Preparation method and application of EuFeO3 / g-C3N4 composite material

Abstract

The invention belongs to the technical field of inorganic material synthesis, and particularly relates to a preparation method and application of an EuFeO3 / g-C3N4 composite material. According to the composite material, g-C3N4 is prepared through a urea solid-phase calcination method, Eu (NO3) 3.5 H2O, Fe (NO3) 3.9 H2O and anhydrous citric acid are subjected to ultrasonic dispersion and then heated, refluxed and further calcined to prepare dark red EuFeO3 powder, and finally, g-C3N4 and EuFeO3 solids are prepared into a target product through a solid-phase calcination method. According to the composite material, graphite phase carbon nitride is used as a substrate material, perovskite type rare earth composite oxide EuFeO3 with 4f active electrons and good photoelectric characteristics is loaded to enhance the conductivity and the enrichment rate of a single g-C3N4 material, and the area of an active center region is adjusted; the EuFeO3 / g-C3N4 composite material with obviously enhanced electrogenerated chemiluminescence signals is prepared, a sensor probe is constructed, the effect of high-sensitivity and specific recognition of Cd < 2 + > is successfully achieved, the response stability and reproducibility are good, and the EuFeO3 / g-C3N4 composite material can be used for trace detection of Cd < 2 + > and is an electrogenerated chemiluminescence sensing material with potential application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic material synthesis, and in particular relates to a preparation method and application of a EuFeO3 / g-C3N4 composite material. Background Art

[0002] Cadmium ions (Cd 2+ ) is one of the heavy metal ions widely used in the military and metallurgical industries. It can cause irreversible environmental pollution and accumulation in the food chain, thus causing serious damage to the kidneys, bones, and cardiovascular system, and even lead to developmental deformities and cancer. The U.S. Agency for Toxic Substances and Disease Registry and the Environmental Protection Agency (EPA) have listed Cd as 2+ It is identified as a highly toxic heavy metal and Cd in drinking water is 2+ The concentration limit standard is set at 5 ppb, so there is an urgent need to develop a highly sensitive, low-cost, rapid and reliable method to quantitatively detect Cd in complex environmental samples. 2+ concentration.

[0003] Currently available methods include spectrophotometry, electrochemistry, atomic absorption spectroscopy (AAS), etc. Among them, spectrophotometry is simple to operate and widely used, but it has great limitations in terms of sensitivity and selectivity. Although electrochemical methods and atomic absorption spectroscopy have high sensitivity and selectivity, the expensive and complex instruments and the need for skilled operators have become bottlenecks that limit their large-scale application in routine detection. In recent years, electrochemiluminescence (ECL), a process related to the transfer of high-energy electrons on the electrode to produce excited state luminescence, which combines the advantages of electrochemistry and spectroscopy, has been widely used in fields including clinical diagnosis, environmental monitoring and food safety testing due to its advantages such as rapid analysis, low detection limit and wide dynamic range.

[0004] Graphitic carbon nitride (g-C3N4) has been highly favored in ECL research due to its non-toxicity, ease of synthesis, low cost, and good biocompatibility. However, due to its poor conductivity, charge accumulation, and electrode passivation, the ECL signal intensity of g-C3N4 is often unstable. To address this issue, strategies such as element doping, morphology control, and heterojunction construction have been used to improve and optimize the performance of g-C3N4, attracting the attention of researchers in the ECL field. Rare earth materials, especially lanthanide iron oxide (ReFeO3) perovskites with unique electrical, catalytic, and crystal defect properties, have developed into one of the most promising functional luminescent materials due to their excellent luminescence properties brought about by the inherent 4f-4f transition and rich and diverse stepped electronic energy levels, such as ultra-high luminescence efficiency, long lifetime, and inherently narrow emission peaks. They are widely used in catalysts, capacitors, sensors, and other fields.

[0005] In view of this, the inventors hope to provide a preparation method and application of EuFeO3 / g-C3N4 composite material. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of complex synthesis process, high energy consumption, long time consumption, low sensing sensitivity and selectivity, inability to quantitatively detect and poor stability of probe materials in traditional technologies. A preparation method and application of EuFeO3 / g-C3N4 composite material are provided. Through a simple reaction process and mild reaction conditions, with water as the main green and pollution-free reaction solvent and test solvent, the perovskite-type rare earth composite oxide EuFeO3 with 4f active electrons and excellent photoelectric properties is used to enhance the conductivity and enrichment rate of a single g-C3N4 material, and the area of its active center is adjusted to prepare a EuFeO3 / g-C3N4 composite material with significantly enhanced electrochemiluminescence signal and construct a sensor probe, which successfully achieves high sensitivity and specific recognition of Cd 2+ The response stability and reproducibility are good, and it can be used for trace detection of Cd 2+ , is an electrochemiluminescent sensing material with potential application value.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] The present invention provides a method for preparing a EuFeO3 / g-C3N4 composite material, comprising the following steps:

