Hydrogen-sensitive color-changing dye and preparation method thereof

Abstract

The invention relates to the technical field of sensing detection, in particular to a hydrogen-sensitive color-changing dye and a preparation method thereof. The hydrogen-sensitive color-changing dye takes a-WO3 / Pd quantum dots as a main effective component. The preparation method of the a-WO3 / Pd quantum dot comprises the following steps: placing a tungsten sheet as an anode in an electrolyte for anodic oxidation to obtain a quantum tungsten oxide solution; mixing a potassium hypochloropalladate solution with the quantum tungsten oxide solution to obtain a reaction solution; and carrying out ultraviolet irradiation on the reaction liquid to obtain the a-WO3 / Pd quantum dot. The a-WO3 / Pd quantum dots are prepared through an anodic oxidation-ultraviolet reduction method, the hydrogen-sensitive color-changing dye with excellent hydrogen-sensitive color-changing performance is prepared through further dispersion, when the dye is exposed to low-concentration hydrogen (200 ppm), chromatic aberration can be distinguished and recognized by naked eyes, and the dye can be applied to important fields such as hydrogen track conveying, hydrogen storage equipment protection and hydrogen operator protection and has good application prospects. The method has a wide application scene and a huge value space.

Description

Technical Field

[0001] The invention relates to the field of sensing detection technology, in particular to a hydrogen-sensitive color-changing dye and a preparation method thereof. Background Art

[0002] Compared with traditional fossil fuel energy, hydrogen energy is considered to be the clean energy with the greatest development potential in the 21st century due to its wide sources, environmental protection, non-toxicity, low calorific value, low ignition point, wide application and renewable advantages. At the same time, hydrogen, as an important chemical raw material, plays a key role in the fields of petrochemicals, electronics, metallurgy, food processing, fine organic synthesis, and aerospace. However, hydrogen has the characteristics of being colorless and odorless, small in size, light in weight, and fast in diffusion, and has low ignition energy, low ignition point, and a wide explosion range (4.0% to 75.6%). Therefore, it is necessary to monitor hydrogen leakage in the hydrogen use environment in a timely manner to eliminate the explosion hazard. Especially in the fields of long-distance rail transportation and operation in hydrogen environment, there is an urgent need for a safe, convenient, low-cost hydrogen warning method that can be directly observed by staff. At present, semiconductor type, catalytic combustion type, field effect transistor type, electrochemical type and other hydrogen sensors are widely studied, but they generally require current voltage drive and high temperature drive, and the signal detection cost is high. In comparison, colorimetric hydrogen sensors have received increasing attention due to their low maintenance cost, no driver, high wearable compatibility, and ease of direct observation.

[0003] Shankara S.Kalanur et al. prepared Pd / MoO by combining hydrothermal method and photochemical reduction method. 3 The sensor changes color in 10% hydrogen and changes transmittance by 10% in 7 minutes. Zhang et al. deposited amorphous nano-columnar WO on a glass substrate using magnetron sputtering technology. 3 , and then Pd catalyst was deposited on WO by electron beam evaporation. 3 The sensor is 1% H 2 Producing a color difference of 52, the response time is 10min; Wanyu Qi et al. prepared WO by sol-gel method 3 The colloid was coated on PET and the catalytic layer was prepared by dip coating. The sensor can detect 4% H 2 However, the above color-developing hydrogen sensors do not simultaneously meet the practical requirements of obvious color development, rapid color development, low test limit, color reversibility, repeated color development, and low operating temperature, which is still a problem to be solved. Summary of the invention

[0004] Based on the above content, the present invention provides a 3 / Pd quantum dot hydrogen-sensitive color-changing fuel and its preparation method can be mixed with fabrics, polymers, etc. to prepare various hydrogen-sensitive color-changing labels. The dye is simple to prepare, has low production cost, obvious color change, rapid color change, low detection limit, good repeatability, and has huge application potential and value space in the fields of pipeline gas leakage monitoring, hydrogen storage equipment condition detection, etc.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is an a-WO 3 / Pd quantum dot preparation method, comprising the following steps:

[0007] The tungsten sheet is placed in an electrolyte as an anode for anodic oxidation to obtain a quantum tungsten oxide solution;

[0008] Mixing the potassium hypochloropalladate solution with the quantum tungsten oxide solution to obtain a reaction solution;

[0009] The reaction solution is irradiated with ultraviolet light to obtain the a-WO 3 / Pd quantum dots.

