Carbon nanodot exciplex, and preparation method and application thereof

Abstract

The application discloses a carbon nanodot exciplex and a preparation method and application thereof. Acrylamide, citric acid and urea are dissolved in deionized water to obtain a uniform and transparent mixed solution A; the mixed solution A is subjected to a hydrothermal reaction, and then is subjected to dialysis and freeze-drying to obtain carbon dots; the carbon dots are dissolved in deionized water together with polyacrylamide vinyl carbazole to be fully dissolved by stirring to obtain a mixed solution B; and the mixed solution B is subjected to freeze-drying to obtain a carbon nanodot exciplex photocatalyst. The carbon nanodot exciplex prepared by the application is non-toxic and harmless, can be stored for a long time, and has the advantages of long carrier lifetime; meanwhile, compared with carbon nanodots and ligands, the exciplex can utilize lower-energy photons, and is expected to be used for photocatalytic hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic hydrogen production technology, specifically relating to a carbon nanoparticle excimer complex, its preparation method, and its application. Background Technology

[0002] Excitocomplexes are excited states of intermolecular charge transfer formed between two different molecules, typically physical mixtures of donor and acceptor molecules with biased hole transport properties. In the excited state, electron rearrangement or transfer occurs between the two molecules, resulting in intermolecular charge transfer and the formation of excitocomplexes. Generally, excitocomplexes are unstable and exist only in the excited state. Furthermore, the energy level difference (ΔE) between the lowest excited singlet state (S1) and the lowest excited triplet state (T1) of the excitocomplex is significant. ST The small size of T1 excitons allows them to transform into S1 excitons via reverse intersystem crossing, thus extending carrier lifetime. Therefore, excitocomplexes hold great potential for photocatalysis. Currently, most excitocomplexes are mainly composed of small organic conjugated molecules. Although these materials have long carrier lifetimes, they generally lack hydrophilic groups and inevitably suffer from drawbacks such as complex preparation processes, toxicity, and poor reliability, which are unfavorable for photocatalysis. Furthermore, few excitocomplex organic materials have been reported for photocatalytic hydrogen production. Therefore, it is necessary to design and synthesize novel excitocomplex photocatalytic materials.

[0003] Carbon nanodots (CDs) are zero-dimensional nanomaterials with a particle size of less than 10 nm. They possess excellent properties such as ease of preparation, low cost, low toxicity, and high photostability, attracting great interest from researchers. They are generally composed of elements such as C, H, and O, with the core typically consisting of sp... 2 and sp 3 Hybridized carbon atoms form a multilayered graphitic microcrystalline structure. Designing carbon dot-based excimer complexes requires selecting appropriate carbon nanoparticles (CDs) and ligands. For CDs, the surface functional groups of the carbon dots can be used to modify surface chemistry, improving their hydrophilicity and photocatalytic performance; for example, hydroxyl, carbonyl, or carboxyl groups can be used. The ligands should possess good adsorption properties to immobilize the CDs onto the catalytic substrate. Furthermore, the energy levels of the CDs and ligands must be matched to ensure an effective electron transfer pathway between the ligand and the carbon dots, promoting the formation of the excimer complex. Melamine is a commonly reported ligand in the literature, but it lacks photocatalytic properties and is unsuitable as a ligand. The synthesis of CDs includes methods such as thermal decomposition, hydrothermal synthesis, and microwave-assisted synthesis, but the specific method parameters and conditions need to be adjusted according to the properties of the precursor. To date, few studies have reported on the preparation and photocatalytic applications of carbon nanoparticle excimer complexes. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a carbon nanodot excitocomposite, its preparation method and application. The carbon nanodot excitocomposite prepared by carbon dots and polyacrylamide vinylcarbazole is non-toxic and harmless, can be stored for a long time, can utilize photons with lower energy than carbon dot monomers, and can extend the carrier lifetime, thereby solving the technical problem of short carrier lifetime in nanophotocatalysts.

[0005] The present invention adopts the following technical solution:

[0006] A method for preparing carbon nanodot excimer composites includes the following steps:

[0007] Acrylamide, citric acid and urea were dissolved in deionized water and stirred to obtain a homogeneous and transparent mixed solution A. Mixed solution A was subjected to a hydrothermal reaction, and then carbon dots were obtained by dialyzing and freeze-drying.

[0008] The carbon dots and polyacrylamide vinylcarbazole were dissolved in deionized water and stirred until fully dissolved to obtain mixed solution B.

