A method and device for fluorescence detection of lead ions

Abstract

The present invention discloses a fluorescence detection method and device for lead ions, comprising the following steps: Step 1, prepare CDs@MIL-101-NH2 material; Step 2, establish a standard curve of the change in fluorescence intensity of CDs@MIL-101-NH2 and the concentration of lead ions; Step 3, fully mix and react the water source to be tested with the CDs@MIL-101-NH2 for a fixed time to obtain a test mixture, and use a fluorescence detection device to detect the test mixture to obtain the concentration value of lead ions. The fluorescence detection device includes a power supply, an excitation light source, an optical window, a filter, a reference detector, a fluorescence detector, a photodetector, a signal collector, a transmission cable, and a display terminal. The method and device provided by the present invention have the advantages of fast detection speed, simple operation, low price, etc., and are suitable for the monitoring of remote and scattered water sources and the emergency monitoring of sudden environmental incidents.

Description

Technical Field

[0001] The present invention relates to the field of lead ion detection, and in particular to a method and device for fluorescence detection of lead ions. Background Art

[0002] Lead (Pb) is a ubiquitous heavy metal with physiological toxicity and bioaccumulation. Even low-concentration exposure can cause permanent damage to the human body and living environment. It is recognized as one of the most toxic metals. Lead ions mainly come from industries such as lead smelting, battery manufacturing, printing and mining. Heavy metals that enter surface runoff through the hydrological cycle will accumulate in water bodies and easily cause harm to the surrounding environment. For example, Pb 2+ Entering the human body from wastewater and waste residues can cause damage to the human hematopoietic system, nervous system, and digestive system. According to the surface water environmental quality standards, Pb in Class V water 2+ The content is not higher than 0.1mg / L.

[0003] At present, common methods for heavy metal detection include atomic spectroscopy, chromatography, electrochemical method, inductively coupled plasma emission spectroscopy, surface enhanced Raman spectroscopy and other methods. However, these methods have the disadvantages of complex pretreatment, time-consuming, expensive equipment and not easy to carry. Compared with the above methods, the fluorescent sensor has a low detection limit, high sensitivity, simple operation, and easy miniaturization, which is convenient to design into a portable instrument, suitable for on-site rapid detection, and has broad application prospects. In the current invention, there is a DNA enzyme system composed of nucleotide chain A and nucleotide chain B, and the aggregation-induced luminescence effect of the aggregation-induced luminescence material combined with the vertical arrangement on the substrate and the mutual coordination of the optical properties of the nematic phase liquid crystal, so as to achieve high specificity and high sensitivity of lead ions. The disadvantage of this method is that it requires the synthesis of nucleic acid aptamers, which is cumbersome to operate, costly, and not specifically designed as a portable device. There is also a method for preparing an electrical sensor material that can simultaneously detect lead ions and copper ions, and the preparation method is to slowly add ferric chloride hexahydrate and terephthalic acid to N, N-dimethylformamide solution, and the mixture is transferred to a reactor for reaction. The intermediate A obtained after the reaction is evenly dispersed by ultrasonication, and then silver nitrate and potassium chromate are added. Finally, it is washed and dried to obtain the final product. The advantage of this material is that lead ions and copper ions can be detected simultaneously by electrochemical method, but the disadvantage is that the design idea of ​​the material to the sensor is not presented. The scheme most similar to this scheme is that in the 20mMTris-HAc (pH=7.4) system, lead ions have a strong fluorescence emission peak at 620nm. As the concentration of lead ions increases, lead ions can be quantitatively detected. Although this method has high sensitivity and good selectivity for lead ions, it must meet the prerequisite of the 20mMTris-HAc (pH=7.4) system, which is not conducive to operation and cannot cope with water quality monitoring in complex environments. Secondly, this method has not been constructed into a complete system, and there is no implementation method for portable instruments.

