A gas detector for detecting concentration of formaldehyde based on surface plasmon resonance

Abstract

The application discloses a gas detector for detecting formaldehyde concentration based on surface plasmon resonance, and relates to the technical field of gas detection.The detector comprises an optical detection unit, an electrical detection unit, a sensitive film layer, a hot electron-electrical signal intelligent processing module and a signal processing unit.The application realizes high precision and high sensitivity of formaldehyde concentration detection by fusing the optical detection unit, the electrical detection unit, the sensitive film layer, the hot electron-electrical signal intelligent processing module and the signal processing unit.The optical detection unit utilizes the SPR phenomenon, and through precise optical path design and a laser constant temperature control system, the stability and accuracy of the optical signal are ensured, thereby providing a reliable basis for subsequent detection.The electrical detection unit collects hot electron current signals through electrodes, thereby further enhancing the sensitivity of detection.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, specifically to a gas detector for detecting formaldehyde concentration based on surface plasmon resonance. Background Technology

[0002] With the increasing prominence of indoor air quality problems, the need for formaldehyde concentration monitoring, as a typical volatile organic pollutant, is becoming more urgent in the fields of smart homes, industrial safety, and environmental health. Traditional formaldehyde detection technologies mainly rely on electrochemical sensors, semiconductor sensors, or spectroscopic analysis, but they generally suffer from insufficient sensitivity, poor selectivity, or bulky equipment. Surface plasmon resonance (SPR) technology, due to its high sensitivity to changes in film refractive index, has gradually become a research hotspot in the field of gas sensing. However, single SPR detection is easily affected by ambient temperature, humidity, and non-target gases, resulting in insufficient signal stability and anti-interference ability. In addition, traditional technologies have high detection limits for low concentrations of formaldehyde, making it difficult to meet the needs of high-precision air quality monitoring. Therefore, developing a formaldehyde detection technology that combines high sensitivity, strong selectivity, and real-time performance has become a key challenge in the current environmental monitoring field.

[0003] Existing formaldehyde detection technologies have several limitations. While electrochemical sensors are inexpensive, they are susceptible to cross-sensitivity, leading to false alarms for other volatile organic compounds. Semiconductor sensors require high-temperature operation, resulting in high power consumption and short lifespan. Although spectroscopic analysis can achieve non-contact detection, the equipment is complex and expensive, hindering widespread application. In SPR technology applications, traditional structures rely solely on light intensity or phase changes for detection, lacking active control over the behavior of hot electrons, leading to severe signal drift in complex environments. Furthermore, traditional signal processing methods often employ threshold judgment or simple fitting algorithms, which cannot effectively resolve the weak signal changes caused by low concentrations of formaldehyde, limiting the improvement of the detection limit. In addition, the design of sensitive membrane materials generally suffers from low adsorption capacity and poor regenerability, resulting in significant performance degradation after long-term use, further affecting detection reliability.

[0004] Therefore, developing a gas detector for formaldehyde concentration based on surface plasmon resonance not only significantly improves detection sensitivity and selectivity, but also enhances the detector's anti-interference capability in complex environments. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a gas detector for detecting formaldehyde concentration based on surface plasmon resonance. Through a dual-modal detection mechanism of optical and electrical modes, combined with a sensitive membrane layer that has a specific adsorption function for formaldehyde, the detector achieves accurate identification of formaldehyde concentration. The detector innovatively introduces a hot electron-electric signal intelligent processing module and uses discretization coding, interference modulation and machine learning algorithms to solve the nonlinear error problem of traditional sensors in low-concentration detection.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A gas detector for detecting formaldehyde concentration based on surface plasmon resonance, the detector comprising: an optical detection unit, an electrical detection unit, a sensitive film layer, a thermionic-electrical signal intelligent processing module, and a signal processing unit; The optical detection unit consists of a laser, a collimating lens, a prism, a metal thin film, and a photodetector. The light emitted by the laser is collimated by the collimating lens and passes through the prism at a 45-degree angle. At the prism-metal thin film interface, surface plasmon resonance is excited to generate plasmons. The photodetector collects the intensity and phase signals of the reflected light. The electrical detection unit consists of an electrode pair and a current measuring device, and is disposed on the surface of a metal thin film. Plasmon decay generates hot electrons, the electrode pair collects the hot electron current signal, and the current measuring device converts the current signal into an electrical signal for output. The sensitive membrane layer is made of a functional material that specifically adsorbs formaldehyde and is coated on the surface of a metal thin film. When formaldehyde is adsorbed, the electronic structure of the membrane layer changes, affecting the generation, transport, and phase of hot electrons. The thermionic-electric signal intelligent processing module consists of a thermionic-electric signal discretization submodule, an electrical signal interference control submodule, and a machine learning decoding submodule. The signal processing unit is connected to the photodetector, the current measuring device, and the thermionic-electric signal intelligent processing module, respectively, and performs signal acquisition, preprocessing, and integration of decoding results.

