Metal organic framework composite film based on thermoelectric effect, flexible temperature sensor and preparation method of flexible temperature sensor

Abstract

The invention belongs to the technical field of flexible sensors, and particularly relates to a metal organic framework composite film based on a thermoelectric effect, a flexible temperature sensor and a preparation method of the flexible temperature sensor. According to the method, Ni3 (HITP) 2 nanoparticles are grown in situ on a single-walled carbon nanotube, and the MOFs-based thermoelectric composite film is obtained. According to the invention, Ni3 (HITP) 2 and SWCNT are adopted as raw materials, Ni3 (HITP) 2 grows on SWCNT in situ, so that the preparation of a flexible metal organic framework composite film with high Seebeck coefficient and high conductivity is realized, the flexible metal organic framework composite film is used for temperature sensing, the preparation of a metal organic framework material-based temperature sensor with high mechanical flexibility, high Seebeck coefficient and high conductivity is realized, and the preparation of the flexible metal organic framework material-based temperature sensor with high mechanical flexibility, high Seebeck coefficient and high conductivity is realized. For example, the sensitivity can reach 44.7 [mu] V / K.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible sensors, and in particular relates to a metal-organic framework composite film based on thermoelectric effect, a flexible temperature sensor and a preparation method thereof. Background Art

[0002] As a core indicator of metabolic activity and environmental adaptability, temperature sensing plays an irreplaceable role in applications such as analyzing plant photosynthetic efficiency, studying animal circadian rhythms, and monitoring human health. The development of wearable devices has placed higher demands on temperature sensing devices, necessitating innovative solutions that combine flexibility, lightweightness, and comfort. Furthermore, current flexible temperature sensors face technical bottlenecks in achieving high-precision continuous monitoring, including insufficient long-term sensing stability and measurement accuracy. Against this backdrop, temperature sensing technology based on the thermoelectric effect offers unique advantages. It directly converts temperature into an electrical signal through the thermoelectric effect. Compared to traditional rigid temperature measurement devices (such as fragile and highly toxic mercury thermometers and infrared thermometers limited by line-of-sight transmission), its core advantages lie in its structural flexibility, lightweightness, zero-power operation, and environmentally friendly monitoring capabilities. This provides a new technical approach for addressing the temperature sensing needs of flexible electronic devices in applications such as medical diagnostics and exercise physiology monitoring. Temperature sensors based on the thermoelectric effect require both high conductivity and a high Seebeck coefficient to achieve long-term, stable, and highly sensitive temperature sensing.

[0003] Metal-organic frameworks (MOFs) have shown great research value in the field of thermoelectric temperature sensing materials due to their low lattice thermal conductivity characteristics endowed by their periodic microporous structures. However, due to the energy level matching problem between the metal center and the organic ligand, most MOFs materials exhibit electrical insulating properties, with electrical conductivity generally below 10 -12 S cm -1 The low electrical conductivity and conventional powder morphology of MOFs materials limit their application in the field of thermoelectric temperature sensing.

[0004] To date, researchers have attempted to improve the conductivity, flexibility, and Seebeck coefficient of MOFs through various methods. These include effectively enhancing the conductivity of metal-organic frameworks by promoting metal-ligand charge transfer or introducing redox-active guest molecules to create new charge transfer pathways; increasing the Seebeck coefficient by manipulating the shape of the density of states at the Fermi level of MOFs; and using flexible substrates to enhance sensor flexibility.

[0005] For example, Lu et al. proposed a strategy to precisely adjust the interlayer electronic coupling in two-dimensional MOFs by controlling the interlayer spacing through side chain induction. By designing a π-conjugated 2,3,7,8,12,13-hexamethylenediaminetriindole (HATI) ligand, they were able to modify the nitrogen atom of the indole with alkyl chains of varying steric volume. They then synthesized a series of triindole-based two-dimensional MOFs. By precisely adjusting the interlayer spacing, they were able to effectively improve the Seebeck coefficient of two-dimensional MOF thermoelectric materials. However, the preparation of MOF-based temperature sensors that combine high mechanical flexibility with a high Seebeck coefficient and high electrical conductivity through a simple process remains a challenge. Summary of the Invention

[0006] The purpose of the present invention is to provide a metal organic framework composite film based on thermoelectric effect, a flexible temperature sensor and a preparation method thereof, and to achieve a temperature sensor with both high Seebeck coefficient and high conductivity.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A metal organic framework composite film based on thermoelectric effect is obtained by in-situ growing Ni3(HITP)2 nanoparticles on single-walled carbon nanotubes.

