A modified cellulose / acrylic acid composite fluorescent hydrogel and its preparation method and application

Abstract

The invention discloses a modified cellulose / acrylic acid composite fluorescent hydrogel and its preparation method and application, which belongs to the technical field of modified biomass functional polymer materials. The method is to use microcrystalline cellulose as raw material, add dialdehyde cellulose anthrone ethylenediamine fluorescent material to the raw material, use N, N-methylenebisacrylamide and acrylic acid as cross-linking agents, and use sodium persulfate as initiator to prepare modified cellulose / acrylic acid composite fluorescent hydrogel through physical and chemical cross-linking. The prepared hydrogel has obvious three-dimensional structure, which can effectively improve the shortcomings of existing cellulose-based hydrogels such as low mechanical strength, poor toughness, weak interaction of molecular chains in gel network, and insufficient toughness. The modified cellulose / acrylic acid composite fluorescent hydrogel of the present invention has a three-dimensional structure, good strength and toughness, has good recognition and fluorescence responsiveness to Hg(II) ions in water bodies, and when used for the detection of Hg(II) ions in water bodies, has the advantages of good recognition selectivity, low detection limit, high detection efficiency, economy and environmental protection.

Description

Technical Field

[0001] The invention belongs to the technical field of modified biomass functional polymer materials, and particularly relates to a modified cellulose / acrylic acid composite fluorescent hydrogel and a preparation method and application thereof. Background Art

[0002] In recent years, with the continued advancement of the industrial age, pollution incidents have become increasingly frequent. Wastewater generated by various industrial and domestic activities is often contaminated by a wide range of pollutants, including inorganic pollutants such as heavy metal ions, organic substances such as dyes and pharmaceuticals, biological pollutants such as bacteria, and radioactive waste such as radionuclides. These harmful substances have direct and negative impacts on both humans and the environment. Heavy metal ion pollution, in particular, can linger in the environment for extended periods, eventually entering the human body through the food chain and accumulating in large quantities, causing a variety of health risks. Therefore, eliminating heavy metal pollution has become a key concern for public health.

[0003] Therefore, it is necessary to develop methods for rapid detection and removal of heavy metal ions. Among various analytical methods, fluorescent sensors have been widely studied due to their high sensitivity and simple instrumentation requirements. Compared to the widely used polyvinyl alcohol electrolyte, hydrogels with three-dimensional network structures are more suitable for the preparation of sensor devices due to their high stretchability and compressibility. Fluorescent hydrogels are a new type of polymer composite material with a three-dimensional cross-linked network and fluorescence emission properties. They can change the fluorescence intensity or fluorescence emission color when stimulated by external target analytes. Therefore, fluorescent hydrogels can serve as an important tool for quantitative detection of target analyte concentrations and exhibit good fluorescence stability and detection portability. In recent years, researchers have developed a variety of fluorescent hydrogel sensing probes based on different types of response mechanisms and applied them to the detection of various types of target analytes. Li et al. constructed a fluorescent cellulose hydrogel with 0D thiol carbon dots. The cellulose-based hydrogel was prepared by self-assembly of 0D thiol carbon dots and cellulose hydrogel. The detection limit of Hg(II) in the range of 0–40 μM was 3 μmol / s. (Li M, Yang M, Liu B, et al. Self-assembling fluorescent hydrogel for highly efficient water purification and photothermal conversion[J]. Chemical Engineering Journal, 2022, 431: 134245). In particular, fluorescent hydrogels based on biomass materials have been reported as metal ion sensors due to their excellent biocompatibility, degradability and adaptability. Cellulose-based fluorescent hydrogel materials have significantly enhanced the toughness of the resulting hydrogel due to their supramolecular network, with the toughness increased by more than dozens of times. In addition, it exhibits enhanced properties in terms of stretchability, modulus, self-stiffness and elasticity. Therefore, the excellent mechanical properties and sensing properties of cellulose-based functional fluorescent hydrogel materials have been widely studied and utilized. Another problem with modified cellulose functional hydrogel probes is their low strength and poor toughness, which affects their practical application. For example, someone used 4-formylphenylboronic acid to crosslink polyvinyl alcohol and polyethyleneimine to construct a dual dynamic crosslinked hydrogel network based on borate ester bonds and imine bonds. The introduction of polypyrrole-modified cellulose nanofibers resulted in a nanocomposite hydrogel with good self-healing and electrical conductivity. The maximum tensile strength was 6.65 kPa and the maximum elongation was 350%. (Qiu Yijuan, Lin Jiawei, Qin Jirui, et al. Dual dynamic covalent crosslinked nanocellulose conductive hydrogel and its flexible sensor [J]. Chemical Industry Progress, 2022(8):041.)

