CN (399.98 eV) and NH (401.78 eV); as Figure 1 H, in the XPS spectrum of O1s, shows two peaks: SO (532.48 eV) and CO / OH (531.68 eV). For example... Figure 1 I, in the XPS spectrum of S2p, can be separated into two peaks, namely C-SO3 (168.68eV) and C-SO4 (169.88eV).

[0032] In summary, the XPS analysis results are consistent with those of FTIR, further confirming that the surface of N,S-BCDs contains a large number of amino, carboxyl, hydroxyl, and sulfur-containing functional groups, which gives N,S-BCDs high water solubility and helps to improve the fluorescence performance of N,S-BCDs.

[0033] The following tests used UV-Vis and FL to measure the UV absorption wavelength, fluorescence center, and fluorescence stability of N,S-BCDs. Figure 2 As shown in Figure A, the UV-Vis absorption spectrum of N,S-BCDs shows an absorption peak at 275 nm, which may indicate an n-π* transition in the C=O / C=N double bond. Under 365 nm UV irradiation, they emit bright blue fluorescence, with excitation and emission wavelengths of 309 nm and 374 nm, respectively. Figure 2As shown in Figure B, under excitation wavelengths of 280–400 nm, the fluorescence emission wavelength of N,S-BCDs exhibits a redshift with increasing excitation wavelength. This may be due to surface defects in N,S-BCDs. The fluorescence emission intensity initially increases and then decreases with increasing excitation wavelength, reaching its maximum at an excitation wavelength of 310 nm. Fluorescence stability is an important criterion for evaluating the fluorescence performance of N,S-BCDs. Figure 2 As shown in Figure C, the UV irradiation time did not affect the fluorescence intensity of N,S-BCDs, indicating that N,S-BCDs exhibit fluorescence stability under UV irradiation. In summary, this demonstrates that N,S-BCDs possess excellent fluorescence properties.

[0034] The following section applies N,S-BCDs to the detection of various common metal ions, exploring the effect of different metal ions on the fluorescence intensity of N,S-BCDs. Preparations containing 300µM metal ions (K... + Na + Ca 2+ Zn 2+ Cr 6+ Pb 2+ Sn 2+ Ba 2+ Mn 2+ Sr 2+ Mg 2+ Bi 3+ The N,S-BCDs solution was shaken thoroughly and allowed to stand for 20 minutes before fluorescence intensity detection. Different concentrations of Cr were then used. 6+ (0-800 μM) was added to N,S-BCDs solution, shaken thoroughly, and allowed to stand for 20 min before fluorescence intensity detection. Different concentrations of Cr were analyzed. 6+ The changing trend of fluorescence quenching intensity of N,S-BCDs was investigated to explore the Cr 6+ Linear relationship between concentration and fluorescence response (F / F0) of N,S-BCDs.

[0035] like Figure 2 As shown in Figure D, the results indicate that N,S-BCDs affect Cr 6+ It exhibits good selectivity and responsiveness, and other metal ions have little impact on the fluorescence intensity of N,S-BCDs. Furthermore, the presence of other metal ions has a relatively small effect on Cr... 6+ The selective response has almost no effect. Figure 2 E indicates that, with Cr 6+ As the concentration increased from 0 μM to 800 μM, the fluorescence intensity of N,S-BCDs gradually decreased, while the center position of the emission peak remained unchanged. Further investigation was conducted into the fluorescence response (F / F0) and Cr... 6+ The relationship between concentrations, the results are as followsFigure 2 As shown in F, in Cr 6+ In the concentration range of 5~50µM, the fluorescence response was similar to that of Cr. 6+ The concentrations showed a good linear correlation. The linear fitting equation was: y =-0.00383 x +0.97421, correlation coefficient R 2 The value is 0.99082. Based on the detection limit calculation formula LOD = 3σ / k, the detection limit is 1.64 μM, which proves that N,S-BCDs are detectable in Cr... 6+ It exhibits high sensitivity in detection, with detection limits comparable to, or even better than, those of other fluorescent probes for Cr. Its low detection limit and wide linear range make N,S-BCDs the optimal choice for environmental monitoring and water quality assessment. The aforementioned results demonstrate that N,S-BCDs effectively detect Cr. 6+ With high selectivity and high sensitivity, N,S-BCDs can be used as a detection method for Cr. 6+ Excellent sensor.

[0036] N,S-BCDs were applied to amino acid detection to investigate the effect of different amino acids on the fluorescence intensity of N,S-BCDs. N,S-BCDs solutions containing 200 μM metal ions (L-glutamic acid, D-asparagine, L-asparagine, L-glutamine, mandelic acid, L-methionine, L-leucine, L-valine, L-ascorbic acid, and riboflavin) were prepared, shaken thoroughly, and allowed to stand for 20 min before fluorescence intensity detection. Different concentrations of riboflavin (0-200 μM) were added to the N,S-BCDs solutions, shaken thoroughly, and allowed to stand for 20 min before fluorescence intensity detection. The changing trend of N,S-BCDs fluorescence quenching intensity under different concentrations of riboflavin was analyzed to explore the linear relationship between riboflavin concentration and the fluorescence response (F / F0) of N,S-BCDs. The results are as follows: Figure 3 As shown.

