A humidity-induced spin-activated composite gel and its preparation method and application

Abstract

The present invention discloses a humidity-induced spin transition composite gel and its preparation method and application. The gel material includes PVDF, PEG, a spin transition material, and a moisture-absorbing material (SHM). The spin transition material is [Fe(1,3-bpp)2(NCS)2]2. The mass percentage of [Fe(1,3-bpp)2(NCS)2]2 with respect to PVDF is 20%. The mass percentage of the moisture-absorbing material SHM with respect to PVDF is 5% to 20%. The mass ratio of PEG to PVDF is 0.2 to 1:1 to 4. Under normal temperature and pressure, the composite gel materials doped with different proportions of the moisture-absorbing material achieve spin transition behaviors triggered by different humidities, and are simple to prepare, have stable properties, and have broad application potential in humidity detectors, sensors, digital displays, etc.

Description

Technical Field

[0001] The present invention relates to a composite gel and a preparation method and application thereof, and particularly relates to a humidity-induced spin-transition composite gel and a preparation method and application thereof. Background Art

[0002] Spin-transition materials refer to materials in which the electronic configuration of the central metal ion can switch between high-spin (HS) and low-spin (LS) states under external triggering conditions (such as temperature, pressure, light, magnetic field or other guest molecules). Both of these states have unique magnetic, electrical, mechanical and other physico-chemical properties. Therefore, this property endows spin-transition metal complexes with potential applications in information storage, sensors and digital displays, etc. As is well known, the most important thing for the occurrence of spin-transition materials is external perturbation. Generally speaking, the most common ones are temperature and pressure changes, or additional provision of light, magnetic field or absorption of guests. However, the existence of these conditions requires additional energy consumption. Atmospheric humidity is a large and widespread energy field. When the strategy of using humidity change to induce spin transition reduces additional energy consumption and expands the application scenarios of spin-transition materials on the one hand, on the other hand, it can achieve the induction of spin transition at room temperature and atmospheric pressure, increasing the practical application potential of spin-transition materials.

[0003] Considering the aspect of practical application, in order to be more conveniently concentrated on devices, the spin-transition states of solid or inorganic materials have been studied the most widely. However, the macroscopic behavior of bulk SCO materials is strongly affected by the electron-lattice coupling effect. In particular, the change in molecular volume and shape accompanying the spin state change leads to considerable elastic interactions between them. These interactions give rise to various cooperative phenomena, such as first-order phase transitions or self-accelerating relaxation. In this process, the size reduction effect of spin crossover materials is expected to occur. These situations result in the inability to effectively regulate the performance of spin crossover materials. Therefore, current research has begun to focus on the spin transition of soft materials (such as gels, thin films, etc.), because this kind of material is easier to process and orient than solids and liquids. On the other hand, gels, as negative carriers, can endow gels with new physico-chemical properties (optical, magnetic, electrical conductivity, etc.) by doping metal ions or other substances, increasing the possibility of using gel materials. Therefore, the formation of gels using metal-organic components or other substances can be used to manufacture materials with controlled and adjustable properties. Summary of the Invention

[0004] Objective of the Invention: The present invention aims to provide a humidity-induced spin-transition composite gel that can achieve spin-transition behavior at the molecular level under normal temperature and pressure conditions; another objective of the present invention is to provide a preparation method of the composite gel material, which is simple to operate and has mild conditions, enabling the humidity-triggered spin-transition behavior of solid-state materials with different doping ratios of moisture-absorbing materials without external energy; another objective of the present invention is to provide related applications of the composite gel material in humidity detection, which is expected to be applied to molecular electronic devices such as sensors and digital displays.

[0005] Technical Solution: The composite gel material of the present invention includes PVDF, PEG, a spin-transition material [Fe(1,3-bpp) 2 (NCS) 2 2 and a moisture-absorbing material, where the moisture-absorbing material is a two-dimensional van der Waals heterojunction material combined with 2D-Co([Co(NCS) 2 (pyz) 2 n ) and 2D-Zn([Zn(NCS) 2 (pyz) 2 n ), and pyz = pyrazine, referring to Patent CN111282545B.

[0006] Furthermore, the mass percentage of [Fe(1,3-bpp) 2 (NCS) 2 2 with respect to PVDF is 20%, and the mass percentage of the moisture-absorbing material with respect to PVDF is 5% - 20%; the mass ratio of PEG to PVDF is 0.2 - 1:1 - 4.

