Preparation and application of proton conduction mode regulated titanate sensing material

Abstract

The invention belongs to the technical field of gas sensors, and particularly relates to preparation and application of a titanate sensing material regulated and controlled in a proton conduction mode. According to the sensor, anatase type titanium dioxide powder with the particle size of 200-300 nm is adopted as a precursor, sodium hydroxide is added for a hydrothermal reaction, ion exchange is conducted through a 10 <-4 > mol / L to 10 <-2 > mol / L HCl solution, sodium ions are replaced with hydrogen ions, and an H-NTO advanced sensing material with reliability and stability is successfully synthesized. The unique surface structure and proton conduction characteristic of the H-NTO material significantly improve the adsorption capacity and response sensitivity of the H-NTO material to formaldehyde molecules. In the preparation process, the adopted ion exchange method is simple and environment-friendly, and the crystal structure and the electrochemical performance of H-NTO can be accurately controlled. The formaldehyde sensor has the advantages of quick response, low detection limit, good selectivity and long-time stability, is suitable for real-time detection of formaldehyde, and particularly has wide application prospects in the fields of indoor air quality monitoring, early diagnosis of diseases and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and particularly relates to the preparation and application of a titanate sensing material with proton conduction mode regulation. Background Art

[0002] In recent years, with the aggravation of environmental pollution problems and the improvement of people's health awareness, the demand for efficient gas sensing technology in the fields of air quality monitoring, industrial safety, and medical health has been increasing. Gas-sensitive semiconductor materials are widely used due to their high sensitivity to specific gases. Among them, metal oxide semiconductor materials (such as SnO2, ZnO, WO3, etc.) occupy an important position in the field of gas sensors by virtue of their good stability and adjustable gas-sensitive characteristics. However, existing gas-sensitive materials still have obvious limitations in low-concentration target gas detection, response speed, humidity interference, etc., and there is an urgent need to develop new high-performance gas-sensitive materials to meet the actual application requirements.

[0003] Formaldehyde is a colorless and highly irritating toxic gas, which is listed as a Class I carcinogen by the World Health Organization (WHO). Long-term exposure can cause respiratory diseases, immune system damage, and is closely related to the occurrence of major diseases such as leukemia. Formaldehyde mainly comes from indoor decoration materials, furniture, adhesives, textiles, etc., and has the characteristics of a long release period and difficulty in complete removal, resulting in a very serious problem of indoor air pollution. According to investigations, in newly decorated residential and office premises in China, the proportion of formaldehyde concentration exceeding the standard is as high as 60% - 94%, and its average concentration often far exceeds the national standard (0.08mg / m 3 ), posing a long-term threat to human health. Therefore, developing a formaldehyde sensor with high sensitivity, low detection limit, and real-time response is of great significance for protecting public health and improving the living environment.

[0004] At present, the detection techniques for formaldehyde mainly include chemical analysis methods and physical sensing methods. Chemical analysis methods (such as phenol reagent colorimetry, acetylacetone method, etc.) usually require cumbersome pretreatment steps and rely on specific reagents for color reaction, making it difficult to achieve real-time on-line detection. Physical sensing methods (such as gas chromatography, spectroscopy, electrochemical sensing method, etc.) have high sensitivity and accuracy, but the instrument equipment is expensive and the operation is complex, which is not suitable for large-scale popularization. In contrast, metal oxide semiconductor gas sensors have received extensive attention in the field of formaldehyde detection due to their advantages such as low cost, easy preparation, and integratability. However, the current mainstream metal oxide sensors still face technical bottlenecks such as high detection limit (>1 ppm), sensitivity to humidity changes, and slow response and recovery speed. In addition, most semiconductor gas sensing materials need to work at high temperatures (260°C - 300°C), which not only increases power consumption but also poses safety hazards. Therefore, finding new materials that can achieve high-sensitivity formaldehyde detection at lower temperatures is the key research direction of current gas sensing technology.