[0007] Furthermore, in the optical detection unit, the laser is equipped with a constant temperature control system, and the optical path of the optical detection unit is provided with a half-wave plate and a polarizing beam splitter. After processing by the half-wave plate and the polarizing beam splitter, the P-polarized light component is greater than 99%. The metal thin film is made by sequentially depositing a 10nm titanium adhesion layer and a 50nm gold film on the bottom surface of the prism through an electron beam evaporation process. The roughness of the metal thin film is less than 0.5nm, and the crystallinity is greater than 95%.

[0008] Furthermore, in the electrical detection unit, the electrode pair is a platinum interdigitated electrode array fabricated on the surface of a metal thin film using a photolithography process. The electrode width is 5 μm, the spacing is 5 μm, and the effective detection area is 1 mm². 2 The electrode surface is modified with a self-assembled monolayer of 11-mercaptoundecanoic acid.

[0009] Furthermore, the functional material in the sensitive membrane layer that specifically adsorbs formaldehyde is one of the following: metal porphyrin compounds, MOFs, or nano-titanium dioxide composite materials.

[0010] Furthermore, in the sensitive film layer, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin zinc is fixed to the electrode surface modified with a self-assembled monolayer film using an EDC / NHS chemical coupling method, with a loading of 0.5-1 nmol / cm³. 2 The sensitive film layer also includes ZIF-8 nanocrystals grown in situ on the electrode surface. The ZIF-8 nanocrystals have an average particle size of 80 nm, and porphyrin compound molecules are encapsulated in the channels of the ZIF-8 nanocrystals to form a core-shell structure. The specific surface area of ​​the core-shell structure is greater than 1000 m². 2 / g, the sensitive membrane layer changes its electronic structure after adsorbing formaldehyde, affecting the generation efficiency, transmission rate and phase characteristics of hot electrons.

[0011] Furthermore, the specific contents of the thermionic-electrical signal discretization submodule, the electrical signal interference control submodule, and the machine learning decoding submodule in the thermionic-electrical signal intelligent processing module are as follows: The thermoelectro-electric signal discretization submodule receives the thermoelectro current signal output by the electrical detection unit and discretizes the continuous current signal into an electrical signal sequence through a thermoelectro-electric signal encoding algorithm. The electrical signal interference control submodule utilizes the SPR optical signal of the optical unit, calculates the phase change of electrical signal interference based on the phase change of hot electrons caused by formaldehyde adsorption, performs interference control on the electrical signal sequence, and generates an electrical signal interference state carrying formaldehyde information. The machine learning decoding submodule uses a signal feature mapping algorithm to invert formaldehyde concentration from the electrical signal level, converting the feature information of the light-electric signal into a specific formaldehyde concentration value.