[0007] The preparation method of the composite gel material includes the following steps:

[0008] (1) Pour PEG into a solvent, ultrasonically dissolve it until it becomes transparent, and then add PVDF and stir until PVDF is completely dissolved and transparent, obtaining a colorless and transparent mixed sol I of PVDF and PEG;

[0009] (2) Under stirring conditions, add the spin-transition material [Fe(1,3-bpp) 2 (NCS) 2 2 and the moisture-absorbing material to the PVDF / PEG sol I obtained in the above step, heat and stir until it is evenly dispersed, obtaining a green sol II;

[0010] (3) Cool the sol II to room temperature, let it stand for degassing, and pour it into a mold for molding.

[0011] ​​​​​Further, the mass-volume ratio of PEG to the solvent in step (1) is 0.2-1 g: 10-30 mL.

[0012] Further, the solvent in step (1) is N,N-dimethylformamide; the dissolution condition of PEG is: ultrasonic for 8-18 min at 30-60 °C and 20-60 kHz until PEG is completely dissolved and transparent; the dissolution condition of polyvinylidene fluoride is: stir at 100-500 rpm for 0.5-2 h until PVDF is completely dissolved and transparent.

[0013] Further, the heating and stirring temperature in step (2) is 85-95 °C, the stirring speed is 100-500 rpm, and the stirring time is 5-10 h.

[0014] The composite gel material can be applied to humidity detection. After the composite gel material absorbs moisture, its color changes from green to yellow.

[0015] Advantages: Compared with the prior art, the present invention has the following remarkable advantages: (1) The composite gel material provided by the present invention has good performance, is non-toxic and can exist stably; (2) The composite gel material provided by the present invention combines the advantages of moisture-absorbing materials, utilizes humidity triggering that is widely present and does not require additional energy supply, and can realize spin conversion behavior at the molecular level under normal temperature and pressure conditions; (3) The composite gel material is prepared by blending two polymers PVDF, PEG, a spin conversion complex and a moisture-absorbing material, and its preparation method is simple and flexible, and can be applied to other spin conversion complex systems; (4) The composite gel material can achieve spin state conversion under normal temperature and pressure at different doping ratios of the moisture-absorbing material (SHM), can simply realize the spin conversion phenomenon under environmental conditions, and can be applied in molecular electronic devices such as humidity detection, sensors and digital displays. Description of the Drawings

[0016] Figure 1 It is a color change diagram of the composite gel at different adsorption times under an environment with a relative humidity of 98%;

[0017] Figure 2 It is the solid ultraviolet-visible absorption spectrum of the humidity-triggered spin conversion gel material SHM@Fe@PVDF / PEG at different times. Detailed Embodiments

[0018] The technical solution of the present invention will be further described below in conjunction with the drawings.

[0019] Example 1

[0020] The composite gel material includes PVDF, PEG, a spin conversion material [Fe(1,3-bpp)2 (NCS) 2 2 and the moisture-absorbing material SHM (2D-Co([Co(NCS) 2 (pyz) 2 n ) and 2D-Zn([Zn(NCS) 2 (pyz) 2 n )-bonded two-dimensional van der Waals heterojunction material, pyz = pyrazine, see Patent CN 111282545 B), the [Fe(1,3-bpp) 2 (NCS) 2 2 The mass percentage of [Fe(1,3-bpp)(NCS)] with respect to PVDF is 20%, and the mass percentage of the moisture-absorbing material with respect to PVDF is 5%. The preparation method is as follows:

[0021] (1) Preparation of PVDF / PEG sol I: At room temperature (25 °C), 0.45 g of polyethylene glycol (PEG, Mw ~ 6000) was loaded into a 50 mL three-necked flask, 15 mL of N,N-dimethylformamide (DMF) was poured into the flask, and ultrasonication was carried out at 40 °C and 50 kHz for 10 min until PEG was completely dissolved and transparent. Then, 2 g of polyvinylidene fluoride (PVDF, Mw ~ 50000) was added, and stirring was carried out at 500 rpm for 3 h until PVDF was completely dissolved and transparent, obtaining a colorless and transparent mixed sol of PVDF and PEG, PVDF / PEG sol I;