[0004] Based on the above background, the present invention is based on CDs@MIL-101-NH 2 As the core of fluorescent sensing, the material builds a complete system for detecting lead ions and realizes lead ion detection in complex scenarios. 2 Fe is the central metal of MOFs materials. Compared with other luminescent MOFs materials, such as lanthanide metals, the transition metal Fe is more environmentally friendly, with a wide source, low cost and environmental protection. 2 The fluorescence intensity of the material can be increased and the detection performance can be improved. In addition, the present invention also constructs a complete set of fluorescence detection methods for lead ions, which realizes the detection of lead ions from special CDs@MIL-101-NH 2 Preparation, establishment of lead ion detection line, and design of portable detection device.

[0005] In summary, among the existing schemes of fluorescence method, some need to synthesize complex nucleic acid aptamers or nanoparticles, and some need to meet certain system requirements, which are difficult to achieve in practical applications. The common shortcoming is that they only propose the preparation of materials, and do not construct a complete method from material preparation, performance detection to equipment implementation. Therefore, technicians in this field are committed to developing a new detection method and detection device that is easy to operate and accurate in measurement to solve the problem of water quality monitoring in complex environments. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to accurately, conveniently and quickly detect the concentration of lead ions in water.

[0007] To achieve the above object, the present invention provides a method for fluorescence detection of lead ions, characterized in that it comprises the following steps:

[0008] Step 1: Preparation of CDs@MIL-101-NH 2 Material;

[0009] Step 2: Create CDs@MIL-101-NH 2 The standard curve of fluorescence intensity change and lead ion concentration;

[0010] Step 3: Mix the water source to be tested with the CDs@MIL-101-NH 2 After sufficient mixing and reacting for a fixed time, a mixed solution to be tested is obtained, and the mixed solution to be tested is detected using a fluorescence detection device to obtain a concentration value of lead ions.

[0011] Furthermore, step 1 also includes the following steps:

[0012] Step 1), preparation of carbon dots (N, S, I-CDs): Potassium iodate and thiocyanate were mixed in deionized water at room temperature, and ethylenediamine was added, and ultrasonic vibration was performed until it was completely dissolved. The mixed solution was placed in a polytetrafluoroethylene reactor and reacted at high temperature. After the reaction was completed, the mixture was taken out and naturally cooled to room temperature. The mixed solution after the reaction was filtered and stored for later use;

[0013] Step 2), using a hydrothermal method, FeCl3·6H2O and NH2-H2BDC were dispersed in DMF at room temperature, ultrasonically dissolved, and then CDs solution was added to transfer the mixed solution to a polytetrafluoroethylene reactor, placed in an oven for reaction, and naturally cooled to room temperature after the reaction was completed. The product was centrifuged, washed by centrifugation to remove excess impurities, and dried under vacuum conditions to obtain CDs@MIL-101-NH 2 .

[0014] Furthermore, step 2 also includes the following steps:

[0015] Step 1), optimal excitation and emission wavelengths: Fluorescence spectrometer FLS1000 (Edinburgh, UK), measured at room temperature, using a 450W xenon lamp and a photomultiplier tube (PMT900) as the test light source; the test liquid container is a quartz cuvette (1cm×1cm), and the excitation wavelength and slit width take into account both the sample characteristics and the maximum fluorescence intensity accepted by the instrument;

[0016] Step 2), optimal concentration: 5, 10, 25, 50, 100, 200, 300, 500 mg / L, measure the above concentrations CDs@MIL-101-NH 2 The fluorescence intensity was calculated to obtain the optimal concentration value;

[0017] Step 3), optimal pH value: preparation of CDs@MIL-101-NH 2 The solution was then adjusted to pH 5-13 using 1 mol / L sulfuric acid and sodium hydroxide solutions, and the pH of CDs@MIL-101-NH 2 The fluorescence intensity of the solution was used to obtain the optimal pH value;

[0018] Step 4), optimal response time: set the response time to 1, 20, 60, 90, 120, 150, 180, 240, 300 min, and detect the optimal concentration value and the optimal pH value of CDs@MIL-101-NH at each response time. 2 The fluorescence intensity of the solution was used to obtain the optimal response time;

[0019] Step 5), after the optimal response time, detect the optimal concentration value and the optimal pH value of CDs@MIL-101-NH 2 The fluorescence intensity of the solution increases with the increase of Pb 2+ The concentration of CDs@MIL-101-NH was changed (0, 10, 20, 40, 60, 80, 100, 120, 150, 180, 200, 240, 280, 320, 360, 400, 450, 500 μM). 2 The standard curve of fluorescence intensity change and lead ion concentration.

