CN111751409A - A kind of preparation method of gas sensor based on flexible cotton fiber/polyaniline composite material - Google Patents

Abstract

The invention relates to a method for preparing a gas sensor based on a flexible cotton fiber/polyaniline composite material. The device involved in this method is composed of 4 sensors and 8 electrodes. In order to avoid the waste caused by traditional sensor substrates, cotton fiber/polyaniline composites were prepared by in-situ polymerization. The PANI sliver-loaded sensor (CSPS) and the cotton thread-based sensor (CYPS) have good gas sensing performance. Both CSPS and CYPS have high selectivity to NH3, high anti-interference to humidity, and good repeatability of sensing devices. Compared with sliver CSPS, quasi-one-dimensional cotton thread CYPS has higher sensitivity, faster response and recovery speed due to higher surface exposure rate. The response of CYPS to 100ppm NH3 was improved from ‑32.1% of CSPS to ‑92.1%, and the recovery time was shortened by 20.1 s from 30.1 s of CSPS. Importantly, the research endows cotton fibers with new and diversified functions and expands the application fields of cotton fibers.

Description

Preparation of a gas sensor based on flexible cotton fiber/polyaniline composite method

technical field

The invention relates to the field of toxic gas detection, in particular to a method for identifiable detection of toxic atmosphere. The method prepares a gas sensor by loading polyaniline on cotton fibers, and does not require a substrate, so as to realize detection of various target gases differential responses.

Background technique

Gas sensors play an increasingly important role in production and life, and are one of the core devices of the Internet of Things. Traditional gas sensing materials are mostly solid powders, which require rigid substrates (ceramic or quartz) or flexible substrates (plastic or rubber) to support. It is a challenge to find a gas sensor that does not require rigid substrates. Currently, most substrates, including ceramics and plastics, are non-biodegradable, non-recyclable, poor in biocompatibility, and poor in permeability. For example, plastics take 450 years to decompose, and ceramics are almost non-degradable compared to plastics. And the average lifespan of the various sensors and flexible displays is 18 months. Therefore, electronic applications generate a large amount of waste, which is a challenge to protect the environment. Furthermore, the low permeability of these substrates hinders the effective exposure of sensing materials to target gas molecules, thus limiting the enhancement and improvement of gas sensing performance. As the largest material system in nature, biomaterials not only have good biocompatibility, biodegradability, and versatility, but also have the advantages of sustainability and low cost. The flexibility and biodegradability of biomaterials have attracted more and more attention because they can reduce environmental pollution. As a product of plant fibers, filter paper has developed into a simple, multi-purpose, flexible, and disposable replacement device system due to its characteristics of easy degradation, high permeability, and low cost. Liu et al. constructed a flexible gas sensor for NO2 by spin-coating colloidal PbS quantum dots on Al2O3, polyethylene terephthalate, and paper, respectively. The conclusions show that the paper-based sensor exhibits the highest gas sensing response when the NO2 concentration is 50 ppm, which is mainly due to the higher exposure of PbS to the surface of the target gas molecules. Manohar et al. report that chemical sensors fabricated using a method of coating single-walled carbon nanotube (CNT) bundles on cellulose (paper and cloth) can detect oxidizing gases, such as bismuth, at 250 ppb and 500 ppb. Nitrogen oxide and chlorine. Swager et al. also reported that chemically functionalized carbon nanotubes could rapidly form sensor arrays on paper and used them for the discriminative detection of volatile organic compounds (VOCs). Meanwhile, paper-based CNT sensors have also been used for the selective detection of VOCs. However, a large amount of waste water, waste gas, solid waste and noise will be produced in the papermaking process, which will pollute the environment. Cho et al. loaded graphene on butterfly wings to fabricate an ultrasensitive gas sensor capable of highly selective detection of acetone vapor, including fast response time (1 s) and low detection threshold (20 ppb) and superior mechanical properties. However, butterfly wings are not easy to obtain, and the acquisition of large numbers of butterfly wings may lead to the extinction of butterflies and damage the ecosystem. On the other hand, cotton fibers for the fabrication of flexible electronic devices have received increasing attention due to their low cost, easy processing, good durability, and good mechanical properties. Torrisi et al. prepared a flexible conductive cotton fabric by precipitating graphene oxide (GO) dispersions onto cotton fabrics by vacuum filtration. On this basis, the cotton fabric was reduced by hot pressing at 180 °C for 60 min to prepare a flexible pressure sensor. Han et al. loaded CNTs on cotton yarn to fabricate an NH3 gas sensor with a detection limit of 8 ppm. The CNTs-cotton thread sensor exhibits uniformity, repeatability, and good mechanical resistance to bending. The above studies provide inspiration for the exploration of cotton fibers as gas sensing substrates and the development of gas sensors.

