CN110849947A

CN110849947A - Fruit deterioration detection system and construction method and detection method thereof

Info

Publication number: CN110849947A
Application number: CN201911142755.4A
Authority: CN
Inventors: 陶佰睿; 苗凤娟; 苗瑞; 李雪
Original assignee: Qiqihar University
Current assignee: Qiqihar University
Priority date: 2019-11-20
Filing date: 2019-11-20
Publication date: 2020-02-28
Anticipated expiration: 2039-11-20
Also published as: CN110849947B

Abstract

The invention discloses a fruit deterioration detection system and a construction method and a detection method thereof, wherein the fruit deterioration detection system is based on a photoelectrochemical sensor and comprises a microcontroller module, a light source control module, a photoelectrochemical sensor module, a data transmission module, a background server module, a data calibration module, a human-computer interaction module and a power supply module; the specific construction method comprises the steps of preparing a photoelectrochemical sensor, testing the performance of the photoelectrochemical sensor, designing hardware and software of a detection system, and judging the freshness of the fruits by detecting the trace change of the ethanol released by the fruits under the anaerobic respiration action by using the photoelectrochemical sensor; then, the acquired data is sent to a background through a microcontroller and a wireless transmission technology; finally, the background server processes data to obtain stable data and visually displays the detection result to a tester through a human-computer interaction interface; the invention can well assist people in judging the freshness of fruits and improve the life quality of people.

Description

Fruit deterioration detection system and construction method and detection method thereof

Technical Field

The invention relates to the technical field of fruit deterioration detection systems, in particular to a fruit deterioration detection system and a construction method and a detection method thereof.

Background

Fruits are essential food in life of people, along with social progress and continuous improvement of living standard of people, people pay more and more attention to freshness of fruits, the taste of the fruits can be influenced due to deterioration of the fruits, toxic substances are generated due to metabolism of microorganisms in rotten parts of the fruits, most of the toxic substances are mould fungi, after the mould fungi invade, peels can be softened, scabs, subsidence and pulp softening are formed, fermentation are carried out, some mould fungi also utilize nutrition of the fruits to generate new toxins, such as penicillium and aspergillus to generate patulin, aspergillus niger can generate aflatoxin and the like, some poison effects such as carcinogenesis, teratogenesis and the like on people can be caused, and some harm to brain and central nervous system can be caused. The fruit deterioration can also generate other substances which are not even harmful, such as ethanol and the like, and the existing judging method for the fruit deterioration generally observes the states of the texture structure and the like of the fruit surface by naked eyes, so that the accuracy is difficult to guarantee.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a fruit deterioration detection system based on a photoelectrochemical sensor, a construction method and a detection method thereof, which can well assist people in judging the freshness of fruits.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

fruit detecting system that deteriorates, its characterized in that: the system comprises a microcontroller module, a light source control module, a photoelectrochemistry sensor module, a data transmission module, a background server module, a data calibration module, a man-machine interaction module and a power supply module;

the microcontroller module comprises a microcontroller and a peripheral circuit, and the microcontroller module realizes the control of the whole system;

the light source control module provides a light source for the photoelectrochemistry sensor module;

the photoelectrochemical sensor module converts the concentration of the ethanol released by the fruits into a current signal and feeds the current signal back to the microcontroller module for processing and analysis;

the data transmission module realizes wireless data transmission;

the background server module analyzes the uploaded data, then stores the data into a database, and waits for the calling of the human-computer interaction module;

the data calibration module calibrates data using a machine learning procedure, the machine learning procedure including SVW perceptron algorithm and time series analysis;

the human-computer interaction module visually displays the detected data to a tester;

the power supply module supplies power to the whole system;

the utility model discloses a fruit testing device, including a photoelectric chemical sensor module, microcontroller module control light source control module does the photoelectrochemistry sensor module provides the light source, the photoelectrochemistry sensor module detects the ethanol concentration that fruit released and converts the current signal feedback into to utilize the data transmission module to send data to the backstage server module through wireless transmission technology, the data calibration module is located in the backstage server module, it is right the data that the backstage server module received calibrate, the backstage server module with the human-computer interaction module links to each other, gives the tester with the audio-visual demonstration of the data after calibrating.

Further, the peripheral circuit of the microcontroller module comprises a light source control circuit, a sensor weak current detection circuit, a data transmission circuit and a power supply circuit; the micro-controller module controls the light source control module to provide a light source for the photoelectrochemistry sensor module through the light source control circuit, the sensor weak current detection circuit collects current signals sent by the photoelectrochemistry sensor module, converts the current signals into digital signals and transmits the digital signals to the controller, then data are transmitted to the data transmission module through the data transmission circuit, and the power circuit provides a power supply for the micro-controller module.

Furthermore, the sensor weak current detection circuit comprises an I-V conversion circuit, an amplifying circuit, a sensor weak current detection filter circuit and an A/D conversion circuit; the collected current signals are converted into photoelectric voltage through the I-V conversion circuit, the photoelectric voltage is amplified through the amplifying circuit, then the amplified photoelectric voltage is filtered to remove noise waves through the filter circuit, and finally the collected signals are converted into digital signals through the A/D conversion circuit.

