Gel color developing patch for indicating VOCs in ward based on photocatalysis and preparation method thereof

Abstract

The application discloses a gel color developing patch for indicating VOCs in a sickroom based on photocatalysis and a preparation method thereof. The gel color developing patch comprises, in percentage by mass, 1.4-2.0% of graphite phase carbon nitride g-C3N4, 0.2-1.0% of fluoran dye, 5.0-7.0% of polyvinyl alcohol (PVA) and 90.0-93.4% of distilled water. The polyvinyl alcohol is dissolved in deionized water to obtain a PVA solution; a nanometer flake aqueous solution of graphite phase carbon nitride g-C3N4 and the fluoran dye are added into the PVA solution, and the mixture is stirred at room temperature until uniform, to obtain a reaction liquid; the reaction liquid is transferred into a glass container and sealed, and is repeatedly frozen and thawed for multiple times, to obtain the gel color developing patch. The gel color developing patch is used for visual detection of VOCs in air in a sickroom of a hospital, and is helpful for monitoring emission of VOCs in a hospital room and finding a pollution source.

Description

Technical Field

[0001] This invention relates to the field of VOCs detection technology, and more specifically, to a gel colorimetric patch for indicating VOCs in hospital wards based on photocatalysis and its preparation method. Background Technology

[0002] Given the high volume and diverse composition of atmospheric VOCs in my country, it is essential to combine multiple technologies to achieve optimal treatment results. Photocatalysis is a highly efficient, green, thorough, and pollution-free technology for VOCs treatment. This method demonstrates good treatment efficacy for low concentrations of VOCs or odor molecules, thus showing promising application prospects in indoor VOCs treatment. Developing new photocatalytic materials or technologies, such as combining photocatalysis with other technologies (adsorption, colorimetry, etc.), could become another avenue for optimizing the detection of organic pollutants.

[0003] Hospitals, as public environments, experience high traffic. They also store and use various medications, resulting in a wide variety and high concentration of volatile organic compounds (VOCs) in their indoor air. Alkanes, alkenes, and aromatic hydrocarbons account for approximately 61%–98% of these VOCs. Alkanes, primarily ethane, propane, n-butane, isobutane, and isopentane, constitute over 50% of the total. Alkenes, mainly ethylene, propylene, and isoprene, account for approximately 53%–83% of the total. Aromatic hydrocarbons, primarily benzene, toluene, ethylbenzene, xylene, and styrene, account for approximately 79%–98%. Although the composition of aromatic hydrocarbons varies significantly between different waiting areas, the high concentrations of VOCs in most indoor areas indicate that these pollutants originate from indoor sources.

[0004] Therefore, the detection and monitoring of VOCs in hospital indoor environments is of great significance. However, most current air quality monitoring instruments are expensive, complex to operate, and space-consuming. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a gel colorimetric patch based on photocatalysis to indicate VOCs in hospital wards and its preparation method, so as to achieve the purpose of simple and visual detection of VOCs in the air in hospital wards.

[0006] To address the above technical problems, according to one aspect of the present invention, a gel colorimetric patch for indicating VOCs in wards based on photocatalysis is provided, comprising, by weight percentage, 1.4-2.0% graphitic carbon nitride g-C3N4, 0.2-1.0% fluorane dye, 5.0-7.0% polyvinyl alcohol (PVA), and 90.0-93.4% distilled water.

[0007] According to another aspect of the present invention, a method for preparing the above-mentioned photocatalytically indicative ward VOCs gel colorimetric patch is provided, comprising:

[0008] Step 1: Dissolve polyvinyl alcohol (PVA) in deionized water to obtain a PVA solution;

[0009] Step 2: Add the aqueous solution of graphitic carbon nitride g-C3N4 nanosheets and fluorane dye to the PVA solution, and stir at room temperature until the mixture is homogeneous to obtain the reaction solution;

[0010] Step 3: Transfer the reaction solution to a glass container and seal it. Freeze it at -17℃ to -19℃ for 18 to 22 hours, and then thaw it at room temperature for 3 to 5 hours. Repeat this cycle multiple times to obtain the gel colorimetric patch based on photocatalysis to indicate VOCs in the ward.