[0009] Furthermore, the process of in situ growth of Ni3(HITP)2 nanoparticles on single-walled carbon nanotubes is as follows: first, single-walled carbon nanotubes SWCNTs are dispersed in deionized water, and then nickel chloride hexahydrate and 2,3,6,7,10,11-hexamidinitibenzenehexahydrochloride are added in sequence, and Ni3(HITP)2 nanoparticles are in situ grown on the surface of SWCNTs at 55-75°C; after the reaction is completed, the reaction solution is filtered and dried to obtain the metal organic framework composite film.

[0010] The concentration of single-walled carbon nanotubes is no more than 0.5 mg / mL.

[0011] Furthermore, single-walled carbon nanotubes SWCNT and polyvinyl pyrrolidone PVP are dispersed in deionized water, and the amount of PVP used is 40%-60% of the mass of SWCNT.

[0012] Furthermore, the amount of single-walled carbon nanotubes SWCNT used is 10-60% of the nickel chloride hexahydrate, and the mass amount of 2,3,6,7,10,11-hexamidinitibenzene hexahydrochloride used is 1.4-1.6 times the mass of nickel chloride hexahydrate.

[0013] Preferably, the amount of single-walled carbon nanotubes SWCNT used is 40% of the nickel chloride hexahydrate.

[0014] Specifically, PVP and SWCNT are fully dispersed in deionized water; nickel chloride hexahydrate and 2,3,6,7,10,11-hexamidinitibenzene hexahydrochloride are added and fully dissolved; the pH value is adjusted to 10-11 by stirring, and then reacted in a 65° C. water bath for 3.5-6.5 hours, and finally filtered into a thin film and dried at no higher than 60° C.

[0015] The water bath reaction time is preferably 5 h.

[0016] The composite film can be used to prepare a metal organic framework-based flexible temperature sensor based on the thermoelectric effect.

[0017] The present invention further provides a method for preparing a metal-organic framework-based flexible temperature sensor based on the thermoelectric effect, wherein a PDMS prepolymer and a curing agent are mixed to prepare a precursor, which is poured onto a composite film. After curing, a single-sided PDMS-encapsulated SWCNT / Ni3(HITP)2 film is obtained; and a conductive material is connected to obtain a SWCNT / Ni3(HITP)2 temperature sensor.

[0018] The mass ratio of the PDMS prepolymer to the curing agent can be 10:1.

[0019] Ni3(HITP)2 is a two-dimensional conductive metal-organic framework (2D c-MOFs) with an electronic structure and in-plane conjugated transport pathway similar to graphene. It constructs a unique carrier transport structure through a planar coordination network of metal ions and organic ligands, which can significantly improve carrier concentration and carrier mobility. The conductivity of Ni3(HITP)2 is about 2s·cm -1 Although it is higher than general MOFs materials, it is also in powder state.

[0020] Ni3(HITP)2 particles have a particle size between 10 and 100 nm, similar to single-walled carbon nanotubes. This invention leverages the advantages of similarly sized nanomaterials, which can achieve synergistic enhancements in multiple properties (such as electrical and mechanical properties) when combined. In the field of thermoelectrics, similarly sized nanomaterials can also optimize the transmission paths of phonons and carriers, improving energy conversion efficiency.