[0022] (2) Under the stirring condition of 300 rpm, 0.4 g of the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 (the preparation method refers to Chinese Patent 2018108260382) and 0.1 g of the moisture-absorbing material (SHM) were added to the PVDF / PEG sol I obtained in step (1), and stirring was carried out for 1 h. Then, the flask was transferred to an oil bath at 95 °C and stirring was continued at 300 rpm for 6 h until the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 and the moisture-absorbing material SHM were uniformly dispersed, obtaining a green and transparent SHM@Fe@PVDF / PEG sol II;

[0023] ​​​​​​(3) Remove the flask, cool it to room temperature (20 °C), let it stand for degassing, and then pour Sol II into a cylindrical mold with a diameter of 2 mm and a height of 4 mm and let it stand for 24 hours to obtain a green transparent SHM@Fe@PVDF / PEG gel material doped with spin transition complex SCO and moisture-absorbing material SHM.

[0024] The composite gel material SHM@Fe@PVDF / PEG prepared in this example, in which the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 The mass percentage of PVDF is 20%, and the mass percentage of the moisture-absorbing material SHM with respect to PVDF is 5%.

[0025] Perform ultraviolet-visible absorption spectroscopy measurement on it (the laser selected for the light illumination experiment is a 230 W Hg arc lamp with a 310 ± 5 nm band-pass filter, the wavelength is 980 nm, and the power is 1.5 W cm -2 ), and the specific measurement process is as follows: Take 2 g of the SHM@Fe@PVDF / PEG gel material, place it in an environment with a humidity of 98%, and perform solid ultraviolet-visible absorption spectroscopy measurement in the time range of 0 - 120 min at intervals of 10 min. The change of the solid ultraviolet-visible absorption spectrum of the sample with the moisture absorption time is as Figure 2 shown. After observing the moisture absorption, the color of the composite gel gradually changes from the original green to yellow ( Figure 1 ), the solvent-mediated intra-ligand π–π * transitions and d-d transitions of low-spin Fe(II) increase, while the transition from d(Fe) π +π(NCS) to π*(1,3-bpp) decreases, indicating a typical humidity-triggered transition from the high-spin state to the low-spin state ( Figure 2 ). Thus, it can be seen that the composite gel material obtained by the method of the present invention is convenient for practical applications and can be applied to molecular electronic devices such as humidity detection, molecular switches, and molecular displays.

[0026] Example 2

[0027] The composite gel material includes PVDF, PEG, spin transition material [Fe(1,3-bpp) 2 (NCS) 2 2 and moisture-absorbing material SHM. The mass percentage of [Fe(1,3-bpp) 2 (NCS) 2 2 with respect to PVDF is 20%, and the mass percentage of the moisture-absorbing material with respect to PVDF is 10%. The preparation method is as follows: ​​​

[0028] (1) Preparation of PVDF / PEG Sol I: At room temperature (25 °C), 0.45 g of polyethylene glycol (PEG, Mw ~ 6000) was loaded into a 50 mL three-necked flask. 30 mL of N,N-dimethylformamide (DMF) was poured into the flask. Under the conditions of 40 °C and 50 kHz, it was ultrasonically treated for 10 min until PEG was completely dissolved and became transparent. Then, 4 g of polyvinylidene fluoride (PVDF, Mw ~ 50000) was added, and it was stirred at 500 rpm for 3 h until PVDF was completely dissolved and became transparent, obtaining a colorless and transparent mixed sol of PVDF and PEG, namely PVDF / PEG Sol I;

[0029] (2) Under the stirring condition of 300 rpm, 0.4 g of spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 (The preparation method refers to Chinese Patent 2018108260382) and 0.2 g of moisture-absorbing material were added to the PVDF / PEG Sol I obtained in step (1), and it was stirred for 3 h. Then, the flask was transferred to an oil bath at 95 °C and continued to be stirred at 300 rpm for 6 h until the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 and the moisture-absorbing material were uniformly dispersed, obtaining a green and transparent SHM@Fe@PVDF / PEG Sol II;

[0030] (3) The flask was removed, cooled to room temperature (25 °C), allowed to stand for degassing, and then the Sol II was poured into a cylindrical mold with a diameter of 3 mm and a height of 4 mm and allowed to stand for 24 hours, obtaining a green 2 (NCS) 2 2 SHM-doped gel material SHM@Fe@PVDF / PEG of the spin transition complex [Fe(1,3-bpp)

[0031] In this example, the obtained SHM@Fe@PVDF / PEG gel material SHM@Fe@PVDF / PEG, the mass percentage of the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 with respect to PVDF is 20%, and the mass percentage of the moisture-absorbing material SHM with respect to PVDF is 10%. This spin crossover gel material SHM@Fe@PVDF / PEG is applied to molecular electronic devices such as humidity detection, molecular switches, and molecular displays.

