CN104614437A - Electrode spacing optimization method for carbon nanotube three-electrode gas sensor - Google Patents

Abstract

The invention discloses an electrode spacing optimization method for a carbon nanotube three-electrode gas sensor. The method is used for optimizing the electrode spacing between the first electrode and the second electrode and between the second electrode and the third electrode of the carbon nanotube three-electrode gas sensor. The method comprises the following steps: designing the electrode spacing, constructing a sensor array consisting of different electrode spacing sensors, performing concentration detection on gas of known concentration by using the constructed sensor array, constructing a database for the electrode spacing of the sensor array and the corresponding gas detection result, constructing a quantitative analysis model for the detected gas concentration, and optimizing the electrode spacing of each composition sensor in the sensor array, so that the optimal electrode spacing aiming at a single sensor which corresponds to different detection gases and the optimal electrode spacing aiming at each composition sensor in the sensor array which corresponds to the mixed gas can be effectively obtained. Therefore, high detection sensitivity can be obtained.

Description

Electrode spacing optimization method for carbon nanotube three-electrode gas sensor

technical field

The invention belongs to the field of gas sensing, and in particular relates to an electrode spacing optimization method of a carbon nanotube three-electrode gas sensor.

Background technique

In recent years, with the continuous development of carbon nanotechnology, gas-sensitive, temperature-sensitive and humidity-sensitive sensors made of carbon nanotubes as sensitive materials continue to emerge. CN102081073A discloses a micro-nano carbon nanotube film three-electrode sensor, which uses three electrodes separated from each other by insulating pillars (the base of the carbon nanotube film on the inner surface of the first electrode) to form a sensor for detecting gas, temperature and humidity; CN102095791B proposes a method for detecting the concentration of a multi-component mixed gas by composing a sensor array composed of the carbon nanotube thin film three-electrode sensor disclosed in CN102081073A.

Because carbon nanotube sensors have unique advantages such as low operating voltage and small overall size, they have broad application prospects in many fields such as biology, chemistry, machinery, and aviation. However, the current carbon nanotube three-electrode sensors all work at several specific electrode spacings. There is no targeted structural support for different detection gases, and it is difficult to obtain higher detection sensitivity; The sensor array detects the mixed gas, and it remains to be clarified which electrode spacing combination of multiple sensors can obtain the best detection effect. Therefore, there is an urgent need for a method to optimize the electrode spacing of the carbon nanotube three-electrode sensor, so as to improve the detection sensitivity and accelerate the application of the sensor.

Contents of the invention

The present invention aims at the above-mentioned problems and deficiencies existing in the existing carbon nanotube three-electrode sensors, and provides a single carbon nanotube three-electrode sensor and a plurality of carbon nanotube three-electrode sensors combined to form a sensor array. The optimization method can effectively obtain the optimal electrode spacing of a single sensor corresponding to different detection gases, and the optimal electrode spacing of each component sensor in the sensor array corresponding to a mixed gas, thereby obtaining higher detection sensitivity.

In order to achieve the above object, technical scheme of the present invention is:

The electrode spacing optimization method of the carbon nanotube three-electrode gas sensor optimizes the electrode spacing between the first electrode and the second electrode, the second electrode and the third electrode of the carbon nanotube three-electrode gas sensor, and the carbon nanotube three-electrode gas sensor The inner surface of the first electrode of the gas sensor is distributed with a carbon nanotube film substrate, the second electrode is a lead-out plate with lead-out holes, the third electrode is a collector, and the three electrodes are separated from each other by insulating pillars. The distance between two adjacent electrodes ranges from 50 μm to 250 μm, which is characterized in that the following optimization steps are adopted:

1) Design pole spacing

In the sensor array composed of n carbon nanotube three-electrode gas sensors, the distance between the first electrode and the second electrode of the i-th sensor is d _i1 , and the distance between the second electrode and the third electrode is d _i2 , where , i=1, 2,..., n, when n is 1, it refers to a single carbon nanotube three-electrode gas sensor, and the d _i1 and d _i2 of each sensor have two situations of equal spacing and unequal spacing:

Equal spacing: d _i1 and d _i2 are equal, d _i1 or d _i2 increases with a step size S starting from 50 μm, until d _i1 or d _i2 is greater than or equal to 250 μm, and S is any integer between 0 μm and 200 μm;

