Double-heteroatom-regulated polyoxometallate material and preparation method and application thereof
阅读说明：本技术 一种双杂原子调控的多金属氧酸盐材料及制备方法与应用 (Double-heteroatom-regulated polyoxometallate material and preparation method and application thereof ) 是由 刘建彩 赵俊伟 陈利娟 谢赛赛 于 2021-10-21 设计创作，主要内容包括：本发明涉及一种双杂原子调控的多金属氧酸盐材料及其制备方法与应用,其化学式为[H-(2)N(CH-(3))-(2)]-(10)NaH-(9)[Nd-(4)(H-(2)O)-(14)W-(7)O-(15)(H-(2)MA)-(4)][Sb～(III)W-(9)O-(33)]-(2)[HP～(III)Sb～(III)W-(15)O-(54)]-(2)·44H-(2)O。该多金属氧酸盐是通过Na-(9)[B-α-SbW-(9)O-(33)]‧19.5H-(2)O前驱体与二水钨酸钠、盐酸二甲胺、DL-苹果酸、亚磷酸和醋酸钕分步组装反应制备而得,操作简单且成本较低。该多金属氧酸盐与吡咯溶液(PY)通过电聚合作用形成导电薄膜(POM@PPY),随后构建了电化学免疫传感器,实现了对植物生长激素(吲哚乙酸)的检测,并表现出优异的灵敏度、选择性和抗干扰能力。(The invention relates to a polyoxometallate material regulated by double hetero atoms, a preparation method and application thereof, wherein the chemical formula is [ H ] 2 N(CH 3 ) 2 ] 10 NaH 9 [Nd 4 (H 2 O) 14 W 7 O 15 (H 2 MA) 4 ][Sb III W 9 O 33 ] 2 [HP III Sb III W 15 O 54 ] 2 ·44H 2 And O. The polyoxometallate is obtained by reacting Na 9 [B‑ α ‑SbW 9 O 33 ]‧19.5H 2 The O precursor, sodium tungstate dihydrate, dimethylamine hydrochloride, DL-malic acid, phosphorous acid and neodymium acetate are prepared by step-by-step assembly reaction, and the preparation method is simple to operate and low in cost. The polyoxometallate and pyrrole solution (PY) form a conductive film (POM @ PPY) through electropolymerization, and then an electrochemical immunosensor is constructed to realizeThe method detects the plant growth hormone (indoleacetic acid) and shows excellent sensitivity, selectivity and anti-interference capability.)
1. A kind of polyoxometallate material regulated by double hetero atoms has a chemical formula: [ H ]2N(CH3)2]10NaH9[Nd4(H2O)14W7O15(H2MA)4][SbIIIW9O33]2[HPIIISbIIIW15O54]2·44H2O。
2. The method for preparing the double-heteroatom-regulated polyoxometalate material of claim 1, comprising the steps of:
(1) preparation of antimony tungstate precursor Na9[B-α-SbW9O33]∙19.5H2O；
(2) Under the condition of stirring, adding Na9[B-α-SbW9O33]∙19.5H2O, sodium tungstate dihydrate, DL-malic acid, phosphorous acid and saltsDissolving dimethylamine acid into distilled water, adjusting the pH value of a reaction system to 2.80-3.20, stirring for 15-30 min, then adding neodymium acetate, adjusting the pH value of the reaction system to 2.80-3.20 again, continuously stirring for 20-40 min, finally heating in a water bath at 80-95 ℃ for 1.5-2.5 h, taking out, cooling to room temperature, filtering, standing and volatilizing the filtrate at room temperature, and separating out light purple cuboid crystals, namely the polyoxometallate material.
3. The method of preparing the dual heteroatom-regulated polyoxometalate material of claim 2, wherein the Na is9[B-α-SbW9O33]∙19.5H2The molar ratio of O, sodium tungstate dihydrate, DL-malic acid, phosphorous acid, dimethylamine hydrochloride, neodymium acetate and distilled water is 0.3-0.4: 13-16: 2-3: 0.4-0.8: 12-25: 1.0-1.2: 1300-1400.
4. Use of the dual heteroatom-regulated polyoxometalate material of claim 1 in an electrochemical sensor.
5. The electrically conductive film prepared by electropolymerization of the double heteroatom controlled polyoxometallate and the pyrrole according to claim 1, which is prepared by the following steps:
in a solution containing 5mM polyoxometallate and 7mM pyrrole monomers, a glassy carbon electrode is taken as a working electrode, an Ag/AgCl electrode is taken as a reference electrode, and a platinum electrode is taken as an auxiliary electrode respectively by utilizing a chronoamperometry method, a conductive film POM @ PPY is formed on ITO conductive glass by an electropolymerization method under the external field voltage of 0.6-0.7V, and the electropolymerization time is 40-360 s.
