Volatile organic compound monitoring system and method based on photo-thermal modulation enhancement

Abstract

The invention discloses a volatile organic compound monitoring system and method based on photo-thermal modulation enhancement, and relates to the technical field of air quality detection. An MEMS gas sensor is used for detecting volatile organic compounds; the ultraviolet LED lamp is mounted right above the MEMS gas sensor, a gap is formed between the ultraviolet LED lamp and the MEMS gas sensor, and the ultraviolet LED lamp is used for generating ultraviolet light and irradiating the MEMS gas sensor by utilizing the ultraviolet light; the processor is used for adjusting the working temperature of the MEMS gas sensor, turning on the ultraviolet LED lamp when the MEMS gas sensor is in a detection state, turning off the ultraviolet LED lamp when the MEMS gas sensor is in a non-detection state, and adjusting the light source intensity of the ultraviolet LED lamp. The volume can be further reduced, and the response performance and the energy consumption can be optimized.

Description

Technical Field

[0001] The present application relates to the technical field of air quality detection, and in particular to a volatile organic compound monitoring system and method based on photothermal modulation enhancement. Background Art

[0002] In modern society, the detection of volatile organic compounds (VOCs) plays a vital role in air pollution, environmental protection, food safety, medical health and other fields, and has therefore become a mainstream concern. In recent years, low-energy (also known as power consumption) and small-size intelligent monitoring systems that combine various sensors have gained increasingly important applications in VOCs detection. However, the energy consumption and size of these intelligent monitoring systems are mainly limited by the large size and high-temperature working characteristics of traditional metal oxide semiconductor (MOS) gas sensors.

[0003] MOS gas sensors have been widely studied for their excellent performance, simple manufacturing and low cost. They can be used to detect various harmful gases. ZnO nanomaterials are typical n-type semiconductor metal oxides with a wide band gap of 3.4 eV. They have been shown to be an effective VOCs detection sensing material due to their high electron mobility and chemical stability. However, MOS gas sensors usually require higher operating temperatures to achieve optimal performance, which leads to increased energy consumption. The operating temperature has a great influence on the performance of MOS gas sensors. Lowering the operating temperature can not only reduce energy consumption, but also improve material stability and prevent the risk of flammable gas explosion caused by high temperature. The operating temperature can be reduced by changing material properties, adopting micro-electro-mechanical system (MEMS) manufacturing technology and using ultraviolet (UV) assisted irradiation. Among these methods, UV assisted irradiation technology can improve the response and recovery of MOS gas sensors at lower temperatures, thereby achieving a balance between energy consumption and detection performance. When metal oxides are irradiated by short-wavelength ultraviolet light, electron-hole pairs are generated. These electron-hole pairs act as carriers, activate adsorbed oxygen, and promote the redox reaction of the target gas.

[0004] Currently, Yi et al. synthesized hollow ZnO microspheres using a carbon template-assisted method and used a low-power UV LED (Light Emitting Diode) (2mW) to respond quickly to ethanol at temperatures below 150°C. Ting et al. proposed a MEMS-based gas sensor integrated with a blue LED for NO detection. Although they focused on low energy consumption and improved sensor performance, the miniaturization and real-time detection aspects of the sensor have not been thoroughly studied. Summary of the invention

[0005] The purpose of this application is to provide a volatile organic compound monitoring system and method based on photothermal modulation enhancement, which can further reduce the volume and optimize the response performance and energy consumption.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a volatile organic compound monitoring system based on photothermal modulation enhancement, the volatile organic compound monitoring system based on photothermal modulation enhancement comprising:

[0008] MEMS gas sensors are used to detect volatile organic compounds; MEMS gas sensors are metal oxide semiconductor gas sensors;

[0009] An ultraviolet LED lamp is installed directly above the MEMS gas sensor with a gap between the lamp and the MEMS gas sensor, and is used to generate ultraviolet light and illuminate the MEMS gas sensor with the ultraviolet light;

[0010] The processor is connected to the MEMS gas sensor and the ultraviolet LED lamp respectively, and is used to adjust the working temperature of the MEMS gas sensor, turn on the ultraviolet LED lamp when the MEMS gas sensor is in a detection state, turn off the ultraviolet LED lamp when the MEMS gas sensor is in a non-detection state, and adjust the light source intensity of the ultraviolet LED lamp.

[0011] Optionally, the MEMS gas sensor comprises: a ZnO nanoplate and a heating plate, the ZnO nanoplate is mounted on the heating plate; the ZnO nanoplate is used to detect volatile organic compounds; the heating plate is used to heat the ZnO nanoplate;

[0012] The processor is connected to the ZnO nanoplate and the heating plate respectively; the processor is used to receive the detection data of the ZnO nanoplate and adjust the output power of the heating plate to adjust the working temperature of the MEMS gas sensor.

[0013] Optionally, the ZnO nanoplate is prepared by a hydrothermal synthesis method or a magnetron sputtering method.

