CN111117596B - Quantum dot/agar composite prepared by one-pot method and method for detecting metal ions by using quantum dot/agar composite - Google Patents
Quantum dot/agar composite prepared by one-pot method and method for detecting metal ions by using quantum dot/agar composite Download PDFInfo
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Abstract
The invention provides a quantum dot/agar composite prepared by a one-pot method and a method for detecting metal ions by the quantum dot/agar composite, which are characterized in that agar is used as a stabilizer in the preparation process of manganese-doped zinc sulfide quantum dots, a novel and simple one-pot method is adopted to prepare the manganese-doped zinc sulfide quantum dot/agar composite with the metal ion detection function, and the method comprises the following steps: 1) preparing a manganese-doped zinc sulfide quantum dot/agar composite; 2) and (3) preparing the manganese-doped zinc sulfide quantum dot/agar composite gel pellet. And (3) carrying out metal ion detection by using the quantum dot/agar composite. The one-pot preparation method has the advantages of simple method, environmental friendliness, greenness, no toxicity, mild reaction conditions, convenience in post-treatment process and the like. The manganese-doped zinc sulfide quantum dot/agar composite prepared by the invention has good detection effect on the detection of metal ions such as copper ions, and has reliable detection means, convenient detection method and easy separation from a system to be detected after detection. The manganese-doped zinc sulfide quantum dot/agar composite has good application value in the fields of metal ion detection and the like.
Description
Technical Field
The invention belongs to the technical fields of high polymer materials, nano materials, analysis and detection and the like, and particularly relates to a quantum dot/agar composite prepared by a one-pot method and a method for detecting metal ions by using the quantum dot/agar composite.
Background
Agar is a long-chain polysaccharide extracted from red algae plants, is a natural polymer material with abundant resources and stable properties, has good biocompatibility and biodegradability, and has good application value in the fields of drug delivery carrier systems, preparation of nano particles, food engineering and the like. The basic structural unit of agar is composed of galactose and galactose derivatives, and the galactose residue is connected with sulfate, methoxyl and pyruvate groups to different degrees. The long-chain polysaccharide having no such groups on galactose residues is called agarose, which is a gel-forming component, and the long-chain polysaccharide having such groups is called agar gel, which is a non-gel component, so that agar is mainly composed of two parts, agar gel and agarose, which is a main component for forming gels. Agar swells only by absorbing water at ambient temperatures, dissolves in water to form a solution when the temperature is raised to about 90 ℃, is relatively temperature stable, can be subjected to repeated treatments at temperatures of 100 ℃ or higher, and begins to form a gel when the temperature drops below about 30 ℃.
In recent years, research on natural polymer and nanoparticle composite materials has attracted great attention of researchers. It is noted that some natural polymers can be used as stabilizers in the nanoparticle preparation process [ Journal of Physics-Condensed Matter,2007,19(38):386237 ]. On one hand, the natural polymers can stabilize the nano particles, and effectively reduce the agglomeration effect in the preparation process of the nano particles; on the other hand, the use of toxic chemical stabilizers (such as 3-mercaptopropionic acid and the like) is avoided, so that the stabilizer prepared by using the natural polymer as the nanoparticles meets the requirements of environmental protection and sustainable development strategy. For example, Mathew et al prepared silver nanoparticles efficiently in an aqueous medium using agar as a stabilizer, and the prepared silver nanoparticles showed excellent catalytic activity for the reduction of methyl orange [ Journal of Molecular Liquids,2014,197:346-352 ].
The quantum dot is a novel nano material with excellent fluorescence performance, the three-dimensional size of the quantum dot is nano-scale, and the quantum dot is generally composed of II-VI group elements or III-V group elements. The unique property of the quantum dot is based on the quantum effect of the quantum dot, when the particle size enters the nanometer level, the size confinement causes the size effect, the quantum confinement effect and the surface effect, so that the low-dimensional physical property different from that of a macroscopic system and a microscopic system is generated, and the quantum dot has physical properties and optical effects which cannot be compared with that of a macroscopic material. In recent years, some non-toxic or low-toxic quantum dots such as manganese-doped zinc sulfide quantum dots have attracted much attention. The manganese-doped zinc sulfide quantum dot has the advantages of long excited state life, smaller self-quenching effect, good thermal stability and Chemical stability and the like, and the advantages ensure that the manganese-doped zinc sulfide quantum dot has good application value in the fields of fluorescence detection analysis, cell imaging, biological labeling and the like [ Chemical Society Reviews,2013,42(12):5489-5521 ].