[0005] Titanate materials have shown broad application prospects in the fields of energy storage, catalysis, sensing, etc. due to their unique layered structure and chemical stability. Sodium titanate (Na2Ti3O7), as a typical layered titanate, has good structural controllability and adjustable electronic properties, and can theoretically be used for the development of high-performance gas sensing materials. However, its intrinsic conductivity is low and the surface active sites are limited, resulting in limited performance in gas sensing applications. Therefore, we considered converting sodium titanate into hydrogenated titanium oxide (H-NTO) by ion exchange to improve its conductivity and surface activity. However, the ordinary acid treatment method is prone to cause the collapse of the layered structure, resulting in a decrease in the stability of the nanosheets and being unfavorable for maintaining the sensing performance. Therefore, how to improve the conductivity and gas sensing activity of H-NTO while maintaining the integrity of the layered structure has become the key challenge to enhance its formaldehyde sensing performance. Summary of the Invention

[0006] The present invention provides a controllable method for realizing the conversion of sodium titanate to sodium hydrogen titanate through ion exchange, which solves the problems of low sensitivity and complex manufacturing process of existing gas sensing materials for detecting formaldehyde. By precisely controlling the ion exchange process, it is ensured that while the structure of the material is stable, its electrochemical activity and specific surface area are improved, thereby enhancing the adsorption and reaction ability to formaldehyde molecules. Compared with traditional metal oxide sensing materials, the H-NTO sensor prepared by this method can achieve high sensitivity, low detection limit, fast response, and good anti-humidity interference ability at room temperature, providing a new solution for the research and development of a new generation of high-performance formaldehyde sensors.

[0007] The preparation method of a titanate sensing material regulated by a proton conduction mode according to the present invention includes the following steps:

[0008] (1) Add anatase titanium dioxide powder with a particle size of 200 nm to 300 nm to a NaOH solution with a concentration of 10 mol / L to 12 mol / L. For every 0.1 g of titanium dioxide powder, 15 ml of NaOH solution is used. Stir at 500 rpm for 3 min to 5 min to obtain an alkaline dispersion of titanium dioxide. Hydrothermally react the alkaline dispersion at 140 °C to 180 °C for 18 h to 36 h. After cooling, perform solid-liquid separation to obtain nanoscale sodium titanate;

[0009] (2) Immerse the nanoscale sodium titanate obtained in step (1) into a HCl solution with a concentration of 10 -4 mol / L to 10 -2 mol / L. Soak for 3 min to 5 min, and after solid-liquid separation, obtain nanoscale protonated sodium titanate, which is the titanate sensing material with regulated proton conduction mode;

[0010] After washing the sodium titanate obtained in step (1) with 100% deionized water, immerse it into the HCl solution;

[0011] The concentration of the HCl solution described in step (2) is preferably 10 -3 mol / L;

[0012] After vacuum drying the protonated sodium titanate obtained in step (2) at 60 °C, a white powder is obtained, which is the titanate sensing material with regulated proton conduction mode.

[0013] The protonated sodium titanate obtained by the above method has a nanoscale layered structure, and its chemical formula is H x Ti3O7·nH2O (0.8 ≤ x ≤ 1.2, 0 ≤ n ≤ 2), and the layer spacing is 0.79 ± 0.03 nm.

[0014] The protonated sodium titanate can be used as a sensing material to prepare a formaldehyde sensor. The preparation method is as follows: Mix the protonated sodium titanate with an appropriate amount of ethanol and ultrasonically treat it for 30 seconds to ensure full fusion of the two to form a uniform viscous slurry; accurately drop this slurry onto the surface of a clean interdigital electrode and naturally dry and cure it in the air to prepare the formaldehyde sensor.

[0015] This formaldehyde sensor can be used for the detection of formaldehyde gas in the environment and the early diagnosis of breast cancer.

[0016] The present invention has the following beneficial effects:

[0017] In the present invention, H + is used to replace Na +Counter ions are used to construct an H-Ti-O nanostructure rich in surface hydroxyl groups, and the crystal structure and electrochemical properties of H-NTO can be precisely controlled. The prepared protonated sodium titanate material has unique structural and surface characteristics, enabling it to exhibit ultra-high sensitivity at the ppb level and excellent anti-interference performance towards formaldehyde, with a significantly improved response speed compared to traditional materials.

