Preparation method and use of ultraviolet-degradable, functionalized cellulose paper-based colorimetric sensor

Abstract

The application belongs to the technical field of color-sensitive sensing 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-based color-sensitive sensor; the steps are as follows: firstly, a TiO2 cellulose paper base and a TiO2 / OTS functionalized cellulose filter paper are prepared; then a color-sensitive sensor is obtained by combining a color-sensitive material; a food quality evaluation model is established based on the color-sensitive sensor, and rapid evaluation of food quality is realized. The paper-based color-sensitive sensor prepared by the application has a TiO2 surface load, and the photocatalysis of the TiO2 layer can effectively degrade color-sensitive dyes; and the paper base has a hydrophilic sample loading area and a hydrophobic isolation area; the isolation area can effectively isolate the mutual influence of the color-sensitive units, and improve the moisture resistance and stability of the sensor. The color-sensitive sensor prepared by the application has strong moisture resistance, good stability and good environmental compatibility, can be applied to rapid detection of food quality, and has good application prospect and use value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of colorimetric sensing detection and non-destructive detection of food and agricultural products, and particularly relates to a preparation method and application of an ultraviolet-degradable and functionalized cellulose paper-based colorimetric sensor. BACKGROUND

[0002] Volatile organic compounds in food refer to a class of chemical substances that can volatilize into the air in food, which have an important influence on food quality. Monitoring volatile organic compounds in food can achieve the evaluation of food quality and timely warning of possible quality problems in food processing or storage. By monitoring and controlling the volatile components of food in a timely manner, the flavor characteristics and product quality of food can be ensured, and the satisfaction of consumers and the market competitiveness of products can be improved. Therefore, monitoring the volatile components of food is of great significance.

[0003] Gas chromatography or gas chromatography-mass spectrometry technology 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. Colorimetric sensing detection technology for volatile components is based on the principle of mammalian olfactory perception. 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 colorimetric sensors. Paper-based materials are commonly used flexible materials for preparing colorimetric sensors, which have the advantages of convenient use, good biocompatibility and low cost, and are favored by researchers. However, the inherent hydrophilicity of filter paper will cause the colorimetric response signal to drift, which seriously hinders its practical application. In addition, the strong capillary force between colorimetric units will cause uneven diffusion of the solution, which will affect the sensing units and cause poor stability of the colorimetric sensor. Metal porphyrin, fluoroboropyrrole and pH indicator are used as colorimetric dyes for preparing sensors, which will pollute the environment. With the development of society, people's environmental awareness is gradually improving. Developing degradable substrates for constructing colorimetric sensors can avoid secondary pollution and is of great significance to environmental protection. SUMMARY

[0004] In view of the problems of poor stability and low moisture resistance of the color-sensitive sensor, the application provides a functionalized fiber filter paper paper-based material, which has a hydrophilic color-sensitive point sample area and a hydrophobic isolation area. The large-area hydrophobic area can effectively isolate the moisture in the environment absorbed by the filter paper, 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 application provides a paper-based material with TiO2 photocatalytic properties. When the color-sensitive sensor is prepared using the paper-based material, the dye on the color-sensitive sensor only needs to be irradiated with ultraviolet light to achieve the purpose of degradation, 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, poor moisture resistance, complex detection process and dye pollution of the environment in the prior art.

[0005] In order to achieve the above-mentioned purpose, the specific steps of the application are as follows:

[0006] A preparation method of an ultraviolet-degradable, functionalized cellulose paper-based color-sensitive sensor, comprising the following steps:

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

[0008] According to the requirements, the filter paper is cut and soaked in anhydrous ethanol (to clean and activate the hydroxyl groups on the surface of the cellulose structure), after soaking, the filter paper is taken out and dried to obtain dry filter paper; anhydrous ethanol, butyl titanate and glacial acetic acid are mixed to obtain a mixed solution, and the dry filter paper is soaked in the mixed solution, then placed on a shaking table for shaking reaction, after reaction, the filter paper is taken out and dried; after drying, the filter paper is soaked in the mixed solution again, and the soaking, shaking reaction and drying steps are repeated for several times, then the filter paper is taken out and hydrolyzed in deionized water, and TiO2 cellulose filter paper is obtained after hydrolysis;