[0011] Further, in step one, polyvinyl alcohol (PVA) is dissolved in deionized water, stirred at 95 °C for 2-5 h, and cooled to room temperature to obtain a PVA solution.

[0012] Furthermore, the preparation method of the graphite phase carbon nitride g-C3N4 is as follows: 0.5-2.0g of melamine and 0.1-0.5g of polyvinyl alcohol (PVA) are heated to 550℃ in a muffle furnace at a heating rate of 5℃ / min and held for 3h to obtain graphite phase carbon nitride g-C3N4.

[0013] Furthermore, 400 mg of graphitic carbon nitride g-C3N4 was ground and dissolved in 100 mL of deionized water and sonicated for 20 h to obtain an aqueous solution of g-C3N4 nanosheets with a concentration of 4 mg / mL.

[0014] Furthermore, in step two, stir at room temperature for 12-24 hours until the mixture is homogeneous.

[0015] Furthermore, in step three, the sample is frozen in a -18°C freezer for 20 hours, then thawed at room temperature for 4 hours. This cycle is repeated three times to obtain the gel colorimetric patch based on photocatalytic indication of VOCs in the ward.

[0016] According to another aspect of the present invention, the application of the above-described photocatalytic indicator gel colorimetric patch for visual detection of volatile organic compounds in hospital ward air is provided.

[0017] The gel colorimetric patch described in this invention is a portable, visual composite gel for detecting VOCs in indoor air. It is used to detect VOCs in the air and has the advantages of good selectivity and simple operation, which helps to monitor VOC emissions in hospitals and find pollution sources. Attached Figure Description

[0018] Figure 1 This is a transmission electron microscope image of g-C3N4 nanosheets in Example 1 of this invention.

[0019] Figure 2 According to Example 1 of the present invention, the gel colorimetric patch was placed in a hospital ward for 1 day before ( Figure 2 A) After ( Figure 2 B) The color development state. Detailed Implementation

[0020] To address the necessity of VOCs monitoring in hospital indoor environments and the problem of expensive and complex instruments and equipment, this invention develops a simple composite gel colorimetric patch that can directly indicate VOCs in the air.

[0021] A typical embodiment of the present invention provides a gel colorimetric patch based on photocatalytic indication of VOCs in wards, which, by weight percentage, comprises 1.4-2.0% graphitic carbon nitride g-C3N4, 0.2-1.0% fluorane dye, 5.0-7.0% polyvinyl alcohol (PVA) and 90.0-93.4% distilled water.

[0022] The concept of this invention is to treat VOCs using photocatalysis. It utilizes the synergistic effect between light and the catalytic material, graphitic carbon nitride (g-C3N4). When light irradiates the surface of the catalytic material, electron transitions occur when the photon energy exceeds the band gap between the valence and conduction bands. Under the influence of an electric field, electrons accumulate in the conduction band, while holes accumulate in the valence band. Electrons and holes possess high reducing and oxidizing properties, respectively. Water vapor, under the influence of high-energy electrons, generates hydroxyl radicals, which also possess strong oxidizing properties. The VOCs adsorbed by the system undergo a series of oxidation reactions on the surface of the catalytic material, transforming into organic acids with a certain degree of acidity. These organic acids can cause a fluorane dye indicator to change color, thus achieving visual monitoring. Fluorane violet dye exhibits sharp color development, high stability, and high intensity in the colorimetric reaction. When fluorane violet dye encounters acid, it reacts with the acid, causing the lactone ring to cleave and releasing color.

[0023] The gel colorimetric patch described in the above embodiments is a portable, visual composite hydrogel for detecting VOCs in indoor air. Its usage and detection effect in a practical testing scenario are as follows: the gel colorimetric patch is placed directly in a clean area of ​​the testing scenario, and the color of the composite hydrogel is observed after 1 day. If the indoor VOCs concentration is too high, the composite gel will appear purple, and the higher the VOCs concentration, the deeper the purple color of the composite hydrogel.

[0024] This detection method has the advantages of good selectivity and simple operation, which helps to monitor indoor VOCs emissions in hospitals and find pollution sources.

[0025] The preparation method of the gel colorimetric patch based on photocatalysis to indicate VOCs in wards, as described above, includes the following steps.