[0012] Furthermore, in the thermionic-electrical signal intelligent processing module, the calculation formula for the thermionic-electrical signal encoding algorithm is as follows: ,in, It is the discrete electrical signal sequence corresponding to the thermionic signal. It is the number of the electrical signal sequence, with values ​​ranging from 0 to... integers, The total number of electrical signal sequences is set. These are discrete sampled values ​​of the thermionic current, obtained by the current measuring device of the electrical detection unit sampling the thermionic current at equal intervals. The baseline current is determined by averaging multiple measurements in a standard clean environment. This is a parameter that controls the encoding width, used to adjust the range of the current signal mapped to the electrical signal sequence. It is the hot electron lifetime. For plasmon lifetime, and is the weighted component of the electrical signal sequence, and erf is the error function that realizes the mapping between current and electrical signal sequence.

[0013] Furthermore, in the aforementioned thermionic-electrical signal intelligent processing module, the calculation formula for the electrical signal interference control algorithm is as follows: ; ,in It is the phase change of the electrical signal interference. It is the SPR phase measured by the optical unit. This represents the change in the lifetime of hot electrons. It is the reference hot electron lifetime when there is no formaldehyde adsorption. It is the coupling coefficient, determined by the efficiency of the sensitive film. To compensate for the phase, It is an electrical signal sequence after electrical signal interference modulation. It is the discrete electrical signal sequence corresponding to the thermionic signal. It is the product operator for electrical signals, used to represent combinations of different electrical signals. It is a time-dependent phase coefficient. It is the Hadmar coefficient. It is a reference electrical signal, serving as the initial reference signal for electrical signal interference control.

[0014] Furthermore, in the aforementioned thermionic-electrical signal intelligent processing module, the calculation formula for the signal feature mapping algorithm is as follows: ,in It refers to formaldehyde concentration. It is the concentration calibration coefficient. It is an electrical signal interference state signal. It's a neural network. It is a signal feature extraction function. It is a characteristic signal of surface plasmon resonance optical signal. It is a product operation of electrical signals. Characteristic signals of hot electron signals It is a concentration reference signal. It is the correlation regularization coefficient. It is the signal correlation coefficient.

[0015] Compared with existing technologies, this gas detector for formaldehyde concentration based on surface plasmon resonance has the following advantages: I. This invention achieves high sensitivity and specificity in formaldehyde concentration identification by combining surface plasmon resonance technology with a multi-unit collaborative detection mechanism. The electrophysiological detection unit utilizes plasmons generated by surface plasmon resonance to accurately capture changes in the electronic structure of the membrane layer caused by formaldehyde adsorption. Simultaneously, the electrical detection unit directly acquires the thermionic current signal, forming a complementary photo-electric dual-mode detection system. The sensitive membrane layer uses functional materials with specific adsorption for formaldehyde, combined with core-shell structure design and molecular encapsulation technology, which enhances the selective adsorption capacity of the membrane layer for formaldehyde and avoids interference from other volatile organic compounds. This multi-dimensional detection architecture not only improves detection sensitivity but also achieves real-time inversion of formaldehyde concentration through machine learning decoding of the thermionic-electric signal intelligent processing module, providing a more accurate technical means for indoor air quality monitoring.

[0016] Second, this invention overcomes the limitations of traditional gas sensor signal analysis through algorithmic innovation in the intelligent processing module. The thermionic-electrical signal discretization submodule converts the continuous current signal into a discrete electrical signal sequence. Combined with the dynamic response of the electrical signal interference modulation submodule to the SPR phase change, an interference state signal carrying formaldehyde characteristic information is generated. The machine learning decoding submodule further converts the photoelectric signal characteristics into formaldehyde concentration values ​​through a signal feature mapping algorithm, effectively solving the nonlinear error problem of traditional sensors in low-concentration detection. In addition, the core-shell structure design of the sensitive film layer enhances the generation efficiency and transmission stability of thermionic electrons. Combined with the real-time calibration capability of the intelligent processing module, the detector can maintain high repeatability and long-term stability in complex environments, providing a reliable formaldehyde monitoring solution for smart homes, industrial safety and other fields.

