CN111189887A - Humidity sensor and manufacturing method and application thereof - Google Patents

Humidity sensor and manufacturing method and application thereof Download PDF

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CN111189887A
CN111189887A CN202010023338.4A CN202010023338A CN111189887A CN 111189887 A CN111189887 A CN 111189887A CN 202010023338 A CN202010023338 A CN 202010023338A CN 111189887 A CN111189887 A CN 111189887A
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humidity
humidity sensor
substrate
preparation
film
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季俊廷
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China University of Petroleum East China
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China University of Petroleum East China
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/048—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance for determining moisture content of the material

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Abstract

The application provides a humidity sensor and a manufacturing method and application thereof, the humidity sensor utilizes graphite phase carbon nitride as a humidity sensing material, the humidity sensor comprises a substrate and a g-C combined on the substrate3N4A film, and a film connected to said g-C3N4The humidity sensor can measure the humidity in air within a range of 0-97%, the response time is only 0.3s, and the humidity sensor can be applied to nondestructive testing of paper products.

Description

Humidity sensor and manufacturing method and application thereof
Technical Field
The application belongs to the field of humidity sensing, and particularly relates to a humidity sensor and a manufacturing method and application thereof.
Background
Humidity is not closely classified with daily life, and a humidity sensor as a detection device plays an important role in the production and life of people, and in recent years, the humidity sensor has been successfully applied to various fields, such as meteorological measurement, medical care and health, and use protection of precision instruments.
Most of the materials used in humidity sensors include metal oxides, electrolytes, polymers, etc., and humidity sensors manufactured by using the above materials still have the problems of narrow measurement range, long response time, poor reversibility, etc.
Therefore, it is necessary and important to search for a new sensing material to manufacture an enhanced humidity sensor.
Disclosure of Invention
In order to solve the problems of narrow measurement range, long response time, poor reversibility and the like of the conventional humidity sensor, the application provides a method for utilizing a two-dimensional material, particularly graphite-phase carbon nitride (g-C)3N4) As a transmitterA humidity sensor for sensing a material, the humidity sensor comprising a substrate, a g-C bonded to the substrate3N4A film, and a film connected to said g-C3N4The humidity sensor can measure the humidity in air in a range of 0-97%, and the response time is only 0.3 s.
The present application aims to provide the following aspects:
in a first aspect, the present application provides the use of graphite phase carbon nitride for humidity indication.
In one implementation, the graphite phase carbon nitride is a graphite phase carbon nitride thin film.
In a second aspect, the present application provides a humidity sensor comprising a substrate, a g-C bonded to the substrate3N4A film, and a film connected to said g-C3N4And a resistance value detection device on the film.
In an implementable manner, the substrate includes a PCB board, flexible interdigitated electrodes, and the like.
Further, the g-C3N4The thickness of the film is 0.1 to 1 nm.
In one implementable manner, the humidity sensor is prepared by a method comprising the steps of:
preparation of g-C3N4Suspending liquid;
g to C3N4Coating the suspension on the substrate;
will be coated with g-C3N4Drying the substrate of the suspension;
and connecting the dried device with a resistance detection device.
Alternatively, the preparation g-C3N4The suspension comprises:
preparation of g-C3N4A solid;
g-C obtained by preparation3N4The solid is dispersed in a solvent.
Alternatively, preparation of g-C3N4The solid may comprise the steps of:
weighing raw materials;
heating the raw materials and preserving heat;
and cooling the system after heat preservation.
In a third aspect, the present application provides a method of manufacturing a humidity sensor according to the second aspect, the method comprising the steps of:
preparation of g-C3N4Suspending liquid;
g to C3N4Coating the suspension on the substrate;
will be coated with g-C3N4Drying the substrate of the suspension;
and connecting the dried device with a resistance detection device.
Alternatively, the preparation g-C3N4The suspension comprises:
preparation of g-C3N4A solid;
g-C obtained by preparation3N4The solid is dispersed in a solvent.
In a fourth aspect, the present application further provides a humidity sensing system, where the system includes the second aspect, the humidity sensor, the processor and the service terminal, and the processor receives the humidity information collected by the humidity sensor, processes the humidity information, and reports the processed humidity information to the service terminal.
In a fifth aspect, the application also provides the humidity sensor and the use of the humidity sensing system for humidity detection of diapers.
