A composite hydrogel material containing carbon quantum dots, a preparation method thereof, and applications thereof

Abstract

The present invention provides a composite hydrogel material containing carbon quantum dots, a preparation method and application thereof, and relates to the technical field of hydrogel preparation. The composite hydrogel material of the present invention is prepared by using hydrogen peroxide and ascorbic acid to initiate the redox polymerization of N-isopropyl acrylamide, acrylamide and N-N'-methylene bisacrylamide in a mass ratio of 0.30-0.50:0-0.03:0.01. The process of the present invention is simple and rapid, has strong scalability, and is easy to mass produce. The prepared hydrogel material is used for Fe 3+ The detection has strong blue fluorescence, and the fluorescence is stable, and at the same time has different transition temperatures, which meets the practical application requirements in the field of fluorescence detection.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogel preparation, and in particular to a composite hydrogel material containing carbon quantum dots, and a preparation method and application thereof. Background Art

[0002] On the one hand, the element iron (Fe) is ubiquitous in biological systems and the natural environment. For example, the human body contains approximately 4-5 grams of iron in various forms. 3+ Ions are transition metal ions that are involved in many metabolic processes, including oxygen transport, DNA synthesis, and electron transport. 3+ Fe ions can cause tissue or organ damage associated with diseases such as hepatitis, hemochromatosis, organ dysfunction, and neurodegenerative diseases. 3+ Testing is of great significance.

[0003] Fluorescence spectroscopy has attracted significant attention due to its simplicity, high sensitivity, and rapid response. Quantum dots (QDs) have become a promising nanomaterial for fluorescence-based sensing applications due to their high quantum yield, excellent photostability, and exceptionally broad absorption band (allowing for a wide range of excitation wavelengths). However, a major challenge with QD-based sensors is that the QD probes typically need to be mixed with the target water sample for subsequent fluorescence measurement, hindering rapid on-site detection. Therefore, QDs can be loaded into 3D networks of hydrogels, which provide chemical stability for the QDs. In turn, the incorporation of QDs improves the structure and properties of the hydrogels to a certain extent. The highly tunable 3D structure and high surface area of the hydrogels enable them to accommodate a variety of micro- and nanoparticles, effectively preventing clustering and significantly improving the fluorescence stability of the QDs. This allows for on-site detection of heavy metal ions in aqueous environments by monitoring changes in fluorescence intensity. Therefore, the development of facile, low-cost 3D fluorescence sensors with both fluorescence stability and metal ion detection performance remains a key challenge. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite hydrogel material containing carbon quantum dots and its preparation method and application, so as to solve the problems existing in the above-mentioned prior art and to obtain Fe 3+ Fluorescence detection of hydrogel materials.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the purposes of the present invention is to provide a method for preparing a composite hydrogel material containing carbon quantum dots, wherein the composite hydrogel material containing carbon quantum dots is prepared by utilizing the redox initiation of hydrogen peroxide and ascorbic acid to polymerize N-isopropylacrylamide, acrylamide, and N-N'-methylenebisacrylamide in a mass ratio of 0.30-0.50:0-0.03:0.01.

[0007] Furthermore, the molar ratio of the hydrogen peroxide to ascorbic acid is 1:1.

[0008] Furthermore, the mass ratio of N-isopropylacrylamide, acrylamide, N-N'-methylenebisacryloyl and ascorbic acid is 0.30-0.50:0-0.03:0.01:0.02-0.08.

[0009] Furthermore, the preparation method of the composite hydrogel material containing carbon quantum dots specifically includes the following steps:

[0010] (1) N-isopropylacrylamide, acrylamide, and N-N'-methylenebisacrylamide were mixed according to a mass ratio, and ascorbic acid was added. The obtained mixture 1 was dissolved in water, and ultrasonic treatment was performed to obtain a mixture 2;

[0011] (2) Under ice bath conditions (below 5° C.), hydrogen peroxide is added to the mixture 2, refrigerated, and then heat-treated to obtain the composite hydrogel material containing carbon quantum dots.

[0012] Furthermore, in step (1), the ratio of water to N-isopropylacrylamide, acrylamide and N-N'-methylenebisacrylamide is: 3.52 mL-3.88 mL: 0.30-0.50 g: 0-0.03 g: 0.01 g.

[0013] Furthermore, in step (2), the refrigeration temperature is 0-5°C and the time is 12-24 hours; the heat treatment temperature is 85-90°C and the time is 2-3 hours.

[0014] The second object of the present invention is to provide a composite hydrogel material containing carbon quantum dots obtained by the above preparation method.

[0015] The third object of the present invention is to provide the composite hydrogel material containing carbon quantum dots in Fe 3+ Application in detection.