[0004] Currently available biomass cellulose-based fluorescent hydrogel materials for heavy metal ion detection suffer from low mechanical strength, poor toughness, weak molecular chain interactions within the gel network, low ion detection efficiency, poor selectivity, and high detection limits, hindering their practical application. Therefore, there is an urgent need to develop biomass hydrogel fluorescent detection materials with high mechanical strength, good toughness, strong intermolecular interactions between gel network stabilizers, high detection efficiency, good selectivity, and low detection limits. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a modified cellulose / acrylic acid composite fluorescent hydrogel and its preparation method and application, so as to solve the shortcomings of cellulose-based hydrogels such as poor mechanical properties, weak molecular chain interactions in the gel network, and insufficient toughness, which lead to low metal ion detection efficiency, poor selectivity and high detection limit.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel, comprising the following steps:

[0008] 1) After stirring anthrone ethylenediamine, dialdehyde cellulose, and methanol at 50-70°C for 5-7 hours, ethanol was added and filtered to obtain dialdehyde cellulose anthrone ethylenediamine fluorescent material;

[0009] 2) The dialdehyde cellulose anthrone ethylenediamine fluorescent material prepared in step 1) is added to microcrystalline cellulose, and then a zinc chloride solution is added. After stirring until clear, N,N-methylenebisacrylamide and ammonium persulfate are added to continue the reaction. Then, acrylic acid is added and stirred evenly. After ultraviolet irradiation, a modified cellulose / acrylic acid composite fluorescent hydrogel is obtained.

[0010] Optimally, in step 2), the mass ratio of dialdehyde cellulose anthrone ethylenediamine fluorescent material: microcrystalline cellulose: zinc chloride solution: N,N-methylenebisacrylamide: ammonium persulfate: acrylic acid is (0.02~0.05): (0.15~0.18): (18~22): (0.02~0.06): (0.06~0.08): (1.5~3); the mass fraction of the zinc chloride solution is 68%.

[0011] Optimally, in step 2), the ultraviolet irradiation time is 8 to 10 minutes.

[0012] Optimally, in step 1), the mass ratio of anthrone ethylenediamine: dialdehyde cellulose: methanol: ethanol is (0.05~0.15): (0.2~0.6): (20~30): (20~30).

[0013] Optimally, in step 1), the molecular weight of the dialdehyde cellulose is 40,000-100,000.

[0014] Optimally, in step 1), the molecular weight of the dialdehyde cellulose anthrone ethylenediamine fluorescent material is 40230-100240.

[0015] Optimally, in step 1),

[0016] The preparation method of the anthrone ethylenediamine comprises the following steps: adding anthrone to a toluene solvent, then adding an ethylenediamine solution, reacting evenly, vacuum filtering, and vacuum drying to obtain anthrone ethylenediamine;

[0017] The mass ratio of the anthrone: toluene solvent: ethylenediamine solution is (0.5-1.5): (40-60): (0.3-0.7);

[0018] The mass fraction of the toluene is 99.5%, and the mass fraction of ethylenediamine is 99.5%.

[0019] Optimally, in step 1),

[0020] The preparation method of dialdehyde cellulose comprises: adding sodium periodate into water and stirring to form a suspension, then adding microcrystalline cellulose, continuing to stir in the dark, adding ethylene glycol and continuing to stir, and filtering with water and ethanol to obtain dialdehyde cellulose;

[0021] The mass ratio of sodium periodate: water: microcrystalline cellulose: ethylene glycol is (3-5): (75-85): (1-5): (3-5);

[0022] The mass fraction of the ethylene glycol is 99.5%.

[0023] The present invention also discloses a modified cellulose / acrylic acid composite fluorescent hydrogel prepared by the above preparation method. The modified cellulose / acrylic acid composite fluorescent hydrogel has a maximum tensile strength of 130-150 KPa and a maximum elongation of 680%-730%.