[0010] The second technical solution of the present invention is an a-WO prepared according to the above-mentioned preparation method. 3 / Pd quantum dots.

[0011] The third technical solution of the present invention is that the a-WO 3 / Application of Pd quantum dots in the preparation of hydrogen-sensitive color-changing products.

[0012] The fourth technical solution of the present invention is a hydrogen-sensitive color-changing dye, the raw materials of which include the a-WO 3 / Pd quantum dots.

[0013] A fifth technical solution of the present invention is a method for preparing the hydrogen-sensitive color-changing dye, comprising: 3 / Pd quantum dots are dissolved in a solvent.

[0014] The sixth technical solution of the present invention is a hydrogen-sensitive color-changing mark, the raw material includes the a-WO 3 / Pd quantum dots or the hydrogen-sensitive color-changing dye.

[0015] The present invention discloses the following technical effects:

[0016] (1) The present invention uses an anodic oxidation-ultraviolet reduction method to prepare a-WO 3 / Pd quantum dots, a-WO 3 The overall size of the a-WO / Pd quantum dots is uniform and controllable. 3The average particle size is less than 5nm. The quantum dot-level particle size gives it a large specific surface area, providing a large number of adsorption sites for palladium quantum dots and gas reactions; palladium quantum dots are photochemically reduced and uniformly attached to the surface of tungsten oxide quantum dots, and their particle size is controlled within 5nm. The uniform particle size of tungsten oxide quantum dots and the uniform modification of palladium quantum dot catalysts further improve the color-changing performance of this dye.

[0017] (2) With the a-WO of the present invention 3 / Pd quantum dots are used as dyes to impregnate filter paper, which has room temperature hydrogen-sensitive color change performance. Specifically, the color-changing sample can reach a color difference value of 52 within 20 seconds when exposed to 1% volume concentration of hydrogen at room temperature; when exposed to low concentration of hydrogen (200ppm), the color difference can be distinguished and identified by the naked eye; when exposed to air, it can be slowly bleached to the initial color, providing a historical leakage record for hydrogen leakage that was not detected in time.

[0018] (3) a-WO of the present invention 3 / Pd quantum dots are a kind of hydrogen-sensitive color-changing dye with a wide range of uses. For example, they can be mixed with flexible slurries such as silica gel and PDMS to prepare hydrogen color-changing tapes, and can be directly dyed on flexible materials such as non-woven fabrics and cotton cloth to prepare hydrogen color-changing labels. They can be coated on the surface of flexible substrates such as PI to obtain hydrogen color-changing films, which can then be used in important fields such as hydrogen rail transportation, protection of hydrogen storage equipment, and protection of hydrogen workers to achieve "naked eye observation" of hydrogen leakage, with broad application scenarios and huge value space. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The a-WO in the quantum tungsten oxide solution prepared in Example 1 3 TEM image of.

[0021] Figure 2 a-WO prepared in Example 1 3 TEM image of Pd / QDs.