[0018] The formaldehyde gas sensor element prepared with protonated sodium titanate shows faster response speed, higher sensitivity, wider detection range, and more excellent long-term stability in performance compared to existing semiconductor formaldehyde sensors. In addition, this gas sensor element has strong adaptability to environmental humidity and can maintain reliable detection performance in complex environments. Its preparation process is simple, with low cost and small device volume, facilitating integration and mass production. It is particularly suitable for high-precision formaldehyde quantitative detection and the development of portable sensing devices, and can be widely applied in the fields of environmental monitoring and medical diagnosis. Description of the Drawings

[0019] Figure 1 It is the XPS diagram of the H-Ti-O nanobelt of the sensing material; among them, H-NTO represents the sensing material prepared in Example 2, and NTO represents the sensing material prepared in Comparative Example 2.

[0020] Figure 2 It is the infrared spectrum of the sensing materials prepared in Examples 1-3 and Comparative Examples 1-2, showing the characteristic adsorption peak diagram of formaldehyde at the -OH site.

[0021] Figure 3 It is the comparative curve graph of the response performance of the sensors prepared in Examples 1-3 and Comparative Examples 1-2 towards formaldehyde.

[0022] Figure 4 It is the comparison graph of the response value and response time of the sensors prepared in Examples 1-3 and Comparative Examples 1-2 towards formaldehyde.

[0023] Figure 5 It is the microscopic morphology diagram of the sensing material; among them, A represents NTO of Comparative Example 2, B represents H-NTO C-3 of Example 2, and C represents H-NTO C-1 of Comparative Example 1.

[0024] Figure 6 It is the response situation diagram of the sensor prepared in Example 2 towards 1 ppm formaldehyde under different humidity (RH) conditions at 20°C.

[0025] Figure 7 It is the internal circuit diagram of the sensor prepared by the present invention for formaldehyde detection.

[0026] Figure 8 It is the schematic diagram of the circuit board of the sensor prepared by the present invention for formaldehyde detection; among them, (a) is the front side of the circuit board, and (b) is the back side of the circuit board.

[0027] Figure 9 It is the influence of different ventilation times on the formaldehyde content in the environment.

[0028] Figure 10 It is the response of the sensor prepared in Example 2 in different respiratory samples. Detailed implementation manners

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings. It should be noted that the embodiments described in the present invention are only used for further explanation and illustration, rather than limiting its application scope. Based on the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

[0030] Example 1

[0031] (1) 0.1 g of titanium dioxide powder (CAS: 1317700, anatase type, particle size 200 nm - 300 nm) was added to 15 mL of NaOH solution with a concentration of 10 mol / L, and stirred at 500 rpm for 5 min to obtain an alkaline dispersion of titanium dioxide; the alkaline dispersion was placed in a 20 ml tetrafluoroethylene autoclave and subjected to hydrothermal reaction at 140 °C for 36 h. After cooling, solid-liquid separation was carried out to obtain a white precipitate product; the obtained white precipitate product was washed with 100% deionized water to obtain nanoscale sodium titanate.

[0032] (2) The obtained sodium titanate was immersed in 10 -4 mol / L HCl solution for 3 min. After solid-liquid separation, a white product was obtained, and after vacuum drying at 60 °C, a white powder of nanoscale protonated sodium titanate, that is, a titanate sensing material with regulated proton conduction mode, was obtained, denoted as H-NTO C-4.

[0033] The above protonated sodium titanate was used to prepare a formaldehyde sensor, and the preparation method was as follows:

[0034] H-NTO C-4 was mixed with an appropriate amount of ethanol and ultrasonically treated with an ultrasonic cleaner for 30 seconds to ensure full fusion of the two to form a uniform viscous slurry. This slurry was precisely drop-coated on the surface of a clean interdigital electrode and naturally dried and cured in the air to obtain the formaldehyde sensor.