Currently, researchers have actively developed the research of applying quantum dots to detection and analysis, for example, Ma et al use dopamine-modified manganese-doped zinc sulfide quantum dots as fluorescent probes to detect tyrosinase in human serum [ Sensors and Actuators B: Chemical,2018,256: 1069-. Li et al used gold/proline functionalized graphene quantum dots as detection platform for electrochemical detection of acetamidophenol [ Rsc Advances,2016,6(48):42751-42755 ]. However, the operation process of the quantum dots applied to detection and analysis is often complicated; on the other hand, some toxic reagents are used in the preparation process of constructing the quantum dot system applied to the aspect of detection and analysis, and the preparation process is complex. Therefore, the quantum dot detection system which is simple in construction and preparation method, mild in reaction condition, environment-friendly and non-toxic in preparation process, convenient in post-treatment process and convenient in detection method is still the technical problem to be solved.
In conclusion, agar is used as a stabilizer in the preparation process of the manganese-doped zinc sulfide quantum dots, and a novel, simple, green and environment-friendly one-pot method is adopted to prepare the manganese-doped zinc sulfide quantum dot/agar composite with the metal ion detection function. The one-pot preparation method has the advantages of environmental friendliness, no toxicity, mild reaction conditions, convenience in post-treatment process and the like. Meanwhile, because the manganese-doped zinc sulfide quantum dots exist in the prepared manganese-doped zinc sulfide quantum dot/agar composite, the manganese-doped zinc sulfide quantum dot/agar composite has the fluorescence property of the manganese-doped zinc sulfide quantum dots, has strong fluorescence stability at normal temperature, shows good detection effect on the detection of metal ions such as copper ions, and has reliable detection means, convenient detection method and easy separation from a system to be detected after detection. Therefore, the manganese-doped zinc sulfide quantum dot/agar composite has good application value in the fields of metal ion detection and analysis and the like. However, the quantum dot/agar composite prepared by the one-pot method and the method for detecting metal ions by using the quantum dot/agar composite are not reported in documents and patents.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the preparation method has the advantages of low cost, mild reaction conditions, simple and convenient preparation process, environmental friendliness, and meanwhile, the manganese-doped zinc sulfide quantum dot/agar compound has the fluorescence property of the manganese-doped zinc sulfide quantum dot due to the existence of the manganese-doped zinc sulfide quantum dot in the obtained manganese-doped zinc sulfide quantum dot/agar compound, has strong fluorescence stability at normal temperature, shows good detection effect on the detection of metal copper ions, is reliable in detection means and convenient and fast in detection method, and is easy to separate from an object system to be detected after detection.
The technical scheme provided by the invention for solving the technical problems is as follows: a quantum dot/agar composite prepared by a one-pot method is characterized in that: firstly, agar is used as a stabilizer in the preparation process of the manganese-doped zinc sulfide quantum dots, and a green, environment-friendly, novel and simple one-pot method is adopted to prepare a manganese-doped zinc sulfide quantum dot/agar compound with a metal ion detection function; and dripping the prepared manganese-doped zinc sulfide quantum dot/agar composite solution into cold soybean oil to form manganese-doped zinc sulfide quantum dot/agar composite gel balls, thus obtaining the quantum dot/agar composite prepared by a one-pot method. And then, metal ions such as copper ions have a quenching effect on the fluorescence of the manganese-doped zinc sulfide quantum dots, namely the copper ions can enable the fluorescence of the manganese-doped zinc sulfide quantum dots/agar complexes to disappear, so that the gel beads are placed in a metal ion solution such as copper ion solution to realize the detection of the manganese-doped zinc sulfide quantum dots/agar complexes on the metal copper ions.
A quantum dot/agar composite prepared by a one-pot method is characterized by comprising the following steps:
1) preparing a manganese-doped zinc sulfide quantum dot/agar compound: adding 0.11-1.1 g of zinc acetate dihydrate into the prepared agar solution, simultaneously adding 0.5-3.8 mL of the prepared manganese acetate solution, magnetically stirring for 20-40 minutes at 90-100 ℃, uniformly mixing the solution, adding 3.3-8 mL of the prepared sodium sulfide solution into the mixed solution, enabling the molar concentration ratio of zinc acetate to manganese acetate in the mixed solution to be 1: 0.05-1: 0.15 and the molar concentration ratio of zinc acetate to sodium sulfide to be 1: 0.5-1: 1, and continuously heating and stirring at 90-100 ℃ for reaction for 30-40 minutes to obtain a manganese-doped zinc sulfide quantum dot/agar compound;
2) preparing a manganese-doped zinc sulfide quantum dot/agar composite gel pellet: 150-200 mL of soybean oil is placed in a refrigerator and cooled to 0-5 ℃, the manganese-doped zinc sulfide quantum dot/agar composite prepared in the step 1) is dropwise added into the soybean oil at the speed of 10-20 drops/minute by using a medical injector, the drops of the manganese-doped zinc sulfide quantum dot/agar composite are completely immersed into the soybean oil, a gel pellet is formed after standing for 30-60 minutes, the gel pellet is taken out and sequentially washed with ethanol and distilled water for 3-6 times, the manganese-doped zinc sulfide quantum dot/agar composite gel pellet is prepared, and the quantum dot/agar composite prepared by a one-pot method (or called as: quantum dot/agar complex with metal ion detection).