In terms of sensing materials, polyaniline (PANI) has also been widely studied as the development direction of flexible electronic devices due to its tunable morphology, scalable preparation, easy doping, and low cost. Structurally, the monomeric aniline of PANI contains amino groups, while natural cellulose is rich in hydroxyl groups. The hydroxyl group can easily form a hydrogen bond with the amino group, so that the aniline molecule is adsorbed on the cotton fiber through the hydrogen bond. Therefore, in this study, the multifunctional flexible composites of cotton fibers and PANI were prepared by in-situ polymerization for the first time. The gas sensing properties of the flexible composites were investigated.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing a gas sensor based on a flexible cotton fiber/polyaniline composite material. The device involved in this method is composed of 4 sensors, ceramic substrate and 8 electrodes, which can realize the identification and detection of ammonia water, acetone, ethanol and water vapor at room temperature (25 °C).

The present invention is a method for preparing a gas sensor based on flexible cotton fiber/polyaniline composite material, and the specific operation is carried out according to the following steps:

Preparation of gas sensitive materials:

a. Dissolve 5mL of aniline + 3mL of hydrochloric acid in 85mL of deionized water, and stir magnetically for 10min to fully dissolve;

b. Soak the washed and dried cotton sliver and cotton thread into the solution obtained in step a;

c. Dissolve 5g of ammonium persulfate in 15ml of deionized water to form an aqueous solution of ammonium persulfate

d. Put the above solutions obtained in steps b and c into an ice-water mixture and cool to 0°C, then quickly pour the cooled solutions b and c into a 200-ml beaker to mix, and stir in the ice-water mixture. reaction for 24 hours;

e. Soak the dark green cotton sliver and cotton thread samples obtained in step d in deionized water for 10 minutes (to remove unreacted residues), and then dry them at room temperature to make a gas sensor. This sample was labeled CSPS and CYPS, respectively.

Preparation of Resistive Gas Sensor Arrays:

a. Select two cotton slivers (CSPS) obtained in step e, marked as the first sensor and the second sensor to form a gas sensor array. Two cotton threads (CYPS) obtained in step d are selected and marked as the third sensor and the fourth sensor to form a gas sensor array.

The gas sensor array based on the flexible cotton fiber/polyaniline composite material obtained by the method has the purpose of detecting toxic atmospheres such as ammonia, acetone, ethanol and water vapor.

Description of drawings

Figure 1 is the scanning electron microscope images of the present invention corresponding to (a) to (c) pure cotton sliver, (d) to (f) CSPS composite material and (g) to (i) CYPS composite material under different magnifications;

Figure 2 shows the response of the array of sliver sensors (first sensor and second sensor,) to (a) ammonia water and air, (b) acetone and air, (c) ethanol and air, and (d) humidity at room temperature in the present invention and the response curve of air;

Fig. 3 is the cotton thread sensor (the third sensor and the fourth sensor,) array in the present invention for (a) ammonia water and air, (b) acetone and air, (c) ethanol and air, and (d) humidity and air at room temperature Air response curve;

Fig. 4 is the X-ray diffraction pattern in the present invention, and a to c in the figure correspond to pure cotton sliver, cotton sliver, cotton thread respectively

Detailed ways

Example 1

Preparation of gas sensitive materials:

a. Dissolve 5mL of aniline + 3mL of hydrochloric acid in 85mL of deionized water, and magnetically stir for 10min to fully dissolve;

b. Soak the washed and dried cotton sliver into the solution obtained in step a;

c. Dissolve 5g of ammonium persulfate in 15ml of deionized water to form an aqueous solution of ammonium persulfate

d. Put the above solutions obtained in steps b and c into an ice-water mixture and cool to 0°C, then quickly pour the cooled solutions b and c into a 200-ml beaker to mix, and stir in the ice-water mixture. reaction for 24 hours;

e. Soak the dark green cotton sliver sample obtained in step d in deionized water for 10 minutes (to remove unreacted residues), and then dry it at room temperature to make a gas sensor. Label this sample as CSPS, respectively.

