A method for preparing nanorod-shaped B-TiO2 acetone gas-sensitive material

Abstract

This invention discloses a method for preparing a nanorod-shaped B-TiO2 acetone gas-sensitive material, belonging to the field of semiconductor gas sensing technology. The invention first prepares TiO2 nanorods via a hydrothermal method, then reduces them with NaBH4 to obtain B-TiO2 nanorods. A ZIF-8 coating layer is then grown in situ on the nanorod surface, followed by annealing to obtain a B-TiO2@ZIF-8 composite material. This method is simple, operates under mild conditions, and does not require high-temperature hydrogen reduction. The resulting material exhibits a response of 13.0 to 20 ppm acetone at room temperature, with response / recovery times as low as 3.9 s and 5.2 s, respectively. Especially under high humidity (90% RH), the response value decreases by only 14.6%, far superior to pure B-TiO2 (which decreases by 55%). The material of this invention effectively resists interference from high humidity environments, and its response to acetone in human exhaled breath is highly synchronized with changes in blood glucose levels, showing broad application prospects in the field of non-invasive blood glucose detection.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor gas sensing technology, specifically relating to a method for preparing ZIF-8 coated nanorod-shaped B-TiO2 acetone gas-sensitive material. Background Technology

[0002] Acetone is a typical volatile organic compound (VOC) widely present in industrial production, environmental monitoring, and chemical testing. Rapid, accurate, and stable detection of acetone gas is of significant application value. Acetone is a characteristic biomarker of human blood glucose metabolism; the concentration of acetone in exhaled breath is directly related to blood glucose levels. Non-invasive blood glucose detection based on acetone sensing offers advantages such as being non-invasive, convenient, and rapid.

[0003] Common metal oxide semiconductor materials (such as TiO2) are the mainstream materials for acetone gas sensing, possessing advantages such as fast response, simple preparation, and low cost. Kong et al. prepared tungsten-doped titanium dioxide (W-TiO2) through a two-step method of ion exchange and high-temperature calcination (KONG L, Li G, WANG H, et al. Highly sensitive acetone sensor based on synergistic effect of anatase / rutile homojunction and heterometaldoping of porous tungsten-doped TiO2 nanocakes derived from bimetallic metal-organic framework[ J]. Sensors and Actuators B: Chemical, 2026, 450:139223.). At the optimal operating temperature of 200℃, the response value for 10 ppm acetone was as high as 12.6, with a detection limit as low as 100 ppb. However, when the ambient humidity increased to 85% RH, the responsivity dropped to 1.35, a decrease of 89.3%. Lv et al. prepared TiO2 / Fe2TiO5@PW12 core-shell structured nanofibers (LV X, JIANGB, GUO Z, et al. Construction and highly acetone detectability via one-dimensional (TiO2 / Fe2TiO5)@polyoxometalates nanofibers gas sensor [J]. Sensors and Actuators B: Chemical, 2026, 451: 139383) using a coaxial electrospinning combined with high-temperature calcination process. The response value to 100 ppm acetone was 6.5 at the optimal operating temperature of 270℃. Regarding humidity sensitivity, the sensor response was significantly affected by humidity, with the best response at 32% relative humidity. The response gradually decreased with increasing humidity, indicating weak overall moisture resistance.

[0004] It is evident that traditional TiO2-based gas-sensitive materials are highly sensitive to environmental humidity. In high-humidity environments above 90% RH, the material surface readily adsorbs a large number of water molecules, occupying gas active sites and causing a significant attenuation and signal distortion in acetone sensing response, failing to meet the acetone detection requirements under high humidity conditions. Existing dehumidification methods easily lead to acetone gas loss and the introduction of interfering impurities, making it difficult to solve the high-humidity interference problem from the material itself. Metal-organic frameworks (MOFs) possess advantages such as large specific surface area, controllable pore size, and hydrophobic selectivity, and can be used as a coating layer for gas-sensitive materials to achieve water molecule blocking and selective enrichment of target gases. ZIF-8, as a typical MOF material, possesses excellent hydrophobic properties and molecular sieving effects, making it an ideal component for modifying TiO2-based gas-sensitive materials and improving acetone sensing performance under high humidity. Summary of the Invention