[0022] Figure 3 In order to utilize the a-WO in Example 1 3The hydrogen-sensitive color-changing dye prepared by Pd / Pd quantum dots is applied to the color change and bleaching process of filter paper samples; among them, (a) is the hydrogen-sensitive color change process of the sample in 200ppm hydrogen, (b) is the hydrogen-sensitive color change process of the sample in 1% hydrogen, and (c) is the bleaching process of the sample exposed to air after color change (1% hydrogen). DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] The present invention proposes an a-WO that can work at room temperature, has a short color change time, obvious color change, and a detection limit of ppm level. 3 / Pd quantum dots, the a-WO 3 / Pd quantum dots can be used as the main effective component to prepare hydrogen-sensitive color-changing dyes. 3The preparation method of / Pd quantum dots is an anodic oxidation-ultraviolet reduction method. The present invention can be used to prepare hydrogen-sensitive color-changing marks by dyeing fiber fabrics with hydrogen-sensitive color-changing dyes, mixing with flexible slurry, and directly coating the surface of a rigid substrate, thereby realizing naked-eye hydrogen identification in various scenarios such as pipeline hydrogen leakage detection and safety protection of hydrogen workers.

[0029] In a first aspect, the present invention provides an a-WO 3 / Pd quantum dot preparation method, comprising the following steps:

[0030] The tungsten sheet is placed in an electrolyte as an anode for anodic oxidation to obtain a quantum tungsten oxide solution;

[0031] Mixing the potassium hypochloropalladate solution with the quantum tungsten oxide solution to obtain a reaction solution;

[0032] The reaction solution is irradiated with ultraviolet light to obtain the a-WO 3 / Pd quantum dots.

[0033] In some specific embodiments of the present invention, the tungsten sheet is a tungsten metal sheet with a purity of 98% to 100%. The tungsten sheet also includes the steps of polishing, cleaning, and nitrogen drying before anodizing.

[0034] In some specific embodiments of the present invention, the tungsten sheet is polished with sandpaper or a grinder to remove tungsten oxide impurities on the surface.

[0035] In some specific embodiments of the present invention, two tungsten sheets are placed in parallel in the electrolyte, and the parallel distance between the tungsten sheets is 1-200 mm.

[0036] In a preferred embodiment of the present invention, the electrolyte is an aqueous solution of hydrochloric acid with a pH value of 0.1-3.

[0037] In a preferred embodiment of the present invention, the anodization is carried out under constant current or constant voltage conditions; the current range of the constant current is 0.02A to 5A; the voltage range of the constant voltage is 10V to 80V; and the anodization time is 1min to 240min.

[0038] In the present invention, if the concentration of the hydrochloric acid aqueous solution is too high, a too thick oxide layer will be formed on the surface of the tungsten sheet, resulting in a slow oxidation rate. If the concentration of the hydrochloric acid aqueous solution is too low, the electrolyte conductivity will be low and oxidation cannot be performed, which ultimately affects the preparation of quantum tungsten oxide.

[0039] In the present invention, too high current or voltage will lead to too fast anodization rate, which will easily damage the tungsten sheet, resulting in inconsistent thickness of the tungsten sheet and affecting the particle size of tungsten oxide. Too low current or voltage will lead to too slow anodization rate.

[0040] Whether it is the concentration of the hydrochloric acid aqueous solution or the parameters of the current or voltage, they all have an impact on the crystallinity, structure and particle size of the tungsten oxide released by anodization. After repeated experiments, the present invention has found that amorphous quantum tungsten oxide can only be obtained within the above parameter range.

[0041] In a preferred embodiment of the present invention, the concentration of quantum tungsten oxide in the quantum tungsten oxide (tungsten oxide quantum dots) solution is 0.275 mol / L to 2.75 mol / L; the concentration of the potassium hypochlorous palladium solution is 0.1 mol / L to 1 mol / L; the solvent of the potassium hypochlorous palladium solution is water; the volume ratio of the potassium hypochlorous palladium solution to the quantum tungsten oxide solution is 20:1 to 1:20.

[0042] In a preferred embodiment of the present invention, the wavelength of the ultraviolet light irradiation is 254 nm, the power is 6-18 W, and the time is 3 min to 60 min.

[0043] The reaction solution needs to be stirred during the ultraviolet irradiation process.