[0009] 1) Weigh 8-12 mg of urea into a porcelain crucible, cover it with tin foil, and calcine it in a muffle furnace. After cooling naturally to room temperature, remove the light yellow solid and grind it in an agate mortar to obtain g-C3N4 powder;

[0010] 2) A certain amount of Eu(NO3)3·5H2O and Fe(NO3)3·9H2O were weighed and dissolved in deionized water. An equal amount of anhydrous citric acid was added to the Eu(NO3)3·5H2O, and the mixed solution in the round-bottom flask was ultrasonically dispersed. The mixture was then transferred to an oil bath and heated with stirring. After the solvent was completely evaporated, the obtained solid product was calcined in a muffle furnace. After cooling to room temperature, the agate powder was washed with water and ethanol, respectively, and centrifuged. Finally, it was dried in a vacuum drying oven to obtain a dark red EuFeO3 powder.

[0011] 3) Ultrasonic dispersion of g-C3N4 powder and EuFeO3 powder in deionized water, then transfer the flask containing the mixed solution to an oil bath for stirring and reaction, dry the reaction product in an oven, and finally calcine the crucible containing the dried product in a muffle furnace to obtain a EuFeO3 / g-C3N4 composite material.

[0012] Furthermore, in step 1), the calcination parameters of the muffle furnace are: heating to 400-600° C. at a heating rate of 4-6° C. / min, and the calcination time is controlled at 2-6 h.

[0013] Furthermore, in step 2), the molar ratio of Eu(NO3)3·5H2O to Fe(NO3)3·9H2O is 1:0.8-1.2.

[0014] Furthermore, in step 2), the temperature of the oil bath is controlled at 60-100° C., and the heating and stirring time is controlled at 8-15 h.

[0015] Furthermore, in step 2), the calcination parameters of the muffle furnace are: heating to 700-900° C. at a heating rate of 2-4° C. / min, and the calcination time is controlled at 2-6 h.

[0016] Furthermore, in step 2), the drying temperature of the vacuum drying oven is controlled at 40-60° C., and the drying time is controlled at 6-12 h.

[0017] Furthermore, in step 3), the temperature of the oil bath is controlled at 50-90° C., and the stirring reaction time is controlled at 4-8 h.

[0018] Furthermore, in step 3), the drying temperature of the oven is controlled at 70-100° C., and the drying time is controlled at 6-10 h.

[0019] Furthermore, in step 3), the calcination parameters of the muffle furnace are: heating to 300-500° C. at a heating rate of 3-5° C. / min, and the calcination time is controlled at 1-4 h.

[0020] The present invention also provides a EuFeO3 / g-C3N4 nanocomposite material for preparing heavy metal ion Cd 2+ Application of Electrochemiluminescence Sensors for Identification and Trace Detection

[0021] The working mechanism of the present invention is:

[0022] Using graphene-based carbon nitride as a substrate, which has the advantages of high efficiency, stability, wide spectral response range, low price and good biocompatibility, and a simple low-temperature liquid-phase reaction coupled with a medium- and low-temperature solid-state calcination method, the loaded material has 4f active electrons. EuFeO3 with excellent optical, electrical, magnetic and catalytic properties can inhibit the aggregation of rare earth nanomaterials themselves, and synergistically improve the conductivity of single g-C3N4 materials, promote charge transport and electron transfer, reduce the reaction energy barrier, expose more catalytic active sites, and improve the overall luminescence efficiency. This enables the electrochemiluminescence sensor constructed with EuFeO3 / g-C3N4 composite material to highly sensitively and specifically identify and detect trace amounts of heavy metal Cd 2+ .

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The preparation process of the EuFeO3 / g-C3N4 composite material of the present invention is relatively simple, the raw materials are cheap, and the amount used is small.

[0025] 2. The reaction conditions of the EuFeO3 / g-C3N4 composite material of the present invention are relatively mild, which saves energy and reduces consumption.

[0026] 3. The preparation and post-processing process of the EuFeO3 / g-C3N4 composite material of the present invention is simple and easy to separate and purify.

[0027] 4. The reaction solvent and detection solvent used in the method of the present invention are aqueous phase, which is friendly to humans and the environment.

[0028] 5. Cd constructed from EuFeO3 / g-C3N4 composite material of the present invention 2+ Electrochemiluminescence sensor for Cd 2+ The sensor has a sensitive response and good recognition selectivity; it can detect trace amounts of Cd 2+ The sensor can detect quantitatively with a wide linear detection range and low detection limit; it also has excellent reproducibility and long-term stability.

[0029] Of course, any product implementing the present invention does not necessarily need to achieve all of the above advantages at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing 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 creative work.

