Preparation method and application of ultraviolet degradable and functionalized cellulose paper primary color sensitive sensor

Abstract

The invention belongs to the technical field of color-sensitive sensing technology and nondestructive testing of food and agricultural products, and particularly relates to a preparation method and application of an ultraviolet degradable and functionalized cellulose paper color-sensitive sensor. The preparation method comprises the following steps: firstly, preparing a TiO2 cellulose paper base and TiO2 / OTS functional cellulose filter paper; then combining with a color-sensitive material to obtain a color-sensitive sensor; a food quality evaluation model is established based on the color-sensitive sensor, and rapid evaluation of food quality is realized. TiO2 is loaded on the surface of the prepared paper-based color-sensitive sensor, and color-sensitive dye can be effectively degraded based on the photocatalysis of the TiO2 layer; the paper base is provided with a hydrophilic sample application area and a hydrophobic isolation area; the isolation area can effectively isolate the mutual influence of the color-sensitive units, and the moisture resistance and stability of the sensor are improved. The prepared color-sensitive sensor is high in moisture resistance, good in stability and good in environmental compatibility, can be applied to rapid detection of food quality, and has good application prospects and use value.

Description

Technical Field

[0001] The invention belongs to the field of color-sensitive sensing detection technology and non-destructive detection technology of food and agricultural products, and specifically relates to a preparation method and application of an ultraviolet-degradable, functionalized cellulose paper-based color-sensitive sensor. Background Art

[0002] Volatile organic compounds in food refer to a class of chemical substances in food that can evaporate into the air, which has an important impact on food quality. Monitoring volatile organic compounds in food can evaluate food quality and promptly warn of quality problems that may exist in food processing or storage. By timely monitoring and controlling the volatile components of food, the flavor characteristics and product quality of the food can be ensured, and consumer satisfaction and product market competitiveness can be improved. Therefore, it is of great significance to monitor the volatile components of food.

[0003] Gas chromatography or gas chromatography-mass spectrometry is a conventional method for detecting volatile components. This method has complex pretreatment and high detection cost, and is not suitable for on-site detection. The color-sensitive sensing detection technology of volatile components is developed based on the olfactory perception principle of mammals. It has the characteristics of fast response speed, low cost and strong portability, and is widely used in the detection of volatile components. At present, there are still some problems in the practical application of color-sensitive sensors. Paper-based materials, as common flexible materials for the preparation of color-sensitive sensors, have the advantages of convenient use, good biocompatibility and low cost, and are favored by researchers. However, in the process of using paper-based color-sensitive sensors, the inherent hydrophilicity of filter paper will cause the colorimetric response signal to drift, which seriously hinders its practical application; and the strong capillary force between color-sensitive units will cause uneven diffusion of the solution, causing the sensing units to affect each other, resulting in poor stability in the production of color-sensitive sensors. Color-sensitive dyes such as metal porphyrins, fluoroboryl pyrroles, and pH indicators are the core materials for making sensors, and the use of these substances will cause environmental pollution. With the development of society, human environmental awareness has gradually increased. The development of degradable substrates for the construction of color-sensitive sensors can avoid secondary pollution and is of great significance to environmental protection. Summary of the invention

[0004] In view of the problems of poor stability and low moisture resistance in the production of color-sensitive sensors, the present invention proposes to produce a paper-based material for functionalized fiber filter paper, which has a hydrophilic color-sensitive spot area and a hydrophobic isolation area. The large area of ​​the hydrophobic area can effectively isolate the filter paper from absorbing moisture in the environment, and the prepared color-sensitive sensor has stronger moisture resistance; at the same time, the isolation area can effectively isolate the mutual influence between the color-sensitive units, and the prepared color-sensitive sensor has better stability. In view of the problem of possible environmental pollution, the present invention proposes to produce a paper-based material with TiO2 photocatalytic properties; when the paper-based material is used to prepare a color-sensitive sensor, the dye on the color-sensitive sensor can be degraded by ultraviolet irradiation, and the prepared color-sensitive sensor has better environmental compatibility. The paper-based color-sensitive sensor solves the technical problems of high detection cost, poor repeatability, weak moisture resistance, complex detection process, and dye pollution in the prior art.

[0005] In order to achieve the above object, the specific steps of the present invention are as follows:

[0006] A method for preparing a UV-degradable, functionalized cellulose paper-based color-sensitive sensor comprises the following steps:

[0007] Step 1, preparation of TiO2 cellulose paper base:

[0008] Cut the filter paper according to the needs and soak it in anhydrous ethanol (to clean and activate the hydroxyl groups on the surface of the cellulose structure). After soaking, take out the filter paper and dry it to obtain dry filter paper; mix anhydrous ethanol, butyl titanate and glacial acetic acid to obtain a mixed solution, and soak the dry filter paper in the mixed solution, then place it on a shaker for shaking reaction, and take out the filter paper after the reaction to dry it; after drying, soak the filter paper in the mixed solution again, repeat the soaking, shaking reaction and drying steps several times, take out the filter paper and place it in deionized water for hydrolysis, and obtain TiO2 cellulose filter paper after hydrolysis;