6. A method for constructing an electrochemical immunosensor by using the conductive film of claim 5 is characterized by comprising the following specific steps:
1) polishing a glassy carbon electrode smoothly, preparing a POM @ PPY film on the glassy carbon electrode by an electropolymerization method, and constructing a POM @ PPY/GCE sensor;
2) cleaning POM @ PPY/GCE, and thenSoaking in a solution containing 0.01M KNO30.10 g ∙ L−1 HAuCl4∙3H2In the O solution, the fixed voltage is-0.2V, the working time is 20-120 s, and therefore the Au/POM @ PPY/GCE electrode is prepared by electrodepositing the gold nanoparticles on the POM @ PPY/GCE;
3) dripping 10 mu L of 0.01 mg/mL indoleacetic acid antibody on the surface of an Au/POM @ PPY/GCE electrode, and standing at room temperature for 1-5h to form Anti-IAA/Au/POM @ PPY/GCE of the electrochemical immunosensor; after being cleaned by high-purity water, the volume is 16 mu L0.01 mg mL−1Soaking in bovine serum albumin for 15-30 min.
7. The electrochemical immunosensor produced by the method of claim 6.
8. Use of the electrochemical immunosensor of claim 7 for detecting the auxin in indoleacetic acid.
Technical Field
The invention belongs to the technical field of preparation of polyoxometallate chemical materials, and particularly relates to a polyoxometallate material regulated by double heteroatoms, a preparation method and application of the polyoxometallate material in the aspect of electrochemical immunosensing.
Background
Metal oxide cluster materialMaterials have attracted considerable attention in material science and crystal engineering because of their unique physicochemical properties (see k. Yonesato, s. Yamazoe, s. Yokogawa, et al,Angew. Chem. Int. Ed. 2021, 60, 16994−16998；N. Li, Y. X. Shang, R. Xu, et al, J. Am. Chem. Soc. 2019, 141, 17968-17972). Polyoxometallate, as a representative metal oxide cluster, has abundant chemical compositions and structural types, unique electronic configurations, and excellent redox activity, and thus is widely used in the fields of catalysis, magnetism, medicine, electrochemistry, energy storage, and the like, and is gradually becoming one of research hotspots of chemistry and material chemistry (see w.j. Luo, j. Hu, h.l. Diao, et al,Angew. Chem. Int. Ed. 2017, 56, 4941−4944；L. G. Gong, W. Q. Ding, Y. Chen, et al, Angew. Chem. Int. Ed. 2021, 60, 21449-21456). The central heteroatom is an important component of polyoxometallate, and the electronic structural characteristics of the central heteroatom play an important role in the structural framework of the polyoxometallate and the properties of the central heteroatom, such as stability, oxidizing capability, acidity and the like. Considering that different heteroatoms carry different functional characteristics, the introduction of different heteroatoms into the same reaction system is expected to prepare more complicated and interesting novel functional materials, so researchers gradually look at the polyoxometallate with single heteroatom participation to the polyoxometallate with double heteroatom participation. For example, in 2017, the task group of auspicious construction of holes reported a novel example, which also contains { SbW9} and { PW9Two kinds of polyoxometallate cluster [ Ln ] of construction units3NiII 9(μ 3-OH)9(SbW9O33)2(PW9O34)3(CH3COO)3]30–(J. Cai, X. Y. Zheng, J. Xie, et al, Inorg. Chem. 2017, 56, 8439-8445). In 2021, an example of AsO was reported in Yangkou Yi subject group4Bridged, hexadecarycyclic nickel substituted silicotungstates [ (AsO)4){Ni8(OH)6(H2O)2(CO3)2(A-α-SiW9O34)2}2]31− (C. Lian, H.-L. Li, G.-Y. Yang, Inorg. Chem. 2021, 60, 3996-4003). However, at present, few novel polyoxometallate materials related to the synergistic assembly of double heteroatoms and simultaneously participating in the construction of the same building unit have been reported, which is mainly caused by the difference of the reactivity and the coordination bonding capability of two heteroatoms in the same reaction system. Therefore, two kinds of hetero atoms Sb with matched atom radius sizes and having lone pair and lone pair-like electron effects are selectedШAnd PШAnd combining, wherein the reaction dosage of the two is regulated and controlled, and the space electron arrangement effect of the two is fully utilized, so that the tungstate is driven to be assembled in a synergic manner to form an open type heteropolyoxometallate fragment carrying high negative charges, more rare earth cations are attracted to be embedded into a target structure, and the development bottleneck in the field is broken through.
Polyoxometallate has abundant redox centers, can undergo a rapid and reversible multi-electron transfer process, and the structure of the polyoxometallate is kept unchanged in the process of getting and losing electrons, so that polyoxometallate has excellent electrochemical performance and is widely applied to preparation of abundant novel electrochemical functional materials (T. Wei, Y. Chen, W. Tu, et al,Chem. Commun. 2014, 50, 9357–9360；D. Zhu, D. X. Guo, L. L. Zhang, et al, Sens. Actuators B Chem. 2019, 281, 893-904). The electrochemical detection technology has the advantages of simple operation, high sensitivity, fast response, low cost, short analysis period, easy miniaturization and the like, thereby arousing the extensive attention of researchers (l. Lu,Biosens. Bioelectron. 2018, 110, 180-192). PdNPs @ PW is prepared by Zhangyufan subject group in 201912the/NHCS ternary composite material (NP stands for nano particles, NHCSs stands for nitrogen-doped hollow carbon spheres) is modified on a glassy carbon electrode to construct an electrochemical sensor, and acetaminophen shows a wider linear range, a lower detection limit (3 nM) and excellent anti-interference capability (L, Wang, T.J. Meng, J.J. Sun, et al,Anal. Chim. Acta 2019, 1047, 28-35). However, the current research on the electrochemical sensing performance of polyoxometallate is mainly focused on the small-size or single-heteroatom-involved polytungstic acidOn the salt material, no research report about the polyoxometallate rare earth derivative material regulated by double hetero atoms and the electrochemical immunity sensing performance thereof is found.