[0031] Figure 1 Schematic diagram of the preparation and electrochemiluminescence sensing of EuFeO3 / g-C3N4 composite material;

[0032] Figure 2 Characterization diagram of the 0.25% EuFeO3 / g-C3N4 composite material prepared in Example 3;

[0033] Among them, a is TEM image, b is HRTEM image, c is SEM image, dh is element mapping image, and i is EDS image;

[0034] Figure 3 This is the spectrum of the 0.25% EuFeO3 / g-C3N4 composite material prepared in Example 3;

[0035] Wherein, a is the XPS total spectrum, b is the fine spectrum of C1s, c is the fine spectrum of N1s, d is the fine spectrum of O1s, e is the fine spectrum of Fe 2p, and f is the fine spectrum of Eu 3d;

[0036] Figure 4 Cd 2+ The inhibition kinetic curve of the ECL system of the 0.25% EuFeO3 / g-C3N4 composite material prepared in the best embodiment 3;

[0037] Figure 5 is a comparison of different materials in PBS (0.1 M, pH = 7) solution;

[0038] Among them, a is the ECL intensity comparison, b is the cyclic voltammetry curve, c is the electrochemical impedance spectroscopy, d is the ECL signal comparison of different composite materials, and e is the ECL signal intensity comparison of the composite materials under different atmospheres;

[0039] Figure 6 The influence of different factors on ECL intensity;

[0040] Wherein, a is a buffer solution of different compositions, b is the pH of the PBS solution, c is the doping amount of EuFeO3 in the composite material prepared in Example 3; d is the modification amount of the 0.25% EuFeO3 / g-C3N4 composite material prepared in Example 3 on the electrode;

[0041] Figure 7 This is a curve diagram of the 0.25% EuFeO3 / g-C3N4 reaction system prepared in Example 3;

[0042] Where a is the Cd concentration at different 2+ Response curve, b is the logarithm of the ECL intensity change and Cd 2+ Calibration curve between natural logarithms of concentrations;

[0043] Figure 8 Schematic diagram of the response of the 0.25% EuFeO3 / g-C3N4 system prepared in Example 3;

[0044] Among them, a is the response to different ions; b is the response of 0.25% EuFeO3 / g-C3N4 ECL system to Cd 2+ Reproducibility of response. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments 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 any creative efforts shall fall within the scope of protection of the present invention.

[0046] The present invention discloses a preparation method and application of a EuFeO3 / g-C3N4 composite material, belonging to the technical field of inorganic material synthesis. The compound is first prepared by solid-phase calcination of urea to prepare g-C3N4. Simultaneously, Eu(NO3)3·5H2O, Fe(NO3)3·9H2O, and anhydrous citric acid are ultrasonically dispersed, then heated under reflux and further calcined to prepare dark red EuFeO3 powder. Finally, the synthesized g-C3N4 and varying amounts of EuFeO3 solid are heated in a low-temperature oil bath coupled with a medium-temperature solid-phase calcination method to prepare the target EuFeO3 / g-C3N4 product. This composite material synthesis method is relatively simple, features low-cost raw materials, mild conditions, requires minimal reagents, and utilizes a non-polluting aqueous solvent, making it environmentally friendly. The composite material uses graphene-like structure, non-toxic, low-cost, moderate band gap, and high physicochemical stability of graphene-phase carbon nitride as the base material, and loads perovskite-type rare earth composite oxide EuFeO3 with 4f active electrons and excellent photoelectric properties to enhance the conductivity and enrichment rate of single g-C3N4 material, adjust the area of its active center, and prepare EuFeO3 / g-C3N4 composite material with significantly enhanced electrochemiluminescence signal. The sensor probe is constructed and successfully realizes high sensitivity and specificity in recognizing Cd 2+ The response stability and reproducibility are good, and it can be used for trace detection of Cd 2+ , is an electrochemiluminescent sensing material with potential application value.

[0047] The relevant embodiments of the present invention are as follows:

[0048] The morphology of the reaction products in each example was measured using an X-ray powder diffractometer (PHI Bruker D8 ADVANCE, Germany) and a transmission electron microscope (HT-7700, Japan);

[0049] The surface elements, content and chemical valence of the composite materials were analyzed using a Japanese PHIQuantera II X-ray photoelectron spectroscopy (XPS);

[0050] An MPI-B electrochemiluminescence analysis system (Xi'an Ruimai Analytical Instrument Co., Ltd.) was used for electrochemiluminescence analysis;

[0051] AC impedance analysis was performed on a CHI660 D electrochemical workstation assembled by Shanghai Chenhua Instrument Co.;

[0052] The spectral properties of the materials were analyzed using a Hitachi U-3900 UV spectrophotometer.

[0053] 1. Preparation method of TbVO4 / g-C3N4 composite material of the present invention

[0054] Example 1

[0055] Weigh 10 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 5°C / min and heat it to 500°C for 4 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0056] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.323 g (0.8 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 35 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 0.5 h, then transferred to a 60°C oil bath and heated with stirring for 15 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 700°C at a heating rate of 2°C / min and calcined for 6 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven set at 40°C and dried for 12 h to obtain EuFeO3 dark red powder.