[0024] The present invention also discloses the application of the modified cellulose / acrylic acid composite fluorescent hydrogel in the detection of heavy metal ions. The modified cellulose / acrylic acid composite fluorescent hydrogel has recognition and fluorescence responsiveness to Hg(II) in water, linear quenching in the concentration range of 0-400 μmol / L, and can complete detection in 1-2 minutes, with a detection limit of 0.02-0.03 μmol / L.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel. The method involves reacting dialdehyde cellulose with the fluorescent small molecule anthrone ethylenediamine to produce a dialdehyde cellulose anthrone ethylenediamine fluorescent material with a linear macromolecular structure. Within the dialdehyde cellulose anthrone ethylenediamine fluorescent material system, microcrystalline cellulose, acrylic acid, and N,N-methylenebisacrylamide are polymerized and cross-linked under the action of ammonium persulfate to construct a hydrogel system with a three-dimensional cross-linked network structure. The modified cellulose / acrylic acid composite fluorescent hydrogel is then prepared through physical and chemical cross-linking with the dialdehyde cellulose anthrone ethylenediamine fluorescent material. The prepared modified cellulose / acrylic acid composite fluorescent hydrogel exhibits a distinct three-dimensional structure and significantly improves its strength and toughness, with a maximum tensile strength of 130-150 kPa and a maximum elongation of 680%-730%. The chemical reactions involved in the preparation process, the method for obtaining the modified cellulose / acrylic acid composite hydrogel, and its chemical structure are novel, creative, and practical.

[0027] The present invention also discloses a modified cellulose / acrylic acid composite fluorescent hydrogel prepared by the above-mentioned preparation method. The hydrogel has a distinct three-dimensional structure, high strength, and good toughness, with a maximum tensile strength of 130-150 kPa and a maximum elongation of 680%-730%. Furthermore, the hydrogel has excellent recognition and fluorescence responsiveness to Hg(II) in water, exhibiting a significant quenching effect and good selectivity when used for Hg(II) detection in water. Therefore, the hydrogel can be used for Hg(II) detection in water, with advantages such as high efficiency, high sensitivity, and low cost.

[0028] The present invention also discloses the application of the modified cellulose / acrylic acid composite fluorescent hydrogel in the detection of heavy metal ions. The modified cellulose / acrylic acid composite fluorescent hydrogel has high selectivity for Hg(II) in water, and has the best detection performance for Hg(II), with significant improvements in detection limit, quenching concentration range, and detection time. It linearly quenches Hg(II) in the range of 0-400 μmol / L, can complete detection in 1-2 minutes, and has a detection limit of 0.02-0.03 μmol / L. At the same time, the detection cost is about 5 yuan per sample, and the application has low economic cost and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The diagrams for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel disclosed in the present invention are as follows; (a) is a schematic diagram of the chemical reaction for preparing the dialdehyde cellulose anthrone ethylenediamine fluorescent material and its chemical structure; (b) is a schematic diagram of the preparation process and chemical structure of the modified cellulose / acrylic acid composite fluorescent hydrogel;

[0030] Figure 2This is a comparison of infrared spectra of the modified cellulose / acrylic acid composite fluorescent hydrogel and microcrystalline cellulose prepared in Example 1 of the present invention;

[0031] Figure 3 This is a graph showing the fluorescence response of the modified cellulose / acrylic acid composite fluorescent hydrogel prepared in Example 1 of the present invention to different metal ions. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] The present invention is further described in detail below with reference to specific embodiments and accompanying drawings:

[0035] The invention discloses a preparation method of a modified cellulose / acrylic acid composite fluorescent hydrogel. Microcrystalline cellulose is used as a raw material, dialdehyde cellulose anthrone ethylenediamine fluorescent material is added to the raw material, N,N-methylenebisacrylamide and acrylic acid are used as cross-linking agents, sodium persulfate is used as an initiator, and the modified cellulose / acrylic acid composite fluorescent hydrogel is prepared through physical cross-linking and chemical cross-linking.