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

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

[0011] Then a glass cover plate is covered on the TiO2 / OTS cellulose filter paper, and is irradiated under a ultraviolet lamp for a period of time, and then the cellulose filter paper is cleaned with anhydrous ethanol to obtain TiO2 / OTS functionalized cellulose filter paper with circular hydrophilic color-sensitive point sample area and hydrophobic isolation area; the cover plate is consistent with the area of the TiO2 / OTS cellulose filter paper, and a plurality of circular holes are arranged on the cover plate at equal intervals;

[0012] Step three, preparation of the UV-degradable, functionalized cellulose paper-based colorimetric sensor:

[0013] First, prepare the colorimetric material solution; then, drop the colorimetric material solution on the circular hydrophilic spotting area of the TiO2 / OTS functionalized cellulose filter paper prepared in step two to prepare a UV-degradable, functionalized cellulose paper-based colorimetric sensor.

[0014] Preferably, the filter paper in step one is qualitative filter paper, and the size is 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℃, and the drying time is not more than 20min.

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

[0016] Preferably, in step two, the volume ratio of octadecyltrichlorosilane to n-hexane is 1000:1, and the soaking time is 5-10min; the number of washing times using n-hexane and anhydrous ethanol is 3-5 times; the drying temperature is 30-50℃, and the drying time is not more than 20min.

[0017] Preferably, in step two, the cover plate is a cuboid with a length of 39mm, a width of 39mm and a thickness of 4mm, the center distance between adjacent circular holes is 9mm, and the diameter of the circular holes is 6mm.

[0018] The UV lamp is a UV lamp with dual emission wavelengths of 185 and 254nm; the cover plate is below the UV lamp, and the distance between the UV 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 UV lamp, the area covered by the cover plate is not degraded by UV irradiation, forming a hydrophobic isolation zone; the TiO2 / OTS cellulose filter paper in the circular hole area is degraded by the UV irradiation, and the OTS is decomposed, forming a hydrophilic spotting area with a diameter of 6mm on the TiO2 / OTS cellulose filter paper.

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

[0020] The metalloporphyrin includes tetraphenylporphyrin manganese; the fluoroboropyrrole includes 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoborondipyrrromethane; and the pH indicator includes bromothymol blue, bromocresol green, methyl red, bromophenol blue, cresol red, chlorophenol red, aniline violet;

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

[0022] Based on the application of the prepared ultraviolet-degradable and functionalized cellulose paper-based color-sensitive sensor in food quality monitoring, the steps are as follows:

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

[0024] S1, selecting samples, different quality grades of samples correspond to different volatile odor substances, and different volatile odor substances will cause different color changes of the color-sensitive sensor; the samples include tea samples;

[0025] S2, first, use a camera to obtain an image of the ultraviolet-degradable cellulose-based color-sensitive sensor before reaction; then place the sample in a reaction container, and store the color-sensitive sensor and the sample in the same sealed reaction container, so that the volatile odor substances of the color-sensitive sensor and the sample 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 the computer to locate the positions of the color-sensitive units before and after the reaction, extract the color features, and calculate the difference between the gray value averages of each color-sensitive unit before and after the reaction, so as to obtain the difference value of the gray value average, which is the characteristic variable of the color-sensitive unit;

[0026] Combine the characteristic variables contained in all samples to obtain a characteristic matrix, use the characteristic matrix as input, and use the quality grade of the detected sample as output to construct a long short-term memory recursive neural network (LSTM) model for food quality evaluation, which is a 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 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 the sample 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 at the top end of the reaction container.

[0030] Preferably, the extraction of the characteristic variables in S2 of step (1) is as follows: the positions of each color-sensitive unit of the color-sensitive sensor are located by using a computer; the images of the color-sensitive sensor before and after the reaction are decomposed into R channel, G channel and B channel gray scale images, and the hue (H), saturation (S), brightness (V), color brightness (L), red-green value (a) and yellow-blue value (b) of the images are extracted.

[0031] The differences between R, G, B, H, S, V, L, a and b of each sensitive unit before and after the reaction are calculated to obtain the corresponding difference values, which are denoted as ΔR, ΔG, ΔB, ΔH, ΔS, ΔV, ΔL, Δa and Δb in sequence; and the Euclidean distance is calculated according to The characteristic variables of one color-sensitive unit are ΔR, ΔG, ΔB, ΔH, ΔS, ΔV, ΔL, Δa and Δb and ED, and X color-sensitive units obtain Y characteristic variables, wherein Y=10X.