[0044] In some specific embodiments of the present invention, the steps of washing and drying are further included after the ultraviolet irradiation is completed.

[0045] The second aspect of the present invention provides an a-WO prepared according to the above preparation method. 3 / Pd quantum dots.

[0046] The third aspect of the present invention provides the a-WO 3 / Application of Pd quantum dots in the preparation of hydrogen-sensitive color-changing products.

[0047] The fourth aspect of the present invention provides a hydrogen-sensitive color-changing dye, the raw materials of which include the a-WO 3 / Pd quantum dots.

[0048] The fifth aspect of the present invention provides a method for preparing the hydrogen-sensitive color-changing dye, comprising: 3 / Pd quantum dots are dissolved in a solvent.

[0049] In some specific embodiments of the present invention, the solvent may be an ethanol solution. The present invention does not impose any particular limitation on the concentration of the ethanol solution, which can make a-WO 3 / Pd quantum dots are fully dissolved and evenly dispersed.

[0050] The sixth aspect of the present invention provides a hydrogen-sensitive color-changing mark, the raw material includes the a-WO 3 / Pd quantum dots or the hydrogen-sensitive color-changing dye.

[0051] In some specific embodiments of the present invention, the preparation method of the hydrogen-sensitive color-changing mark includes: dipping filter paper and fiber fabric in hydrogen-sensitive color-changing dye, and obtaining a hydrogen-sensitive color-changing mark that can be used for hydrogen identification through multiple dipping and drying; or, mixing the hydrogen-sensitive color-changing dye with a polymer and PDMS in a ratio of 5:1 to 1:5 and then curing the mixture to obtain a hydrogen-sensitive color-changing tape, and applying the hydrogen-sensitive color-changing dye to a rigid substrate to obtain a hydrogen-sensitive color-changing film.

[0052] The present invention obtains amorphous tungsten oxide quantum dots by a simple and convenient anodic oxidation method, and then generates palladium quantum dots attached to the amorphous tungsten oxide quantum dots by ultraviolet reduction in a mixed solution of amorphous tungsten oxide quantum dots and potassium hypochloropalladate, thereby preparing tungsten oxide quantum dots (i.e., a-WO) uniformly loaded with palladium quantum dot catalysts. 3 / Pd quantum dots). The amorphous tungsten oxide quantum dots are evenly distributed, with a particle size range of 2-5nm, thus having a large specific surface area to provide more active sites for the adsorption and reaction of catalysts and hydrogen; the presence of amorphous tungsten oxide quantum dots during the ultraviolet reduction process can promote and guide the formation of palladium crystals, so that the palladium quantum dots cling to the vicinity of the amorphous tungsten oxide quantum dots; the stirring-assisted ultraviolet reduction technology can make the generated Pd crystals have a particle size of quantum dot level and a uniform size. 3 The controllable quantum dot-level particle size and uniform distribution of Pd quantum dots improve their color rendering performance as a sensor.

[0053] a-WO of the present invention 3 / Pd quantum dots as hydrogen-sensitive color-changing dyes have superior properties such as room temperature hydrogen-sensitive color-changing, wide detection range, low detection limit, and repeatable color development. The dye is exposed to 1% hydrogen at room temperature and completes an ultra-obvious color change response from light brown to dark blue in an ultra-short time (20s), and is quasi-reversible in the air, that is, it can be slowly bleached to the initial color in the air, and the leakage history is recorded in a short time; the color difference of the hydrogen-sensitive color-changing dye of the present invention is sufficient to be observed by the naked eye in a hydrogen concentration as low as 200ppm.