[0005] To address the shortcomings of traditional B-TiO2 gas-sensitive materials, such as poor acetone sensing performance, weak resistance to humidity interference, and insufficient detection stability under high humidity conditions, this invention provides a ZIF-8-coated nanorod-shaped B-TiO2 acetone gas-sensitive material, along with a simple, mild, and scalable preparation method, and the application of this material in acetone gas detection under high humidity conditions.

[0006] This invention is achieved through the following technical solution. The preparation method of a nanorod-shaped B-TiO2 acetone gas-sensitive material according to this invention includes the following steps:

[0007] (1) Preparation of TiO2 nanorods: Prepare a 15-25% NaOH solution, stir magnetically until completely dissolved, and allow to cool to room temperature. Mix tetrabutyl titanate and anhydrous ethanol at a volume ratio of 3:20 and stir vigorously to obtain a homogeneous tetrabutyl titanate-ethanol mixture. Add the tetrabutyl titanate-ethanol mixture dropwise to the above sodium hydroxide solution and stir continuously magnetically to obtain a milky white uniform suspension. Transfer the obtained suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven. Heat to 120-180℃ and react at a constant temperature for 24 h. After the reaction is completed, allow it to cool naturally to room temperature, remove the suspension from the reactor, place it in a centrifuge tube, and collect the lower white solid precipitate. Wash the precipitate twice each with dilute hydrochloric acid, anhydrous ethanol, and deionized water to neutralize residual sodium hydroxide and remove surface impurities. Transfer the washed solid to a drying oven and dry at a constant temperature of 60℃ to obtain TiO2 nanorods.

[0008] (2) Preparation of B-TiO2 nanorods: The TiO2 nanorods prepared in step (1) were mixed with NaBH4 at a mass ratio of 2:1-1:2 and continuously ground until the mixture presented a uniform and fine grayish-white powder with no obvious particle agglomeration. Then, thermal reduction was carried out under argon protection at a temperature of 300-400℃. After holding at this temperature for 1 h, the mixture was naturally cooled to room temperature to obtain a black powder. The product was then washed twice with ultrapure water and anhydrous ethanol to remove impurities and unreacted NaBH4. After centrifugation, the solution was placed in a drying oven and dried at 60℃ for 4 hours to obtain B-TiO2 nanorods.

[0009] (3) Preparation of B-TiO2@ZIF-8: 20 mL of methanol was added to a beaker, and 0.1-0.25 g of Zn(NO3)2·6H2O and 2.7 g of B-TiO2 nanorods were weighed and added to it. The mixture was magnetically stirred until completely dissolved. Separately, 0.43-1.08 g of 2-methylimidazole was weighed and added to 20 mL of methanol. The mixture was magnetically stirred for 5 minutes until completely dissolved, resulting in a colorless and transparent methanol solution of the ligand. The two solutions were mixed and magnetically stirred for 30 minutes, and the solution quickly turned into a milky white suspension. The mixture was then transferred to a polytetrafluoroethylene reactor, sealed, and placed in an oven at 120-150℃ for 12-24 hours. After the reaction was completed and the solution cooled, the precipitate at the bottom was collected. The collected precipitate was transferred to a centrifuge tube and washed successively with anhydrous ethanol and deionized water. After drying, the ZIF-8-coated nanorod-shaped B-TiO2 gas-sensitive material was obtained.

[0010] (4) Annealing treatment: The B-TiO2@ZIF-8 prepared in step (3) is annealed under an argon atmosphere at a temperature of 200℃ for 6 h.

[0011] Preferably, the concentration of the NaOH solution in step (1) is 20%.