According to the technical scheme, the preparation of the agar solution comprises the following steps: adding 0.5-4.5 g of agar powder into a beaker filled with 100-150 mL of distilled water, heating to 90-100 ℃, and stirring for 20-40 minutes to completely dissolve the agar, thereby preparing the agar solution with the mass percentage concentration of 0.5-3%.
According to the technical scheme, the preparation of the sodium sulfide solution comprises the following steps: taking 2.4-7.2 g of sodium sulfide nonahydrate, adding 100-150 mL of distilled water, and magnetically stirring for 15-40 minutes at the temperature of 20-30 ℃ to prepare a sodium sulfide solution with the molar concentration of 0.1-0.3M.
According to the technical scheme, the method is characterized in that the manganese acetate solution is prepared by the following steps: taking 1.225-4.9 g of tetrahydrate manganese acetate, adding 100-150 mL of distilled water, and magnetically stirring for 15-40 minutes at the temperature of 20-30 ℃ to prepare a manganese acetate solution with the molar concentration of 0.05-0.2M.
The method for detecting the metal ions by using the quantum dot/agar composite prepared by the one-pot method is characterized by comprising the following steps of: copper sulfate solutions of different molarity (concentration range of copper sulfate solution is 10)-5M～10-3M) respectively placing the manganese-doped zinc sulfide quantum dots/agar composite gel beads with uniform size prepared in the step 2) into different quartz cuvettes, adding 5-10 beads with the same quantity into each cuvette, and completely immersing the beads into a copper sulfate solution for standing for 5-15 minutes; observing and comparing the fluorescence property change of the manganese-doped zinc sulfide quantum dot/agar composite gel beads before and after adding copper sulfate solutions with different concentrations by using an ultraviolet instrument; then taking the small balls out of the copper sulfate solution, putting the small balls into a clean beaker, heating the small balls to 90-100 ℃, preserving the heat for 20-40 minutes to enable the small balls to be completely converted into a manganese-doped zinc sulfide quantum dot/agar complex solution, and detecting the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar complex solution after the small balls are acted with copper sulfate solutions with different concentrations by using a fluorescence spectrophotometer to obtain a fluorescence emission spectrum; the detection of the manganese-doped zinc sulfide quantum dot/agar composite on the metal copper ions is realized by the detection means.
The technical principle of the invention is that agar is used as a stabilizer in the preparation process of the manganese-doped zinc sulfide quantum dot, and the manganese-doped zinc sulfide quantum dot/agar composite with the metal ion detection function is prepared by adopting a one-pot method which has the advantages of low cost, mild reaction conditions, simple, convenient and fast operation and environmental protection. In addition, the prepared manganese-doped zinc sulfide quantum dot/agar composite has the fluorescence property of the manganese-doped zinc sulfide quantum dot, the fluorescence stability is high at normal temperature, the obtained manganese-doped zinc sulfide quantum dot/agar composite has a good detection effect on the detection of metal copper ions, the detection means is reliable, the detection method is convenient and fast, and the detected manganese-doped zinc sulfide quantum dot/agar composite is easy to separate from a material system to be detected.
The invention has the beneficial effects that:
1) according to the invention, natural polymer agar is used as a stabilizer in the preparation process of the manganese-doped zinc sulfide quantum dots, the reaction conditions in the whole preparation process are mild, the post-treatment process is convenient, other post-treatment processes such as separation and purification are not needed, the manganese-doped zinc sulfide quantum dot/agar compound is directly prepared by a one-step method, and the manganese-doped zinc sulfide quantum dot/agar compound can be directly applied to detection of metal ions.