[0016] The fourth object of the present invention is to provide a method for detecting Fe 3+ The fluorescent sensor comprises the composite hydrogel material containing carbon quantum dots.

[0017] The present invention utilizes hydrogen peroxide-ascorbic acid redox-initiated polymerization to prepare a composite hydrogel material containing carbon quantum dots. The fluorescence properties of the resulting composite hydrogel are regulated by controlling the ascorbic acid content and pH. Simultaneously, by regulating the ratio of N-isopropylacrylamide to acrylamide in the hydrogel, poly (N-isopropylacrylamide) / acrylamide hydrogels with different volume transition temperatures are prepared.

[0018] The present invention discloses the following technical effects:

[0019] (1) The preparation method of the present invention has a simple and rapid process, strong scalability, and is easy to mass produce.

[0020] (2) The present invention provides a method for 3+ A simple preparation method for carbon quantum dot-doped composite hydrogel sensors for detection. The special three-dimensional structure hydrogel material containing carbon quantum dots obtained by this method has strong blue fluorescence and different transition temperatures, which can realize Fe 3+ The fluorescence is stable and meets the practical application requirements in the field of fluorescence detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 TEM images of the carbon quantum dots (a) prepared in Example 1 of the present invention and the hydrogel (b) prepared in Example 2;

[0023] Figure 2 (a) is the fluorescence spectrum of the hydrogel prepared in Example 2-5 of the present invention, Figure 2 (b) is the fluorescence lifetime of the carbon quantum dots in aqueous solution of Example 1 and in the hydrogel of Example 2;

[0024] Figure 3 (a) shows the effect of different pH solutions on the fluorescence intensity of the hydrogel in Example 2. Figure 3 (b) Effect of storage time at room temperature on the fluorescence intensity of the hydrogel in Example 2;

[0025] Figure 4 (a) is the F / F0 diagram of the hydrogel in Example 2 for different metal ions, Figure 4 (b) is the Fe 3+ Emission spectrum of Example 2 hydrogel in solution (λex = 340 nm);

[0026] Figure 5 These are the DSC curves of the hydrogels prepared in Example 2 and Examples 6-8 of the present invention. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] Example 1

[0033] (1) 0.06 g of ascorbic acid and 0.36 mL of hydrogen peroxide (3 wt%) were placed in a beaker, dissolved in 3.64 mL of deionized water by magnetic stirring, and then sonicated for 5 min in a 400 W ultrasonic machine.

[0034] (2) The mixture prepared in step (1) was placed in a hot water bath at 90° C. for 2 h to obtain carbon quantum dots (CQDs).

[0035] Example 2

[0036] (1) 0.50 g of N-isopropylacrylamide, 0.01 g of N-N'-methylenebisacrylamide, and 0.06 g of ascorbic acid were placed in a beaker, dissolved in 3.64 mL of deionized water by magnetic stirring, and then sonicated in a 400 W ultrasonic machine for 10 min.

[0037] (2) The mixture prepared in step (1) was placed in an ice-water bath (below 5°C), and 0.36 mL of 3% hydrogen peroxide (with a molar ratio of 1:1 to ascorbic acid) was added with stirring. The mixture was then poured into a mold. After incubation in a refrigerator at 5°C for 24 hours, the hydrogel was removed from the mold and finally reacted in an oven at 90°C for 2 hours to obtain a carbon quantum dot-poly (N-isoacrylamide) hydrogel (labeled as C6-PN50).

[0038] Example 3

[0039] (1) 0.50 g of N-isopropylacrylamide, 0.01 g of N-N'-methylenebisacrylamide, and 0.02 g of ascorbic acid were placed in a beaker, dissolved in 3.88 mL of deionized water by magnetic stirring, and then sonicated in a 400 W ultrasonic machine for 10 min.

[0040] (2) The mixture prepared in step (1) was placed in an ice-water bath (below 5°C), and 0.12 mL of 3% hydrogen peroxide (with a molar ratio of 1:1 to ascorbic acid) was added with stirring. The mixture was then poured into a mold. After incubation in a refrigerator at 5°C for 24 hours, the hydrogel was removed from the mold and finally reacted in an oven at 90°C for 2 hours to obtain a carbon quantum dot-poly (N-isoacrylamide) hydrogel (labeled as C2-PN50).

[0041] Example 4

[0042] (1) 0.50 g of N-isopropylacrylamide, 0.01 g of N-N'-methylenebisacrylamide, and 0.04 g of ascorbic acid were placed in a beaker, dissolved in 3.76 mL of deionized water by magnetic stirring, and then sonicated in an ultrasonic machine at a power of 400 W for 10 min;

[0043] (2) The mixture prepared in step (1) was placed in an ice-water bath (below 5°C), and 0.24 mL of 3% hydrogen peroxide (with a molar ratio of 1:1 to ascorbic acid) was added with stirring. The mixture was then poured into a mold. After incubation in a refrigerator at 5°C for 24 hours, the hydrogel was removed from the mold and finally reacted in an oven at 90°C for 2 hours to obtain a carbon quantum dot-poly (N-isoacrylamide) hydrogel (labeled as C4-PN50).