[0012] Preferably, the mass ratio of TiO2 nanorods to sodium borohydride in step (2) is 2:1.

[0013] Preferably, the heating rate of the tubular furnace in step (2) is 8 to 10 °C / min.

[0014] Preferably, the heat reduction temperature in step (2) is 350°C and the heat preservation time is 1 h.

[0015] Preferably, the reaction temperature in step (3) is 150°C.

[0016] Preferably, the amount of Zn(NO3)2·6H2O added in step (3) is 0.2 g, and the amount of 2-methylimidazole added is 0.87 g.

[0017] Preferably, the reaction temperature in step (3) is 120°C and the reaction time is 24 h.

[0018] Principle of this invention:

[0019] The preparation of nanorod-shaped TiO2 is achieved by using NaOH to provide an alkaline guiding environment that drives the preferential growth of crystals along a specific crystal orientation. Specifically, in a high-concentration NaOH environment, a large amount of OH- is provided. - The OH⁻ reacts with titanium oxyhydroxyl groups to form titanate intermediates. Under hydrothermal conditions, OH⁻ selectively adsorbs on the transverse crystal planes of the titanate, inhibiting its transverse growth. Simultaneously, the strong interaction of intralayer / intrachain Ti-O covalent bonds drives the preferential growth of the crystal along the longitudinal crystal direction, gradually forming a one-dimensional rod-like structure.

[0020] Furthermore, this invention utilizes NaBH4, a highly reducing agent, to perform surface reduction and oxygen vacancy construction on TiO2, achieving TiO2 reduction at a relatively low temperature of 350°C and within a short time of 1 hour. This is due to the extremely strong reducing properties of NaH, the product of NaBH4's thermal decomposition, which may react with oxygen atoms in the TiO2 lattice, abstracting lattice oxygen and forming stable oxygen-containing compounds, thereby leaving oxygen vacancies in TiO2 and generating B-TiO2. Compared to pure TiO2, B-TiO2 has a smaller band gap and a higher carrier concentration, resulting in more electron excitation upon contact with the target gas, generating more free electrons on the surface to participate in the gas-sensing reaction. Therefore, B-TiO2 exhibits superior sensing performance for acetone compared to traditional TiO2.

[0021] On the other hand, the moisture resistance of B-TiO2@ZIF-8 is significantly improved after ZIF-8 coating. For B-TiO2, due to its hydrophilic surface, water vapor competes with acetone for active sites, affecting its specific response to acetone. Furthermore, B-TiO2's high responsiveness to water molecules significantly reduces its baseline resistance, weakening the resistance reduction caused by acetone molecules. The hydrophobic organic groups in the ZIF-8 ligand give the ZIF-8 surface and pores an overall hydrophobic character, resulting in extremely weak interaction with polar water molecules. This not only makes it difficult to chemically adsorb water molecules but also significantly inhibits the physical adsorption and spreading of water molecules on the material surface. Therefore, the ZIF-8 coating layer on the B-TiO2@ZIF-8 surface, through its hydrophobicity and structural selectivity, blocks the adsorption of water molecules, allowing only acetone molecules to contact the B-TiO2 matrix. This avoids the influence of interfering substances under high humidity conditions, ensuring a targeted response to acetone.

[0022] The beneficial effects of this invention are:

[0023] (1) The B-TiO2 preparation method used in this invention does not require high temperature and hydrogen, has low risk, and is suitable for large-scale production.

[0024] (2) This invention does not use chemical reagents that are difficult to degrade or environmentally unfriendly, and will not have a negative impact on the environment.

[0025] (3) The B-TiO2@ZIF-8 prepared in this invention has a responsiveness of 13.0 to 20 ppm acetone at room temperature, and the response / recovery time is as low as 3.9 s and 5.2 s, respectively.