Further, the working electrode of the photoelectrochemical sensor used by the photoelectrochemical sensor module is a Pd-ZnO/Ni electrode.

Further, the construction method of the fruit deterioration detection system is characterized by comprising the following steps:

s1: preparing a photoelectric chemical sensor by a hydrothermal method and an electrochemical deposition method;

s2: testing the performance of the photoelectrochemical sensor;

s3: detecting the design of a system hardware circuit;

s4: and (5) detecting system software programming.

Further, the specific operation of step S1 includes:

s11: shearing a foam nickel plate into a foam nickel sheet with the size of 1cm3, ultrasonically cleaning and drying;

s12: ultrasonically cleaning and drying the ITO conductive glass;

s13: respectively growing zinc oxide nano hexagonal prisms on the processed foamed nickel and ITO conductive glass substrates;

s14: repeatedly washing and drying the prepared zinc oxide nano hexagonal prism electrode;

s15: taking a foamed nickel sheet with a zinc oxide nanometer hexagonal prism electrode and ITO conductive glass as leads at one corner by using a copper wire, smearing silver paste at the joint, and putting the joint into a drying box for drying; completely isolating the copper wire from the silver paste by using epoxy resin by adopting a small amount of method for many times, and drying after sealing glue each time;

s16: carrying out electro-deposition on palladium ions on a zinc oxide nano hexagonal prism electrode growing on a foamed nickel and ITO conductive glass substrate;

s17: washing and drying the zinc oxide nano hexagonal prism electrode subjected to palladium ion electrodeposition, and finishing the manufacture of the sensor electrode;

s18: and packaging the prepared foamed nickel, the ITO conductive glass and the sensor electrode together through PVA solid electrolyte, and finishing the manufacturing of the photoelectrochemical sensor.

Further, the performance test of the photo-electrochemical sensor in the step S2 includes a physical characterization test, an electrochemical test, and a test of sensitivity, selectivity and stability; the physical characterization test comprises a scanning electron microscope, an energy dispersion X-ray spectrum, X-ray diffraction and an X-ray photoelectron spectrum test; the electrochemical test comprises the steps of exploring the change relation between the photocurrent and the ethanol concentration by a chronoamperometry method and exploring the change relation between the impedance and the ethanol concentration by an alternating current impedance method.

Further, the system hardware circuit in step S3 includes a microcontroller core circuit and a microcontroller peripheral circuit, where the microcontroller core circuit includes a microcontroller chip, a crystal oscillator circuit, a microcontroller chip filter circuit, and a reset circuit.

Further, the system software program in step S4 includes a main program, a light source control subprogram, a sensor micro-current acquisition signal subprogram, a data transmission module subprogram, a machine learning program, and a human-computer interaction interface program; the main program is arranged in the microcontroller module, the light source control subprogram is arranged in the light source control module, the sensor micro-current acquisition signal subprogram is arranged in the photoelectrochemical sensor module, the data transmission module subprogram is arranged in the data transmission module, the machine learning program and the human-computer interaction interface program are arranged in the data calibration module, and the human-computer interaction interface program is arranged in the human-computer interaction module.

Further, the detection method of the fruit deterioration detection system is characterized by comprising the following steps:

s1: debugging a fruit deterioration detection system to ensure that the fruit deterioration detection system can be normally used;

s2: wrapping fruits to be tested and the photoelectrochemical sensor by a preservative film;

s3: detecting the concentration of ethanol released by the fruits by using a fruit deterioration detection system;

s4: and the test result after the data calibration is displayed on the man-machine interaction module for a user to check.

The invention has the beneficial effects that:

1. the core technology of the fruit deterioration detection system is a photoelectrochemical sensor, the sensitivity of a Pd-ZnO/Ni electrode to ethanol is utilized to detect the concentration of the ethanol released after the fruits deteriorate, the detection precision is high, the selectivity is good, people can be better assisted in judging the freshness of the fruits in daily life, people can feel more confident when eating the fruits, and the life quality of the people is improved;

2. the design of the fruit deterioration detection system based on the photoelectrochemical sensor provides practical support for the development of electronic label type fruit packages and the development of intelligent sensors.

3. The invention utilizes an embedded technology and a narrow-band Internet of things wireless transmission technology on the basis of photoelectrochemistry, and builds the whole system to enable the acquired weak photoelectric stream data to be transmitted in real time; by applying a software programming method and a machine learning artificial intelligence technology, the data is displayed to the detector more stably, accurately and intuitively.

4. The fruit deterioration detection system is simple in overall operation, convenient to carry, low in price and good in practicability.

