Photoelectric dual-mode virtual electronic nose

Abstract

The invention discloses a photoelectric dual-mode virtual electronic nose, which adopts an MgO / ZnO composite film gas sensitive element to detect catalytic luminescence and resistance signals at the same time. By adopting the technical scheme of the invention, the CTL signal value, the resistance response value, the ratio of the CTL signal to the resistance response, the CTL response time and the CTL recovery time can be obtained through one-time measurement by only adopting one sensing element; and meanwhile, distinguishing of isobutanol, n-butanol, isobutylene alcohol and isobutyraldehyde is realized by combining principal component analysis, a support vector machine and a linear discriminant analysis algorithm.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic noses, and in particular relates to a photoelectric dual-mode virtual electronic nose. Background Art

[0002] The rapid detection and accurate identification of volatile organic compounds (VOCs) have always been a huge challenge in the field of chemical sensing. In recent years, the rapid development of electronic nose technology has brought hope for the rapid identification and detection of VOCs gases. However, in the face of complex and diverse VOCs gases with similar structures, traditional electronic nose systems often need to rely on a large number of gas sensors to ensure the accuracy and comprehensiveness of detection, which not only increases the cost and complexity of the system, but also limits its practical application. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a photoelectric dual-mode virtual electronic nose, which can simultaneously collect catalytic luminescence and resistance signals generated after the gas interacts with the gas sensitive element.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A photoelectric dual-mode virtual electronic nose uses a MgO / ZnO composite film gas sensor to simultaneously detect catalytic luminescence and resistance signals; it includes: an air generator, a VOCs generator, an automatic sampling module, a reaction chamber, a catalytic luminescence detector, a resistance signal sensing probe and a data processing system; wherein,

[0006] The air carrier gas continuously generated by the air generator is used as the power to drive the target gas generated by the vaporization of the VOCs generator, and the target gas is delivered to the reaction chamber in a timely and quantitative manner through the control of the automatic sampling module; when the target gas reaches the surface of the MgO / ZnO composite film gas sensor in the reaction chamber, the corresponding redox reaction occurs; the adsorption capacity and catalytic activity of the top material MgO of the MgO / ZnO composite film gas sensor are conducive to the formation of luminescent intermediates or luminescent products to generate a higher catalytic luminescence signal, which is captured by the catalytic luminescence detector; the bottom ZnO has a high electron mobility, which is conducive to the transfer of electrons released by gas molecules, that is, the electrons released during the redox process are transmitted to the external circuit through the bottom ZnO and captured by the resistance signal sensing probe; the optical signals and electrical signals captured by the catalytic luminescence detector and the resistance signal sensing probe will eventually be converted into digital signals by the data processing system and presented on the computer.

[0007] Preferably, the preparation of the MgO / ZnO composite film gas sensor comprises:

[0008] Preparation of slurry: weigh 0.1g ethyl cellulose and 0.1g zinc oxide respectively and place them in the same clean beaker, add 10mL anhydrous ethanol, ultrasonically oscillate for 10min, then add 10mL pinene alcohol and transfer to a magnetic stirrer and stir for 4h to obtain a mixed solution, finally place the mixed solution on a heating table, heat to 80℃, and maintain for about 2h to obtain a viscous zinc oxide slurry; at the same time, replace zinc oxide with magnesium oxide, and magnesium oxide slurry can be prepared according to the above steps.

[0009] Film preparation by scraping method: First, the interdigital electrode is placed in anhydrous ethanol and deionized water for ultrasonic cleaning for 10 minutes to remove surface oil and impurities; after standing and drying, it is placed on the workbench of the coating machine, and the electrode sheet is fixed with tape, and the zinc oxide slurry is evenly attached to the scraper; press the start button on the coating machine interface, and after the scraping is completed, start the heating table to heat up to 80°C, keep it for 20 minutes, and evaporate the excess slurry; replace the tape on the electrode sheet, attach the magnesium oxide slurry to the scraper and repeat the above operation; the evaporated film is placed in a vacuum muffle furnace and heated to 500°C at a heating rate of 15°C / min, kept for 2 hours, annealed, and placed in a dry and cool place for aging for 3 days after naturally cooling to room temperature, and finally a MgO / ZnO composite film-type gas sensor is obtained.

[0010] Preferably, the substrate material of the interdigital electrode is aluminum oxide, the size is 8×4 mm, and the conductive layer is gold.

[0011] Preferably, the scraping speed is set to 5 mm / s and the scraping thickness is set to 20 μm.

[0012] The invention adopts a MgO / ZnO composite film gas sensor, combines the strong catalytic luminescence activity of MgO and the excellent conductivity of ZnO, can detect catalytic luminescence and resistance signals at the same time, and realizes that only one sensing element is used, and rich analysis signals (including CTL signal value (SI), resistance response value (SR), ratio of CTL signal to resistance response (SIR), CTL response time (Tres) and CTL recovery time (Trec)) can be obtained through one measurement, and at the same time, algorithms such as principal component analysis (PCA), support vector machine (SVM) and linear discriminant analysis (LDA) are combined to realize accurate distinction of isobutanol, n-butanol, isobutenol and isobutyraldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0014] Figure 1 This is a schematic diagram of the structure of an urban photoelectric dual-mode virtual electronic nose according to an embodiment of the present invention;

[0015] Figure 2 The catalytic luminescence signal and resistance response measurement results of four gases, including (a) isobutanol, (b) n-butanol, (c) isobutenol, and (d) isobutyraldehyde;

[0016] Figure 3 The concentration-photoelectric ratio diagram of four gases;

[0017] Figure 4 The catalytic luminescence dynamic response curves of four gases; wherein, (a) is a schematic diagram of the response curves of different concentrations of isobutanol, (b) is a schematic diagram of the response curves of different concentrations of n-butanol, (c) is a schematic diagram of the response curves of different concentrations of isobutenol, and (d) is a schematic diagram of the response curves of different concentrations of isobutyraldehyde;

[0018] Figure 5 It is a three-dimensional PCA graph;

[0019] Figure 6 The PCA-SVM model fitting and validation data set classification results; (a) is a schematic diagram of the PCA-SVM model fitting results, and (b) is a schematic diagram of the PCA-SVM model validation data set classification results;

[0020] Figure 7 It is a typical score graph of LDA;

[0021] Figure 8 LDA model fitting and validation data set classification results. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Embodiment 1:

[0025] The embodiment of the present invention provides a photoelectric dual-mode virtual electronic nose, which adopts a MgO / ZnO composite film gas sensor, combines the strong catalytic luminescence activity of MgO and the excellent conductivity of ZnO, and can simultaneously detect catalytic luminescence and resistance signals.

[0026] like Figure 1 As shown, the photoelectric dual-mode virtual electronic nose of the embodiment of the present invention includes: an air generator, a VOCs generator, an automatic sampling module, a reaction chamber, a catalytic luminescence detector, a resistance signal sensing probe and a data processing system.

[0027] The air carrier gas continuously generated by the air generator is used as the power to drive the target gas generated by the vaporization of the VOCs generator, and the target gas is delivered to the reaction chamber in a timely and quantitative manner through the control of the automatic sampling module. When the target gas reaches the surface of the MgO / ZnO composite film gas sensor in the reaction chamber, the corresponding redox reaction occurs. The top material MgO of the MgO / ZnO composite film gas sensor has good adsorption capacity and catalytic activity, which is conducive to the formation of luminescent intermediates or luminescent products, thereby generating a higher catalytic luminescence signal and being captured by the catalytic luminescence detector; the bottom ZnO has a high electron mobility, which is conducive to the transfer of electrons released by gas molecules, that is, the electrons released during the redox process are more easily transmitted to the external circuit through the bottom ZnO and captured by the resistance signal sensing probe. The optical signals and electrical signals captured by the catalytic luminescence detector and the resistance signal sensing probe will eventually be converted into digital signals by the data processing system and presented on the computer.

[0028] As an implementation method of the present invention, the preparation steps of the MgO / ZnO composite film type gas sensor can be divided into two stages: slurry preparation and film formation:

[0029] Preparation of slurry: Weigh 0.1g ethyl cellulose and 0.1g zinc oxide respectively and place them in the same clean beaker, add 10mL anhydrous ethanol, ultrasonically vibrate for 10min, then add 10mL pinene alcohol and transfer to a magnetic stirrer and stir for 4h to obtain a mixed solution, finally place the mixed solution on a heating table, heat it to 80℃, and keep it for about 2h to obtain a viscous zinc oxide slurry. Replace zinc oxide with magnesium oxide and prepare magnesium oxide slurry according to the above steps.

[0030] Film preparation by scraping: First, the interdigital electrode (the base material is alumina, the size is 8×4mm, and the conductive layer is gold) is placed in anhydrous ethanol and deionized water for ultrasonic cleaning for 10 minutes to remove surface oil and impurities. After standing and drying, it is placed on the workbench of the coating instrument, and the electrode sheet is fixed with tape, and the zinc oxide slurry is evenly attached to the scraper. Set the scraping speed to 5mm / s and the scraping thickness to 20μm. Press the start button on the coating machine interface. After the scraping is completed, start the heating table to heat up to 80℃, keep it for 20min, and evaporate the excess slurry. Then replace the tape at the electrode sheet, attach the magnesium oxide slurry to the scraper and repeat the above operation. The evaporated film is placed in a vacuum muffle furnace and heated to 500℃ at a heating rate of 15℃ / min, kept for 2 hours, annealed, and placed in a dry and cool place for 3 days after cooling naturally to room temperature, and finally the MgO / ZnO composite film type gas sensor is obtained.

[0031] Application of optoelectronic dual-mode virtual electronic nose in identification of isobutanol, n-butanol, isobutenol and isobutyraldehyde

[0032] 1. Determination of characteristic quantities of catalytic luminescence signal and electrical signal

[0033] In order to qualitatively identify and analyze the gas, the collection of multi-dimensional characteristic quantity signals is essential. Under the conditions of working temperature of 290℃ and carrier gas flow rate of 550mL / min, gas with concentrations of 250, 500 and 750mg / m 3 The isobutyl alcohol, n-butyl alcohol, isobutylene alcohol and isobutylaldehyde gases are used to collect CTL signals and resistance response signals. Figure 2 As shown in (a), (b), (c), and (d), the photoelectric dual-mode virtual electronic nose generates a CTL signal and a resistance response signal simultaneously, and the generation of the two signals is synchronous.

[0034] S I Signal and S R The signal showed a linear trend within a certain concentration range, and it was inferred that S I Signal and S R The ratio between the signals may be a constant, namely the photoelectric ratio (S IR , defined as S I With S R Four gases of different concentrations were introduced into the reaction chamber to obtain the corresponding S I and S R The value of S is obtained by further calculation IR .like Figure 3 As shown, the photoelectric ratio of each gas does not change with the change of gas concentration, and its size is independent of gas concentration. Therefore, it can be used as a characteristic quantity to distinguish different gases.

[0035] Response / recovery time is a very important characteristic parameter for gas sensors. Response time is defined as the time taken from the baseline to the peak, and recovery time is defined as the time taken from the peak to the baseline. In the same gas sensor, the response time and recovery time for each gas should be different. Figure 4 (a), (b), (c), and (d) show the dynamic response curves of the gas sensor to the catalytic luminescence of four gases at three concentrations. res ), except for isobutylaldehyde which has a response time of 1 second, the response time of the other three gases is about 12.5 seconds. At the same time, the peak shape of isobutylaldehyde is different from the other three, and there is a plateau period of 11 seconds at the peak. The difference in response / recovery time is also an important basis for distinguishing different gases, so it can also be used as a characteristic quantity to distinguish different gases.

[0036] 2. Identification of isobutanol, n-butanol, isobutenol and isobutyraldehyde

[0037] The catalytic luminescence signals (S I ), resistance response (S R ), photoelectric ratio (S IR ), catalytic luminescence response time (T res ) and catalytic luminescence recovery time (T rec ) as the feature quantity, combined with principal component analysis, support vector machine and linear discriminant analysis, the accurate distinction between isobutanol, n-butanol, isobutenol and isobutyraldehyde can be achieved.

[0038] Establishment of the data set: The five characteristic values ​​of the four gases at different concentrations were obtained by the photoelectric dual-mode virtual electronic nose (the detected concentrations are shown in Table 1). Each concentration was tested three times in parallel to form a 51×5 data set.

[0039] Principal component analysis: Using statistical software, we performed principal component analysis on the data set (the number of principal components extracted was 3), and we obtained Figure 5 The data points of various gases are in different planes and do not interfere with each other within their respective concentration ranges. The established PCA model can intuitively display the structure of the data set.

[0040] Support vector machine: The 51×3 data set (PC1, PC2 and PC3) after PCA dimension reduction is used as the SVM data set, 34 data sets are selected as training data sets, and the remaining 17 data sets are used as validation data sets. The radial basis function (RBF) is used as the kernel function of the model. The PCA-SVM model results show that the accuracy of the SVM model fitting is 100% when judging whether the classification is correct, and the classification accuracy of the validation data set is also 100%. The specific classification results are as follows Figure 6 As shown in (a) and (b), all gases are correctly classified with an accuracy rate of 100%.

[0041] Linear discriminant analysis: The gas type is used as the classification category, and the S I , S R , S IR , T res and T rec As feature quantity, 34 sets of data were selected as training data sets, and the LDA model was constructed for training. The remaining 17 sets of data were selected as validation data sets. The analysis results showed that the error rate of LDA model cross validation was 0.00%. A three-dimensional scatter plot was drawn for the typical score 1, typical score 2 and typical score 3 of the training data set (see Figure 7 ), the four gases of different concentrations gathered in different spaces, and no overlapping areas were found. All samples in the validation dataset were correctly classified with an accuracy rate of 100% (see Figure 8 ).

[0042] Table 1

[0043]

[0044] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A photoelectric dual-mode virtual electronic nose, characterized in that: The MgO / ZnO composite film gas sensor is used to detect catalytic luminescence and resistance signals at the same time; it includes: an air generator, a VOCs generator, an automatic sampling module, a reaction chamber, a catalytic luminescence detector, a resistance signal sensing probe and a data processing system; among which, The air carrier gas continuously generated by the air generator is used as the power to drive the target gas generated by the vaporization of the VOCs generator, and the target gas is delivered to the reaction chamber in a timely and quantitative manner through the control of the automatic sampling module; when the target gas reaches the surface of the MgO / ZnO composite film gas sensor in the reaction chamber, the corresponding redox reaction occurs; the adsorption capacity and catalytic activity of the top material MgO of the MgO / ZnO composite film gas sensor are conducive to the formation of luminescent intermediates or luminescent products to generate a higher catalytic luminescence signal, which is captured by the catalytic luminescence detector; the bottom ZnO has a high electron mobility, which is conducive to the transfer of electrons released by gas molecules, that is, the electrons released during the redox process are transmitted to the external circuit through the bottom ZnO and captured by the resistance signal sensing probe; the optical signals and electrical signals captured by the catalytic luminescence detector and the resistance signal sensing probe will eventually be converted into digital signals by the data processing system and presented on the computer.

2. The optoelectronic dual-mode virtual electronic nose according to claim 1, characterized in that: The preparation of MgO / ZnO composite film gas sensor includes: Preparation of slurry: weigh 0.1g ethyl cellulose and 0.1g zinc oxide respectively and place them in the same clean beaker, add 10mL anhydrous ethanol, ultrasonically oscillate for 10min, then add 10mL pinene alcohol and transfer to a magnetic stirrer and stir for 4h to obtain a mixed solution, finally place the mixed solution on a heating table, heat to 80℃, and maintain for about 2h to obtain a viscous zinc oxide slurry; at the same time, replace zinc oxide with magnesium oxide, and magnesium oxide slurry can be prepared according to the above steps. Film preparation by scraping method: First, the interdigital electrode is placed in anhydrous ethanol and deionized water for ultrasonic cleaning for 10 minutes to remove surface oil and impurities; after standing and drying, it is placed on the workbench of the coating machine, and the electrode sheet is fixed with tape, and the zinc oxide slurry is evenly attached to the scraper; press the start button on the coating machine interface, and after the scraping is completed, start the heating table to heat up to 80°C, keep it for 20 minutes, and evaporate the excess slurry; replace the tape on the electrode sheet, attach the magnesium oxide slurry to the scraper and repeat the above operation; the evaporated film is placed in a vacuum muffle furnace and heated to 500°C at a heating rate of 15°C / min, kept for 2 hours, annealed, and placed in a dry and cool place for aging for 3 days after naturally cooling to room temperature, and finally a MgO / ZnO composite film-type gas sensor is obtained.

3. The optoelectronic dual-mode virtual electronic nose according to claim 2, characterized in that: The substrate material of the interdigital electrode is alumina, the size is 8×4 mm, and the conductive layer is gold.

4. The optoelectronic dual-mode virtual electronic nose according to claim 3, characterized in that: The coating speed was set to 5 mm / s and the coating thickness was set to 20 μm.

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