[0036] The specific steps include:

[0037] 1) By weight, 0.5-1.5 parts of anthrone were added to 40-60 parts of toluene solvent, and 0.3-0.7 parts of ethylenediamine solution was slowly added dropwise. The mixture was stirred at 100-120°C for 7-9 hours. The mixture was vacuum filtered and then vacuum dried for 5-7 hours to prepare anthrone ethylenediamine. 3-5 parts of sodium periodate were added to 75-85 parts of water and stirred to obtain a suspension. 1-5 parts of microcrystalline cellulose were added to the suspension and stirred in the dark for 7-9 hours. 3-5 parts of ethylene glycol were added dropwise and stirred for 1-2 hours. The mixture was filtered with 20-30 parts of water and 20-30 parts of ethanol to obtain dialdehyde cellulose. 0.05-0.15 parts of anthrone ethylenediamine and 0.2-0.6 parts of dialdehyde cellulose were added dropwise to 20-30 parts of methanol and stirred at 50-70°C for 5-7 hours. hours, adding 20 to 30 parts of ethanol and filtering to obtain a dialdehyde cellulose anthrone ethylenediamine fluorescent material;

[0038] 2) To 0.15-0.18 parts of microcrystalline cellulose, 0.02-0.05 parts of dialdehyde cellulose anthrone ethylenediamine fluorescent material were added, followed by the addition of 18-22 parts of zinc chloride solution. After stirring to clarify, 0.02-0.06 parts of N,N-methylenebisacrylamide and 0.06-0.08 parts of ammonium persulfate were added to continue the reaction. 1.5-3 parts of acrylic acid were added, stirring was continued for 2-4 minutes, and the mixture was irradiated under ultraviolet light for 8-10 minutes to obtain a modified cellulose / acrylic acid composite fluorescent hydrogel.

[0039] The mass fraction of the toluene is 99.5%, the mass fraction of ethylenediamine is 99.5%, and the mass fraction of ethylene glycol is 99.5%.

[0040] The molecular weight of the dialdehyde cellulose is 40,000-100,000, and the molecular weight of the dialdehyde cellulose anthrone ethylenediamine fluorescent material is 40,230-100,240.

[0041] The mass fraction of the zinc chloride solution is 68%.

[0042] The modified cellulose / acrylic acid composite fluorescent hydrogel has a maximum tensile strength of 130-150 kPa and a maximum elongation of 680%-730%. Its notable application performance and characteristic is its ability to adsorb Hg(II). The hydrogel's ability to detect metal ions was tested. The hydrogel membrane linearly quenches Hg(II) in water over a concentration range of 0-400 μmol / L, enabling detection within 1-2 minutes with a detection limit of 0.02-0.03 μmol / L. The detection results of the patented detection method of the present invention are far lower than the national Hg(II) content standard of 0.5 μmol / L in food and the Hg(II) content standard of 0.25 μmol / L in tap water, as specified in the "Industrial Water Hygiene Standard GB2762-2012."

[0043] Example 1

[0044] A method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel specifically comprises the following steps:

[0045] 1) By weight, 0.5 parts of anthrone were added to 40 parts of toluene solvent, and 0.3 parts of ethylenediamine solution was slowly added dropwise. The mixture was stirred at 110°C for 8 hours, filtered, and then vacuum-dried for 6 hours to prepare anthrone ethylenediamine. 3 parts of sodium periodate were added to 75 parts of water and stirred to obtain a suspension. 1 part of microcrystalline cellulose was added to the suspension and stirred in the dark for 8 hours. 3 parts of ethylene glycol was added dropwise and stirred for 1 hour. The mixture was filtered with 20 parts of water and 20 parts of ethanol to obtain dialdehyde cellulose. 0.05 parts of anthrone ethylenediamine and 0.2 parts of dialdehyde cellulose were added dropwise with 20 parts of methanol, stirred at 60°C for 6 hours, and filtered with 20 parts of ethanol to obtain a dialdehyde cellulose anthrone ethylenediamine fluorescent material.

[0046] 2) To 0.15 parts of microcrystalline cellulose, 0.02 parts of dialdehyde cellulose anthrone ethylenediamine fluorescent material was added, and 20 parts of zinc chloride solution was added for reaction. After stirring to clarify, 0.04 parts of N,N-methylenebisacrylamide and 0.08 parts of ammonium persulfate were added to continue the reaction. 2.5 parts of acrylic acid was added and stirring was continued for 2 minutes. The mixture was irradiated under ultraviolet light for 10 minutes to obtain a modified cellulose / acrylic acid composite fluorescent hydrogel.