Drawings

FIG. 1 is a circuit logic and functional block diagram of a fruit spoilage detection system of the present invention;

FIG. 2 is a flow chart of a technical route of the present invention;

FIG. 3 is a topographical representation of a sensor electrode prepared in accordance with the present invention;

FIG. 4 is an EDS test chart of the Pd/ZnO/Ni electrode of the present invention;

FIG. 5 is an XRD test pattern of the Pd/ZnO/Ni electrode of the present invention;

FIG. 6 is an XPS test chart of the Pd/ZnO/Ni electrode of the present invention;

FIG. 7 is a diagram showing the result of cyclic voltammetry test for Pd/ZnO/Ni electrodes of the present invention;

FIG. 8 is a graph comparing the sensitivity of the Pd-ZnO/Ni electrode of the present invention to ethanol with and without light;

FIG. 9 is a graph showing the change of photocurrent when 0.1 μ M ethanol was added to the Pd-ZnO/Ni electrode according to the present invention;

FIG. 10 is a graph showing the change of photocurrent when 0.02 μ M ethanol was added to the Pd-ZnO/Ni electrode according to the present invention;

FIG. 11 is a schematic view of a microtube mechanistic analysis of the sensor of the present invention;

FIG. 12 is a block diagram of the hardware components of the detection system of the present invention;

FIG. 13 is a flowchart illustrating the design of a main program according to the present invention;

FIG. 14 is a flow chart of the light source control module programming of the present invention;

FIG. 15 is a flow chart of a sensor micro-current acquisition programming of the present invention;

FIG. 16 is a flow chart of the data transfer module programming of the present invention;

FIG. 17 is a flowchart of the human-computer interaction interface programming of the present invention;

FIG. 18 is a graph illustrating the correlation between the measured ethanol concentration and the voltage response according to one embodiment of the present invention;

FIG. 19 is a histogram of current response versus days for the second embodiment of the present invention.

FIG. 20 is a histogram of current response versus days for the third embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the following further describes the technical solution of the present invention with reference to the drawings and the embodiments.

As shown in the attached figure 1, the fruit deterioration detection system comprises a microcontroller module, a light source control module, a photoelectrochemistry sensor module, a data transmission module, a background server module, a data calibration module, a human-computer interaction module and a power supply module;

the data transmission module realizes wireless data transmission;

the data calibration module calibrates data;

the power supply module supplies power to the whole system;

the micro-controller module controls the light source control module to provide a light source for the photoelectrochemical sensor module, the photoelectrochemical sensor module detects that the concentration of ethanol released by fruits is converted into a current signal and feeds the current signal back to the micro-controller module, and the data transmission module is used for transmitting data to the background server module through a wireless transmission technology, and the background server module is connected with the human-computer interaction module and visually displays the data to a tester;

further, the peripheral circuit of the microcontroller module comprises a light source control circuit, a sensor weak current detection circuit and a data transmission circuit; the micro-controller module controls the light source control module to provide a light source for the photoelectrochemical sensor module through the light source control circuit, the sensor weak current detection circuit collects current signals sent by the photoelectrochemical sensor module, converts the current signals into digital signals, transmits the digital signals to the controller, and transmits the data to the data transmission module through the data transmission circuit.

Furthermore, the sensor weak current detection circuit comprises an I-V conversion circuit, an amplifying circuit, a filter circuit and an A/D conversion circuit; the collected current signals are converted into photoelectric voltage through the I-V conversion circuit, the photoelectric voltage is amplified through the amplifying circuit, then the amplified photoelectric voltage is filtered to remove noise waves through the filter circuit, and finally the collected signals are converted into digital signals through the A/D conversion circuit.

Further, the technical route of the invention is shown in figure 2, and the construction method of the fruit deterioration detection system comprises the following steps:

1. preparing a photoelectric chemical sensor by a hydrothermal method and an electrochemical deposition method;

specifically, the steps of preparing the photoelectrochemical sensor may specifically be:

s11: cutting the foam nickel plate into 1cm³Putting the foam nickel sheet with the size into deionized water, and ultrasonically cleaning for 5min to remove water-soluble impurities; ultrasonically cleaning in acetone for 10min to remove liposoluble impurities; ultrasonic cleaning in deionized water for 5min, ultrasonic cleaning in 2mol/L dilute hydrochloric acid for 10min to remove oxides, and washing residual reagent with a large amount of deionized water; drying the treated foam nickel in a closed drying box at 60 ℃ for 30 min;

s12: putting the purchased ITO conductive glass into toluene for ultrasonic treatment for 15min to remove oil stains, then putting the ITO conductive glass into acetone for ultrasonic cleaning for 30min to remove residual toluene, and then ultrasonic cleaning in deionized water for 15min to remove residual acetone; drying the treated ITO conductive glass in a closed drying box at 60 ℃ for 30 min;

specifically, 0.35g of zinc acetate and 50ml of deionized water are weighed and put into a beaker for ultrasonic treatment for 15min for standby; 0.74g of zinc nitrate hexahydrate, 1.08g of hexamethyltetramine and 50ml of deionized water are weighed and put into a beaker for ultrasonic treatment for 15min for standby. And respectively putting the processed foamed nickel and the ITO conductive glass into the prepared zinc acetate solution for 3-5min, and then performing high-temperature annealing at 200 ℃ to generate a zinc oxide nanocrystal seed layer. Then placing the annealed zinc oxide nano crystal seed layer into a high-temperature high-pressure kettle, pouring the prepared mixed solution of zinc nitrate hexahydrate and hexamethyltetramine into the high-temperature high-pressure kettle, and carrying out hydrothermal treatment at the temperature of 95 ℃ for 5 hours to generate a zinc oxide nano hexagonal prism;