In a sixth aspect, the present application further provides the use of the moisture sensor and the moisture sensing system for non-destructive testing of paper products.
The graphite-phase carbon nitride is a mature two-dimensional material in the prior art, and the applicant finds the unique application of the graphite-phase carbon nitride in the field of humidity indication, can quickly, accurately and nondestructively indicate the environmental humidity and the humidity of industrial products such as paper products and the like, and has the characteristics of short response time, high accuracy, strong reversibility and the like.
Compared with the prior art, the humidity sensor using the graphite-phase carbon nitride as the indicating material has the advantages of simple structure, convenience in manufacturing, accurate humidity detection result, short response time, good reversibility and capability of realizing nondestructive detection, is applied to the humidity detection of paper cultural relics, can really realize the nondestructive detection of the cultural relics, and thus effectively protects the cultural relics.
Drawings
FIG. 1 shows the manufacture of g-C3N4A schematic of a humidity sensor flow path;
FIG. 2a shows g-C prepared by example3N4A nanostructure at a unit dimension of 10 μm;
FIG. 2b shows g-C prepared in example3N4A nanostructure at a unit scale of 1 μm;
FIG. 2C shows g-C prepared by example3N4A nano structure diagram with a unit dimension of 100 nm;
FIG. 2d shows g-C prepared by example3N4Nanostructures at a unit dimension of 200 nm;
FIG. 3 shows g-C prepared in example3N4An infrared spectrum of (1);
FIG. 4a shows g-C prepared by example3N4XRD spectrum of (1);
FIG. 4b shows g-C prepared by example3N4(ii) a full spectrum of XPS;
FIG. 4C shows g-C prepared by example3N4The high resolution XPS spectrum of C1 s;
FIG. 4d shows g-C prepared by example3N4The high resolution XPS spectrum of N1 s;
FIG. 5 illustrates a non-linear function of resistance as a function of relative humidity for a humidity sensor fabricated according to an embodiment;
FIG. 6 shows the real-time response and recovery of a g-C3N4 film sensor fabricated by an example;
FIG. 7 shows the resistance of the humidity sensor manufactured by the embodiment at 11-97% relative humidity;
FIG. 8 illustrates the fastest response time and recovery time for a humidity sensor made by an embodiment;
FIG. 9 shows the highest response at 97% RH for a humidity sensor made by an example;
FIG. 10 illustrates the resistance value variation of a humidity sensor due to humidity rise (relative humidity from 11% to 97%, up test) and humidity fall (relative humidity from 97% to 11%, down test);
FIG. 11 shows the hysteresis characteristics of the humidity sensor manufactured by the embodiment at a relative humidity of 11-97%;
FIG. 12 illustrates the repeatability of humidity sensors made in accordance with the examples at 33%, 43%, and 67% relative humidity;
FIG. 13 shows g-C3N4A schematic diagram of the adsorption process of one possible water molecule on the surface of the film;
FIG. 14 is a schematic view showing a humidity sensor manufactured by the embodiment applied to an automatic alarm device for diaper wetting;
FIG. 15 is a schematic view illustrating the application of the humidity sensor manufactured by the embodiment to nondestructive humidity detection of paper products.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.
The humidity sensor and the manufacturing method and application thereof provided by the present application are explained in detail by specific embodiments below.
Two-dimensional nanomaterials (hereinafter referred to as "two-dimensional materials") refer to materials in which electrons can move in a plane freely only on a nanoscale of two dimensions (e.g., 1nm to 100nm), such as a nano-film, a superlattice, a quantum well, and the like, and have many unique and excellent physicochemical properties, such as high electron mobility, high heat resistance, good high-temperature stability, stable chemical properties, and the like, which make them a hot research focus worldwide nowadays.
g-C3N4The material is a novel high molecular organic material, is an important member in a two-dimensional material, and has a plurality of excellent physicochemical properties such as good biocompatibility, good thermal stability, good chemical stability, low density, no cytotoxicity, easy structural modification and the like due to the unique electronic structure. g-C3N4The interior of the material contains nitrogen functional groups and electron delocalization structures, so that the material has a complex adsorption mechanism comprising hydrogen bond action, acid-base reaction, electrostatic action, redox reaction, pi-pi conjugation and the like, and thus g-C3N4The method has great research value in a plurality of fields such as catalysis, photoimaging, energy storage, biological medicine and the like.
