Wireless molybdenum disulfide gas content detector

Abstract

The invention relates to a molybdenum disulfide gas detector. The molybdenum disulfide gas detector comprises a molybdenum disulfide gas sensor, a PCB (Printed Circuit Board), an NRF24L01 wireless module, an STM32F103C8T6 single chip microcomputer and an OLED (Organic Light Emitting Diode) display screen. The molybdenum disulfide gas sensor further comprises a substrate material, molybdenum disulfide, metal particles, a gate electrode, a source electrode and a drain electrode. The molybdenum disulfide gas sensor is characterized in that the molybdenum disulfide gas sensor, the NRF24L01 wireless module, the STM32F103C8T6 single-chip microcomputer and the OLED display screen form a circuit which is welded on the PCB. The molybdenum disulfide gas sensor inputs analog signals to the STM32F103C8T6 single-chip microcomputer, the STM32F103C8T6 single-chip microcomputer converts the analog signals into electric signals, the electric signals are transmitted to the NRF24L01 wireless module, the NRF24L01 wireless module sends out the electric signals, the NRF24L01 wireless module receives the electric signals, and the received signals are transmitted to the OLED display screen to be displayed. Compared with an existing gas sensor, the molybdenum disulfide gas detector is longer in service life, higher in sensitivity and excellent in selectivity to different gases.

Description

Technical Field

[0001] This invention relates to a wireless molybdenum disulfide gas content detector. A gas sensor can be integrated onto a 45mm×44mm PCB board for wireless signal transmission and reception, enabling remote detection of gas content. Background Technology

[0002] Ammonia released into the atmosphere reacts with gaseous pollutants such as sulfur dioxide and nitrogen oxides to form secondary aerosol particles that absorb and scatter light, reducing atmospheric visibility. Furthermore, prolonged exposure to high ammonia concentrations can damage and irritate the skin and respiratory system, leading to symptoms such as sore throat, chest tightness, difficulty breathing, and even poisoning. Therefore, monitoring ammonia concentrations in the environment is essential. In recent years, with the continuous development and advancement of modern human breath analysis technology, breath analysis-based ammonia sensors for disease diagnosis have received widespread attention from researchers both domestically and internationally. Ammonia, a significant component of exhaled gases, is an important physiological marker for diseases such as liver dysfunction, kidney disease, Helicobacter pylori infection, and oral diseases. In particular, the ammonia concentration in the exhaled gases of kidney disease patients can reach levels of 10 ppm. Therefore, breath analysis of NH3 can enable large-scale rapid screening, early prevention, and daily self-diagnosis of kidney disease. Currently, the detection and analysis of NH3 in exhaled gases often relies on techniques such as gas chromatography and mass spectrometry, but these equipment are expensive and require professional operation, making real-time online detection of NH3 difficult to achieve. Metal oxide semiconductor gas sensors are a good choice for detecting NH3 because of their simple structure, small size, low cost, and good compatibility with modern integrated circuit technology.

[0003] Currently, effective sensing methods used in human diagnostic breath tests can be broadly categorized into chromatography, mass spectrometry, spectroscopy, canine olfactory methods, electrochemical gas sensing, and metal oxide sensing. Chromatography, with its ability to rapidly separate single gases and extremely low detection limits, has been widely applied across various sectors, particularly playing a crucial role in the development of exhaled breath detection. However, the unique nature of chromatographic detection principles makes sample collection and preservation difficult, and different sample pretreatment processes can affect test results, significantly hindering its application and development in exhaled breath detection. With the increasing popularity of mass spectrometry, this technique has been combined with chromatography. Mass spectrometry incorporates various complex techniques, but its detection principle remains based on the ion mass-to-charge ratio, resulting in good quantitative detection capabilities and applications in agriculture, petrochemicals, and other fields. However, mass spectrometry requires expensive instruments and exhibits lower response to certain gas molecules. Spectroscopy is a rapidly developing gas detection technology in recent years. However, it requires a large number of samples for modeling and analysis, and its maintenance and purchase costs are high. Furthermore, uncontrollable factors can significantly impact the detection results. Electrochemical gas sensors utilize the electrochemical activity of the gas being detected, reducing or oxidizing it to determine its concentration and composition. Electrochemical gas sensors offer advantages in detecting exhaled gases, such as fast response and low cost. However, they also have significant drawbacks: they are difficult to adapt to complex exhaled gases, and factors such as temperature and humidity significantly affect their detection accuracy, requiring further signal anti-interference processing. Metal oxide sensing has attracted considerable attention from scholars both domestically and internationally, exhibiting excellent detection performance for exhaled gas molecules with relatively low molecular weights, such as NH3, HCHO, and C2H6O. Metal oxide sensors are categorized based on their components, including surface resistance-controlled gas sensors, sintered gas sensors, and overall resistance-controlled gas sensors. They have a wide range of applications and are inexpensive. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and obtain a wireless gas sensor using molybdenum disulfide (a single-layer thin film grown by CVD) as a substrate. Compared with existing gas sensors, this invention has a longer lifespan, higher sensitivity, and excellent selectivity for different gases; it is also smaller and more integrated than existing molybdenum disulfide gas sensors, and can achieve the function of remotely detecting gas concentration, which these sensors lack.

[0005] The molybdenum disulfide gas content detector provided by this invention, such as... Figure 3As shown—the bottom layer is a doped p-type silicon wafer connected to the gate (its electrical properties can be altered by controlling the carrier behavior of the semiconductor material in the channel through the application of a gate voltage). The middle layer is a thin insulating layer (approximately 300nm thick silicon dioxide, which prevents leakage caused by the silicon wafer connecting to the electrode or by external current directly entering the lower silicon wafer). The top layer is an L-type electrode with high Ti content (approximately 30nm thick), with one end connected to the source and the other to the drain. The middle of the channel is a 0.2nm ruthenium-modified monolayer of molybdenum disulfide material.