s14: repeatedly washing the prepared zinc oxide nano hexagonal prism electrode in a closed drying box, and drying at 60 ℃ for 30 min;

s15: a foamed nickel sheet with a zinc oxide nanometer hexagonal prism electrode and ITO conductive glass are led out at one corner by a copper wire, and a proper amount of silver paste is smeared at the joint to enhance the conductivity; drying in a 60 deg.C drying oven for 30 min. Completely isolating copper wires and silver paste by using epoxy resin, adopting a method of multiple times and a small amount of adhesive sealing to prevent large-area diffusion, drying at 60 ℃ after each adhesive sealing, and sealing for 6 times at intervals of 30 min;

s16: performing electro-deposition on palladium ions on the zinc oxide nano hexagonal prism grown on the foamed nickel and ITO conductive glass substrate;

specifically, 1.169g of Ethylene Diamine Tetraacetic Acid (EDTA), 0.375g of ammonium chloride and 20ml of deionized water are weighed, placed in a beaker for ultrasonic treatment for 15min to generate a flocculent solution, and then ammonia water is added dropwise to change the solution into a neutral solution; weighing 0.02g of palladium chloride, adding the palladium chloride into a neutral solution, and carrying out ultrasonic treatment for 15 min; putting the dried foam nickel electrode into the prepared solution, connecting to a programmable direct current power supply, setting the mode to be a constant current mode, wherein the current density is 10mA/cm^-2The electroplating time is 3 minutes; the platinum electrode is used as the positive electrode of electroplating, and the working electrode is used as the negative electrode of electroplating.

S17: repeatedly washing with deionized water after the electroplating is finished, washing off the residual solution on the surface of the electrode, then placing the electrode into a drying box for drying for 30min at 60 ℃, and finishing the manufacture of the sensor electrode after the drying;

s18: and packaging the prepared foamed nickel, ITO conductive glass and a sensor electrode together by PVA solid electrolyte, and finishing the manufacturing of the Pd/ZnO/Ni photoelectrochemical sensor.

2. Testing the performance of the photoelectrochemical sensor;

specifically, the sensor electrode is physically characterized by a Scanning Electron Microscope (SEM), an energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS); then, through chemical tests, a time current method (CA) is used for researching the change relation between the photocurrent and the ethanol concentration, and an alternating current impedance method (EIS) is used for researching the change relation between the impedance and the ethanol concentration.

The Scanning Electron Microscope (SEM) of the sensor electrode prepared by the preparation method is shown in figure 3. FIG. 3(a) is a scanning electron microscope image of zinc oxide nanorods (ZnO NRs) on a nickel foam network substrate at low magnification, which shows that the ZnO NRs arrays uniformly and vertically grow on the nickel foam network substrate. FIGS. 3b and 3c show high magnification scanning electron microscope images of ZnO NRs on a foamed nickel network substrate, which are structured as hexagonal prisms. The uniform nanorod hexagonal prism structure facilitates absorption of ultraviolet light. FIG. 3d shows an SEM image of a ZnO NRs array from the side, which is about 500 μ M in length. Fig. 3e and 3f show high-power scanning electron microscope images of Pd nanoparticles on an electrode, which can well observe that Pd ions are in irregular crystals and dense spherical clusters after electrodeposition, but irregular Pd nanoparticles are more favorable for adsorbing ethanol molecules.

FIG. 4 (see FIG. 4 of the substantive review references) shows the element composition and element distribution EDS of the Pd/ZnO/Ni electrode, which is clearly seen to be composed of Zn, Pd, O, Ni elements. It can be seen from the image that the elements of zinc, palladium and oxygen are uniformly distributed on the surface of the electrode.

FIG. 5 (see FIG. 5 of the substantive examination references) shows XRD spectra of ZnO/Ni and Pd/ZnO/Ni. Diffraction peaks at 2 θ of 31.4, 34.02, 34.46, 47.64, 56.62, 62.82, 67.92, 69.02 correspond to the zinc oxide planes of (100), (002), (101), (102), (110), (103), (112), and (201), respectively. Since the Pd nanoparticles can shield ZnO NRs, no ZnO NRs peak is detected by Pd/ZnO/Ni. The diffraction peaks are 40.08, 46.56 and 68.30 in 2 theta and three strong peaks originated from foamed nickel.

To further understand the chemical composition and valence of the near-surface elements, XPS analysis was performed, and as shown in fig. 6 (see fig. 6 in the parenchymal examination reference), fig. 6(a) shows the presence of Pd, Zn, O, C, Ni elements in the Pd/ZnO/Ni nanocomposite, which corresponds to the EDS results, and the valence of these elements in the nanocomposite was studied. In the Pd three-dimensional spectrum shown in FIG. 6(b), the two peaks of 341.86eV and 335.56eV are Pd 3d3/2 and Pd 3d5/2, respectively, and the splitting is about-6 eV, which is the characteristic peak of metallic Pd. FIG. 6(c) shows that the binding energies of 1021.4eV and 1045.1eV are assigned to Zn 2p1/2 and Zn 2p3/2, respectively, indicating the presence of Zn2+ in the Pd/ZnO/Ni nanocomposite. FIG. 6(d) shows that O1s is the two oxygen supply peaks for high resolution spectral decomposition, the peak at 531.4eV is due to O2-of the Zn-O band, and the weak peak at 532.5eV corresponds to the surface-oh group. The results of XPS spectroscopy indicated the formation of a Pd/ZnO nanocomposite on a foamed nickel substrate.