[0035] Example 2

[0036] (1) Add 0.1 g of titanium dioxide powder (CAS: 1317700, anatase type, particle size 200 nm - 300 nm) to 15 mL of NaOH solution with a concentration of 10 mol / L, stir ultrasonically at 500 rpm for 5 min to obtain an alkaline dispersion of titanium dioxide; place the alkaline dispersion in a 20 ml tetrafluoroethylene autoclave and carry out hydrothermal reaction at 140 °C for 36 h. After cooling, perform solid-liquid separation to obtain a white precipitate product; wash the obtained white precipitate product with 100% deionized water to obtain nanoscale sodium titanate;

[0037] (2) Immerse the obtained sodium titanate in 10 -3 mol / L HCl solution, soak for 3 min, perform solid-liquid separation to obtain a white product, and obtain a white powder of nanoscale protonated sodium titanate after vacuum drying at 60 °C, which is the titanate sensing material with proton conduction mode regulation, denoted as H-NTO C-3.

[0038] Use the above-mentioned protonated sodium titanate to prepare a formaldehyde sensor, and the preparation method is as follows:

[0039] Mix H-NTO C-3 with an appropriate amount of ethanol, and ultrasonically treat it with an ultrasonic cleaner for 30 seconds to ensure full fusion of the two to form a uniform viscous slurry. Drop this slurry precisely onto the surface of a clean interdigital electrode and air-dry and cure it naturally to obtain the formaldehyde sensor.

[0040] Figure 1 It can be seen that Na in the sensing material H-NTO C-3 + is completely removed. The microscopic morphology of H-NTO C-3 is as Figure 5 shown in B. After the sodium titanate is treated with 10 -3 mol / L HCl, the nanosheets roll into nanotubes, the surface area increases, and it is more conducive to the adsorption of formaldehyde gas. The response of the prepared sensor to 1 ppm formaldehyde under different humidity conditions at 20 °C is as Figure 6 shown.

[0041] Example 3

[0042] (1) Add 0.1 g of titanium dioxide powder (CAS: 1317700, anatase type, particle size 200 nm - 300 nm) to 15 mL of NaOH solution with a concentration of 10 mol / L, stir ultrasonically at 500 rpm for 3 min to obtain an alkaline dispersion of titanium dioxide; place the alkaline dispersion in a 20 ml tetrafluoroethylene autoclave and carry out hydrothermal reaction at 140 °C for 18 h. After cooling, perform solid-liquid separation to obtain a white precipitate product; wash the obtained white precipitate product with 100% deionized water to obtain nanoscale sodium titanate;

[0043] (2) Immerse the obtained sodium titanate in 10 -2In an HCl solution with a concentration of [[mol / L]], soak for 3 min. After solid-liquid separation, a white product is obtained. After vacuum drying at 60 °C, a white powder of nanoscale protonated sodium titanate, namely the titanate sensing material with regulated proton conduction mode, is denoted as H-NTO C-2.

[0044] Use the above-mentioned protonated sodium titanate to prepare a formaldehyde sensor. The preparation method is as follows:

[0045] Mix H-NTO C-2 with an appropriate amount of ethanol and ultrasonically treat it with an ultrasonic cleaner for 30 seconds to ensure full fusion of the two and form a uniform viscous slurry. Drop this slurry precisely onto the surface of a clean interdigital electrode and naturally dry and cure it in the air to obtain the formaldehyde sensor.

[0046] Comparative Example 1

[0047] (1) Add 0.1 g of titanium dioxide powder (CAS: 1317700, anatase type, particle size 200 nm - 300 nm) to 15 mL of a NaOH solution with a concentration of 10 [[mol / L]], and ultrasonically stir at 500 rpm for 5 min to obtain an alkaline dispersion of titanium dioxide. Place the alkaline dispersion in a 20 ml tetrafluoroethylene autoclave and carry out a hydrothermal reaction at 140 °C for 36 h. After cooling, perform solid-liquid separation to obtain a white precipitate product. Wash the obtained white precipitate product with 100% deionized water to obtain nanoscale sodium titanate;

[0048] (2) Immerse the obtained sodium titanate in 10 -1 mol / L HCl solution, soak for 3 min. After solid-liquid separation, a white product is obtained. After vacuum drying at 60 °C, a white powder of nanoscale protonated sodium titanate, namely the titanate sensing material with regulated proton conduction mode, is denoted as H-NTO C-1. The microscopic morphology is as Figure 5 shown in C.