[0057] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 20 mL of deionized water by ultrasonication for 1 hour. The flask containing the mixed solution was then transferred to a 70°C oil bath and stirred for 6 hours. The reaction product was placed in an oven set at 90°C for 8 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 300°C at a heating rate of 3°C / min. After calcination for 4 hours, the calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0058] Example 2

[0059] Weigh 8 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 4°C / min and heat it to 400°C for 6 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0060] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.444 g (1.1 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 35 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 1.5 h, then transferred to an 80°C oil bath and heated with stirring for 12 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 800°C at a heating rate of 2.5°C / min and calcined for 4 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven and dried at 50°C for 8 h to obtain EuFeO3 dark red powder.

[0061] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 20 mL of deionized water under ultrasonication for 1 hour. The flask containing the mixed solution was then transferred to a 70°C oil bath and stirred for 6 hours. The reaction product was placed in an oven set at 90°C for 8 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 400°C at a heating rate of 4°C / min. After calcination for 2 hours, the calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0062] Example 3

[0063] Weigh 10 g of urea and place it in a crucible. Cover the crucible with a lid, wrap it with tin foil, and place it in a muffle furnace. Heat the temperature from room temperature to 550 °C at a heating rate of 5 °C / min and calcine for 3 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0064] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.404 g (1 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 40 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 1 h, then transferred to an 80°C oil bath and heated with stirring for 12 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 800°C at a heating rate of 2.5°C / min and calcined for 4 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven and dried at 50°C for 8 h to obtain EuFeO3 dark red powder.

[0065] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 20 mL of deionized water under ultrasonication for 1 hour. The flask containing the mixed solution was then transferred to a 70°C oil bath and stirred for 6 hours. The reaction product was placed in an oven set at 90°C for 8 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 400°C at a heating rate of 4°C / min. After calcination for 2 hours, the calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0066] Example 4

[0067] Weigh 12 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 5 °C / min and heat it to 600 °C for 2 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0068] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.485 g (1.2 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 45 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 1.5 h, then transferred to a 90 °C oil bath and heated with stirring for 10 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 900 °C at a heating rate of 4 °C / min and calcined for 3 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven set at 45 °C and dried for 10 h to obtain EuFeO3 dark red powder.

[0069] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 25 mL of deionized water under ultrasonication for 1.5 hours. The flask containing the mixed solution was then transferred to a 70°C oil bath and stirred for 6 hours. The reaction product was placed in an oven set at 90°C for 8 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 400°C at a heating rate of 4°C / min. After calcination for 2 hours, the calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0070] Example 5

[0071] Weigh 10 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 4°C / min and heat it to 450°C for 5 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0072] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.364 g (0.9 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 35 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 0.5 h, then transferred to a 60°C oil bath and heated with stirring for 14 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 850°C at a heating rate of 3°C / min and calcined for 4.5 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven set at 45°C and dried for 10 h to obtain EuFeO3 dark red powder.

[0073] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 15 mL of deionized water under ultrasonication for 1.5 hours. The flask containing the mixed solution was then transferred to a 70°C oil bath and stirred for 6 hours. The reaction product was placed in an oven set at 90°C for 8 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 400°C at a heating rate of 4°C / min and calcined for 2 hours. The calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0074] Example 6

[0075] Weigh 10 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 4 °C / min and heat it to 500 °C for 5 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0076] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.323 g (0.8 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 35 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 0.5 h, then transferred to a 70 °C oil bath and heated with stirring for 13 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 850 °C at a heating rate of 3 °C / min and calcined for 4.5 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven set at 45 °C and dried for 10 h to obtain EuFeO3 dark red powder.

[0077] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 25 mL of deionized water by ultrasonication for 0.5 h. The flask containing the mixed solution was then transferred to a 50°C oil bath and stirred for 8 h. The reaction product was placed in an oven set at 90°C and dried for 8 h. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 400°C at a heating rate of 4°C / min and calcined for 2 h. The calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0078] Example 7

[0079] Weigh 12 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 6°C / min and heat it to 600°C for 2 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0080] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.364 g (0.9 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 35 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 0.5 h, then transferred to a 75 °C oil bath and heated with stirring for 10 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 900 °C at a heating rate of 4 °C / min and calcined for 2 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven and dried at 50 °C for 8 h to obtain EuFeO3 dark red powder.

[0081] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 20 mL of deionized water by ultrasonication for 1 hour. The flask containing the mixed solution was then transferred to a 90°C oil bath and stirred for 4 hours. The reaction product was placed in an oven set at 90°C and dried for 8 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 300°C at a heating rate of 3°C / min and calcined for 4 hours. The calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0082] Example 8

[0083] Weigh 9 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 6°C / min and heat it to 600°C for 2 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0084] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.404 g (1 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 45 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 1.5 h, then transferred to a 100 °C oil bath and heated with stirring for 8 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 850 °C at a heating rate of 2 °C / min and calcined for 3 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven and dried at 60 °C for 6 h to obtain EuFeO3 dark red powder.