[0021] In addition, the present invention creatively grows Ni3(HITP)2 nanoparticles in situ on single-walled carbon nanotubes, which not only solves the problem of poor conductivity of Ni3(HITP)2, but also increases the Seebeck coefficient of the material based on the energy filtering effect, improves the transport of carriers, and thus achieves enhanced thermoelectric performance; at the same time, the thermoelectric composite film also inherits the flexibility of the single-walled carbon nanotube film, realizing the preparation of metal-organic framework material-based temperature sensors with high mechanical flexibility, high Seebeck coefficient and high electrical conductivity.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The present invention uses Ni3(HITP)2 and SWCNT as raw materials, and realizes the preparation of a flexible metal-organic framework composite film with both high Seebeck coefficient and high conductivity by in-situ growing Ni3(HITP)2 on SWCNT. It uses it for temperature sensing, and realizes the preparation of a metal-organic framework material-based temperature sensor with high mechanical flexibility, high Seebeck coefficient and high conductivity, for example, its sensitivity can reach 44.7μV / K. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 a is a physical picture of pure Ni3(HITP)2 powder, and b is a physical picture of the flexible SWCNT / Ni3(HITP)2 film obtained in Example 1;

[0025] Figure 2 a and a' are electron microscope images of Ni3(HITP)2 nanoparticles; b and b' are electron microscope images of single-walled carbon nanotubes; c and c' are scanning electron microscope images of SWCNT / Ni3(HITP)2 obtained by in situ growth of Ni3(HITP)2 on SWCNT; it can be seen that Ni3(HITP)2 is successfully and uniformly grown on SWCNT;

[0026] Figure 3 The Seebeck coefficients of the films obtained with different SWCNT addition ratios in the examples;

[0027] Figure 4 The sensing sensitivity of the temperature sensor prepared by using the SWCNT / Ni3(HITP)2 film of Example 1;

[0028] Figure 5 The conductivity of the films obtained with different SWCNT addition ratios in the examples is shown. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0030] The specific sources of materials used in the embodiments of the present invention are as follows, but other commercially available products can also achieve the effects of the corresponding embodiments:

[0031] Carboxylated single-walled carbon nanotubes (length 5-30 μm, diameter 1-2 nm) were purchased from Zhongke Times Nanotechnology Co., Ltd.; 2,3,6,7,10,11-hexamidinitibenzene hexahydrochloride was purchased from Shanghai Adamas Reagent Co., Ltd.; nickel chloride hexahydrate was purchased from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; polyvinylpyrrolidone (K29-30) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; and polydimethylsiloxane (PDMS-Sylgard 184) was purchased from Dow Corning Corporation, USA.

[0032] Example 1

[0033] Preparation of a metal organic framework based SWCNT / Ni3(HITP)2 film based on thermoelectric effect:

[0034] 2.4 mg of PVP and 6 mg of SWCNTs were added to 60 mL of deionized water and ultrasonically dispersed for 60 minutes. 15 mg of nickel chloride hexahydrate and 22.5 mg of 2,3,6,7,10,11-hexaaminotriphenyl hexahydrochloride were then dissolved in the solution with stirring and ultrasonically dispersed for 60 minutes. 900 μL of ammonia was added while stirring, and the mixture was then reacted in a 65°C waterbath for 5 hours. Finally, the mixture was filtered to form a thin film and dried at 60°C to obtain a SWCNT / Ni3(HITP)2 thin film.

[0035] Examples 2-6

[0036] The added amounts of SWCNTs were varied to 1.5 mg, 3 mg, 4.5 mg, 7.5 mg, and 9 mg, respectively, and the rest were the same as in Example 1.

[0037] Examples 7-8

[0038] The dosage of ammonia water was adjusted to 800 μL and 1000 μL respectively, and the rest was the same as in Example 1.

[0039] Example 9

[0040] The reaction time in a 65° C. water bath was adjusted to 3.5 h, and the rest was the same as in Example 1.

[0041] Example 10

[0042] The reaction time in a 65° C. water bath was adjusted to 6.5 h, and the rest was the same as in Example 1.