[0020] Furthermore, step 3 also includes the following steps:

[0021] Step 1), turning on the power supply of the fluorescence detection device;

[0022] Step 2), the excitation light source emits 340nm monochromatic light;

[0023] Step 3), the excited monochromatic light is divided into two paths, one path of light is collected by a reference light detector to detect the light source intensity, which is used to offset or balance the influence of the light source's luminous intensity on temperature and service life; the other path of light is used to excite the fluorescent substance in the mixed solution to be tested to generate fluorescence;

[0024] Step 4), the fluorescence detector collects and processes the fluorescence signal sensed through the bandpass filter with a central wavelength of 436nm, and converts the optical signal into an electrical signal;

[0025] Step 5) Use the long-distance transmission RS485 communication interface and standard Modbus protocol to connect to the computer, and use professional data acquisition software to display the measurement results.

[0026] Furthermore, the fluorescence detection device includes a power supply, an excitation light source, an optical window, a filter, a reference detector, a fluorescence detector, a signal collector, a transmission cable and a display terminal; the power supply drives the excitation light source to emit continuous monochromatic light, and the monochromatic light is irradiated to the CDs@MIL-101-NH to be tested through the optical window. 2 Fluorescence is generated in the solution, and the fluorescence is irradiated to the fluorescence detector after passing through the filter. The fluorescence detector converts the optical signal into an electrical signal and transmits it to the signal collector. The reference detector converts the optical signal into an electrical signal and transmits it to the signal collector. The signal collector converts the received electrical signal into data information and transmits it to the display terminal through the transmission cable. The display terminal displays the measurement result of the lead ion concentration.

[0027] Furthermore, the monochromatic light emitted by the excitation light source has a wavelength of 340 nm.

[0028] Furthermore, the central wavelength of the filter is 436 nm.

[0029] Furthermore, the signal collector processes the received electrical signal through data acquisition software and converts it into data information, and then transmits the data information to the display terminal for display through the transmission cable.

[0030] Furthermore, the transmission cable is connected to the display terminal via a USB485 interface.

[0031] Furthermore, the data acquisition software is designed using Visual Studio as a development platform.

[0032] Compared with the traditional detection method, the present invention proposes a complete method from material preparation, performance detection to system implementation. The method provided by the present invention has the advantages of fast detection speed, simple operation, low price, etc., and is suitable for monitoring remote and dispersed water sources and emergency monitoring of sudden environmental events.

[0033] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Pb is a preferred embodiment of the present invention 2+ Schematic diagram of the linear relationship with the fluorescence intensity quenching of CDs@MIL-101-NH2(Fe);

[0035] Figure 2 It is a schematic diagram of the detection principle of a fluorescence detection device of a preferred embodiment of the present invention;

[0036] Figure 3 It is a schematic diagram of the structural framework of a fluorescence monitoring device of a preferred embodiment of the present invention;

[0037] Figure 4 It is a schematic diagram of the internal structure of a fluorescence monitoring device according to a preferred embodiment of the present invention.