At present, g-C is common3N4Comprises 5 crystal structures of α phase (α -C)3N4) β phase (β -C)3N4) Cubic phase (C-C)3N4) Quasi-cubic phase (pc-C)3N4) And a graphite phase (g-C)3N4). Among them, the carbon nitride material of the first four crystal structures has a g-C of soft phase due to its unique valence bond structure to make its hardness comparable to that of diamond3N4The physical and chemical properties of the material are most stable at room temperature and normal pressure.
g-C3N4Is a non-metallic semiconductor formed by stacking two-dimensional sheets similar to graphene. g-C3N4As a graphite-like material, the van der waals forces between the layers render it insoluble in most solvents, while also providing good PH stability. g-C3N4In conventional solvents, for example: water, ethanol, DMF, etc. are not dissolved, nor do they react chemically with solvents. However, g-C3N4And may be partially decomposed or even completely decomposed under strong acid solution or hydrothermal conditions. Scientific researchers find the g-C after the high-concentration hydrochloric acid etching treatment3N4The specific surface area is 8.0m before etching2The/g is increased to 30.0m after etching2G, at the same timeg-C after etching3N4The surface of the silicon nitride has positive charges, and the forbidden band width, the ionic conductivity and the dispersibility of the silicon nitride are improved.
To date, researchers have focused more on studying g-C3N4And the present application attempts to convert g-C3N4The method is applied to humidity indication and achieves unexpected effects.
In a first aspect, the present application provides the use of graphite phase carbon nitride for humidity indication.
In one implementation, the graphite phase carbon nitride is a graphite phase carbon nitride thin film.
In the present application, the g-C3N4Can be prepared according to a process comprising the following steps 1 to 3:
step 1, preparation of g-C3N4And (4) suspending the solution.
In the present application, the g-C3N4The suspension may be g-C3N4Solid-liquid mixed dispersions with solvents, i.e. g-C3N4An aqueous dispersion of (1).
In one achievable mode, the preparing g-C3N4The suspension comprises the following steps 1-1 and 1-2:
step 1-1, preparation of g-C3N4And (3) a solid.
The application is to the preparation of g-C3N4The method for producing the solid is not particularly limited, and g-C can be produced by any of the conventional methods3N4Methods of making solids, e.g. said g-C3N4The solid may be prepared by a method comprising the following steps 1-1-1 to 1-1-3:
step 1-1-1, weighing raw materials.
The application is to the preparation of g-C3N4The solid raw material is not particularly limited, and any one of the conventional methods capable of producing g-C by thermal polymerization can be used3N4Solid raw materials, for example, urea, etc.
Step 1-1-2, heating the raw materials and preserving heat.
The heating and heat preservation modes are not particularly limited in the application, and any preparation method and parameters matched with the used raw materials in the prior art can be adopted to prepare the g-C3N4High efficiency of solids, g-C produced3N4The purity of the solid is high, and the yield is high.
Taking urea as an example, the g-C can be obtained by controlling the heating rate to be 10 ℃/min, heating to 550 ℃ and keeping the temperature for 4h3N4And (3) a solid.
In the present application, the g-C3N4The solids are g-C3N4Solid powder, preferably, said g-C3N4The particle size of the solid powder is 2-10 nm.
And 1-1-3, cooling the system after heat preservation.
The cooling mode in the present application is not particularly limited, and any cooling mode in the prior art, such as natural cooling or auxiliary cooling, may be adopted, and the cooling mode along with the furnace may be adopted, taking the above example as an example.
The structure, morphology and composition properties of the thin film are examined by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), see in particular examples fig. 2, fig. 3 and fig. 4.
Step 1-2, subjecting the g-C obtained by the preparation3N4The solid is dispersed in a solvent.
In the present application, the solvent may be any one of those known in the art capable of dispersing g-C3N4The solvent for the solid powder is, for example, high-purity water, alcohol, or the like.
Step 2, mixing g-C3N4The suspension is coated on the substrate.
In the present application, any of the coating methods known in the art may be employed to enable the formation of g-C3N4The suspension is preferably uniformly applied to the substrate.
Step 3, coating with g-C3N4Substrate drying of suspensionAnd (5) drying.