[0017] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0018] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings: Figure 1 The flowchart shows the structure of a gas detector for detecting formaldehyde concentration based on surface plasmon resonance. Figure 2 Here is a flowchart of the thermionic-electrical signal intelligent processing module; Figure 3This is a flowchart of the detector signal interaction and data processing. Figure 4 This is a schematic diagram of the optical path structure of the optical detection unit. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A gas detector for formaldehyde concentration detection based on surface plasmon resonance.

[0021] Overall structure and connection relationships of the detector: The detector consists of an optical detection unit, an electrical detection unit, a sensitive film layer, a hot electron-electric signal intelligent processing module, and a signal processing unit. These units work collaboratively through physical integration and electrical signal transmission. Figure 1 As shown, the laser, collimating lens, prism, metal thin film, and photodetector in the optical detection unit are arranged in sequence to form an optical path. The metal thin film is deposited on the bottom surface of the prism, and the photodetector is electrically connected to the electrical signal processing unit to transmit optical signals. The platinum interdigitated electrode array of the electrical detection unit is set on the surface of the metal thin film, and the electrode pairs are connected to the current measuring device through wires. The output end of the current measuring device is connected to the signal processing unit. The sensitive film layer is coated on the surface of the metal thin film and the electrodes and is in direct contact with the optical and electrical units. The three sub-modules of the hot electron-electric signal intelligent processing module all communicate bidirectionally with the signal processing unit, receive the pre-processed signal, and feed back the decoding result.

[0022] The specific structure and function of each unit: Optical Detection Unit: The laser is a 633nm semiconductor laser, externally encased in a constant temperature control system. Through Peltier effect cooling and heating, temperature fluctuations are precisely controlled within ±0.01℃ to avoid wavelength changes caused by temperature drift. A half-wave plate and a polarizing beam splitter are sequentially arranged in the optical path. The half-wave plate rotates to adjust the polarization direction of the light, and the polarizing beam splitter filters the light to ensure that the P-polarized component is greater than 99%, guaranteeing that the incident light excites surface plasmon resonance with a high degree of polarization. The prism is a right-angle glass prism, with a 10nm titanium adhesion layer deposited on the bottom surface using electron beam evaporation, followed by the growth of a 50nm gold film. The metal film roughness is less than 0.5nm, and the crystallinity is greater than 95%, ensuring efficient excitation of surface plasmon polaritons. The photodetector is a high-speed InGaAs detector, which collects the intensity and phase signals of the reflected light in real time at a sampling frequency of 10kHz.

[0023] Electrical detection unit: A platinum interdigitated electrode array is fabricated on the surface of a metal thin film using photolithography. The electrode width and spacing are both 5 μm, resulting in an effective detection area of ​​1 mm². 2 The electrode surface is modified with a 11-mercaptoundecanoic acid self-assembled monolayer film, which provides anchoring points for the sensitive film layer and regulates interfacial electron transport. When plasmon decay generates hot electrons, the electrode pair collects these hot electrons to form a current. The current measuring device (low-noise current amplifier) ​​converts the picoampere-level current signal into a voltage signal output with an amplification factor of 10. 6 .

[0024] Sensitive film layer: 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin zinc (Zn-TCPP) was immobilized on the electrode surface modified with a self-assembled monolayer film via EDC / NHS chemical coupling, with a loading of 0.7 nmol / cm². 2 Simultaneously, ZIF-8 nanocrystals with an average particle size of 80 nm were grown in situ on the electrode surface. Porphyrin compound molecules were encapsulated within their channels to form a core-shell structure, resulting in a specific surface area of ​​1200 m². 2 / g, Zn-TCPP has a specific coordination adsorption effect on formaldehyde, the porous structure of ZIF-8 increases the adsorption capacity, and the core-shell structure synergistically optimizes the electron transport path.