[0038] Among them, 1-cleaning brush, 2-filter, 3-fluorescence detector, 4-stainless steel sleeve, 5-mounting thread, 6-optical window, 7-excitation light source, 8-reference detector, 9-cable protective cover. DETAILED DESCRIPTION

[0039] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0040] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0041] This embodiment is a method for fluorescent detection of lead ions. First, a fluorescent quantitative detection material for lead ions is prepared, and the specific steps are as follows:

[0042] CDs@MIL-101-NH 2 Preparation:

[0043] First, the preparation of carbon dots (N, S, I-CDs): 250 mg potassium iodate and 25 mg thiocyanate were mixed in 25 ml deionized water at room temperature, 1.5 ml ethylenediamine was added, and ultrasonic vibration was performed until completely dissolved. The mixed solution was placed in a 50 ml polytetrafluoroethylene reactor (a stainless steel autoclave lined with polytetrafluoroethylene), and the temperature was set to 180 ° C for 8 hours. After the reaction was completed, it was taken out and naturally cooled to room temperature. The reaction mixture was filtered with a 0.22 μm hydrophilic PTFE filter membrane, and the clarified solution was stored at 4 ° C for use.

[0044] Then, FeCl 3 6H 2 O and NH 2 -H 2 BDC was dispersed in DMF (N, N-dimethylformamide), dissolved by ultrasonication, and then CDs solution (N, S, I-CDs) was added. The mixture was transferred to a polytetrafluoroethylene reactor and placed in an oven for reaction. After the reaction was completed, it was naturally cooled to room temperature, and the product was centrifuged, washed by centrifugation to remove excess impurities, and dried under vacuum conditions to obtain CDs@MIL-101-NH 2 .

[0045] Establish a standard curve for lead ions and screen the optimal conditions for establishing the standard curve. The specific steps are as follows:

[0046] Optimal excitation and emission wavelengths: Fluorescence spectrometer FLS1000 (Edinburgh, UK), measured at room temperature, using a 450W xenon lamp and a photomultiplier tube (PMT900) as the test light source; the test liquid container is a quartz cuvette (1cm×1cm), the excitation wavelength and slit width take into account both the sample characteristics and the maximum fluorescence intensity accepted by the instrument; Optimal concentrations: 5, 10, 25, 50, 100, 200, 300, 500 mg / L, the above concentrations CDs@MIL-101-NH 2 The fluorescence intensity was calculated to obtain the optimal concentration; the optimal pH value was used to prepare the optimal concentration of CDs@MIL-101-NH 2 The solution was then adjusted to pH 5-13 using 1 mol / L sulfuric acid and sodium hydroxide solutions, and the pH of CDs@MIL-101-NH 2 The fluorescence intensity of the solution was measured to obtain the optimal pH value; the optimal response time was set to 1, 20, 60, 90, 120, 150, 180, 240, and 300 min, and the CDs@MIL-101-NH at the optimal concentration and the optimal pH value at each response time was detected. 2 The fluorescence intensity of the solution was measured to obtain the optimal response time.

[0047] The optimal excitation and emission wavelengths were finally 340nm and 436nm; the optimal concentration of the material was 10mg / L; the optimal pH was 7; and the optimal response time was 1min.

[0048] like Figure 1 As shown, using the optimal excitation wavelength of 340 nm and the emission wavelength of 436 nm, after the optimal response time of 1 min, the CDs@MIL-101-NH with the optimal concentration of 10 mg / L and the optimal pH of 7 was detected. 2 The fluorescence intensity of the solution increases with the increase of Pb 2+ The concentration of CDs@MIL-101-NH was changed (0, 10, 20, 40, 60, 80, 100, 120, 150, 180, 200, 240, 280, 320, 360, 400, 450, 500 μM). 2 The standard curve of fluorescence intensity change and lead ion concentration.

[0049] like Figure 2 As shown in the figure, the principle of a fluorescence detection device for heavy metal lead ions is that the lead ions in the water sample are reacted with 10 mg / L CDs@MIL-101-NH 2 The (Fe) fluorescent probe reacts and the fluorescence intensity is quenched.

[0050] like Figure 3 As shown, a structural framework of a fluorescence detection device for lead ions includes a power supply, an excitation light source, a reference detector, a fluorescence detector and data acquisition software.