Disclosure of Invention
The invention aims to overcome the problems in the prior art, provides a polyoxometallate material regulated by double hetero atoms, simultaneously compounds the polyoxometallate material with pyrrole to prepare a conductive film POM @ PPY, and evaluates the application of the synthesized film in the aspect of electrochemical sensing. The electrochemical immunosensor constructed by the film has excellent sensitivity, selectivity and anti-interference capability on detection of indoleacetic acid (IAA), and provides a new idea for promoting the polyoxometallate material to be applied to detection of auxin in the field of botany.
The invention also provides a preparation method of the polyoxometallate material regulated and controlled by the double hetero atoms and electrochemical sensing performance research.
In order to achieve the purpose, the invention adopts the following technical scheme:
a kind of polyoxometallate material regulated by double hetero atoms has a chemical formula: [ H ]2N(CH3)2]10NaH9[Nd4(H2O)14W7O15(H2MA)4][SbIIIW9O33]2[HPIIISbIIIW15O54]2·44H2O (POM, H for short)3MA = DL-malic acid), belonging to the monoclinic system,P2/nspace group, cell parameter ofa = 30.1465(8) Å，b = 35.4265(12) Å，c = 34.1200(9) Å，α = γ = 90.00º，β = 96.4110(10)º，V = 36211.8 Å3。H4MA represents DL malic acid.
The polyoxometallate material regulated by the double hetero atoms is obtained by adopting a step-by-step assembly method, and the specific preparation method comprises the following steps:
(1) preparation of antimony tungstate precursor Na9[B-α-SbW9O33]∙19.5H2O; synthesis of precursors according to literature reported methodsNa9[B-α-SbW9O33]·19.5H2O (see in particular literature (baby, m.; los, i.; Pohlmann, h.; Krebs, B).Chem. Eur. J. 1997, 3, 1232−1237)；
(2) Under the condition of stirring, adding Na9[B-α-SbW9O33]∙19.5H2Dissolving O, sodium tungstate dihydrate, DL-malic acid, phosphorous acid and dimethylamine hydrochloride into distilled water, adjusting pH of the reaction system to 2.80-3.20, stirring for 15-30 min, and adding Nd (CH) acetate3COO)3And regulating the pH value of the reaction system to 2.80-3.20 again, continuously stirring for 20-40 min, finally placing the reaction mixture in a water bath at the temperature of 80-95 ℃ to heat for 1.5-2.5 h, taking out, cooling to room temperature, filtering, standing the filtrate at room temperature, slowly volatilizing, and separating out light purple cuboid crystals after about one week to obtain the target product polyoxometallate material.
Specifically, the Na9[B-α-SbW9O33]∙19.5H2The molar ratio of O, sodium tungstate dihydrate, DL-malic acid, phosphorous acid, dimethylamine hydrochloride, neodymium acetate and distilled water is 0.3-0.4: 13-16: 2-3: 0.4-0.8: 12-25: 1.0-1.2: 1300-1400.
The invention also provides the application of the polyoxometallate material regulated and controlled by the double hetero atoms in an electrochemical sensor. The application is further characterized in that the conductive film formed by electropolymerization of the polyoxometallate material regulated by the double heteroatoms and pyrrole is used for preparing the electrochemical sensor for detecting the plant growth hormone indoleacetic acid, and the electrochemical sensor shows excellent sensitivity, selectivity and anti-interference capability.
The invention provides a conductive film (POM @ PPY) prepared by electropolymerization of Polyoxometallate (POM) and Pyrrole (PY) regulated and controlled by double heteroatoms, which is prepared by the following steps:
in a solution containing 5mM Polyoxometallate (POM) and 7mM Pyrrole (PY) monomers, a conductive film POM @ PPY is formed on ITO conductive glass by an electropolymerization method under an external field voltage of 0.6-0.7V by using a chronoamperometry method and respectively using a Glassy Carbon Electrode (GCE) as a working electrode, an Ag/AgCl electrode as a reference electrode and a platinum electrode as an auxiliary electrode, wherein the electropolymerization time is 40-360 s.
The invention also provides a method for constructing an electrochemical immunosensor by using the conductive film (POM @ PPY), which comprises the following specific steps:
1) polishing a glassy carbon electrode smoothly, preparing a POM @ PPY film on the glassy carbon electrode by an electropolymerization method, and constructing a POM @ PPY/GCE sensor;
2) cleaning POM @ PPY/GCE with high purity water, and soaking in a solution containing 0.01M KNO30.10 g ∙ L−1HAuCl4∙3H2In the O solution, the fixed voltage is-0.2V, the working time is 20-120 s, and therefore the Au/POM @ PPY/GCE electrode is prepared by electrodepositing the gold nanoparticles on the POM @ PPY/GCE;
3) dripping 10 mu L of 0.01 mg/mL indoleacetic acid antibody (Anti-IAA) on the surface of an Au/POM @ PPY/GCE electrode, standing at room temperature for 1, 2, 3, 4 and 5 hours to attach the indoleacetic acid antibody on the surface of the Au/POM @ PPY/GCE electrode through Au-S bond interaction to form an Anti-IAA/Au/POM PPy/GCE electrochemical immunosensor; after being cleaned by high-purity water, the volume is 16 mu L0.01 mg mL−1Soaking in Bovine Serum Albumin (BSA) for 15-30 min to remove non-specifically bound indoleacetic acid antibody.