[0009] The carbon nanodot excimer composite photocatalyst was obtained by freeze-drying the mixed solution B.

[0010] Preferably, the mass ratio of acrylamide, citric acid and urea is (3-4):(0.1-0.5):(3-4).

[0011] Preferably, a uniform and transparent mixed solution A is obtained by stirring with a magnetic stirrer at room temperature.

[0012] Preferably, the temperature at which the mixed solution A undergoes the hydrothermal reaction is 180–200°C.

[0013] Preferably, the dialysis time is 12–24 hours.

[0014] Preferably, the mass ratio of carbon dots to polyacrylamide vinylcarbazole is (0.01-2.0):(0.01-2.0).

[0015] Preferably, mixed solution B is obtained by stirring at room temperature for 10-20 minutes.

[0016] Preferably, the freeze-drying time is 24–48 hours.

[0017] Another technical solution of the present invention is a carbon nanodot excimer complex.

[0018] Another technical solution of the present invention is the application of carbon nanodot excimer complex in photocatalytic reduction of methanol to produce hydrogen.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] A method for preparing carbon nanodot excitocomplexes involves synthesizing carbon nanodots from acrylamide, citric acid, and urea as precursors via a hydrothermal method, and then freeze-drying the carbon nanodots with commercially available polyacrylamide vinylcarbazole to obtain the carbon nanodot excitocomplexes. The preparation method is simple, low-cost, and has a short preparation cycle.

[0021] Furthermore, the mass ratio of acrylamide, citric acid, and urea can be adjusted to control the surface properties of the carbon dots.

[0022] Furthermore, by setting the hydrothermal reaction temperature to 180–200°C, the reaction pressure can be controlled, thereby controlling the degree of carbonization of the carbon dot precursor.

[0023] Furthermore, setting the dialysis time to 12–24 hours can remove residual reaction materials and impurities, making the sample purer.

[0024] Furthermore, the purpose of setting the mass ratio of carbon dots to polyacrylamide vinylcarbazole is to control the composition and properties of the carbon nanodot excimer composite.

[0025] Further, stir for 10–20 minutes to obtain a mixed solution, ensuring that the two monomers are fully dissolved and mixed to form a homogeneous solution.

[0026] The carbon nanoparticle-based excimer complex prepared by this invention has a porous structure and abundant active sites, which is beneficial for photon capture and separation of photogenerated charges. It is suitable for applications such as photocatalytic hydrogen production and has broad application prospects.

[0027] In summary, the carbon nanodot excimer complex prepared by this invention is non-toxic, harmless, and can be stored for a long time, with the advantage of long carrier lifetime. At the same time, compared with carbon nanodots and ligands, this excimer complex can utilize photons with lower energy, and is expected to be used for photocatalytic hydrogen production.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a transmission electron microscope image of the carbon nanodot excimer composite prepared in Example 1 of the present invention;

[0030] Figure 2 The excitation spectrum of the carbon nanodot excimer composite prepared in Example 1 of this invention;

[0031] Figure 3 The fluorescence emission pattern of carbon nanodots and polyacrylamide vinylcarbazole prepared in Example 1 of this invention;

[0032] Figure 4The fluorescence emission patterns of the carbon nanodot excimer composite prepared in Example 1 of this invention at different excitation wavelengths are shown.

[0033] Figure 5 The fluorescence lifetime diagram shows the carbon nanodots, polyacrylamide vinylcarbazole and carbon nanodot excitosome complex prepared in Example 1 of this invention.

[0034] Figure 6 The photocatalytic performance of carbon nanodots, polyacrylamide vinylcarbazole and carbon nanodot excimer complex prepared in Example 1 of this invention is shown in the figure.

[0035] Figure 7 This is a schematic diagram illustrating the stability of the photocatalytic performance of the carbon nanodot excimer composite prepared in Example 1 of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0038] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0039] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0040] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0041] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0042] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0043] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0044] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0045] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0046] This invention provides a carbon nanodot excitopolymer, its preparation method, and its application. Acrylamide, citric acid, and urea are dissolved in deionized water and stirred until fully dissolved to obtain a mixed solution. This solution is then subjected to a hydrothermal reaction followed by dialyzing and freeze-drying to obtain carbon dots. The carbon dots and polyacrylamide vinylcarbazole (PAMCz) are then stirred in deionized water until fully dissolved to obtain a mixed solution. This mixed solution is then freeze-dried to obtain the carbon nanodot excitopolymer. The carbon nanodots prepared by this invention are non-toxic and harmless, exhibit a redshift in absorption, have a long carrier lifetime, and can be stored for extended periods, making them suitable for photocatalysis.

