A method for detecting carbon nanodots

Abstract

This invention discloses a method for detecting nano-carbon dots, which can be used to detect nano-carbon particles or nano-carbon dots. The method includes: preparing a test solution containing nano-carbon dots and a detection substrate, wherein the substrate contains an active gold sol-gel based on SERS; mixing the test solution with the detection substrate to obtain a test sample; irradiating the detection substrate with a preset excitation light and acquiring the Raman spectrum fed back by the detection substrate to obtain a first control spectrum; and irradiating the test sample with the excitation light and acquiring the Raman spectrum fed back by the test sample to obtain an experimental spectrum; determining the components in the nano-carbon dots based on the first control spectrum and the experimental spectrum. This invention provides an effective and convenient means for detecting the components of nano-carbon dots.

Description

Technical Field

[0001] This invention relates to the field of physical detection technology, and in particular to a method for detecting nano-carbon particles. Background Technology

[0002] Carbon nanodots (CNDs) are important members of the carbon family, consisting of a nanoscale carbon core and carbon-based chemical functional groups doped or adsorbed at the edge of the carbon core. They possess a variety of unique physical and chemical properties, such as fluorescence and biocompatibility, and therefore have potential important applications in fields such as light-emitting diodes, displays, solar cells, photodetectors, biology, and medicine.

[0003] Because there are various mixed substances in nano carbon dots, it is quite complicated to detect nitrogen and sulfur doping in CNDs. Generally, X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR) techniques are used for detection. Both of these techniques have a long detection field, high cost, and complex experimental procedures. Summary of the Invention

[0004] The technical problem this invention aims to solve is that the detection methods for nano-carbon dots are costly and involve complex procedures. To address the shortcomings of existing technologies, this invention provides a method for detecting nano-carbon dots.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for detecting nano carbon dots, the method comprising:

[0007] Prepare a test solution and a detection substrate containing nano-carbon dots, wherein the substrate contains an active gold sol-gel based on SERS;

[0008] The test solution is brought into contact with the detection substrate to obtain the test sample;

[0009] The detection substrate is irradiated with a preset excitation light, and the Raman spectrum fed back by the detection substrate is acquired to obtain a first control spectrum; and,

[0010] The sample to be tested is irradiated with the excitation light, and the Raman spectrum fed back by the sample to be tested is collected to obtain the experimental spectrum;

[0011] The composition of the nanocarbon dots was determined based on the first control spectrum and the experimental spectrum.

[0012] The method for detecting nano-carbon dots, wherein the method for preparing the detection substrate includes:

[0013] A salt solution containing gold nanoparticles is mixed with a substrate preparation agent to obtain a curing solution;

[0014] The liquid to be cured is drawn into a pre-set capillary tube and gelled and cured at room temperature to obtain an initial substrate;

[0015] The initial substrate is reduced using a preset reducing agent to obtain an intermediate substrate;

[0016] The intermediate substrate is cleaned to obtain the test substrate.

[0017] The method for detecting nano carbon dots, wherein the nano carbon dots in the test solution contain nitrogen, sulfur and / or boron.

[0018] The method for detecting nano-carbon dots, wherein the excitation light is 785 nm.

[0019] The method for detecting nano-carbon dots, wherein the Raman spectrum is in the infrared band.

[0020] The method for detecting nano-carbon dots, wherein determining the components in the nano-carbon dots based on the first control spectrum and the experimental spectrum includes:

[0021] When a redshift and splitting peak are determined in the experimental spectrum based on the first control spectrum, it is determined that the nano carbon dots contain carbon-sulfur bonds;

[0022] The concentration of carbon sulfides is determined based on the redshift magnitude.

[0023] In the method for detecting nano-carbon dots, the splitting peak is located at a wavelength of 342 cm⁻¹ in the experimental spectrum. -1 With 267 cm -1 Place.