[0051] like Figure 4 As shown, a fluorescence detection device for lead ions includes a power supply, a cleaning brush 1, a filter 2, a fluorescence detector 3, a stainless steel sleeve 4, a mounting thread 5, an optical window 6, an excitation light source 7, a reference detector 8, a cable protective cover 9, a signal collector, a transmission cable and a display terminal; the power supply drives the excitation light source 7 to emit continuous monochromatic light, and the monochromatic light is irradiated to the CDs@MIL-101-NH in the sample pool through the optical window 6. 2(Fe) solution to produce fluorescence, the fluorescence passes through the filter 2 and then irradiates the fluorescence detector 3, the fluorescence detector 3 converts the optical signal into an electrical signal and then transmits it to the signal collector, the reference detector 8 converts the optical signal into an electrical signal and then transmits it to the signal collector, the signal collector converts the received electrical signal into data information and then transmits it to the display terminal through the transmission cable, and the display terminal displays the concentration measurement result of lead ions. The excitation light source 7 emits 340nm monochromatic light; the excited monochromatic light is divided into two paths, one of which is collected by the reference detector 8 to detect the intensity of the light source, which is used to offset or balance the influence of the light source's luminous intensity on temperature and service life; the other light is used to excite the fluorescent substance in the mixed solution to be tested to produce fluorescence; the fluorescence detector 3 collects and processes the fluorescence signal sensed through the filter 2 with a central wavelength of 436nm, and converts the optical signal into an electrical signal; the computer is connected using a long-distance transmission RS485 communication interface and a standard Modbus protocol, and is equipped with professional data acquisition software to display the measurement results.

[0052] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for fluorescent detection of lead ions, characterized in that: The following steps are involved: Step 1, preparing CDs@MIL-101-NH2 material; comprising the following steps: Step 1), preparation of carbon dots (N, S, I-CDs): Potassium iodate and thiocyanate were mixed in deionized water at room temperature, and ethylenediamine was added, and ultrasonic vibration was performed until it was completely dissolved. The mixed solution was placed in a polytetrafluoroethylene reactor and reacted at high temperature. After the reaction was completed, the mixture was taken out and naturally cooled to room temperature. The mixed solution after the reaction was filtered and stored for later use; Step 2), using a hydrothermal method, FeCl3·6H2O and NH2-H2BDC are dispersed in DMF at room temperature, ultrasonically dissolved, and then CDs solution is added to transfer the mixed solution to a polytetrafluoroethylene reactor, placed in an oven for reaction, and naturally cooled to room temperature after the reaction is completed. The product is centrifuged, washed by centrifugation to remove excess impurities, and dried under vacuum conditions to obtain CDs@MIL-101-NH2; Step 2, establish a standard curve of the fluorescence intensity change of CDs@MIL-101-NH2 and the lead ion concentration; Step 3: Fully mix the water source to be tested and the CDs@MIL-101-NH2 and react for a fixed time to obtain a mixed solution to be tested, and use a fluorescence detection device to detect the mixed solution to obtain the concentration value of lead ions.

2. The method for fluorescent detection of lead ions according to claim 1, wherein: Step 2 also includes the following steps: Step 1), optimal excitation and emission wavelengths: Edinburgh, UK fluorescence spectrometer FLS1000, measured at room temperature, using a 450W xenon lamp and a photomultiplier tube PMT900 as the test light source; the test liquid container is a 1cm×1cm quartz cuvette, and the excitation wavelength and slit width take into account both the sample characteristics and the maximum fluorescence intensity accepted by the instrument; Step 2), optimal concentration: 5, 10, 25, 50, 100, 200, 300, 500 mg / L, measure the fluorescence intensity of CDs@MIL-101-NH2 at the above concentrations to obtain the optimal concentration value; Step 3), optimal pH value: prepare a CDs@MIL-101-NH2 solution of optimal concentration, and then adjust its pH to 5-13 using 1 mol / L sulfuric acid and sodium hydroxide solution, respectively, and measure the fluorescence intensity of the CDs@MIL-101-NH2 solution at the pH to obtain the optimal pH value; Step 4), optimal response time: set the response time to 1, 20, 60, 90, 120, 150, 180, 240, 300 min, detect the fluorescence intensity of the CDs@MIL-101-NH2 solution at the optimal concentration value and the optimal pH value at each response time, and obtain the optimal response time; Step 5), after the optimal response time, the fluorescence intensity of the CDs@MIL-101-NH2 solution at the optimal concentration value and the optimal pH value is detected as Pb 2+ The standard curve of the fluorescence intensity change of CDs@MIL-101-NH2 and the lead ion concentration was established. 2+ The concentrations are 0, 10μM, 20μM, 40μM, 60μM, 80μM, 100μM, 120μM, 150μM, 180μM, 200μM, 240μM, 280μM, 320μM, 360μM, 400μM, 450μM, and 500μM respectively.