In the present application, the coating is g-C3N4The method for drying the substrate in the suspension is not particularly limited, and any method of removing the solvent on the substrate in the prior art may be used, and alternatively, the temperature for drying may be a temperature capable of removing the g-C3N4The solvent in the suspension can not damage the substrate.
In a second aspect, the present application provides a humidity sensor comprising a substrate, a g-C bonded to the substrate3N4A film, and a film connected to said g-C3N4And a resistance value detection device on the film.
In the present application, the substrate includes a PCB board, a flexible interdigital electrode, and the like.
Preferably, the outline dimension of the window on the PCB substrate is 1 × 1cm, the thickness of the electrode is 50 μm, and the width and the gap are both 200 μm, and the applicant finds that the selected interdigital electrode has the advantages of large-scale mass production, low cost, miniaturization, and the like.
Preferably, the flexible interdigital electrode is made of a nickel/copper material. The applicant finds that the flexible electrode can be conveniently applied to wearable respiration monitoring, athlete close fitting sweat detection and other aspects.
Further, the g-C3N4The thickness of the film is 0.1 to 1 nm. The applicant has found that at this thickness, the sensor response time is shorter, the recovery performance is excellent, and the sensitivity to humidity is higher.
FIG. 1 shows the manufacture of g-C3N4A schematic of a humidity sensor flow diagram, as shown in fig. 1, in one implementable form, the humidity sensor is prepared by a method comprising steps 1 'through 4' as follows:
step 1' preparation of g-C3N4And (4) suspending the solution.
Please refer to step 1 for the method used in this step, which is not described herein again.
Step 2', adding g-C3N4Coating the suspension on the substrate;
please refer to step 2 for the method used in this step, which is not described herein again.
Step 3' coating with g-C3N4Drying the substrate of the suspension;
please refer to step 3 for the method used in this step, which is not described herein again.
And 4', connecting the dried device with a resistance detection device.
In the present application, the resistance detection device employs a high-precision LCR measuring instrument.
The Applicant has found that said g-C3N4The resistance of the film decreases with increasing humidity, but the resistance is minimal at humidity close to 100%, but still has a resistance value above 100 ohms.
The Applicant has found that said g-C3N4There is a non-linear relationship between the resistance of the film and the humidity of the object to be detected, see in the example fig. 5, so that the humidity sensor can be based on the g-C3N4And calculating the humidity of the object to be detected by the resistance value of the film.
The Applicant studied the g-C at a temperature of 20 ℃ and a Relative Humidity (RH) of 0-97%3N4The humidity sensing device has the advantages that the humidity sensing characteristic of the humidity sensor is high in sensitivity, quick in response, short in recovery time and the like.
In a third aspect, the present application also provides a method of manufacturing the humidity sensor of the second aspect, the method comprising the following steps 1 "to 4":
step 1', preparation of g-C3N4And (4) suspending the solution.
For the method in this step, please refer to step 1', which is not described herein again.
Step 2', mixing g-C3N4Coating the suspension on the substrate;
for the method in this step, please refer to step 2', which is not described herein again.
Step 3' coating with g-C3N4Drying the substrate of the suspension;
for the method in this step, please refer to step 3', which is not described herein again.
And 4', connecting the dried device with a resistance detection device.
For the method in this step, please refer to step 4', which is not described herein again.
In a fourth aspect, the present application further provides a humidity sensing system, where the system includes the second aspect, the humidity sensor, the processor and the service terminal, and the processor receives the humidity information collected by the humidity sensor, processes the humidity information, and reports the processed humidity information to the service terminal.
In this application, can carry out data interaction through modes such as WIFI connection between humidity transducer, treater and the service terminal, the treater can with the resistance value that humidity transducer gathered is handled into corresponding humidity value, and will service terminal is reported to the humidity value, service terminal can with the humidity value is fed back to the user.
In this application, the service terminal includes a mobile phone, a PC, or a device that needs to collect humidity information, such as a humidifier.
In a fifth aspect, the application also provides the humidity sensor and the use of the humidity sensing system for humidity detection of diapers.
In the application, the humidity sensor or the humidity sensor in the humidity sensing system can be close to the paper diaper, so that the humidity information of the paper diaper can be known without damage.
In a sixth aspect, the present application further provides the use of the moisture sensor and the moisture sensing system for non-destructive testing of paper products.