[0014] Optionally, the MEMS gas sensor further comprises: a Wheatstone bridge; the Wheatstone bridge is connected to the ZnO nanoplate; the Wheatstone bridge is used to measure the resistance of the ZnO nanoplate;

[0015] The processor is connected to the Wheatstone bridge; the processor is used to determine whether the resistance change value is greater than a preset change value. If so, it is determined that the MEMS gas sensor is in a detection state; if not, it is determined that the MEMS gas sensor is in a non-detection state; wherein the resistance change value is the difference between the resistance at the current moment and the resistance at the previous moment.

[0016] Optionally, the volatile organic compound monitoring system based on photothermal modulation enhancement further includes: a first low-pass filter, a first emitter follower, a second low-pass filter and a second emitter follower;

[0017] The processor is used to generate a first PWM signal and a second PWM signal; the first PWM signal is used to adjust the output power of the heating plate; the second PWM signal is used to adjust the output power of the ultraviolet LED lamp to adjust the light source intensity of the ultraviolet LED lamp;

[0018] The first low-pass filter and the second low-pass filter are respectively connected to the processor; the first low-pass filter is used to filter the first PWM signal to obtain a first DC voltage; the second low-pass filter is used to filter the second PWM signal to obtain a second DC voltage;

[0019] The first emitter follower is connected to the first low-pass filter and the heating plate respectively; the first emitter follower is used to amplify the first DC voltage to obtain a first amplified voltage, and use the first amplified voltage to drive the heating plate to work;

[0020] The second emitter follower is connected to the second low-pass filter and the ultraviolet LED lamp respectively; the second emitter follower is used to amplify the second DC voltage to obtain a second amplified voltage, and use the second amplified voltage to drive the ultraviolet LED lamp to work.

[0021] Optionally, there are multiple MEMS gas sensors and multiple ultraviolet LED lamps, and the MEMS gas sensors correspond to the ultraviolet LED lamps one by one.

[0022] Optionally, the volatile organic compound monitoring system based on photothermal modulation enhancement also includes: a USB-C interface and a Bluetooth module; the USB-C interface and the Bluetooth module are both connected to the processor; the USB-C interface is used to realize wired communication between the processor and external devices; the Bluetooth module is used to realize wireless communication between the processor and external devices.

[0023] Optionally, the volatile organic compound monitoring system based on photothermal modulation enhancement further includes: a temperature and humidity sensor, an LED indicator light, a buzzer and a DIP switch; the temperature and humidity sensor, the LED indicator light, the buzzer and the DIP switch are all connected to the processor;

[0024] The temperature and humidity sensor is used to measure the ambient temperature and humidity;

[0025] The LED indicator light is used to indicate the working status of the volatile organic compound monitoring system based on photothermal modulation enhancement;

[0026] The buzzer is used for alarm;

[0027] The DIP switch is used to set the working state of the volatile organic compound monitoring system based on photothermal modulation enhancement.

[0028] Optionally, the volatile organic compound monitoring system based on photothermal modulation enhancement further includes: a battery, a power management unit and a plug terminal;

[0029] The USB-C port and plug-in terminal are used to power the battery, MEMS gas sensor, UV LED lamp and processor through the power management unit;

[0030] The battery is used to power the MEMS gas sensor, UV LED light, and processor via a power management unit.

[0031] In a second aspect, the present application provides a volatile organic compound monitoring method based on photothermal modulation enhancement, which is applied to any one of the volatile organic compound monitoring systems based on photothermal modulation enhancement described above, and the volatile organic compound monitoring method based on photothermal modulation enhancement includes:

[0032] Adjust the operating temperature of the MEMS gas sensor so that the MEMS gas sensor operates at a preset operating temperature;

[0033] Determine whether the MEMS gas sensor is in the detection state;

[0034] If so, turn on the ultraviolet LED lamp and adjust the light source intensity of the ultraviolet LED lamp so that the ultraviolet LED lamp irradiates the MEMS gas sensor with a preset light source intensity, and receive detection data of the MEMS gas sensor until the MEMS gas sensor is in a non-detection state. At this time, turn off the ultraviolet LED lamp.

[0035] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0036] The present application provides a volatile organic compound monitoring system and method based on photothermal modulation enhancement, including: a MEMS gas sensor, an ultraviolet LED lamp and a processor, wherein the ultraviolet LED lamp is installed directly above the MEMS gas sensor, and there is a gap between the ultraviolet LED lamp and the MEMS gas sensor, so that the MEMS gas sensor and the ultraviolet LED lamp can be integrated together to reduce the volume. The processor can adjust the operating temperature of the MEMS gas sensor, turn on the ultraviolet LED lamp when the MEMS gas sensor is in a detection state, turn off the ultraviolet LED lamp when the MEMS gas sensor is in a non-detection state, and adjust the light source intensity of the ultraviolet LED lamp, so that the operating temperature and light source intensity can be adjusted at the same time, and the response performance and energy consumption can be optimized based on photothermal modulation enhancement. The present application can further reduce the volume, optimize the response performance and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 A schematic diagram of the structure of a volatile organic compound monitoring system based on photothermal modulation enhancement provided in Example 1 of the present application.