[0032] Example 3

[0033] ​​​​The composite gel material includes PVDF, PEG, a spin transition material [Fe(1,3-bpp) 2 (NCS) 2 2 and a moisture-absorbing material SHM. The mass percentage of [Fe(1,3-bpp) 2 (NCS) 2 2 with respect to PVDF is 20%, and the mass percentage of the moisture-absorbing material with respect to PVDF is 20%. The preparation method is as follows:

[0034] (1) Preparation of PVDF / PEG sol I: At room temperature (25 °C), 0.45 g of polyethylene glycol (PEG, Mw ~ 6000) was placed into a 50 mL three-necked flask, 30 mL of N,N-dimethylformamide (DMF) was poured into the flask, and ultrasonication was carried out at 40 °C and 50 kHz for 10 min until PEG was completely dissolved and transparent. Then, 2 g of polyvinylidene fluoride (PVDF, Mw ~ 50000) was added, and stirring was carried out at 500 rpm for 3 h until PVDF was completely dissolved and transparent, obtaining a colorless and transparent mixed sol of PVDF and PEG, PVDF / PEG sol I;

[0035] (2) Under the stirring condition of 500 rpm, 0.4 g of the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 (for the preparation method, see Chinese Patent 2018108260382) and 0.4 g of the moisture-absorbing material SHM were added to the PVDF / PEG sol I obtained in step (1), and stirring was carried out for 3 h. Then, the flask was transferred to an oil bath at 95 °C and stirring was continued at 300 rpm for 6 h until the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 and the moisture-absorbing material SHM were uniformly dispersed, obtaining a green and transparent SHM@Fe@PVDF / PEG sol II;

[0036] (3) The flask was removed, cooled to room temperature (25 °C), allowed to stand for degassing, and then the sol II was poured into a cylindrical mold with a diameter of 3 mm and a height of 4 mm and allowed to stand for 24 hours, obtaining a green SHM@Fe@PVDF / PEG gel material doped with the spin transition SCO and the moisture-absorbing material SHM.

[0037] In this example, the obtained spin transition gel material SHM@Fe@PVDF / PEG, the spin transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 ​​​​​For a PVDF mass percentage of 20%, the moisture-absorbing material SHM has a mass percentage of 20% with respect to PVDF. The spin-transition gel material 20% SHM@Fe@PVDF / PEG is used in molecular electronic devices such as humidity detection, molecular switches, and molecular displays.

[0038] Comparative Example 1

[0039] The gel material was directly prepared without adding SHM. The method is as follows:

[0040] (1) Step (1) is the same as in Example 1.

[0041] (2) Under stirring conditions of 300 rpm, 0.4 g of the spin-transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 (The preparation method refers to Chinese Patent 2018108260382) was added to the PVDF / PEG sol I obtained in step (1), stirred for 1 h, and then the flask was transferred to an oil bath at 95 °C and stirred continuously at 300 rpm for 6 h until the spin-transition complex [Fe(1,3-bpp) 2 (NCS) 2 2 was uniformly dispersed to obtain a transparent Fe@PVDF / PEG sol II. As a result, in the obtained Fe@PVDF / PEG gel material, the doped Fe@PVDF / PEG was uniformly dispersed in the PVDF gel.

[0042] (3) Step (3) is the same as in Example 1.

[0043] The Fe@PVDF / PEG gel material obtained in this example was placed in an environment with a humidity of 98% at normal temperature and pressure, and the humidity did not cause the spin-transition behavior of the gel material Fe@PVDF / PEG.

[0044] Comparative Example 2

[0045] The gel material was directly prepared without adding the spin-transition complex. The method is as follows:

[0046] (1) Step (1) is the same as in Example 1.