[0009] Step 2, preparation of TiO2 / OTS functionalized cellulose filter paper:

[0010] The TiO2 cellulose filter paper obtained in step 1 is immersed in a mixed solution of octadecyltrichlorosilane and n-hexane (OTS), taken out after soaking, and then washed with n-hexane and anhydrous ethanol respectively, and then dried after washing to obtain TiO2 / OTS cellulose filter paper;

[0011] Then, a glass cover is placed on the TiO2 / OTS cellulose filter paper and exposed to ultraviolet light for a period of time. After exposure, the cellulose filter paper is cleaned with anhydrous ethanol to obtain a TiO2 / OTS functionalized cellulose filter paper having a circular hydrophilic color-sensitive spot area and a hydrophobic isolation area; the cover plate has the same area as the TiO2 / OTS cellulose filter paper, and is provided with a number of circular holes distributed at equal intervals;

[0012] Step 3: Preparation of UV-degradable, functionalized cellulose paper-based colorimetric sensor:

[0013] First, a color-sensitive material solution is prepared; then the color-sensitive material solution is dripped onto the circular hydrophilic spotting area of ​​the TiO2 / OTS functionalized cellulose filter paper prepared in step 2 to prepare a UV-degradable, functionalized cellulose paper-based color-sensitive sensor;

[0014] Preferably, the filter paper in step 1 is a qualitative filter paper with a size of 30-40mm*30-40mm; the filter paper is soaked in anhydrous ethanol for 3-6h; the drying temperature of the filter paper is 30-50°C, and the drying time does not exceed 20min;

[0015] Preferably, in step one, the volume ratio of anhydrous ethanol, butyl titanate and glacial acetic acid is 10:3:1, the shaking reaction speed of the shaking table is 180-200r / min, and the shaking reaction time is 30-60min; the soaking, shaking reaction and drying steps are repeated 3-5 times; the hydrolysis temperature is 85-95°C, and the hydrolysis time is 2-5h.

[0016] Preferably, in step 2, the volume ratio of octadecyltrichlorosilane to n-hexane is 1000:1, and the soaking time is 5-10 min; the number of cleaning times using n-hexane and anhydrous ethanol is 3-5 times; the drying temperature is 30-50° C., and the drying time does not exceed 20 min;

[0017] Preferably, the cover plate in step 2 is a rectangular parallelepiped, and its length, width and thickness are 39 mm, 39 mm and 4 mm respectively, the distance between the centers of adjacent circular holes is 9 mm, and the diameters of the circular holes are all 6 mm.

[0018] The ultraviolet lamp is an ultraviolet lamp with dual emission wavelengths of 185 and 254 nm; the cover plate is below the ultraviolet lamp, and the distance between the ultraviolet lamp and the glass cover plate is 1-2 cm, and the irradiation time is 40-60 min; after the TiO2 / OTS cellulose filter paper is irradiated by the ultraviolet lamp, the area covered by the cover plate is not degraded by ultraviolet irradiation, forming a hydrophobic isolation area; after the TiO2 / OTS cellulose filter paper in the circular hole area is irradiated by ultraviolet light, OTS decomposes, and a circular hydrophilic spot area with a diameter of 6 mm is formed on the TiO2 / OTS cellulose filter paper.

[0019] Preferably, the color-sensitive solution in step 3 is prepared in X types, X is a positive integer, and the X color-sensitive solutions are composed of solution A or / and solution B; wherein solution A is a dichloromethane solution of metal porphyrin or fluoroborylpyrrole, and solution B is an ethanol solution of a pH indicator; wherein the amount ratio of metal porphyrin or fluoroborylpyrrole to dichloromethane in solution A is 2 mg:1 mL; and the amount ratio of pH indicator to ethanol in solution B is 2 mg:1 mL;

[0020] The metal porphyrin includes tetraphenylporphyrin manganese; the fluoroboryl pyrrole includes 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoboron dipyrromethane; the pH indicator includes bromothymol blue, bromocresol green, methyl red, bromophenol blue, cresol red, chlorophenol red, and aniline violet;

[0021] Preferably, the amount of the color-sensitive dye solution added dropwise onto the TiO2 / OTS functionalized cellulose filter paper in step three is 1.5-2 μL.

[0022] The UV-degradable, functionalized cellulose paper-based color-sensitive sensor prepared by the present invention is applied to food quality monitoring, and the steps are as follows:

[0023] (1) Establishment of food quality evaluation model:

[0024] S1. Selecting a sample, where different quality levels of the sample correspond to different volatile odor substances, and different volatile odor substances will cause the color-sensitive sensor to produce different color changes; the sample includes a tea sample;

[0025] S2. First, use a camera to obtain an image of the ultraviolet degradable cellulose-based color-sensitive sensor before the reaction; then place the sample in a reaction container, and store the color-sensitive sensor and the sample in the same closed reaction container, so that the color-sensitive sensor and the volatile odor substances in the sample can fully react for a period of time; after the reaction, use a camera to obtain an image of the nano color-sensitive sensor after the reaction, and save the obtained image in a computer; use a computer to locate the position of the color-sensitive unit in the image before and after the reaction, extract its color characteristics, and make a difference between the grayscale means of each color-sensitive unit before and after the reaction, and the difference in the grayscale means is the characteristic variable of the color-sensitive unit;