[0032] Preferably, the number of samples used to construct the food quality evaluation model in S2 of step (1) is selected as N, wherein N contains n degrees of treatment, and each degree contains m samples, i.e. N=n*m; n is a positive integer not less than 2, and m and N are positive integers.

[0033] Preferably, the establishment of the food quality evaluation model in S2 of step (1) is as follows: the characteristic matrix is denoted as S, S is N*Y, wherein N is the number of samples, and Y is the characteristic variables contained by X color-sensitive units; the input characteristic variable matrix S is calculated through 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 full connection layer, H' is f(W h *H+b h ), wherein f is an activation function, W h is a weight matrix, and b h is a bias variable (the model parameters, including the weight matrix inside the LSTM unit and the weight matrix W h and the bias variable b h of the full connection layer, are optimized by minimizing the error between the predicted output matrix H' and the actual label).

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

[0035] Preferably, the rapid evaluation of food quality in step (2) is as follows: Y characteristic variables of M to-be-tested samples are obtained according to the method in step (1) to form a characteristic variable matrix R, R is an M*Y matrix; the LSTM evaluation model constructed in step (1) is called, the characteristic matrix R is taken as an input value, and output values Q correspond to processing degree information of the M to-be-tested samples respectively, so that the rapid evaluation of food quality is realized.

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

[0037] (1) The present application discloses a preparation method of an ultraviolet-degradable cellulose-based color-sensitive sensor and a rapid evaluation method of food quality, which mainly focuses on breaking through technical problems such as high detection cost, poor sensor stability, complex detection process and dye pollution of the environment, and realizes rapid evaluation of food quality by obtaining food volatile component information.

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

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

[0040] (4) The long short-term memory recurrent neural network (LSTM) model for rapid evaluation of food quality has time sequence, uses signal values collected by the color-sensitive sensor as input, and uses the processing degree of food as output to establish an evaluation model of food quality, has good universality, improves the quality evaluation efficiency, and has important significance for evaluation of food quality in the processing process. BRIEF DESCRIPTION OF DRAWINGS

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

[0042] Figure 2 (a) and (b) are scanning electron microscope images and EDS energy spectrum images of TiO2 cellulose filter paper;

[0043] Figure 3 (a) and (b) are scanning electron microscope images and EDS energy spectrum images of TiO2 / OTS cellulose filter paper;

[0044] Figure 4 (a) and (b) are schematic diagrams of a glass cover plate and UV irradiation, and the formation of hydrophilic and hydrophobic spotting areas after UV irradiation, respectively;

[0045] Figure 5 (a) and (b) are schematic diagrams of a glass cover plate and UV irradiation, and the formation of hydrophilic and hydrophobic spotting areas after UV irradiation, respectively;

[0046] Figure 6 (a) and (b) are schematic diagrams of a glass cover plate and UV irradiation, and the formation of hydrophilic and hydrophobic spotting areas after UV irradiation, respectively;

[0047] Figure 7 (a) and (b) are schematic diagrams of a glass cover plate and UV irradiation, and the formation of hydrophilic and hydrophobic spotting areas after UV irradiation, respectively;

[0048] Figure 8 (a) and (b) are schematic diagrams of a glass cover plate and UV irradiation, and the formation of hydrophilic and hydrophobic spotting areas after UV irradiation, respectively;

[0049] Figure 9 (a) and (b) are schematic diagrams of a glass cover plate and UV irradiation, and the formation of hydrophilic and hydrophobic spotting areas after UV irradiation, respectively; DETAILED DESCRIPTION

[0050] Various illustrative embodiments of the present application are described in detail below. This detailed description is not intended to restrict the application unless so indicated, but to provide a description of certain aspects, features, and embodiments of the present application.

[0051] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains.

[0052] Although preferred methods and materials have been described herein, any method and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials which are described in them. In case of conflict, the content of the present specification will control.

[0053] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application.

[0054] Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only.