[0049] Use the above-mentioned protonated sodium titanate to prepare a formaldehyde sensor. The preparation method is as follows:

[0050] Mix H-NTO C-1 with an appropriate amount of ethanol and ultrasonically treat it with an ultrasonic cleaner for 30 seconds to ensure full fusion of the two and form a uniform viscous slurry. Drop this slurry precisely onto the surface of a clean interdigital electrode and naturally dry and cure it in the air to obtain the formaldehyde sensor.

[0051] Comparative Example 2

[0052] (1) Add 0.1 g of titanium dioxide powder (CAS: 1317700, anatase type, particle size 200 nm - 300 nm) to 15 mL of NaOH solution with a concentration of 10 mol / L, stir at 500 rpm for 5 min to obtain an alkaline dispersion of titanium dioxide; place the alkaline dispersion in a 20 ml tetrafluoroethylene high-pressure reaction kettle and carry out hydrothermal reaction at 140 °C for 36 h. After cooling, perform solid-liquid separation to obtain a white precipitate product; wash the obtained white precipitate product with 100% deionized water and vacuum dry at 60 °C to obtain nanoscale sodium titanate, denoted as NTO. The microscopic morphology is as Figure 5 shown in A.

[0053] (2) No treatment with HCl solution.

[0054] Use the above sodium titanate to prepare a formaldehyde sensor, and the preparation method is as follows:

[0055] Mix NTO with an appropriate amount of ethanol and ultrasonically treat it with an ultrasonic cleaner for 30 seconds to ensure full fusion of the two to form a uniform viscous slurry. Drop this slurry precisely onto the surface of a clean interdigital electrode and naturally dry and cure it in the air to obtain the formaldehyde sensor described.

[0056] Comparative Example 3

[0057] (1) Add 0.1 g of titanium dioxide powder (CAS: 13463677, P25, anatase type, average particle size 25 nm) to 15 mL of NaOH solution with a concentration of 10 mol / L, stir at 500 rpm for 5 min to obtain an alkaline dispersion of titanium dioxide; place the alkaline dispersion in a 20 ml tetrafluoroethylene high-pressure reaction kettle and carry out hydrothermal reaction at 140 °C for 36 h. After cooling, perform solid-liquid separation to obtain a white precipitate product; wash the obtained white precipitate product with 100% deionized water to obtain nanoscale sodium titanate;

[0058] (2) Immerse the obtained sodium titanate in 10 -3 mol / L HCl solution and soak for 3 min. After solid-liquid separation, obtain a white product and vacuum dry at 60 °C to obtain a nanoscale protonated sodium titanate white powder, that is, a titanate sensing material with proton conduction mode regulation, denoted as H-NTO C-31.

[0059] Use the above protonated sodium titanate to prepare a formaldehyde sensor, and the preparation method is as follows:

[0060] Mix H-NTO C-31 with an appropriate amount of ethanol and ultrasonically treat it with an ultrasonic cleaner for 30 seconds to ensure full fusion of the two to form a uniform viscous slurry. Drop this slurry precisely onto the surface of a clean interdigital electrode and naturally dry and cure it in the air to obtain the formaldehyde sensor described.

[0061] Comparative Example 4

[0062] (1) Add 0.1 g of titanium dioxide powder (CAS: 1317700, anatase type, particle size 200 nm - 300 nm) to 15 mL of a 1 mol / L NaOH solution, stir at 500 rpm for 5 min to obtain an alkaline dispersion of titanium dioxide; place the alkaline dispersion in a 20 ml tetrafluoroethylene autoclave and carry out a hydrothermal reaction at 140 °C for 36 h. After cooling, perform solid-liquid separation to obtain a white precipitate product; wash the obtained white precipitate product with 100% deionized water to obtain nanoscale sodium titanate;

[0063] (2) Immerse the obtained sodium titanate in a 10 -3 mol / L HCl solution, soak for 30 min, then ultrasonicate for 3 min. After solid-liquid separation, a white product is obtained. After vacuum drying at 60 °C, a nanoscale protonated sodium titanate white powder, i.e., a titanate sensing material with regulated proton conduction mode, is obtained, denoted as H-NTO C-32.