[0025] Thermionic-Electronic Signal Intelligent Processing Module: Thermionic-Electronic Signal Discretization Submodule receives thermionic current signal output from the electrical detection unit and discretizes the continuous current signal into an electrical signal sequence through a thermionic electrical signal encoding algorithm. The calculation formula for the thermionic electrical signal encoding algorithm is as follows: The electrical signal interference modulation submodule utilizes the SPR optical signal from the optical unit. Based on the phase change of hot electrons caused by formaldehyde adsorption, it calculates the phase change of electrical signal interference using an electrical signal interference modulation algorithm. This algorithm then modulates the electrical signal sequence to generate an electrical signal interference state carrying formaldehyde information. The calculation formula for the electrical signal interference modulation algorithm is as follows: ; The machine learning decoding submodule uses a signal feature mapping algorithm to invert formaldehyde concentration from the electrical signal level, converting the feature information of the light-electric signal into a specific formaldehyde concentration value. The calculation formula for the signal feature mapping algorithm is as follows: Concentration calibration coefficient The entanglement regularization coefficient is 0.5. A value of 0.1 converts quantum state information into a specific concentration value, such as... Figure 2 As shown.

[0026] Signal processing unit: Implemented by FPGA chip, it synchronously acquires the optical signal (sampling rate 10kHz) from the photodetector and the electrical signal (sampling rate 100kHz) from the current measuring device, performs filtering and amplification processing, transmits the pre-processed signal to the thermionic-electrical signal intelligent processing module, integrates the decoding results, outputs the formaldehyde concentration value through the serial port, and drives the LCD screen to display it in real time.

[0027] Working principle: Zn-TCPP in the sensitive film layer has a specific coordination adsorption effect on formaldehyde, and the porous structure of ZIF-8 increases the adsorption capacity. The two work together to change the refractive index and electrical properties of the sensitive film layer after adsorbing formaldehyde. In the optical detection unit, the light emitted by the 633nm laser is processed to obtain high polarization degree P-polarized light. After being incident on the prism, it excites the surface plasmon resonance on the surface of the metal thin film. The intensity and phase changes of the reflected light are collected by the high-speed InGaAs detector and transmitted to the signal processing unit. The platinum interdigitated electrode array of the electrical detection unit collects the thermionic current generated by the decay of surface plasmon polaritons. After being amplified by the low-noise current amplifier, it is transmitted to the signal processing unit. The signal processing unit simultaneously collects and preprocesses the optical and electrical signals and transmits them to the thermionic-electrical signal intelligent processing module. This module first discretizes the thermionic current signal into an electrical signal sequence, then combines it with the SPR optical signal to generate an electrical signal interference state carrying formaldehyde information. Finally, the formaldehyde concentration is obtained by inversion through the machine learning decoding submodule. The signal processing unit integrates the results and outputs them through the serial port to drive the LCD screen for real-time display.

[0028] Example 2: Real-time monitoring of formaldehyde concentration in home indoor spaces.

[0029] During home renovation, various boards and paints may continuously release formaldehyde. Formaldehyde is a colorless but irritating gas, and long-term exposure can pose a potential threat to human health (such as causing respiratory discomfort and allergic reactions). Therefore, a device that can monitor indoor formaldehyde concentration 24 hours a day is needed so that residents can keep track of the environmental safety status at any time and take timely measures such as ventilation and use air purifiers when the concentration exceeds the standard.

[0030] Operation of the optical detection unit: The laser emits a stable beam, which is collimated by a collimating lens into a parallel beam and precisely incident on a prism at a 45-degree angle. At the interface between the prism and the metal film, the light excites a surface plasmon resonance effect, forming an electron compression-sparse wave (i.e., plasmon resonance) that propagates along the metal-dielectric interface. The photodetector continuously collects the intensity and phase signals of the reflected light. During this process, the laser's temperature control system keeps the laser temperature fluctuation within a very small range, ensuring the stability of light emission. The half-wave plate and polarizing beam splitter in the optical path efficiently filter the light, making the P-polarized light component absolutely dominant, laying a precise optical foundation for subsequent detection.