[0026] (4) The B-TiO2@ZIF-8 structure prepared in this invention can achieve a rapid response to low concentrations of acetone under high humidity, which is suitable for the high humidity environment of human exhalation and can be used for non-invasive blood glucose detection. Attached Figure Description

[0027] Figure 1 The images show scanning electron microscope (SEM) images of the B-TiO2 nanorods prepared in Comparative Example 2 and the B-TiO2@ZIF-8 nanorods prepared in Examples 1, 3, and 4. (a) is the SEM image of the B-TiO2 nanorods; (b) is the SEM image of the B-TiO2 nanorods coated with 1% ZIF-8; (c) is the SEM image of the B-TiO2 nanorods coated with 2% ZIF-8; and (d) is the SEM image of the B-TiO2 nanorods coated with 2.5% ZIF-8.

[0028] Figure 2 X-ray diffraction patterns of B-TiO2 nanorods prepared in Comparative Example 2, pure ZIF-8 prepared in Comparative Example 3, and B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4.

[0029] Figure 3 The reference resistance and response value to 20 ppm acetone are for the TiO2 nanorods prepared in Comparative Example 1, the B-TiO2 nanorods prepared in Comparative Example 2, the pure ZIF-8 prepared in Comparative Example 3, and the B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4.

[0030] Figure 4This section compares the response values ​​of TiO2 nanorods prepared in Comparative Example 1, B-TiO2 nanorods prepared in Comparative Example 2, pure ZIF-8 prepared in Comparative Example 3, and B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4 to different concentrations of acetone. Specifically, (a) shows the response values ​​of B-TiO2 to different concentrations of acetone with ZIF-8 coating amounts ranging from 1% to 2.5%; (b) shows the response values ​​of pure ZIF-8, TiO2, B-TiO2, and B-TiO2@2% ZIF-8 to different concentrations of acetone.

[0031] Figure 5 The response values ​​of TiO2 nanorods prepared in Comparative Example 1, pure ZIF-8 prepared in Comparative Example 3, and B-TiO2@ZIF-8 prepared in Example 3 to different types of gases are compared.

[0032] Figure 6 The response values ​​of TiO2 nanorods prepared in Comparative Example 1, B-TiO2 nanorods prepared in Comparative Example 2, and B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4 to 20 ppm acetone were compared under dry (50% RH) and humid (90% RH) conditions.

[0033] Figure 7 This is a comparison of the human body's expiratory response and blood glucose levels measured by a blood glucose meter over a day using B-TiO2@ZIF-8 prepared in Example 3. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] Add 20 mL of methanol to a beaker, then weigh 0.1 g of Zn(NO3)2·6H2O and 2.7 g of B-TiO2 nanorods prepared in step (2) and add them to the beaker. Stir magnetically for 10 minutes until completely dissolved. Separately weigh 0.43 g of 2-methylimidazole and add it to 20 mL of methanol. Stir magnetically for 5 minutes until completely dissolved to obtain a colorless and transparent ligand methanol solution. Mix the two solutions and stir magnetically for 30 minutes. The solution quickly turns into a milky white suspension. Then transfer the mixture to a polytetrafluoroethylene reactor, seal it, and place it in an oven at 120℃ for 24 hours. After the reaction is complete and the solution has cooled, collect the precipitate at the bottom. Transfer the collected precipitate to a centrifuge tube and wash it sequentially with anhydrous ethanol and deionized water. After drying, the product is B-TiO2@1% ZIF-8.

[0037] B-TiO2@1% ZIF-8 powder was dispersed in anhydrous ethanol and continuously ground until it became a highly viscous viscous substance. It was then coated onto interdigitated electrodes and subjected to a 30-hour aging treatment. The response of the powder to acetone and humidity was then tested at room temperature using a gas-sensitive testing system.