[0064] Use the above-mentioned protonated sodium titanate to prepare a formaldehyde sensor, and the preparation method is as follows:

[0065] Mix H-NTO C-32 with an appropriate amount of ethanol and ultrasonically treat it with an ultrasonic cleaner for 30 seconds to ensure full fusion of the two to form a uniform viscous slurry. Drop this slurry precisely onto the surface of a clean interdigital electrode and air-dry and cure it naturally to obtain the formaldehyde sensor.

[0066] Comparative Example 5

[0067] (1) Add 0.1 g of titanium dioxide powder (CAS: 1317700, anatase type, particle size 200 nm - 300 nm) to 15 mL of a 10 mol / L NaOH solution, stir at 500 rpm for 5 min to obtain an alkaline dispersion of titanium dioxide; place the alkaline dispersion in a 20 ml tetrafluoroethylene autoclave and carry out a hydrothermal reaction at 140 °C for 36 h. After cooling, perform solid-liquid separation to obtain a white precipitate product; wash the obtained white precipitate product with 100% deionized water to obtain nanoscale sodium titanate;

[0068] (2) Immerse the obtained sodium titanate in a 10 -3 mol / L HCl solution, stir for 1 h. After solid-liquid separation, a white product is obtained. After vacuum drying at 100 °C, a nanoscale protonated sodium titanate white powder, i.e., a titanate sensing material with regulated proton conduction mode, is obtained, denoted as H-NTO C-33.

[0069] Use the above-mentioned protonated sodium titanate to prepare a formaldehyde sensor, and the preparation method is as follows:

[0070] Mix H-NTO C-33 with an appropriate amount of ethanol and ultrasonically treat it for 30 seconds using an ultrasonic cleaner to ensure full fusion of the two and form a uniform viscous slurry. Drop this slurry precisely onto the surface of a clean interdigital electrode and allow it to dry and cure naturally in air to obtain the formaldehyde sensor described above.

[0071] Detect the performance of the formaldehyde sensors prepared in the above examples and comparative examples. The internal circuit of the sensor when used for formaldehyde detection is as Figure 7 shown. Integrate the test core device on a circuit board of 5 cm × 5 cm, ensuring the miniaturization of the test device while maintaining the test accuracy. The circuit board of the sensor when used for formaldehyde detection is as Figure 8 shown. Figure 8 (a) is the front side of the circuit board, Figure 8 (b) is the back side of the circuit board. It can be seen from Figure 2 that the characteristic adsorption peak of each sensing material for formaldehyde at the -OH site is at 3369 cm-1. The response performance of the sensors prepared in Examples 1-3 and Comparative Examples 1-2 to formaldehyde is as Figure 3 shown (covering the concentration range of 2 ppb to 100000 ppb), and the comparison of the response value and response time is as Figure 4 shown. The detection results of the sensors prepared in each example and comparative example for formaldehyde are shown in Table 1. The temperature during the test is 20 °C and the humidity is 30%.

[0072] Table 1 Detection results of the sensors prepared in each example and comparative example for formaldehyde

[0073]