2) The invention utilizes the agar as an important component of the manganese-doped zinc sulfide quantum dot/agar composite, the agar has good biodegradability, biocompatibility and nontoxicity, and simultaneously has the characteristics of wide source, reproducibility and the like, and in addition, the prepared quantum dot is the nontoxicity manganese-doped zinc sulfide quantum dot, namely, the prepared manganese-doped zinc sulfide quantum dot/agar composite is composed of two nontoxicity components, which is very favorable for the application of the quantum dot/agar composite in the fields of biomedical materials and the like.
3) The manganese-doped zinc sulfide quantum dot/agar composite is prepared by a one-pot method, and the preparation method has the advantages of low cost, mild reaction conditions, simple and quick operation, environmental protection and simple product post-treatment; meanwhile, because toxic chemical stabilizers (such as 3-mercaptopropionic acid and the like) are avoided, the stabilizer prepared by using agar as the manganese-doped zinc sulfide quantum dot meets the requirements of environmental protection and sustainable development.
4) The manganese-doped zinc sulfide quantum dot/agar composite prepared by the invention keeps the fluorescence property of the manganese-doped zinc sulfide quantum dot, has strong fluorescence stability at normal temperature, shows good detection effect on the detection of metal copper ions, has reliable detection means, is easy to separate from an object system to be detected after detection, and has safe and controllable detection process and high detection efficiency.
Drawings
Fig. 1 is a photograph (a) of a manganese-doped zinc sulfide quantum dot/agar composite with a metal ion detection effect prepared in example 2 of the invention under sunlight and a fluorescent photograph (b) under excitation of 302nm ultraviolet light.
FIG. 2 is the UV absorption curve of the Mn-doped Zn sulfide quantum dot/agar composite with metal ion detection function prepared in example 2 of the present invention and the control agar sample.
Fig. 3 is a fluorescent photograph (a) of a manganese-doped zinc sulfide quantum dot/agar composite gel pellet prepared in example 2 of the present invention under 302nm ultraviolet excitation before adding a copper ion solution and a fluorescent photograph (b) under 302nm ultraviolet excitation after adding a copper ion solution.
FIG. 4 is a fluorescence emission spectrum of the manganese-doped zinc sulfide quantum dot/agar composite with metal ion detection function prepared in example 2 of the present invention after the composite is reacted with copper ion solutions of different concentrations.
Detailed Description
The invention is further described below with reference to the following figures and examples, which should not be construed as limiting the invention.
The invention provides a quantum dot/agar composite prepared by a one-pot method and a method for detecting metal ions by using the quantum dot/agar composite, and the invention is further explained by combining specific examples, but the invention is not limited by the examples.
Example 1
A quantum dot/agar composite prepared by a one-pot method comprises the following steps:
1) preparing a manganese-doped zinc sulfide quantum dot/agar compound: taking 0.5g of solid agar powder, adding the solid agar powder into a beaker filled with 100mL of distilled water, heating to 90 ℃, and stirring for 20 minutes to completely dissolve the agar, thereby preparing an agar solution with the mass percentage concentration of 0.5%. 2.4g of sodium sulfide nonahydrate is added into a beaker containing 100mL of distilled water, and the mixture is magnetically stirred for 15 minutes at the temperature of 20 ℃ to prepare a sodium sulfide solution with the molar concentration of 0.1M. Adding 1.225g of tetrahydrate manganese acetate into a beaker filled with 100mL of distilled water, and magnetically stirring for 15 minutes at the temperature of 20 ℃ to prepare a manganese acetate solution with the molar concentration of 0.05M;
adding 0.11g of zinc acetate dihydrate into the prepared agar solution, simultaneously adding 0.5mL of the prepared manganese acetate solution, magnetically stirring the solution for 20 minutes at 90 ℃, uniformly mixing the solution, adding 3.3mL of the prepared sodium sulfide solution into the mixed solution to ensure that the molar concentration ratio of the zinc acetate to the manganese acetate in the mixed solution is 1:0.05 and the molar concentration ratio of the zinc acetate to the sodium sulfide is 1:0.66, and continuously heating, stirring and reacting the mixed solution for 30 minutes at 90 ℃ to prepare the manganese-doped zinc sulfide quantum dot/agar compound;
2) preparing a manganese-doped zinc sulfide quantum dot/agar composite gel pellet: cooling 150mL of soybean oil in a refrigerator to 0 ℃, dropwise adding the manganese-doped zinc sulfide quantum dot/agar composite prepared in the step 1) into the soybean oil by using a medical injector at a speed of 10 drops/minute to completely immerse the drops of the manganese-doped zinc sulfide quantum dot/agar composite in the soybean oil, standing for 30 minutes to form gel beads, taking out the gel beads, and sequentially washing the gel beads with ethanol and distilled water for 3 times to prepare the manganese-doped zinc sulfide quantum dot/agar composite gel beads, thus obtaining the quantum dot/agar composite prepared by a one-pot method.