[0026] Step 1: Dissolve polyvinyl alcohol (PVA) in deionized water to obtain a PVA solution.

[0027] More specifically, polyvinyl alcohol (PVA) is dissolved in deionized water, stirred at 95 °C for 2-5 h, and then cooled to room temperature to obtain a PVA solution.

[0028] Step 2: Add the aqueous solution of graphitic carbon nitride g-C3N4 nanosheets and fluorane dye to the PVA solution, and stir at room temperature until the mixture is homogeneous to obtain the reaction solution.

[0029] The preparation method of the graphitic carbon nitride g-C3N4 is as follows: 0.5-2.0 g of melamine and 0.1-0.5 g of polyvinyl alcohol (PVA) are heated to 550 °C in a muffle furnace at a heating rate of 5 °C / min and held for 3 h to obtain graphitic carbon nitride g-C3N4. 400 mg of graphitic carbon nitride g-C3N4 is ground and dissolved in 100 mL of deionized water and sonicated for 20 h to obtain an aqueous solution of g-C3N4 nanosheets with a concentration of 4 mg / mL.

[0030] Step 3: Transfer the reaction solution to a glass container and seal it. Freeze it at -17℃ to -19℃ for 18 to 22 hours, and then thaw it at room temperature for 3 to 5 hours. Repeat this cycle multiple times to obtain the gel colorimetric patch based on photocatalysis to indicate VOCs in the ward.

[0031] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments and comparative examples are for explaining the implementation schemes of this invention and do not exceed the scope of the subject matter of this invention. The scope of protection of this invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art. Example 1

[0032] 0.5 g of melamine and 0.5 g of polyvinyl alcohol (PVA) were heated to 550 °C in a muffle furnace at a heating rate of 5 °C / min and held for 3 h to obtain graphitic carbon nitride g-C3N4. 400 mg of the prepared g-C3N4 was ground and dissolved in 100 mL of deionized water and sonicated for 20 h to obtain an aqueous solution of g-C3N4 nanosheets with a mass concentration of 4 mg / mL.

[0033] 6.0 mg of polyvinyl alcohol (PVA) was dissolved in 100 mL of deionized water and stirred at 95 °C for 5 h. The mixture was then cooled to room temperature to obtain a PVA solution. 0.4 mL of a 4 mg / mL g-C3N4 solution and 0.5 mg of fluorane dye were added to the PVA solution, and the mixture was stirred at room temperature for 20 h until homogeneous to obtain a reaction solution. The reaction solution was transferred to a 2 × 2 × 0.2 cm glass container, sealed, and frozen at -18 °C for 20 h. Afterward, it was thawed at room temperature for 4 h, and this cycle was repeated three times to obtain a g-C3N4 / fluorane dye / PVA composite gel.

[0034] Transmission electron microscope images of g-C3N4 nanosheets obtained in Example 1 are shown below. Figure 1 As shown. The g-C3N4 / fluorane dye / PVA composite gel obtained in Example 1 was placed directly in a clean area of ​​a hospital ward. After 1 day, the composite hydrogel was observed to be purple. Figure 2 As shown in B. Example 2

[0035] 2.0 g of melamine and 0.1 g of polyvinyl alcohol (PVA) were heated to 550 °C in a muffle furnace at a heating rate of 5 °C / min and held for 3 h to obtain graphitic carbon nitride g-C3N4. 400 mg of the prepared g-C3N4 was ground and dissolved in 100 mL of deionized water and sonicated for 20 h to obtain an aqueous solution of g-C3N4 nanosheets with a mass concentration of 4 mg / mL.

[0036] 7.0 mg of polyvinyl alcohol (PVA) was dissolved in 100 mL of deionized water and stirred at 95 °C for 5 h. The mixture was then cooled to room temperature to obtain a PVA solution. 0.4 mL of 0.4 mg / mL g-C3N4 solution and 0.5 mg of fluorane dye were added to the PVA solution, and the mixture was stirred at room temperature for 12 h until homogeneous to obtain a reaction solution. The reaction solution was transferred to a 2 × 2 × 0.2 cm glass container, sealed, and frozen at -17 °C for 22 h. Afterward, it was thawed at room temperature for 5 h, and this cycle was repeated three times to obtain a g-C3N4 / fluorane dye / PVA composite gel. Example 3

[0037] 2.0 g of melamine and 0.1 g of polyvinyl alcohol (PVA) were heated to 550 °C in a muffle furnace at a heating rate of 5 °C / min and held for 3 h to obtain graphitic carbon nitride g-C3N4. 400 mg of the prepared g-C3N4 was ground and dissolved in 100 mL of deionized water and sonicated for 20 h to obtain an aqueous solution of g-C3N4 nanosheets with a mass concentration of 4 mg / mL.