[0047] This invention designs a carbon dot based on citric acid, acrylamide, and urea. This carbon dot has hydrophilic groups such as carboxyl, carbon, and hydroxyl groups. For the first time, the water-soluble polymer material polyacrylamide vinylcarbazole (PAMCz) is used as the ligand. The carbon dot and polyacrylamide vinylcarbazole are physically blended in a certain ratio. The donor-acceptor pair is synthesized by designing the coulombic attraction to prepare the carbon nanodot excitosome complex.

[0048] This invention discloses a method for preparing carbon nanodot excimer composites, comprising the following steps:

[0049] S1. Acrylamide, citric acid and urea are dissolved in deionized water at a mass ratio of 3-4:0.1-0.5:3-4. The mixture is stirred at room temperature with a magnetic stirrer to ensure complete dissolution, resulting in a homogeneous and transparent mixed solution A. Mixed solution A is placed in a reaction vessel and subjected to hydrothermal reaction at 180-200℃. The mixture is dialyzed for 12-24 hours and then freeze-dried to obtain carbon dots.

[0050] S2. Dissolve the carbon dots obtained in step S1 with polyacrylamide vinylcarbazole in deionized water at a mass ratio of (0.01-2.0):(0.01-2.0). Stir with a magnetic stirrer at room temperature for 10-20 minutes to ensure complete dissolution and obtain mixed solution B.

[0051] S3. Freeze-dry the mixed solution B for 24–48 h to obtain the carbon nanodot excimer composite photocatalyst.

[0052] The carbon nanodot excitocomposite prepared by the method of the present invention has a yield of 100%. The absorption peak of the carbon nanodot excitocomposite shows a red shift relative to the carbon nanodots, the lifetime of carbon dot charge carriers increases from 3.37 ns to 7.85 ns, and the photocatalytic hydrogen production efficiency increases from 1.1 mmol / gh (CDs) and 0.1 mmol / gh (polyacrylamide vinylcarbazole) to 5.4 mmol / gh.

[0053] Based on spectroscopic characterization, the evidence for carbon nanodot excimer complexes is as follows:

[0054] (1) This can be verified from the absorption.

[0055] The absorptions of CDs and polyacrylamide vinylcarbazole are at 337 and 342 nm, respectively, and the absorption of the carbon nanodot excitopolymer is also around 340 nm. However, the excitation spectrum shows that the absorption of the excited state has redshifted, which means that CDs and polyacrylamide vinylcarbazole interact in the excited state to form a new energy level.

[0056] (2) Verification can be made from fluorescence.

[0057] The carbon nanodot excimer complex exhibited different luminescent properties compared to CDs and polyacrylamide vinylcarbazole: the fluorescence peak of carbon dots generally showed excitation wavelength dependence, meaning the position of the fluorescence peak differed depending on the excitation wavelength. The fluorescence peak of CDs redshifted from 410 nm (excitation wavelength 320 nm) to 450 nm (excitation wavelength 400 nm). In contrast, polyacrylamide vinylcarbazole was wavelength-independent; when the excitation wavelength was less than 340 nm, its fluorescence peak was always located at 360 nm. The fluorescence of the carbon nanodot excimer complex did not show the characteristic peak of polyacrylamide vinylcarbazole and did not exhibit excitation wavelength dependence; the fluorescence peak appeared at 406 nm.

[0058] (3) Fluorescence lifetime can be verified

[0059] The carbon nanodot excitopolymer exhibits a different carrier lifetime than CDs and polyacrylamide vinylcarbazole. The fluorescence intensity of CDs shows a double exponential decay, consistent with the non-uniform structural size of the carbon dots. Both the carbon nanodot excitopolymer and polyacrylamide vinylcarbazole show a single exponential decay, and their lifetimes differ. This suggests that the carbon nanodot excitopolymer is a pure phase with only one excited state level. The different lifetimes indicate that this excited state level is not that of CDs or polyacrylamide vinylcarbazole, but rather represents the creation of a new energy level.