Further, the sensor electrode is subjected to micro-mechanism analysis through photoelectrochemical tests, all the photoelectrochemical tests are carried out on an electrochemical workstation, and a three-electrode system and a two-electrode system are adopted;

specifically, Cyclic Voltammetry (CV) of the electrode in 1M Na2SO4 electrolyte confirmed the catalytic oxidation of the Pd/ZnO/Ni electrode to ethanol as shown in FIG. 7 (see FIG. 7 for substantive examination) at 50mVs^-1The electrode has catalytic oxidation reaction on the ethanol, which is confirmed by the fact that the oxidation peak current is obviously increased after the ethanol is added as can be seen by comparing CV graphs of ethanol addition and ethanol non-addition and whether light irradiation is added or not. Further increase in oxidation peak current was observed with the addition of ethanol under light conditions, demonstrating the photoelectric effect of the electrode and promoting catalytic oxidation of ethanol.

The graph comparing the sensitivity of the Pd-ZnO/Ni electrode to ethanol with and without light is shown in fig. 8 (refer to fig. 8 in the substantive review reference), in fig. 8a, the influence of the ultraviolet light on the catalytic reaction of the electrode is further proved by the step experiment in the chronoamperometric mode, in fig. 8(b), the electrode after light addition is more sensitive to ethanol as can be seen from the fitting result, mainly because the ultraviolet light excites the electron transition in the ZnO NRs, and the catalytic oxidation capability of the Pd nanoparticles is improved.

The photocurrent test of fig. 9 (see fig. 9 of the substantive review reference) was conducted in a three-electrode state with a platinum electrode as the counter electrode, a mercury oxide mercury electrode as the reference electrode, and a Pd-ZnO/Ni electrode as the working electrode. The photocurrent was tested in a chronoamperometric mode (CA) mode of the electrochemical workstation with a bias voltage of 0V. From FIG. 9(a), it can be clearly seen that the photocurrent generated by the Pd/ZnO/Ni electrode during the UV irradiation process depends on the concentration of ethanol. The photocurrent increased with each addition of 0.1 μ M ethanol, indicating that the Pd-ZnO/Ni electrode had good sensitivity to ethanol. The intrinsic reason for this is because Pd nanoparticles on ZnO NRs react with ethanol, consuming holes, increasing photocurrent. It can be seen from FIG. 9(b) that the increase of photocurrent after the first three ethanol additions is very severe is gradually reduced, because the surface activity of the electrode is limited and the reaction speed is high initially, but with the addition of ethanol, the electrode surface active substance reacts with ethanol, so the reaction speed is correspondingly reduced.

Further, by adding ethanol, a relationship between the photocurrent and the ethanol concentration was established, as shown in fig. 10 (refer to fig. 10 in the substantive review reference). FIG. 10(a) is a graph showing the change in photocurrent with the increase in ethanol concentration per 0.02. mu.M of ethanol added to the electrolyte. Fig. 10(b) is a graph to which the average peak value of photocurrent was fitted, and it can be seen that the linear correlation was good at the points other than the first point which contained no ethanol. This further demonstrates that Pd-ZnO/Ni electrodes have good sensitivity to ethanol.

In summary, ZnO NRs is an n-type semiconductor, and the morphology thereof has a certain influence on the sensitivity to ultraviolet light. In the structure of the present invention, ZnO NRs has a desirable form, and energy in ultraviolet light can be absorbed by ZnO NRs. Under illumination, electrons (e-) in the valence band of ZnO NRs are excited to the conduction band, and the electrons move in one direction to generate current to provide energy.

The schematic diagram of the microtube mechanism analysis of the sensor is shown in FIG. 11 (refer to FIG. 11 in the substantive examination reference), and as shown in FIG. 11(a), after ZnO NRs are contacted with the solution, the oxidation-reduction reaction is promoted by ultraviolet irradiation. In this case, the photocurrent exhibited three stages, initial rapid increase, stabilization, and decrease. These three phases are related to the photogenerated electrons under ultraviolet light, the recombination of photogenerated electron-hole pairs, and the balance between the generation and recombination of electron-hole pairs, respectively. The photocurrent of the Pd/ZnO/Ni electrode is related to the concentration of ethanol, the working mechanism of the Pd/ZnO/Ni photoanode is shown in figure 11(b), and ordered ZnO NRs are used as light absorption materials to generate photoinduced electron-hole pairs under illumination. Electrons (e-) in the valence band of ZnO NRs are excited to the conduction band, and holes (h +) in the valence band migrate to the surface of the electrode and accumulate to participate in ethanol oxidation. Under the action of the three-dimensional foamed nickel network, photosensitive electrons tend to move to single ZnO NRs, and photocurrent is generated. The photo-induced hole improves the catalytic oxidation capacity of the Pd nano particles to the ethanol, and the photo-induced hole is consumed by the Pd catalytic ethanol oxidation. Therefore, more electron photocurrent is generated. Therefore, the self-powered sensing of the Pd/ZnO/Ni electrode to ethanol can be realized by utilizing the sensitivity of ZnO NRs to ultraviolet light and a 3D Pd/ZnO/Ni heterostructure.