[0055] Example 1:

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

[0057] Step one: first, cut the qualitative filter paper into the size of 40*40mm, and soak it in anhydrous ethanol for 3h 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℃ for 15min to obtain dry filter paper;

[0058] Then, prepare a mixed solution of anhydrous ethanol, butyl titanate and glacial acetic acid in a volume ratio of 10:3:1, then soak the dry filter paper in the mixed solution, shake it in a shaker at a speed of 190r / min for 30min, then take out the filter paper and dry it in an oven at 50℃ for 15min, then soak it in the mixed solution again, and repeat the soaking and drying steps for 3 times, to obtain cellulose filter paper fully adsorbed with butyl titanate;

[0059] Finally, place the cellulose filter paper fully adsorbed with butyl titanate in ultrapure water at 95℃ for 5h, and then obtain TiO2 cellulose paper base after sufficient hydrolysis.

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

[0061] Step two: first mix octadecyltrichlorosilane with n-hexane to obtain a mixed solution, wherein the volume ratio of octadecyltrichlorosilane to n-hexane is 1000:1;

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

[0063] Finally, a glass cover plate was placed over the TiO2 / OTS cellulose filter paper and irradiated for 30 minutes at a position 2 cm away under a 185 / 254 nm dual-emission wavelength UV lamp. The cellulose filter paper was then washed with anhydrous ethanol to obtain TiO2 / OTS functionalized cellulose filter paper with circular hydrophilic color-sensitive spotting areas and hydrophobic isolation areas. The cover plate was a cuboid with a length, width, and thickness of 39 mm, 39 mm, and 4 mm, respectively. The center-to-center distance between adjacent circular holes was 9 mm, and the diameter of each circular hole was 6 mm. All circular holes were located inside the cover plate and did not intersect with the side lengths. Furthermore, the distance from the center of any circular hole near the perimeter of the cover plate to the nearest side of the cover plate was 6 mm.

[0064] Figure 2 This is a time optimization diagram for OTS surface modification of TiO2 cellulose filter paper. As can be seen from the diagram, 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 min, the surface tension and contact angle of the filter paper basically stabilize, that is, the optimal time for OTS surface modification of TiO2 cellulose filter paper is 5 min.

[0065] Figure 3 These are scanning electron microscope (SEM) images and EDS spectra of TiO2 / OTS cellulose filter paper; through... Figure 3 Figure a shows that many chemical substances have grown on the surface and in the pores of the filter paper fibers. Figure 3 EDS spectra of b and c show that the surface and pores of the filter paper fibers are filled with TiO2 and OTS. This result indicates that TiO2 and OTS have been successfully loaded onto the surface of the fiber filter paper, and the hydrophobic modification of the filter paper has been successful.

[0066] Figure 4 Image a shows a schematic diagram of the glass cover and UV irradiation; image b shows a schematic diagram of the formation of hydrophilic and hydrophobic sampling areas after UV irradiation. Figure 4 Figure a shows the arrangement and diameter of the circular openings in the glass cover, as well as the distance between the UV lamp and the glass cover during UV irradiation; from Figure 4 As shown in Figure b, the TiO2 / OTS cellulose filter paper covering the cover plate will form a TiO2 / OTS cellulose functionalized filter paper with a hydrophilic color-sensitive sampling area and a hydrophobic isolation area after being irradiated by a UV lamp.

[0067] Figure 5 The figure shows the optimal time for functional modification of TiO2 / OTS functionalized cellulose filter paper. As can be seen from the figure, with the extension of UV treatment time, the surface tension of the filter paper increases and the contact angle decreases. After 30 min of UV irradiation, the surface tension and contact angle of the filter paper basically stabilize, that is, the optimal time for functional modification of TiO2 / OTS functionalized cellulose filter paper is 30 min.

[0068] Step three: first, 8 color-sensitive solutions were prepared, consisting of 1 dichloromethane solution of fluoropyrrole, 1 dichloromethane solution of metal porphyrin and 6 ethanol solutions of pH indicator;

[0069] Among them, the 8 color-sensitive solutions are respectively 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] Among them, the color-sensitive solution A is a dichloromethane solution of 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoborondipyrrromethane, and the amount ratio of 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoborondipyrrromethane to dichloromethane is 20mg:10mL;

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

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

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

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

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

[0076] The color-sensitive solution G is an ethanol solution of cresyl red, and the amount ratio of cresyl red to ethanol is 20mg:10mL;

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

[0078] Finally, 1.5μL of the color-sensitive solution was fixed on the hydrophilic color-sensitive sampling area of the TiO2 / OTS functionalized cellulose filter paper using micro-capillary pipetting, to obtain a color-sensitive sensor based on TiO2 / OTS functionalized cellulose filter paper, i.e. an ultraviolet-degradable, functionalized cellulose paper-based color-sensitive sensor.