[0031] The electrical detection unit works as follows: When plasmons decay, they release hot electrons. The platinum interdigitated electrode array on the surface of the metal thin film quickly captures the current signal formed by these hot electrons. The current measurement device then converts the weak current signal into an easily processed electrical signal output. The self-assembled monolayer film modified on the electrode surface optimizes the interaction between the electrode and the hot electrons, improving the efficiency and stability of signal acquisition.

[0032] The sensitive membrane plays a role: The sensitive membrane coated on the surface of the metal film uses functional materials (such as metalloporphyrin compounds) that have a specific ability to recognize formaldehyde. When formaldehyde molecules in indoor air come into contact with the membrane with the airflow, they are specifically adsorbed. This adsorption behavior will cause subtle changes in the electronic structure of the membrane, which will affect the number of hot electrons generated, the transport path and the phase characteristics. These changes become the key signals for subsequent detection of formaldehyde concentration.

[0033] The thermal electron-electric signal intelligent processing module processes signals: The thermionic-electrical signal discretization submodule receives the thermionic current signal output from the electrical detection unit and discretizes the continuous current signal into an electrical signal sequence using a thermionic electrical signal encoding algorithm. The calculation formula for the thermionic electrical signal encoding algorithm is as follows: ,in, It is the discrete electrical signal sequence corresponding to the thermionic signal. It is the number of the electrical signal sequence, with values ​​ranging from 0 to... integers, The total number of electrical signal sequences is set. These are discrete sampled values ​​of the thermionic current, obtained by the current measuring device of the electrical detection unit sampling the thermionic current at equal intervals. The baseline current is determined by averaging multiple measurements in a standard clean environment. This is a parameter that controls the encoding width, used to adjust the range of the current signal mapped to the electrical signal sequence. It is the hot electron lifetime. For plasmon lifetime, and is the weighted component of the electrical signal sequence, and erf is the error function that realizes the mapping between current and electrical signal sequence.

[0034] The electrical signal interference modulation submodule utilizes the SPR optical signal from the optical unit and, based on the phase change of hot electrons caused by formaldehyde adsorption, calculates the phase change of electrical signal interference using an electrical signal interference modulation algorithm. This algorithm then modulates the electrical signal sequence through interference. The calculation formula for the electrical signal interference modulation algorithm is as follows: ; ,in It is the phase change of the electrical signal interference. It is the SPR phase measured by the optical unit. This represents the change in the lifetime of hot electrons. It is the reference hot electron lifetime when there is no formaldehyde adsorption. It is the coupling coefficient, determined by the efficiency of the sensitive film. To compensate for the phase, It is an electrical signal sequence after electrical signal interference modulation. It is the discrete electrical signal sequence corresponding to the thermionic signal. It is the product operator for electrical signals, used to represent combinations of different electrical signals. It is a time-dependent phase coefficient. It is the Hadmar coefficient. It is a reference electrical signal, serving as the initial reference signal for electrical signal interference control.

[0035] The machine learning decoding submodule uses a signal feature mapping algorithm to invert formaldehyde concentration from the electrical signal level, converting the feature information of the light-electric signal into a specific formaldehyde concentration value. The calculation formula for the signal feature mapping algorithm is as follows: ,in It refers to formaldehyde concentration. It is the concentration calibration coefficient. It is an electrical signal interference state signal. It's a neural network. It is a signal feature extraction function. It is a characteristic signal of surface plasmon resonance optical signal. It is a product operation of electrical signals. Characteristic signals of hot electron signals It is a concentration reference signal. It is the correlation regularization coefficient. It is the signal correlation coefficient.

[0036] Signal processing unit integration results: The signal processing unit, synchronously connected to the photodetector, current measuring device, and thermionic-electric signal intelligent processing module, collects various signals in real time and performs noise reduction and amplification preprocessing. Subsequently, it deeply integrates and analyzes optical signals, electrical signals, and quantum decoding results, ultimately presenting the indoor formaldehyde concentration value intuitively via a digital display screen and mobile APP push notifications, allowing residents to clearly understand the environmental safety status. Figure 3 As shown.