[0054] The present invention is based on a-WO 3 / Pd quantum dot hydrogen-sensitive color-changing dyes can be used to prepare hydrogen-sensitive color-changing labels by dyeing fiber fabrics, mixing with flexible slurries, etc. For example, hydrogen-sensitive color-changing dyes can be dyed into fiber fabrics as warning labels to be worn on the body to monitor hydrogen leakage in the experimental environment; hydrogen-sensitive color-changing dyes can be mixed evenly with flexible slurries such as PDMS and silica gel and then cured to prepare hydrogen-sensitive color-changing tapes, which can be applied to potential hydrogen leakage points in pipelines to facilitate "naked eye detection" by inspection personnel and timely troubleshoot hydrogen leakage.

[0055] The present invention is based on a-WO 3The hydrogen-sensitive color-changing dye of Pd / Pd quantum dots can be used for the preparation of hydrogen identification marks by methods such as dyeing fiber fabrics, mixing with flexible slurry, and coating on the surface of rigid substrates. The hydrogen identification mark prepared with the hydrogen-sensitive color-changing dye has high sensitivity and obvious color change. It can sense hydrogen with a concentration as low as 200ppm at room temperature and has great application prospects in the fields of rail gas leakage monitoring and hydrogen storage equipment safety status monitoring.

[0056] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0057] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0058] Example 1

[0059] Step 1: Soak the polished commercial tungsten sheet in acetone, ethanol, and deionized water for ultrasonic cleaning for 15 minutes, and purge the cleaned tungsten sheet with a nitrogen gun to obtain a thoroughly cleaned tungsten sheet;

[0060] Step 2: Place two thoroughly cleaned tungsten sheets as anodes and cathodes in parallel in an electrolytic cell with a parallel distance of 1 mm. The electrolyte is 0.02 mol / L dilute hydrochloric acid. Apply a constant current of 0.35 A and a constant voltage of 35 V to the tungsten sheets to start anodization for 40 minutes. During this process, quantum tungsten oxide enters the electrolyte to obtain a quantum tungsten oxide solution with a concentration of 1.37 mol / L.

[0061] Step 3: Weigh potassium hypochloropalladate solid and dissolve it in deionized water to obtain a 0.37 mol / L potassium hypochloropalladate solution, mix it evenly with a 1.37 mol / L quantum tungsten oxide solution at a volume ratio of 1:8, and then place the mixed solution in a dark and ventilated environment under continuous stirring, and expose it to 254 nm ultraviolet light for 30 min (ultraviolet light irradiation power 12 W); then wash it alternately with deionized water and ethanol three times, and dry it (60-80 ° C) to obtain a-WO 3 / Pd quantum dots.

[0062] Figure 1 The a-WO in the quantum tungsten oxide solution prepared in Example 1 3 TEM image of Figure 1 It can be seen that the prepared tungsten oxide is an independent quantum dot with ultra-small particle size.

[0063] Figure 2 a-WO prepared in Example 1 3 TEM image of Pd / Pd quantum dots. Figure 2It can be seen that the Pd catalyst is successfully reduced and attached to the vicinity of tungsten oxide.

[0064] The a-WO prepared in this example 3 / Pd quantum dots were dissolved in ethanol solution (the concentration of ethanol solution was such that a-WO 3 / Pd quantum dots are fully dissolved) to obtain 3.21mol / L hydrogen-sensitive color-changing dye; the hydrogen-sensitive color-changing dye is dripped on the surface of the filter paper for three times, each time until the filter paper is completely wetted, and after each dripping, it is completely dried at 70°C (the drying temperature can be 60-70°C) to obtain a hydrogen-sensitive color-changing mark. The hydrogen-sensitive color-changing mark is verified for color change in hydrogen and bleaching in air. The results are as follows Figure 3 As shown. Figure 3 It can be seen that the sample can detect hydrogen as low as 200 ppm; the sample can respond quickly to 1% (v / v) hydrogen and completely change color in 20s. After the coloring state is stable (1% hydrogen), air is introduced, and it can be seen that the sample slowly bleached to its initial state.