[0024] The method for detecting nano-carbon dots, wherein determining the components in the nano-carbon dots based on the first control spectrum and the experimental spectrum includes:

[0025] When the experimental spectrum is redshifted and exhibits double peaks in the mid-infrared region based on the first control spectrum, it is determined that the nano carbon dots contain nitrogen or a nitrogen-boron mixture.

[0026] In the method for detecting nanocarbon dots, the redshift relative to the position of the reference peak in the first control spectrum is 354 cm⁻¹. -1 .

[0027] The method for detecting nano-carbon dots further includes:

[0028] The test solution is irradiated with the excitation light, and the Raman spectrum fed back by the test solution is collected to obtain a second control spectrum;

[0029] The content of carbon-nitrogen bonds and / or carbon=carbon bonds in the nano carbon dots is determined based on the characteristic peak fingerprint, the second control spectrum, and the experimental spectrum.

[0030] Beneficial Effects: This method provides a SERS-based active gold sol-gel method for detecting carbon nanodots. Simply contact the test solution containing carbon nanodots with the active gold sol-gel and irradiate it with a specific excitation light. Based on the bonding between the gold nanoparticles and carbon nanodots in the sol-gel, the incident excitation light will produce Raman luminescence. By collecting the Raman spectrum and comparing it with the spectrum of the sol-gel without carbon nanodots, the composition of the carbon nanodots can be determined. Compared to commonly used XPS and NMR methods, this method offers faster, more convenient, and lower-cost detection of carbon nanodots. Attached Figure Description

[0031] Figure 1 A flowchart of the detection method for nano-carbon dots provided by the present invention.

[0032] Figure 2 The first control spectrum, the second control spectrum, and the experimental spectrum are provided in the detection method for nano carbon dots provided by the present invention. Detailed Implementation

[0033] This invention provides a method for detecting nano-carbon dots. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0034] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0035] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0036] S10. Prepare the test solution and detection substrate containing nano carbon dots.

[0037] Specifically, Raman spectroscopy is a rapid and sensitive method for detecting elements and functional groups in chemical substances. The inventors of this method used infrared Raman spectroscopy to discover that nitrogen and sulfur-doped carbon nanoparticles on an active gold sol-gel substrate induce a redshift or splitting of characteristic Raman peaks.

[0038] First, a detection substrate suitable for contact with the test solution is prepared. This detection substrate contains a SERS-based active gold sol-gel. The sol-gel is a stable and transparent system. Gold nanoparticles with a particle size between 50 nm and 100 nm are present in the active gold sol-gel, and these nanoparticles emit characteristic Raman light when subsequently excited by excitation light.

[0039] Furthermore, carbon nanodots can be prepared using physical methods such as pulverization and construction, or chemical methods such as gas-phase decomposition, precipitation, and sol-gel methods. In this scheme, to standardize the chemical composition of the carbon nanodots and verify the effectiveness of the detection method, a chemical method is used to prepare the carbon nanodots. In this embodiment, five different groups of carbon nanodots are prepared in advance. In the first, second, and third groups, N (nitrogen)-doped carbon nanodots and NB (nitrogen-boron)-doped carbon nanodots are prepared. In the fourth and fifth groups, NS-doped carbon nanodots (nitrogen-sulfur doping) are prepared.

[0040] The first group prepared N-doped nanoparticles (CNDs-1). First, analytical grade citric acid (CA) was evenly spread at the bottom of a beaker, which was then placed on a heating platform and heated. The beaker was then allowed to cool naturally to room temperature, and ethanol was added. The mixture was then magnetically stirred, ultrasonically vibrated, and centrifuged to precipitate large particles. The supernatant was obtained and dialyzed using a dialysis bag to screen for nanoparticles of suitable diameter. Finally, N-doped nanoparticles dispersed in an ethanol solution were obtained. In this example, 2 g of citric acid was used, the heating temperature was 300 °C, heating was continued for 5–15 min, 30 ml of ethanol was added, magnetic stirring was performed for 10 min, ultrasonic vibration was performed for 10 min, centrifugation was performed at 12000 r / min for 30 min, and the dialysis bag mesh size was 30000 D.