3. Detecting the design of a system hardware circuit;

the hardware main components of the system comprise: an Arduino micro-control core circuit; a light source control circuit; a sensor weak current detection circuit; a data transmission circuit; the power circuit is composed of several parts. The Arduino microcontroller and the peripheral circuit are mainly used for controlling the normal operation of the whole system. The main function of the light source control circuit is to provide a light source for the photoelectrochemical sensor. The weak current detection circuit of the sensor mainly detects the photocurrent generated by the sensor and comprises an I-V conversion circuit, an amplifying circuit, a filter circuit and an A/D conversion circuit. The I-V conversion circuit is used for converting a current signal output by the photoelectrochemical sensor into a voltage signal so as to facilitate the subsequent processing; the voltage amplifying circuit is mainly used for further increasing the voltage and facilitating measurement; the filter circuit mainly filters clutter in the system; the A/D conversion circuit samples the analog signal output by the filter circuit and then transmits the output data to the Arduino single chip microcomputer for processing. The data transmission circuit mainly transmits data acquired by the system to a background for analysis and processing, and the circuit is mainly completed by a BC-95 module in NB-IoT wireless transmission. The power supply circuit mainly supplies power to the whole system. The hardware composition block diagram of the system is shown in fig. 12. The power supply circuit mainly functions to supply power to all modules in the system. However, since the NB-IOT module in the system needs to provide 3.3V power supply and the Arduino microcontroller needs 5V power supply to supply power, the voltage conversion circuit and the boost circuit are designed to enable the system to operate normally. The main purpose of the light source control circuit is to provide a light source for the photoelectrochemical sensor, but the Arduino single chip microcomputer cannot directly control strong electricity, so that a method of controlling strong electricity by weak electricity is adopted, and the relay is controlled by the Arduino single chip microcomputer so as to control the light source. The weak current detection circuit of the sensor mainly utilizes an I-V conversion circuit, an amplifying circuit, a filter circuit and an A/D conversion circuit to detect weak current signals generated by the photoelectrochemical sensor, and the change of the concentration of the ethanol is detected through the change of micro current. The functions of the circuits are as follows: (1) the I-V conversion circuit is mainly used for converting a weak photocurrent signal generated by the photoelectrochemical sensor into a voltage signal; (2) the amplifying circuit is mainly used for amplifying signals output by the I-V conversion circuit, and can amplify microvolt and millivolt voltages by utilizing a high-precision microvolt amplifier AD620 module, wherein the amplification factor is 1.5-10000 times, the amplifying circuit is high in precision, low in offset and good in linearity, and the precision can be improved by zeroing; (3) the filter circuit filters and amplifies the signal processed by the amplifying circuit to reduce the influence of clutter on the measurement signal; (4) the A/D conversion circuit converts the analog quantity output by the filter circuit into digital quantity and transmits the digital quantity to the Arduino single chip microcomputer, the Arduino single chip microcomputer is used for packaging data, and the data are transmitted to the background through the data transmission circuit to be analyzed and processed. The data transmission circuit mainly utilizes a BC95 module in NB-IoT to wirelessly upload data.

S4: detecting system software programming;

specifically, the system software programming comprises three aspects of system software programming, machine learning programming and human-computer interaction interface programming. The system software program design also comprises a main program design, a light source control subprogram design, a sensor micro-current acquisition signal subprogram design and a data transmission module subprogram design; the machine learning programming comprises SVW perceptron algorithm and time sequence analysis; the human-computer interface program design mainly utilizes Visual Studio to build a platform to enable detected data to be visually displayed to a tester.

As can be seen from the hardware block diagram of the system shown in FIG. 12, the main implementation of the Arduino main program is to enable the system to operate normally by calling partial subprograms. The Arduino main program calling subprogram module respectively comprises: the photoelectric chemical sensor comprises a light source control module, a sensor micro-current acquisition module and a data transmission module, and the functions of providing a light source for the photoelectric chemical sensor, acquiring micro-current generated by the sensor and transmitting detected data to a background in a wireless transmission mode are respectively realized. Firstly, the system carries out initialization operation and sets the baud rate of serial port operation to be 115200. And calling a light source control subprogram to control the light source to provide the light source for the photoelectrochemical sensor. Then calling a sensor micro-current detection module to collect the sensor photocurrent. And finally, calling an NB-IOT transmission module to transmit the acquired signals to the background through a BC95 module.

Specifically, the main program design flowchart is shown in fig. 13. The light source is controlled to be turned on and off by driving the relay.

The light source control subroutine flow chart is shown in fig. 14. The light source is controlled to be turned on and off by driving the relay. Firstly, initializing the module, secondly, judging the state of the output level, and then determining whether the bit sensor provides a light source or not by judging the level. The sensor micro-current acquisition program mainly drives hardware to acquire micro-current signals generated by the photoelectrochemical sensor. After the light source control circuit provides a light source for the sensor, firstly, initializing the module, and converting the collected photocurrent into photovoltage through an I-V circuit; secondly, amplifying the photovoltage through an amplifying circuit; then filtering out clutter through a filter circuit, and converting the acquired analog signal into a digital signal through an analog-to-digital conversion circuit; and finally, transmitting the signal to an Arduino controller.