[0038] 7.0 mg of polyvinyl alcohol (PVA) was dissolved in 100 mL of deionized water and stirred at 95 °C for 5 h. The mixture was then cooled to room temperature to obtain a PVA solution. 0.5 mL of a 4 mg / mL g-C3N4 solution and 1.0 mg of fluorane dye were added to the PVA solution, and the mixture was stirred at room temperature for 24 h until homogeneous to obtain a reaction solution. The reaction solution was transferred to a 2 × 2 × 0.2 cm glass container, sealed, and frozen at -19 °C for 18 h. Afterward, it was thawed at room temperature for 3 h, and this cycle was repeated three times to obtain a g-C3N4 / fluorane dye / PVA composite gel.

[0039] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A gel colorimetric patch for indicating VOCs in hospital wards based on photocatalysis, characterized in that: By weight percentage, it includes 1.4-2.0% graphitic carbon nitride g-C3N4, 0.2-1.0% fluorane dye, 5.0-7.0% polyvinyl alcohol (PVA) and 90.0-93.4% distilled water.

2. The preparation method of the gel colorimetric patch based on photocatalysis to indicate VOCs in wards according to claim 1, characterized in that, include: Step 1: Dissolve polyvinyl alcohol (PVA) in deionized water to obtain a PVA solution; Step 2: Add the aqueous solution of graphitic carbon nitride g-C3N4 nanosheets and fluorane dye to the PVA solution, and stir at room temperature until the mixture is homogeneous to obtain the reaction solution; Step 3: Transfer the reaction solution to a glass container and seal it. Freeze it at -17℃ to -19℃ for 18 to 22 hours, and then thaw it at room temperature for 3 to 5 hours. Repeat this cycle multiple times to obtain the gel colorimetric patch based on photocatalysis to indicate VOCs in the ward.

3. The method for preparing the gel colorimetric patch based on photocatalysis to indicate VOCs in wards according to claim 2, characterized in that, In step one, polyvinyl alcohol (PVA) is dissolved in deionized water, stirred at 95 °C for 2-5 h, and then cooled to room temperature to obtain a PVA solution.

4. The method for preparing the gel colorimetric patch based on photocatalysis to indicate VOCs in wards according to claim 2 or 3, characterized in that, The preparation method of the graphitic carbon nitride g-C3N4 is as follows: 0.5-2.0g of melamine and 0.1-0.5g of polyvinyl alcohol (PVA) are heated to 550℃ in a muffle furnace at a heating rate of 5℃ / min and held for 3h to obtain graphitic carbon nitride g-C3N4.

5. The preparation method of the gel colorimetric patch based on photocatalysis to indicate VOCs in wards according to claim 4, characterized in that: 400 mg of graphitic carbon nitride g-C3N4 was ground and dissolved in 100 mL of deionized water and sonicated for 20 h to obtain an aqueous solution of g-C3N4 nanosheets with a concentration of 4 mg / mL.

6. The method for preparing the gel colorimetric patch based on photocatalysis to indicate VOCs in wards according to claim 5, characterized in that: In step two, stir at room temperature for 12-24 hours until the mixture is homogeneous.

7. The method for preparing the gel colorimetric patch based on photocatalysis to indicate VOCs in wards according to claim 1, characterized in that: In step three, the sample is frozen in a -18°C freezer for 20 hours, then thawed at room temperature for 4 hours. This cycle is repeated three times to obtain the gel colorimetric patch based on photocatalytic indication of VOCs in the ward.

8. The application of the photocatalytic indicator gel colorimetric patch for VOCs in hospital wards as described in claim 1 in the visual detection of volatile organic compounds in hospital ward air.

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