[0085] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 20 mL of deionized water under ultrasonication for 1 hour. The flask containing the mixed solution was then transferred to a 70°C oil bath and stirred for 6 hours. The reaction product was placed in an oven set at 90°C for 8 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 400°C at a heating rate of 4°C / min. After calcination for 2 hours, the calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0086] Example 9

[0087] Weigh 12 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 5.5 °C / min and heat it to 600 °C for 3 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0088] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.444 g (1.1 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 45 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 1.5 h, then transferred to a 90 °C oil bath and heated with stirring for 10 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 750 °C at a heating rate of 3 °C / min and calcined for 5 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven and dried at 55 °C for 8 h to obtain EuFeO3 dark red powder.

[0089] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 15 mL of deionized water under ultrasonication for 1.5 hours. The flask containing the mixed solution was then transferred to a 100°C oil bath and stirred for 4 hours. The reaction product was placed in an oven set at 100°C for 7 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 350°C at a heating rate of 3°C / min and calcined for 3 hours. The calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0090] Example 10

[0091] Weigh 8 g of urea and pour it into a porcelain crucible. Wrap it with tin foil and place it in a muffle furnace. Set the heating rate to 4 °C / min and heat it to 500 °C for 5 h. After cooling naturally to room temperature, take out the light yellow solid and grind it with an agate mortar to obtain g-C3N4 powder.

[0092] 0.428 g (1 mmol) Eu(NO3)3·5H2O and 0.485 g (1.2 mmol) Fe(NO3)3·9H2O were weighed separately and dissolved in 45 mL deionized water. 0.192 g (1 mmol) of anhydrous citric acid was added and the mixed solution in the round-bottom flask was ultrasonically dispersed for 1.5 h, then transferred to an 85°C oil bath and heated with stirring for 10 h. After the solvent was completely evaporated, the obtained solid product was placed in a muffle furnace and heated to 900°C at a heating rate of 3°C / min and calcined for 2 h. After cooling to room temperature, the initial product of the agate was washed with water and ethanol respectively and centrifuged. Finally, it was placed in a vacuum drying oven set at 45°C and dried for 10 h to obtain EuFeO3 dark red powder.

[0093] First, 200 mg of g-C3N4 and different amounts of EuFeO3 (0.2 mg, 0.5 mg, 1 mg, 2 mg, and 4 mg) were weighed and dispersed in 25 mL of deionized water under ultrasonication for 1.5 hours. The flask containing the mixed solution was then transferred to an 85°C oil bath and stirred for 5 hours. The reaction product was placed in an oven set at 80°C for 10 hours. Finally, the crucible containing the dried product was placed in a muffle furnace and heated to 350°C at a heating rate of 3°C / min and calcined for 3 hours. The calcined products were labeled as 0.1%, 0.25%, 0.5%, 1%, and 2% EuFeO3 / g-C3N4 composite materials, respectively. Other rare earth ferrites were prepared according to the same method.

[0094] 2. Performance Characterization of EuFeO3 / g-C3N4 Composite Materials

[0095] The morphology of the 0.25% EuFeO3 / g-C3N4 composite material prepared in the best embodiment 3 was characterized by TEM and SEM respectively. Figure 2 From the transmission electron microscope image (a), it can be observed that black EuFeO3 particles are successfully loaded onto the surface of the thick layer of g-C3N4 with a large number of wrinkles. The particle size is about 40nm. After further magnification of one of the EuFeO3 nanoparticles ( Figure 2 (b)), it was found that its lattice spacing is 0.343nm, corresponding to the (111) crystal plane of EuFeO3. SEM image of EuFeO3 / g-C3N4 composite material ( Figure 2 In (c), it can be observed that the layered structure of g-C3N4 contains many black holes, which may contain EuFeO3 nanoparticles. Figure 2(di) It can be clearly seen that the five elements C, N, O, Fe and Eu are densely distributed in the skeleton of the entire composite material structure, confirming that the EuFeO3 / g-C3N4 composite material was successfully prepared.