[0060] The carbon nanodot excitopolymer of this invention is non-toxic, harmless, and can be stored for a long time, with the advantages of long carrier lifetime. At the same time, compared with carbon nanodots and ligands, the carbon nanodot excitopolymer prepared by this invention has a porous structure and abundant active sites, which is beneficial to photon capture and separation of photogenerated charges. It can utilize photons with lower energy and is suitable for use in the field of photocatalytic hydrogen production, with broad application prospects.

[0061] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0062] Example 1

[0063] Step 1: Dissolve acrylamide, citric acid and urea in deionized water in a ratio of 4g:0.5g:4g. Stir at room temperature to ensure complete dissolution and obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 24 hours and freeze dry for 48 hours to obtain carbon dots.

[0064] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 0.12g:1.2g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0065] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0066] Please see Figure 1 The carbon nanodots prepared by this invention have a diameter of about 4.1 nm and a lattice fringe spacing of 0.21 nm, corresponding to the

[100] crystal plane of graphite, indicating that the product is a carbon-based material.

[0067] Please see Figure 2 The excitation spectrum of the carbon nanodot excimer composite prepared in this invention exhibits a redshift relative to CDs and PAMCz, which indicates that the composite material interacts in the excited state.

[0068] Please see Figure 3The fluorescence of the carbon nanodots prepared by this invention is wavelength-dependent, with the optimal emission wavelength of the carbon nanodots being 340 nm. Commercially available polyacrylamide vinylcarbazole, on the other hand, is wavelength-independent, with its fluorescence peak located at 366 nm.

[0069] Please see Figure 4 Unlike carbon nanodots, the carbon nanodot excimer complex does not show excitation wavelength dependence; when the excitation wavelength is 320 to 380 nm, the fluorescence peak position is always at 406 nm.

[0070] Please see Figure 5 The fluorescence lifetime of the carbon nanodot excimer complex prepared in this invention is significantly improved compared to that of carbon nanodots, extending from 3.37 ns to 7.85 ns. Simultaneously, the fluorescence decay curve changes from a double-exponential decay of carbon nanodots to a single-exponential decay, and the decay curve differs from that of polyacrylamide vinylcarbazole, demonstrating the generation of new energy levels and further proving the formation of the excimer complex.

[0071] Please see Figure 6 Under simulated solar lamp conditions without the addition of Pt co-catalyst, and in a reaction environment of 100 mL methanol (containing 10 g sodium hydroxide), the performance of this carbon nanodot in reducing methanol to produce hydrogen was 1.1 mmol / gh. However, the carbon nanodot excimer composite prepared in this invention has a hydrogen production capacity as high as 5.4 mmol / gh, which is the highest performance reported in the literature to date for photocatalytic reduction of methanol to produce hydrogen.

[0072] Please see Figure 7 Under simulated solar lamp conditions and without the addition of Pt co-catalyst, the photocatalytic activity of the carbon nanoparticle excitopolymer complex was stable in a reaction environment of 100 mL methanol (containing 10 g sodium hydroxide).

[0073] Example 2

[0074] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 3g:0.2g:3g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 180℃. Further dialyze for 18h and freeze dry for 48h to obtain carbon dots.

[0075] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 0.01g:2.0g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0076] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0077] The composite prepared in this example did not produce a carbon nanodot excimer complex; the fluorescence primarily showed luminescence from polyacrylamide vinylcarbazole, without any luminescence information from the carbon nanodots. The sample had a carrier lifetime of 10.4 ns and a photocatalytic hydrogen production performance of 0.3 mmol / gh.

[0078] Example 3

[0079] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 4g:0.1g:3g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 24h and freeze dry for 36h to obtain carbon dots.

[0080] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 0.12g:2.0g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0081] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0082] The carbon nanodot excimer composite prepared in this example exhibited a new fluorescence peak (406 nm) similar to that in Example 1, without excitation wavelength dependence, and the fluorescence peak did not show the characteristic peaks of carbon nanodots or polyacrylamide vinylcarbazole. The carrier lifetime of this sample was 8.20 ns, and the photocatalytic hydrogen production performance was 5.00 mmol / gh.

[0083] Example 4

[0084] Step 1: Dissolve acrylamide, citric acid and urea in deionized water in a ratio of 4g:0.5g:4g. Stir at room temperature to ensure complete dissolution and obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 180℃. Further dialyze for 24 hours and freeze dry for 48 hours to obtain carbon dots.