The method for detecting the metal ions by using the quantum dot/agar composite (the quantum dot/agar composite with the metal ion detection function) prepared by the one-pot method comprises the following steps: copper sulfate solutions of different molarity (concentration range is 10)-5M order of magnitude) are respectively arranged in different quartz cuvettes, the manganese-doped zinc sulfide quantum dot/agar composite gel beads with uniform size obtained by the preparation are added into copper sulfate solution cuvettes with different concentrations, 5 beads with the same quantity are added into each cuvette, and the beads are completely immersed in the copper sulfate solution and stand for 5 minutes; observing and comparing the fluorescence property change of the manganese-doped zinc sulfide quantum dot/agar composite gel beads before and after adding copper sulfate solutions with different concentrations by using an ultraviolet instrument; then taking the small balls out of the copper sulfate solution, putting the small balls into a clean beaker, heating the small balls to 90 ℃, preserving the heat for 20 minutes to ensure that the small balls are completely converted into manganese-doped zinc sulfide quantum dot/agar complex solution, and detecting the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar complex solution after the small balls are acted with copper sulfate solutions with different concentrations by using a fluorescence spectrophotometer to obtain fluorescenceThe emission spectrum.
Example 2
A quantum dot/agar composite prepared by a one-pot method comprises the following steps:
1) preparing a manganese-doped zinc sulfide quantum dot/agar compound: taking 1.0g of solid agar powder, adding the solid agar powder into a beaker filled with 100mL of distilled water, heating to 95 ℃, and stirring for 40 minutes to completely dissolve the agar, thereby preparing an agar solution with the mass percentage concentration of 1%. 7.2g of sodium sulfide nonahydrate is added into a beaker filled with 150mL of distilled water, and the mixture is magnetically stirred for 30 minutes at the temperature of 30 ℃ to prepare a sodium sulfide solution with the molar concentration of 0.2M. Adding 3.675g of tetrahydrate manganese acetate into a beaker filled with 150mL of distilled water, and magnetically stirring for 30 minutes at the temperature of 30 ℃ to prepare a manganese acetate solution with the molar concentration of 0.1M;
adding 0.22g of zinc acetate dihydrate into the prepared agar solution, simultaneously adding 1.0mL of the prepared manganese acetate solution, magnetically stirring the solution at 95 ℃ for 40 minutes to uniformly mix the solution, adding 5mL of the prepared sodium sulfide solution into the mixed solution to ensure that the molar concentration ratio of the zinc acetate to the manganese acetate in the mixed solution is 1:0.1 and the molar concentration ratio of the zinc acetate to the sodium sulfide is 1:1, and continuously heating, stirring and reacting at 95 ℃ for 40 minutes to prepare the manganese-doped zinc sulfide quantum dot/agar compound;
2) preparing a manganese-doped zinc sulfide quantum dot/agar composite gel pellet: cooling 180mL of soybean oil in a refrigerator to 0 ℃, dropwise adding the manganese-doped zinc sulfide quantum dot/agar composite prepared in the step 1) into the soybean oil by using a medical injector at a speed of 15 drops/minute to completely immerse the drops of the manganese-doped zinc sulfide quantum dot/agar composite in the soybean oil, standing for 40 minutes to form gel beads, taking out the gel beads, and sequentially washing the gel beads with ethanol and distilled water for 6 times to prepare the manganese-doped zinc sulfide quantum dot/agar composite gel beads, thus obtaining the quantum dot/agar composite prepared by a one-pot method.
Using quantum dot/agar complexes (with gold) prepared by a one-pot methodQuantum dot/agar complex for ion detection), comprising the following steps: copper sulfate solutions of different molarity (concentration range is 10)-4M order of magnitude) are respectively arranged in different quartz cuvettes, the manganese-doped zinc sulfide quantum dot/agar composite gel beads with uniform size obtained by the preparation are added into copper sulfate solution cuvettes with different concentrations, 8 beads with the same number are added into each cuvette, and the beads are completely immersed in the copper sulfate solution and stand for 10 minutes; observing and comparing the fluorescence property change of the manganese-doped zinc sulfide quantum dot/agar composite gel beads before and after adding copper sulfate solutions with different concentrations by using an ultraviolet instrument; and then taking the small balls out of the copper sulfate solution, putting the small balls into a clean beaker, heating to 95 ℃, preserving the heat for 40 minutes to enable the small balls to be completely converted into manganese-doped zinc sulfide quantum dot/agar complex solution, and detecting the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar complex solution after the small balls are acted with copper sulfate solutions with different concentrations by using a fluorescence spectrophotometer to obtain a fluorescence emission spectrum.