[0038] Example 2

[0039] Add 20 mL of methanol to a beaker, then weigh 0.15 g of Zn(NO3)2·6H2O and 2.7 g of B-TiO2 nanorods prepared in step (2) and add them to the beaker. Stir magnetically for 10 minutes until completely dissolved. Separately weigh 0.65 g of 2-methylimidazole and add it to 20 mL of methanol. Stir magnetically for 5 minutes until completely dissolved to obtain a colorless and transparent ligand methanol solution. Mix the two solutions and stir magnetically for 30 minutes. The solution quickly turns into a milky white suspension. Then transfer the mixture to a polytetrafluoroethylene reactor, seal it, and place it in an oven at 120℃ for 24 hours. After the reaction is complete and the solution has cooled, collect the precipitate at the bottom. Transfer the collected precipitate to a centrifuge tube and wash it sequentially with anhydrous ethanol and deionized water. After drying, the product is obtained as B-TiO2@1.5% ZIF-8.

[0040] B-TiO2@1.5% ZIF-8 powder was dispersed in anhydrous ethanol and continuously ground until it became a highly viscous viscous substance. It was then coated onto interdigitated electrodes and subjected to a 30-hour aging treatment. The response of the electrodes to acetone and humidity was tested at room temperature using a gas-sensitive testing system.

[0041] Example 3

[0042] Add 20 mL of methanol to a beaker, then weigh 0.2 g of Zn(NO3)2·6H2O and 2.7 g of B-TiO2 nanorods prepared in step (2) and add them to the beaker. Stir magnetically for 10 minutes until completely dissolved. Separately weigh 0.87 g of 2-methylimidazole and add it to 20 mL of methanol. Stir magnetically for 5 minutes until completely dissolved to obtain a colorless and transparent ligand methanol solution. Mix the two solutions and stir magnetically for 30 minutes. The solution quickly turns into a milky white suspension. Then transfer the mixture to a polytetrafluoroethylene reactor, seal it, and place it in an oven at 120℃ for 24 hours. After the reaction is complete and the solution has cooled, collect the precipitate at the bottom. Transfer the collected precipitate to a centrifuge tube and wash it sequentially with anhydrous ethanol and deionized water. After drying, the product is B-TiO2@2% ZIF-8.

[0043] B-TiO2@2% ZIF-8 powder was dispersed in anhydrous ethanol and continuously ground until it became a highly viscous viscous substance. It was then coated onto interdigitated electrodes and subjected to a 30-hour aging treatment. The response of the powder to acetone and humidity was then tested at room temperature using a gas-sensitive testing system.

[0044] Example 4

[0045] Add 20 mL of methanol to a beaker, then weigh 0.25 g of Zn(NO3)2·6H2O and 2.7 g of B-TiO2 nanorods prepared in step (2) and add them to the beaker. Stir magnetically for 10 minutes until completely dissolved. Separately weigh 1.08 g of 2-methylimidazole and add it to 20 mL of methanol. Stir magnetically for 5 minutes until completely dissolved to obtain a colorless and transparent ligand methanol solution. Mix the two solutions and stir magnetically for 30 minutes. The solution quickly turns into a milky white suspension. Then transfer the mixture to a polytetrafluoroethylene reactor, seal it, and place it in an oven at 120℃ for 24 hours. After the reaction is complete and the solution has cooled, collect the precipitate at the bottom. Transfer the collected precipitate to a centrifuge tube and wash it sequentially with anhydrous ethanol and deionized water. After drying, the product is obtained as B-TiO2@2.5% ZIF-8.

[0046] B-TiO2@2.5% ZIF-8 powder was dispersed in anhydrous ethanol and continuously ground until it became a highly viscous viscous substance. It was then coated onto interdigitated electrodes and subjected to a 30-hour aging treatment. The response of the electrodes to acetone and humidity was then tested at room temperature using a gas-sensitive testing system.

[0047] Comparative Example 1

[0048] Pure TiO2 nanorods were dispersed in anhydrous ethanol and continuously ground until they became a highly viscous viscous substance. This viscous substance was then coated onto interdigitated electrodes and subjected to a 30-hour aging treatment. The response of the nanorods to acetone and humidity was then tested at room temperature using a gas-sensitive testing system.