[0037] like Figure 3 As shown in Figure A, the results indicate that N,S-BCDs exhibit good selectivity and responsiveness to riboflavin, while other amino acids have little effect on the fluorescence intensity of N,S-BCDs. Furthermore, the presence of other amino acids has almost no effect on the selective response to riboflavin. Figure 3 As shown in Figure B, the fluorescence intensity of N,S-BCDs gradually decreased as the riboflavin concentration increased from 0 μM to 200 μM, while the center position of the emission peak remained unchanged. Further investigation into the relationship between fluorescence response (F / F0) and riboflavin concentration yielded the following results: Figure 3 As shown in Figure C, within the riboflavin concentration range of 5–40 μM, the fluorescence response exhibits a good linear correlation with the riboflavin concentration. The linear fitting equation is as follows: y =-0.01033x +0.9212, correlation coefficient R 2 The value is 0.99363. Based on the detection limit calculation formula LOD=3σ / k, the detection limit is found to be 0.78 μM. The aforementioned results demonstrate that N,S-BCDs have high sensitivity in the detection of riboflavin and can be used for highly sensitive detection of riboflavin in aquatic environments.

[0038] Example 2 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Example 1 is that the amount of apple branch powder used in this embodiment is 0.25g, and the rest is the same as in Example 1.

[0039] Example 3 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Example 1 is that the amount of apple branch powder used in this embodiment is 0.75g, and the rest is the same as in Example 1.

[0040] Example 4 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Example 1 is that the amount of apple branch powder used in this embodiment is 1.00g, and the rest is the same as in Example 1.

[0041] Example 5 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the amount of apple branch powder used in this embodiment is 1.25g, and the rest is the same as in Embodiment 1.

[0042] Example 6 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the microwave power in this embodiment is 180W, and the rest is the same as in Embodiment 1.

[0043] Example 7 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the microwave power in this embodiment is 360W, and the rest is the same as in Embodiment 1.

[0044] Example 8 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the microwave power in this embodiment is 540W, and the rest is the same as in Embodiment 1.

[0045] Example 9 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the microwave power in this embodiment is 720W, and the rest is the same as in Embodiment 1.

[0046] Example 10 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the microwave time is 4 minutes, and the rest is the same as in Embodiment 1.

[0047] Example 11 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this method and Embodiment 1 is that the microwave time in this embodiment is 6 minutes, and the rest is the same as in Embodiment 1.

[0048] Example 12 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the microwave time is 8 minutes, and the rest is the same as in Embodiment 1.

[0049] Example 13 This embodiment provides a novel method for preparing biomass carbon dots. The only difference between this embodiment and Embodiment 1 is that the microwave time is 12 minutes, and the rest is the same as in Embodiment 1.

[0050] Example 14 This embodiment provides a method for preparing biomass carbon dots in Cr as described in Example 1. 6+ And its application in riboflavin detection. River water was selected as the environmental water sample, and a standard addition method was used to conduct a spiked recovery test on the actual water sample to reveal the Cr content. 6+ The application performance of riboflavin detection in actual water samples is described, but the specific experimental process will not be repeated here. The experimental results are as follows: When different concentrations of Cr were added... 6+ In environmental water samples, Cr based on N,S-BCDs fluorescent probes 6+ The spiked recoveries reached an excellent level of 96.05%–102.56%, with relative standard deviations (RSDs) all less than 1.54%. When different concentrations of riboflavin were added to environmental water samples, the riboflavin spiked recoveries of the N,S-BCDs-based fluorescent probes reached an excellent level of 97.70%–102.30%, with RSDs all less than 1.24%. The aforementioned experimental results fully demonstrate that the N,S-BCDs fluorescent probes prepared using the method of this invention can effectively spike riboflavin in environmental water samples containing Cr. 6+ It has high reliability and practical value in riboflavin detection.

[0051] The following experiments were conducted using biomass carbon dots prepared in Examples 1, 2, 3, 4, and 5 to investigate the effects of different amounts of apple twigs added on the yield and fluorescence intensity of N,S-BCDs; experiments were conducted using biomass carbon dots prepared in Examples 1, 6, 7, 8, and 9 to investigate the effects of different microwave powers on the yield and fluorescence intensity of N,S-BCDs; and experiments were conducted using biomass carbon dots prepared in Examples 1, 10, 11, 12, and 13 to investigate the effects of different microwave times on the yield and fluorescence intensity of N,S-BCDs. The aforementioned experimental procedures will not be repeated here, and the experimental results are as follows. Figure 4 As shown.