The flow chart of the sensor micro-current acquisition programming is shown in figure 15. The data transmission module subprogram design mainly drives a BC95 module in NB-IoT equipment, so that acquired data are transmitted to an OceanConnect cloud platform through a wireless network BC95 module, and the OceanConnect cloud platform transmits the data to a server side through transparent transmission. Firstly, the BC95 chip transmits and receives data through RX/TX, and the data received by the BC95 is transmitted and received through a telecommunication card in a USIM card slot. The data transmission process of the BC95 is to first power on and initialize the USIM card; secondly, checking whether the network is connected or not, and automatically searching the network; then activating PDN to obtain IP address and establishing PDN connection; then data are received and transmitted; and finally, after no data transmission is carried out for a certain time, entering a PSM state, waiting for the number of the clients again, and entering PDN connection.

The data transfer module programming flow diagram is shown in figure 16. A supervised learning mode is used in machine learning software design, and data are more accurate and stable through learning. Firstly, data are collected through a photoelectrochemical sensor and are subjected to learning training, preprocessing and classifying operation are carried out on the data collected by the sensor through an SVM, then a hyperplane which can accurately divide positive and negative sample points in a linear separable data set into two is found through a sensor model, and finally the process of finding the hyperplane is converted into the process of finding a minimum loss function. And then 5000 pieces of data acquired by the photoelectrochemical sensor are subjected to time series analysis after being preprocessed. The data time sequence forms a numerical value sequence at each time point, a corresponding model is obtained after the time sequence is analyzed and trained, and future values are predicted through the model. The time series analysis is not only a simple regression to time, but also a research on the change rule and trend of the data,

the collected data were subjected to time series analysis in the system using the pandas analysis tool in python. Firstly, stability inspection is carried out, which is the premise of time sequence analysis, then unstable sequences are processed and finally converted into stable sequences, the vibration amplitude of data is reduced by utilizing logarithmic transformation, and the linear rule is more obvious. Then, the average value in a certain time interval is adopted as an estimated value in a certain period by using a moving average method in a smoothing method, the average value is calculated by using a variable weight method in exponential averaging, and the data in the period is weighted, so that the daily period factor can be reduced, but the influence cannot be eliminated. Therefore, the invention utilizes the differential operation to remove the periodically-influenced elements from the time sequence difference, and linearly subtracts the data at equal periodic intervals in the operation. And finally separating the time series data into different components. Time series data were separated into long-term trends, seasonal trends and random components using the X-11 method in statsmodel. And finally, after different decomposition results are obtained, fitting each component through a time sequence model respectively, and obtaining a more accurate result by adopting time sequence fitting. By decomposing time sequence data, the cross influence of the data during modeling is avoided, and the prediction accuracy can be improved.

The main function of the human-computer interaction interface design is to better display the analyzed and processed data through the human-computer interaction module at the PC end, so that a tester can more intuitively, conveniently and quickly know the test result, and a flow chart of a human-computer interaction interface programming program is shown in fig. 17.

In order to verify that the fruit deterioration detection system based on the photoelectrochemical sensor of the present invention can realize high-sensitivity detection of ethanol, the following examples were conducted.

The first embodiment is as follows:

in order to detect the measurement performance of the system, solutions with the ethanol concentrations of 400ppm,600ppm,800ppm,1000ppm and 1500ppm are respectively prepared. The prepared solution was then tested using the assembled fruit spoilage detection system. The response relation of the ethanol concentration and the current is obtained through the oxidation-reduction reaction carried out under the same ethanol concentration. The results of the tests are shown in table 1. Through tests, the correlation between the ethanol concentration and the current is obtained, and a curve graph of the fitted relation is shown in the attached figure 18.

TABLE 1 data table of voltage values measured for ethanol of different concentrations

Ethanol concentration (ppm)	400	600	800	1000	1500
						Current mA	0.491	0.542	0.583	0.534	0.672

As can be seen from table 1 and fig. 18, the correlation equation between ethanol concentration and current response is 0.443 × x + 1.644. The ethanol concentration had a good correlation with the measured current value (R2 ═ 0.965). From Table 1 we can observe that the current value increases significantly with increasing ethanol concentration, indicating that the present system can reflect changes in ethanol concentration by changes in current.

Example two:

firstly, apples purchased from a supermarket are washed and sliced, the apples and a photoelectrochemical sensor are wrapped by a preservative film to form a closed space, the sealed space is placed at room temperature and is respectively placed for different days for detection, the recorded data are shown in table 2, and the data are processed to obtain a histogram of the relationship between the current response value and the days, which is shown in figure 19.