[0047] See also Figure 1 This is a diagram for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel disclosed in the present invention; wherein, (a) is a schematic diagram of the chemical reaction for preparing the dialdehyde cellulose anthrone ethylenediamine fluorescent material and its chemical structure; as can be seen from the figure, microcrystalline cellulose generates dialdehyde cellulose under the action of sodium periodate, and dialdehyde cellulose then reacts with anthrone ethylenediamine to generate the dialdehyde cellulose anthrone ethylenediamine fluorescent material; (b) is a schematic diagram of the preparation process of the modified cellulose / acrylic acid composite fluorescent hydrogel and its chemical structure; as can be seen from the figure, dialdehyde cellulose anthrone ethylenediamine then reacts with microcrystalline cellulose under the action of acrylic acid, N,N-methylenebisacrylamide and ammonium persulfate to generate a modified cellulose / acrylic acid composite fluorescent hydrogel fluorescent material with an interpenetrating cross-linked network structure.

[0048] See also Figure 2 The infrared spectra of the modified cellulose / acrylic acid composite fluorescent hydrogel and microcrystalline cellulose prepared in Example 1 are compared. As can be seen from the figure, the modified cellulose / acrylic acid composite fluorescent hydrogel has a peak at 3412 cm -1 There is an obvious characteristic absorption peak of -OH of microcrystalline cellulose at 1612 cm -1There is also a characteristic absorption peak of C=O of acrylic acid, indicating the successful cross-linking of microcrystalline cellulose and acrylic acid in the hydrogel.

[0049] See also Figure 3 This is a fluorescence response diagram of the modified cellulose / acrylic acid composite fluorescent hydrogel prepared in Example 1 of the present invention to different metal ions. It can be seen from the figure that the modified cellulose / acrylic acid composite fluorescent hydrogel has a more obvious fluorescence response to Hg(II).

[0050] The modified cellulose / acrylic acid composite fluorescent hydrogel prepared using the above method exhibited a maximum tensile strength of 130 kPa and a maximum elongation of 680%. Its remarkable application performance and characteristic is its ability to adsorb Hg(II) in water. The hydrogel membrane linearly quenched Hg(II) over a concentration range of 0 to 300 μmol / L, enabling detection within one minute with a detection limit of 0.02 μmol / L.

[0051] Example 2

[0052] A method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel specifically comprises the following steps:

[0053] 1) By weight, 1 part of anthrone was added to 50 parts of toluene solvent, and 0.5 parts of ethylenediamine solution was slowly added dropwise, and the mixture was stirred at 110°C for 8 hours; the mixture was filtered and then vacuum-dried for 6 hours to prepare anthrone ethylenediamine; 4 parts of sodium periodate was added to 80 parts of water and stirred to obtain a suspension; 2 parts of microcrystalline cellulose was added to the suspension and stirred in the dark for 8 hours, 4 parts of ethylene glycol was added dropwise and stirred for 1 hour, and the mixture was filtered with 20 parts of water and 20 parts of ethanol to obtain dialdehyde cellulose; 30 parts of methanol were added dropwise to 0.1 parts of anthrone ethylenediamine and 0.5 parts of dialdehyde cellulose, and the mixture was stirred at 60°C for 6 hours. 20 parts of ethanol was added and filtered to obtain a dialdehyde cellulose anthrone ethylenediamine fluorescent material;

[0054] 2) To 0.18 parts of microcrystalline cellulose, 0.05 parts of dialdehyde cellulose anthrone ethylenediamine fluorescent material was added, and 20 parts of zinc chloride solution was added for reaction. After stirring to clarify, 0.04 parts of N,N-methylenebisacrylamide and 0.08 parts of ammonium persulfate were added to continue the reaction. 2.5 parts of acrylic acid was added and stirring was continued for 4 minutes. The mixture was irradiated under ultraviolet light for 10 minutes to obtain a modified cellulose / acrylic acid composite fluorescent hydrogel.