[0043] Comparative Example 1

[0044] Carboxyl-functionalized SWCNTs (2 mg), THT (42 mg), and NiCl2·6H2O (36 mg) were placed in an autoclave, and a mixture of chlorobenzene (5 mL) and ethanol (5 mL) was added. The mixture was reacted at 100°C under argon for 48 hours. The resulting suspension was filtered, rinsed several times with anhydrous ethanol (30 mL) and deionized water (30 mL), and then dried under vacuum at 60°C for 2 hours to obtain a SWCNT@Ni-THT (SWCNTs 4 wt%) thin film.

[0045] Comparative Example 2

[0046] 2,3,6,7,10,11-Hexamidinitibenzenehexahydrochloride and NiCl2·6H2O were dissolved in deionized water. The mixture was reacted at 65°C for 45 minutes under continuous bubbling, followed by reaction at 65°C for 2 hours under N2. The resulting black precipitate was washed with water, ethanol, and acetone and dried in vacuo at 40°C. SWCNTs and sodium dodecylbenzenesulfonate were dispersed in dimethyl sulfoxide (DMSO) at a weight ratio of 1:5. The synthesized Ni3(HITP)2 powder was then added to the prepared SWCNT solution. The mixture was sonicated for 5 minutes and filtered. After thorough washing with DMSO and ethanol, the mixture was dried in a vacuum oven at 40°C to obtain a black Ni3(HITP)2 / SWCNT powder. The powder was pressed at 20 MPa for 15 minutes (D = 12.7 mm) to obtain a rigid pellet for subsequent measurements.

[0047] Sensor production:

[0048] The PDMS prepolymer and curing agent were mixed in a 10:1 mass ratio in a beaker, stirred thoroughly, and then vacuum-degassing for 30 minutes. The SWCNT / Ni3(HITP)2 film obtained in Example 1 was fixed to a stainless steel substrate. The prepared PDMS precursor was poured onto the filter membrane. After self-leveling, the film was cured at 80°C for 60 minutes to obtain a single-sided PDMS-encapsulated SWCNT / Ni3(HITP)2 film.

[0049] The SWCNT / Ni3(HITP)2 film obtained above was cut into a size of 1 cm×5 cm. A conductive silver paste with a width of about 0.5 cm was evenly coated on both ends of the SWCNT / Ni3(HITP)2 film (the side not encapsulated by PDMS). After the solvent of the silver paste evaporated and solidified, a conductive tape was attached to obtain a SWCNT / Ni3(HITP)2 temperature sensor.

[0050] The Seebeck coefficient (temperature sensing sensitivity) of the films or pressed sheets obtained in the Examples and Comparative Examples, as well as the corresponding temperature sensors, was tested and data collected using a semiconductor temperature controller and a DAQ data acquisition system. The two ends of the sample were placed on the high and low temperature platforms of the semiconductor temperature controller, respectively. A temperature differential was created across the sample by varying the temperatures of the two platforms. During the test, the DAQ data acquisition system measured and recorded the sample output voltage. The slope of the output voltage relative to the temperature differential was the Seebeck coefficient (temperature sensing sensitivity).

[0051] Sensing response mechanism: SWCNT / Ni3(HITP)2 temperature sensor realizes temperature sensing based on Seebeck effect. When there is a temperature difference (ΔT) across the thermoelectric material, a thermoelectric voltage (V t In actual application scenarios, when one end of the sensor maintains a constant temperature (T0), the temperature to be measured at the other end (T s ) can be obtained by the formula “T s =T0+V t / S T ” indicates that temperature sensing can be achieved.

[0052] Table 1 shows the properties of different films or tablets obtained in Example 1 and Comparative Examples 1-2.

[0053] Table 1

[0054]

[0055] Table 2 shows the Seebeck coefficients of the films obtained in Examples 1-6 using different SWCNT contents (the content is the ratio of the mass of SWCNT to nickel chloride hexahydrate).

[0056] Table 2

[0057]

[0058] from Figure 3 、 Figure 4 It can be seen that with the increase of SWCNT addition, the Seebeck coefficient of the film first increases and then decreases. When the SWCNT content is 40%, the Seebeck coefficient is the highest and the sensor sensitivity is the highest.