Fig. 1 is a photograph (a) of a manganese-doped zinc sulfide quantum dot/agar composite with a metal ion detection effect prepared in example 2 of the invention under sunlight and a fluorescent photograph (b) under excitation of 302nm ultraviolet light. From fig. 1, it can be found that the manganese-doped zinc sulfide quantum dot/agar composite prepared in step 1) is colorless, transparent and uniform under the sunlight condition; the fluorescence property of the manganese-doped zinc sulfide quantum dot/agar composite is observed by using an ultraviolet instrument, and the result shows that the manganese-doped zinc sulfide quantum dot/agar composite shows very obvious red fluorescence under the excitation of 302nm ultraviolet light, and the results show that the manganese-doped zinc sulfide quantum dot exists in the prepared manganese-doped zinc sulfide quantum dot/agar composite, so that the manganese-doped zinc sulfide quantum dot/agar composite has the fluorescence property of the manganese-doped zinc sulfide quantum dot.
FIG. 2 is the UV absorption curve of the Mn-doped Zn sulfide quantum dot/agar composite with metal ion detection function prepared in example 2 of the present invention and the control agar sample. The specific testing steps are as follows: taking a pure agar solution with the mass percentage concentration of 1% as a control sample, taking 3mL of the agar solution, putting the agar solution into a clean quartz cuvette, putting the quartz cuvette into a cuvette frame of an ultraviolet visible spectrophotometer (UV-2550, SHIMADZU, Japan), scanning to obtain an ultraviolet absorption curve of the agar solution, taking the manganese-doped zinc sulfide quantum dot/agar composite solution prepared in the step 1), and scanning in the same wavelength range to obtain the ultraviolet absorption curve of the manganese-doped zinc sulfide quantum dot/agar composite solution. From fig. 2, it can be found that, compared with the control agar sample, the manganese-doped zinc sulfide quantum dot/agar composite has a very obvious ultraviolet absorption peak near 300nm, and the ultraviolet absorption peak is generated by the manganese-doped zinc sulfide quantum dot, which further indicates that the manganese-doped zinc sulfide quantum dot exists in the manganese-doped zinc sulfide quantum dot/agar composite prepared in step 1).
Fig. 3 is a fluorescent photograph (a) of a manganese-doped zinc sulfide quantum dot/agar composite gel pellet prepared in example 2 of the present invention under 302nm ultraviolet excitation before adding a copper ion solution and a fluorescent photograph (b) under 302nm ultraviolet excitation after adding a copper ion solution. From fig. 3, it can be found that the manganese-doped zinc sulfide quantum dot/agar composite gel beads show very obvious red fluorescence under the excitation of 302nm ultraviolet light before being added into the copper ion solution; when the zinc sulfide quantum dot/agar composite gel pellet is added with a copper ion solution, red fluorescence of the pellet disappears under the excitation of 302nm ultraviolet light; the results show that the fluorescence property of the manganese-doped zinc sulfide quantum dot/agar composite gel pellet is obviously changed after the copper ion solution is added into the manganese-doped zinc sulfide quantum dot/agar composite gel pellet, the copper ion has a quenching effect on the fluorescence of the manganese-doped zinc sulfide quantum dot, and the copper ion can enable the fluorescence of the manganese-doped zinc sulfide quantum dot/agar composite to disappear; therefore, the manganese-doped zinc sulfide quantum dot/agar composite gel pellet is placed in the copper ion solution, the detection of metal copper ions by using the manganese-doped zinc sulfide quantum dot/agar composite can be realized, the detection method is convenient and fast, and the detected manganese-doped zinc sulfide quantum dot/agar composite gel pellet is easy to separate from a system to be detected.