[0055] The modified cellulose / acrylic acid composite fluorescent hydrogel prepared according to the above preparation method has a maximum tensile strength of 150 kPa and a maximum elongation of 730%. This hydrogel can be used to detect Hg(II) in water. It linearly quenches Hg(II) in the concentration range of 0-100 μmol / L and can complete detection within 2 minutes with a detection limit of 0.025 μmol / L.

[0056] Example 3

[0057] A method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel specifically comprises the following steps:

[0058] 1) By weight, 1.5 parts of anthrone were added to 60 parts of toluene solvent, and 0.7 parts of ethylenediamine solution was slowly added dropwise. The mixture was stirred at 110°C for 8 hours, filtered, and then vacuum-dried for 6 hours to prepare anthrone ethylenediamine. 5 parts of sodium periodate were added to 80 parts of water and stirred to obtain a suspension. 5 parts of microcrystalline cellulose were added to the suspension and stirred in the dark for 8 hours. 5 parts of ethylene glycol were added dropwise and stirred for 1 hour. The mixture was filtered with 20 parts of water and 20 parts of ethanol to obtain dialdehyde cellulose. 0.15 parts of anthrone ethylenediamine and 0.6 parts of dialdehyde cellulose were added dropwise with 25 parts of methanol, stirred at 60°C for 6 hours, and filtered with 20 parts of ethanol to obtain a dialdehyde cellulose anthrone ethylenediamine fluorescent material.

[0059] 2) To 0.17 parts of microcrystalline cellulose, 0.03 parts of dialdehyde cellulose anthrone ethylenediamine fluorescent material was added, and 20 parts of zinc chloride solution was added for reaction. After stirring to clarify, 0.04 parts of N,N-methylenebisacrylamide and 0.08 parts of ammonium persulfate were added to continue the reaction. 2.5 parts of acrylic acid was added and stirring was continued for 3 minutes. The mixture was irradiated under ultraviolet light for 10 minutes to obtain a modified cellulose / acrylic acid composite fluorescent hydrogel.

[0060] The modified cellulose / acrylic acid composite fluorescent hydrogel prepared according to the above preparation method has a maximum tensile strength of 145 kPa and a maximum elongation of 696%. This hydrogel can be used to detect Hg(II) in water. It linearly quenches Hg(II) in the concentration range of 0-200 μmol / L and can complete detection in 1.5 minutes with a detection limit of 0.03 μmol / L.

[0061] Example 4

[0062] A method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel specifically comprises the following steps:

[0063] 1) By weight, 1 part anthrone was added to 50 parts toluene solvent, and 0.5 parts of ethylenediamine solution was slowly added dropwise. The mixture was stirred at 110°C for 8 hours, filtered, and then vacuum-dried for 6 hours to prepare anthrone ethylenediamine. 4 parts of sodium periodate was added to 80 parts of water and stirred to obtain a suspension. 2 parts of microcrystalline cellulose was added to the suspension and stirred in the dark for 8 hours. 4 parts of ethylene glycol was added dropwise and stirred for 1 hour. The suspension was filtered with 20 parts of water and 20 parts of ethanol to obtain dialdehyde cellulose. 26 parts of methanol were added dropwise to 0.1 parts of anthrone ethylenediamine and 0.5 parts of dialdehyde cellulose. The mixture was stirred at 60°C for 6 hours, and 20 parts of ethanol was added and filtered to obtain a dialdehyde cellulose anthrone ethylenediamine fluorescent material.

[0064] 2) To 0.16 parts of microcrystalline cellulose, 0.04 parts of dialdehyde cellulose anthrone ethylenediamine fluorescent material was added, and 20 parts of zinc chloride solution was added for reaction. After stirring to clarify, 0.04 parts of N,N-methylenebisacrylamide and 0.08 parts of ammonium persulfate were added to continue the reaction. 2.5 parts of acrylic acid was added and stirring was continued for 4 minutes. The mixture was irradiated under ultraviolet light for 10 minutes to obtain a modified cellulose / acrylic acid composite fluorescent hydrogel.

[0065] The modified cellulose / acrylic acid composite fluorescent hydrogel prepared according to the above preparation method has a maximum tensile strength of 140 kPa and a maximum elongation of 710%. This hydrogel can be used to detect Hg(II) in water. It linearly quenches Hg(II) in the concentration range of 0-300 μmol / L and can complete detection in 1.5 minutes with a detection limit of 0.023 μmol / L.