[0059] Figure 4 The sensing sensitivity of the temperature sensor prepared using the SWCNT / Ni3(HITP)2 film of Example 1.

[0060] Table 3 shows the Seebeck coefficients of the films obtained in Example 1 and Examples 7 and 8 using different amounts of ammonia added.

[0061] Table 3

[0062]

[0063] Table 4 shows the Seebeck coefficients of the films obtained in Example 1 and Examples 9 and 10 using different water bath times.

[0064] Table 4

[0065]

[0066] The conductivity of the film was measured using the four-probe method. Figure 5 The conductivity of the film obtained by using different SWCNT addition ratios in the embodiment is shown; it can be seen that with the increase in the amount of SWCNT, the conductivity of the film is greatly improved, and low conductivity will cause large fluctuations in the sensor signal.

Claims

1. A method for preparing a metal-organic framework composite film based on thermoelectric effect, characterized in that: Ni3(HITP)2 nanoparticles were in situ grown on single-walled carbon nanotubes to obtain MOFs-based thermoelectric composite films.

2. The method for preparing a metal-organic framework composite film based on thermoelectric effect according to claim 1, wherein: The process of in-situ growth of Ni3(HITP)2 nanoparticles on single-walled carbon nanotubes is as follows: first, single-walled carbon nanotubes (SWCNTs) are dispersed in deionized water, and then nickel chloride hexahydrate and 2,3,6,7,10,11-hexamidinitibenzenehexahydrochloride are added in sequence, and Ni3(HITP)2 nanoparticles are in-situ grown on the surface of SWCNTs at 55-75°C; after the reaction is completed, the reaction solution is filtered and dried to obtain the metal-organic framework composite film.

3. The method for preparing a metal-organic framework composite film based on thermoelectric effect according to claim 2, characterized in that: The dosage of single-walled carbon nanotubes (SWCNTs) is 10-60% of nickel chloride hexahydrate, and the mass dosage of 2,3,6,7,10,11-hexamidinitibenzene hexahydrochloride is 1.4-1.6 times of the mass of nickel chloride hexahydrate.

4. The method for preparing a metal-organic framework composite film based on thermoelectric effect according to claim 3, characterized in that: The amount of single-walled carbon nanotubes (SWCNTs) used is 40% of nickel chloride hexahydrate.

5. The method for preparing a metal-organic framework composite film based on thermoelectric effect according to claim 2, wherein: Single-walled carbon nanotubes (SWCNTs) and polyvinyl pyrrolidone (PVP) are dispersed in deionized water, with the amount of PVP being 40%-60% of the mass of the SWCNTs.

6. The method for preparing a metal-organic framework composite film based on thermoelectric effect according to claim 5, characterized in that: The concentration of single-walled carbon nanotubes is no more than 0.5 mg / mL.

7. The method for preparing a metal-organic framework composite film based on thermoelectric effect according to any one of claims 1 to 6, characterized in that: Fully disperse PVP and SWCNT in deionized water; add nickel chloride hexahydrate and 2,3,6,7,10,11-hexamidinitibenzene hexahydrochloride and fully dissolve; stir and adjust the pH value to 10-11, then react in a 65°C water bath for 3.5-6.5 hours, finally filter into a thin film and dry at no more than 60°C.

8. A metal-organic framework composite film based on thermoelectric effect obtained by the preparation method according to any one of claims 1 to 7.

9. A metal organic framework based flexible temperature sensor based on thermoelectric effect, characterized in that: The flexible temperature sensor is prepared by using the composite film according to claim 8.

10. The method for preparing a metal organic framework-based flexible temperature sensor based on thermoelectric effect according to claim 9, characterized in that: The PDMS prepolymer and curing agent are mixed to prepare a precursor, which is poured onto the composite film. After curing, a single-sided PDMS-encapsulated SWCNT / Ni3(HITP)2 film is obtained; a conductive material is connected to obtain a SWCNT / Ni3(HITP)2 temperature sensor.

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