[0041] The second group prepared NB-doped nanoparticles (CNDs-2). First, citric acid and boric acid were mixed and spread evenly at the bottom of a beaker, which was then placed on a heating platform for heating. After the beaker was naturally cooled to room temperature, ethanol was added. The mixture was then magnetically stirred, ultrasonically vibrated, and centrifuged to precipitate large particles. The supernatant was obtained and dialyzed using a dialysis bag to screen for nano-carbon dots of suitable diameter, finally yielding NB-doped nanoparticles dispersed in an ethanol solution. In this example, 2 g of citric acid and 2 g of boric acid (BA) were used. The heating temperature was 300 °C for 5–15 min, the ethanol volume was 30 ml, the magnetic stirring time was 10 min, the ultrasonic vibration time was 10 min, the centrifugation parameters were 12000 r / min for 30 min, and the dialysis bag mesh size was 30000 D.

[0042] The third group prepared N-doped nanoparticles (CNDs-3). First, citric acid and uric acid were mixed. The other steps were the same as those for preparing N-doped nanoparticles and will not be repeated here. In this example, 2 g of citric acid and 2 g of urea were used, and the remaining parameters were the same as those in the second group.

[0043] The fourth group prepared NS-doped nanoparticles (CNDs-4). First, arginine was placed in alcohol and magnetically stirred. After mixing, the mixture was placed in a reaction vessel, and the vessel containing the sample was placed in a drying oven for drying. After drying, the reaction product was magnetically stirred and ultrasonically vibrated to break down and dissolve the product in the solution. Finally, centrifugation was performed to precipitate the product, obtaining nano-carbon dots dispersed in ethanol. In this example, the following parameters were used: 4 g of arginine, 30 ml of alcohol, magnetic stirring time of 10 min, drying temperature of 120 °C, drying time of 30 min, magnetic stirring time of 10 min, ultrasonic vibration for 10 min, centrifugation speed of 12000 r / min, and centrifugation time of 15 min.

[0044] In the fifth group, NS-doped nanoparticles (CNDs-5) were prepared. Arginine was placed in deionized water and magnetically stirred until homogeneous. The mixture was then placed in a reaction vessel. Subsequent drying and crushing steps were the same as in the fourth group and will not be repeated here. The mass of arginine was 4 g, and the volume of deionized water was 30 ml.

[0045] In the preparation of active gold sol-gel, a wet chemical method can be used. This embodiment provides a simple and rapid method for preparing active gold sol-gel, which specifically includes:

[0046] A10. Mix the salt solution containing gold nanoparticles with the substrate preparation agent to obtain the curing solution.

[0047] Specifically, 0.1–0.5 mol / L HAuCl4·3H2O solution, 70% HNO3, and TMOS were mixed for 1–5 minutes to obtain the SERS substrate.

[0048] In addition to the chemical reagents mentioned above, the salt solution containing gold nanoparticles can be replaced with other concentrations or salt solutions, 70% HNO3 can be replaced with other concentrations of nitric acid, hydrochloric acid, etc., and TMOS can also be replaced with other reagents that can be used to prepare SERS substrates.

[0049] A20. The liquid to be cured is drawn into a preset capillary tube and gelled and cured at room temperature to obtain the initial substrate.

[0050] Specifically, the preparation of gel-sol requires processes such as hydrolysis, polymerization, film formation, drying, and calcination. In this embodiment, the metal salt solution and the substrate preparation agent can be directly cross-linked while gradually decomposing silicon oxide. Therefore, the liquid to be cured can be directly applied to a pre-set carrier and allowed to slowly gel and cure at room temperature to obtain the initial substrate.

[0051] In this embodiment, light scattering measurement is performed, and the carrier is made of a transparent material, such as a transparent capillary tube or a glass bottle. Taking a capillary tube as an example, the liquid to be cured can be drawn into the channel of the capillary tube, and then both ends of the capillary tube are sealed and placed at room temperature for gelation and curing. The recommended gelation and curing time is 20-30 hours.