[0066] Example 5

[0067] A method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel specifically comprises the following steps:

[0068] 1) By weight, 1 part of anthrone was added to 50 parts of toluene solvent, and 0.5 parts of ethylenediamine solution was slowly added dropwise, and the mixture was stirred at 110°C for 8 hours; the mixture was filtered and then vacuum-dried for 6 hours to prepare anthrone ethylenediamine; 4 parts of sodium periodate was added to 80 parts of water and stirred to obtain a suspension; 2 parts of microcrystalline cellulose was added to the suspension and stirred in the dark for 8 hours, 4 parts of ethylene glycol was added dropwise and stirred for 1 hour, and the mixture was filtered with 20 parts of water and 20 parts of ethanol to obtain dialdehyde cellulose; 0.1 parts of anthrone ethylenediamine and 0.5 parts of dialdehyde cellulose were added dropwise with 28 parts of methanol, and the mixture was stirred at 60°C for 6 hours. 20 parts of ethanol was added and filtered to obtain a dialdehyde cellulose anthrone ethylenediamine fluorescent material;

[0069] 2) To 0.04 parts of microcrystalline cellulose, 0.05 parts of dialdehyde cellulose anthrone ethylenediamine fluorescent material was added, and 20 parts of zinc chloride solution was added for reaction. After stirring to clarify, 0.04 parts of N,N-methylenebisacrylamide and 0.08 parts of ammonium persulfate were added to continue the reaction. 2.5 parts of acrylic acid was added and stirring was continued for 3 minutes. The mixture was irradiated under ultraviolet light for 10 minutes to obtain a modified cellulose / acrylic acid composite fluorescent hydrogel.

[0070] The modified cellulose / acrylic acid composite fluorescent hydrogel prepared according to the above preparation method has a maximum tensile strength of 135 kPa and a maximum elongation of 705%. This hydrogel can be used to detect Hg(II) in water. It linearly quenches Hg(II) in the concentration range of 0-400 μmol / L and can complete detection within 2 minutes with a detection limit of 0.03 μmol / L.

[0071] The present invention uses microcrystalline cellulose as raw material, N, N-methylenebisacrylamide and acrylic acid as crosslinking agents, and ammonium persulfate as initiator to introduce dialdehyde cellulose / anthrone ethylenediamine fluorescent groups to prepare modified cellulose / acrylic acid composite fluorescent hydrogel, which effectively improves the shortcomings of existing cellulose-based hydrogels, such as poor mechanical strength, weak molecular chain interaction in the gel network, and insufficient toughness. In addition, the material is resistant to Hg 2+ It has an ideal fluorescence response, obvious quenching effect and selectivity, and can be used for the detection of Hg(II) in water.

[0072] Control Example

[0073] By weight, 20 parts of zinc chloride solution were added to 0.15 parts of microcrystalline cellulose for reaction. After stirring to clarify, 0.04 parts of N,N-methylenebisacrylamide and 0.08 parts of ammonium persulfate were added to continue the reaction. Then, 2.5 parts of acrylic acid were added and stirring was continued for 10 minutes. The mixture was irradiated under ultraviolet light for 10 minutes to obtain a cellulose / acrylic acid composite hydrogel.

[0074] The cellulose / acrylic acid composite hydrogel prepared according to the above preparation method can detect Hg(II) within 5-10 minutes, linearly quenches Hg(II) in the concentration range of 300-400 μmol / L, and has a detection limit of 50 μmol / L.

[0075] The detection results of the patented detection method of this invention are far lower than the national standard of Hg(II) content in food of 0.5 μmol / L and the Hg(II) content standard of 0.25 μmol / L in the national standards of the People's Republic of China GB4754-84 and GB2762-2012 for tap water.

[0076] Table 1 Detection application of modified cellulose / acrylic acid composite fluorescent hydrogels prepared in Examples 1 to 5 for Hg(II)

[0077]

[0078] Table 2 Mechanical properties and toughness of modified cellulose / acrylic acid composite fluorescent hydrogels prepared in Examples 1 to 5

[0079]

[0080] Table 1 shows the application of modified cellulose / acrylic acid composite fluorescent hydrogels prepared in Examples 1-5 of the present invention for Hg(II) detection. The test results in the table demonstrate that the modified cellulose / acrylic acid composite fluorescent hydrogels prepared in the present invention significantly improve the detection limit, quenching range, and detection time for Hg(II) in solution. Furthermore, the detection cost is approximately one-third of that of the national standard method, demonstrating its novelty, creativity, and practicality.