[0074] As can be seen from Table 1, the protonated sodium titanate prepared by the present invention used as a formaldehyde sensor has the advantages of high sensitivity, fast response, low detection limit, and wide measurement range. The sensing material in Comparative Example 1 is 10 -1The samples were soaked in HCl acid with a concentration of [[mol / L]] for 3 min. An excessively high acid concentration caused the collapse of the interlayer structure of sodium titanate, resulting in structural damage and a very small response value to formaldehyde. The sensing material in Comparative Example 2 was the original sodium titanate without being treated with HCl solution, without protonation exchange, and had a relatively small response value to formaldehyde. The titanium dioxide powder used as the sensing material in Comparative Example 3 was P25. Since the average particle size of P25 titanium dioxide was 25 nm and the layered structure was not obvious, the protonation exchange process failed and there was almost no response to formaldehyde. The NaOH solution with a concentration of 1 [[mol / L]] was used for hydrothermal synthesis of the sensing material in Comparative Example 4. The NaOH concentration was too low, which was not conducive to the construction of a two-dimensional layered structure. The method of protonation exchange for the sensing material in Comparative Example 5 was vacuum drying at 100 °C after stirring in the acid solution for 1 h. Since the protonation exchange process occurred very rapidly, stirring or soaking for too long would damage the original structure; there were a large number of hydroxyl groups on the surface during the protonation process, and vacuum drying at 100 °C would remove the original bonded hydroxyl groups, reducing the specific adsorption sites and being unfavorable for formaldehyde adsorption.

[0075] To further explore the response of the sensor to formaldehyde, the response of the sensor prepared from the sensing material H-NTO C-3 of Example 2 to 1 ppm HCHO was tested under different temperature and humidity conditions. The results are shown in Tables 2 and 3.

[0076] Table 2 Response of the sensor to 1 ppm formaldehyde at different temperatures with a humidity of 30%

[0077]

[0078]

[0079] Table 3 Response of the sensor to 1 ppm formaldehyde at different humidities at 20 °C

[0080] Humidity (%) Response value (Rg / Ra - 1) Response time (s) 20 15.2749 76 30 8.34991 71 40 7.43307 75.69 50 5.47568 83.875 60 4.75238 89.5 80 4.75238 113.51

[0081] To evaluate the practical application potential of the protonated sodium titanate (H-NTO) sensor, the sensing material prepared in Example 2 was integrated onto a 5 cm × 5 cm printed circuit board (PCB), as Figure 8 shown, thus constructing a wireless intelligent detection system. This system used a resistive H-NTO sensor as the core sensing element and was wirelessly connected to a mobile intelligent device through a Wi-Fi module. Through a smartphone application, users could monitor and view the formaldehyde response signal in real time.

[0082] To simulate real leakage scenarios, we conducted formaldehyde release experiments in an actual indoor environment. Formaldehyde solutions of different volumes were applied to cotton and then sealed in glass containers to prepare controlled release sources. These containers were placed in different rooms to simulate different exposure levels. When the sensor was close to these release sources, an obvious reaction occurred immediately. Once the detected concentration exceeded the safety threshold of 80 ppb, the connected smartphone would trigger a real-time alarm. In rooms without a formaldehyde source, the readings always remained at the baseline level, which further confirmed the excellent sensitivity of the sensor.

[0083] Subsequently, natural ventilation was adopted to reduce the indoor formaldehyde level, and the concentration was continuously monitored. It took about 4 hours of ventilation to lower the concentration below the safety threshold of 80 ppb (as Figure 9 shown). It is worth noting that even in high-humidity environments such as balconies and bathrooms, the sensor could maintain stable and sensitive performance throughout the experiment, demonstrating good moisture resistance.

[0084] In summary, this experiment comprehensively verified the high sensitivity, fast response, and environmental stability of the H-NTO sensor under realistic conditions, highlighting its practical application potential in the fields of environmental monitoring and indoor air quality assessment.

[0085] In addition to environmental monitoring, this study further explored the application of the H-NTO sensor prepared in Example 2 in non-invasive breath analysis, especially its potential in early disease diagnosis. In the experimental design, we simulated the release of formaldehyde biomarkers in the exhaled breath of breast cancer patients and measured the response of the sensor. First, aluminum foil sampling bags were used to collect exhaled breath samples from 5 healthy subjects (numbered 1, 2, 3, 4, 5) to evaluate the formaldehyde detection ability of the sensor. Subsequently, formaldehyde gas was injected to increase the concentration in the sampling bags to 500 ppb (corresponding to numbers 6, 7, 8, 9, 10) and 1 ppm (corresponding to numbers 11, 12, 13, 14, 15) respectively, simulating the typical exhaled breath environment of breast cancer patients. Compared with the breath samples of healthy people, the response of the sensor to the simulated patient breath samples was significantly higher, as Figure 10 shown, indicating that the response signal of the sensor to the simulated patient breath samples was significantly enhanced, which showed that the sensor could effectively distinguish different health conditions.