In the present application, the moisture sensor or the moisture sensor in the moisture sensing system may be brought close to the paper product, and the moisture information of the paper product may be known without damage.
The application provides a humidity transducer and humidity sensing system can nondestructive test the humidity of paper historical relic to do not damage under the prerequisite of file, provide reliable foundation for historical relic protection and restoration.
Examples
CO (NH) as used in the present application2)2Purchased from shansi chemistry, shanghai.
Example 1 preparation of graphite phase carbon nitride
Adding 20g of urea into a 50mL crucible, wrapping the crucible opening with aluminum foil, covering the crucible opening with a cover, and ensuring that the crucible is in a semi-sealed state so as to reduce the volatilization of the urea in the temperature rise process, wherein the thermal polymerization process is carried out in a muffle furnace. Setting the temperature raising program to be 10 ℃/min, raising the temperature to 550 ℃, preserving the heat for 4h, cooling along with the furnace, and obtaining the product which is g-C without any treatment3N4。
In the embodiment, urea is used as a raw material, the heating rate, the reaction temperature and the reaction time are controlled to perform the thermal polymerization reaction of the urea, after the reaction is finished, the temperature is cooled to room temperature along with a furnace, and the product is not subjected to further treatment, namely g-C3N4And the product is in the form of a curly flake.
The g-C prepared in this example was characterized by SEM (Hitachi S-4800)3N4The surface morphology of (1).
FIG. 2a shows g-C prepared in this example3N4Nanostructures at a unit scale of 10 μm, FIG. 2b shows g-C prepared in this example3N4Nanostructures at a unit scale of 1 μm, FIG. 2C shows g-C prepared in this example3N4The nanostructuring at a unit dimension of 100nm, FIG. 2d shows g-C prepared in this example3N4Nanostructures at a unit size of 200 nm. From FIGS. 2a to 2d, it can be seen that g-C prepared by high-temperature polycondensation of urea as a precursor3N4Having a porous lamellar microstructure, the Applicant believes that the synthesis of g-C is due to the thermal dissociation of urea during the preparation process3N4The process generates a large amount of ammonia gas, thereby promoting the formation of porous micro-morphology, and the micro-structure greatly promotes the g-C3N4Specific surface area of (2).
To further determine g-C prepared in this example3N4Sample composition of this example, g-C prepared in this example using FTIR testing techniques3N4The characterization was performed, and the results are shown in FIG. 3 at 1200-1700cm-1Continuous characteristic peaks appear in the region, which shows that C-N, C-N on the carbon-nitrogen heterocyclic ring and C-N outside the ring vibrate telescopically and are positioned at 802.42cm-1The characteristic peak at (A) represents g-C prepared in this example3N4Flexural vibration of the carbon-nitrogen ring in the basic structural unit, located at 3072.76cm-1The absorption peaks indicate-NH and-NH on the 4-edge damaged aromatic ring2Stretching vibration of the group, or stretching vibration of water molecules adsorbed on its surface.
This example illustrates g-C prepared in this example by X-ray diffractometry (Rigaku Miniffex 600)3N4The sample is subjected to XRD characterization, and Cu K α is taken as a radiation source
Figure BDA0002361586400000071
The XRD pattern of the sample is shown in FIG. 4a, and it can be seen from FIG. 4a that g-C prepared in this example3N4The sample exhibited two distinct diffraction signature peaks at 11.5 ° 2 θ and 27.58 ° 2 θ, respectively, indicating successful preparation of g-C in this example3N4。
The results of characterization of the XRD of the sample were analyzed using the bragg formula, i.e., λ ═ 2dsin θ, where λ is the incident X-ray wavelength, d is the interplanar spacing, and θ is the bragg diffraction angle. It can be seen from the bragg formula that when a sample to be measured is irradiated by rays with given wavelengths, the smaller the diffraction angle theta is, the larger the layer-to-layer spacing d of crystal planes of the sample is.
Further, the peak position with a strong diffraction peak is 27.58 ° corresponding to the (002) crystal plane, and belongs to g-C3N4Carrying out pi-pi accumulation between layers; the peak position where the diffraction peak is weak was 11.5 ° corresponding to the (100) crystal plane, and was deposited in an in-plane heptazine ring structure.
Further, for g-C3N4XPS characterization of the nano material was performed to analyze the chemical states of the elements in the sample, and the results are shown in FIG. 4b, and it can be seen from the XPS full spectrum of FIG. 4b that g-C prepared in this example3N4The sample composition mainly includes C, N two elements.
FIG. 4C shows g-C prepared in this example3N4The high resolution XPS spectrum of C1 s; as can be seen from fig. 4C, two characteristic peaks appear in the characteristic energy region of C1s at 284.3eV and 287.65eV, respectively, and correspond to the amorphous carbon atom and sp in the nitrogen-containing aromatic ring (N — C ═ N), respectively2Hybridized carbon atom.
FIG. 4d shows g-C prepared in this example3N4From fig. 4d, the high resolution XPS spectrum of N1s (a) shows that three characteristic peaks appear at 398.11eV, 399.40eV, and 400.69eV, respectively, in the characteristic energy region of N1 s. Wherein the characteristic peaks which occur at 398.11eV and 399.40eV are respectively assigned to sp in the triazine structural unit (C-N ═ C)2Hybridized nitrogen atom and g-C3N4Connecting structure of (1) N- (C)3) The characteristic peak at 400.69eV is ascribed to the nitrogen atom (C-N-H) in the terminal amino group.
Embodiment 2PCB substrate
Take 0.5g g-C3N4Dissolving in 50mL deionized water, stirring, performing ultrasonic treatment for 30 min to obtain uniform dispersion, standing for 10h, collecting supernatant, dripping onto PCB substrate, and drying in vacuum oven at 60 deg.C for 4h to obtain g-C3N4A humidity sensor.
To test the humidity response characteristics of the humidity sensor, the applicant placed the humidity sensor manufactured in this example in a glass bottle prepared from a saturated salt solution and having a relative humidity of 0% to 97%, and measured the resistance of the humidity sensor at different RH levels using a TH2828 precision LCR meter.
In the present application, the response/recovery time is defined as the time required for the resistance value of the humidity sensor to reach 90% of its total resistance value change.
Response is given by R ═ Rx/R0Is determined wherein RxRepresents the resistance value, R, of the humidity sensor at a relative humidity of x%0Which represents the resistance value of the humidity sensor at a relative humidity of 0%.
FIG. 5 shows a film produced by the present embodimentAs can be seen from fig. 5, the resistance value of the humidity sensor manufactured in this embodiment decreases significantly as the relative humidity increases in the range of 0% to 97% and the fitting function of the resistance value (Y) and the relative humidity (X) of the humidity sensor is Y-887490.4 e (-X/15.5) -0601.6, and the regression coefficient R is2Is 0.9985.
Thus, the processor may calculate the current humidity from the resistance value measured in real time and the fitting function.
FIG. 6 shows g-C manufactured in this example through a relative humidity increase test and a relative humidity decrease test3N4Real-time response and recovery of the thin film sensor. As can be seen from FIG. 6, g-C3N4The film sensor has good adsorption-desorption performance.
Fig. 7 shows resistance values of the humidity sensor manufactured in the present embodiment at different humidities. On the basis of real-time response and recovery, the sensor is returned to 0% RH after responding under different relative humidities, and as can be seen from FIG. 7, when the RH level rises from 0% to 97%, g-C3N4The resistance of the thin film sensor decreased from 616.1452M Ω to 175.9962k Ω, indicating the excellent humidity sensitivity of the sensor.
Fig. 8 shows the fastest response time and recovery time of the humidity sensor manufactured by the present embodiment. By repeating the measurements for different relative humidities, it can be seen from FIG. 8 that the fastest response time (0.3s) and recovery time (11s), g-C, is achieved at 67% RH3N4The film sensor has good adsorption and desorption speeds for water molecules.
Fig. 9 shows the highest response at 97% RH for the humidity sensor made in this example. By repeating the measurements for different relative humidities, it can be seen from fig. 9 that the highest response (3570) is obtained at 97% RH, and the humidity sensor has a wide resistance range.
Fig. 10 shows the resistance value variation of the humidity sensor due to a humidity rise (relative humidity rises from 11% to 97%, up test) and a humidity fall (relative humidity falls from 97% to 11%, down test). As can be seen from fig. 10, the resistance value curves obtained by the up-flow test and the down-flow test are substantially symmetrical, and therefore, the applicant believes that the humidity sensor manufactured in this example has excellent adsorption-desorption properties.