[0049] Comparative Example 2

[0050] Weigh the TiO2 nanorods prepared in step (1) and grind them with NaBH4 for 20 min until the mixture becomes a uniform and fine grayish-white powder with no obvious particle agglomeration. Then, perform thermal reduction under argon protection, keep at the temperature for 1 h, and then cool naturally to room temperature to obtain a black powder. Wash the product twice with ultrapure water and anhydrous ethanol to remove impurities and unreacted NaBH4. After centrifuging the solution, place it in a drying oven and dry it at 60℃ for 4 hours to obtain B-TiO2 nanorods.

[0051] Comparative Example 3

[0052] Add 20 mL of methanol to a beaker, weigh 0.25 g of Zn(NO3)2·6H2O, and stir magnetically for 10 minutes until completely dissolved. Separately, weigh 1.08 g of 2-methylimidazole and add it to 20 mL of methanol, stirring magnetically for 5 minutes until completely dissolved to obtain a colorless and transparent ligand methanol solution. Mix the two solutions and stir magnetically for 30 minutes; the solution quickly turns into a milky white suspension. Then, transfer the mixture to a polytetrafluoroethylene (PTFE) reactor, seal it, and place it in an oven at 120°C for 24 hours. After the reaction is complete and the solution cools, collect the precipitate at the bottom. Transfer the collected precipitate to a centrifuge tube and wash it sequentially with anhydrous ethanol and deionized water. After drying, the product yields pure ZIF-8 powder.

[0053] ZIF-8 powder was dispersed in anhydrous ethanol and continuously ground until it became a highly viscous viscous substance. It was then coated onto interdigitated electrodes and subjected to a 30-hour aging treatment. The response of the electrodes to acetone and humidity was then tested at room temperature using a gas-sensitive testing system.

[0054] Figure 1 The images show scanning electron microscope (SEM) images of the B-TiO2 nanorods prepared in Comparative Example 2 and the B-TiO2@ZIF-8 nanorods prepared in Examples 1, 3, and 4. Figure 1 (a) is a SEM image of B-TiO2 nanorods, which are approximately 400-500 nm in length and 50-80 nm in diameter. This one-dimensional structure has a large aspect ratio, which can provide sufficient surface contact sites, facilitating the subsequent coating process. Figure 1 (b) is a SEM image of B-TiO2 nanorods coated with 1% ZIF-8. The matrix structure of the B-TiO2 nanorods remains intact, and fine ZIF-8 particles begin to be uniformly attached to their surface. This process does not destroy the one-dimensional rod-shaped morphology of B-TiO2. Figure 1 (c) is a SEM image of B-TiO2 nanorods coated with 2% ZIF-8. When the ZIF-8 loading is increased, the coverage of ZIF-8 particles on the surface of the nanorods is significantly improved, and a continuous thin coating layer has been formed in some areas. At the same time, the pore structure between ZIF-8 particles is retained on the surface. Figure 1 (d) is a SEM image of the highly coated B-TiO2@ZIF-8 composite nanorods. The surface of the B-TiO2 nanorods is fully coated with a ZIF-8 layer, and ZIF-8 crystal particles are stacked and grown on the surface of the nanorods to form a rough and porous composite structure. This highly coated structure is achieved by controlling the high ligand concentration and reaction temperature. The ZIF-8 layer not only retains the chemical activity of the B-TiO2 nanorods, but also significantly improves the material's response performance to the target gas by utilizing its high specific surface area and selective adsorption characteristics.

[0055] Figure 2 The X-ray diffraction patterns are shown for the B-TiO2 nanorods prepared in Comparative Example 2, the pure ZIF-8 prepared in Comparative Example 3, and the B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4. The XRD patterns show that the characteristic diffraction peaks of B-TiO2 are clearly preserved in B-TiO2, pure ZIF-8, and B-TiO2@ZIF-8 samples with different ZIF-8 loadings (1%, 1.5%, 2%, and 2.5%), while the characteristic peaks of ZIF-8 are concentrated in the 10°-20° range, and the peak intensity gradually increases with increasing loading. This indicates that ZIF-8 has been successfully loaded onto the surface of B-TiO2, and the coating process has not damaged the original crystal structure of B-TiO2.