The invention provides an electrochemical immunosensor constructed by the method.
The invention also provides application of the electrochemical immunosensor in detecting the plant growth hormone indoleacetic acid.
The invention adopts a step-by-step assembly method, and sodium tungstate dihydrate and Na are regulated and controlled under the condition that organic solubilizers of dimethylamine hydrochloride and DL-malic acid exist9[B-α-SbW9O33]·19.5H2O precursor, phosphorous acid and Nd (CH)3COO)3Obtaining the polyoxometallate material regulated by the double hetero atoms according to the molar ratio of the reaction raw materials and the pH value of the reaction system. Two kinds of hetero atoms SbШAnd PШHas electron and lone pair-like electron effect, is favorable for constructing vacancy polyoxometallate fragments exposing more oxygen coordination sites, andmore oxophilic components (e.g., rare earth or tungsten centers) undergo coordination assembly. Different heteroatoms have different reactivity and coordination bonding capability in the same reaction system, and the purpose of embedding the heteroatoms into the polyoxometallate material at the same time is achieved by regulating the dosage of two heteroatom components and heating to improve the reactivity. Further, by preparing Na beforehand9[B-α-SbW9O33]·19.5H2The O precursor is reacted with phosphorous acid to reduce the competition of the two hetero atoms. The organic ligand DL-malic acid can be subjected to coordination assembly with rare earth, can effectively prevent rare earth ions from hydrolyzing, and can be used as a bridging unit of polyoxometallate fragments to construct a large cluster structure. According to researches, the polyoxometallate material regulated and controlled by the double hetero atoms can be used for preparing a conductive film with pyrrole through electropolymerization, so that an electrochemical immunosensor is further constructed, and excellent electrochemical performance is shown in the detection of the plant growth hormone indoleacetic acid.
The invention provides a preparation method of a polyoxometallate material regulated by double hetero atoms and electrochemical immunosensing performance research thereof, compared with the prior art, the invention has the following advantages:
1) the polyoxometallate material regulated by the double heteroatoms provided by the invention is a first example of a Sb/P polyoxometallate material regulated by the double heteroatoms, and the molecular structure of the polyoxometallate material can be accurately determined by an X-ray single crystal diffraction technology;
2) the polyoxometallate material regulated by the double hetero atoms adopts a step-by-step assembly method, and the synthesis method is simple and convenient to operate;
3) the electrochemical sensor constructed by the polyoxometallate material regulated by the double hetero atoms provided by the invention has excellent sensitivity, selectivity and anti-interference capability in the detection of indoleacetic acid, and has potential application value in the aspect of detecting the plant growth hormone by utilizing electrochemistry.
Drawings
FIG. 1 shows a molecular structure unit diagram of the target material (a) and a multi-metal cluster [ Ln ] modified with DL-malic acid (b)4(H2O)14W7O15(H2MA)4]20+And (c) is [ Ln4(H2O)14W7O15(H2MA)4]20+(d) - (e) are the skeletal structure and complete { W } of the target material after removal of DL-malic acid7Nd4Metal cluster, (f) is 'fish' shaped Nd2W3Unit, (g) is { HP }IIISbW15And { SbW }9Fragment is passed through { Nd }2W3Are connected to form [ Nd ]2(H2O)7W3O15][SbIIIW9O33][HPIIISbIIIW15O54]24−Dimeric units, (h) Nd 2-W29-Nd 3 bridging units, (i) removal of DL-malic acid and Nd for the target material3+The four-cluster structure after ion, (j) - (k) are Nd3+The coordination configuration of the ion;
FIG. 2 shows (a) an infrared spectrum of a target material and (b) a thermogravimetric plot of the target material;
FIG. 3 is an X-ray powder diffraction pattern of a target material;
FIG. 4 is (a) a schematic diagram showing the preparation of a POM @ PPY film, (b) a DPV curve of the POM @ PPY/GCE at a time of no-electropolymerization, (c) - (d) SEM and cross-sectional SEM images of the POM @ PPY film, (e) an AFM image of the POM @ PPY film, and (f) a three-dimensional AFM image of the POM @ PPY film;
FIG. 5 shows (a) IR images of POM, PY, and POM @ PPY films, and (b) Raman images of POM, PY, and POM @ PPY films;
FIG. 6 shows XPS survey spectra for (a) POM @ PPY film and (b) - (d) for W4f, C1s, and N1s in POM @ PPY film;
FIG. 7 is a schematic diagram of a construction process of a POM @ PPY-based electrochemical immunosensor;
FIG. 8 shows (a) DPV curves of Au/POM @ PPY/GCE at different gold deposition times, (b) SEM images of Au/POM @ PPY films, and (c) AFM images and corresponding three-dimensional images of Au/POM @ PPY films;
FIG. 9 (a) shows DPV curves obtained by anti-IAA/Au/POM @ PPY/GCE under the condition of changing the incubation time of an indoleacetic acid antibody, (b) shows DPV curves of electrodes modified by different materials, and in the graph b, a bare electrode (A), POM @ PPY/GCE (B), Au/POM @ PPY/GCEs (C), anti-IAA/Au/POM @ PPY/GCE (D) and IAA/Au/POM @ PPY/GCE (E);
FIGS. 10 (a) - (b) are DPV curves obtained by POM @ PPY film based electrochemical immunosensor at different concentrations of indoleacetic acid, and their corresponding peak current changes (. DELTA.I) Linear relation curve with indoleacetic acid concentration, wherein (c) - (d) are DPV curves of the electrochemical immunosensor based on the POM @ PPY film when different biomolecules are detected and corresponding peak current change (delta)I) Curves, (e) - (f) are DPV curves obtained when an electrochemical immunosensor based on the POM @ PPY film detects indoleacetic acid in the presence of different interfering substances, and corresponding peak current change (delta)I) A curve;
FIG. 11 shows (a) DPV curves for six sets of IAA/anti-IAA/Au/POM @ PPY/GCEs, and (b) stability test for POM @ PPY/GCEs over time.