[0079] Figure 6Figure 1 is a contrast effect diagram of TiO2 / OTS functionalized cellulose filter paper and ordinary filter paper for color-sensitive sensor; from the figure, it can be seen that the color-sensitive sensor prepared by TiO2 / OTS functionalized cellulose filter paper has a lower coefficient of variation, indicating that the color-sensitive sensor prepared by TiO2 / OTS functionalized cellulose filter paper has better stability.

[0080] Figure 7 Figure 2 is a contrast effect diagram of the moisture resistance of color-sensitive sensors prepared by ordinary filter paper (a) and TiO2 / OTS functionalized cellulose filter paper; from the figure, it can be seen 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] Example 2:

[0082] The use of the ultraviolet-degradable and functionalized cellulose paper-based color-sensitive sensor (hereinafter referred to as cellulose paper-based color-sensitive sensor) for withering tea quality evaluation mainly includes the following steps:

[0083] Step 1: Selection of samples:

[0084] Samples with time sequence are selected as tea leaves with different withering times, which 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] Grade explanation:

[0086] Grade 1: It is a sample of fresh leaves picked after 70% water content; the leaf water content is high, the leaf is hard and easy to break, and emits a grassy aroma;

[0087] Grade 2: It is a sample of fresh leaves picked after 3h of far-infrared irradiation; the water content is reduced, the leaf flexibility is increased, and the aroma abundance is increased;

[0088] Grade 3: It is a sample of grade 2 sample after 3h of natural water evaporation, with a total withering time of 6h; the water content is further reduced, the leaf is soft and not easy to break, the aroma abundance is increased, and the grassy aroma is weakened;

[0089] Grade 4: It is a sample of grade 3 sample after 3h of natural water evaporation, with a total withering time of 9h; the water content is further reduced, the leaf is soft and not easy to break, the aroma abundance is increased, the grassy aroma is weakened, and the flower and fruit aroma is revealed;

[0090] Grade 5: It is a sample of grade 4 sample after 3h of natural water evaporation, with a total withering time of 12h; the water content is further reduced, the leaf is soft and not easy to break, the grassy aroma is weakened, and the flower and fruit aroma is revealed;

[0091] Grade 6: it is the sample of grade 5 sample after natural moisture evaporation for 3h, the total length of wilting is 15h; its moisture is further lost, the leaf is soft and not easy to break, the green grass smell is weak, and the flower and fruit smell is more obvious;

[0092] Grade 7: it is the sample of grade 6 sample after natural moisture evaporation for 3h, the total length of wilting is 18h, and the moisture content of the sample is about 60%; its moisture is further lost, the leaf is soft and not easy to break, the green grass smell is weak, and the flower and fruit smell is obvious;

[0093] Step two: first, the image of the cellulose paper-based color sensor before reaction is obtained by using the camera;

[0094] Then, 0.6g of each wilting degree sample is weighed and placed in the reaction container with the cellulose paper-based color sensor, the prepared cellulose paper-based color sensor is fixed at the top of the reaction container, and the cellulose paper-based color sensor and the volatile odor substances of the tea leaf sample with different wilting degrees are fully reacted at 25℃ for 20min; finally, the image of the cellulose paper-based color sensor after reaction is obtained by using the camera, and the obtained image is saved in the computer.