Example 2

a. Dissolve 5mL of aniline + 3mL of hydrochloric acid in 85mL of deionized water, and magnetically stir for 10min to fully dissolve;

b. Soak the washed and dried cotton thread into the solution obtained in step a;

c. Dissolve 5g of ammonium persulfate in 15ml of deionized water to form an aqueous solution of ammonium persulfate

d. Put the above solutions obtained in steps b and c into an ice-water mixture and cool to 0°C, then quickly pour the cooled solutions b and c into a 200-ml beaker to mix, and stir in the ice-water mixture reaction for 24 hours;

e. Soak the dark green cotton thread sample obtained in step d in deionized water for 10 minutes (to remove unreacted residues), and then dry it at room temperature to make a gas sensor. This sample is individually labeled as CYPS.

Preparation of gas sensor array:

Example 3

Cut the cotton sliver thread obtained in step e in Examples 1-4 to a suitable size, and mark them as the first sensor, the second sensor, the third sensor and the fourth sensor, respectively, to form a gas sensor array.

Detection of target atmosphere by gas sensor array:

Example 4

Turn on the power of the Catherine meter, and test the tampon (CSPS-1, CSPS-2) sensor array obtained in step e at room temperature (temperature 25 ℃, relative humidity 25%) under a bias voltage of 1 V in ammonia water and air. resistance. It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based cotton sliver sensor array to 1000ppm ammonia water reaches -32.15% and -32.04%, respectively; the response time is 1.9 and 2.1s; the recovery time is 30.1 and 30.1 s, respectively. 31.3s (Fig. 2a).

Example 5

Turn on the power of the Catherine meter, and test the tampon (CSPS-1, CSPS-2) sensor array obtained in step e at room temperature (temperature 25 ℃, relative humidity 25%) under 1 V bias in acetone and air. resistance. It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based cotton sliver sensor array to 1000ppm acetone reaches -17.90% and -17.95%, respectively; the response time is 27.6 and 27.5s; the recovery time is 25.3 and 25.3 seconds, respectively 25.8 (Fig. 2b).

Example 6

Turn on the power of the Catherine meter, and test the tampon (CSPS-1, CSPS-2) sensor array obtained in step e at room temperature (temperature 25 ℃, relative humidity 25%) under 1 V bias in ethanol and air. resistance. It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based tampon sensor array to 1000ppm ethanol reaches -7.13% and -7.18%, respectively; the response time is 27.1 and 26.8s; the recovery time is 41.2 and -7.18s, respectively. 43.5 (Fig. 2c).

Example 7

Turn on the power of the Catherine meter, and test the tampon (CSPS-1, CSPS-2) sensor array obtained in step e at room temperature (temperature 25 ℃, relative humidity 25%) under a bias voltage of 1 V in water vapor and air The resistance. It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based tampon sensor array to 1000ppm water vapor reaches -5.4% and -5.5%, respectively; the response time is 13.3 and 13.0s; the recovery time is 17.4 and 18.8 (Fig. 2d).

Example 8

Turn on the power of the Catherine meter, and test the resistance of the cotton thread (CYPS-1, CYPS-2) sensor array obtained in step e in ammonia water and air at room temperature (temperature 25 ℃, relative humidity 25%) under a bias voltage of 1 V . It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based cotton wire sensor array to 1000ppm ammonia water reaches -92.1% and -93.5%, respectively; the response time is 1.60 and 1.75s; the recovery time is 21.1 and 22.4, respectively (Fig. 3a).