Based on the data from the test of fig. 10, a hysteresis curve is plotted, as shown in fig. 11, and it can be seen from fig. 11 that the hysteresis effect of the humidity sensor manufactured in the present embodiment is negligible.
The humidity sensor manufactured in this example was subjected to repeated experiments in which three repeated measurements were performed at relative humidities of 33%, 43% and 67%, respectively, and the results are shown in fig. 12, and it can be seen from fig. 12 that the resistance values of the humidity sensor substantially agree with each other in the three measurements, and therefore, the applicant believes that the humidity sensor manufactured in this example exhibits excellent reproducibility.
The Applicant believes that this example utilizes the thermal polymerization method to produce g-C3N4Has the advantages of large specific surface area, high catalytic performance, and the like. Due to the large specific surface area, the surface of the humidity sensor is filled with a large number of active sites, so that the adsorption and desorption effects of water molecules on the surface of the humidity sensor are greatly enhanced. During the reaction for preparing the material, there may be cases where polycondensation is not completed, g-C prepared3N4Amino groups remain therein, thereby introducing nitrogen defects. g-C in an environment with low relative humidity3N4Hydrogen bonds are formed among the nitrogen defects of the film, and the surface of the film shrinks, so that the film is curled; meanwhile, a small amount of water molecules adsorbed on the surface of the humidity sensor form a discontinuous layer to block the free movement of the water molecules, so that the humidity sensor shows high resistance at low relative humidity. In the environment with high relative humidity, water molecules can be adsorbed on g-C in multiple layers3N4On the surface of the film, hydrogen bonds are formed between the water molecules and the nitrogen defects, so that the surface of the film is expanded, and the resistance value is reduced.
FIG. 13 shows g-C3N4A possible adsorption process of water molecules on the surface of the film. As shown in FIG. 13, initially, a small amount of water molecules was adsorbed at g-C3N4The aqueous layer is dispersed withThe increase of relative humidity, the adsorption of multiple water molecules to g-C3N4Film surface, g-C3N4The water molecules on the surface of the film form a continuous layer. Due to the existence of amino groups, more hydrogen bonds can be generated in the process of continuously combining with water molecules, the adsorption of the water molecules is facilitated, and the adsorbed water molecules can generate protons (H)3O+→H2O+H+). In addition, the amino group is also protonated (-NH → NH)2 +) Proton hopping between adjacent water molecules occurs more readily, according to the Grotthus chain reaction H2O+H3O+→H3O++H2O and H2O+NH2 +→NH++H3O+When water molecule penetrates g-C3N4With an intermediate layer between the films, the conductivity of the sensor increases, and the resistance value increases accordingly. -
The humidity sensor manufactured by the embodiment is applied to the automatic alarm device for the diaper, namely, as shown in fig. 14, the humidity sensor is clamped outside the diaper, and an experimental result shows that the diaper with the automatic humidity detection and alarm functions can be practical, quick, accurate and safe for the common diaper. The alarm device has the characteristics of economy, durability, convenient use, strong anti-interference capability and the like, fills the blank of the automatic alarm of the diaper, helps a guardian to quickly and accurately judge whether the diaper is wet or not and the quantity of urine, and also ensures the sleep health quality of the patient or the baby.
EXAMPLE 3 Flexible substrate
The method used in this example is similar to example 2, except that flexible interdigitated electrodes are used as the substrate.
(1) The humidity sensor manufactured by the embodiment is applied to nondestructive testing of wet paper
Various paper moisture meters commonly available on the market require direct contact with the paper surface. For example, a probe-type moisture meter needs to directly insert a probe into paper to measure moisture, and certain damage is necessarily caused to paper products such as precious paper cultural relics. In addition, the high frequency type moisture meter, which eliminates the need for a needle, still requires the probe to be in contact with the surface of the paper, and the thermal effect produced during the measurement process may cause damage to the cultural relics.
To solve this problem, rice paper commonly used in painting and calligraphy creation was selected as test paper, and the humidity of the paper was measured by the humidity sensor manufactured in this example, and the result is shown in fig. 15. In the experiment, compared with dry rice paper, the resistance value of the sensor is rapidly reduced when the sensor is close to wet rice paper, which shows that the sensor has extremely high sensitivity and ultra-fast response, and therefore, the sensor has potential application value in the humidity nondestructive detection of paper cultural relics.