[0026] The characteristic variables contained in all samples are combined to obtain a characteristic matrix, and a long short-term memory recurrent neural network (LSTM) model for food quality evaluation is constructed with the characteristic matrix as input and the quality grade of the test sample as output, which is the food quality evaluation model;

[0027] (2) Rapid monitoring and evaluation of food quality:

[0028] The sample to be tested is reacted according to the method described in (1) to obtain characteristic variables; the characteristic variables of the sample to be tested are brought into the LSTM model constructed in (1) to obtain the quality grade information of the sample to be tested, thereby realizing rapid evaluation of food quality.

[0029] Preferably, the amount of sample used in S2 of step (1) is 0.5-1.5 g, the reaction time is 10-30 min; and the color-sensitive sensor is fixed on the top of the reaction container.

[0030] Preferably, the feature variable extraction step in S2 of step (1) is as follows: using a computer to locate the position of each color-sensitive unit of the color-sensitive sensor; decomposing the image of the color-sensitive sensor before and after the camera acquires the reaction into R channel, G channel and B channel grayscale images, and extracting the hue (Hue, denoted as H), saturation (Saturation, denoted as S), brightness (Value, denoted as V), color brightness (denoted as L), red-green value (denoted as a) and yellow-blue value (denoted as b) of the image;

[0031] The R, G, B, H, S, V, L, a, and b of each sensitive unit before and after the reaction are subtracted, and the corresponding differences are recorded as △R, △G, △B, △H, △S, △V, △L, △a, and △b respectively; and according to Calculate the Euclidean distance; △R, △G, △B, △H, △S, △V, △L, △a, △b and ED are the characteristic variables of a color-sensitive unit, and X color-sensitive units obtain Y characteristic variables, where Y=10X.

[0032] Preferably, in S2 of step (1), the number of samples used to construct the food quality evaluation model is selected to be N, including n processing levels, m samples for each level, that is, N=n*m; n is a positive integer not less than 2, and m and N are both positive integers.

[0033] Preferably, the steps for establishing the food quality evaluation model in S2 of step (1) are as follows: the feature matrix is ​​denoted as S, S is N*Y, where N is the number of samples and Y is the feature variable contained in X color-sensitive units; the input feature variable matrix S is calculated by the LSTM unit to generate a hidden state matrix H; then the hidden state matrix H is selectively mapped to an output matrix H' through a fully connected layer, where H' is f(W h *H+b h ), where f is the activation function, W h is the weight matrix, b h Bias variables (optimize model parameters by minimizing the error between the predicted output matrix H' and the actual label, including the weight matrix inside the LSTM unit and the weight matrix W of the fully connected layer h and the bias variable b h ).

[0034] The sample corresponding product matrix T is used as the output value to construct the LSTM model for food quality evaluation;

[0035] Preferably, the rapid evaluation step of food quality in step (2) is as follows: according to the method described in step (1), Y feature variables of M samples to be tested are obtained to form a feature variable matrix R, where R is an M*Y matrix; the LSTM evaluation model constructed in step (1) is called, and the feature matrix R is used as an input value, and the output value Q corresponds to the processing degree information corresponding to the M samples to be tested, thereby realizing rapid evaluation of food quality.

[0036] The present invention discloses the following technical effects:

[0037] (1) The present invention discloses a method for preparing a UV-degradable cellulose-based colorimetric sensor and a method for rapidly evaluating food quality. The present invention focuses on overcoming the technical difficulties of high detection cost, weak sensor stability, complex detection process, and environmental pollution caused by dyes, and realizes rapid evaluation of food quality by obtaining information on volatile components of food.

[0038] (2) The present invention selects fiber filter paper as the substrate and loads TiO2 on the surface of the fiber filter paper to prepare a photocatalytic layer, thereby promoting photocatalytic degradation of the color-sensitive dye under ultraviolet light, improving the environmental performance of the color-sensitive sensor, and greatly improving the modification efficiency of the fiber filter paper.

[0039] (3) The present invention prepares a plurality of hydrophilic color-sensitive spot areas isolated by hydrophobic areas by modifying OTS on the surface of fiber filter paper and combining it with ultraviolet irradiation. The plurality of spot areas do not interfere with each other, thereby enhancing the preparation stability and moisture resistance of the paper-based sensor.

[0040] (4) The long short-term memory recursive neural network (LSTM) model for rapid evaluation of food quality established in the present invention has time series characteristics. It uses the signal value collected by the color-sensitive sensor as input and the processing degree of the food as output to establish a food quality evaluation model. It has good versatility and improves the efficiency of quality evaluation, which is of great significance for the evaluation of food quality during the processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The scanning electron microscope image (a) and EDS spectrum (b) of TiO2 cellulose filter paper;

[0042] Figure 2 This is the time optimization diagram for modifying the surface of TiO2 cellulose filter paper with OTS;

[0043] Figure 3 The scanning electron microscope image (a) and EDS spectra (b) and (c) of TiO2 / OTS cellulose filter paper;

[0044] Figure 4 Schematic diagram of a glass cover plate and ultraviolet irradiation (a) and a schematic diagram of a hydrophilic spotting area and a hydrophobic spotting area formed after ultraviolet irradiation (b);

[0045] Figure 5 This is the functional modification time optimization diagram of TiO2 / OTS functionalized cellulose filter paper;

[0046] Figure 6 Comparison diagram of color-sensitive sensors made from TiO2 / OTS functionalized cellulose filter paper and ordinary filter paper;

[0047] Figure 7 Comparative diagram of the moisture resistance of color-sensitive sensors made of ordinary filter paper (a) and TiO2 / OTS functionalized cellulose filter paper (b);

[0048] Figure 8 The LSTM discrimination results of the withering degree of tea leaves in Example 2: training set (a) and prediction set (b);

[0049] Fig. 9 This is a graph showing the UV degradation efficiency of the UV-degradable, functionalized cellulose paper-based color-sensitive sensor produced in Example 2. DETAILED DESCRIPTION

[0050] 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.

[0051] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art in the art to which the present invention relates.

[0052] Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0053] It will be apparent to those skilled in the art that many modifications and variations can be made to the particular embodiments of the invention described herein without departing from the scope or spirit of the invention.

[0054] Other embodiments will be apparent to the skilled person from the description of the present invention.The description and examples of the present invention are intended to be exemplary only.

[0055] Embodiment 1:

[0056] A method for preparing a UV-degradable, functionalized cellulose paper-based color-sensitive sensor mainly comprises the following steps:

[0057] Step 1: First, cut the qualitative filter paper into a size of 40*40 mm and soak it in anhydrous ethanol for 3 hours to clean and activate the hydroxyl groups on the surface of the cellulose structure. Then take out the fiber filter paper and dry it in an oven at 50°C for 15 minutes to obtain dry filter paper;

[0058] Subsequently, anhydrous ethanol, butyl titanate, and glacial acetic acid were used to prepare a mixed solution in a volume ratio of 10:3:1, and the obtained dry filter paper was then immersed in the mixed solution and placed on a shaker at a speed of 190 r / min for a shake reaction for 30 minutes. After the reaction, the filter paper was taken out and dried in an oven at 50°C for 15 minutes, and then immersed in the mixed solution again after drying. The immersion and drying steps were repeated 3 times to obtain a cellulose filter paper that fully adsorbed butyl titanate.

[0059] Finally, the cellulose filter paper fully adsorbed with butyl titanate was placed in ultrapure water at 95° C. for hydrolysis for 5 h, and the TiO2 cellulose paper base was obtained after sufficient hydrolysis.

[0060] Figure 1 This is the scanning electron microscope image and EDS spectrum of TiO2 cellulose filter paper; Figure 1 It can be seen from Figure a that the surface and pores of the filter paper fibers are filled with substances. Figure 1 The EDS spectrum in Figure b shows that the substance filling the surface and pores of the filter paper fibers is TiO2; this result shows that TiO2 has been successfully loaded on the surface of the fiber filter paper.

[0061] Step 2: firstly, octadecyltrichlorosilane and n-hexane are mixed to obtain a mixed solution, wherein the volume ratio of octadecyltrichlorosilane to n-hexane is 1000:1;

[0062] Secondly, the TiO2 cellulose filter paper was immersed in a n-hexane solution of octadecyltrichlorosilane for 5 min, and washed with n-hexane and anhydrous ethanol for 3 times respectively, and then dried at room temperature to obtain the TiO2 / OTS cellulose filter paper;

[0063] Finally, a glass cover was placed on the TiO2 / OTS cellulose filter paper, and it was placed under a 185 / 254nm dual-emission wavelength ultraviolet lamp at a position of 2 cm for irradiation for 30 minutes. The cellulose filter paper was then cleaned with anhydrous ethanol to obtain a TiO2 / OTS functionalized cellulose filter paper with a circular hydrophilic color-sensitive spot area and a hydrophobic isolation area. The cover was a rectangular parallelepiped with a length, width and thickness of 39 mm, 39 mm and 4 mm, respectively. The center spacing of adjacent circular holes was 9 mm, and the diameter of the circular holes was 6 mm. The circular holes were all inside the cover, that is, they did not intersect with the side length. The distance from the center of any circular hole close to the four sides of the cover to the nearest side of the cover was 6 mm.

[0064] Figure 2 It is the time optimization diagram of TiO2 cellulose filter paper surface modified with OTS. It can be seen from the figure that with the extension of treatment time, the surface tension of the filter paper decreases and the contact angle increases. When the treatment time reaches 5 minutes, the surface tension and contact angle of the filter paper basically tend to be stable, that is, the optimal time for TiO2 cellulose filter paper surface modified with OTS is 5 minutes.

[0065] Figure 3 This is the scanning electron microscope image and EDS spectrum of TiO2 / OTS cellulose filter paper; Figure 3 Figure a shows that many chemical substances grow on the surface and holes of the filter paper fibers. Figure 3 The EDS spectra in b and c show that the substances filling the surface and pores of the filter paper fibers are TiO2 and OTS; this result shows that TiO2 and OTS have been successfully loaded on the surface of the fiber filter paper and the filter paper has been successfully hydrophobically modified.

[0066] Figure 4 a is a schematic diagram of a glass cover plate and ultraviolet irradiation, and b is a schematic diagram of a hydrophilic spotting area and a hydrophobic spotting area formed after ultraviolet irradiation; Figure 4 Figure a shows the arrangement and diameter parameters of the circular holes in the glass cover, as well as the distance parameters between the UV lamp and the glass mask during UV irradiation. Figure 4 In Figure b, we can see that the TiO2 / OTS cellulose filter paper covers the cover plate. After irradiation with ultraviolet light, a TiO2 / OTS cellulose functionalized filter paper with a hydrophilic color-sensitive spot area and a hydrophobic isolation area is formed.

[0067] Figure 5 This is the functional modification time optimization diagram of TiO2 / OTS functionalized cellulose filter paper. It can be seen from the figure that with the extension of UV treatment time, the surface tension of the filter paper increases and the contact angle decreases. After 30 minutes of UV irradiation, the surface tension and contact angle of the filter paper basically tend to be stable, that is, the optimal time for functional modification of TiO2 / OTS functionalized cellulose filter paper is 30 minutes.

[0068] Step 3: First, eight color-sensitive solutions are prepared, which are composed of one dichloromethane solution of fluoroboryl pyrrole, one dichloromethane solution of metalloporphyrin, and six ethanol solutions of pH indicators;

[0069] The eight color-sensitive solutions are respectively named color-sensitive solution A (S1), color-sensitive solution B (S2), color-sensitive solution C (S3), color-sensitive solution D (S4), color-sensitive solution E (S5), color-sensitive solution F (S6), color-sensitive solution G (S7) and color-sensitive solution H (S8);

[0070] The color-sensitive solution A is a dichloromethane solution of 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoborondipyrrolmethane, and the amount ratio of dichloromethane of 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoborondipyrrolmethane is 20 mg:10 mL;

[0071] Color-sensitive solution B is a dichloromethane solution of tetraphenylporphyrin manganese, and the dosage ratio of tetraphenylporphyrin manganese to dichloromethane is 20 mg:10 mL;

[0072] Color-sensitive solution C is an ethanol solution of bromothymol blue, and the dosage ratio of bromothymol blue to ethanol is 20 mg:10 mL;

[0073] Color-sensitive solution D is an ethanol solution of bromocresol green, and the dosage ratio of bromocresol green to ethanol is 20 mg:10 mL;

[0074] Color-sensitive solution E is an ethanol solution of methyl red, and the dosage ratio of methyl red to ethanol is 20 mg:10 mL;

[0075] Color-sensitive solution F is an ethanol solution of bromophenol blue, and the dosage ratio of bromophenol blue to ethanol is 20 mg:10 mL;

[0076] Color-sensitive solution G is an ethanol solution of cresol red, and the dosage ratio of cresol red to ethanol is 20 mg:10 mL;

[0077] The color-sensitive solution H is an ethanol solution of aniline violet, and the dosage ratio of aniline violet to ethanol is 20 mg:10 mL;

[0078] Finally, 1.5 μL of the color-sensitive solution was aspirated using a microcapillary and fixed on the hydrophilic color-sensitive spot area of ​​the TiO2 / OTS functionalized cellulose filter paper to obtain a color-sensitive sensor based on the TiO2 / OTS functionalized cellulose filter paper, which is a UV-degradable, functionalized cellulose paper-based color-sensitive sensor.

[0079] Figure 6This is a comparison diagram of color-sensitive sensors made of TiO2 / OTS functionalized cellulose filter paper and ordinary filter paper; as can be seen from the figure, the color-sensitive sensor prepared with TiO2 / OTS functionalized cellulose filter paper has a lower coefficient of variation, indicating that the color-sensitive sensor prepared with TiO2 / OTS functionalized cellulose filter paper has better stability.

[0080] Figure 7 This is a comparative diagram of the moisture resistance of color-sensitive sensors made of ordinary filter paper (a) and TiO2 / OTS functionalized cellulose filter paper; it can be seen from the figure that under the same humidity environment, the response value of the color-sensitive sensor prepared by TiO2 / OTS functionalized cellulose filter paper is lower, indicating that the color-sensitive sensor prepared by TiO2 / OTS functionalized cellulose filter paper has stronger moisture resistance.

[0081] Embodiment 2:

[0082] The use of a UV-degradable, functionalized cellulose paper-based color-sensitive sensor (abbreviated as: cellulose paper-based color-sensitive sensor in this embodiment) for evaluating the quality of withered tea leaves mainly comprises the following steps:

[0083] Step 1: Sample selection:

[0084] The samples with time series are tea leaves with different withering times, and the tea leaves are grown in Jurong City, Jiangsu Province; the withering degree of the tea leaves is divided into grades 1-7 according to the withering time;

[0085] Level Description:

[0086] Level 1: The moisture content of the fresh leaves is about 70% after being picked. The leaves have high moisture content, are hard and brittle, and emit a grassy aroma.

[0087] Level 2: The fresh leaves were irradiated with far-infrared for 3 hours after being picked; the moisture content was reduced, the flexibility of the leaves was increased, and the richness of the aroma became stronger;

[0088] Level 3: This is a level 2 sample that has been naturally evaporated for 3 hours, and the total withering time is 6 hours; its moisture is further lost, the leaves are soft and not easy to break, the aroma becomes richer, and the grassy aroma becomes weaker;

[0089] Level 4: This is a level 3 sample that has been naturally evaporated for 3 hours, and the total withering time is 9 hours; its moisture is further lost, the leaves are soft and not easy to break, the aroma becomes richer, the grassy aroma becomes weaker, and the floral and fruity aroma is revealed;

[0090] Level 5: Level 4 samples are subjected to natural moisture evaporation for 3 hours, with a total withering time of 12 hours; the moisture is further lost, the leaves are soft and not easy to break, the grassy aroma becomes weaker, and the floral and fruity aroma is revealed;

[0091] Level 6: This is a level 5 sample that has been naturally evaporated for 3 hours, and the total withering time is 15 hours; its moisture is further lost, the leaves are soft and not easy to break, the grassy aroma becomes weaker, and the floral and fruity aroma is more obvious;

[0092] Level 7: This is a level 6 sample that has been naturally evaporated for 3 hours, with a total withering time of 18 hours, and the moisture content of the sample is about 60%; its moisture is further lost, the leaves are soft and not easy to break, the grassy aroma becomes weaker, and the floral and fruity aroma is revealed;

[0093] Step 2: First, use a camera to obtain an image of the cellulose paper-based color-sensitive sensor before it reacts;

[0094] Subsequently, 0.6 g of each withering degree sample was weighed and placed in a reaction container together with a cellulose paper-based color-sensitive sensor. The prepared cellulose paper-based color-sensitive sensor was fixed on the top of the reaction container. The cellulose paper-based color-sensitive sensor and the volatile odor substances of the tea samples with different withering degrees were allowed to fully react at 25°C for 20 minutes. Finally, a camera was used to obtain an image of the cellulose paper-based color-sensitive sensor after the reaction, and the obtained image was saved in a computer.

[0095] Step 3: Use a computer to locate the position of each color-sensitive unit of the cellulose paper-based color-sensitive sensor; decompose the image of the color-sensitive sensor obtained by the camera before and after the reaction into R channel, G channel and B channel grayscale images, and extract the hue (Hue, H), saturation (Saturation, S), brightness (Value, V), color brightness (L), red-green value (a) and yellow-blue value (b) of the image; subtract R, G, B, H, S, V, L, a, b of each sensitive unit before and after the reaction to obtain △R, △G, △B, △H, △S, △V, △L, △a, △b, and calculate according to Calculate the Euclidean distance. △R, △G, △B, △H, △S, △V, △L, △a, △b and ED are the characteristic variables of a color-sensitive unit, and 8 color-sensitive units have 80 characteristic variables; 7 matcha grades, each grade sample contains 25 samples, a total of 175 samples, and the 80 characteristic variables of these 175 samples are combined to obtain the characteristic matrix S; the LSTM model for matcha quality evaluation is constructed with the characteristic matrix S as input and the sample corresponding quality grade matrix T as output;

[0096] Figure 8 Figure a in the middle is an LSTM model for evaluating the quality of withered tea leaves based on sample information collected by a cellulose paper-based color-sensitive sensor, and the training accuracy of the evaluation model is 100%.

[0097] Step 4: Take 70 matcha samples of unknown grade, and obtain 24 feature variables of the 70 samples to be tested according to the methods described in steps 2 and 3 to form a feature variable matrix R (R is a 70*80 matrix); call the LSTM evaluation model constructed in step 3, and use the feature matrix R as input value. The output matrix Q is the quality grade information corresponding to the 70 samples to be tested, which realizes the rapid evaluation of tea quality during the withering process.

[0098] Figure 8 Figure b in the middle is the result of calling the LSTM evaluation model constructed in step three to predict 70 matcha samples to be tested, and its prediction accuracy is 90%. This result confirms that the cellulose paper-based color-sensitive sensor constructed in the present invention can realize the rapid evaluation of the quality of tea leaves during the withering process.

[0099] Embodiment 3:

[0100] A UV degradation method for a UV-degradable, functionalized cellulose paper-based color-sensitive sensor mainly comprises the following steps:

[0101] Step 1: Place the used UV-degradable, functionalized cellulose paper-based color-sensitive sensor under a UV lamp with dual emission wavelengths of 185 / 254 nm at a position of 2 cm to perform a degradation experiment;

[0102] Step 2: Use a camera to obtain images of the color-sensitive sensor before and after the degradation experiment, and use a computer to locate the position of each color-sensitive unit of the color-sensitive sensor, decompose the image of the color-sensitive unit into R channel, G channel and B channel grayscale images, and the color information of the color-sensitive unit before the degradation experiment is recorded as R a , G a and B a , the color information of the color-sensitive unit before the degradation experiment is recorded as R b , G b and B b ;

[0103] Then, the background information of the color-sensitive sensor is extracted, and the R channel, G channel, and B channel information of the background are extracted, which are recorded as R0, G0, and B0;

[0104] Step 2: Calculate the degradation rate of the color-sensitive sensor;

[0105] △R a =R0-R a , △G a =G0-G a ,

[0106] △R b =R0-R b , △G b =G0-G b ,

[0107]

[0108] Fig. 9 This is a graph of the UV degradation efficiency of the UV-degradable, functionalized cellulose paper-based color sensor produced in the example. It can be seen from the graph that the degradation rate of each color-sensitive unit in the color sensor increases with the extension of the irradiation time. When the irradiation time reaches 80 minutes, the color sensor can achieve a degradation effect of 60%-90%.

[0109] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above embodiments, a person skilled in the art should understand that the present invention can still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a UV-degradable, functionalized cellulose paper-based color-sensitive sensor, characterized in that: Here are the steps: Step 1, preparation of TiO2 cellulose paper base: Cut the filter paper according to the needs and soak it in anhydrous ethanol. After soaking, take out the filter paper and dry it to obtain dry filter paper; mix anhydrous ethanol, butyl titanate and glacial acetic acid to obtain a mixed solution, and soak the dry filter paper in the mixed solution, then place it on a shaker for shaking reaction, and take out the filter paper after the reaction to dry it; after drying, soak the filter paper in the mixed solution again, repeat the soaking, shaking reaction and drying steps several times, take out the filter paper and place it in deionized water for hydrolysis, and obtain TiO2 cellulose filter paper after hydrolysis; Step 2, preparation of TiO2 / OTS functionalized cellulose filter paper: The TiO2 cellulose filter paper obtained in step 1 is immersed in a mixed solution of octadecyltrichlorosilane and n-hexane, taken out after soaking, and then washed with n-hexane and anhydrous ethanol respectively, and dried after washing to obtain TiO2 / OTS cellulose filter paper; Then, a glass cover is placed on the TiO2 / OTS cellulose filter paper and exposed to ultraviolet light for a period of time. After exposure, the cellulose filter paper is cleaned with anhydrous ethanol to obtain a TiO2 / OTS functionalized cellulose filter paper having a circular hydrophilic color-sensitive spot area and a hydrophobic isolation area; the cover plate has the same area as the TiO2 / OTS cellulose filter paper, and is provided with a number of circular holes distributed at equal intervals; Step 3: Preparation of UV-degradable, functionalized cellulose paper-based colorimetric sensor: First, a color-sensitive material solution is prepared; then the color-sensitive material solution is dropped onto the circular hydrophilic spotting area of ​​the TiO2 / OTS functionalized cellulose filter paper prepared in step 2 to prepare a UV-degradable, functionalized cellulose paper-based color-sensitive sensor.

2. The method for preparing a UV-degradable, functionalized cellulose paper-based color-sensitive sensor according to claim 1, characterized in that: The filter paper in step 1 is a qualitative filter paper with a size of 30-40mm*30-40mm; the filter paper is soaked in anhydrous ethanol for 3-6h; the drying temperature of the filter paper is 30-50°C, and the drying time does not exceed 20min; The volume ratio of anhydrous ethanol, butyl titanate and glacial acetic acid is 10:3:1, the shaking reaction speed of the shaking table is 180-200r / min, and the shaking reaction time is 30-60min; the soaking, shaking reaction and drying steps are repeated 3-5 times; the hydrolysis temperature is 85-95°C, and the hydrolysis time is 2-5h.

3. The method for preparing a UV-degradable, functionalized cellulose paper-based color-sensitive sensor according to claim 1, characterized in that: In step 2, the volume ratio of octadecyltrichlorosilane to n-hexane is 1000:1, and the soaking time is 5-10 minutes; the number of cleaning times using n-hexane and anhydrous ethanol is 3-5 times; the drying temperature is 30-50° C., and the drying time does not exceed 20 minutes; The cover plate is a rectangular parallelepiped, and its length, width and thickness are 39mm, 39mm and 4mm respectively. The distance between the centers of adjacent circular holes is 9mm, and the diameter of the circular holes is 6mm. The ultraviolet lamp is an ultraviolet lamp with dual emission wavelengths of 185 and 254nm. The cover plate is below the ultraviolet lamp, and the distance between the ultraviolet lamp and the glass cover plate is 1-2cm, and the irradiation time is 40-60min. After the TiO2 / OTS cellulose filter paper is irradiated by the ultraviolet lamp, the area covered by the cover plate is not degraded by ultraviolet irradiation, forming a hydrophobic isolation area; after the TiO2 / OTS cellulose filter paper in the circular hole area is irradiated by ultraviolet light, OTS decomposes, and a circular hydrophilic spot area with a diameter of 6mm is formed on the TiO2 / OTS cellulose filter paper.

4. The method for preparing a UV-degradable, functionalized cellulose paper-based color-sensitive sensor according to claim 1, characterized in that: In step 3, the color-sensitive solutions are prepared in X quantities, where X is a positive integer, and the X color-sensitive solutions are composed of solution A and / or solution B; wherein solution A is a dichloromethane solution of metal porphyrin or fluoroborane pyrrole, and solution B is an ethanol solution of a pH indicator; The amount ratio of metal porphyrin or fluoroborane to dichloromethane in solution A is 2 mg:1 mL; the amount ratio of pH indicator to ethanol in solution B is 2 mg:1 mL; The amount of the color-sensitive dye solution fixed on the TiO2 / OTS functionalized cellulose filter paper is 1.5-2 μL.

5. The method for preparing a UV-degradable, functionalized cellulose paper-based color-sensitive sensor according to claim 1, characterized in that: The pH indicator in step three includes bromothymol blue, bromocresol green, methyl red, bromophenol blue, cresol red, and aniline violet; the metal porphyrin includes tetraphenylporphyrin manganese; and the fluoroborane includes 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoborane dipyrrolmethane.

6. Use of the UV-degradable, functionalized cellulose paper-based color-sensitive sensor prepared by the method according to any one of claims 1 to 5 for food quality monitoring, characterized in that: Here are the steps: (1) Establishment of food quality evaluation model: S1. Selecting a sample, where different quality levels of the sample correspond to different volatile odor substances, and different volatile odor substances will cause the color-sensitive sensor to produce different color changes; the sample includes a tea sample; S2. First, use a camera to obtain an image of the UV-degradable cellulose-based color-sensitive sensor before the reaction; then place the sample in a reaction container, and store the color-sensitive sensor and the sample in the same closed reaction container, so that the color-sensitive sensor and the volatile odor substances in the sample can fully react for a period of time; after the reaction, use a camera to obtain an image of the nano color-sensitive sensor after the reaction, and save the obtained image in a computer; use a computer to locate the position of the color-sensitive unit in the image before and after the reaction, and extract its color characteristics. The grayscale mean value of each color-sensitive unit before and after the reaction is subtracted, and the difference in grayscale mean value is the characteristic variable of the color-sensitive unit; The characteristic variables contained in all samples are combined to obtain a characteristic matrix, and a long-short time memory recursive neural network model for food quality evaluation is constructed with the characteristic matrix as input and the quality grade of the test samples as output, which is the food quality evaluation model; (2) Rapid evaluation of food quality: The sample to be tested is reacted according to the method described in (1) to obtain characteristic variables; the characteristic variables of the sample to be tested are brought into the LSTM model constructed in (1) to obtain the quality grade information of the sample to be tested, thereby realizing rapid evaluation of food quality.

7. The use according to claim 6, characterized in that The steps are as follows: the amount of sample used in S2 of step (1) is 0.5-1.5 g, and the reaction time is 10-30 min; the color-sensitive sensor is fixed on the top of the reaction container.

8. The use according to claim 6, characterized in that The steps are as follows: The steps of extracting the characteristic variables in S2 of step (1) are as follows: using a computer to locate the position of each color-sensitive unit of the color-sensitive sensor; decomposing the image of the color-sensitive sensor before and after the camera acquires the reaction into R channel, G channel and B channel grayscale images, and extracting the hue (denoted as H), saturation (denoted as S), brightness (denoted as V), color brightness (denoted as L), red-green value (denoted as a) and yellow-blue value (denoted as b) of the image; The R, G, B, H, S, V, L, a, and b of each sensitive unit before and after the reaction are subtracted, and the corresponding differences are recorded as △R, △G, △B, △H, △S, △V, △L, △a, and △b respectively; and according to Calculate the Euclidean distance; △R, △G, △B, △H, △S, △V, △L, △a, △b and ED are the characteristic variables of a color-sensitive unit, and X color-sensitive units obtain Y characteristic variables, where Y = 10X; The number of samples used to construct the food quality evaluation model is selected to be N, including n processing levels, m samples in each level, that is, N=n*m; n is a positive integer not less than 2, and m and N are both positive integers.

9. The use according to claim 6, characterized in that: The steps are as follows: The steps for establishing the food quality evaluation model in S2 of step (1) are as follows: the feature matrix is ​​denoted as S, S is N*Y, where N is the number of samples, and Y is the feature variable contained in X color-sensitive units; The input feature variable matrix S generates a hidden state matrix H through the calculation of the LSTM unit; then the hidden state matrix H is selectively mapped to the output matrix H' through the fully connected layer, where H' is f(W h *H+b h ), where f is the activation function, W h is the weight matrix, b h is the bias variable.

10. The use according to claim 6, characterized in that The steps are as follows: The steps for rapid evaluation of food quality in step (2) are as follows: according to the method described in step (1), Y characteristic variables of M samples to be tested are obtained to form a characteristic variable matrix R, where R is an M*Y matrix; The LSTM evaluation model constructed in step (1) is called, and the feature matrix R is used as the input value. The output value Q corresponds to the processing degree information of the M samples to be tested, thereby realizing a rapid evaluation of food quality.

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