[0056] Figure 3 The reference resistance and response to 20 ppm acetone are shown for the TiO2 nanorods prepared in Comparative Example 1, the B-TiO2 nanorods prepared in Comparative Example 2, the pure ZIF-8 prepared in Comparative Example 3, and the B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4. The pure ZIF-8 material exhibits a low reference resistance but poor gas-sensitive response to acetone. B-TiO2, on the other hand, exhibits the opposite characteristics, possessing a high reference resistance and excellent acetone response. For the series of ZIF-8-coated modified samples, as the ZIF-8 loading gradually increases, the coating layer continuously covers the active sites on the B-TiO2 surface, hindering the interfacial interaction between gas molecules and the matrix, resulting in an overall decreasing trend in sample responsibility. The composite sample with a 2% loading achieves synergistic performance optimization, utilizing the porous structure of ZIF-8 to achieve efficient enrichment of acetone molecules while maximizing the effective utilization of the active sites on the B-TiO2 surface, exhibiting the relatively best gas-sensitive response performance among all modified samples.

[0057] Figure 4 The response values ​​of TiO2 nanorods prepared in Comparative Example 1, B-TiO2 nanorods prepared in Comparative Example 2, pure ZIF-8 prepared in Comparative Example 3, and B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4 to different concentrations of acetone are compared. Figure 4 (a) The results showed that, within the acetone concentration range of 5–200 ppm, the gas-sensing response of samples with different ZIF-8 coating ratios increased with increasing acetone concentration; however, the sample response performance gradually decreased with increasing ZIF-8 loading. Figure 4(b) A comparison of the gas-sensing performance of TiO2, B-TiO2, pure ZIF-8, and B-TiO2@2% ZIF-8 shows that pure ZIF-8 consistently maintains a low response level to acetone. B-TiO2 exhibits a better acetone response than pure TiO2, attributed to the exposure of its unique crystal faces providing more active sites and a more complete interfacial charge transfer process. Furthermore, the gas-sensing response of B-TiO2@2% ZIF-8 is significantly superior to the other materials. The 2% loading ratio achieves a good balance between the enrichment of acetone molecules in the porous structure of ZIF-8 and the effective exposure of the active sites in B-TiO2; therefore, this ratio represents the optimal composite sample.

[0058] Figure 5 This study compares the response values ​​of TiO2 nanorods prepared in Comparative Example 1, pure ZIF-8 prepared in Comparative Example 3, and B-TiO2@ZIF-8 prepared in Example 3 to different types of gases. Gas selectivity comparison tests show that B-TiO2@2%ZIF-8 exhibits a significantly higher response to acetone than common interfering gases in human exhalation and the environment, such as H2S and C2H5OH. In contrast, pure ZIF-8 and pure TiO2 show poor selectivity for acetone. The high selectivity of this sample stems from the molecular sieving effect of the pore size of ZIF-8, which selectively adsorbs acetone molecules. Simultaneously, there is a specific interaction between its surface functional groups and acetone molecules. Combined with the high gas-sensitive activity of B-TiO2 for acetone, the two work synergistically, ultimately significantly improving the gas-sensitive selectivity of the composite material for acetone.