Unequal spacing: d _i1 and d _i2 are not equal, d _i1 starts from 50 μm and increases with step size S ₁ until d _i1 is greater than or equal to 250 μm, d _i2 starts with 50 μm and increases with step size S ₂ until d _i2 is greater than or equal to 250 μm, Both S ₁ and S ₂ are arbitrary integers between 0 μm and 200 μm. When d _i1 takes one of the aforementioned values, d _i2 takes a value different from d _i1 ;

2) Construct a sensor array composed of sensors with different pole spacing

For a single-component measured gas or a mixed gas composed of R components, select the number of sensors n, n≥R, use the electrode spacing designed in step 1), and construct m groups of n different equal spacing and different Equally spaced carbon nanotube three-electrode gas sensors form m groups of carbon nanotube three-electrode gas sensor arrays with different pole spacings, and d _i1 and d _i2 of all sensors in the m group of sensor arrays are all possibilities for designing the pole spacing in step 1) exhaustive or empirical selection;

3) Use the constructed sensor array to detect the concentration of gas with known concentration

A variety of single-component gas or multi-component mixed gas samples with different concentrations are prepared by using standard gases, and m groups of carbon nanotube three-electrode gas sensor arrays with different electrode spacings constructed by step 2) are used for detection in groups, and each measured The gas discharge ion current value of the gas sample;

4) Establish the electrode spacing of the sensor array and its corresponding gas detection result database

Use the d _i1 and d _i2 of each component sensor in the carbon nanotube three-electrode gas sensor array of all m groups, the gas discharge ion current value obtained by detecting the gas sample, and the concentration of the gas to be measured to establish the electrode spacing and the corresponding gas detection result database;

5) Establish a quantitative analysis model for the measured gas concentration

Adopt the support vector machine method, with the measured gas discharge ion current value in the database established in step 4) as input, with its corresponding gas concentration as output, set up the measured gas concentration quantitative analysis model;

6) Optimizing the electrode spacing of each component sensor in the sensor array

Adopt the measured gas concentration quantitative analysis model established by step 5) to analyze the gas concentration of all measured gas samples to obtain the detected concentration of the measured gas; calculate the difference between the detected concentration of the measured gas and its corresponding actual concentration, Then divide by the actual concentration of the gas to be measured to obtain the relative error of detecting the gas; using the particle swarm optimization algorithm, with the minimum relative error of the gas to be measured as the goal, the m group of carbon nanotube three electrodes constructed by step 2) The d _i1 and d _i2 of each component sensor in the gas sensor array are optimized, and finally the best electrode spacing of each sensor in the carbon nanotube three-electrode gas sensor array for detecting the gas is obtained.

The carbon nanotube three-electrode gas sensor can be replaced by a carbon nanotube three-electrode temperature sensor or a carbon nanotube three-electrode humidity sensor for detecting temperature or humidity.

The present invention has the following beneficial effects:

1) Strong scalability: This method can optimize the electrode spacing of each sensor in the carbon nanotube three-electrode gas sensor array for detecting single-component gases and multi-component gases, and can also be extended to the temperature and Humidity Sensor.

2) Good combination: For a specific gas, you can choose a specific concentration of gas samples for optimization, or you can choose a variety of gas samples with different concentrations for optimization. The gas samples are simple and can analyze a variety of gases. Combination good.

3) Strong flexibility: When establishing the quantitative analysis model of the measured gas concentration, various quantitative analysis methods other than the support vector machine can be used, and the best quantitative analysis model of the method can be obtained by optimizing its parameters, which has strong flexibility .

Description of drawings

Fig. 1 is a flowchart of the optimization method of the present invention;

Fig. 2 is the relative error of detecting NO and _SO2 mixed gas in the embodiment of the present invention.

Detailed ways

Introduce detailed technical scheme of the present invention below in conjunction with accompanying drawing:

The electrode spacing optimization method of the carbon nanotube three-electrode gas sensor is to optimize the electrode spacing between the first electrode and the second electrode, the second electrode and the third electrode of each sensor in the carbon nanotube three-electrode gas sensor array, said The inner surface of the first electrode of the carbon nanotube three-electrode gas sensor is distributed with a carbon nanotube film substrate, the second electrode is an extraction electrode plate with an extraction hole, the third electrode is a collector, and the three electrodes are separated from each other by insulating pillars. The distance between two adjacent electrodes among the three electrodes ranges from 50 μm to 250 μm. It employs the following optimization steps:

1) Design pole spacing

In the sensor array composed of n carbon nanotube three-electrode gas sensors, the distance between the first electrode and the second electrode of the i-th sensor is d _i1 , and the distance between the second electrode and the third electrode is d _i2 , where , i=1, 2,..., n, when n is 1, it refers to a single carbon nanotube three-electrode gas sensor, and the d _i1 and d _i2 of each sensor have two situations of equal spacing and unequal spacing:

Equal spacing: d _i1 and d _i2 are equal, d _i1 or d _i2 increases with a step size S starting from 50 μm, until d _i1 or d _i2 is greater than or equal to 250 μm, and S is any integer between 0 μm and 200 μm;

Unequal spacing: d _i1 and d _i2 are not equal, d _i1 starts from 50 μm and increases with step size S ₁ until d _i1 is greater than or equal to 250 μm, d _i2 starts with 50 μm and increases with step size S ₂ until d _i2 is greater than or equal to 250 μm, Both S ₁ and S ₂ are arbitrary integers between 0 μm and 200 μm. When d _i1 takes one of the aforementioned values, d _i2 takes a value different from d _i1 ;

2) Construct a sensor array composed of sensors with different pole spacing

For a single-component measured gas or a mixed gas composed of R components, select the number of sensors n, n≥R, use the electrode spacing designed in step 1), and construct m groups of n different equal spacing and different Equally spaced carbon nanotube three-electrode gas sensors form m groups of carbon nanotube three-electrode gas sensor arrays with different pole spacings, and d _i1 and d _i2 of all sensors in the m group of sensor arrays are all possibilities for designing the pole spacing in step 1) exhaustive or empirical selection;

3) Use the constructed sensor array to detect the concentration of gas with known concentration

A variety of single-component gas or multi-component mixed gas samples with different concentrations are prepared by using standard gases, and m groups of carbon nanotube three-electrode gas sensor arrays with different electrode spacings constructed by step 2) are used for detection in groups, and each measured The gas discharge ion current value of the gas sample;

4) Establish the electrode spacing of the sensor array and its corresponding gas detection result database

Use the d _i1 and d _i2 of each component sensor in the carbon nanotube three-electrode gas sensor array of all m groups, the gas discharge ion current value obtained by detecting the gas sample, and the concentration of the gas to be measured to establish the electrode spacing and the corresponding gas detection result database;

5) Establish a quantitative analysis model for the measured gas concentration

Adopt the support vector machine method, with the measured gas discharge ion current value in the database established in step 4) as input, with its corresponding gas concentration as output, set up the measured gas concentration quantitative analysis model;

6) Optimizing the electrode spacing of each component sensor in the sensor array

Adopt the measured gas concentration quantitative analysis model established by step 5) to analyze the gas concentration of all measured gas samples to obtain the detected concentration of the measured gas; calculate the difference between the detected concentration of the measured gas and its corresponding actual concentration, Then divide by the actual concentration of the gas to be measured to obtain the relative error of detecting the gas; using the particle swarm optimization algorithm, with the minimum relative error of the gas to be measured as the goal, the m group of carbon nanotube three electrodes constructed by step 2) The d _i1 and d _i2 of each component sensor in the gas sensor array are optimized, and finally the best electrode spacing of each sensor in the carbon nanotube three-electrode gas sensor array for detecting the gas is obtained.

For a single-component gas to be measured, multiple single carbon nanotube three-electrode gas sensors with different electrode spacings can be selected to detect a variety of gas samples with different concentrations. The carbon nanotube three-electrode gas sensor with the smallest detection error corresponds to The pole spacing is the most suitable pole spacing for the gas detection; multiple carbon nanotube three-electrode gas sensors can also be used to form a sensor array, and the gas samples with different concentrations can be detected in groups, and the carbon nanotube three-electrode gas sensor with the smallest detection error The electrode spacing corresponding to the electrode gas sensor is the most suitable electrode spacing for the gas detection.

For multi-component mixed gas, it is necessary to build a sensor array for detection. Generally, if there are several components to form a mixed gas, it is necessary to use carbon nanotube three-electrode gas sensors that are greater than or equal to the number of mixed gas components to form a sensor array. The embodiment is only illustrated by taking the mixed gas of nitric oxide (NO) and sulfur dioxide (SO ₂ ) as an example, and the number of components of the mixed gas can be expanded.

As shown in Figure 1, the electrode spacing optimization method of the carbon nanotube three-electrode gas sensor array adopts the following steps:

1) Design pole spacing

In the sensor array composed of 2 sensors, let the pole spacing between the first electrode and the second electrode of the first sensor be d ₁₁ , and the pole spacing between the second electrode and the third electrode be d ₁₂ ; the second sensor first The pole spacing between the electrode and the second electrode is d ₂₁ , the pole spacing between the second electrode and the third electrode is d ₂₂ , and there are two cases of equal spacing and unequal spacing for each sensor’s two pole spacing:

Equal spacing: that is, the distance between the two poles of a single sensor constituting the sensor array is equal, d ₁₁ , d ₁₂ , d ₂₁ and d ₂₂ start from 50 μm and increase in steps of 30 μm to form 50 μm, 80 μm, 110 μm, 140 μm, 170 μm, 200 μm, 230μm, 250μm, a total of 8 pole pitches.

