CN106290488A - Amino-functionalized carbon nanotube resistance type formaldehyde gas sensor and preparation method thereof - Google Patents

Abstract

The invention discloses an amino functionalized carbon nanotube resistance type formaldehyde gas sensor and a preparation method thereof. The gas-sensitive film is composed of amino-functionalized carbon nanotubes modified by tannic acid and polyethyleneimine. The gas sensor can detect formaldehyde gas at normal temperature, is insensitive to humidity, has strong anti-interference capability, high response sensitivity and quick response. The preparation method of the gas sensor is simple, easy to control and suitable for batch production, so that the gas sensor can be suitable for sensitive detection of formaldehyde in the fields of industrial production, process control, environment monitoring, modern agricultural production and the like.

Description

An amino functionalized carbon nanotube resistive formaldehyde gas sensor and its preparation method

technical field

The invention relates to the field of gas sensors, in particular to an amino functionalized carbon nanotube resistance type formaldehyde gas sensor and a preparation method.

Background technique

With the continuous development of intelligence and informatization, many fields of modern society, including environmental monitoring, industrial production, medical diagnosis and national defense and military, have higher and higher requirements for real-time monitoring of gases in the environment. Among them, formaldehyde gas has a wide range of existence and is very harmful to the human body, so the real-time monitoring of formaldehyde is particularly important. The development of lightweight and portable formaldehyde gas sensors will significantly affect human life. At present, the main formaldehyde gas sensors used are metal oxide semiconductor (MOS) sensors and solid electrolyte (SE) sensors, but both require higher Working at high temperature, high power consumption, low sensitivity, poor anti-interference ability, and inconvenient use. With the development of nanotechnology, a large number of research reports on nano-gas sensors have been published in recent years, especially carbon nanotube (CNTs) gas sensors. Sensors have made significant progress.

Carbon nanotubes have many advantages as a gas sensor: large specific surface area, strong adsorption capacity for gas; use at room temperature reduces the working temperature of the sensor; good chemical stability, small size. Carbon nanotubes have good detection effect on NO ₂ , SO ₂ , NH ₃ and O ₂ and other gases. However, due to the limitations of their own structure and chemical properties, the types of gases that can be adsorbed by intrinsic carbon nanotubes are very limited, limited to several strong oxidizing gases and strong reducing gases, and the detection of formaldehyde cannot be realized. nanotube modification. Carbon nanotube modification is mainly organic modification and inorganic doping. Inorganic doping is mainly to introduce metals or metal oxides on carbon nanotubes. Although formaldehyde can be detected better, it cannot be detected at room temperature. Organic modification mainly introduces amino functional groups to the surface of carbon nanotubes through covalent or non-covalent bonding methods, and relies on the interaction between amino groups and formaldehyde to change the resistance of the gas sensor to realize the detection of formaldehyde. However, the preparation of amino-functionalized carbon nanotubes by covalent bond method is cumbersome and will destroy the conjugated structure of carbon nanotubes, which will adversely affect their electrical conductivity and sensing performance. Although the non-covalent bond method is convenient and simple, due to the relatively weak force between the amino functional group and the carbon nanotubes, it is easy to peel off when the external conditions change, which has an adverse effect on its stability. Therefore, it is necessary to develop a simple and effective new method to prepare amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

Contents of the invention

In order to overcome the deficiencies of the prior art, the invention provides an amino functionalized carbon nanotube resistance type formaldehyde gas sensor and a preparation method thereof.

A method for preparing an amino functionalized carbon nanotube resistance type formaldehyde gas sensor, comprising the steps of:

Forming interdigitated electrodes on the flexible substrate by means of screen printing, inkjet printing and photolithography to obtain a flexible substrate with interdigitated electrodes;

Adding the carbon nanotubes to PBS buffer solution with pH=7.5-9 and sonicating for 10-60 minutes, wherein the concentration of the carbon nanotubes is 0.5-2 mg/ml. Then add tannic acid to the suspension of the carbon nanotubes, the tannic acid is 0.5-2 times the mass of the carbon nanotubes, and sonicate again for 10-60 minutes. The aqueous solution of polyethyleneimine is slowly added dropwise to the suspension of tannic acid and carbon nanotubes, and reacted for 0.5-5 hours to obtain an aqueous solution of amino-modified carbon nanotubes, wherein the molecular weight of polyethyleneimine can be 600-10000, The concentration is 1-10 mg/ml, and the mass of polyethyleneimine is 0.5-2 times that of carbon nanotubes.

The aqueous solution of the amino-modified carbon nanotubes prepared above is drop-coated on a flexible substrate with interdigitated electrodes, and dried to prepare an amino-functionalized carbon nanotube resistance type formaldehyde gas sensor.

