CN108037163B - Cu3P@Ti-MOF-NH2Composite material, electrochemical sensor and preparation method and application thereof - Google Patents
Cu3P@Ti-MOF-NH2Composite material, electrochemical sensor and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to Cu3P@Ti‑MOF‑NH2Composite material, electrochemical sensor, and preparation method and application thereof. The composite material is prepared by the following steps: 2-amino terephthalic acid,Tetrabutyl titanate, Cu3And carrying out solvothermal reaction on the P in a solvent to obtain the compound. Cu provided by the invention3P@Ti‑MOF‑NH2Composite material, Cu3P and Ti-MOF-NH2The strong synergistic effect exists between the two components, and the effective charge separation and transfer on the catalyst interface can be promoted, so that the electrocatalytic oxidation of the hydrazine hydrate is promoted. Electrochemical tests show that Cu3P@Ti‑MOF‑NH2The composite material shows outstanding electrocatalytic activity on the oxidation of hydrazine hydrate, and the electrode prepared from the composite material has higher sensitivity and selectivity on the detection of hydrazine hydrate, and has huge application prospect in the field of electrochemical analysis.
Description
Technical Field
The invention belongs to the field of electrochemical sensors, and particularly relates to Cu3P@Ti-MOF-NH2Composite material, electrochemical sensor, and preparation method and application thereof.
Background
Hydrazine hydrate is widely used as an important chemical raw material in the fields of agriculture, fine chemicals, fuel cells, explosives, photographic chemicals, preservatives, weapons, emulsifiers, pharmacology, and the like. Hydrazine is classified as a carcinogen by the united states Environmental Protection Agency (EPA) due to its mutagenicity, carcinogenicity and neurotoxicity. Currently, there are many analytical methods for determining hydrazine hydrate in water, including titration, chromatography, spectrophotometry, chemiluminescent flow injection analysis, potentiometry and electroanalytical methods. When the conventional method is adopted to measure hydrazine hydrate, the defects of high instrument cost, difficult carrying, time consumption and poor applicability exist.
The electrochemical method has the characteristics of quick reaction, simple operation, on-site analysis, good sensitivity and economy and the like when detecting pollutants, and is very suitable for detecting hydrazine hydrate. However, conventional electrodes are not suitable for electrochemical determination of hydrazine hydrate due to limitations of high oxidation overpotentials, slow electron transport, etc. Platinum, gold, silver and the like have high catalytic activity, but are very expensive, and are greatly limited in practical application. The research on the electrocatalyst with low cost and high catalytic activity can be conveniently and sensitively applied to the electrochemical oxidation of hydrazine hydrate, and has very important significance.
Metal Organic Framework (MOF) is a new type of nanoporous crystalline material formed by interconnecting metal cations and organic ligands, and due to its chemical property adjustability and structural diversity, MOF has great applications in the fields of gas storage and separation, molecular detection, biomedicine, electronics, optoelectronic devices, catalysis, etc. At present, an electrocatalyst for detecting hydrazine hydrate constructed based on MOF is rarely reported.
Disclosure of Invention
The invention aims to provide Cu3P@Ti-MOF-NH2The composite material solves the problems of low electrocatalytic activity and poor selectivity of the existing hydrazine hydrate detection electrode material. The invention also provides an electrochemical sensor, a preparation method and application.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
cu3P@Ti-MOF-NH2A composite material prepared by a method comprising the steps of: 2-amino terephthalic acid, tetrabutyl titanate and Cu3And carrying out solvothermal reaction on the P in a solvent to obtain the compound.
Cu provided by the invention3P@Ti-MOF-NH2Composite material, Cu3P and Ti-MOF-NH2The strong synergistic effect exists between the two components, and the effective charge separation and transfer on the catalyst interface can be promoted, so that the electrocatalytic oxidation of the hydrazine hydrate is promoted. Electrochemistry methodThe test shows that Cu3P@Ti-MOF-NH2The composite material shows outstanding electrocatalytic activity on the decomposition of hydrazine hydrate, and the electrode prepared from the composite material has higher sensitivity and selectivity on the detection of hydrazine hydrate, and has huge application prospect in the field of electrochemical analysis.
2-amino terephthalic acid, tetrabutyl titanate, Cu3The dosage ratio of P is (0.2-0.3) g: (0.2-0.3) mL: (5-100) mg. The actual amount of the above-mentioned main raw materials may be enlarged or reduced according to the above-mentioned ratio. Preferably, 2-aminoterephthalic acid, tetrabutyl titanate, Cu3The dosage ratio of P is (0.2-0.3) g: (0.2-0.3) mL: 50 mg. The raw materials are controlled within the proportion range, and good electrocatalytic activity effect is obtained.