[0086] In addition, we also conducted a compositional analysis of the selected test samples. The results showed that there was no overlap between the response data from healthy subjects and simulated patients, and the two groups could be clearly distinguished, with a classification accuracy rate as high as 94.6%.

[0087] To enhance the sensor's recognition ability, we introduced a one-dimensional depth convolutional neural network (1-D CNN) algorithm to analyze the sensor's response patterns and automatically classify different breathing states. In this study, we collected 50 sets of data, including four different breathing states, and normalized the sensor signals using formula S1. Subsequently, we trained and optimized the CNN model to distinguish: (A1) normal breathing of healthy individuals; (A2) mildly abnormal breathing simulating stage I breast cancer patients; (A3) pathological breathing of stage III breast cancer patients (with lymph node metastasis); and (A4) non-cancer respiratory diseases (such as chronic obstructive pulmonary disease, COPD). Confusion matrix analysis showed that the model had extremely high accuracy in classifying different breathing categories, with an average classification accuracy approaching 95%.

[0088] In summary, the sensor can not only quantify the formaldehyde level but also accurately distinguish individuals with different health conditions by combining intelligent algorithms, providing a feasible method for non-invasive disease screening based on breath biomarkers. These results indicate that the developed sensor has great potential in practical formaldehyde detection.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a titanate sensing material with regulated proton conduction mode, characterized in that, It includes the following steps: (1) Add anatase titanium dioxide powder with a particle size of 200 nm to 300 nm into a NaOH solution with a concentration of 10 mol / L to 12 mol / L. For every 0.1 g of titanium dioxide powder, 15 ml of NaOH solution is used to obtain an alkaline dispersion of titanium dioxide. Hydrothermally react the alkaline dispersion at 140 °C to 180 °C for 18 h to 36 h. After cooling, perform solid-liquid separation to obtain nanoscale sodium titanate; (2) Immerse the sodium titanate obtained in step (1) in 10 -4 mol / L to 10 -2 mol / L HCl solution, soak for 3 min to 5 min, and obtain nanoscale protonated sodium titanate after solid-liquid separation, that is, the titanate sensing material with regulated proton conduction mode.

2. The preparation method of a titanate sensing material with regulated proton conduction mode according to claim 1, characterized in that, In step (1), the titanium dioxide powder is added to the NaOH solution and stirred at 500 rpm for 3 min to 5 min to obtain the alkaline dispersion of titanium dioxide. After the nanoscale sodium titanate is washed with 100% deionized water, it is then immersed in an HCl solution.

3. The preparation method of a titanate sensing material with regulated proton conduction mode according to claim 1, characterized in that, The concentration of the HCl solution described in step (2) is 10 -3 mol / L.

4. The preparation method of a titanate sensing material with regulated proton conduction mode according to claim 1, characterized in that, The protonated sodium titanate obtained in step (2) is vacuum-dried at 60 °C to obtain the titanate sensing material with the proton conduction mode regulated.

5. The preparation method of a titanate sensing material with proton conduction mode regulation according to claim 1, characterized in that, The sodium titanate nanotubes described in step (2) are of a nanoscale layered structure, and their chemical formula is H x Ti3O7·nH2O, where 0.8 ≤ x ≤ 1.2, 0 ≤ n ≤ 2, and the interlayer spacing is 0.79 ± 0.03 nm.

6. The protonated sodium titanate obtained by the method according to any one of claims 1 to 5 is used as a sensing material for a formaldehyde sensor.

7. The sensing material for a formaldehyde sensor according to claim 6, characterized in that, The usage method is as follows: Mix the protonated sodium titanate with ethanol and perform ultrasonic treatment to form a uniform viscous slurry. Coat the slurry on the surface of the interdigital electrode, dry and cure it to prepare the formaldehyde sensor.

8. The formaldehyde sensor according to claim 7 is used for the detection of formaldehyde gas in the environment and the early diagnosis of breast cancer.

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