[0052] A30. The initial substrate is reduced using a preset reducing agent to obtain an intermediate substrate.

[0053] Specifically, since the metal in the salt solution still exists in the form of ions in the initial substrate, a reducing agent is needed to reduce the metal ions to form metal nanoparticles, thus obtaining a substrate containing gold nanoparticles, which is the intermediate substrate.

[0054] The reducing agent can be sodium borohydride, hydrogen, sodium citrate, potassium tartrate, etc. Since the metal ions have already made sufficient contact with the TMOS in the substrate in this embodiment, sodium borohydride, which has a strong reducing ability, is used as the reducing agent, with an amount of 10-100 μL and a concentration of 0.01-0.03 mol / L.

[0055] A40. The intermediate substrate is cleaned to obtain the test substrate.

[0056] Specifically, the intermediate substrate is finally cleaned to remove residual reagents such as sodium borohydride, thus avoiding interference with subsequent detection. Cleaning can be performed using ultrapure water, or by first cleaning with an organic solvent followed by ultrapure water.

[0057] S20. The test solution is brought into contact with the detection substrate to obtain the test sample.

[0058] Specifically, after preparing the test solution and the detection substrate, the two are brought into full contact. Taking a capillary tube as the carrier of the detection substrate as an example, the test solution is drawn into the capillary tube through a syringe and brought into contact with the detection substrate in the capillary tube for several minutes to obtain the test sample.

[0059] S30. Irradiate the detection substrate with a preset excitation light and collect the Raman spectrum fed back by the detection substrate to obtain a first control spectrum. Irradiate the test sample with the excitation light and collect the Raman spectrum fed back by the test sample to obtain an experimental spectrum.

[0060] To detect redshift and splitting phenomena, Raman spectra need to be collected from both the test substrate and the sample to be tested.

[0061] An excitation light of a pre-set wavelength is used to irradiate the detection substrate. The current detection substrate contains only active gold and a sol-gel, such as... Figure 2As shown in the middle figure, activated gold also reflects surface features as light. By acquiring the Raman spectrum from the detection substrate, a first control spectrum can be obtained. Using the same excitation light, the sample is irradiated. When the nano-carbon dots in the sample come into contact with the activated gold, the activated gold reflects the excitation light. The Raman spectrum contains the chemical characteristics of the nano-carbon dots in contact with the activated gold. Acquiring the corresponding Raman spectrum yields the experimental spectrum.

[0062] In this embodiment, the detection substrate and the sample to be tested are placed under a detection instrument for separate detection. The detection instrument used in this embodiment for emitting laser light is a portable Raman spectrometer. Since this scheme is based on the redshift and splitting of Raman spectral peaks, infrared light with strong uniformity is used. Furthermore, in this embodiment, the infrared light used is 785 nm. To ensure the accuracy of the measurement, the emission of excitation light and the collection of scattered light are carried out at room temperature in free space.

[0063] In addition, Raman spectroscopy is produced by elastic and inelastic scattering of light on a substance. Therefore, in order to compare different Raman spectral detections, the test solution is also irradiated with excitation light, and the Raman spectrum fed back by the test solution is collected to obtain a second control spectrum.

[0064] S40. Determine the composition of the nano carbon dots based on the first control spectrum and the experimental spectrum.

[0065] Specifically, Figure 2 The second control spectrum (bottom), the first control spectrum (middle), and the experimental spectrum (top) are shown. Here, Raman shift is the Raman shift, intensity is the Raman light intensity, au is an arbitrary unit (dimensionless), and Nano Au refers to gold nanoparticles.

[0066] Characteristic peak fingerprints refer to fingerprints obtained by measuring known pure solutions, exhibiting peaks near relatively fixed wavenumbers in Raman spectra. By comparing characteristic peaks, the presence of certain chemical elements or bonds can be determined. The height of the characteristic peaks is positively correlated with the concentration of the components in the solution, thus it can also be used to estimate component concentrations. Taking the detection substrate as an example, even if the detection substrate does not come into contact with the test solution, it contains chemical substances, thus generating characteristic peak fingerprints corresponding to the detection substrate.