(2) Humidity sensing manufactured by the embodiment is applied to a humidifier
According to the measurement, people feel that the most comfortable environmental temperature is about 25 ℃, the relative humidity is 45% -70%, the northern climate is dry in spring and autumn, the indoor relative humidity is only 15% -20%, people can feel dry throat, and particularly the throat is more serious after the warm air is supplied. For example, in hospitals, the humidity in a ward is increased by adopting methods such as sprinkling water in the ward, putting wet towels or washbasins on a heater and the like, so that the standard management of the ward is not facilitated, and daily activities are influenced. Therefore, the humidifier used in the room of the postoperative patient can increase the relative humidity in the patient room, improve the indoor dry environment, dilute the sputum in the respiratory tract to make the sputum easy to expectorate and reduce the complications of the respiratory tract.
The applicant manufactures a distributed humidity sensing humidifier by using the humidity sensor manufactured in the embodiment, that is, a plurality of humidity sensors manufactured in the embodiment are distributed in a humidification space, the humidity sensors and the humidifier can perform data interaction, and the humidifier can adjust the humidification strength and direction according to humidity information reported by the plurality of humidity sensors. Specifically, the humidifier can sense the humidity of the humidifier and the humidity of the surrounding environment through the humidity sensors distributed in the humidification space, each sensor can independently process the information of the sensor, a large amount of data is provided, the classification characteristic of a target can be further obtained, and the serious performance reduction caused by electronic countermeasures to a single sensor system is avoided, so that the indoor humidity change condition can be more accurately sensed, the defect that the traditional humidifier cannot automatically adjust the running state without being controlled is avoided, and the environment which makes a human body feel comfortable is achieved through the adjustment of the mist quantity of the humidifier and the automatic switch.
Based on the above embodiments, the present application provides a method based on g-C3N4A high-performance humidity sensor made of two-dimensional nano materials. The humidity sensor has the advantages of high sensitivity, good reversibility, quick response/recovery time and the like, and has the advantages of strong anti-interference capability, low cost, quickness, convenience in use, safety and the like.
The present application has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to limit the application. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the presently disclosed embodiments and implementations thereof without departing from the spirit and scope of the present disclosure, and these fall within the scope of the present disclosure. The protection scope of this application is subject to the appended claims.

Claims (9)

1. Use of graphite phase carbon nitride for humidity indication.
2. A humidity sensor, comprising a substrate, a g-C sensor bonded to the substrate3N4A film, and a film connected to said g-C3N4And a resistance value detection device on the film.
3. A humidity sensor according to claim 2, wherein the substrate comprises a PCB board and flexible interdigitated electrodes or the like.
4. A humidity sensor according to claim 2 or 3, wherein the humidity sensor is prepared by a method comprising the steps of:
preparation of g-C3N4Suspending liquid;
g to C3N4Coating the suspension on the substrate;
will be coated with g-C3N4Drying the substrate of the suspension;
and connecting the dried device with a resistance detection device.
5. Humidity sensor according to any of claims 2 to 4, characterized in that the preparation g-C3N4The suspension comprises:
preparation of g-C3N4A solid;
g-C obtained by preparation3N4The solid is dispersed in a solvent.
6. A method of manufacturing a humidity sensor according to any one of claims 2 to 5, the method comprising the steps of:
preparation of g-C3N4Suspending liquid;
g to C3N4Coating the suspension on the substrate;
will be coated with g-C3N4Drying the substrate of the suspension;
and connecting the dried device with a resistance detection device.
7. A humidity sensing system, the system includes the humidity sensor of any one of claims 2 to 5, a processor and a service terminal, the processor receives humidity information collected by the humidity sensor, processes the humidity information and reports the processed humidity information to the service terminal.
8. Use of the humidity sensor according to any one of claims 2 to 5 and the humidity sensing system according to claim 7 for the humidity detection of diapers.
9. Use of the moisture sensor of any of claims 2 to 5 and the moisture sensing system of claim 7 for non-destructive testing of paper products.
CN202010023338.4A 2020-01-09 2020-01-09 Humidity sensor and manufacturing method and application thereof Pending CN111189887A (en)

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