The solvent is methanol and N, N-dimethylformamide.
Mixing Cu3Dispersing P in methanol solution of PVP, centrifuging to obtain solid phase, dispersing the solid phase in N, N-dimethylformamide to obtain Cu3P dispersion of Cu3The P dispersion as a raw material undergoes the solvothermal reaction with methanol, 2-aminoterephthalic acid, tetrabutyl titanate. Cu3P, PVP, the dosage ratio of methanol is (5-100) mg: (0.3-0.4) g: (9-10) mL. Preferably, the Mw of PVP is 20000-. Cu3The P reacts with the mixed solution in the form of the dispersion liquid, can promote the reaction to be carried out uniformly and efficiently, and is helpful for further optimizing Cu3P@Ti-MOF-NH2Cu in composite material3The dispersion effect of P improves the electrocatalytic performance of the composite material.
Cu3P can be prepared according to the prior art. Preferably, the Cu3P is prepared by a method comprising the following steps: mixing Cu (OH)2And NaH2PO2And (3) mixing, and reacting for 1-3 h at 280-320 ℃ in a protective atmosphere to obtain the catalyst. Preferably, Cu (OH)2、NaH2PO2The mass ratio of (A) to (B) is as follows: 0.05: (0.2-0.3). Cu (OH)2Can pass through Cu (NO)3)2·3H2The O solution and the excessive NaOH solution. Cu can be conveniently obtained by adopting the steps3P nanocrystals, withTi-MOF-NH2The preparation process has good adaptability, and the obtained Cu3P@Ti-MOF-NH2The stability and repeatability of the composite material are good.
The solvent thermal reaction is carried out for 24-48 h at the temperature of 140-160 ℃.
Cu prepared by adopting the preferred scheme3P@Ti-MOF-NH2The composite material has the characteristics of simplicity, economy and high electrocatalytic activity, can be conveniently and efficiently used for trace detection of hydrazine hydrate, and has good application prospect.
The electrochemical sensor adopts the technical scheme that:
an electrochemical sensor comprises a substrate electrode and Cu attached to the substrate electrode3P@Ti-MOF-NH2A composite material.
The substrate electrode is a glassy carbon electrode. Glassy carbon electrodes of other diameters, Cu3P@Ti-MOF-NH2The amount of the composite material can be determined by calculation based on the above ratio.
The electrochemical sensor of the invention shows high catalytic activity and selectivity for detecting hydrazine hydrate, and can be conveniently used for conveniently, conveniently and efficiently detecting hydrazine hydrate.
The preparation method of the electrochemical sensor comprises activating the substrate electrode, and using the electrochemical sensor containing Cu3P@Ti-MOF-NH2And modifying the activated electrode by using the dispersion liquid of the composite material, and drying to obtain the electrode.
The basal body electrode can be a glassy carbon electrode. The activation of the glassy carbon electrode can adopt the prior art, and preferably, the activation of the glassy carbon electrode comprises the following steps: polishing the glassy carbon electrode by using paste liquid of alumina powder, washing by using nitric acid solution, ethanol solution and water in sequence, and drying to obtain the product.
Containing Cu3P@Ti-MOF-NH2The dispersion of the composite material comprises water and Cu3P@Ti-MOF-NH2Composite composition, control of Cu3P@Ti-MOF-NH2The concentration of the composite material is 1-2 mg/mL-1。
The preparation method of the electrochemical sensor provided by the invention has the advantages of simple process and low manufacturing cost, greatly reduces the trace detection cost of hydrazine hydrate, and improves the effectiveness and the applicability of the trace detection of hydrazine hydrate.
The invention also provides the application of the electrochemical sensor in hydrazine hydrate detection.
On the basis of the electrochemical sensor, the trace detection of hydrazine hydrate in water can be realized according to the existing electrochemical method.
Hydrazine hydrate is detected by the electrochemical sensor of the invention, and the lowest detection limit of hydrazine hydrate is 0.079 mu M (S/N-3) in a linear range of 5 mu M to 7.5 mM. In addition, when some common interferents are added, the electrochemical sensor has high selectivity, stability and practical feasibility for detecting hydrazine hydrate, and reflects good detection capability.