[0081] Table 2 shows the maximum tensile strength and maximum elongation of the modified cellulose / acrylic acid composite fluorescent hydrogels prepared in Examples 1-5 of the present invention. The test results in the table demonstrate that the modified cellulose / acrylic acid composite fluorescent hydrogels disclosed herein exhibit high strength and good toughness. Mechanical testing of the hydrogels was performed using a universal mechanical testing machine in accordance with the national standard method GB / T528-1998.

[0082] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a modified cellulose / acrylic acid composite fluorescent hydrogel, characterized in that: The following steps are involved: 1) After stirring anthrone ethylenediamine, dialdehyde cellulose, and methanol at 50-70°C for 5-7 hours, ethanol was added and filtered to obtain dialdehyde cellulose anthrone ethylenediamine fluorescent material; 2) The dialdehyde cellulose anthrone ethylenediamine fluorescent material prepared in step 1) is added to microcrystalline cellulose, and then a zinc chloride solution is added. After stirring until clear, N,N-methylenebisacrylamide and ammonium persulfate are added to continue the reaction. Then, acrylic acid is added and stirred evenly. After ultraviolet irradiation, a modified cellulose / acrylic acid composite fluorescent hydrogel is obtained.

2. The method for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 1, characterized in that: In step 2), the mass ratio of dialdehyde cellulose anthrone ethylenediamine fluorescent material: microcrystalline cellulose: zinc chloride solution: N,N-methylenebisacrylamide: ammonium persulfate: acrylic acid is (0.02~0.05): (0.15~0.18): (18~22): (0.02~0.06): (0.06~0.08): (1.5~3); the mass fraction of the zinc chloride solution is 68%.

3. The method for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 1, characterized in that: In step 2), the ultraviolet irradiation time is 8 to 10 minutes.

4. The method for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 1, characterized in that: In step 1), the mass ratio of anthrone ethylenediamine: dialdehyde cellulose: methanol: ethanol is (0.05-0.15): (0.2-0.6): (20-30): (20-30).

5. The method for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 1, characterized in that: In step 1), the molecular weight of the dialdehyde cellulose is 40,000-100,000.

6. The method for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 1, characterized in that: In step 1), the molecular weight of the dialdehyde cellulose anthrone ethylenediamine fluorescent material is 40230-100240.

7. The method for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 1, characterized in that: In step 1), The preparation method of the anthrone ethylenediamine comprises the following steps: adding anthrone to a toluene solvent, then adding an ethylenediamine solution, reacting evenly, vacuum filtering, and vacuum drying to obtain anthrone ethylenediamine; The mass ratio of the anthrone: toluene solvent: ethylenediamine solution is (0.5-1.5): (40-60): (0.3-0.7); The mass fraction of the toluene is 99.5%, and the mass fraction of ethylenediamine is 99.5%.

8. The method for preparing the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 1, characterized in that: In step 1), The preparation method of dialdehyde cellulose comprises: adding sodium periodate into water and stirring to form a suspension, then adding microcrystalline cellulose, continuing to stir in the dark, adding ethylene glycol and continuing to stir, and filtering with water and ethanol to obtain dialdehyde cellulose; The mass ratio of sodium periodate: water: microcrystalline cellulose: ethylene glycol is (3-5): (75-85): (1-5): (3-5); The mass fraction of the ethylene glycol is 99.5%.

9. The modified cellulose / acrylic acid composite fluorescent hydrogel prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The maximum tensile strength is 130~150 KPa, and the maximum elongation is 680%~730%.

10. Use of the modified cellulose / acrylic acid composite fluorescent hydrogel according to claim 9 in detecting heavy metal ions, characterized in that: The modified cellulose / acrylic acid composite fluorescent hydrogel has recognition and fluorescence responsiveness to Hg(II) in water, with linear quenching in the concentration range of 0-400 μmol / L, and can complete detection within 1-2 minutes, with a detection limit of 0.02-0.03 μmol / L.

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