Example 9

Turn on the power of the Catherine meter, and test the resistance of the cotton thread (CYPS-1, CYPS-2) sensor array obtained in step e in acetone and air at room temperature (temperature 25 °C, relative humidity 25%) under a bias voltage of 1 V. . It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based cotton thread sensor array to 1000ppm acetone reaches -36.4% and -37.6%, respectively; the response time is 7.60 and 7.77s; the recovery time is 11.1 and 12.5, respectively (Fig. 3b).

Example 10

Turn on the power of the Catherine meter, and test the resistance of the cotton thread (CYPS-1, CYPS-2) sensor array obtained in step e at room temperature (temperature 25 °C, relative humidity 25%) in ethanol and air under a bias voltage of 1 V. . It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based cotton wire sensor array to 1000ppm ethanol reaches -13.1% and -13.7%, respectively; the response time is 13.1 and 14.5s; the recovery time is 10.7 and 11.1, respectively s (Fig. 3c).

Example 11

Turn on the power of the Catherine meter, and test the cotton thread (CYPS-1, CYPS-2) sensor array obtained in step e at room temperature (temperature 25 ℃, relative humidity 25%) under a bias voltage of 1 V in water vapor and air. resistance. It can be seen from the response curve that at room temperature, the response size of the flexible polyaniline-based cotton line sensor array to 1000ppm water vapor reaches -8.1% and -8.4%, respectively; the response time is 6.8 and 6.85s; the recovery time is 10.5 and 11.2s (Fig. 3d).

Example 12

Crystallization properties

The X-ray diffractometer was used to detect the samples, and it was found that the peak of the raw cotton cloth sample appeared a strong peak at 23.1 ^o , and two low peaks appeared at 15.2 ^o and 16.6 ^o . The XRD patterns of CSPS and CYPS are almost unchanged compared with cotton, and there are no characteristic peaks of PANI. It may be due to the very thin coating of PANI on cotton fibers, so no XRD characteristic peaks of PANI appear. It is worth noting that the XRD peaks of CSPS and CYPS shift slightly towards the low frequency. The main reason is that PANI is a rigid molecule, and the polyaniline coated on the cotton fiber will be uniformly combined with the cotton fiber during the drying process, resulting in a change in the structure of the cotton fiber.

The preparation method of the gas sensor based on the flexible cotton fiber/polyaniline composite material prepared by this method. It can be seen from the gas-sensing data that CYPS can achieve faster detection compared with CSPS. We can use this feature to make more sensitive gas-sensing sensors, and use other data analysis methods to identify explosive vapors. The method still falls in within the protection scope of the present invention.

Claims (4)

1. A preparation method of a gas sensor based on a flexible cotton fiber/polyaniline composite material specifically comprises the following steps:

a. dissolving 5mL of aniline and 3mL of hydrochloric acid in 85mL of deionized water, and magnetically stirring for 10min to fully dissolve the aniline and the hydrochloric acid;

b. b, soaking the washed and dried cotton slivers and cotton threads into the solution obtained in the step a;

c. dissolving 5g of ammonium persulfate into 15mL of deionized water to form an aqueous solution of ammonium persulfate;

d. respectively putting the solutions obtained in the steps b and c into an ice-water mixture to be cooled to 0^oC, quickly pouring the cooled solution b and the solution C into a 200 ml beaker for mixing, and stirring and reacting in an ice-water mixture for 24 hours;

e. and d, soaking the dark green cotton sliver and cotton thread samples obtained in the step d in deionized water for 10min (removing unreacted residues), and drying at room temperature to obtain the gas sensor.

2. Marking this sample as CSPS and CYPS respectively a method for making a flexible cotton fiber/polyaniline composite-based gas sensor according to claim 1, characterized in that step e is to put cotton sliver, cotton thread into solution to load PANI to form a cotton fiber/polyaniline composite.

3. The method for preparing the gas sensor based on the flexible cotton fiber/polyaniline composite material as claimed in claim 1, wherein the temperature in step c is 25 ℃ and the reaction time is 36 hours.

4. The use of a gas sensor array of flexible cotton fibre/polyaniline composite obtained according to the method of claim 1 for detecting an atmosphere containing ammonia, formaldehyde, ethanol and water vapour.

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