Unequal spacing: that is, the spacing between the two poles of a single sensor that makes up the sensor array is not equal. For example, d ₁₁ starts from 50μm and increases in steps of 30μm, forming a total of 8 pieces of 50μm, 80μm, 110μm, 140μm, 170μm, 200μm, 230μm, and 250μm d ₁₁ value; d ₁₂ also increases from 50 μm with a step size of 30 μm, and also forms 8 d ₁₂ values of 50 μm, 80 μm, 110 μm, 140 μm, 170 μm, 200 μm, 230 μm, and 250 μm; theoretically, when d _i1 and d _i2 take When the above different values are combined, there are 56 possible combinations, where i=1,2.

For a single sensor, a total of 64 different pole-pitch combinations can be formed from the above equal and unequal pitches.

2) Construct a sensor array composed of sensors with different pole spacing

For the mixed gas of NO and SO ₂ , the number of sensors is selected to be 2. According to the existing experimental experience, from the electrode spacing designed in step 1), 6 pairs of different combinations of d _i1 and d _i2 are selected to construct 6 groups consisting of A carbon nanotube three-electrode gas sensor array composed of two sensors, where the combination of d _i1 and d _i2 is shown in Table 1:

Table 16 Combinations of different pole spacings of sensor arrays

group d ₁₁ /μm d ₁₂ /μm d ₂₁ /μm d ₂₂ /μm First group 50 150 150 150 Second Group 50 180 180 180 The third group 100 180 100 150 Fourth group 100 200 180 200 fifth group 150 180 180 180 The sixth group 150 200 200 200

3) Use the constructed sensor array to detect the concentration of gas with known concentration

Five kinds of mixed gas samples of NO and _SO2 with different concentrations were prepared by using standard gas, and their proportions are shown in Table 2. Six groups of carbon nanotube three-electrode gas sensor arrays constructed in Table 1 were used to detect five different concentrations of NO and _SO2 mixed gas samples, and a total of 30 groups of 60 gas discharge ion current values were obtained.

Table 25 mixed gases of NO and _SO2 with different concentrations

serial number NO/ppm SO ₂ /ppm 1 500 500 2 500 800 3 500 1000 4 800 800 5 800 1100

4) Establish the electrode spacing of the sensor array and its corresponding gas detection result database

The d _i1 and d _i2 of each sensor in each group of carbon nanotube three-electrode gas sensor array, the gas discharge ion current value obtained by detecting the gas sample, and the concentration of the measured gas are used to establish the electrode spacing and the corresponding gas detection result database;

5) Establish a quantitative analysis model for the measured gas concentration

Neglecting the influence of temperature and humidity on gas detection, adopt the support vector machine method, select the Gaussian kernel function, and in the database established in step 4), detect the discharge ions obtained by each carbon nanotube three _- electrode gas sensor of the mixed gas sample of NO and SO The flow value is input, and the corresponding measured gas concentration is used as the output to establish a quantitative analysis model of the measured gas concentration;

Step 6 Optimizing the electrode spacing of each component sensor in the sensor array

Adopt the measured gas concentration quantitative analysis model established by _step 5) to analyze the concentration of NO and _SO in 30 groups of measured gas samples, obtain NO and _SO detection concentration; The relative error is shown in Figure 2; the particle swarm optimization algorithm is used to target the minimum detection error of the gas to be measured, and each d _i1 and d _i2 in the 6 groups of carbon nanotube three-electrode gas sensor arrays constructed by step 2) are Optimizing the selection, it is found that the sensor array formed by the fifth group of pole spacing combinations has the smallest relative error in detecting NO and SO ₂ mixed gas. Therefore, in the final detection of NO and SO ₂ mixed gas using carbon nanotube three-electrode gas sensor array, two The optimum pole spacing d _i1 and d _i2 of the sensor are: 150 μm, 180 μm and 180 μm, 180 μm, respectively.