Detailed description of the invention
The present invention is further illustrated by the following specific examples, but the scope of the invention is not limited thereto.
Example 1:
a kind of polyoxometallate material regulated by double hetero atoms has a chemical formula: [ H ]2N(CH3)2]10NaH9[Nd4(H2O)14 W7O15(H2MA)4][SbIIIW9O33]2[HPIIISbIIIW15O54]2·44H2O。
The polyoxometallate material regulated and controlled by the double hetero atoms is obtained by adopting a step-by-step assembly method, and the specific preparation method relates to the following steps:
1) synthesizing precursor Na according to the conventional method in the field9[B-α-SbW9O33]·19.5H2O (see in particular references: m. B, i. los, h. Pohlmann, et al,Chem. Eur. J. 1997, 3, 1232−1237)；
2) under the condition of stirring, adding Na9[B-α-SbW9O33]·19.5H2O (1.000 g, 0.350 mmol), sodium tungstate dihydrate (5.000 g, 15.159 mmol), DL-malic acid (0.400 g, 2.983 mmol), phosphorous acid (0.040 g, 0.488 mmol) and dimethylamine hydrochloride (1.750 g, 21.472 mmol) were added to 25 mL of distilled water, stirred and dissolved uniformly, and then 6 mol. L. –1HCl adjusted the reaction pH to 3.00. After stirring for 20 min, Nd (CH) was added3COO)3(0.350 g, 1.104 mmol), followed by 6 mol. L –1HCl controls the final pH of the reaction system at 3.00. And continuously stirring for 30 min, heating the reaction mixture in a water bath kettle at 90 ℃, taking out after 2 h, cooling to room temperature, filtering, standing the filtrate at room temperature, slowly volatilizing, and precipitating light purple cuboid crystals after about one week to obtain the target product polyoxometallate material.
Example 2:
a kind of polyoxometallate material regulated by double hetero atoms has a chemical formula: [ H ]2N(CH3)2]10NaH9[Nd4(H2O)14 W7O15(H2MA)4][SbIIIW9O33]2[HPIIISbIIIW15O54]2·44H2O。
The polyoxometallate material regulated and controlled by the double hetero atoms is obtained by adopting a step-by-step assembly method, and the specific preparation method relates to the following steps:
1) synthesizing precursor Na according to the conventional method in the field9[B-α-SbW9O33]·19.5H2O (see in particular references: m. B, i. los, h. Pohlmann, et al,Chem. Eur. J. 1997, 3, 1232−1237)；
2) under the condition of stirring, adding Na9[B-α-SbW9O33]·19.5H2O (1.000 g, 0.350 mmol), sodium tungstate dihydrate (4.500 g, 13.643 mmol), DL-malic acid (0.400 g, 2.983 mmol), phosphorous acid (0.040 g, 0.488 mmol) and dimethylamine hydrochloride (1.750 g, 21.472 mmol) were dissolved in 25 mL of distilled water, and after stirring well, the solution was diluted with 6 mol. L –1HCl adjusted the reaction pH to 3.20. Stirring for 20 minAdding Nd (CH)3COO)3(0.350 g, 1.104 mmol), followed by 6 mol. L –1HCl controls the final pH of the reaction system at 3.20. And continuously stirring for 30 min, heating the reaction mixture in a water bath kettle at 90 ℃, taking out after 2 h, cooling to room temperature, filtering, standing the filtrate at room temperature, slowly volatilizing, and precipitating light purple cuboid crystals after about one week to obtain the target product polyoxometallate material.