[0006] The sensitive layer used in this invention is molybdenum disulfide (MoD), a relatively mature two-dimensional gas detection material with excellent gas response. MoD is an n-type semiconductor, primarily conductive by electrons. Ammonia is a reducing gas; when ammonia is adsorbed onto the MoD sensitive layer, the nitrogen in the ammonia donates electrons to the n-type semiconductor MoD, narrowing the surface electron depletion layer and increasing the internal electron concentration, thus decreasing the resistance. By detecting the resistance change under different ammonia concentrations and converting it into a response value, it can be used for ammonia concentration detection in clinical applications.

[0007] The gas sensor used in this invention is a molybdenum disulfide thin film modified with metal particles, which has good gas response, long lifespan, and different metal particles are selective for different gases, thereby enabling the detection of different gases.

[0008] This invention utilizes the built-in ADC (Digital-to-Analog Converter) of the STM32F103C8T6 microcontroller to convert analog signals, which are difficult to transmit, into electrical signals, which are easy to transmit, thereby realizing wireless transmission.

[0009] This invention incorporates an NRF24L012.4G wireless module on the PCB board, enabling wireless sensing and remote detection of gas content. This makes it more convenient and flexible to use.

[0010] This invention uses a PCB integrated circuit board to make the detector highly integrated, which greatly reduces the size and cost of existing gas sensors.

[0011] In summary, this invention leverages the inherently superior sensing properties of molybdenum disulfide (MoS2). By modifying the surface of MoS2 with different metal particles, gases are more easily adsorbed onto the MoS2 thin film, thereby modulating the semiconductor conductivity and achieving selective response to different gases. This results in a gas sensor that is selective, low-cost, highly active, highly sensitive, highly practical, and stable. The fabricated device is then mounted on a wirelessly transmitting PCB, converting the sensor's analog signal into an easily detectable electrical signal, enabling long-distance gas detection and giving it practical significance and value. Attached Figure Description

[0012] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0013] Figure 1 This is a front view of the receiver of the molybdenum disulfide gas detector provided by the present invention. 1 is an STM32F103C8T6 microcontroller chip, 2 is an NRFL2401 wireless module chip, 3 is a USB interface, and 4 is a receiving antenna.

[0014] Figure 2 This is a schematic diagram of the back of the receiver of the molybdenum disulfide gas detector provided by the present invention. 1 represents the location where the OLED display screen is placed.

[0015] Figure 3 The specific structure of the molybdenum disulfide gas sensor consists of a bottom layer of doped p-type silicon wafer connected to the gate (its electrical properties can be altered by controlling the carrier behavior of the semiconductor material in the channel through the application of a gate voltage). The middle layer is a thin insulating layer (approximately 300 nm thick silicon dioxide, which prevents leakage caused by the silicon wafer connecting to the electrode or by external current directly entering the lower silicon wafer). The top layer is an L-type electrode with high Ti content (approximately 30 nm thick), with one end connected to the source and the other to the drain. The middle of the channel is a 0.2 nm ruthenium-modified monolayer of molybdenum disulfide material.

[0016] Figure 4 This is a magnified image of the L-shaped channel and material of the substrate under a magnifying optical microscope. Detailed Implementation

[0017] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0018] Example 1 The device structure is as described above, such as Figure 3 As shown—the bottom layer is a doped p-type silicon wafer connected to the gate (its electrical properties can be altered by controlling the carrier behavior of the semiconductor material in the channel through the application of a gate voltage). The middle layer is a thin insulating layer (approximately 300nm thick silicon dioxide, which prevents leakage caused by the silicon wafer connecting to the electrode or by external current directly entering the lower silicon wafer). The top layer is an L-type electrode with high Ti content (approximately 30nm thick), with one end connected to the source and the other to the drain. The middle of the channel is a 0.2nm ruthenium-modified monolayer of molybdenum disulfide material. Figure 4 This is a magnified image of the L-shaped channel and material of the substrate under a magnifying optical microscope.

Claims

1. A wireless molybdenum disulfide gas content detector, characterized in that... The invention includes a molybdenum disulfide gas sensor (1), a PCB board (2), an NRF24L01 wireless module (3), an STM32F103C8T6 microcontroller (4), and an OLED display screen (5). The molybdenum disulfide gas sensor also includes: a silicon wafer (6), silicon dioxide (7), a titanium L-shaped electrode (8), molybdenum disulfide material (9), and ruthenium particles (10). The invention is characterized in that the molybdenum disulfide gas sensor (1), the NRF24L01 wireless module (3), the STM32F103C8T6 microcontroller (4), and the OLED display screen (5) form a circuit that is soldered onto the PCB board (2).

2. The molybdenum disulfide gas content detector according to claim 1, characterized in that, The substrate (1) is an insulating substrate, such as an intrinsic silicon wafer or an Al2O3 crystal substrate.

3. The molybdenum disulfide gas content detector according to claim 1, characterized in that, The modification material is a monolayer CVD-grown molybdenum disulfide modified with the noble metal ruthenium. The ruthenium is modified onto the molybdenum disulfide on the substrate by a PVD method using magnetron sputtering, with a thickness of no more than 1 nm.

4. The molybdenum disulfide gas content detector according to claim 1, characterized in that, The thickness of molybdenum disulfide ranges from 0.7 to 20 nanometers.

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