3. The method for fluorescent detection of lead ions according to claim 1, wherein: Step 3 also includes the following steps: Step 1), turning on the power supply of the fluorescence detection device; Step 2), the excitation light source emits 340nm monochromatic light; Step 3), the excited monochromatic light is divided into two paths, one path of light is collected by a reference light detector to detect the light source intensity, which is used to offset or balance the influence of the light source's luminous intensity on temperature and service life; the other path of light is used to excite the fluorescent substance in the mixed solution to be tested to generate fluorescence; Step 4), the fluorescence detector collects and processes the fluorescence signal sensed through the bandpass filter with a central wavelength of 436nm, and converts the optical signal into an electrical signal; Step 5) Use the long-distance transmission RS485 communication interface and standard Modbus protocol to connect to the computer, and use professional data acquisition software to display the measurement results.

4. A lead ion fluorescence detection device, characterized in that: The fluorescence detection device includes a power supply, an excitation light source, an optical window, a filter, a reference detector, a fluorescence detector, a signal collector, a transmission cable and a display terminal; the power supply drives the excitation light source to emit continuous monochromatic light, the monochromatic light is irradiated to the CDs@MIL-101-NH2 solution to be tested through the optical window to generate fluorescence, the fluorescence is irradiated to the fluorescence detector after passing through the filter, the fluorescence detector converts the optical signal into an electrical signal and transmits it to the signal collector, the reference detector converts the optical signal into an electrical signal and transmits it to the signal collector, the signal collector converts the received electrical signal into data information and transmits it to the display terminal through the transmission cable, and the display terminal displays the measurement result of the lead ion concentration; The preparation of CDs@MIL-101-NH2 comprises the following steps: Step 1), preparation of carbon dots (N, S, I-CDs): Potassium iodate and thiocyanate were mixed in deionized water at room temperature, and ethylenediamine was added, and ultrasonic vibration was performed until it was completely dissolved. The mixed solution was placed in a polytetrafluoroethylene reactor and reacted at high temperature. After the reaction was completed, the mixture was taken out and naturally cooled to room temperature. The mixed solution after the reaction was filtered and stored for later use; Step 2), using a hydrothermal method, FeCl3·6H2O and NH2-H2BDC are dispersed in DMF at room temperature, ultrasonically dissolved, and then the CDs solution is added to transfer the mixed solution to a polytetrafluoroethylene reactor, placed in an oven for reaction, and naturally cooled to room temperature after the reaction is completed. The product is centrifuged, washed by centrifugation to remove excess impurities, and dried under vacuum conditions to obtain CDs@MIL-101-NH2.

5. The lead ion fluorescence detection device according to claim 4, characterized in that: The wavelength of the monochromatic light emitted by the excitation light source is 340nm.

6. The lead ion fluorescence detection device according to claim 4, characterized in that: The central wavelength of the filter is 436 nm.

7. The lead ion fluorescence detection device according to claim 4, characterized in that: The signal collector processes the received electrical signal through data acquisition software and converts it into data information, and then transmits the data information to the display terminal for display through the transmission cable.

8. The lead ion fluorescence detection device according to claim 4, characterized in that: The transmission cable is connected to the display terminal via a USB485 interface.

9. The lead ion fluorescence detection device according to claim 7, characterized in that: The data acquisition software is designed using Visual Studio as a development platform.

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