Example 3:
a kind of polyoxometallate material regulated by double hetero atoms has a chemical formula: [ H ]2N(CH3)2]10NaH9[Nd4(H2O)14 W7O15(H2MA)4][SbIIIW9O33]2[HPIIISbIIIW15O54]2·44H2O。
The polyoxometallate material regulated and controlled by the double hetero atoms is obtained by adopting a step-by-step assembly method, and the specific preparation method relates to the following steps:
1) synthesizing precursor Na according to the conventional method in the field9[B-α-SbW9O33]·19.5H2O (see in particular references: m. B, i. los, h. Pohlmann, et al,Chem. Eur. J. 1997, 3, 1232−1237)；
2) under the condition of stirring, adding Na9[B-α-SbW9O33]·19.5H2O (1.000 g, 0.350 mmol), sodium tungstate dihydrate (5.000 g, 15.159 mmol), DL-malic acid (0.300 g, 2.237 mmol), phosphorous acid (0.055 g, 0.671 mmol) and dimethylamine hydrochloride (1.500 g, 18.395 mmol) were dissolved in 25 mL of distilled water, and after stirring well, the solution was diluted with 6 mol. L –1HCl adjusted the reaction pH to 3.00. After stirring for 20 min, Nd (CH) was added3COO)3(0.350 g, 1.104 mmol), followed by 6 mol. L –1HCl controls the final pH of the reaction system at 3.00. Continuously stirring for 30 min, heating the reaction mixture in a water bath kettle at 90 deg.C for 2 hr, cooling to room temperature, filtering, standing the filtrate at room temperature,slowly volatilizes, and light purple cuboid crystals are separated out after about one week, namely the target product polyoxometallate material.
The invention determines and characterizes the crystal structure of the target polyoxometallate material prepared by the embodiment, and the crystal structure is as follows:
target product Material [ H2N(CH3)2]10NaH9[Nd4(H2O)14W7O15(H2MA)4][SbIIIW9O33]2[HPIIISbIIIW15 O54]2·44H2O, belonging to the monoclinic system,P2/nspace group, cell parameter ofa = 30.1465(8) Å，b= 35.4265(12) Å，c = 34.1200(9) Å，α = γ = 90.00º，β = 96.4110(10)º，V = 36211.8 Å3，ZAnd = 4. Its molecular structure unit is three-vacancy Dawson-type [ HP ] with two completely new double hetero atoms embeddedIIISbW15O54]11− ({HPIIISbW15}) fragment and two three-vacancy Keggin-type [ B-α-SbW9O33]9− ({SbW9}) fragments were passed through a polymetallic cluster [ Ln4(H2O)14W7O15(H2MA)4]20+Are connected (a-c in figure 1). DL-malic acid plays a role in modifying the overall framework structure, and after the ligand is removed, the skeleton of the target material and the polynuclear metal cluster [ Nd ]4(H2O)14W7O15]16+ ({W7Nd4}) remain (d-e in fig. 1). Of the "sailboat" type W7Nd4The fragment can be divided into two Nd segments in the shape of a "fish2W3A unit bridging adjacent HP's simultaneouslyIIISbW15And { SbW }9Fragment formation of dimeric [ Nd }2(H2O)7W3O15][SbIIIW9O33][HPIIISbIIIW15O54]24−And the unit is further bridged by W29 and Nd 2-W29-Nd 3 to complete the assembly of the whole frame of the target material (f-h in FIG. 1). Interestingly, when four Nd were removed3+When ionic, { HPIIISbW15And { SbW }9The fragments can still be connected into a four-membered structure (i in FIG. 1) by the atoms W18, W29 and W9. Furthermore, an octadentate Nd13+And Nd43+Ion, and nine-coordinate Nd23+And Nd33+The ions exhibited twisted trigonal bipyramid and single-cap tetragonal anti-prism configurations (j-k in fig. 1), respectively.
The present invention analyzes the infrared spectrum (a in fig. 2), the thermogravimetric curve (b in fig. 2) and the X-ray powder diffraction (3 in fig. 2) of the target material. As shown in a in FIG. 2, the infrared spectrum thereof is 1000-600 cm in the low wave number region–1Four characteristic peaks 944, 877, 767 and 712 cm are present in the range–1Respectively belong to the target material { SbW9And { HP }IIISbW15W-O of fragmentt、W−Ob、W−OcAnd Sb-OaAsymmetric stretching vibration of the key. At 1063 cm–1The absorption peak at (1) corresponds to { HPIIISbW15Stretching vibration of the P-O bond in the fragment. Crystal water and coordinated waterν(H-O) stretching and bending vibration occurred at 3436 cm–1And 1627 cm–1Location. At 1381-–1Several absorption peaks in the range occur corresponding to symmetric and asymmetric stretching vibrations of the carboxylic acid groups in the DL-malic acid. Furthermore, 3148 and 2783 cm–1The vibration peaks at (A) respectively correspond to the protonated dimethylamine hydrochloride cationν(N-H) andν(C-H) absorption peak. B in fig. 2 shows that the target material underwent a three-step weight loss process, with a first step weight loss of 4.91% (theoretical 4.93%) from 35-200 ℃, due to the loss of 44 crystalline water molecules; the second step lost 9.05% weight from 200-800 deg.C (8.41% theoretical) due to 10 protonated dimethylamine cations, 4H2MA–Ligand, 14 coordinated water molecules and 9 protons H+And (4) dehydrating. Upon continued heating to 1000 ℃, the framework of the target material collapsed with sublimation of tungsten oxide. FIG. 3 shows the target materialThe experimental spectrum obtained by X-ray powder diffraction analysis is basically consistent with the theoretical spectrum of single crystal diffraction analysis, which indicates that the synthesized sample is pure.