[0037] In summary, in the scenario of real-time formaldehyde concentration monitoring in homes, this device can monitor formaldehyde concentration 24 hours a day, ensuring residents' health. During operation, the laser in the optical detection unit emits a beam, which, after processing, excites surface plasmon resonance. The photodetector collects the reflected light signal, and constant temperature control and polarization processing ensure stable and accurate signal transmission. The platinum interdigitated electrode array in the electrical detection unit captures the current signal formed by hot electrons, which is amplified and output. The specific material of the sensitive film layer adsorbs formaldehyde, causing changes in the film layer and affecting the characteristics of hot electrons. The hot electron-electric signal intelligent processing module processes the signal through discretization, interference modulation, and machine learning decoding algorithms to invert the formaldehyde concentration. The signal processing unit integrates and preprocesses the signal, and after fusion analysis, presents the concentration value in an intuitive way, making it easy for residents to understand the environmental safety status and take corresponding measures. Figure 4 As shown.

[0038] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A gas detector for detecting formaldehyde concentration based on surface plasmon resonance, characterized in that, The detector includes: an optical detection unit, an electrical detection unit, a sensitive film layer, a hot electron-electric signal intelligent processing module, and a signal processing unit; The optical detection unit consists of a laser, a collimating lens, a prism, a metal thin film, and a photodetector. The light emitted by the laser is collimated by the collimating lens and passes through the prism at a 45-degree angle. At the prism-metal thin film interface, surface plasmon resonance is excited to generate plasmons. The photodetector collects the intensity and phase signals of the reflected light. The electrical detection unit consists of an electrode pair and a current measuring device, and is disposed on the surface of a metal thin film. Plasmon decay generates hot electrons, the electrode pair collects the hot electron current signal, and the current measuring device converts the current signal into an electrical signal for output. The sensitive membrane layer is made of a functional material that specifically adsorbs formaldehyde and is coated on the surface of a metal thin film. When formaldehyde is adsorbed, the electronic structure of the membrane layer changes, affecting the generation, transport, and phase of hot electrons. The thermionic-electric signal intelligent processing module consists of a thermionic-electric signal discretization submodule, an electrical signal interference control submodule, and a machine learning decoding submodule. The signal processing unit is connected to the photodetector, the current measuring device, and the thermionic-electric signal intelligent processing module, respectively, and performs signal acquisition, preprocessing, and integration of decoding results. The specific contents of the thermionic-electrical signal intelligent processing module, the thermionic-electrical signal discretization submodule, the electrical signal interference control submodule, and the machine learning decoding submodule are as follows: The thermoelectro-electric signal discretization submodule receives the thermoelectro current signal output by the electrical detection unit and discretizes the continuous current signal into an electrical signal sequence through a thermoelectro-electric signal encoding algorithm. The electrical signal interference control submodule utilizes the SPR optical signal of the optical unit, calculates the phase change of electrical signal interference based on the phase change of hot electrons caused by formaldehyde adsorption, performs interference control on the electrical signal sequence, and generates an electrical signal interference state carrying formaldehyde information. The machine learning decoding submodule: uses a signal feature mapping algorithm to invert formaldehyde concentration from the electrical signal level, and converts the feature information of the light-electric signal into a specific formaldehyde concentration value; In the aforementioned thermionic-electrical signal intelligent processing module, the calculation formula for the electrical signal interference control algorithm is as follows: ; ,in It is the phase change of the electrical signal interference. It is the SPR phase measured by the optical unit. This represents the change in the lifetime of hot electrons. It is the reference hot electron lifetime when there is no formaldehyde adsorption. It is the coupling coefficient, determined by the efficiency of the sensitive film. To compensate for the phase, It is an electrical signal sequence after electrical signal interference modulation. It is the discrete electrical signal sequence corresponding to the thermionic signal. It is the product operator for electrical signals, used to represent combinations of different electrical signals. It is a time-dependent phase coefficient. It is the Hadmar coefficient. It is a reference electrical signal, serving as the initial reference signal for electrical signal interference control.