Drawings
FIG. 1 shows (i) Ti-MOF-NH2、(ii)Cu3P、(iii)Cu3P@Ti-MOF-NH2-5、(iv)Cu3P@ Ti-MOF-NH2-20、(v)Cu3P@Ti-MOF-NH2-50 and (vi) Cu3P@Ti-MOF-NH2-100X-ray diffraction spectrum;
FIG. 2 shows (i) Ti-MOF-NH2、(ii)Cu3P、(iii)Cu3P@Ti-MOF-NH2-5、(iv)Cu3P@ Ti-MOF-NH2-20、(v)Cu3P@Ti-MOF-NH2-50 and (vi) Cu3P@Ti-MOF-NH2-an X-ray photoelectron energy spectrum of 100;
FIG. 3 shows (a) Cu3P@Ti-MOF-NH2-5，(b)Cu3P@Ti-MOF-NH2-20，(c) Cu3P@Ti-MOF-NH2-50 and (d) Cu3P@Ti-MOF-NH2-100 high resolution XPS spectra of C1 s, Cu 2p and Ti 2p of the composite;
in FIG. 4, (a), (b), (c) and (d) are Cu, respectively3P@Ti-MOF-NH2-5、 Cu3P@Ti-MOF-NH2-10、Cu3P@Ti-MOF-NH2-50 and Cu3P@Ti-MOF-NH2FESEM image of (e) 100, (e) each of Cu3P@Ti-MOF-NH2-50 composite materials of Ti, Cu and CElemental analysis;
in FIG. 5, (a, b), (c, d), (e, f) and (g, h) are Cu, respectively3P@Ti-MOF-NH2-5、 Cu3P@Ti-MOF-NH2-20、Cu3P@Ti-MOF-NH2-50 and Cu3P@Ti-MOF-NH2-TEM and HR-TEM images of 100 composite materials, the insets in (b), (d), (f) and (h) being the corresponding selected area electron diffraction images, respectively;
FIG. 6 is Cu3P@Ti-MOF-NH2-50 nitrogen adsorption-desorption isotherms of the composite;
FIG. 7 is Cu3P@Ti-MOF-NH2-50 pore size distribution of the composite material;
FIG. 8 shows GCE, Ti-MOF-NH2/GCE、Cu3P/GCE、Cu3P@Ti-MOF-NH2-5/GCE、 Cu3P@Ti-MOF-NH2-20/GCE、Cu3P@Ti-MOF-NH2-50/GCE and Cu3P@Ti-MOF-NH2-nyquist plot of 100/GCE;
FIG. 9 shows GCE, Ti-MOF-NH2/GCE、Cu3P/GCE、Cu3P@Ti-MOF-NH2-5/GCE、 Cu3P@Ti-MOF-NH2-20/GCE、Cu3P@Ti-MOF-NH2-50/GCE and Cu3P@Ti-MOF-NH2-cyclic voltammogram at 100/GCE;
FIG. 10 is Ti-MOF-NH2/GCE、Cu3P/GCE and Cu3P@Ti-MOF-NH2The sweep rate of the/GCE in a 0.2M NaOH solution was 50 mV. multidot.s-1Measuring a cyclic voltammogram under the conditions of (1);
FIG. 11 shows the concentration of 50 mV. multidot.s in the presence of 2.0mM hydrazine hydrate-1At a scanning rate of N2Cyclic voltammograms measured in saturated 0.2M NaOH solution;
FIG. 12 is a graph of the difference in scan rates (from low to high: 25, 50, 75, 100, 150, 200, 250 and 300 mV. multidot.s)-1) Containing 2.0mM hydrazine hydrate2Cyclic voltammogram of the electrode of example 1 in saturated 0.2M NaOH solution, inset is the electrocatalytic oxidation current profile for hydrazine hydrate;
FIG. 13 is a graph of hydrazine hydrate at various concentrations (low to high: 0, 1, m,2. 3, 4, 5, 6, 7 and 9mM) at a scan rate of 50mV · s-1When is at N2Cyclic voltammogram of the electrode of example 1 in a saturated 0.2M NaOH solution;
FIG. 14 is a graph of the current response of the electrode of example 1 in varying concentrations of hydrazine hydrate;
FIG. 15 is a calibration curve of current response versus hydrazine hydrate concentration for the electrode of example 1;
FIG. 16 shows the continuous addition of 0.1mM hydrazine hydrate (i), 50mM NaCl (ii), Na to a 0.2M NaOH solution at a voltage of +0.45V (vs. Ag/AgCl)2CO3(iii), sodium citrate (iv), KNO3(ⅴ)、 Na2SO4(vi) current response plots;
FIG. 17 shows the electrode of example 1 at N2Current response to 5mM hydrazine hydrate in saturated 0.2M NaOH solution at 1800s run time, insert Cu after 7 days3P@Ti-MOF-NH2Response value of cyclic voltammetry of 50/GCE.