[0052] Figure 4 In the figure, A represents the fluorescence spectra of biomass carbon dots prepared with different amounts of apple branch addition, and B represents the fluorescence intensity of biomass carbon dots prepared with different amounts of apple branch addition. Combining A and B, it can be seen that as the amount of apple branch addition increases from 0.25g to 0.50g, the fluorescence intensity of N,S-BCDs continuously increases. This is because the apple branch raw material is fully carbonized under suitable conditions. However, when the amount of apple branch raw material continues to increase, the fluorescence intensity of N,S-BCDs begins to show a decreasing trend. This may be because the raw material cannot be completely carbonized, or even only a small portion of the raw material undergoes the carbonization reaction. The aforementioned results indicate that the optimal raw material addition amount is 0.5g.

[0053] Figure 4 In the figure, C represents the fluorescence spectrum of biomass carbon dots prepared under different microwave powers, and D represents the fluorescence intensity of biomass carbon dots prepared under different microwave powers. Combining C and D, it can be seen that the fluorescence intensity of biomass carbon dots increases significantly with increasing microwave power. When the microwave power is 900W, the fluorescence intensity of N,S-BCDs reaches the highest point, indicating that 900W is the optimal microwave power.

[0054] Figure 4 In the figure, E represents the fluorescence spectrum of biomass carbon dots prepared at different microwave times, and F represents the fluorescence intensity of biomass carbon dots prepared at different microwave times. Combining E and F, it can be seen that when the microwave time increases from 4 min to 10 min, the fluorescence intensity of N,S-BCDs gradually increases, reaching its maximum at 10 min. This is because if the microwave time is too short, the carbonization of the apple branches is incomplete, so the fluorescence intensity of N,S-BCDs increases continuously with increasing carbonization time. However, with further increases in microwave time, the fluorescence intensity begins to decrease, possibly because excessively long microwave times damage the surface structure of the carbon dots, resulting in fluorescence quenching. The aforementioned results indicate that 10 min is the optimal microwave time.

[0055] Through the above single-factor experiments, it can be seen that Example 1 represents the optimal preparation conditions for biomass carbon dots.

[0056] The above embodiments are merely preferred embodiments of the present invention. Any simple modifications, alterations, and substitutions made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A novel method for preparing biomass carbon dots, characterized in that, Includes the following steps: S1. Add apple twig powder to water and mix well to obtain a mixture; S2 involves placing the mixture obtained in S1 into a microwave oven for microwave treatment to obtain the reactants; S3 Take out the reactants, let them cool to room temperature, add water and centrifuge and filter them; S4 collects the supernatant obtained after treatment in S3 and purifies the supernatant; S5 is used to dry the purified product obtained from S4 to obtain biomass carbon dots, which are then stored at a constant temperature of 4°C for later use.

2. The preparation method according to claim 1, characterized in that: In S1, the solid-liquid ratio of the apple branch powder to water is 0.25~1.25g:10mL; after the apple branch powder is added to the water, it is mixed for 5~15min under magnetic stirring.

3. The preparation method according to claim 2, characterized in that: The solid-liquid ratio of the apple branch powder to water is 0.05 g / mL. -1 .

4. The preparation method according to claim 1, characterized in that: In S2, the microwave power of the microwave treatment is 180~900W, and the microwave time is 4~12min, resulting in a dark brown solid reactant.

5. The preparation method according to claim 4, characterized in that: The microwave power of the microwave treatment is 900W, and the microwave time is 10min.

6. The preparation method according to claim 1, characterized in that: In S3, the reactants are added to water and mixed evenly to obtain a brown liquid. The brown liquid is then transferred to a centrifuge and centrifuged at 2000-4000 rpm for 5-20 minutes. After centrifugation, the mixture is filtered through a 0.22 μm filter membrane, and the supernatant is retained.

7. The preparation method according to claim 1, characterized in that: In S4, the supernatant was dialyzed using a dialysis bag with a molecular weight cutoff of 1000 Da for 60-80 hours.

8. The preparation method according to claim 1, characterized in that: In S5, the purified product is freeze-dried under vacuum, and the resulting biomass carbon dots are brownish-yellow powder. The fluorescence of biomass carbon dots can be detected by Cr 6+ and riboflavin quenching; In Cr 6+ Within a concentration range of 5–50 μM, the fluorescence response of the biomass carbon dots was similar to that of Cr. 6+ The concentrations showed a good linear correlation; Within the riboflavin concentration range of 5–40 μM, the fluorescence response of the biomass carbon dots showed a good linear correlation with the riboflavin concentration.

9. A biomass carbon dot prepared by the method according to any one of claims 1 to 8 in Cr 6+ Applications in detection.

10. The application of biomass carbon dots prepared by any one of claims 1 to 8 in riboflavin detection.

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