[0044] Example 5

[0045] (1) 0.50 g of N-isopropylacrylamide, 0.01 g of N-N'-methylenebisacrylamide, and 0.08 g of ascorbic acid were placed in a beaker, dissolved in 3.52 mL of deionized water by magnetic stirring, and then sonicated in a 400 W ultrasonic machine for 10 min.

[0046] (2) The mixture prepared in step (1) was placed in an ice-water bath (below 5°C), and 0.48 mL of 3% hydrogen peroxide (with a molar ratio of 1:1 to ascorbic acid) was added with stirring. The mixture was then poured into a mold. After incubation in a refrigerator at 5°C for 24 hours, the hydrogel was removed from the mold and finally reacted in an oven at 90°C for 2 hours to obtain a carbon quantum dot-poly (N-isoacrylamide) hydrogel (labeled as C8-PN50).

[0047] Example 6

[0048] (1) 0.49 g of N-isopropylacrylamide, 0.01 g of acrylamide, 0.01 g of N-N'-methylenebisacrylamide, and 0.06 g of ascorbic acid were placed in a beaker, dissolved in 3.64 mL of deionized water by magnetic stirring, and then sonicated in an ultrasonic machine at a power of 400 W for 10 min;

[0049] (2) The mixture prepared in step (1) was placed in an ice-water bath (below 5°C), and 0.36 mL of 3% hydrogen peroxide (with a molar ratio of 1:1 to ascorbic acid) was added with stirring, and then poured into a mold. After incubation in a refrigerator at 5°C for 24 hours, the hydrogel was removed from the mold and finally reacted in an oven at 90°C for 2 hours to obtain a carbon quantum dot-poly (N-isoacrylamide) / acrylamide hydrogel (C6-PN49A1).

[0050] Example 7

[0051] (1) 0.48 g of N-isopropylacrylamide, 0.02 g of acrylamide, 0.01 g of N-N'-methylenebisacrylamide, and 0.06 g of ascorbic acid were placed in a beaker, dissolved in 3.64 mL of deionized water by magnetic stirring, and then sonicated in a 400 W ultrasonic machine for 10 min.

[0052] (2) The mixture prepared in step (1) was placed in an ice-water bath (below 5°C), and 0.36 mL of 3% hydrogen peroxide (with a molar ratio of 1:1 to ascorbic acid) was added with stirring, and then poured into a mold. After incubation in a refrigerator at 5°C for 24 hours, the hydrogel was removed from the mold and finally reacted in an oven at 90°C for 2 hours to obtain a carbon quantum dot-poly (N-isoacrylamide) / acrylamide hydrogel (C6-PN48A2).

[0053] Example 8

[0054] (1) 0.47 g of N-isopropylacrylamide, 0.03 g of acrylamide, 0.01 g of N-N'-methylenebisacrylamide, and 0.06 g of ascorbic acid were placed in a beaker, dissolved in 3.64 mL of deionized water by magnetic stirring, and then sonicated in an ultrasonic machine at a power of 400 W for 10 min;

[0055] (2) The mixture prepared in step (1) was placed in an ice-water bath (below 5°C), and 0.36 mL of 3% hydrogen peroxide (with a molar ratio of 1:1 to ascorbic acid) was added with stirring, and then poured into a mold. After incubation in a refrigerator at 5°C for 24 hours, the hydrogel was removed from the mold and finally reacted in an oven at 90°C for 2 hours to obtain a carbon quantum dot-N-isoacrylamide / acrylamide hydrogel (C6-PN47A3).

[0056] The materials prepared in the examples were characterized using a FEI TECNALG2 transmission electron microscope from the Netherlands. Figure 1 .

[0057] in Figure 1 (a) is a TEM image of carbon quantum dots prepared in Example 1. Figure 1 (b) is a TEM image of the hydrogel prepared in Example 2 (inset: HRTEM image). Figure 1 It can be seen that the CQDs obtained in Example 1 aggregated and their shape was close to spherical with a size of 4.1-6.3 nm. However, the CQDs were evenly dispersed in the aerogel prepared in Example 2 and almost no aggregation was observed. Figure 1 b), lattice fringes can be clearly observed. After measurement, the spacing between the lattice fringes is 0.203 nm and they are equidistant from each other, which is very consistent with the spacing corresponding to the (101) peak of graphite, indicating that the quantum dots are a homogeneous monodisperse graphite crystal structure.