[0067] For example, the characteristic peak of a carbon-carbon bond is 1455 cm⁻¹. -1 Near the wavenumber, the characteristic peaks of the carbon-nitrogen bond are located at 885 and 1054 cm⁻¹. -1 Near the wavenumber. In the first control spectrum, 1455 cm⁻¹ can be seen. -1The presence of distinct peaks near the wavenumber indicates the existence of carbon-carbon bonds in the sample, suggesting the presence of carbon dots in the test solution. Simultaneously, peaks are observed at 885 and 1054 cm⁻¹. -1 The detection of characteristic peaks indicating carbon-nitrogen bonds suggests that the nitrogen doped in the test solution has bonded to the carbon nucleus. Figure 1 In the figure below, although CNDs-4 and CNDs-5 samples were doped with sulfur, no characteristic peak fingerprints of carbon-sulfur bonds were observed. Similarly, no boron-related Raman peaks were observed in the CNDs-2 sample. Therefore, using characteristic peak fingerprints and a second control spectrum can only determine the content of carbon-nitrogen bonds and / or carbon=carbon bonds in the nano-carbon dots.

[0068] according to Figure 1 The middle image shows 354 cm. -1 1051 cm -1 and 1385 cm -1 This is the surface plasmon characteristic peak fingerprint of the gold nanoparticles in this embodiment. Different excitation lights and different methods of preparing the detection substrate may result in different characteristic peak fingerprints. Therefore, based on the second control spectrum, the positions where redshift and splitting may occur in the experimental spectrum can be determined, i.e., the surface plasmon characteristic peak fingerprint of the gold nanoparticles.

[0069] according to Figure 1 In the upper figure, it can be seen that in nitrogen- and sulfur-doped carbon nanoparticles (CNDs-4 and CNDs-5), the characteristic peak fingerprint of the gold nanoparticles is relative to that at 354 cm⁻¹ in the middle figure. -1 The peak position exhibits redshift and splitting, therefore 354 cm⁻¹ is considered the optimal position. -1 In this embodiment, the redshift phenomenon is identified as referring to the position of the reference peak in the first control spectrum. Furthermore, 354 cm⁻¹ -1 The splitting peak produced by the splitting phenomenon is located at a wavelength of 342 cm⁻¹ in the experimental spectrum. -1 With 267 cm -1 Therefore, based on the reference peak, it can be determined whether the test solution contains carbon-sulfur bonds. Since the magnitude of the redshift is related to the concentration of the component causing the redshift, the concentration of carbon-sulfur bonds can be further determined based on the magnitude of the redshift, thereby determining the concentration of carbon sulfides.

[0070] In the above figure, it can also be observed that the characteristic peak fingerprints of gold nanoparticles in nitrogen-doped and nitrogen-boron-doped samples (CNDs-1, CNDs-2, CNDs3) show a significant redshift compared to the reference peak. The redshifted peak position is significantly lower than that at 354 cm⁻¹. -1A left shift occurs. Meanwhile, in the cases of nitrogen-doped and nitrogen-boron-doped samples (CNDs-1, CNDs-2, CNDs3), the splitting effect is not significant, and it can be decomposed into two peaks. Therefore, when the experimental spectrum shows a red shift and double peaks in the mid-infrared region based on the first control spectrum, it is determined that the nanocarbon dots contain nitrogen or a nitrogen-boron mixture.

[0071] Furthermore, the surface plasmon interaction between carbon nanodots and gold nanoparticles in the active gold sol-gel substrate leads to the quenching of the characteristic Raman luminescence of the gold nanoparticles. In the first control spectrum, 1051 cm⁻¹ -1 and 1385 cm -1 The nearby characteristic peak fingerprint is very weak or disappears in the experimental spectrum (e.g.) Figure 2 (As shown in the block diagram in the upper middle section).