[0047] ​​(2) Under the stirring condition of 300 rpm, 0.1 g of the moisture-absorbing material SHM was added to the PVDF / PEG sol I obtained in step (1), and stirred for 3 h. Then, the flask was transferred to an oil bath at 95 °C and continued to be stirred at 300 rpm for 6 h until the moisture-absorbing material SHM was evenly dispersed to obtain a transparent SHM-PVDF / PEG sol II. In the obtained SHM-PVDF / PEG gel material, the doped SHM-PVDF / PEG was evenly dispersed in the PVDF gel.

[0048] (3) Step (3) is the same as that in Example 1.

[0049] The SHM-PVDF / PEG gel material obtained in this example was placed in an environment with a humidity of 98% at normal temperature and pressure, and the humidity did not cause the spin transition behavior of the gel material SHM-PVDF / PEG.

[0050] According to the results of Comparative Example 1 and Comparative Example 2, SHM was selected as the moisture-absorbing material in the sample in the present invention.

[0051] [Fe(1,3-bpp) 2 (NCS) 2 2 As the spin transition complex SCO, the preparation of the humidity-induced spin transition composite gel was thus realized.​

Claims

1. A composite gel material comprising PVDF, PEG and a spin-cured material [Fe(1,3-bpp)2(NCS)2]2, characterized in that: The gel material also includes a hygroscopic material, wherein the hygroscopic material is 2D-Co ([Co(NCS)2(pyz)2] n ) and 2D-Zn ([Zn(NCS)2(pyz)2] n ), pyz=pyrazine, the mass percentage of [Fe(1,3-bpp)2(NCS)2]2 to PVDF is 20%, the mass percentage of the moisture-inducing material to PVDF is 5%~20%; the mass ratio of PEG to PVDF is 0.2~1:1~4; The preparation method of the composite gel material comprises: (1) Pour PEG into the solvent, ultrasonicate until PEG is completely dissolved and becomes transparent, then add PVDF and stir until PVDF is completely dissolved and becomes transparent, thereby obtaining a colorless and transparent mixed sol I of PVDF and PEG; (2) adding the spin-transducing material [Fe(1,3-bpp)2(NCS)2]2 and the hygroscopic material to the mixed sol I of PVDF and PEG obtained in the above step under stirring conditions, heating and stirring until the mixture is uniformly dispersed to obtain a green sol II; (3) Cool Sol II to room temperature, let it stand to degas, and then mold it.

2. A method for preparing the composite gel material according to claim 1, characterized in that: The method includes: (1) Pour PEG into the solvent, ultrasonicate until PEG is completely dissolved and becomes transparent, then add PVDF and stir until PVDF is completely dissolved and becomes transparent, thereby obtaining a colorless and transparent mixed sol I of PVDF and PEG; (2) adding the spin-transducing material [Fe(1,3-bpp)2(NCS)2]2 and the hygroscopic material to the mixed sol I of PVDF and PEG obtained in the above step under stirring conditions, heating and stirring until the mixture is uniformly dispersed to obtain a green sol II; (3) Cool Sol II to room temperature, let it stand to degas, and then mold it.

3. The method for preparing the composite gel material according to claim 2, characterized in that: The mass volume ratio of PEG to solvent in step (1) is 0.2-1 g:10-30 mL.

4. The method for preparing the composite gel material according to claim 2, characterized in that: The solvent in step (1) is N,N-dimethylformamide.

5. The method for preparing the composite gel material according to claim 2, characterized in that: The dissolution conditions of PEG in step (1) are: ultrasonication at 30-60°C and 20-60 kHz for 8-18 min until PEG is completely dissolved and becomes transparent; the dissolution conditions of polyvinylidene fluoride are: stirring at 100-500 rpm for 0.5-2 h until PVDF is completely dissolved and becomes transparent.

6. The method for preparing the composite gel material according to claim 2, characterized in that: The heating and stirring temperature in step (2) is 85-95°C.

7. The method for preparing the composite gel material according to claim 2, characterized in that: The stirring speed in step (2) is 100 to 500 rpm, and the stirring time is 5 to 10 hours.

8. An application of the composite gel material according to claim 1 in humidity detection.

9. The application of the composite gel material according to claim 8 in humidity detection is characterized in that: After the composite gel material absorbs moisture, the color changes from green to yellow.

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