[0065] Example 2

[0066] Step 1: After polishing the commercial tungsten sheet, immerse it in acetone, ethanol, and deionized water for ultrasonic cleaning for 15 minutes, and then blow the cleaned tungsten sheet clean with a nitrogen gun to obtain a thoroughly cleaned tungsten sheet;

[0067] Step 2: Place two thoroughly cleaned tungsten sheets in parallel in a transparent electrolytic cell with a parallel distance of 5 mm. The electrolyte is 0.02 mol / L dilute hydrochloric acid. Apply a constant voltage of 60 V to the tungsten sheets and maintain for 10 minutes. During this process, quantum tungsten oxide enters the electrolyte to obtain a quantum tungsten oxide solution with a concentration of 1.37 mol / L.

[0068] Step 3: Potassium hypochloropalladate is dissolved in deionized water to prepare a 0.37 mol / L potassium hypochloropalladate solution, which is mixed evenly with the 1.37 mol / L quantum tungsten oxide solution in step 2 at a volume ratio of 1:4, and then the mixed solution is placed in a dark ventilated environment under continuous stirring, exposed to an ultraviolet environment (ultraviolet light band 254 nm, irradiation power 12 W), and maintained for 30 minutes; then washed alternately with deionized water and ethanol three times, and dried (60-80°C) to obtain a-WO 3 / Pd quantum dots.

[0069] The a-WO prepared in this example 3 / Pd quantum dots and silica gel (food grade platinum silica gel, high transparent AB glue DRSGJ02) are mixed and stirred evenly in a mass ratio of 1:10, and the mixed colloid is cured to obtain hydrogen-sensitive color-changing flexible silica gel.

[0070] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a-WO3 / Pd quantum dots, characterized in that: The following steps are involved: The tungsten sheet is placed in an electrolyte as an anode for anodic oxidation to obtain a quantum tungsten oxide solution; Mixing the potassium hypochloropalladate solution with the quantum tungsten oxide solution to obtain a reaction solution; The reaction solution is irradiated with ultraviolet light to obtain the a-WO3 / Pd quantum dots.

2. The method for preparing a-WO3 / Pd quantum dots according to claim 1, characterized in that: The electrolyte is a hydrochloric acid aqueous solution with a pH value of 0.1-3.

3. The method for preparing a-WO3 / Pd quantum dots according to claim 1, characterized in that: The anodic oxidation is carried out under constant current or constant voltage conditions; the current range of the constant current is 0.02A to 5A; the voltage range of the constant voltage is 10V to 80V; and the time of the anodic oxidation is 1min to 240min.

4. The method for preparing a-WO3 / Pd quantum dots according to claim 1, characterized in that: The concentration of quantum tungsten oxide in the quantum tungsten oxide solution is 0.275 mol / L to 2.75 mol / L; the concentration of the potassium hypochloropalladate solution is 0.1 mol / L to 1 mol / L; the solvent of the potassium hypochloropalladate solution is water; the volume ratio of the potassium hypochloropalladate solution to the quantum tungsten oxide solution is 20:1 to 1:

20.

5. The method for preparing a-WO3 / Pd quantum dots according to claim 1, characterized in that: The wavelength of the ultraviolet light irradiation is 254nm, the power is 6-18W, and the time is 3min to 60min.

6. a-WO3 / Pd quantum dots prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the a-WO3 / Pd quantum dots as claimed in claim 6 in the preparation of hydrogen-sensitive color-changing products.

8. A hydrogen-sensitive color-changing dye, characterized in that: The raw materials include the a-WO3 / Pd quantum dots described in claim 6.

9. A method for preparing the hydrogen-sensitive color-changing dye according to claim 8, characterized in that: The method is prepared by dissolving a-WO3 / Pd quantum dots in a solvent.

10. A hydrogen-sensitive color-changing label, characterized in that: The raw materials include the a-WO3 / Pd quantum dots described in claim 6 or the hydrogen-sensitive color-changing dye described in claim 8.

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