[0096] The elemental composition of 0.25% EuFeO3 / g-C3N4 prepared in the best embodiment 3 was studied by X-ray photoelectron spectroscopy (XPS). Figure 3 As shown. XPS spectrum ( Figure 3 (a) It can be observed that the composite material contains five elements: C, N, O, Fe and Eu. This result is consistent with the above Figure 2 The mapping test results are consistent. In the C1s spectrum ( Figure 3 (b)) Two peaks were found at 284.5 and 287.9 eV corresponding to CC / C=C bond and NC=N bond. Figure 3 (c)) observed that the peaks at 398.2, 400.3 and 403.7 eV were deconvoluted into three different peaks, which were attributed to sp 2 The presence of bonded N atoms (CN=C), tertiary groups (N-(C)3) and amino functional groups (CN). O 1s spectrum ( Figure 3 (d)) The peak at 531.9 eV corresponds to the C=O bond. Figure 3 (e) shows the Fe 2p peaks with binding energies of 711 and 723.1 eV, respectively, belonging to the Fe 2p 3 / 2 and Fe 2p 1 / 2 , corresponding to Fe or Fe in EuFeO3 3+ Chemical state. Figure 3 (f) The results show that the peaks at 1134.8 and 1123.9 eV correspond to Eu 3d 5 / 2 and Eu3d 3 / 2 , confirming that the chemical state of Eu in EuFeO3 is +3.

[0097] 3. Effect of EuFeO3 doping on the ECL behavior of g-C3N4 materials

[0098] ECL testing was performed using an MPI-E electrochemiluminescence analyzer with a three-electrode system. Glassy carbon electrode (GCE) or a glassy carbon electrode modified with different materials was used as the working electrode, Ag / AgCl electrode was used as the reference electrode, and platinum wire was used as the counter electrode. The initial potential was set to 0 V, the scanning speed was controlled at 150 mV / s, and the operating voltage of the photomultiplier tube was adjusted to 800 V.

[0099] During the experiment, a cyclic potential scan was first performed between -1.6V and 0V in a 0.1M phosphate buffer solution at pH 7.0 to observe the blank ECL signal of the glassy carbon electrode. Then, the ECL signals of EuFeO3, g-C3N4, and the 0.25% EuFeO3 / g-C3N4 composite material prepared in the best embodiment 3 modified onto the glassy carbon electrode as a luminescent reagent were tested. Figure 5 As shown in (a), when EuFeO3 is used as the luminescent reagent, almost no ECL signal is generated. Without other luminophores, the ECL signal intensity of g-C3N4 alone is also very weak. However, after combining the two, the cathode ECL signal intensity is significantly enhanced, indicating that the addition of EuFeO3 enhances the electrochemiluminescence of g-C3N4.

[0100] Cyclic voltammetry (CV) was performed on a Shanghai Chenhua CHI 660E electrochemical workstation. Figure 5 (b) The electrochemical behavior of different materials was studied. It was found that the single EuFeO3 and g-C3N4 materials had almost no redox peaks, while the 0.25% EuFeO3 / g-C3N4 composite material prepared in the best example 3 had a clear reduction peak at -0.75V, proving that there was an interaction between EuFeO3 and g-C3N4. The AC impedance test of the three materials can be used to study their charge transfer. Figure 5 As can be seen in (c), the Nyquist semicircle diameter of single EuFeO3 is the largest and its conductivity is the worst, followed by single g-C3N4. The Nyquist radius of the composite material is the smallest, which effectively improves the conductivity of the material, proving that the composite of EuFeO3 and g-C3N4 can effectively promote electron transfer. In addition, the synthesis method of the best embodiment 3 was used to prepare other rare earth ferrite / g-C3N4 composite materials with a doping amount of 0.25%, including 0.25% TmFeO3 / g-C3N4, 0.25% HoFeO3 / g-C3N4, 0.25% NdFeO3 / g-C3N4 and 0.25% YbFeO3 / g-C3N4, and the effects of these rare earth ferrites on the ECL signal intensity of g-C3N4 were studied under the same reaction conditions. Figure 5 As shown in (d), it was found that the ECL signal intensity displayed by 0.25% EuFeO3 / g-C3N4 was significantly stronger than that of other rare earth ferrite / g-C3N4 composite materials, indicating that EuFeO3 and g-C3N4 can play a synergistic role after being composited, thereby enhancing the overall ECL signal.

[0101] In addition, the effects of different atmospheres on the reaction system were studied during the experiment, such as Figure 5As shown in (e), compared with the air atmosphere, when Ar was introduced into the reaction system, the ECL signal intensity of 0.25% EuFeO3 / g-C3N4 showed a weakening trend, while when O2 was introduced into the reaction system, the ECL signal intensity of 0.25% EuFeO3 / g-C3N4 was enhanced, proving that dissolved oxygen participated in the reaction as a co-reactant in the ECL process.

[0102] 4. Effect of EuFeO3 / g-C3N4 composite modified electrode on Cd 2+ Electrochemiluminescence response and trace detection of

[0103] After testing, it was found that when Cd was added to the PBS buffer solution of the 0.25% EuFeO3 / g-C3N4 composite material prepared in the best embodiment 3 as a luminescent reagent, 2+ After that, the ECL signal intensity decreased significantly ( Figure 5 ), indicating that Cd 2+ In order to maximize the sensitization effect of the 0.25% EuFeO3 prepared in Example 3 on the ECL signal of g-C3N4, obtain the highest ECL signal, and facilitate subsequent high-sensitivity response and detection of the target, the following experimental conditions were optimized.