The gas-sensitive film of the gas sensor of the present invention is composed of tannic acid and polyethyleneimine non-covalently modified carbon nanotubes, and the tannin is caused by the Michael addition of tannic acid and polyethyleneimine and the Schiff base reaction. The in-situ cross-linking reaction of acid and polyethyleneimine on the surface of carbon nanotubes forms a layer of uniform tannic acid-polyethyleneimine copolymer on the surface of carbon nanotubes to realize the surface modification of carbon nanotubes, thereby Amino functional groups were successfully introduced to the surface of carbon nanotubes. The macromolecular chains cross-linked by tannic acid and polyethyleneimine can produce strong repulsion and steric hindrance, which can make carbon nanotubes better dispersed in water and form a uniform dispersion. Carbon nanotubes have a large specific surface area, which is conducive to improving sensitivity. At the same time, the interaction between the amino groups introduced on the surface of carbon nanotubes and formaldehyde makes the response of amino functionalized carbon nanotubes to formaldehyde stronger.

The beneficial effects of the present invention are as follows:

(1) Raw material tannic acid and polyethyleneimine have a wide range of sources and are cheap.

(2) The surface amino functionalization of carbon nanotubes is completed in one step, which is simple and fast; and it is carried out in aqueous solution, which is green and environmentally friendly. The method for preparing the gas sensor of the present invention has simple preparation method, low cost and is suitable for mass production.

(3) The gas sensor can detect formaldehyde gas at normal temperature, is insensitive to humidity, has strong anti-interference ability, and has high response sensitivity and fast response.

Description of drawings

Fig. 1 is the structural representation of the amino functionalized carbon nanotube resistance type formaldehyde gas sensor of the present invention;

Fig. 2 is the transmission electron microscope picture of tannic acid polyethyleneimine modified carbon nanotube of the present invention, and picture (a) is the transmission electron microscope of unmodified carbon nanotube, and picture (b) is tannic acid polyethyleneimine Transmission electron microscope pictures of amino-functionalized carbon nanotubes after modification;

Fig. 3 is the response of the tannic acid polyethyleneimine modified carbon nanotubes to 50ppm formaldehyde and the response of unmodified carbon nanotubes to 50ppm formaldehyde.

detailed description

Example 1

(1) Form 10 pairs of interdigitated gold electrodes with a width of 40 μm and an interdigital gap of 40 μm by inkjet printing on a flexible substrate to obtain a flexible substrate with interdigitated gold electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=8.5 and sonicate for 1 h;

(3) Add 50 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 5ml of polyethyleneimine (10mg/ml) to the prepared suspension of carbon nanotubes and tannic acid, and react for 1h to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on the flexible substrate with interdigitated gold electrodes to prepare an amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

The prepared amino functionalized carbon nanotube gas sensor has good detection performance for formaldehyde. It can be seen from Figure 3 that the amino-functionalized carbon nanotube resistive formaldehyde gas sensor prepared by the present invention can detect formaldehyde at room temperature, has a good response to 50ppm formaldehyde, and can recover. However, the response of the unmodified carbon nanotubes to formaldehyde is small, indicating that the amino-functionalized carbon nanotube gas sensor prepared by the method has a better detection effect on formaldehyde.

Example 2

(1) Form 10 pairs of interdigitated gold electrodes 2 with a width of 40 μm and an interdigital gap of 40 μm by inkjet printing on a flexible substrate to obtain a flexible substrate with interdigitated gold electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=7 and sonicate for 1 h;

(3) Add 50 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 5ml of polyethyleneimine (10mg/ml) to the prepared suspension of carbon nanotubes and tannic acid, and react for 1h to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on the flexible substrate with interdigitated gold electrodes to prepare an amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

Comparative example 2 makes the amino-functionalized carbon nanotube resistance type formaldehyde gas sensor, and the response to gas is small mainly because the reaction degree of tannic acid and polyethyleneimine is small under neutral conditions, so it is deposited on carbon There is also less polyethyleneimine on the nanotubes, so the detection effect is not obvious.

Example 3

(1) Form five pairs of interdigitated gold electrodes 2 with a width of 40 μm and an interdigital gap of 40 μm by screen printing on a flexible substrate to obtain a flexible substrate with interdigitated gold electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=8.5 and sonicate for 1 h;

(3) Add 50 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 5ml of polyethyleneimine (10mg/ml) to the prepared suspension of carbon nanotubes and tannic acid, and react for 1h to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on the flexible substrate with interdigitated gold electrodes to prepare an amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

Example 4

(1) Form 10 pairs of interdigitated gold electrodes 2 with a width of 30 μm and an interdigital gap of 30 μm on a flexible substrate by inkjet printing to obtain a flexible substrate with interdigitated gold electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=8.5 and sonicate for 1 h;

(3) Add 50 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 5ml of polyethyleneimine (10mg/ml) to the prepared suspension of carbon nanotubes and tannic acid, and react for 1h to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on the flexible substrate with interdigitated gold electrodes to prepare an amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

Example 5

(1) Form 10 pairs of interdigitated silver electrodes 2 with a width of 40 μm and an interdigital gap of 40 μm by inkjet printing on a flexible substrate to obtain a flexible substrate with interdigitated silver electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=8.5 and sonicate for 1 h;