[0039] Figure 2 The preparation process, structure and performance diagram of the ZnO nanoplate provided in Example 1 of the present application; wherein, Figure 2 (a) is the preparation process of ZnO nanoplates; Figure 2 (b) is a MEMS gas sensor structure based on ZnO nanoplate and an SEM image of the ZnO nanoplate; Figure 2 (c) is the TEM image of ZnO nanoplate; Figure 2 (d) in the figure is the XRD pattern of ZnO nanoplate; Figure 2 (e) is the XPS panoramic spectrum of ZnO nanoplate; Figure 2 (f) in the figure is the high-resolution spectrum of Zn 2p of ZnO nanoplates; Figure 2 (g) in the figure is the high-resolution spectrum of O1s of ZnO nanoplates.

[0040] Figure 3 A physical photo and PCB layout schematic diagram of a volatile organic compound monitoring system based on photothermal modulation enhancement provided in Example 1 of the present application; wherein, Figure 3 (a) is a real photo; Figure 3(b) is the PCB front layout; Figure 3 (c) in the figure is the layout on the back side of the PCB.

[0041] Figure 4 A schematic diagram of the application display interface provided in Example 1 of the present application.

[0042] Figure 5 This is a schematic diagram of the resistance and dynamic response of the MEMS gas sensor provided in Example 1 of the present application; wherein, Figure 5 (a) is the resistance of S1 and S2 in air when they work at different operating temperatures; Figure 5 (b) shows the dynamic response of S1 and S2 when exposed to 10-100 ppm ethanol; Figure 5 (c) shows the dynamic response of S1 and S2 when exposed to 10-100 ppm acetone.

[0043] Figure 6 A schematic diagram showing the dynamic response comparison of the MEMS gas sensor provided in Example 1 of the present application when exposed to 1-100 ppm ethanol at 200°C and 100°C with UV irradiation of different powers and without UV irradiation; wherein, Figure 6 (a) is a comparison of the dynamic responses of S1 when exposed to 1-100 ppm ethanol at 200°C, 1.5 mW UV irradiation and 200°C, no UV irradiation; Figure 6 (b) shows the dynamic response comparison of S1 when exposed to 1-100 ppm ethanol at 200°C, 3 mW UV irradiation and 200°C, without UV irradiation; Figure 6 (c) is a comparison of the dynamic responses of S1 when exposed to 1-100 ppm ethanol at 200°C, 8 mW UV irradiation and 200°C without UV irradiation; Figure 6 (d) is a comparison of the dynamic responses of S1 when exposed to 1-100 ppm ethanol at 100°C, 1.5 mW UV irradiation and 100°C, no UV irradiation; Figure 6 (e) is a comparison of the dynamic responses of S1 when exposed to 1-100 ppm ethanol at 100°C, 3 mW UV irradiation and 100°C, without UV irradiation; Figure 6 (f) in the figure is a comparison of the dynamic responses of S1 when exposed to 1-100 ppm ethanol at 100°C under 8 mW UV light irradiation and at 100°C without UV light irradiation.

[0044] Figure 7 This is a schematic diagram of the response mechanism of ZnO nanosheets to ethanol provided in Example 1 of the present application; wherein, Figure 7 (a) is the response mechanism to ethanol without UV irradiation; Figure 7 (b) in the figure shows the response mechanism to ethanol when exposed to ultraviolet light.

[0045] Figure 8 A schematic flow chart of a volatile organic compound monitoring method based on photothermal modulation enhancement provided in Example 2 of the present application. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] Example 1

[0048] This embodiment provides a volatile organic compound monitoring system based on photothermal modulation enhancement, such as Figure 1 As shown, the volatile organic compound monitoring system based on photothermal modulation enhancement includes:

[0049] MEMS gas sensor is used to detect volatile organic compounds. MEMS gas sensor is a metal oxide semiconductor gas sensor.

[0050] The ultraviolet LED lamp is installed directly above the MEMS gas sensor with a gap between the lamp and the MEMS gas sensor, and is used to generate ultraviolet light and use the ultraviolet light to irradiate the MEMS gas sensor.

[0051] The processor is connected to the MEMS gas sensor and the ultraviolet LED lamp respectively, and is used to adjust the working temperature of the MEMS gas sensor, turn on the ultraviolet LED lamp when the MEMS gas sensor is in a detection state, turn off the ultraviolet LED lamp when the MEMS gas sensor is in a non-detection state, and adjust the light source intensity of the ultraviolet LED lamp.

[0052] With the increasing demand for air quality detection, there is an urgent need to improve the detection performance of volatile organic compounds. Based on this, this embodiment develops a high-performance, low-energy volatile organic compound monitoring system based on photothermal modulation enhancement. The monitoring system integrates a MEMS gas sensor and a miniature ultraviolet LED lamp, and can adjust the working temperature and light source intensity. The combination of the working temperature and the light source intensity co-modulation can significantly improve the response performance of the MEMS gas sensor, while reducing the working temperature (from 300°C to 100°C) and energy consumption (less than 1 / 6 of the original) of the MEMS gas sensor, and proposes a new method for building a high-performance, low-energy volatile organic compound monitoring system.

[0053] In this embodiment, a mounting bracket is provided around the MEMS gas sensor, and the mounting bracket is used to install the ultraviolet LED lamp, so that the ultraviolet LED lamp is installed directly above the MEMS gas sensor, and there is a gap between the ultraviolet LED lamp and the MEMS gas sensor, thereby designing a portable VOCs monitoring system based on MEMS gas sensor thermal modulation and ultraviolet LED light modulation enhancement. By adjusting the working temperature and light source intensity, the response performance and energy consumption can be optimized. At the same time, the MEMS gas sensor and the ultraviolet LED lamp are integrated to reduce the volume, thereby enhancing the response performance of the MEMS gas sensor at low temperatures, and realizing the development of a miniaturized, high-performance VOCs monitoring system.

[0054] In this embodiment, the MEMS gas sensor includes: a ZnO nanoplate and a heating plate, the ZnO nanoplate is mounted on the heating plate, the ZnO nanoplate is used as a ZnO sensing material for detecting volatile organic compounds, and the heating plate is used to heat the ZnO nanoplate. The processor is connected to the ZnO nanoplate and the heating plate respectively, and the processor is used to receive the detection data of the ZnO nanoplate and adjust the output power of the heating plate to adjust the operating temperature of the MEMS gas sensor.

[0055] Wherein, the ZnO nanoplate is prepared by a hydrothermal synthesis method or a magnetron sputtering method.

[0056] Here, the hydrothermal synthesis method is introduced: Figure 2 As shown in (a), first, 0.50 mmol NH 4 F (ammonium fluoride), 1.25mmol urea and 1.75mmol glucose were added to 35mL deionized (DI) water and stirred to make a uniform mixture. Then, 3mmol Zn(CH 3 COO 2 ·2H 2 O (zinc acetate dihydrate) was added to the above mixture, and the resulting final mixture was transferred to a hydrothermal reactor and kept at 200°C for 10 hours. After the reaction was completed, the reaction product was washed alternately with deionized water and ethanol. Subsequently, the precipitate obtained after washing was dried at 60°C for 12 hours to obtain a precursor. Finally, the obtained precursor was annealed in air at 450°C for 2 hours at a heating rate of 1°C / min to obtain ZnO nanosheets. Figure 2 As shown in (b), the prepared ZnO nanosheets are uniformly deposited on the heating plate of the MEMS device. The ZnO nanosheets are in the form of thin films, and the well-defined pores are evenly distributed throughout the nanosheets, which can also be seen from Figure 2 (b) SEM (Scanning Electronic Microscopy) image and Figure 2 The XRD (X-Ray Diffraction) spectrum of ZnO nanosheets is shown in the TEM (Transmission Electron Microscope) image (c). Figure 2 As shown in (d), according to JCPDS No.36-1451 (standard card of hexagonal wurtzite zinc oxide), the sharp XRD peaks indicate that the ZnO nanosheets are well crystallized during high-temperature calcination. The surface composition and chemical state of the ZnO nanosheets were further studied by XPS (X-ray Photoelectron Spectroscopy). Figure 2 The full spectrum analysis in (e) shows that the ZnO nanosheets contain Zn, O and C elements, and no impurity peaks are observed, such as Figure 2 As shown in (f), the Zn 2p orbital shows two different peaks at 1021.5eV and 1044.5eV, representing the Zn 2+ Zn 2p 3 / 2 and Zn 2p 1 / 2 .like Figure 2 As shown in (g), the O1s high-resolution spectrum of ZnO can be divided into two peaks at 530.25 eV and 531.22 eV, corresponding to the lattice oxygen (O L ) and oxygen vacancies (O V ).

[0057] By combining ZnO nanomaterials with MEMS technology, the volume of MEMS gas sensors can be reduced.

[0058] In this embodiment, the output power of the heating plate and the output power of the ultraviolet LED lamp are controlled by the processor to complete the adjustment of the working temperature and the intensity of the light source. The output power of the heating plate and the output power of the ultraviolet LED lamp are controlled by the PWM signal emitted by the processor. The PWM signal is converted into a DC voltage through a low-pass filter, and is amplified by an emitter follower and sent to the heating plate and the ultraviolet LED lamp.

[0059] Based on this, the volatile organic compound monitoring system based on photothermal modulation enhancement in this embodiment further includes: a first low-pass filter, a first emitter follower, a second low-pass filter and a second emitter follower.

[0060] The processor is used to generate a first PWM signal and a second PWM signal, the first PWM signal is used to adjust the output power of the heating plate, and the second PWM signal is used to adjust the output power of the ultraviolet LED lamp to adjust the light source intensity of the ultraviolet LED lamp.

[0061] The first low-pass filter and the second low-pass filter are connected to the processor respectively. The first low-pass filter is used to filter the first PWM signal to obtain a first DC voltage. The second low-pass filter is used to filter the second PWM signal to obtain a second DC voltage.

[0062] The first emitter follower is connected to the first low-pass filter and the heating plate respectively. The first emitter follower is used to amplify the first DC voltage to obtain a first amplified voltage, and use the first amplified voltage to drive the heating plate to work, so that the heating plate works with the output power corresponding to the first PWM signal.

[0063] The second emitter follower is connected to the second low-pass filter and the ultraviolet LED lamp respectively. The second emitter follower is used to amplify the second DC voltage to obtain a second amplified voltage, and use the second amplified voltage to drive the ultraviolet LED lamp to work, so that the ultraviolet LED lamp works at the output power corresponding to the second PWM signal.

[0064] In this embodiment, the MEMS gas sensor further includes: a Wheatstone bridge connected to the ZnO nanoplate, and the Wheatstone bridge is used to measure the resistance of the ZnO nanoplate.

[0065] The processor is connected to the Wheatstone bridge, and the processor is used to determine whether the resistance change value is greater than a preset change value. If so, it is determined that the MEMS gas sensor is in a detection state. If not, it is determined that the MEMS gas sensor is in a non-detection state, wherein the resistance change value is the difference between the resistance at the current moment and the resistance at the previous moment.

[0066] The front-end circuit of the MEMS gas sensor of this embodiment adopts a Wheatstone bridge configuration. The differential output of the Wheatstone bridge is directly input to the ADS1115 analog-to-digital converter, and then input to the processor through the ADS1115 analog-to-digital converter. The internal programmable gain amplifier of the ADS1115 analog-to-digital converter expands the measurement range and improves the sensor performance.

[0067] This embodiment adopts a unique working mode, placing the ultraviolet LED lamp directly above the MEMS gas sensor, and realizing intelligent energy consumption management and gas detection performance optimization through software and hardware linkage. The specific process is as follows:

[0068] (1) Low energy consumption design: In the initial state of the monitoring system, the UV LED light is turned off and the MEMS gas sensor operates at a lower operating temperature. The purpose of this design is to maintain the low energy consumption of the entire monitoring system, because turning on the UV LED light and letting the MEMS gas sensor operate at high temperature will significantly increase energy consumption. By reducing the operating temperature of the MEMS gas sensor to about 100°C, the energy consumption is reduced to one-sixth of the original compared to the traditional 300°C.

[0069] (2) Intelligent monitoring and UV enhancement: The monitoring system uses software to monitor the resistance change value of the MEMS gas sensor in real time and continuously maintains efficient monitoring of the surrounding environment. When the resistance change value of the MEMS gas sensor is detected to exceed the set threshold (i.e., the preset change value), the monitoring system determines that there may be target gas or environmental disturbance. At this time, the ultraviolet LED light will be automatically turned on to enhance the performance of the MEMS gas sensor. The irradiation of ultraviolet light will further stimulate the response of the MEMS gas sensor and improve its sensitivity and detection accuracy. During the ultraviolet light irradiation process, ultraviolet photons enhance the oxygen anion (O) by exciting the electron-hole pairs of the ZnO sensing material. 2- ) is generated, promoting the reaction between the target gas and oxygen molecules, thereby greatly improving the response speed and sensitivity of the MEMS gas sensor to gas.

[0070] (3) Recovery mode: After the detection phase, the MEMS gas sensor enters the recovery process. The monitoring system automatically turns off the UV LED light and waits for the resistance value of the MEMS gas sensor to return to the baseline level. This stable recovery of the baseline is designed to prevent the MEMS gas sensor from working in a high-energy consumption mode for a long time, effectively reducing the overall energy consumption of the monitoring system and extending the working life of the MEMS gas sensor.

[0071] By lowering the operating temperature and enabling ultraviolet light when necessary, the monitoring system can balance the needs of high-performance gas detection and low-energy operation, ensuring wide applicability in different application scenarios. Through this intelligent software-hardware linkage and energy management strategy, the monitoring system can not only effectively reduce energy consumption, but also extend the service life of the monitoring system while ensuring detection accuracy, significantly improving the overall performance and stability of volatile organic compound monitoring.

[0072] In this embodiment, there are multiple MEMS gas sensors and ultraviolet LED lamps, and the MEMS gas sensors correspond to the ultraviolet LED lamps one-to-one, that is, the number of MEMS gas sensors and ultraviolet LED lamps is the same, one MEMS gas sensor corresponds to one ultraviolet LED lamp, and the ultraviolet LED lamp is used to irradiate the corresponding MEMS gas sensor.

[0073] The volatile organic compound monitoring system based on photothermal modulation enhancement of this embodiment also includes: a USB-C interface and a Bluetooth module, both of which are connected to the processor, the USB-C interface is used to realize wired communication between the processor and external devices, and the Bluetooth module is used to realize wireless communication between the processor and external devices.

[0074] The processor can use a 32-bit ARM Cortex-M4 MCU, specifically a single-chip microcomputer STM32L431CB, to achieve low energy consumption. The USB-C interface communicates with the processor through the CH340 chip, which is a USB bus adapter chip to achieve wired communication between the processor and an external PC (Personal Computer). The Bluetooth module can use a BLE (Bluetooth Low Energy) 4.0 module, which supports wireless communication with mobile phones and achieves wireless communication between the processor and external mobile phones.

[0075] The volatile organic compound monitoring system based on photothermal modulation enhancement of this embodiment also includes: a battery, a power management unit and a plug terminal, and the plug terminal can adopt XH2.54. Both the USB-C interface and the plug terminal have the function of providing power. The USB-C interface and the plug terminal are used to power the battery, MEMS gas sensor, ultraviolet LED lamp and processor through the power management unit. Of course, they can also power other components of the monitoring system. When there is no external power supply, the battery is used to power the MEMS gas sensor, ultraviolet LED lamp and processor through the power management unit. Of course, it can also power other components of the monitoring system.

[0076] Among them, the battery can be a lithium battery, and the power management unit is responsible for handling the charging of the lithium battery and the voltage regulation of 5V and 3.3V, and can provide power for components with different needs.

[0077] The volatile organic compound monitoring system based on photothermal modulation enhancement of this embodiment also includes: a temperature and humidity sensor, an LED indicator light, a buzzer and a DIP switch, and the temperature and humidity sensor, the LED indicator light, the buzzer and the DIP switch are all connected to the processor.

[0078] The temperature and humidity sensor may adopt the SHT20 sensor to measure the ambient temperature and humidity.

[0079] The LED indicator light is used to indicate the working status of the volatile organic compound monitoring system based on photothermal modulation enhancement. It can be set according to user needs. For example, setting the LED indicator light to be long indicates that the monitoring system is in normal working condition, setting the LED indicator light to flash indicates that the MEMS gas sensor is in detection state, and setting the LED indicator light to be red indicates that the monitoring system fails.

[0080] The buzzer is used for alarm, specifically, it can be used for alarm when the monitoring system fails.

[0081] The DIP switch is used to set the working state of the volatile organic compound monitoring system based on photothermal modulation enhancement. It can be set according to user needs. For example, the UV LED lamp can be turned on or off by manipulating the DIP switch, the working temperature of the MEMS gas sensor can be controlled, and the light source intensity of the UV LED lamp can be controlled.

[0082] like Figure 3 As shown, this embodiment designs and implements a compact VOCs monitoring system, which has a size of 55 mm long and 35 mm wide. Figure 3 As shown in (a) of Figure 1, the PCB layout is designed using Cadence software. Figure 3 As shown in (b) and (c) in the figure, the monitoring system has a USB-C interface, a power switch and a debugging port (for debugging the monitoring system) on the side for easy access. The PCB board includes two MEMS gas sensors and two UV LED lights, which are designed for low energy consumption and versatility. In order to save space, the Bluetooth module is located at the bottom of the PCB board. The Bluetooth module can realize wireless communication with the mobile phone, thereby collecting data in real time under multifunctional conditions.

[0083] This embodiment also designs a user-friendly Android application for the monitoring system, such as Figure 4 As shown, the application is a mobile phone application that communicates with the monitoring system through the standard JSON protocol and displays real-time data records on up to 8 channels. It can continuously monitor the status of the monitoring system, such as temperature, humidity and battery life. The application includes a GUI (Graphical User Interface) for power control, data storage and system settings. Its universal protocol parsing and customizable interface ensure its versatility.

[0084] The following is a performance verification of the monitoring system of this embodiment:

[0085] In this embodiment, two MEMS gas sensors based on ZnO nanoplates are prepared. The ZnO nanoplates are prepared by hydrothermal synthesis and magnetron sputtering, respectively. The MEMS gas sensor using the ZnO nanoplates synthesized by hydrothermal synthesis is marked as S1, and the MEMS gas sensor using the ZnO nanoplates sputtered by magnetron sputtering is marked as S2. The gas-sensing properties of the monitoring system with S1 and S2 are tested on the test platform. The resistance changes of S1 and S2 in the air when working at different working temperatures of 100℃-300℃-100℃ are observed, as shown in FIG. Figure 5 As shown in (a) in Figure 1, precise temperature control of the heating plate and a wide range of resistance readings can be achieved. At an operating temperature of 300°C, the dynamic response curves exposed to 10-100 ppm ethanol and acetone are shown in Figure 1. Figure 5 (b) and Figure 5 As shown in (c), the prepared MEMS gas sensor demonstrates excellent sensing performance, showing selectivity for different gas types and a large concentration sensing range.

[0086] Figure 6 The dynamic response comparison curves of S1 exposed to 1-100ppm ethanol under different temperatures and different powers of UV light irradiation (marked as S1-UV) and without UV light irradiation (marked as S1) are shown. The performance changes are observed by adjusting the UV light power. The UV light wavelength is 405nm and the power adjustment range is 0-10mW. Figure 6 (a)-(c) show the dynamic response comparison of S1 at 200°C when irradiated with 1.5mW, 3mW and 8mW UV light and without UV light. Figure 6 (d)-(f) in Figure 1 show the dynamic response comparison when the temperature is reduced to 100℃ and other conditions remain unchanged. The ethanol concentration is set to 1ppm, 10ppm, 50ppm and 100ppm. It is obvious that UV light with different power levels effectively enhances the response and recovery of MEMS gas sensors using ZnO nanomaterials. At 200℃, S1-UV not only improves the response performance of S1 by 10-25 times, but also solves the serious problem of baseline drift at low temperatures. Even at 100℃, although the unilluminated S1 no longer responds, S1-UV still shows excellent performance. At 300℃, the power required for gas sensitivity testing without illumination is 60mW, however, at 100℃, the required power is less than 10mW, which is much lower than the 60mW required for operation at 300℃, and the average energy consumption is reduced to 1 / 6 of the original. This fully demonstrates that by using UV light, ZnO-MEMS gas sensors can achieve higher performance at lower operating temperatures, effectively solving the energy consumption problem, while maintaining or even improving sensitivity and response characteristics.

[0087] Figure 7 A schematic diagram showing the response mechanism of ZnO nanosheets without or with UV irradiation. Figure 7 As shown in (a), the conventional anion adsorption model for measurements under light-free conditions shows that when the sensor is exposed to air, oxygen molecules are adsorbed onto the ZnO surface and capture electrons from the conduction band of ZnO to form oxygen anions (mainly O 2- ). When exposed to the target gas (ethanol), it reacts with O 2- reaction, releasing the trapped electrons back into the conduction band and reducing the resistance of the sensor. When UV illumination is introduced, e.g. Figure 7As shown in (b), UV light enhances electronic excitation, a process that provides photons with enough energy to excite electrons from the valence band to the conduction band of ZnO, thereby generating electron-hole pairs, which increases the number of free electrons in the conduction band, even at lower temperatures. The additional electrons generated by UV light irradiation increase the formation of oxygen anions on the ZnO surface, which enhances the depletion layer and makes the sensor more sensitive to atmospheric changes. In addition, UV light helps stabilize the baseline drift of the sensor by continuously generating electron-hole pairs, maintaining a consistent number of charge carriers, and stabilizing the depletion layer.

[0088] This embodiment designs and verifies a high-performance, low-energy and miniature VOCs monitoring system for VOCs monitoring. The monitoring system includes a MEMS gas sensor and an ultraviolet LED lamp, which can adjust the working temperature and light source intensity. The Bluetooth module can realize wireless communication with the mobile phone, thereby collecting data in real time under multifunctional conditions. Specifically, it can establish a wireless connection with the mobile phone through the BLE 4.0 module to realize power control of heat and ultraviolet light, as well as real-time data collection. The MEMS gas sensor based on ZnO nanomaterials can be significantly improved by ultraviolet light irradiation, while reducing the working temperature (from 300℃ to 100℃) and energy consumption (less than 1 / 6 of the original), and a practical and portable VOCs monitoring system is developed. The monitoring system uses MEMS gas sensors and light / heat modulation, highlighting the potential applications of multiple scenarios in the future. The combination of working temperature and ultraviolet light co-modulation can significantly improve the response performance of the sensor, while reducing the working temperature (from 300℃ to 100℃) and energy consumption (less than 1 / 6 of the original).

[0089] Example 2

[0090] This embodiment provides a volatile organic compound monitoring method based on photothermal modulation enhancement, which is applied to the volatile organic compound monitoring system based on photothermal modulation enhancement described in Example 1. Figure 8 As shown, the volatile organic compound monitoring method based on photothermal modulation enhancement includes:

[0091] T1: Adjust the operating temperature of the MEMS gas sensor so that the MEMS gas sensor operates at a preset operating temperature.

[0092] T2: Determine whether the MEMS gas sensor is in the detection state.

[0093] T3: If yes, turn on the UV LED lamp and adjust the light source intensity of the UV LED lamp so that the UV LED lamp irradiates the MEMS gas sensor with a preset light source intensity, and receive the detection data of the MEMS gas sensor until the MEMS gas sensor is in a non-detection state. At this time, turn off the UV LED lamp.

[0094] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A volatile organic compound monitoring system based on photothermal modulation enhancement, characterized in that: The volatile organic compound monitoring system based on photothermal modulation enhancement includes: MEMS gas sensors are used to detect volatile organic compounds; MEMS gas sensors are metal oxide semiconductor gas sensors; An ultraviolet LED lamp is installed directly above the MEMS gas sensor with a gap between the lamp and the MEMS gas sensor, and is used to generate ultraviolet light and illuminate the MEMS gas sensor with the ultraviolet light; The processor is connected to the MEMS gas sensor and the ultraviolet LED lamp respectively, and is used to adjust the working temperature of the MEMS gas sensor, turn on the ultraviolet LED lamp when the MEMS gas sensor is in a detection state, turn off the ultraviolet LED lamp when the MEMS gas sensor is in a non-detection state, and adjust the light source intensity of the ultraviolet LED lamp.

2. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 1, characterized in that: The MEMS gas sensor includes: a ZnO nanoplate and a heating plate, wherein the ZnO nanoplate is mounted on the heating plate; the ZnO nanoplate is used to detect volatile organic compounds; and the heating plate is used to heat the ZnO nanoplate; The processor is connected to the ZnO nanoplate and the heating plate respectively; the processor is used to receive the detection data of the ZnO nanoplate and adjust the output power of the heating plate to adjust the working temperature of the MEMS gas sensor.

3. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 2, characterized in that: The ZnO nanoplates are prepared by hydrothermal synthesis or magnetron sputtering.

4. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 2, characterized in that: The MEMS gas sensor further includes: a Wheatstone bridge; the Wheatstone bridge is connected to the ZnO nanoplate; the Wheatstone bridge is used to measure the resistance of the ZnO nanoplate; The processor is connected to the Wheatstone bridge; the processor is used to determine whether the resistance change value is greater than a preset change value. If so, it is determined that the MEMS gas sensor is in a detection state; if not, it is determined that the MEMS gas sensor is in a non-detection state; wherein the resistance change value is the difference between the resistance at the current moment and the resistance at the previous moment.

5. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 2, characterized in that: The volatile organic compound monitoring system based on photothermal modulation enhancement also includes: a first low-pass filter, a first emitter follower, a second low-pass filter and a second emitter follower; The processor is used to generate a first PWM signal and a second PWM signal; the first PWM signal is used to adjust the output power of the heating plate; the second PWM signal is used to adjust the output power of the ultraviolet LED lamp to adjust the light source intensity of the ultraviolet LED lamp; The first low-pass filter and the second low-pass filter are respectively connected to the processor; the first low-pass filter is used to filter the first PWM signal to obtain a first DC voltage; the second low-pass filter is used to filter the second PWM signal to obtain a second DC voltage; The first emitter follower is connected to the first low-pass filter and the heating plate respectively; the first emitter follower is used to amplify the first DC voltage to obtain a first amplified voltage, and use the first amplified voltage to drive the heating plate to work; The second emitter follower is connected to the second low-pass filter and the ultraviolet LED lamp respectively; the second emitter follower is used to amplify the second DC voltage to obtain a second amplified voltage, and use the second amplified voltage to drive the ultraviolet LED lamp to work.

6. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 1, characterized in that: There are multiple MEMS gas sensors and multiple UV LED lamps, and the MEMS gas sensors correspond to the UV LED lamps one by one.

7. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 1, characterized in that: The volatile organic compound monitoring system based on photothermal modulation enhancement also includes: a USB-C interface and a Bluetooth module; the USB-C interface and the Bluetooth module are both connected to the processor; the USB-C interface is used to realize wired communication between the processor and the external device; the Bluetooth module is used to realize wireless communication between the processor and the external device.

8. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 1, characterized in that: The volatile organic compound monitoring system based on photothermal modulation enhancement also includes: a temperature and humidity sensor, an LED indicator light, a buzzer and a DIP switch; the temperature and humidity sensor, the LED indicator light, the buzzer and the DIP switch are all connected to the processor; The temperature and humidity sensor is used to measure the ambient temperature and humidity; The LED indicator light is used to indicate the working status of the volatile organic compound monitoring system based on photothermal modulation enhancement; The buzzer is used for alarm; The DIP switch is used to set the working state of the volatile organic compound monitoring system based on photothermal modulation enhancement.

9. The volatile organic compound monitoring system based on photothermal modulation enhancement according to claim 7, characterized in that: The volatile organic compound monitoring system based on photothermal modulation enhancement also includes: a battery, a power management unit and a plug terminal; The USB-C port and plug-in terminal are used to power the battery, MEMS gas sensor, UV LED lamp and processor through the power management unit; The battery is used to power the MEMS gas sensor, UV LED light, and processor via a power management unit.

10. A volatile organic compound monitoring method based on photothermal modulation enhancement, applied to the volatile organic compound monitoring system based on photothermal modulation enhancement according to any one of claims 1 to 9, characterized in that: The volatile organic compound monitoring method based on photothermal modulation enhancement includes: Adjust the operating temperature of the MEMS gas sensor so that the MEMS gas sensor operates at a preset operating temperature; Determine whether the MEMS gas sensor is in the detection state; If so, turn on the ultraviolet LED lamp and adjust the light source intensity of the ultraviolet LED lamp so that the ultraviolet LED lamp irradiates the MEMS gas sensor with a preset light source intensity, and receive detection data of the MEMS gas sensor until the MEMS gas sensor is in a non-detection state. At this time, turn off the ultraviolet LED lamp.

Images