TABLE 2 data sheet of apple days and measured current

When placed inWorkshop (sky)	2	4	6	8	10
						Current (μ A)	45	56	65	76	85

As can be seen from the ethanol sample testing experiment in combination with Table 2 and FIG. 19, as the time of the fruit standing days increases, the current value measured by the sensor also increases with the time. Therefore, the ethanol can be obtained in the fruit spoilage process, and the concentration of the ethanol is increased along with the increase of the spoilage degree of the fruit. The results of this example show that the ethanol sensing system can be used to detect the degree of spoilage of fruit.

Example three:

firstly, a plurality of bananas are purchased in a supermarket, the sensor and the bananas are wrapped by a preservative film to form a closed space, the closed space is placed at room temperature and is respectively placed for different days to detect, the recorded data are shown in a table 3, and the data are processed to obtain a histogram of the relationship between the current response value and the days, as shown in an attached figure 20.

TABLE 3 data table of banana days and measured current

Standing time (sky)	1	2	3	4	5	6
							Current (μ A)	35	38	43	49	55	62

As can be seen from the ethanol sample testing experiment in conjunction with Table 3 and FIG. 20, as the time of the fruit standing days increases, the current value measured by the sensor also increases with the time. Therefore, the ethanol can be obtained in the fruit spoilage process, and the concentration of the ethanol is increased along with the increase of the spoilage degree of the fruit. The rot process of bananas can be obviously seen by placing on different days, and the detection of the ethanol sensing system can show that the content of ethanol is obviously increased, and the result of the embodiment further shows that the ethanol sensing system can be used for detecting the rot degree of fruits.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. Fruit detecting system that deteriorates, its characterized in that: the system comprises a microcontroller module, a light source control module, a photoelectrochemistry sensor module, a data transmission module, a background server module, a data calibration module, a man-machine interaction module and a power supply module;

the data transmission module realizes wireless data transmission;

the power supply module supplies power to the whole system;

2. The fruit spoilage detection system of claim 1, wherein: the peripheral circuit of the microcontroller module comprises a light source control circuit, a sensor weak current detection circuit, a data transmission circuit and a power supply circuit; the micro-controller module controls the light source control module to provide a light source for the photoelectrochemistry sensor module through the light source control circuit, the sensor weak current detection circuit collects current signals sent by the photoelectrochemistry sensor module, converts the current signals into digital signals and transmits the digital signals to the controller, then data are transmitted to the data transmission module through the data transmission circuit, and the power circuit provides a power supply for the micro-controller module.

3. The fruit spoilage detection system of claim 2, wherein: the sensor weak current detection circuit comprises an I-V conversion circuit, an amplifying circuit, a sensor weak current detection filter circuit and an A/D conversion circuit; the collected current signals are converted into photoelectric voltage through the I-V conversion circuit, the photoelectric voltage is amplified through the amplifying circuit, then the amplified photoelectric voltage is filtered to remove noise waves through the filter circuit, and finally the collected signals are converted into digital signals through the A/D conversion circuit.

4. The fruit spoilage detection system of claim 1, wherein: the working electrode of the photoelectrochemical sensor used by the photoelectrochemical sensor module is a Pd-ZnO/Ni electrode.

5. A method of constructing a fruit spoilage detection system as claimed in any one of claims 1 to 4, comprising the steps of:

s2: testing the performance of the photoelectrochemical sensor;

s3: detecting the design of a system hardware circuit;

s4: and (5) detecting system software programming.

6. The method for constructing a fruit deterioration detecting system according to claim 5, wherein the specific operation of step S1 includes:

s11: cutting the foam nickel plate into 1cm³Ultrasonically cleaning and drying the foam nickel sheets with the sizes;

s12: ultrasonically cleaning and drying the ITO conductive glass;

7. The method of constructing a fruit spoilage detection system of claim 5, wherein: the performance test of the photoelectrochemical sensor in the step S2 comprises a physical characterization test, an electrochemical test and a test of sensitivity, selectivity and stability; the physical characterization test comprises a scanning electron microscope, an energy dispersion X-ray spectrum, X-ray diffraction and an X-ray photoelectron spectrum test; the electrochemical test comprises the steps of exploring the change relation between the photocurrent and the ethanol concentration by a chronoamperometry method and exploring the change relation between the impedance and the ethanol concentration by an alternating current impedance method.

8. The method of constructing a fruit spoilage detection system of claim 5, wherein: the system hardware circuit in step S3 includes a microcontroller core circuit and a microcontroller peripheral circuit, where the microcontroller core circuit includes a microcontroller chip, a crystal oscillator circuit, a microcontroller chip filter circuit, and a reset circuit.

9. The method of constructing a fruit spoilage detection system of claim 5, wherein: the system software program in the step S4 comprises a main program, a light source control subprogram, a sensor micro-current acquisition signal subprogram, a data transmission module subprogram, a machine learning program and a man-machine interaction interface program; the main program is arranged in the microcontroller module, the light source control subprogram is arranged in the light source control module, the sensor micro-current acquisition signal subprogram is arranged in the photoelectrochemical sensor module, the data transmission module subprogram is arranged in the data transmission module, the machine learning program and the human-computer interaction interface program are arranged in the data calibration module, and the human-computer interaction interface program is arranged in the human-computer interaction module.

10. A method of testing a fruit spoilage detection system according to any of claims 1 to 4, 6 to 9, comprising the steps of: