Nano composite material capable of resisting temperature and humidity changes, preparation method of nano composite material, colorimetric sensor array and application of colorimetric sensor array

Abstract

The invention belongs to the technical field of gas sensing, and discloses a temperature and humidity change resistant nano composite material, a preparation method thereof, a colorimetric sensor array and application thereof. The preparation method of the nano composite material comprises the following steps: adding soluble palladium salt into a histidine solution, carrying out bidentate coordination complexation reaction on imidazole nitrogen, amino nitrogen and palladium ions, then adding SiO2 nano particles, stirring to obtain a gelatinous substance, and drying and grinding to obtain the nano composite material. On this basis, a colorimetric sensor array based on Wacker reaction and # imgabs0 # dye synergistic response is developed, the colorimetric sensor array comprises a sensing element and a substrate, the sensing element comprises a nano composite material and a modified dye, specific optical fingerprints are generated for ethylene with different concentrations by means of multi-molecule interaction, and qualitative and quantitative detection of 1-50 ppm ethylene is achieved. The method still keeps stable detection performance in an environment with severe fluctuation of temperature and humidity, and is of great significance.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensing, and particularly relates to a nanocomposite material resistant to temperature and humidity changes, a preparation method thereof, a colorimetric sensor array and an application thereof. Background Art

[0002] In the food industry and post-harvest agriculture, the real-time monitoring of ethylene is crucial for ensuring the freshness and quality of perishable commodities and helps to precisely control the storage of perishable commodities. In addition, ethylene is also an important plant hormone, which can provide important information for plant health, the ripening process and storage conditions. Therefore, ethylene detection is the cornerstone to promote our understanding of plant biology. Given the ubiquitous and multifaceted effects of ethylene, it is very important to find an accurate and reliable ethylene detection method under different concentrations and environmental conditions.

[0003] However, the practical application of traditional ethylene analysis methods is still limited by price and the lack of on-site deployment capabilities. To address these limitations, other sensing platforms have been explored, including electrochemical systems, electrochemical sensors, gravimetric sensors, fluorescence sensors and organic field-effect transistors. However, the application scope of these methods is often limited by complex manufacturing processes and limited environmental adaptability. Especially under the typical natural high temperature and high humidity conditions in agricultural storage facilities, the thermal stability and hydrolysis stability problems of traditional sensors often lead to technical bottlenecks. For example, the Adam Sklorz team at the University of Bremen in Germany developed a micro ethylene gas chromatography system based on a miniaturized preconcentrator, a silicon-based chromatographic column and a SnO2 detector. However, the preconcentration module of this system is significantly interfered by humidity, which will cause a strong humidity background signal. The Marcel A.G. Zevenbergen team at the Holst Centre in the Netherlands developed an ethylene electrochemical sensor using an ionic liquid as an electrolyte, with a detection limit of 760 ppb. However, this sensor shows obvious signal drift with the fluctuation of environmental humidity, and its performance significantly decreases with the accumulation of gold oxide during the detection process, and it cannot be widely used for ethylene detection under natural high temperature and high humidity conditions. Summary of the Invention

[0004] In order to overcome the disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a nanocomposite material resistant to temperature and humidity changes.

[0005] Another object of the present invention is to provide a preparation method of a nanocomposite material resistant to temperature and humidity changes.

[0006] Another object of the present invention is to provide a colorimetric sensor array, which is an emerging analytical technique that generates a composite optical fingerprint through different molecular interactions with the target analyte. Due to its inherent advantages such as low cost, simple operation, chemical stability, and visual readout function, it has great potential for ethylene detection and can solve the problems of obvious signal drift and performance degradation of existing sensors due to hydrothermal instability.

[0007] Another object of the present invention is to provide an application of the above colorimetric sensor array.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A nano-composite material resistant to temperature and humidity changes, denoted as Pd(Ⅱ) / His@SiO2, has the following structural formula:

[0010]

[0011] A preparation method of a nano-composite material resistant to temperature and humidity changes includes the following steps:

[0012] (1) Add soluble palladium salt to the histidine solution, and carry out a bidentate coordination complexation reaction between the imidazole nitrogen and amino nitrogen of histidine and palladium ions to obtain a solution of palladium-histidine composite material, denoted as Pd-His composite material solution;

[0013] (2) Add SiO2 nanoparticles to the Pd-His composite material solution, stir until evenly dispersed to obtain a gel-like substance, and after drying and grinding, obtain the nano-composite material Pd(Ⅱ) / His@SiO2 resistant to temperature and humidity changes.

[0014] Preferably, the molar ratio of the soluble palladium salt to histidine in step (1) is 1:0.4 - 2, and the concentration of the histidine solution is 0.0075 - 0.0375 mol / L;

[0015] The soluble palladium salt in step (1) is at least one of Pd(NO3)2, PdCl2, or Pd(SO4)2.

[0016] Preferably, the number of silicon-oxygen bond sites provided by SiO2 in step (2) is greater than the number required for the formation of hydrogen bonds between histidine and SiO2;

[0017] Preferably, the molar ratio of the SiO2 nanoparticles to the soluble palladium salt in step (2) is 1:10 - 30.

[0018] A colorimetric sensor array includes a sensing element and a substrate;

[0019] The sensing element includes the nanocomposite Pd(Ⅱ) / His@SiO2 and a modified dye;

[0020] The substrate is a hydrophobic paper-based membrane;

[0021] The sensing element constructs a colorimetric sensor array on the substrate in a 4×4 arrangement pattern, and the row spacing and column spacing are both 4 mm.

[0022] Preferably, the modified dye is a pH-responsive dye modified by tetrabutylammonium hydroxide (TBAH), and the molar ratio of tetrabutylammonium hydroxide (TBAH) to the pH-responsive dye is 1 to 4:1;

[0023] The substrate is a polypropylene film.

[0024] Preferably, the pH-responsive dye is bromophenol blue, methyl red, bromothymol blue, or methyl orange.

[0025] The application of the above colorimetric sensor array in ethylene detection and / or analysis.

[0026] Preferably, the application includes the following steps:

[0027] S1. Place the colorimetric sensor array in the target gas environment, use a scanner to obtain the RGB color maps before and after the array is exposed, calculate the ΔR, ΔG, and ΔB values of each sensing unit through a differential algorithm, and generate a color fingerprint response matrix;

[0028] S2. Use principal component analysis combined with hierarchical clustering analysis of the color fingerprint response matrix to achieve qualitative and quantitative detection of ethylene.

[0029] Preferably, the ethylene concentration is 1 - 50 ppm.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] 1. The method of the present invention utilizes the coordination of histidine (His) and Pd(II) and the hydrogen bond anchoring of SiO2 to double inhibit the hydrolysis and thermal decomposition of palladium salts, enabling the sensor to remain stable in harsh environments such as high temperature and high humidity, overcoming the problem of performance deterioration of traditional sensors caused by environmental fluctuations, and expanding the application scenarios of ethylene sensors.

[0032] 2. The present invention uses the Pd(Ⅱ) / His@SiO2 nanocomposite and the modified dye to synthesize the sensor element through simple compounding, without the need for complex equipment or high-temperature calcination, and the sensor is inexpensive, suitable for real-time visual detection and portable design, etc., and is suitable for large-scale agricultural monitoring scenarios.

[0033] 3. The present invention develops a method based on the Wacker reaction and Colorimetric sensor array with dye synergistic response, using A dual-color development system is constructed by using a composite system of dyes (BB, MR, BTB, MO) and Pd-His material, where The dye recognizes HNO3 generated by the Wacker oxidation of ethylene through acid response, and the reddish-brown Pd(II) is converted to black Pd(0) due to the Wacker oxidation, and the dual signals synergistically enhance the signal specificity.

[0034] 4. Use non-toxic silicon-based carrier (SiO2) and biocompatible histidine to avoid potential environmental pollution risks. Description of the Drawings

[0035] Figure 1 is a schematic diagram of the synthesis of Pd(II) / His@SiO2 nanocomposite;

[0036] Figure 2 is a schematic diagram of the preparation of the colorimetric sensor array;

[0037] Figure 3 is an infrared spectrum analysis chart of Pd(II) / His@SiO2 material;

[0038] Figure 4 is a comparison chart of the temperature and humidity stability of the colorimetric sensor array. (A) is the response fingerprint of the colorimetric sensor to 50 ppm ethylene at humidity gradients of 43%, 58%, 72% and 81% at 25 °C, and (B) is the response fingerprint of the colorimetric sensor to 50 ppm ethylene at temperature gradients of 25 °C, 40 °C, 55 °C and 70 °C at 60% humidity;

[0039] Figure 5 is a comparison chart of the temperature and humidity stability of Pd(NO3)2 and Pd(II) / His@SiO2 materials. (A) is the color change chart of the solution stored at room temperature for 30 days, and (B) is the color change chart of heat treatment at 25 °C and 60 °C for 24 hours;

[0040] Figure 6 is the HCA cluster analysis chart of ethylene concentration response;

[0041] Figure 7 is the PCA classification chart of ethylene concentration response;

[0042] Figure 8 is the change chart of the peel color and ethylene release amount during the banana ripening process. (A) to (G) represent 1 to 7 days respectively, and (H) is the change chart of ethylene release amount. Detailed Implementation Modes

[0043] The present invention will be further described in detail below in conjunction with embodiments. However, the implementation manners of the present invention are not limited thereto. For process parameters not specifically noted, reference may be made to conventional techniques.

[0044] Examples 1 - 6

[0045] As Figures 1 - 2 shown, this group of examples provides a method for preparing a nanocomposite material resistant to temperature and humidity changes, including the following steps:

[0046] Dissolve histidine (His) powders with different masses (0 g, 0.047 g, 0.094 g, 0.141 g, 0.188 g, 0.235 g) in 40 mL of deionized water. The resulting histidine solution concentrations are 0.0075 mol / L, 0.015 mol / L, 0.0225 mol / L, 0.03 mol / L, and 0.0375 mol / L. Stir for 24 hours at a speed of 360 rpm on a magnetic stirrer to prepare His solutions with different concentrations. Then weigh 6 portions of Pd(NO3)2 powder (0.175 g, 0.00076 mol) and add them to the above-mentioned His solutions with different concentrations respectively, to obtain Pd-His composite solutions with Pd(Ⅱ) to His molar ratios of 1:0, 1:0.4, 1:0.8, 1:1.2, 1:1.6, and 1:2, denoted as Pd-His-1-0, Pd-His-1-0.4, Pd-His-1-0.8, Pd-His-1-1.2, Pd-His-1-1.6, and Pd-His-1-2. Subsequently, add SiO2 nanoparticles (specific surface area 200 m 2 / g, 1.0 g, 0.0166 mol), and it is necessary to ensure that the number of siloxane bond sites provided by SiO2 is greater than the number required for histidine and SiO2 to form hydrogen bonds, and stir until it is evenly dispersed in the mixed solution to obtain a gel-like Pd / His@SiO2 composite material. Then dry the gel-like Pd / His@SiO2 at 60 °C for 24 hours. Finally, obtain Pd(Ⅱ) / His@SiO2 powder by grinding and sieving (80 mesh). As shown by infrared spectroscopy Figure 3 shown, the results indicate that the FTIR spectra of all samples show the bands of SiO2. Specifically, a Si-O symmetric stretching vibration peak appears at 799 cm -1 , and a broad Si-O-Si antisymmetric stretching vibration peak is detected near 1095 cm -1 . According to the hydrogen bond theory, strong hydrogen bond interactions will average the electron cloud density and increase the bond length. Therefore, when a strong hydrogen bond interaction is formed, the wavelength of the O-H stretching vibration will become smaller. According to this principle, the O-H stretching vibration peak (3200 - 3300 cm -1) The redshift indicates that with the increase of His loading amount, the interfacial hydrogen bonding in the material is enhanced, confirming the formation of hydrogen bond connection between His and the SiO2 support. The characteristic band analysis shows that the absorption band at 1729 cm -1 is attributed to the stretching vibration of C=O, the absorption band near 1633 cm -1 corresponds to the bending vibration peak of NH3, while the absorption band near 1396 cm -1 corresponds to the stretching vibration peak of NO3 - , and the signal intensities of all three are positively correlated with the His loading amount. The above results show that the His ligand can improve the hydrolysis resistance of Pd(NO3)2 and synergistically inhibit the hydrolysis process of Pd(NO3)2 by forming a hydrogen bond network with SiO2, thereby enhancing the structural stability of the Pd(Ⅱ) / His@SiO2 material. Therefore, the above Pd(Ⅱ) / His@SiO2 powder can be used in the following experiments.

[0047] Test Example 1

[0048] The hydrolysis stabilities of Pd(NO3)2 and six Pd(Ⅱ) / His@SiO2 materials were monitored by monitoring the color change, specifically as follows:

[0049] Dissolve Pd(NO3)2 (0.175 g) in 40 mL of water, and then dissolve six groups of Pd(Ⅱ) / His@SiO2 materials containing equal mass (0.175 g) of Pd(NO3)2 powder in Examples 1-6 above in 40 mL of water. Subsequently, the prepared aqueous solutions of Pd(NO3)2 and Pd(Ⅱ) / His@SiO2 materials were stored at room temperature for 30 d, and the color changes of the aqueous solutions of Pd(NO3)2 and Pd(Ⅱ) / His@SiO2 materials were observed and recorded. In addition, Pd(NO3)2 and Pd(Ⅱ) / His@SiO2 materials were stored under vacuum conditions at 60 °C for 24 hours, and the color changes were observed and recorded to study their thermal stabilities. After hydrolysis treatment and pyrolysis treatment, Pd(NO3)2 and Pd(Ⅱ) / His@SiO2 materials showed different color stabilities, among which Pd-His-1-0.8 had the most stable color and could be used for the preparation of a colorimetric sensor.

[0050] Example 7

[0051] This example provides a visual ethylene colorimetric sensor array. In order to visualize the reaction of the sensor element to ethylene, a pH-sensitive dye was used to detect the acid generated during the reduction process. The specific preparation steps of the colorimetric sensor array are as follows:

[0052] The colorimetric sensor array uses a polypropylene film as the substrate and is arranged in a 4×4 configuration, with a total of 16 sensing elements, as shown in Figure 2As shown. Each sensing element is composed of the optimal molar ratio of Pd-His-1-0.8 and Brilliant dye. Before printing the sensing element, the Brilliant dye solution is first modified with tetrabutylammonium hydroxide (TBAH) at the optimal molar ratio (the molar ratio of TBAH to the dye is 1:1, 2:1, 3:1, and 4:1). TBAH deprotonates the ester group and phenolic group of the Brilliant dye, changing the sensitivity of the dye to acid. By changing the amount of TBAH, different modified ratios of the same dye can have different color responses to ethylene at the same concentration, that is, a color gradient. Subsequently, the sensor array is dried at room temperature for 1 hour to prepare a colorimetric sensor array, and then a sensing experiment is carried out.

[0053] Among them, the detailed codes and corresponding manufacturing information of the sensing elements are shown in Table 1. BB is bromophenol blue, MR is methyl red, BTB is bromothymol blue, MO is methyl orange. After that, a colorimetric sensor array is prepared and then a sensing experiment is carried out.

[0054] Table 1

[0055]

[0056] Test Example 2

[0057] To evaluate the stability of the colorimetric sensor array to humidity and temperature, the color changes of the colorimetric sensor array after storage under different relative humidity and temperature conditions were measured. Specifically, different supersaturated salt solutions (K2CO3, NaBr, (NH4)2SO4, and CON2H4) were prepared at 25 °C to form a humidity gradient from 43% RH to 81% RH. Then the array was stored at different humidities for 24 hours to test the humidity stability. Subsequently, the array was stored at five gradient temperatures (25 °C, 40 °C, 55 °C, and 70 °C) and 60% relative humidity for 24 hours to test the temperature stability.

[0058] As Figure 4 shown, since both the sensor array elements and the substrate are made of materials that do not respond to temperature and humidity, the sensor is not affected by temperature and humidity changes. At four humidity gradients of 43%, 58%, 72%, and 81%, the response fingerprints of the colorimetric sensor to 50 ppm ethylene are almost the same ( Figure 4 A), and at temperature gradients of 25 °C, 40 °C, 55 °C, and 70 °C, there is also no difference in the response fingerprints to 50 ppm ethylene ( Figure 4 B), which indicates that the sensor has temperature and humidity stability and is expected to be used under natural extreme environmental conditions.

[0059] Application Example 1

[0060] The quantitative analysis of the colorimetric sensor array for commercially available ethylene gas of a determined concentration is carried out as follows:

[0061] The colorimetric sensor array is fixed on the inner top of a sealed 500 mL container to monitor ethylene gas, and ethylene gas of the required concentrations (50 ppm, 30 ppm, 20 ppm, 10 ppm, 2 ppm, and 1 ppm) is uniformly injected into the system. A flatbed scanner (CanoScan LiDE 300, Canon Inc.) is used to record the RGB image changes of the colorimetric sensor array before and after exposure. The ΔR, ΔG, and ΔB values of each sensing unit are calculated through a differential algorithm (see Equation 1), generating a color fingerprint response matrix. Ethylene is quantitatively analyzed by analyzing the fingerprint response matrix generated by the colorimetric sensor for ethylene of different concentrations.

[0062] ΔR = |R 前 - R 后 |

[0063] ΔG = |G 前 - G 后 |

[0064] ΔB = |B 前 - B 后 | (1)

[0065] Wherein, R 前 、G 前 、B 前 respectively represent the numerical values of the R, G, and B channels before the reaction, and R 后 、G 后 、B 后 respectively represent the numerical values of the R, G, and B channels after the reaction.

[0066] As Figure 6 shown, the data set is subjected to cluster analysis through HCA (Hierarchical Cluster Analysis). The HCA cluster tree shows that the sensor has a clear and unmistakable clustering for ethylene gas of six concentration gradients, indicating the ability of the sensor to distinguish ethylene gas of different concentrations.

[0067] As Figure 7 shown, the data set is further analyzed through PCA (Principal Component Analysis). The results show that there is a clear distinction between the six concentration gradients of ethylene without confusion.

[0068] Application Example 2

[0069] This application example applies the colorimetric sensor array to the detection of ethylene content during the ripening process of bananas. Based on the clustering samples in Application Example 1, the specific operation steps are as follows:

[0070] To simulate a commercial storage scenario, the bananas are neatly arranged in a ventilated corrugated cardboard box (40×30×25 cm). Then, the cardboard box containing the bananas is placed in an incubator at a temperature of 25 ± 1 °C and a relative humidity of 60 ± 5%, and stored for 7 days. For ethylene quantification, three replicates of banana clusters are sealed in airtight polyethylene bags (22×32 cm) for 2 hours of headspace accumulation, and then the change in the endogenous ethylene release amount of the bananas is measured using a commercially available ethylene detector. At the same time, the images of the colorimetric sensor array are recorded every day, the images are analyzed to obtain the change in the endogenous ethylene release amount of the bananas, and the results are compared with the detection results of the ethylene detector.

[0071] Due to the instability of Pd(NO3)2, it quickly hydrolyzes, turns black, and precipitates in solution, thus unable to support Pd(NO3)2 as a colorimetric sensor.

[0072] As Figure 8 shown, the change in the banana peel color is closely related to ethylene biosynthesis, showing the characteristics of climacteric fruits. At the same time, the colorimetric sensor array and the ethylene detector show significant consistency, verifying its reliability in in-situ monitoring of ethylene and being able to remain stable in an environment with a humidity of 60 ± 5%.

[0073] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A nano-composite material resistant to temperature and humidity changes, characterized in that, The nano-composite material resistant to temperature and humidity changes is denoted as Pd(Ⅱ) / His@SiO2, and its structural formula is as follows:

2. A method for preparing the nano-composite material resistant to temperature and humidity changes according to claim 1, characterized in that, It includes the following steps: (1) Add soluble palladium salt into the histidine solution, and conduct a bidentate coordination complexation reaction between the imidazole nitrogen and amino nitrogen of histidine and palladium ions to obtain a solution of palladium-histidine composite material, denoted as Pd-His composite material solution; (2) Add SiO2 nanoparticles into the Pd-His composite material solution, stir until evenly dispersed to obtain a gel-like substance, and after drying and grinding, obtain the nano-composite material Pd(Ⅱ) / His@SiO2 resistant to temperature and humidity changes.

3. The preparation method of the nano-composite material resistant to temperature and humidity changes according to claim 2, characterized in that, In step (1), the molar ratio of the soluble palladium salt to histidine is 1:0.4 - 2, and the concentration of the histidine solution is 0.0075 - 0.0375 mol / L; The soluble palladium salt in step (1) is at least one of Pd(NO3)2, PdCl2 or Pd(SO4)2.

4. The preparation method of the nano-composite material resistant to temperature and humidity changes according to claim 2, characterized in that, In step (2), the molar ratio of the SiO2 nanoparticles to the soluble palladium salt is 1:10 - 30.

5. A colorimetric sensor array, characterized in that, It includes a sensing element and a substrate; The sensing element includes the Pd(Ⅱ) / His@SiO2 described in claim 1 and a modified dye; The substrate is a hydrophobic paper-based membrane; The sensing element is arranged in a 4×4 array pattern on the substrate to construct a colorimetric sensor array.

6. The colorimetric sensor array according to claim 5, characterized in that, The modified dye is a pH-responsive dye modified by tetrabutylammonium hydroxide, and the molar ratio of tetrabutylammonium hydroxide to the pH-responsive dye is 1 - 4:1; The substrate is a polypropylene film.

7. The colorimetric sensor array according to claim 6, wherein The pH-responsive dye is bromophenol blue, methyl red, bromothymol blue, methyl orange.

8. The application of the colorimetric sensor array according to any one of claims 5 - 7 in the detection and / or analysis of ethylene.

9. The application according to claim 8, wherein It includes the following steps: S1. Place the colorimetric sensor array in the target gas environment, use a scanner to obtain the RGB color maps before and after the array is exposed, calculate the ΔR, ΔG, ΔB values of each sensing unit, and generate a color fingerprint response matrix; S2. Use principal component analysis combined with hierarchical cluster analysis of the color fingerprint response matrix to achieve qualitative and quantitative detection of ethylene.

10. The application according to claim 8, characterized in that, The ethylene concentration is 1 - 50 ppm.

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