[0104] The choice of buffer solution has a significant effect on the ECL signal intensity of the composite material. Therefore, different types of buffer solutions were experimentally compared during the experiment, including Tris buffer solution, citric acid-sodium citrate buffer solution (CPBS), acetic acid-sodium acetate buffer solution (NaAc-HAc), boric acid-KCL buffer solution (BBS) and phosphate buffer solution (PBS). Figure 6 As shown in (a), the ECL signal intensity measured in Tris buffer solution is the lowest, while the ECL signal intensity measured in PBS buffer solution is much higher than that in other buffer solutions. Therefore, all subsequent comparative experiments were carried out in phosphate buffer solution. Figure 6 (b) The effect of pH value of PBS buffer solution on ECL signal intensity was studied in detail. The experimental results show that the ECL signal intensity is reduced under strong acid and alkaline conditions, while in a neutral environment, EuFeO3 / g-C3N4 composite material shows the best ECL response performance. Based on this finding, and taking into account the Cd 2+ In order to meet the requirements of the detection system, the experiment selected PBS buffer solution with a pH value of 7 as the base medium for subsequent target detection.

[0105] Subsequently, experimental comparisons were conducted on the doping amount of EuFeO3 in the composite material prepared in the best embodiment 3 and the modification amount of the 0.25% EuFeO3 / g-C3N4 composite material on GCE. Figure 6As shown in (c), when the doping amount of EuFeO3 is 0.25%, the ECL signal intensity of the EuFeO3 / g-C3N4 composite material is the highest. Then, as the doping amount of EuFeO3 increases, the ECL signal intensity gradually decreases. This may be because the high doping amount reduces its reactive sites. Therefore, the EuFeO3 / g-C3N4 composite material with a doping amount of 0.25% was selected as the luminescent material during the experiment. Figure 6 The experimental results in (d) show that the amount of 0.25% EuFeO3 / g-C3N4 composite material dispersion modified on GCE has a significant impact on the ECL signal intensity. When the modification amount is less than 2μL, the ECL signal intensity gradually increases with the increase in the modification amount. When the modification amount reaches 2μL, the ECL signal intensity is the highest. After further increasing the modification amount, the ECL signal does not continue to increase, but instead shows a downward trend. The reason for this phenomenon may be that the modification amount is too much, the modification layer is thicker, resulting in reduced conductivity, which affects its ECL signal intensity. Therefore, in the experiment, a modification amount of 2μL of 0.25% EuFeO3 / g-C3N4 composite material dispersion was selected to modify the GCE for measurement.

[0106] The study found that under the above optimal experimental conditions, the ECL signal intensity of the 0.25% EuFeO3 / g-C3N4 system prepared in the best embodiment 3 increased with the increase of Cd 2+ The concentration gradually decreased ( Figure 7 (a)), and the logarithm of the ECL signal intensity change value of the system is related to Cd 2+ There is a good linear relationship between the natural logarithm of the concentration ( Figure 6 (b)), the linear regression equation is logΔECL=0.2842lnC Cd 2+ (nM) + 2.078, the correlation coefficient was 0.9948, and the detection limit was calculated to be 3.25 nM according to the 3σ / S method (σ is the standard deviation of the blank solution determination, S is the slope of the linear equation), which was consistent with other methods (Beas-Bernuy LC, Cardenas-Riojas AA, Calderon-Zavaleta SL, Quiroz-Aguinaga U, La Rosa-Toro A, López EO, Asencios YJO, Baena-Moncada AM, Muedas-Taipe G.Cd 2+Detection by an Electrochemical Electrode Based on MWCNT-Orange PeelActivated Carbon[J].ACS Omega,2023,8(40):37341-37352.)Detection of Cd 2+ The effect is better.

[0107] In order to evaluate the EuFeO3 / g-C3N4 system for Cd 2+ During the experiment, a variety of potential interfering ions were introduced into the detection system, including Cu 2+ 、Hg 2+ , K + Mg 2+ NH 4+ 、Ni 2+ , Pb 2+ and Zn 2+ etc., investigated the effects of these possible coexisting ions of equal concentration on the detection results, such as Figure 8 (a) As shown. Other ions have little influence on the ECL signal of EuFeO3 / g-C3N4 system. 2+ After that, the ECL signal intensity decreased significantly, so it was concluded that the EuFeO3 / g-C3N4 system had a 2+ It has strong specific and selective recognition ability.