The pole spacing optimization method of the carbon nanotube three-electrode gas sensor proposed in this patent is also applicable to the optimization of the carbon nanotube three-electrode temperature and humidity sensor pole spacing, as long as the carbon nanotube three-electrode temperature or humidity sensor is used instead of the carbon nanotube three-electrode sensor. The electrode gas sensor constitutes a sensor array, and the temperature and humidity data obtained through detection are incorporated into the database established in step 4), and then steps 5) and 6) are performed.

The support vector machine method in step 5) can also be other regression methods such as neural network, least square regression, kernel method; The particle swarm optimization algorithm in step 6) can also be other optimization algorithms such as ant colony optimization algorithm, genetic algorithm .

Claims (2)

1. the die opening optimization method of carbon nano-tube three electrode gas sensor, to the first electrode and second electrode of carbon nano-tube three electrode gas sensor, second electrode and three electrode die opening are optimized, first electrode inside surface distribution carbon nano-tube film substrate of described carbon nano-tube three electrode gas sensor, second electrode is the extraction pole pole plate being provided with fairlead, 3rd electrode is collector, three electrodes are mutually isolated by insulation column, in three electrodes, the die opening scope of adjacent two electrodes is 50 μm ~ 250 μm, it is characterized in that adopting following Optimization Steps:

1) die opening is designed

In the sensor array be made up of n carbon nano-tube three electrode gas sensor, the first electrode of i-th sensor and the die opening of the second electrode are d _i1, the second electrode and three electrode die opening are d _i2, wherein, i=1,2 ..., n, when n is 1, then refers to Single Carbon Nanotubes three electrode gas sensor, the d of each sensor _i1and d _i2there are equidistant and unequal-interval two kinds of situations:

Equidistant: d _i1with d _i2equal, d _i1or d _i2increase progressively with step-length S from 50 μm, until d _i1or d _i2be more than or equal to 250 μm, S is the arbitrary integer between 0 μm-200 μm;

Unequal-interval: d _i1with d _i2unequal, d _i1with step-length S from 50 μm ₁increase progressively, until d _i1be more than or equal to 250 μm, d _i2with step-length S from 50 μm ₂increase progressively, until d _i2be more than or equal to 250 μm, S ₁and S ₂be the arbitrary integer between 0 μm-200 μm, work as d _i1when getting a value in aforementioned value, d _i2get and d _i1different values;

2) sensor array be made up of different die opening sensor is built

For the tested gas of single component or the mixed gas that is made up of R kind component, selected number of probes n, n>=R, adopt step 1) the middle die opening designed, build the carbon nano-tube three electrode gas sensor of m group n individual not equal pitch and unequal-interval respectively, form the carbon nano-tube three electrode gas sensor array of the different die opening of m group, the d of all the sensors in m group sensor array _i1and d _i2step 1) in all possible exhaustive or selection empirically of design die opening;

3) with building sensor array, Concentration Testing is carried out to concentration known gas

Calibrating gas is adopted to prepare single-component gas or the polycomponent mixed gas sample of multiple variable concentrations, adopting by step 2) the m group carbon nano-tube three electrode gas sensor array column split of different die openings that builds detects, and obtains the gas discharge ion flow valuve of each tested gas sample;

4) die opening of sensor array and corresponding gas detect result database thereof is set up

With the d of composition sensor each in all m group carbon nano-tube three electrode gas sensor arraies _i1and d _i2, detect gas discharge ion flow valuve that gas sample obtains and the concentration of tested gas sets up die opening and corresponding gas detect result database thereof;

5) tested gas concentration quantitative model is set up

Adopting support vector machine method, with step 4) tested gas discharge ion flow valuve is input in institute's building database, with its corresponding gas concentration for exporting, sets up tested gas concentration quantitative model;

6) die opening of each composition sensor in sensor array is optimized

Adopting by step 5) gas concentration of tested gas concentration quantitative model to all tested gas samples set up analyze, and obtains the detectable concentration of tested gas; Actual concentrations corresponding with it for the detectable concentration of tested gas is asked difference, then divided by the actual concentrations of tested gas, obtains the relative error detecting this gas; Adopt particle swarm optimization algorithm, minimum for target with the relative error of tested gas detect, to by step 2) each d forming sensor in the m group carbon nano-tube three electrode gas sensor array that builds _i1and d _i2be in optimized selection, the final best die opening obtaining each sensor in the carbon nano-tube three electrode gas sensor array detecting this gas.

2. the die opening optimization method of carbon nano-tube three electrode gas sensor according to claim 1, it is characterized in that: carbon nano-tube three electrode gas sensor can be replaced carbon nano-tube three electrode temperature sensors or carbon nano-tube three electrode humidity sensor, for detected temperatures or humidity.