FIG. 4 shows an embodiment of the present invention2 the fluorescence emission spectrum of the manganese-doped zinc sulfide quantum dot/agar composite with the metal ion detection function after the action with copper ion solutions with different concentrations. The specific testing steps are as follows: the concentration is 2x10- 4Putting the copper sulfate solution of M into a clean quartz cuvette, adding the manganese-doped zinc sulfide quantum dot/agar composite gel beads prepared in the step 2) into the cuvette, adding 8 gel beads with uniform size into each cuvette, and completely immersing the beads into the copper sulfate solution for standing for 10 minutes; taking the small balls out of the copper sulfate solution, putting the small balls into a clean beaker, heating to 95 ℃, and preserving heat for 40 minutes to ensure that the small balls are completely converted into a compound solution; 3mL of the complex solution was placed in a clean quartz cuvette, the quartz cuvette was placed in a cuvette holder of a fluorescence spectrophotometer (RF-5301PC, SHIMADZU, Japan) with an excitation wavelength of 300nm, and the detection was performed at 2X10-4The fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar composite solution after the action of the M copper ion solution; then the concentration of the copper sulfate solution is changed to 3x10 in turn-4M、4x10-4M、6x10- 4M、9x10-4And M, repeatedly carrying out the test, and detecting the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar composite solution acted with the copper ion solutions with different concentrations to obtain a fluorescence emission spectrum. From fig. 4, it can be found that, as the concentration of the copper ion solution increases, the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar complex solution decreases, and the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar complex and the concentration of the copper ion solution present a better gradient relationship, which further indicates that the manganese-doped zinc sulfide quantum dot/agar complex can be applied to the detection of metal copper ions and exhibits a good detection effect.
Example 3
A quantum dot/agar composite prepared by a one-pot method comprises the following steps:
1) preparing a manganese-doped zinc sulfide quantum dot/agar compound: adding 4.5g of solid agar powder into a beaker filled with 150mL of distilled water, heating to 100 ℃, and stirring for 40 minutes to completely dissolve the agar, thereby preparing an agar solution with the mass percentage concentration of 3%. 7.2g of sodium sulfide nonahydrate is added into a beaker filled with 100mL of distilled water, and the mixture is magnetically stirred for 40 minutes at the temperature of 30 ℃ to prepare a sodium sulfide solution with the molar concentration of 0.3M. Adding 4.9g of tetrahydrate manganese acetate into a beaker filled with 100mL of distilled water, and magnetically stirring for 40 minutes at the temperature of 30 ℃ to prepare a manganese acetate solution with the molar concentration of 0.2M;
adding 1.1g of zinc acetate dihydrate into the prepared agar solution, adding 3.8mL of the prepared manganese acetate solution, magnetically stirring the solution at 100 ℃ for 40 minutes to uniformly mix the solution, adding 8mL of the prepared sodium sulfide solution into the mixed solution to ensure that the molar concentration ratio of the zinc acetate to the manganese acetate in the mixed solution is 1:0.15 and the molar concentration ratio of the zinc acetate to the sodium sulfide is 1:0.5, and continuously heating and stirring the mixed solution at 100 ℃ for 40 minutes to react to prepare the manganese-doped zinc sulfide quantum dot/agar compound;
2) preparing a manganese-doped zinc sulfide quantum dot/agar composite gel pellet: cooling 200mL of soybean oil in a refrigerator to 5 ℃, dropwise adding the manganese-doped zinc sulfide quantum dot/agar composite prepared in the step 1) into the soybean oil by using a medical injector at a speed of 20 drops/minute to completely immerse the drops of the manganese-doped zinc sulfide quantum dot/agar composite in the soybean oil, standing for 60 minutes to form gel beads, taking out the gel beads, and sequentially washing the gel beads with ethanol and distilled water for 6 times to prepare the manganese-doped zinc sulfide quantum dot/agar composite gel beads, thus obtaining the quantum dot/agar composite prepared by a one-pot method.
The method for detecting the metal ions by using the quantum dot/agar composite (or called quantum dot/agar composite with the metal ion detection function) prepared by the one-pot method comprises the following steps: copper sulfate solutions of different molarities (the concentration of the copper sulfate solution is in the range of 10)-3M order of magnitude) are respectively arranged in different quartz cuvettes, and the manganese-doped zinc sulfide quantum dot/agar composite gel beads with uniform size obtained by the preparation are added into copper sulfate solution cuvettes with different concentrations, wherein each bead isAdding 10 pellets with the same quantity into the cuvette, and completely immersing the pellets in a copper sulfate solution for standing for 15 minutes; observing and comparing the fluorescence property change of the manganese-doped zinc sulfide quantum dot/agar composite gel beads before and after adding copper sulfate solutions with different concentrations by using an ultraviolet instrument; and then taking the small balls out of the copper sulfate solution, putting the small balls into a clean beaker, heating to 100 ℃, preserving the heat for 40 minutes to enable the small balls to be completely converted into manganese-doped zinc sulfide quantum dot/agar complex solution, and detecting the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar complex solution after the small balls are acted with copper sulfate solutions with different concentrations by using a fluorescence spectrophotometer to obtain a fluorescence emission spectrum.