Detailed Description
Embodiments of the present invention are further described below with reference to specific examples. In the following examples, tetrabutyl titanate (TBOT), 2-aminoterephthalic acid (H)2BDC-NH2；C8H7NO4) N' -N-dimethylformamide (DMF; (CH)3)2NCHO), methanol (CH)3OH), copper nitrate trihydrate (Cu (NO)3)2·3H2O), sodium hypophosphite (NaH)2PO2) PVP (Mw 40000) and hydrazine hydrate (HHA; n is a radical of2H4·H2O) was purchased from alatin chemical limited (shanghai, china). NaOH and ammonium hydroxide (NH)4OH) was purchased from national pharmaceutical chemicals, ltd. Other reagents were analytically pure and no further purification treatment was required. Ultrapure water was obtained from a Milli-Q water purification system.
Example 1
Cu of the present example3P@Ti-MOF-NH2The composite material is prepared by the following steps:
1)Cu3preparation of P: at room temperature under magnetic stirring, the excess will be50mL of Cu (NO) with a concentration of 0.05mol/L was added to the 0.25mol/L NaOH solution3)2·3H2Reacting in O solution for 0.5h, centrifuging the precipitate, washing with water for several times, and drying in vacuum to obtain Cu (OH)2；
0.05g of Cu (OH)2And 0.25g NaH2PO2Mixing and grinding to obtain mixture, adding the mixture into N2At 2 ℃ min under an atmosphere-1Heating to 300 ℃, preserving heat for 2 hours, naturally cooling, washing the obtained black solid with ultrapure water and ethanol for a plurality of times, and drying in a vacuum oven for later use;
2) 50mg of Cu3Adding P to a methanol solution of PVP (0.35g PVP mixed with 10mL methanol), stirring at room temperature for 12h, centrifuging, washing with methanol three times, dispersing the obtained solid phase in 3.6mL DMF to obtain Cu3A P dispersion;
adding 0.4mL of methanol, 0.22g of 2-aminoterephthalic acid and 0.24mL of tetrabutyl titanate into a beaker, and magnetically stirring for 5min to form a mixed solution;
mixing Cu3Mixing the P dispersion liquid and the mixed solution, transferring the mixture into a polytetrafluoroethylene-lined reaction kettle, reacting for 48 hours at 150 ℃, centrifugally collecting solid matters, washing the solid matters for three times by using methanol, and drying to obtain Cu3P@Ti-MOF-NH2-50。
The electrochemical sensor of the embodiment comprises a glassy carbon electrode and Cu attached to the surface of the glassy carbon electrode3P@Ti-MOF-NH2Composite material, glassy carbon electrode diameter 3.0mm, Cu3P@Ti-MOF-NH2The amount of-50 is 0.01 mg. The electrochemical sensor is prepared by the following steps:
1) the glassy carbon electrode was polished in a paste of alumina powders having particle diameters of 0.3 μm and 0.05 μm in this order, and then treated with a nitric acid solution (concentrated nitric acid: distilled water at a volume ratio of 1:1), an ethanol solution (absolute ethanol: distilled water with the volume ratio of 1:1) and washing with distilled water to obtain an activated electrode; mixing Cu3P@Ti-MOF-NH2-50 in water at a concentration of 1 mg. mL-1The suspension of (a);
2) 10 μ L of suspension was droppedAdding the solution to an activated electrode, and drying the activated electrode in nitrogen flow to obtain the electrochemical sensor Cu3P@Ti-MOF-NH2-50/GCE。
Example 2
Cu of the present example3P@Ti-MOF-NH2The composite material is prepared by the following steps:
1)Cu3p was prepared as in example 1;
2) mixing 5mg of Cu3Adding P to a methanol solution of PVP (0.35g PVP mixed with 10mL methanol), stirring at room temperature for 12h, centrifuging, washing with methanol three times, dispersing the obtained solid phase in 3.6mL DMF to obtain Cu3A P dispersion;
adding 0.4mL of methanol, 0.22g of 2-aminoterephthalic acid and 0.24mL of tetrabutyl titanate into a beaker, and magnetically stirring for 5min to form a mixed solution;
mixing Cu3Mixing the P dispersion liquid and the mixed solution, transferring the mixture into a polytetrafluoroethylene-lined reaction kettle, reacting for 48 hours at 150 ℃, centrifugally collecting solid matters, washing the solid matters for three times by using methanol, and drying to obtain Cu3P@Ti-MOF-NH2-5。
The electrochemical sensor of this example, Cu was prepared by the method of reference example 13P@Ti-MOF-NH2-5/GCE。
Example 3
Cu of the present example3P@Ti-MOF-NH2The composite material is prepared by the following steps:
1)Cu3p was prepared as in example 1;
2) 20mg of Cu3Adding P to a methanol solution of PVP (0.35g PVP mixed with 10mL methanol), stirring at room temperature for 12h, centrifuging, washing with methanol three times, dispersing the obtained solid phase in 3.6mL DMF to obtain Cu3A P dispersion;
adding 0.4mL of methanol, 0.22g of 2-aminoterephthalic acid and 0.24mL of tetrabutyl titanate into a beaker, and magnetically stirring for 5min to form a mixed solution;
mixing Cu3Mixing the P dispersion liquid and the mixed solution, and transferring to polytetrafluoroethyleneReacting in a reaction kettle with a lining at 150 ℃ for 48h, centrifuging to collect solid matters, washing with methanol for three times, and drying to obtain Cu3P@Ti-MOF-NH2-20。
The electrochemical sensor of this example, Cu was prepared by the method of reference example 13P@Ti-MOF-NH2-20/GCE。
Example 4
Cu of the present example3P@Ti-MOF-NH2The composite material is prepared by the following steps:
1)Cu3p was prepared as in example 1;
2) mixing 100mg of Cu3Adding P to a methanol solution of PVP (0.35g PVP mixed with 10mL methanol), stirring at room temperature for 12h, centrifuging, washing with methanol three times, dispersing the obtained solid phase in 3.6mL DMF to obtain Cu3A P dispersion;
adding 0.4mL of methanol, 0.22g of 2-aminoterephthalic acid and 0.24mL of tetrabutyl titanate into a beaker, and magnetically stirring for 5min to form a mixed solution;
mixing Cu3Mixing the P dispersion liquid and the mixed solution, transferring the mixture into a polytetrafluoroethylene-lined reaction kettle, reacting for 48 hours at 150 ℃, centrifugally collecting solid matters, washing the solid matters for three times by using methanol, and drying to obtain Cu3P@Ti-MOF-NH2-100。
The electrochemical sensor of this example, Cu was prepared by the method of reference example 13P@Ti-MOF-NH2-100/GCE。
Comparative example 1
The electrode modification material used in the electrochemical sensor of comparative example 1 was Cu3P, prepared by the method of reference example 1. Then adding Cu3The concentration of P and water is 1 mg/mL-1Was prepared by the method of reference example 1, and an electrochemical sensor Cu was prepared3P/GCE。
Comparative example 2
The electrode modification material used in the electrochemical sensor of comparative example 2 was Ti-MOF-NH2The preparation method comprises the following steps: 3.6mL of DMF, 0.4mL of methanol, 0.22g of 2-aminoterephthalic acid and 0.24m of methanol were mixed togetherAdding tetrabutyl titanate into a beaker, and magnetically stirring for 5min to form a mixed solution; mixing the mixed solution, transferring the mixed solution into a reaction kettle with a polytetrafluoroethylene lining, reacting for 48 hours at 150 ℃, centrifugally collecting solid substances, washing with methanol for three times, and drying to obtain Ti-MOF-NH2. Preparation of electrochemical sensor Ti-MOF-NH by the method of reference example 12/GCE。
Test example 1
The present experimental example analyzes the crystal structure and chemical structure of the composite material of each example using XRD and XPS. X-ray diffraction measurements (XRD) were performed on a Rigaku D/Max-2500X-ray diffractometer using CuK α radiation, and the results are shown in FIG. 1. X-ray photoelectron spectroscopy (XPS) data was measured using an axihis 165 spectrometer (Kratos Analytical, Manchester, UK) with a monochromatic aik α X-ray source (1486.71eV photons) and the results are shown in fig. 2.
As can be seen from FIG. 1, all diffraction peaks of curve i have the same diffraction pattern as that of Ti-MOF-NH2The simulated diffraction peaks of (a) were consistent. Cu3The diffraction peaks of P (curve ii) are 29.0 °, 36.0 °, 39.0 °, 41.6 °, 45.1 °, 46.1 °, 47.3 °, 53.4 °, 59.0 °, 66.5 ° and 73.4 °, respectively, corresponding to the lattice diffraction of the hexagonal lattices (012), (112), (202), (121), (300), (113), (122), (104), (222), (124) and (232) (JCPDS No. 65-3628). The two peaks at 43.3 ° and 50.4 ° indicate metallic copper (JCPDS No. 04-0836). Cu for curves iii and iv3P@Ti-MOF-NH2Nanocomposite material, Cu3The characteristic diffraction peak of P is not very obvious, probably due to Cu3The amount of P nanocrystals used is small, resulting in Cu3P to Ti-MOF-NH2The influence of the formation of the single crystal framework is small. When Cu3At a dosage of P of 50mg (curve v), Ti-MOF-NH is removed2In addition to the diffraction peak of (2), Cu was observed3P, indicating that the two complex well. However, when Cu3When the amount of P was increased to 100mg (curve vi), Cu was observed3Diffraction peak of P, and Ti-MOF-NH2The diffraction peak of (A) is not obvious, indicating that the Ti-MOF-NH is2Is inhibited.
In FIG. 2, in Ti-MOF-NH2In which Ti is observedC, N and O, in Cu3Cu, P and C elements are observed in P. Cu3P@Ti-MOF-NH2The presence of Cu, Ti, C, N, P and O was observed in the composite. In Table 1, with Cu in the composite3The increasing of the P dosage increases the Cu atomic percent from 0.27% to 4.68% and the P atomic percent from 0.83% to 7.40%.
TABLE 1 atomic percent of composites of the examples and comparative examples
To study Cu3P@Ti-MOF-NH2The chemical composition and electronic valence of each element in the composite material were analyzed for high resolution XPS, as shown in fig. 3.
In fig. 3, the C1 s spectrum is broken down into four peaks, 284.6eV, 285.4eV, 286.4eV and 288.6eV, corresponding to C-C/C-H, C-N, N-C ═ O/C ═ O and COO-groups, respectively, which are derived from the organic ligands and solvent residues contained in the MOF. Due to Cu3P@Ti-MOF-NH2Preparation of (E) -5 Cu3The amount of P used is small, so the signal of Cu 2P is not significant. With Cu3With further increase in P dosage, the Cu 2P spectrum can be divided into 6 fractions, with peaks of 932.6eV and 952.42eV corresponding to Cu 2P3/2And Cu 2p1/2Indicating the presence of the cu (i) valence, the peaks of 943.26eV and 962.85eV are their corresponding satellite peaks, respectively. The signals of the high energy peaks at 934.2eV and 954.3eV are due to the Cu (II) valence state. Two distinct peaks were observed at 458.7eV and 464.5eV, which correspond to Ti 2p3/2And Ti 2p1/2The result shows that titanium in the Ti-O cluster is in an IV oxidation state.
Test example 2
In this test example, Cu of each example was observed3P@Ti-MOF-NH2Surface topography of the composite. The shape of each composite material was observed using JSM-6490LV scanning electron microscope (SEM, Japan)States, as shown in FIG. 4; high resolution transmission electron microscope images (HR-TEM) were recorded under a JEOL JEM-2100 high resolution transmission electron microscope, as shown in FIG. 5.
In FIG. 4, Cu3P@Ti-MOF-NH2The surface of the composite material is rough. Cu3P@Ti-MOF-NH2-5 in the form of platelets and the remaining three samples in the form of octahedral structures (FIGS. 4a-d), Cu3P@Ti-MOF-NH2Elemental measurements at-50 confirmed the presence of Ti, Cu and C in the nanocomposite (FIGS. 4 e-g).
In FIG. 5, TEM and HR-TEM images show Cu with a diameter of about 2-5nm3P nanocrystals are grown and embedded in Ti-MOF-NH2In a matrix. Cu3The (012), (300) and (113) planes of P correspond to lattice spacings of 0.307 nm, 0.201nm and 0.196nm, respectively, which corresponds to the results of XRD.
Test example 3
Cu of the present test example for each example3P@Ti-MOF-NH2The composite was subjected to nitrogen adsorption-desorption studies. Obtaining N under ultra-high vacuum using a Belsorp MAX volumetric adsorption apparatus2The adsorption-desorption data, the results are shown in fig. 6 and 7.
In FIG. 6, Cu3P@Ti-MOF-NH2-50 specific surface area of the composite material 327.7m2g-1. In FIG. 7, Cu3P@Ti-MOF-NH2-50 shows a narrow distribution centered at 2-5nm, indicating that the pore size of the composite is mesoporous.
Test example 4
The experimental examples were subjected to Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and chronoamperometry (i-t curves) at room temperature using an electrochemical workstation (CHI760D, Shanghai Chenhua Instruments co., China). A three-electrode system was used, with the electrodes made in each example and comparative example as the working electrode, Ag/AgCl (saturated KCl) as the reference electrode, and Pt as the counter electrode. EIS was tested at 5.0mM K3Fe(CN)6/K4Fe(CN)6(1:1) and 0.1M KCl, with a frequency of 0.01Hz to 100kHz and an amplitude of 5 mV. CV and i-t curves with stirring and N2In 0.2M NaOH electrolyteThe solution was measured. CV was measured from-0.2V to 0.8V at a scan rate of 50 mV. multidot.s-1. Hydrazine hydrate was detected by chronoamperometry with various concentrations of hydrazine hydrate measured in 0.2M NaOH solution. Calculating the average current of each concentration by three repeated experiments; error bars on the calibration curve show the standard deviation from the mean.
In fig. 8, the electrode shows electrochemical behavior similar to that of a capacitive circuit in the high and low frequency regions. The nyquist plot for each electrode has a semicircular portion corresponding to the course of faradic current generated by the kinetic electrochemical reaction of the redox probe at the electrode surface. Furthermore, the nyquist plots for all samples can be simulated using the same equivalent circuit (inset of fig. 8). In this model, Rs, Rct, W, CPE represent solution resistance, charge transfer resistance, Warburg resistance, and constant phase element, respectively. Since the semi-circle diameter is equal to Rct in the interface, the Rct values for all modified electrodes can be derived by fitting the nyquist curve. Cu3The Rct value for P/GCE was 1604 ohms, which is the highest among all electrodes, indicating a slow electron transfer rate at the electrode interface. Ti-MOF-NH2Rct value for/GCE 286 ohm compared to Cu of examples 1-43P@Ti-MOF-NH2The Rct value of the composite material modified electrode is between Cu3P/GCE and Ti-MOF-NH2Middle of the/GCE. Cu3P@Ti-MOF-NH2-5/GCE and Cu3P@Ti-MOF-NH2The Rct values for-20/GCE are 1481 ohm and 335 ohm, respectively. For Cu3P@Ti-MOF-NH2-50/GCE, with Rct value minimum in all examples, 319 ohms, indicating that the composite has a synergistic effect of enhanced electron transfer at the interface. When Cu3When the amount of P was further increased to 100mg, the Rct value of the composite-modified electrode increased to 661 ohms, indicating that the electron transfer rate began to slow down.
In FIG. 9, the bare GCE electrode had a well-defined peak of reversible redox couple, with a difference of approximately 156 mV. After electrode modification is carried out by using an electrode material, the peak separation value is increased, and the redox peak current is slightly reduced. Examples 1 to 4, Cu3P@Ti-MOF-NH2the-50/GCE had the highest current and the minimum peak separation value (225 mV). This result shows that the electrode of example 1 can more easily and rapidly perform the electrochemical reaction of hydrazine hydrate, and the electrocatalytic activity is optimal.
Figure 10 is a CV plot for all electrodes in a 0.2M NaOH solution in the absence of hydrazine hydrate. Wherein, Cu3Area of P/GCE is minimal, and Ti-MOF-NH2The maximum CV curve area of the/GCE indicates Ti-MOF-NH2the/GCE showed the best electrochemical activity in 0.2M NaOH solution.
FIG. 11 is a CV curve of each electrode in 0.2M NaOH solution in the presence of hydrazine hydrate, and it can be seen that each electrode has a distinct anodic peak for hydrazine hydrate oxidation, wherein Cu is present3P@Ti-MOF-NH2The highest response of-50/GCE in the presence of hydrazine hydrate indicates the best electrocatalytic activity towards hydrazine hydrate, and also demonstrates that Cu in the composite material of example 13P and Ti-MOF-NH2Has strong synergistic effect.
FIG. 12 is a graph showing the effect of scan rate on peak current of hydrazine hydrate, and it can be seen that the anodic peak current increases with increasing scan rate, with peak current and square root of scan rate ranging from 25 to 300mV · s-1Range memory is in linear relationship (inset of FIG. 12). This indicates that Cu is in alkaline solution3P@Ti-MOF-NH2The electrochemical behavior of-50/GCE belongs to the diffusion control electrode process.
Fig. 13 is a graph showing the effect of hydrazine hydrate concentration on the peak anodic current by CV measurement, and it can be seen that as the hydrazine hydrate concentration increases, the anodic current of the modified electrode significantly increases and the anodic peak shifts to the positive potential. As can be seen from fig. 10 to 13, the composite material of each example has high catalytic activity for oxidation of hydrazine hydrate, of which electrocatalytic activity of the composite material of example 1 is the best.
FIG. 14 shows Cu3P@Ti-MOF-NH2-50/GCE at an applied potential of +0.45V at N2Typical current responses of saturated 0.2M NaOH solutions with various concentrations of hydrazine hydrate, as can be seen in FIG. 15, the current response and the concentration of hydrazine hydrate, linear range is 5. mu.M to 7.5mM,the correlation coefficient was 0.998, and the corresponding linear regression equation was expressed as I (μ a) ═ 0.62+10.87Chydrazine(mM). The detection limit was calculated to be 0.079. mu.M based on a signal-to-noise ratio of 3. This shows that Cu is based3P@Ti-MOF-NH2The prepared electrochemical sensor shows excellent sensing performance when detecting hydrazine hydrate.
In FIG. 16, Cu3P@Ti-MOF-NH250/GCE has a higher response to 0.1mM hydrazine hydrate and 50mM other interferents (including NaCl, Na)2CO3Sodium citrate, KNO3And Na2SO4) No obvious current response exists, and the composite material modified electrode has higher selectivity in hydrazine hydrate detection.
FIG. 17 shows the results of the study at N2Saturated 0.2M NaOH solution, Cu3P@Ti-MOF-NH2Long-term stability of the/GCE electrochemical sensor, it can be seen from the figure that the current reaches a relatively stable value within 250 seconds and remains at 95.7% of the stable value after a running time of 1800 s. The inset in FIG. 17 shows that the electrode retained 99.0% of its original peak current value after 7 days of storage at 4 deg.C, indicating Cu3P@Ti-MOF-NH2The stability of the/GCE sensor is good.
Test example 5
This test example investigated Cu3P@Ti-MOF-NH2Per GCE Utility in actual samples, three different water sources were added to 100, 300 and 500 μ M hydrazine hydrate, respectively, and subjected to N2The applied voltage was measured in 0.2M NaOH solution under protection to be +0.45V (vs. Ag/AgCl), and the results are shown in Table 2.
Table 2 determination of hydrazine hydrate in real samples (n ═ 3)
From the results in table 2, it is clear that the recovery rate in the actual sample detection is 90.3-106.2%, indicating that the developed sensor has good practical applicability for detecting hydrazine hydrate in sample analysis.
As can be seen from the above test examples, eachCu prepared in example3P@Ti-MOF-NH2The modified GCE can be used for electrocatalytic oxidation of hydrazine hydrate, the lowest detection limit of the sensor in a linear range of 5 mu M to 7.5mM is 0.079 mu M, and the sensor has good selectivity and stability and practical feasibility under the condition that some common interferents for detecting hydrazine hydrate exist, so that the sensor has good detection capability on the determination of hydrazine hydrate. All these results show that Ti-MOF-NH2The related nanocomposites have potential applications to build efficient sensors to detect other analytes in environmental and biological fields.
Claims (9)
1. Cu3P@Ti-MOF-NH2The composite material is characterized by being prepared by a method comprising the following steps: 2-amino terephthalic acid, tetrabutyl titanate and Cu3Carrying out solvothermal reaction on the P in a solvent to obtain the compound; the method specifically comprises the following steps: mixing Cu3Dispersing P in methanol solution of PVP, centrifuging to obtain solid phase, dispersing the solid phase in N, N-dimethylformamide to obtain Cu3P dispersion of Cu3And carrying out the solvothermal reaction on the P dispersion liquid serving as a raw material, 2-amino terephthalic acid and tetrabutyl titanate, wherein the MOF is a metal organic framework material, and the PVP is polyvinylpyrrolidone.
2. Cu according to claim 13P@Ti-MOF-NH2The composite material is characterized by comprising 2-amino terephthalic acid, tetrabutyl titanate and Cu3The dosage ratio of P is (0.2-0.3) g: (0.2-0.3) mL: (5-100) mg.
3. Cu according to claim 1 or 23P@Ti-MOF-NH2Composite material, characterized in that Cu3P, PVP, the dosage ratio of methanol is (5-100) mg: (0.3-0.4) g: (9-10) mL.
4. Cu according to claim 13P@Ti-MOF-NH2Composite material, characterized in that the Cu3The P is prepared by adopting a method comprising the following steps: mixing Cu (OH)2And NaH2PO2And (3) mixing, and reacting for 1-3 h at 280-320 ℃ in a protective atmosphere to obtain the catalyst.
5. Cu according to claim 13P@Ti-MOF-NH2The composite material is characterized in that the solvothermal reaction is carried out for 24-48 h at the temperature of 140-160 ℃.
6. Use of the Cu of claim 13P@Ti-MOF-NH2An electrochemical sensor of composite material, comprising a base electrode and Cu attached to the base electrode3P@Ti-MOF-NH2A composite material.
7. The electrochemical sensor of claim 6, wherein the substrate electrode is a glassy carbon electrode.
8. A method of manufacturing an electrochemical sensor as claimed in claim 6, comprising activating the substrate electrode and then using a material containing Cu3P@Ti-MOF-NH2And modifying the activated electrode by using the dispersion liquid of the composite material, and drying to obtain the electrode.
9. Use of an electrochemical sensor according to claim 6 in the detection of hydrazine hydrate.
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