Example 4:
the invention provides a conductive film (POM @ PPY) prepared by electropolymerization of Polyoxometallate (POM) and Pyrrole (PY) regulated and controlled by double heteroatoms, which is prepared by the following steps:
in a solution containing 5mM Polyoxometallate (POM) and 7mM Pyrrole (PY) monomers, a conductive film POM PPY is formed on ITO conductive glass by an electropolymerization method under an external field voltage of 0.65V by using a Glassy Carbon Electrode (GCE) as a working electrode, an Ag/AgCl electrode as a reference electrode and a platinum electrode as an auxiliary electrode respectively by a chronoamperometry, and the electropolymerization time is 40-360 s.
The obtained target polyoxometalate material and pyrrole form a uniform and stable POM @ PPY conductive film through electropolymerization (a in figure 4), and the optimal electropolymerization time is determined to be 240 s through Differential Pulse Voltammetry (DPV) (b in figure 4). The method is further characterized by means of a field emission Scanning Electron Microscope (SEM), a cross-section SEM, an Atomic Force Microscope (AFM), an infrared spectrum (IR), a Raman spectrum (Raman) and an X-ray photoelectron spectroscopy (XPS), and is specifically described as follows:
the films formed at different deposition times were imaged using SEM and cross-sectional scanning electron microscopy, and the results showed that the formed films failed to completely cover the substrate when the electropolymerization time was 120 s. The morphology of the film was clear and flat as electropolymerization time was increased to 240 s (c-d in FIG. 4). When the electropolymerization time was extended to 360 s, the film cracked. The optimal electropolymerization time was therefore determined to be 240 s, which also coincides with the DPV test results. The AFM results showed a roughness of 7.808 nm (e-f in FIG. 4) for the POM @ PPY film.
Successful recombination of POM @ PPY was further confirmed by IR spectroscopy. The infrared spectrum of POM @ PPY includes both POM (934.20, 871.30, 770.30 and 695.17 cm)–1) And PY (1397.23, 1052.57 and 734.63 cm–1) Indicating successful binding of the target polyoxometalate and pyrrole (fig. 5 a). Likewise, Raman spectrum showed POM @ PPY as wellIt contains POM (813.08, 976.21 and 1406.85 cm)–1) And PY (1145.75 and 1370.16 cm)–1) Further evidence of the above conclusion. In addition, electrostatic interaction between the two causes the POM characteristic peak to shift to a high wavenumber range. XPS spectrum shows that the W binding energy of POM @ PPY is respectively 35.45 eV (W4 f)7/2) And 37.56 eV (W4 f)5/2) The binding energies of C1s are at 284.7 eV (C-C), 286.1 eV (C = N or C-N), respectively+) 287.7 eV (C = O), and N1s binding energies were at 401.6 eV (C-N) and 399.8 eV (C = N-C), respectively (FIG. 6), demonstrating the successful binding of polyoxometallate and pyrrole together.
Example 5:
the invention also provides a method for constructing an electrochemical immunosensor by using the conductive film (POM @ PPY), which comprises the following specific steps:
1) polishing a glassy carbon electrode smoothly, preparing a POM @ PPY film on the glassy carbon electrode by an electropolymerization method, and constructing a POM @ PPY/GCE sensor;
2) cleaning POM @ PPY/GCE with high purity water, and soaking in a solution containing 0.01M KNO30.10 g ∙ L−1HAuCl4∙3H2In the O solution, the fixed voltage is-0.2V, the working time is 20-120 s, and therefore the Au/POM @ PPY/GCE electrode is prepared by electrodepositing the gold nanoparticles on the POM @ PPY/GCE;
3) dripping 10 mu L of 0.01 mg/mL indoleacetic acid antibody (Anti-IAA) on the surface of an Au/POM @ PPY/GCE electrode, standing at room temperature for 1, 2, 3, 4 and 5 hours to attach the indoleacetic acid antibody on the surface of the Au/POM @ PPY/GCE electrode through Au-S bond interaction to form an Anti-IAA/Au/POM PPy/GCE electrochemical immunosensor; after being cleaned by high-purity water, the volume is 16 mu L0.01 mg mL−1Soaking in Bovine Serum Albumin (BSA) for 20 min to remove non-specifically bound indoleacetic acid antibody.
The stability of POM @ PPY/GCE is evaluated by means of a DPV test. The current signal intensity of the bare electrode decreased significantly within one hour. In contrast, the current signal intensity of the POM @ PPY/GCE is only reduced by 2.72% when the POM @ PPY/GCE is kept in a dark environment at room temperature for 21 days, which indicates that a firm film can provide active protection for an electrode, so that the POM @ PPY/GCE has wider application in multiple fields.
Indoleacetic acid is one of the most common natural plant growth hormones, however, too high a level of indoleacetic acid inhibits plant growth and even kills them. The electrochemical sensor for detecting the indoleacetic acid has the advantages of simplicity, rapidness, sensitivity and the like. And the POM @ PPY/GCE can be used as a very promising electrochemical platform for immunoassay of the indoleacetic acid due to good conductivity and stability. In view of the above, we construct an electrochemical immunosensor anti-IAA/Au/POM @ PPY/GCE by attaching an indoleacetic acid antibody (anti-IAA) to the surface of an electrode deposited with gold nanoparticles, and use the electrochemical immunosensor as a probe to specifically capture target indoleacetic acid. The DPV peak current intensity will vary with the concentration of indoleacetic acid as the final detection signal (see FIG. 7 for the construction process).