(3) Add 50 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 5ml of polyethyleneimine (10mg/ml) to the prepared suspension of carbon nanotubes and tannic acid, and react for 1h to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on a flexible substrate with interdigitated silver electrodes to prepare an amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

Example 6

(1) Form 10 pairs of interdigitated gold electrodes 2 with a width of 40 μm and a gap of 40 μm on a flexible substrate by inkjet printing to obtain a flexible substrate with interdigitated gold electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=8.5 and sonicate for 1 h;

(3) Add 30 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 5ml of polyethyleneimine (10mg/ml) to the prepared suspension of carbon nanotubes and tannic acid, and react for 1h to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on the flexible substrate with interdigitated gold electrodes to prepare the amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

The modified carbon nanotube resistive formaldehyde gas sensor prepared in Comparative Example 6 also has a smaller response to formaldehyde, mainly because the modified carbon nanotube has a smaller amino group content, so the response to formaldehyde is also smaller.

Example 7

(1) Form 10 pairs of interdigitated gold electrodes 2 with a width of 40 μm and a gap of 40 μm on a flexible substrate by inkjet printing to obtain a flexible substrate with interdigitated gold electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=8.5 and sonicate for 1 h;

(3) Add 50 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 2ml of polyethyleneimine (10mg/ml) to the prepared suspension of carbon nanotubes and tannic acid, and react for 1h to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on the flexible substrate with interdigitated gold electrodes to prepare an amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

The modified carbon nanotube resistive formaldehyde gas sensor prepared in Comparative Example 7 also has a smaller response to formaldehyde, indicating that a higher content of polyethyleneimine is also not conducive to the response of the modified carbon nanotubes to formaldehyde.

Example 8

(1) Form 10 pairs of interdigitated gold electrodes 2 with a width of 40 μm and a gap of 40 μm on a flexible substrate by inkjet printing to obtain a flexible substrate with interdigitated gold electrodes;

(2) Add 10 mg of carbon nanotubes to 50 ml of PBS buffer solution with pH=7 and sonicate for 1 h;

(3) Add 50 mg of tannic acid to the suspension of the prepared carbon nanotubes, and sonicate again for 1 h;

(4) Slowly add 5ml of polyethyleneimine (10mg/ml) dropwise to the prepared suspension of carbon nanotubes and tannic acid, and react for 10min to obtain an aqueous solution of amino-functionalized carbon nanotubes;

(5) The aqueous solution of the amino-modified carbon nanotubes prepared above was added dropwise on the flexible substrate with interdigitated gold electrodes to prepare an amino-functionalized carbon nanotube resistive formaldehyde gas sensor.

Claims (5)

1. an amino functional carbon nano tube resistor-type formaldehyde gas sensor, it is characterised in that: flexible substrates (1), interdigital Electrode (2), air-sensitive film (3), lead-in wire (4), at the upper drop coating air-sensitive film (3) of above-mentioned flexible substrates and interdigital electrode (2), on The air-sensitive film (3) stated is to be made up of the amino functional carbon nano tube after tannic acid and polyethyleneimine-modified.

A kind of amino functional carbon nano tube resistor-type formaldehyde gas sensor, it is characterised in that: Described flexible substrate can be printing paper, polyethylene terephthalate (PET) film.

A kind of amino functional carbon nano tube resistor-type formaldehyde gas sensor, it is characterised in that: Described interdigital electrode can be gold electrode, silver electrode, copper electrode and Graphene electrodes.

A kind of amino functional carbon nano tube resistor-type formaldehyde gas sensor, it is characterised in that: Interdigital electrode is 5～10 to be the interdigital electrode of 30～60 μm to interdigital width 30～60 μm, interdigital gap.

5. an amino functional carbon nano tube resistor-type formaldehyde gas sensor preparation method, it is characterised in that include walking as follows Rapid:

1) form interdigital electrode by the method for silk screen printing, inkjet printing and photoetching on a flexible substrate, prepare and there is fork Refer to the flexible substrates of electrode；

2) CNT is added in the PBS of pH=7.5～9 ultrasonic 10～60min, and wherein carbon nanotube concentration is 0.5～2mg/ml；Then adding tannic acid in the suspension of above-mentioned CNT, tannic acid is the 0.5 of carbon nanotube mass ～2 times, the most ultrasonic 10～60min；The aqueous solution of polymine is added to slowly the suspension of tannic acid and CNT In liquid, reacting 0.5～5h, obtain amino functional carbon nano-tube aqueous solutions, wherein the molecular weight of polymine can be 600 ～10000, concentration is 1～10mg/ml, and the quality of polymine is 0.5～2 times of CNT；

3) by step 2) the aqueous solution drop coating of preparation-obtained amino functional carbon nano tube is to step 1) in there is interdigital electricity In the flexible substrates of pole, obtain amino functional carbon nano tube resistor-type formaldehyde gas sensor after drying.