It should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the present invention, which is defined by the claims appended hereto.
Claims (5)
1. The quantum dot/agar composite prepared by adopting a one-pot method is characterized by comprising the following steps:
1) adding 0.11-1.1 g of zinc acetate dihydrate into an agar solution with the mass percentage concentration of 0.5% -3%, simultaneously adding 0.5-3.8 mL of a manganese acetate solution with the molar concentration of 0.05-0.2M, magnetically stirring for 20-40 minutes at 90-100 ℃, uniformly mixing the solutions, adding 3.3-8 mL of a sodium sulfide solution with the molar concentration of 0.1-0.3M into the mixed solution, enabling the molar concentration ratio of zinc acetate to manganese acetate in the mixed solution to be 1: 0.05-1: 0.15 and the molar concentration ratio of zinc acetate to sodium sulfide to be 1: 0.5-1: 1, and continuously heating, stirring and reacting at 90-100 ℃ for 30-40 minutes to prepare the manganese-doped zinc sulfide quantum dot/agar composite;
2) preparing a manganese-doped zinc sulfide quantum dot/agar composite gel pellet: cooling 150-200 mL of soybean oil in a refrigerator to 0-5 ℃, dropwise adding the manganese-doped zinc sulfide quantum dot/agar complex prepared in the step 1) into the soybean oil, completely immersing the liquid drops of the manganese-doped zinc sulfide quantum dot/agar complex in the soybean oil, standing to form gel beads, taking out the gel beads, sequentially cleaning with ethanol and distilled water, and preparing to obtain the manganese-doped zinc sulfide quantum dot/agar complex gel beads, namely the quantum dot/agar complex prepared by a one-pot method.
2. The one-pot quantum dot/agar composite as claimed in claim 1, wherein the agar solution is prepared by: adding 0.5-4.5 g of agar powder into a beaker filled with 100-150 mL of distilled water, heating to 90-100 ℃, and stirring for 20-40 minutes to completely dissolve the agar, thereby preparing the agar solution with the mass percentage concentration of 0.5-3%.
3. The one-pot quantum dot/agar composite as claimed in claim 1, wherein the sodium sulfide solution is prepared by: taking 2.4-7.2 g of sodium sulfide nonahydrate, adding 100-150 mL of distilled water, and magnetically stirring for 15-40 minutes at the temperature of 20-30 ℃ to prepare a sodium sulfide solution with the molar concentration of 0.1-0.3M.
4. The one-pot quantum dot/agar complex of claim 1, wherein the manganese acetate solution is prepared by: taking 1.225-4.9 g of tetrahydrate manganese acetate, adding 100-150 mL of distilled water, and magnetically stirring for 15-40 minutes at the temperature of 20-30 ℃ to prepare a manganese acetate solution with the molar concentration of 0.05-0.2M.
5. The method for detecting metal ions by using the quantum dot/agar composite as claimed in claim 1, which comprises the following steps: respectively placing copper sulfate solutions with different molar concentrations in different quartz cuvettes, wherein the concentration range of the copper sulfate solution is 10-5M～10-3M; adding the manganese-doped zinc sulfide quantum dot/agar composite gel beads into copper sulfate solution cuvettes with different concentrations, and adding 5-10 manganese-doped zinc sulfide quantum dots/agar in the same quantity into each cuvetteCompletely immersing the manganese-doped zinc sulfide quantum dot/agar composite gel pellets in a copper sulfate solution, and standing for 5-15 minutes; observing and comparing the fluorescence property change of the manganese-doped zinc sulfide quantum dot/agar composite gel beads before and after adding copper sulfate solutions with different concentrations by using an ultraviolet instrument; then taking the manganese-doped zinc sulfide quantum dot/agar composite gel beads out of the copper sulfate solution, putting the manganese-doped zinc sulfide quantum dot/agar composite gel beads into a clean beaker, heating to 90-100 ℃, preserving the heat for 20-40 minutes to enable the manganese-doped zinc sulfide quantum dot/agar composite gel beads to be completely converted into manganese-doped zinc sulfide quantum dot/agar composite solution, and detecting the fluorescence intensity of the manganese-doped zinc sulfide quantum dot/agar composite solution after the manganese-doped zinc sulfide quantum dot/agar composite gel beads react with copper sulfate solutions with different concentrations by using a fluorescence spectrophotometer to obtain a fluorescence emission spectrum; the detection of the manganese-doped zinc sulfide quantum dot/agar composite on the metal copper ions is realized by the detection means.
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