[0108] Repeated measurements of 1000 nM Cd were performed using a 0.25% EuFeO3 / g-C3N4 composite modified electrode. 2+ The reproducibility of the constructed sensor was examined by testing the solution 9 times. Figure 8 As shown in (b), the relative standard deviation (RSD) is only 2.31%. The electrode modified under the same conditions was stored at 4 ° C and tested every day for 5 consecutive days. It was found that the ECL value did not change significantly, indicating that the sensor has good reproducibility and long-term stability. The above experimental results show that the target product EuFeO3 / g-C3N4 composite material is used as a modifier. The electrochemiluminescence sensor can be used to detect Cd 2+ response and microanalysis detection.

[0109] Based on the above experimental results and existing research reports (Lin Z, Li P, Zheng D, Huang L, Chen Y, Gao W. Highly efficient synthesis of CeO2@g-C3N4 double-shelled hollow spheres for ultrasensitive self-enhanced electrochemiluminescence biosensors[J]. Microchemical Journal, 2023, 190: 108588-108595; Dewangan L, Chawre Y, Korram J, et al. N-doped, silver, and cerium co-doped carbon quantum dots based sensor for detection of Hg 2+ and captopril[J].Microchemical Journal,2022,182:107867-107875.), it is speculated that in a system containing EuFeO3 / g-C3N4 and the co-reactant O2, the composite material obtains electrons during the electrochemical reduction process to form EuFeO3 / g-C3N4 with strong reducing properties. ·- Active substances. At the same time, dissolved oxygen molecules undergo electrochemical reduction in the electrode interface area, directly generating the main product H2O2, and some oxygen molecules may first undergo O2 - ·The intermediate state is finally converted into H2O2; then H2O2 is further reduced to ·OH on the electrode surface, and ·OH reacts with EuFeO3 / g-C3N4 enriched on the surface of the material ·- Electron transfer occurs, prompting the system to form an excited state EuFeO3 / g-C3N4* and transition back to the ground state, which then releases a significant ECL signal. 2+ Afterwards, the free radicals are annihilated, electron transport is hindered or the luminescent sites on the surface of the composite material are covered, resulting in the quenching of ECL luminescence.

[0110] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a EuFeO3 / g-C3N4 composite material, characterized in that: The steps include: 1) Weigh 8-12 mg of urea into a porcelain crucible, cover it with tin foil, and calcine it in a muffle furnace. After cooling naturally to room temperature, remove the light yellow solid and grind it in an agate mortar to obtain g-C3N4 powder; 2) A certain amount of Eu(NO3)3·5H2O and Fe(NO3)3·9H2O were weighed and dissolved in deionized water. An equal amount of anhydrous citric acid was added to the Eu(NO3)3·5H2O, and the mixed solution in the round-bottom flask was ultrasonically dispersed. The mixture was then transferred to an oil bath and heated with stirring. After the solvent was completely evaporated, the obtained solid product was calcined in a muffle furnace. After cooling to room temperature, the agate powder was washed with water and ethanol, respectively, and centrifuged. Finally, it was dried in a vacuum drying oven to obtain a dark red EuFeO3 powder. 3) Ultrasonic dispersion of g-C3N4 powder and EuFeO3 powder in deionized water, then transfer the flask containing the mixed solution to an oil bath for stirring and reaction, dry the reaction product in an oven, and finally calcine the crucible containing the dried product in a muffle furnace to obtain a EuFeO3 / g-C3N4 composite material.

2. The preparation method according to claim 1, characterized in that In step 1), the calcination parameters of the muffle furnace are: heating to 400-600° C. at a heating rate of 4-6° C. / min, and the calcination time is controlled at 2-6 hours.

3. The preparation method according to claim 1, characterized in that In step 2), the molar ratio of Eu(NO3)3·5H2O to Fe(NO3)3·9H2O is 1:0.8-1.

2.

4. The preparation method according to claim 1, characterized in that In step 2), the temperature of the oil bath is controlled at 60-100° C., and the heating and stirring time is controlled at 8-15 h.

5. The preparation method according to claim 1, characterized in that In step 2), the calcination parameters of the muffle furnace are: heating to 700-900° C. at a heating rate of 2-4° C. / min, and the calcination time is controlled at 2-6 hours.

6. The preparation method according to claim 1, characterized in that In step 2), the drying temperature of the vacuum drying oven is controlled at 40-60° C., and the drying time is controlled at 6-12 hours.

7. The preparation method according to claim 1, characterized in that In step 3), the temperature of the oil bath is controlled at 50-90° C., and the stirring reaction time is controlled at 4-8 h.

8. The preparation method according to claim 1, characterized in that In step 3), the drying temperature of the oven is controlled at 70-100° C., and the drying time is controlled at 6-10 hours.

9. The preparation method according to claim 1, characterized in that In step 3), the calcination parameters of the muffle furnace are: heating to 300-500° C. at a heating rate of 3-5° C. / min, and the calcination time is controlled at 1-4 h.

10. The EuFeO3 / g-C3N4 nanocomposite material obtained by the preparation method according to claim 1 is used in the preparation of heavy metal ion Cd 2+ Application of Electrochemiluminescence Sensors for Identification and Trace Detection

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