2. The gas detector for detecting formaldehyde concentration based on surface plasmon resonance according to claim 1, characterized in that, In the optical detection unit, the laser is equipped with a constant temperature control system. The optical path of the optical detection unit is equipped with a half-wave plate and a polarizing beam splitter. After processing by the half-wave plate and polarizing beam splitter, the P-polarized light component is greater than 99%. The metal thin film is made by sequentially depositing a 10nm titanium adhesion layer and a 50nm gold film on the bottom surface of the prism through an electron beam evaporation process. The roughness of the metal thin film is less than 0.5nm and the crystallinity is greater than 95%.

3. A gas detector for detecting formaldehyde concentration based on surface plasmon resonance according to claim 1, characterized in that, In the electrical detection unit, the electrode pair is a platinum interdigitated electrode array fabricated on the surface of a metal thin film using a photolithography process. The electrode width is 5 μm, the spacing is 5 μm, and the effective detection area is 1 mm². 2 The electrode surface is modified with a self-assembled monolayer of 11-mercaptoundecanoic acid.

4. A gas detector for detecting formaldehyde concentration based on surface plasmon resonance according to claim 1, characterized in that, The functional material in the sensitive membrane layer that specifically adsorbs formaldehyde is one of the following: metal porphyrin compounds, MOFs, or nano-titanium dioxide composite materials.

5. A gas detector for detecting formaldehyde concentration based on surface plasmon resonance according to claim 1, characterized in that, In the sensitive film layer, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin zinc is fixed to the electrode surface modified with a self-assembled monolayer film by EDC / NHS chemical coupling, with a loading of 0.5-1 nmol / cm³. 2 The sensitive film layer also includes ZIF-8 nanocrystals grown in situ on the electrode surface. The ZIF-8 nanocrystals have an average particle size of 80 nm, and porphyrin compound molecules are encapsulated in the channels of the ZIF-8 nanocrystals to form a core-shell structure. The specific surface area of ​​the core-shell structure is greater than 1000 m². 2 / g, the sensitive membrane layer changes its electronic structure after adsorbing formaldehyde, affecting the generation efficiency, transmission rate and phase characteristics of hot electrons.

6. A gas detector for detecting formaldehyde concentration based on surface plasmon resonance according to claim 1, characterized in that, In the aforementioned thermionic-electrical signal intelligent processing module, the calculation formula for the thermionic-electrical signal encoding algorithm is as follows: ,in, It is the discrete electrical signal sequence corresponding to the thermionic signal. It is the number of the electrical signal sequence, with values ​​ranging from 0 to... integers, The total number of electrical signal sequences is set. These are discrete sampled values ​​of the thermionic current, obtained by the current measuring device of the electrical detection unit sampling the thermionic current at equal intervals. The baseline current is determined by averaging multiple measurements in a standard clean environment. This is a parameter that controls the encoding width, used to adjust the range of the current signal mapped to the electrical signal sequence. It is the hot electron lifetime. For plasmon lifetime, and It is the weighted component of the electrical signal sequence, and erf is the error function, realizing the mapping between current and electrical signal sequence.

7. A gas detector for detecting formaldehyde concentration based on surface plasmon resonance according to claim 1, characterized in that, In the aforementioned thermionic-electric signal intelligent processing module, the calculation formula for the signal feature mapping algorithm is as follows: ,in It refers to formaldehyde concentration. It is the concentration calibration coefficient. It is an electrical signal interference state signal. It's a neural network. It is a signal feature extraction function. It is a characteristic signal of surface plasmon resonance optical signal. It is a product operation of electrical signals. Characteristic signals of hot electron signals It is a concentration reference signal. It is the correlation regularization coefficient. It is the signal correlation coefficient.

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