Preparation method and application of co-fe pba derived co / fe-based oxide nanoflower material

Abstract

The application relates to a preparation method and application of Co-Fe PBA derived Co / Fe-based oxide nanoflower materials, and relates to a preparation method and application of Co / Fe-based oxide materials. The application aims at solving the problem that Co3[Fe(CN)6]2 prepared by an existing method is almost in a cubic shape. The preparation method comprises the following steps: one, preparing a nanoflower-shaped Co3[Fe(CN)6]2 precursor; two, heat treatment. Application, which is used for preparing a humidity sensing element to detect humidity. The application is used for the preparation and application of Co-Fe PBA derived Co / Fe-based oxide nanoflower materials.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method and application of Co / Fe-based oxide materials. BACKGROUND

[0002] Metal-organic frameworks (MOFs) refer to one-dimensional, two-dimensional or three-dimensional crystalline materials generated by bridging metal ions or metal clusters with organic ligands. Such materials generally have a larger specific surface area and can be adjusted in terms of pore structure and morphology as needed, and thus have a large number of applications in scientific research fields such as gas separation and storage, catalysis, energy storage, sensors and drug storage and transmission. Among the many MOF template materials, Prussian blue (PB) and Prussian blue analogues (PBAs) have attracted extensive attention due to their higher metal content and diverse compositions. As a typical Prussian blue analogue, Co3[Fe(CN)6]2is composed of Co 2+ and Fe 3+ two different metal ions inside and outside, respectively. By sintering Co3[Fe(CN)6]2precursors, Co3O4 / Fe2O3composite materials with the same morphology as the precursors can be obtained. In the existing synthesis method of Co3[Fe(CN)6]2, K3[Fe(CN)6]is first dissolved in water, and then a cobalt nitrate or cobalt acetate aqueous solution is added dropwise into the K3[Fe(CN)6]solution, and Co3[Fe(CN)6]2precursors are obtained by constant stirring. By calcining the precursors, Co3O4 / Fe2O3composite materials with the same morphology as the precursors can be obtained. Since the solubility of Co3[Fe(CN)6]2is small, even a small concentration of Co 2+ and [Fe(CN)6] 3- in the aqueous solution will quickly form Co3[Fe(CN)6]2precipitate, resulting in poor controllability of the product morphology. Although the method of adding cobalt nitrate solution dropwise can reduce the concentration of Co 2+ in the aqueous solution to some extent, thereby reducing the precipitation rate of Co3[Fe(CN)6]2, this method is time-consuming and labor-intensive, and the Co3[Fe(CN)6]2prepared by the existing method is almost in the form of a cube. The morphology of nanomaterials has a significant impact on the performance of the materials. Developing a new synthesis method to obtain Co3[Fe(CN)6]2and Co3O4 / Fe2O3composite materials with novel morphology will have broad application prospects. SUMMARY

[0003] The present application aims to solve the problem that Co3[Fe(CN)6]2prepared by the existing method is almost in the form of a cube, and further provides a preparation method and application of Co-Fe PBA derived Co / Fe-based oxide nanoflower materials.

[0004] A preparation method of Co-Fe PBA derived Co / Fe-based oxide nanoflower material, which is carried out according to the following steps:

[0005] I. Brominated 1-butyl-3-methyl imidazole is added into water, and magnetic stirring is carried out until complete dissolution, then K3[Fe(CN)]6 is added and magnetic stirring is carried out, to obtain a yellow-green clear solution, cobalt (II) acetylacetone is added into the yellow-green clear solution and magnetic stirring is carried out, to obtain a dark green suspension, the dark green suspension is sequentially aged, centrifuged, washed and dried, to obtain a nanoflower-shaped Co3[Fe(CN)6]2 precursor;

[0006] The mass ratio of the brominated 1-butyl-3-methyl imidazole to K3[Fe(CN)]6 is 1:(0.25-0.63); the mass ratio of the brominated 1-butyl-3-methyl imidazole to cobalt (II) acetylacetone is 1:(0.12-0.5);

[0007] II. The nanoflower-shaped Co3[Fe(CN)6]2 precursor is heat-treated, to obtain the Co-Fe PBA derived Co / Fe-based oxide nanoflower material.

[0008] The application of the Co-Fe PBA derived Co / Fe-based oxide nanoflower material is to prepare a humidity sensing element for humidity sensing detection.

[0009] The beneficial effects of the present application are:

[0010] The present application uses cobalt (II) acetylacetone and K3[Fe(CN)6] as reaction raw materials, utilizes the characteristics that cobalt (II) acetylacetone is slightly soluble in water, effectively reduces the Co 2+ concentration in the aqueous solution, thereby reducing the speed of Co 2+ co-precipitation with [Fe(CN)6] 3- , and then utilizes the structure guiding effect of the brominated 1-butyl-3-methyl imidazole surfactant to make the Co3[Fe(CN)6]2 nanoparticles self-assemble into a nanoflower morphology, and through sintering the Co3[Fe(CN)6]2 precursor in air, a Co3O4 / Fe2O3 composite material with the same nanoflower morphology is obtained.

[0011] The prepared Co3O4 / Fe2O3 nanoflower composite material is constructed into a humidity sensing element and the humidity sensing performance thereof is tested, the element has a high sensitivity of 1757 in the relative humidity range of 6-97% RH, and the response and recovery times are only 0.56 s and 9.35 s, and the humidity hysteresis value is 0.65%. In view of the characteristics such as fast response and recovery of the material, the material will have great application prospects in the fields of respiratory diagnosis and treatment, health monitoring and the like.

[0012] (1) The Co3O4 / Fe2O3 nanoflower is obtained by using Co3[Fe(CN)6]2 as a precursor.

[0013] (2) The Co3O4 / Fe2O3 nanoflower is obtained by using Co3[Fe(CN)6]2 as a precursor. 2+ The concentration of Co in water is effectively reduced, and the coprecipitation speed of Co3[Fe(CN)6]2 is reduced. At the same time, the Co3[Fe(CN)6]2 precipitate is separated from the water phase, further promoting the dissolution of cobalt (II) acetylacetone in water. The method can effectively reduce the generation speed of the product by using chemical principles, thereby effectively controlling the morphology of the product. Compared with the traditional method of slowing down the reaction speed by adding Co 2+ solution drop by drop, the method is time-saving, labor-saving and more effective, and is suitable for mass production.

[0014] (3) The Co3O4 / Fe2O3 nanoflower composite material is applied in the field of humidity sensors for the first time.

[0015] The application relates to a preparation method and application of a Co-Fe PBA derived Co / Fe-based oxide nanoflower material. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A scanning electron microscope image of the nanoflower-shaped Co3[Fe(CN)6]2 precursor prepared in step one of the embodiment;

[0017] Figure 2 An XRD spectrum of the nanoflower-shaped Co3[Fe(CN)6]2 precursor prepared in step one of the embodiment;

[0018] Figure 3 A scanning electron microscope image of the Co3O4 / Fe2O3 nanoflower material prepared in step two of the embodiment;

[0019] Figure 4 An XRD spectrum of the Co3O4 / Fe2O3 nanoflower material prepared in step two of the embodiment;

[0020] Figure 5 A response recovery curve of the humidity sensing element prepared in the embodiment two in a humidity range of 6% to 97%;

[0021] Figure 6 A humidity hysteresis curve of the humidity sensing element prepared in the embodiment two. DETAILED DESCRIPTION

[0022] DETAILED DESCRIPTION ONE: The preparation method of the Co-Fe PBA derived Co / Fe-based oxide nanoflower material is carried out according to the following steps:

[0023] I. Add brominated 1-butyl-3-methyl imidazole into water, magnetically stir until completely dissolved, then add K3[Fe(CN)]6 and magnetically stir to obtain a yellow-green clear solution, add cobalt (II) acetylacetonate into the yellow-green clear solution and magnetically stir to obtain a dark green suspension, sequentially age, centrifugalize, wash and dry the dark green suspension to obtain nanoflower-shaped Co3[Fe(CN)6]2 precursor;

[0024] The mass ratio of the brominated 1-butyl-3-methyl imidazole to K3[Fe(CN)]6 is 1:(0.25-0.63); the mass ratio of the brominated 1-butyl-3-methyl imidazole to cobalt (II) acetylacetonate is 1:(0.12-0.5);

[0025] II. Heat treat the nanoflower-shaped Co3[Fe(CN)6]2 precursor to obtain Co-Fe PBA derived Co / Fe-based oxide nanoflower material.

[0026] The beneficial effects of the present embodiment are:

[0027] The present embodiment uses cobalt (II) acetylacetonate and K3[Fe(CN)6] as reaction raw materials, utilizes the characteristics of cobalt (II) acetylacetonate that is slightly soluble in water, effectively reduces the Co 2+ concentration in the aqueous solution, thereby reducing the speed of Co 2+ co-precipitation with [Fe(CN)6] 3- , and further utilizes the structure guiding effect of the brominated 1-butyl-3-methyl imidazole surfactant to make the Co3[Fe(CN)6]2 nanoparticles self-assemble into nanoflower morphology, and through sintering the Co3[Fe(CN)6]2 precursor in air, a Co3O4 / Fe2O3 composite material with the same nanoflower morphology is obtained.

[0028] The prepared Co3O4 / Fe2O3 nanoflower composite material is constructed into a humidity sensing element and tested for humidity sensing performance, the element has a sensitivity as high as 1757 in the relative humidity range of 6-97% RH, and the response and recovery times are only 0.56 s and 9.35 s, and the humidity hysteresis is 0.65%. In view of the characteristics such as fast response and recovery of the material, the material will have great application prospects in the fields of respiratory diagnosis and treatment, health monitoring, etc.

[0029] (1) The present embodiment obtains nanoflower-shaped Co3O4 / Fe2O3 using Co3[Fe(CN)6]2 as precursor.

[0030] (2) The present embodiment utilizes the characteristics of cobalt (II) acetylacetonate that is slightly soluble in water and weakly ionized, effectively reduces the Co 2+concentration, and further reduces the coprecipitation rate of Co3[Fe(CN)6]2. Meanwhile, Co3[Fe(CN)6]2precipitates are separated from the aqueous phase, which further promotes the dissociation of cobalt (II) acetylacetone in the aqueous phase. The method of the present embodiment effectively reduces the product generation rate by using chemical principles, thereby effectively controlling the morphology of the product. Compared with the traditional method of slowing down the reaction rate by adding Co 2+ The present method is time-saving, labor-saving and more effective than the traditional method of slowing down the reaction rate by adding Co

[0031] (3) The present embodiment is the first application of Co3O4 / Fe2O3 nanoflower composite materials in the field of humidity sensors.

[0032] Specific embodiment two: The present embodiment is different from the first embodiment in that the mass / volume ratio of brominated 1-butyl-3-methylimidazole to water in step one is 1g:(313-500)mL. The other aspects are the same as the first embodiment.

[0033] Specific embodiment three: The present embodiment is different from the first or second embodiment in that the aging in step one is specifically aging at a temperature of 24-26°C for 8-10h. The other aspects are the same as the first or second embodiment.

[0034] Specific embodiment four: The present embodiment is different from the first to third embodiments in that the centrifugal separation in step one is specifically centrifugal separation at a speed of 6000-8000rpm. The other aspects are the same as the first to third embodiments.

[0035] Specific embodiment five: The present embodiment is different from the first to fourth embodiments in that the washing and drying in step one are specifically washing with anhydrous ethanol and ultrapure water, and then vacuum drying at a temperature of 60-80°C for 8-10h. The other aspects are the same as the first to fourth embodiments.

[0036] Specific embodiment six: The present embodiment is different from the first to fifth embodiments in that the thermal treatment of the nanoflower-shaped Co3[Fe(CN)6]2precursor in step two is specifically thermal treatment in an air atmosphere at a temperature of 380-580°C for 1-1.5h. The other aspects are the same as the first to fifth embodiments.

[0037] Specific embodiment seven: An application of a Co-Fe PBA-derived Co / Fe-based oxide nanoflower material, which is used to prepare a humidity-sensitive element for humidity detection.

[0038] Specific embodiment eight: The present embodiment is different from the seventh embodiment in that the humidity-sensitive element is prepared according to the following steps:

[0039] The Co-Fe PBA derived Co / Fe-based oxide nanoflower material is ground, then anhydrous ethanol is added dropwise and the grinding is continued, to obtain a slurry, the slurry is uniformly coated on the interdigital electrode of the substrate, and finally dried and aged to obtain a humidity sensor. The other aspects are the same as Embodiment Seven.

[0040] Embodiment Nine: Different from one of Embodiments Seven or Eight, the substrate is Al2O3 ceramic. The other aspects are the same as Embodiments Seven or Eight.

[0041] Embodiment Ten: Different from one of Embodiments Seven to Nine, the drying is specifically at a temperature of 70-80°C for 4-8h, and the aging treatment is specifically in a saturated salt solution with a relative humidity of 97% for 20-24h. The other aspects are the same as Embodiments Seven to Nine.

[0042] The beneficial effects of the present application are verified by the following examples:

[0043] Example One:

[0044] A preparation method of a Co-Fe PBA derived Co / Fe-based oxide nanoflower material, which is carried out according to the following steps:

[0045] I. 0.08g of 1-butyl-3-methylimidazolium bromide is added to 30mL of water, and magnetically stirred until completely dissolved, then 0.03g of K3[Fe(CN)]6 is added, and magnetically stirred at a speed of 220rpm for 30min to obtain a yellow-green clear solution, 0.02g of cobalt(II) acetylacetonate is added to the yellow-green clear solution, and magnetically stirred at a speed of 220rpm for 2h to obtain a dark green suspension, the dark green suspension is sequentially aged, centrifuged, washed and dried to obtain a nanoflower-shaped Co3[Fe(CN)6]2 precursor;

[0046] II. The nanoflower-shaped Co3[Fe(CN)6]2 precursor is heat-treated at an air atmosphere and a temperature of 380°C for 1h to obtain a Co-Fe PBA derived Co / Fe-based oxide nanoflower material, i.e. a Co3O4 / Fe2O3 nanoflower material.

[0047] The aging in Step I is specifically at a temperature of 25±1°C for 8h.

[0048] The centrifugation in Step I is specifically at a speed of 6000rpm.

[0049] The washing and drying in step one are specifically washing three times with anhydrous ethanol and ultrapure water, respectively, and drying under vacuum at 70°C for 8h.

[0050] Example 2: Application of a Co-Fe PBA-derived Co / Fe-based oxide nanoflower material, which is used to prepare a humidity-sensitive element for humidity detection.

[0051] The preparation of the humidity-sensitive element is specifically performed according to the following steps:

[0052] The Co-Fe PBA-derived Co / Fe-based oxide nanoflower material prepared in Example 1 is ground, and then anhydrous ethanol is added dropwise for further grinding to obtain a slurry. The slurry is uniformly coated on the interdigital electrodes of a substrate (interdigital electrode spacing: 50μm, electrode size: 9.4mm×9.4mm×0.38mm), and finally dried and aged to obtain a humidity-sensitive element.

[0053] The substrate is Al2O3 ceramic; the drying is specifically performed at 70°C for 8h; and the aging treatment is specifically performed in a saturated salt solution with a relative humidity of 97% for 24h.

[0054] Humidity performance test: Different saturated salt solutions are sealed in 2.5L jars for at least 24h to obtain different relative humidities. The LiBr, LiCl, CH3COOK, MgCl2, K2CO3, Mg(NO3)2, NaBr, KI, NaCl, KCl and Pb(NO3)2 saturated salt solutions correspond to relative humidities of 6%, 11%, 23%, 33%, 43%, 54%, 69%, 75%, 84% and 97%, respectively. In a typical humidity test, the humidity-sensitive element is first placed in a 6% relative humidity bottle to obtain a stable impedance value, and then quickly transferred to other relative humidity bottles (11%, 23%, 33%, 43%, 54%, 69%, 75%, 84% or 97%), and finally returned to the 6% relative humidity bottle after the test. The impedance change during the entire test process is recorded by a TH2829C LCR digital bridge, and all tests are performed at room temperature (25±1°C).

[0055] The sensitivity calculation formula is S=R 6％ / R 97％ . Wherein, R 6％ represents the stable impedance value of the humidity-sensitive element in a 6% relative humidity, and R 97％ represents the stable impedance value of the humidity-sensitive element in a 97% relative humidity. The response time and recovery time correspond to the impedance value of the humidity sensor changing from R 6％ to R 6％ -90% (R6％ -R 97％ ) required time and impedance value after moving away from the measured humidity by R 97％ changes to R 97％ + 90% (R 6％ -R 97％ ) required time.

[0056] Figure 1 The scanning electron microscope image of the nanoflower Co3[Fe(CN)6]2 precursor prepared in Example Step 1. As can be seen from the figure, the product is a nanoflower morphology assembled by two-dimensional nanosheets.

[0057] Figure 2 The XRD spectrum of the nanoflower Co3[Fe(CN)6]2 precursor prepared in Example Step 1. As can be seen from the figure, all the diffraction peaks of the product are consistent with the standard card of Co3[Fe(CN)6]2·10H2O (JCPDS NO. 46-0907) in the library, without impurity peaks, indicating that the product is also pure phase Co3[Fe(CN)6]2·10H2O.

[0058] Figure 3 The scanning electron microscope image of the Co3O4 / Fe2O3 nanoflower material prepared in Example Step 2. As can be seen from the figure, the calcined product still well maintains the morphology of the precursor.

[0059] Figure 4 The XRD spectrum of the Co3O4 / Fe2O3 nanoflower material prepared in Example Step 2. As can be seen from the figure, the diffraction peak position is consistent with Co3O4 (JCPDS NO. 42-1467) and γ-Fe2O3 (JCPDS NO. 39-1346) in the JCPDS database, indicating that the sintered product is a composite metal oxide composed of Co3O4 and γ-Fe2O3.

[0060] Figure 5 The response and recovery curve of the humidity-sensitive element prepared in Example 2 in the range of 6% to 97% humidity; Figure 6 The hysteresis curve of the humidity-sensitive element prepared in Example 2. As can be seen from the figure, the element shows excellent humidity-sensitive performance at room temperature (25℃). In the conversion process of 6% RH and 97% RH, the response time is 0.56 s, the recovery time is 9.35 s, the sensitivity is 1757, and the hysteresis value is 0.65%. The Co3O4 / Fe2O3 nanoflower composite material can realize rapid and effective measurement of humidity in the range of 6% to 97% humidity.

Claims

1. A method for preparing Co / Fe-based oxide nanoflower materials derived from Co-Fe PBA, characterized in that... It is done in the following steps:

1. Add 1-butyl-3-methylimidazole bromide to water and stir magnetically until completely dissolved. Then add K3[Fe(CN)]6 and stir magnetically to obtain a clear yellow-green solution. Add cobalt(II) acetylacetonate to the clear yellow-green solution and stir magnetically to obtain a dark green suspension. The dark green suspension is then aged, centrifuged, washed, and dried to obtain a nano-flower-like Co3[Fe(CN)6]2 precursor. The mass ratio of 1-butyl-3-methylimidazolium bromide to K3[Fe(CN)]6 is 1:(0.25~0.63); the mass ratio of 1-butyl-3-methylimidazolium bromide to cobalt(II) acetylacetonate is 1:(0.12~0.5).

2. Under air atmosphere and temperature of 380℃~580℃, the nanoflower-like Co3[Fe(CN)6]2 precursor was heat-treated for 1h~1.5h to obtain Co / Fe-based oxide nanoflower materials derived from Co-Fe PBA. The Co-Fe PBA-derived Co / Fe-based oxide nanoflower material is a composite metal oxide composed of Co3O4 and γ-Fe2O3.

2. The method for preparing a Co / Fe-based oxide nanoflower material derived from Co-Fe PBA according to claim 1, characterized in that... The mass ratio of 1-butyl-3-methylimidazole bromide to water in step one is 1 g:(313~500) mL.

3. The method for preparing a Co / Fe-based oxide nanoflower material derived from Co-Fe PBA according to claim 1, characterized in that... The aging process described in step one specifically involves aging at a temperature of 24℃~26℃ for 8h~10h.

4. The method for preparing a Co / Fe-based oxide nanoflower material derived from Co-Fe PBA according to claim 1, characterized in that... The centrifugation described in step one is specifically performed at a rotation speed of 6000 rpm to 8000 rpm.

5. The method for preparing a Co-Fe PBA-derived Co / Fe-based oxide nanoflower material according to claim 1, characterized in that... The washing and drying process described in step one specifically involves washing with anhydrous ethanol and ultrapure water respectively, followed by vacuum drying at a temperature of 60℃~80℃ for 8h~10h.

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