[0085] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 0.60g:2.0g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0086] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0087] The carbon nanodot excimer composite prepared in this example exhibited a new fluorescence peak (406 nm) similar to that in Example 1, without excitation wavelength dependence, and the fluorescence peak did not show the characteristic peaks of carbon nanodots or polyacrylamide vinylcarbazole. The carrier lifetime of this sample was 6.20 ns, and the photocatalytic hydrogen production performance was 4.20 mmol / gh.

[0088] Example 5

[0089] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 4g:0.3g:3g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out hydrothermal reaction at 200℃. Further dialyze for 12h and freeze dry for 24h to obtain carbon dots.

[0090] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 1.20g:2.0g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0091] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0092] The carbon nanodot excimer composite prepared in this example exhibited a new fluorescence peak (410 nm) similar to that in Example 1, without excitation wavelength dependence, and the fluorescence peak did not show the characteristic peaks of carbon nanodots or polyacrylamide vinylcarbazole. The carrier lifetime of this sample was 4.40 ns, and the photocatalytic hydrogen production performance was 3.80 mmol / gh.

[0093] Example 6

[0094] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 3g:0.1g:4g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out hydrothermal reaction at 200℃. Further dialyze for 18h and freeze dry for 48h to obtain carbon dots.

[0095] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 1.50g:2.0g, and stir for 10 minutes to fully dissolve them to obtain mixed solution B;

[0096] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0097] This example did not produce a carbon nanodot excimer complex; the fluorescence spectrum simultaneously exhibited characteristic peaks for both carbon nanodots and polyacrylamide vinylcarbazole. The sample had a carrier lifetime of 3.80 ns and a photocatalytic hydrogen production performance of 2.80 mmol / gh.

[0098] Example 7

[0099] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 4g:0.5g:4g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 180℃. Further dialyze for 12 hours and freeze dry for 24 hours to obtain carbon dots.

[0100] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2g:0.01g, and stir for 10 minutes to obtain mixed solution B.

[0101] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0102] This example did not produce a carbon nanodot excimer complex; the fluorescence spectrum only showed the characteristic peaks of carbon nanodots. The carrier lifetime of this sample was 3.20 ns, and the photocatalytic hydrogen production performance was 1.80 mmol / gh.

[0103] Example 8

[0104] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 3g:0.2g:4g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 24h and freeze dry for 24h to obtain carbon dots.

[0105] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2.0g:0.12g, and stir for 10 minutes to fully dissolve them to obtain mixed solution B;

[0106] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0107] This example did not produce a carbon nanodot excimer complex; the fluorescence spectrum only showed the characteristic peaks of carbon nanodots. The carrier lifetime of this sample was 3.80 ns, and the photocatalytic hydrogen production performance was 2.10 mmol / gh.

[0108] Example 9

[0109] Step 1: Dissolve acrylamide, citric acid and urea in deionized water in a ratio of 4g:0.5g:4g. Stir at room temperature to ensure complete dissolution and obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 24 hours and freeze dry for 48 hours to obtain carbon dots.

[0110] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2.0g:0.48g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0111] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0112] The carbon nanodot excimer composite prepared in this example exhibited a new fluorescence peak (412 nm) similar to that in Example 1, without excitation wavelength dependence, and the fluorescence peak did not show the characteristic peaks of carbon nanodots or polyacrylamide vinylcarbazole. The carrier lifetime of this sample was 4.90 ns, and the photocatalytic hydrogen production performance was 4.30 mmol / gh.

[0113] Example 10

[0114] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 3g:0.4g:4g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 12h and freeze dry for 36h to obtain carbon dots.

[0115] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2.0g:0.60g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0116] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0117] The carbon nanodot excimer composite prepared in this example exhibited a new fluorescence peak (416 nm) similar to that in Example 1, without excitation wavelength dependence, and the fluorescence peak did not show the characteristic peaks of carbon nanodots or polyacrylamide vinylcarbazole. The carrier lifetime of this sample was 5.70 ns, and the photocatalytic hydrogen production performance was 4.80 mmol / gh.

[0118] Example 11

[0119] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 4g:0.1g:3g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 24h and freeze dry for 48h to obtain carbon dots.

[0120] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2.0g:0.80g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0121] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0122] The carbon nanodot excimer composite prepared in this example exhibited a new fluorescence peak (416 nm) similar to that in Example 1, without excitation wavelength dependence, and the fluorescence peak did not show the characteristic peaks of carbon nanodots or polyacrylamide vinylcarbazole. The carrier lifetime of this sample was 6.30 ns, and the photocatalytic hydrogen production performance was 4.40 mmol / gh.