[0072] Comparing the first control spectrum, the second control spectrum, and the experimental spectrum, nitrogen- and sulfur-doped carbon nanoparticles on the active gold sol-gel substrate induce a redshift and splitting of low-wavenumber (or mid-infrared) characteristic Raman peaks. This is due to the coupling of nitrogen- and sulfur-doped carbon nanoparticles with surface plasmons of the gold nanoparticles. The gold nanoparticles at 354 cm⁻¹... -1 The characteristic Raman peaks nearby (middle image) can be observed at 342 cm⁻¹ after combining with nitrogen- and sulfur-doped carbon nanoparticles. -1 With 267 cm -1 Split Raman peaks were observed nearby. This unique physical phenomenon provides a rapid, reliable, and low-cost detection method for nitrogen and sulfur impurities, as well as carbon-nitrogen and carbon-sulfur bonds, in nano-carbon dots.

Claims

1. A method for detecting nano-carbon dots, characterized in that, The method includes: Prepare a test solution and a detection substrate containing nano-carbon dots, wherein the substrate contains an active gold sol-gel based on SERS; The test solution is brought into contact with the detection substrate to obtain the test sample; The detection substrate is irradiated with a preset excitation light, and the Raman spectrum fed back by the detection substrate is acquired to obtain a first control spectrum; and, The sample to be tested is irradiated with the excitation light, and the Raman spectrum fed back by the sample to be tested is collected to obtain the experimental spectrum; The composition of the nano carbon dots was determined based on the first control spectrum and the experimental spectrum. The method for preparing the detection substrate includes: A salt solution containing gold nanoparticles is mixed with a substrate preparation agent to obtain a curing solution; The liquid to be cured is drawn into a pre-set capillary tube and gelled and cured at room temperature to obtain an initial substrate; The initial substrate is reduced using a preset reducing agent to obtain an intermediate substrate; The intermediate substrate is cleaned to obtain the test substrate.

2. The method for detecting nano-carbon dots according to claim 1, characterized in that, The nano carbon dots in the test solution contain nitrogen, sulfur and / or boron.

3. The method for detecting nano-carbon dots according to claim 1, characterized in that, The Raman spectrum is in the infrared light band.

4. The method for detecting nano-carbon dots according to claim 3, characterized in that, The excitation wavelength is 785 nm.

5. The method for detecting nano-carbon dots according to claim 1, characterized in that, The step of determining the composition of the nanocarbon dots based on the first control spectrum and the experimental spectrum includes: When a redshift and splitting peak are determined in the experimental spectrum based on the first control spectrum, it is determined that the nano carbon dots contain carbon-sulfur bonds and carbon-nitrogen bonds; The concentration of carbon sulfides is determined based on the redshift magnitude.

6. The method for detecting nano-carbon dots according to claim 5, characterized in that, The splitting peak is located at a wavelength of 342 cm⁻¹ in the experimental spectrum. -1 With 267 cm -1 Place.

7. The method for detecting nano-carbon dots according to claim 1, characterized in that, The step of determining the composition of the nanocarbon dots based on the first control spectrum and the experimental spectrum includes: When the experimental spectrum is redshifted and exhibits double peaks in the mid-infrared region based on the first control spectrum, it is determined that the nano carbon dots contain nitrogen or a nitrogen-boron mixture.

8. The method for detecting nano-carbon dots according to any one of claims 5 to 7, characterized in that, The redshift relative to the position of the reference peak in the first control spectrum is 354 cm⁻¹. -1 .

9. The method for detecting nano-carbon dots according to claim 2, characterized in that, The method further includes: The test solution is irradiated with the excitation light, and the Raman spectrum fed back by the test solution is collected to obtain a second control spectrum; The content of carbon-nitrogen bonds and / or carbon=carbon bonds in the nano carbon dots is determined based on the characteristic peak fingerprint, the second control spectrum, and the experimental spectrum.

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