[0058] The excitation spectrum scanning, emission spectrum scanning and fluorescence lifetime test of the hydrogel were performed using a Canadian QuantaMaster 8000 steady-state transient fluorescence spectrometer. The results are shown in Figure 2-4 .

[0059] Figure 2 (a) is the fluorescence spectrum of the hydrogel prepared in Example 2-5, Figure 2 (b) is the fluorescence lifetime of the carbon quantum dots in aqueous solution of Example 1 and in the hydrogel of Example 2. Figure 2It can be seen that the fluorescence intensity of the hydrogels of Examples 2-5 is the strongest at 410nm under the excitation wavelength of 340nm, which are 67741.52, 96682.72, 148523.719 and 153003.875 CPS respectively. When the optimal excitation wavelength is 340nm, Example 2 has the strongest fluorescence emission peak at 410nm, which is mainly attributed to the n-π* transition in the CQDs molecular state region. In addition, according to the relevant calculation formula The relative quantum yield (QY) can be calculated to be 11.6%, and the fluorescence lifetimes in aqueous solution and hydrogel are 1.435 ns and 2.138 ns, respectively.

[0060] Figure 3 (a) shows the effect of different pH solutions on the fluorescence intensity of the hydrogel in Example 2. Figure 3 (b) shows the effect of standing time at room temperature on the fluorescence intensity of the hydrogel in Example 2. Figure 3 It can be seen that the fluorescence performance of the hydrogel in Example 2 reaches its highest at pH = 4, and it still has fluorescence performance after being placed at room temperature for 5 days.

[0061] Figure 4 (a) is the F / F0 diagram of the hydrogel in Example 2 for different metal ions, Figure 4 (b) is the Fe 3+ The emission spectrum of Example 2 hydrogel in solution (λex=340nm) is shown in FIG. Figure 4 It can be seen that as a fluorescent probe, the hydrogel of Example 2 exhibits 3+ The fluorescence quenching selectivity of Fe 3+ Exhibits highly sensitive and specific fluorescence response.

[0062] The volume transition temperature of the hydrogel was analyzed using a German NETZSCH 204 differential scanning calorimeter. Figure 5 The DSC curves of the hydrogels prepared in Example 2 and Examples 6-8 are shown in FIG. Figure 5 As can be seen, endothermic peaks were observed in all hydrogel materials. This endothermic transition is due to the hydrophobic hydration of the isopropyl groups of the NIPAM component in the hydrogel. Increasing the acrylamide content in the hydrogel (decreasing the N-isopropylacrylamide content) can increase the volume transition temperature (LCST) of the hydrogel. This is because increasing the concentration of the hydrophilic AM copolymer in the hydrogel reduces the hydrophobic hydration of NIPAm and increases the hydrophilic hydration, which in turn shifts the transition temperature to a higher temperature. The transition temperatures of the hydrogels prepared in Example 2 and Examples 6-8 are 31.31°C, 36.01°C, 38.06°C, and 42.37°C, respectively.

[0063] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a composite hydrogel material containing carbon quantum dots, characterized in that: The following steps are involved: (1) N-isopropylacrylamide, acrylamide, and N-N'-methylenebisacrylamide are mixed, and ascorbic acid is added. The obtained mixture 1 is dissolved in water, and ultrasonic treatment is performed to obtain a mixture 2; (2) adding hydrogen peroxide to the mixture 2 at a temperature below 5° C., refrigerating, and then heat-treating to obtain the composite hydrogel material containing carbon quantum dots; The mass ratio of N-isopropylacrylamide, acrylamide, N-N'-methylenebisacrylamide and ascorbic acid is 0.30-0.50:0-0.03:0.01:0.02-0.08, and the mass of acrylamide is not 0; The molar ratio of the hydrogen peroxide to ascorbic acid is 1:1; In step (2), the refrigeration temperature is 0-5°C and the time is 12-24 hours; the heat treatment temperature is 85-90°C and the time is 2-3 hours.

2. The preparation method according to claim 1, characterized in that In step (1), the ratio of water to N-isopropylacrylamide, acrylamide and N-N'-methylenebisacrylamide is: 3.52mL-3.88mL:0.30-0.50g:0-0.03g:0.01g, and the mass of acrylamide is not 0.

3. A composite hydrogel material containing carbon quantum dots obtained by the preparation method according to any one of claims 1 to 2.

4. The composite hydrogel material containing carbon quantum dots as claimed in claim 3 is in Fe 3+ Application in detection.

5. A method for detecting Fe 3+ The fluorescence sensor is characterized in that A composite hydrogel material comprising the carbon quantum dots according to claim 3.

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