[0123] Example 12

[0124] Step 1: Dissolve acrylamide, citric acid and urea in deionized water in a ratio of 4g:0.5g:4g. Stir at room temperature to ensure complete dissolution and obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 24 hours and freeze dry for 48 hours to obtain carbon dots.

[0125] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2.0g:1.0g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0126] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0127] This example did not produce a carbon nanodot excimer complex; the fluorescence spectrum simultaneously exhibited characteristic peaks for both carbon nanodots and polyacrylamide vinylcarbazole. The sample had a carrier lifetime of 7.40 ns and a photocatalytic hydrogen production performance of 3.80 mmol / gh.

[0128] Example 13

[0129] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 3g:0.3g:4g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out hydrothermal reaction at 200℃. Further dialyze for 24h and freeze dry for 36h to obtain carbon dots.

[0130] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2.0g:1.5g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0131] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0132] This example did not generate a carbon nanodot excimer complex; the fluorescence spectrum simultaneously exhibited characteristic peaks for both carbon nanodots and polyacrylamide vinylcarbazole. The sample had a carrier lifetime of 8.20 ns and a photocatalytic hydrogen production performance of 2.30 mmol / gh.

[0133] Example 14

[0134] Step 1: Dissolve acrylamide, citric acid and urea in deionized water according to the ratio of 4g:0.5g:3g. Stir at room temperature to fully dissolve them to obtain a homogeneous and transparent mixed solution A. Place mixed solution A in a reaction vessel and carry out a hydrothermal reaction at 200℃. Further dialyze for 24h and freeze dry for 48h to obtain carbon dots.

[0135] Step 2: Dissolve carbon dots and polyacrylamide vinylcarbazole in deionized water at a ratio of 2.0g:2.0g, and stir for 20 minutes to ensure complete dissolution, thus obtaining mixed solution B;

[0136] Step 3: Freeze-dry the mixed solution B for 48 hours to obtain the carbon nanodot excimer composite photocatalyst.

[0137] This example did not generate a carbon nanodot excimer complex; the fluorescence spectrum simultaneously exhibited characteristic peaks for both carbon nanodots and polyacrylamide vinylcarbazole. The sample had a carrier lifetime of 9.10 ns and a photocatalytic hydrogen production performance of 1.50 mmol / gh.

[0138] In summary, this invention provides a carbon nanoparticle-based excimer composite, its preparation method, and its application. The carbon nanoparticle-based excimer composite can respond to a wider wavelength spectrum, making full use of sunlight, while also extending carrier lifetime and effectively improving photocatalytic hydrogen production efficiency.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing carbon nanodot excimer composites, characterized in that, Includes the following steps: Acrylamide, citric acid and urea were dissolved in deionized water and stirred to obtain a homogeneous and transparent mixed solution A. The mass ratio of acrylamide, citric acid and urea was (3~4):(0.1~0.5):(3~4). Mixed solution A was subjected to a hydrothermal reaction at a temperature of 180~200 ℃. Then, carbon dots were obtained by dialysis and freeze-drying. The carbon dots and polyacrylamide vinylcarbazole were dissolved in deionized water and stirred until fully dissolved to obtain mixed solution B. The mass ratio of carbon dots to polyacrylamide vinylcarbazole was (0.12~0.60):(1.2~2.0). The carbon nanodot excimer composite photocatalyst was obtained by freeze-drying the mixed solution B.

2. The method for preparing carbon nanodot excimer composites according to claim 1, characterized in that, A homogeneous and transparent mixed solution A was obtained by stirring with a magnetic stirrer at room temperature.

3. The method for preparing carbon nanodot excimer composites according to claim 1, characterized in that, The dialysis time is 12-24 hours.

4. The method for preparing carbon nanodot excimer composites according to claim 1, characterized in that, Stir at room temperature for 10-20 minutes to obtain mixed solution B.

5. The method for preparing carbon nanodot excimer composites according to claim 1, characterized in that, The freeze-drying time is 24~48 h.

6. The carbon nanodot excimer composite prepared by the method according to any one of claims 1 to 5.

7. The application of the carbon nanodot excimer complex according to claim 6 in the photocatalytic reduction of methanol to produce hydrogen.

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