The invention determines the optimal gold precipitation time to be 80 s when Au/POM @ PPY/GCEs are prepared by electrodepositing gold nano-particles on the surface of an electrode film through a DPV test, and the current signal intensity under the time is the maximum (a in figure 8). SEM shows that gold nanoparticles (approximately 60.12 nm in size) are uniformly dispersed on the surface of the POM @ PPY thin film (b in FIG. 8), providing a good platform for the attachment of the indoleacetic acid antibody to Au/POM @ PPY/GCEs. AFM results showed a roughness of 7.811 nm for Au/POM @ PPY (c in FIG. 8).
The invention researches the performance of an electrochemical immunosensor anti-IAA/Au/POM @ PPY/GCE constructed by POM @ PPY for identifying and detecting indoleacetic acid. The effect of the incubation time of the indolylacetic acid antibody drop on the Au/POM @ PPY/GCE surface on the current signal was first explored by the DPV assay. With prolonged incubation time, the DPV signal gradually decreased, probably due to steric effects of the antibody preventing electron transfer. When the time exceeded 3 h, the DPV signal gradually plateaued indicating that the antibody attached to the electrode surface reached a state of saturation (a in fig. 9). Therefore, the optimal incubation time for immobilizing the antibody on the electrode surface in the subsequent experiments was determined to be 3 h. Subsequently, the feasibility of detecting indoleacetic acid with different modified electrodes was explored. Relative to a bare electrode, POM @ PPY/GCE, Au/POM @ PPY/GCEs, anti-IAA/Au/POM @ PPY/GCE and IAA/Au/POM @ PPY/GCE are used for obtaining DPV (DPV) kojiThe peak current intensity of the wire is significantly enhanced. The introduction of the gold nanoparticles with excellent electron transfer capacity, high dispersibility and high specific surface area enables the current signal intensity of Au/POM @ PPY/GCEs to be obviously superior to that of POM @ PPY/GCE. However, when the antigen is immobilized on the electrode surface, the conductivity of anti-IAA/Au/POM @ PPY/GCE is reduced mainly due to the electronegative indoleacetic acid antibody molecule and electronegative [ Fe (CN)6]3−/4−The electrostatic repulsion between the solutions reduces to some extent the electron transfer from the solution to the electrode surface (b in fig. 9). In addition, the electronegative indoleacetic acid also has the capability of blocking electron transfer, so that when the indoleacetic acid is combined with anti-IAA/Au/POM @ PPY/GCE through an immune reaction, the current intensity of the indoleacetic acid is continuously reduced, and a basis is provided for realizing the detection of the indoleacetic acid.
Under the optimal conditions, a series of indoleacetic acid with different concentrations is detected by using a designed electrochemical immunosensor based on a POM @ PPY film. With increasing concentration of indoleacetic acid from 0, 100, 1000, 5000, 10000, 50000 to 1X 105 pg·mL−1The DPV peak current signal strength gradually decreases (a in fig. 10); and found a DPV peak current change (. DELTA.)I) Linear relationship (delta) to indoleacetic acid concentrationI = I 0 – I，I 0AndIrespectively representing DPV peak current intensity of the electrochemical immunosensor before and after detecting the indoleacetic acid), and the linear fitting equation is deltaI (μA) = 29.70 logC − 51.59 (R 2= 0.9971) (b in fig. 10), and the limit of detection (LOD) was 87.41 pg · mL−1。
To search for the specificity of this immunosensor, the selectivity was examined using abscisic acid (ABA), Salicylic Acid (SA), Gibberellin (GL), and the like as interfering factors. Clearly, DPV did not have significant response signals (c-d in fig. 10) when ABA, SA and GL were used as the detectors, indicating that the electrochemical immunosensor based on POM @ PPY membrane has excellent selectivity for indoleacetic acid. In addition, compared with the single detection of the indoleacetic acid, when other plant growth hormone or hormones are added at the same time when the indoleacetic acid is detected (a represents the indoleacetic acid + abscisic acid; b represents the indoleacetic acid + salicylic acid; c represents the indoleacetic acid + gibberellin; d represents the indoleacetic acid + abscisic acid + salicylic acid + gibberellin), the peak current signal intensity of the DPV curve is not obviously changed (e-f in figure 10), and the electrochemical immunosensor is proved to have excellent anti-interference capability.
The six groups of anti-IAA/Au/POM @ PPY/GCEs are tested under the same experimental conditions, the DPV signals of the six groups of anti-IAA/Au/POM @ PPY/GCEs have no obvious difference, and the anti-IAA/Au/POM @ PPY/GCEs have good repeatability (a in FIG. 11). Further, stability of the electrochemical immunosensor constructed by the POM @ PPY film is evaluated by detecting indoleacetic acid by using POM @ PPY/GCE which is stored for a certain time as a working electrode. The test results showed that the DPV signal intensity did not change significantly after 21 days of standing at room temperature (b in fig. 11).
From the results, the electrochemical immunosensor constructed by the POM @ PPY film has the advantages of wide linear range, low detection limit, excellent selectivity, excellent anti-interference capability and good repeatability and stability, and can promote the application of polyoxometallate-based functional materials in the biological field.