[0059] Figure 6 This study compares the response values ​​of TiO2 nanorods prepared in Comparative Example 1, B-TiO2 nanorods prepared in Comparative Example 2, and B-TiO2@ZIF-8 prepared in Examples 1, 2, 3, and 4 to 20 ppm acetone under dry (50% RH) and humid (90% RH) conditions. The results show that the overall response of pure TiO2 is low, and the response under humid conditions (2.6) is much lower than that under dry conditions (5.6), indicating a significant interference from humidity. B-TiO2 exhibits a response value of 15.8 under dry conditions, demonstrating strong acetone gas-sensing activity, but the response drops sharply to 7.1 under humid conditions, a loss of up to 55%, indicating a significant impact from humidity. In contrast, the ZIF-8-coated samples not only generally show higher response values ​​under dry conditions than pure TiO2, but more importantly, the difference in response values ​​between dry and humid conditions is significantly reduced. For example, the 2% ZIF-8 coated sample had a response of 13.0 under dry conditions and 11.1 under humid conditions, with a response value decrease of only 14.6%. This indicates that ZIF-8 coating effectively weakens the interference of humidity on the acetone response, making the sample's response to acetone more stable under different humidity environments, while retaining good gas-sensing activity.

[0060] Figure 7The results show that the response of B-TiO2@2% ZIF-8 to human exhalation between 11 and 20 pm is highly synchronized with the measured blood glucose value change trend, and can accurately generate response signals according to blood glucose fluctuations. Human exhalation is a near-saturated high-humidity environment, which easily interferes with traditional gas-sensitive materials, causing signal distortion and poor stability; however, the ZIF-8 coating modification effectively improves the moisture resistance of B-TiO2, weakens the interference of high-humidity environment, and enables the material to stably capture blood glucose-related characteristic signals. The excellent moisture resistance is the key to the synchronization of the two changes, proving that the material has good signal recognition and stable response capabilities in high-humidity exhalation detection, and has potential application value in the field of non-invasive blood glucose detection sensors.

Claims

1. A method for preparing a nanorod-shaped B-TiO2 acetone gas-sensitive material, characterized in that, Includes the following steps: (1) Preparation of TiO2 nanorods: Prepare a 15-25% NaOH solution, mix tetrabutyl titanate and anhydrous ethanol at a volume ratio of 3:20 and add them dropwise to the NaOH solution. After hydrothermal reaction, wash and dry to obtain TiO2 nanorods. (2) Preparation of B-TiO2 nanorods: The TiO2 nanorods obtained in step (1) are mixed and ground with NaBH4 at a mass ratio of 2:1-1:2, and then thermally reduced at 300-400℃ for 1 h under argon protection. After cleaning and drying, B-TiO2 nanorods are obtained. (3) Preparation of B-TiO2@ZIF-8: Zn(NO3)2·6H2O and B-TiO2 nanorods were added to methanol, and 2-methylimidazolium was dissolved in methanol. After mixing, the mixture was subjected to hydrothermal reaction at 120-150℃ for 12-24 h. After washing and drying, B-TiO2 coated with ZIF-8 was obtained. (4) Annealing treatment: The product of step (3) is annealed at 200°C for 6 h under argon protection.

2. The preparation method according to claim 1, characterized in that, The concentration of the NaOH solution mentioned in step (1) is 20%.

3. The preparation method according to claim 1, characterized in that, The mass ratio of TiO2 nanorods to NaBH4 in step (2) is 2:

1.

4. The preparation method according to claim 1, characterized in that, The temperature for thermal reduction in step (2) is 350℃, and the holding time is 1 h.

5. The preparation method according to claim 1, characterized in that, In step (2), the heating rate of the tubular furnace is 8-10℃ / min.

6. The preparation method according to claim 1, characterized in that, The amount of Zn(NO3)2·6H2O added in step (3) is 0.2 g, and the amount of 2-methylimidazole added is 0.87 g.

7. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature in step (3) is 120℃ and the reaction time is 24 h.

8. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature in step (3) is 150°C.

9. The preparation method according to claim 1, characterized in that, The annealing process is carried out in an argon atmosphere for 6 hours.

10. The application of the ZIF-8 coated nanorod-shaped B-TiO2 acetone gas-sensitive material obtained by the preparation method according to any one of claims 1-9 in the detection of acetone gas in a high humidity environment.

Images