[0095] Step three: the position of each color-sensitive unit of the cellulose paper-based color sensor is located by using the computer; the images of the color sensor before and after reaction are decomposed into R channel, G channel and B channel gray scale images, and the hue (H), saturation (Saturation, S), brightness (Value, V), color brightness (L), red-green value (a) and yellow-blue value (b) of the image are extracted; the differences of R, G, B, H, S, V, L, a, b of each sensitive unit before and after reaction are obtained, that is, △R, △G, △B, △H, △S, △V, △L, △a, △b, and the Euclidean distance is calculated according to The △R, △G, △B, △H, △S, △V, △L, △a, △b and ED are the characteristic variables of a color-sensitive unit, and 80 characteristic variables are obtained from 8 color-sensitive units; 7 grades of matcha, each grade sample contains 25 samples, a total of 175 samples, and 80 characteristic variables of the 175 samples are combined to obtain a characteristic matrix S; the characteristic matrix S is taken as the input, and the sample corresponding quality grade matrix T is taken as the output to construct the LSTM model for evaluating the quality of matcha;

[0096] Figure 8 Fig. 2a is an evaluation LSTM model for wilting tea quality based on the sample information collected by the cellulose paper-based color sensor, and the training accuracy of the evaluation model is 100%.

[0097] Step four: 70 unknown grade of matcha samples are taken, 24 characteristic variables of the 70 to-be-tested samples are obtained according to the method described in steps two and three to form a characteristic variable matrix R (R is a 70*80 matrix); the LSTM evaluation model constructed in step three is called, the characteristic matrix R is taken as an input value, and the output matrix Q is the quality grade information corresponding to the 70 to-be-tested samples, so that the quality of the withering process tea leaves is rapidly evaluated.

[0098] Figure 8 Fig. b is the prediction result of the 70 to-be-tested matcha samples by calling the LSTM evaluation model constructed in step three, and the prediction accuracy is 90%, which proves that the cellulose paper-based colorimetric sensor constructed in the application can realize the rapid evaluation of the quality of the withering process tea leaves.

[0099] Example 3:

[0100] The ultraviolet degradation of the ultraviolet-degradable and functionalized cellulose paper-based colorimetric sensor mainly comprises the following steps:

[0101] Step one: the used ultraviolet-degradable and functionalized cellulose paper-based colorimetric sensor is placed at a position 2 cm away from a 185 / 254 nm dual-emission wavelength ultraviolet lamp for irradiation, and a degradation experiment is performed;

[0102] Step two: a camera is used to obtain the images of the colorimetric sensor before and after the degradation experiment, and a computer is used to locate the position of each colorimetric unit of the colorimetric sensor, so as to decompose the image of the colorimetric unit into R channel, G channel and B channel grayscale images; the color information of the colorimetric unit before the degradation experiment is recorded as R a , G a and B a , and the color information of the colorimetric unit before the degradation experiment is recorded as R b , G b and B b .

[0103] Then, the background information of the colorimetric sensor is extracted, and the R channel, G channel and B channel information of the background are extracted and recorded as R0, G0 and B0.

[0104] Step two: the degradation rate of the colorimetric sensor is calculated;

[0105] △R a = R0-R a , △G a = G0-G a ,

[0106] △R b = R0-R b , △G b = G0-G b ,

[0107]

[0108] Figure 9 Figure of UV degradation efficiency of the UV-degradable, functionalized cellulose paper-based colorimetric sensor made in the examples; from the figure, it can be seen that the degradation rate of each colorimetric unit in the colorimetric sensor increases with the extension of the irradiation time; when the irradiation time reaches 80 min, the colorimetric sensor can achieve a degradation effect of 60%-90%.

[0109] Description: the above examples are only used to illustrate the present application and not to limit the technical solutions described in the present application; therefore, although the present application has been described in detail with reference to the above-mentioned various embodiments, those skilled in the art should understand that the present application can still be modified or replaced equivalently; and all technical solutions and improvements which do not deviate from the spirit and scope of the present application should be covered in the scope of the claims of the present application.

Claims

1. Use of an ultraviolet-degradable, functionalized cellulose paper-based colorimetric sensor for food quality monitoring, characterized in that, The steps are as follows: Step one, preparation of TiO2 cellulose paper base: According to the needs, the filter paper is cut and soaked in anhydrous ethanol, after soaking, the filter paper is taken out and dried to obtain dry filter paper; a mixed solution is obtained by mixing anhydrous ethanol, butyl titanate and glacial acetic acid, the volume ratio of the anhydrous ethanol, butyl titanate and glacial acetic acid is 10:3:1; and the dry filter paper is soaked in the mixed solution, then placed on a shaker for shaking reaction, after the reaction, the filter paper is taken out and dried; after drying, the filter paper is soaked in the mixed solution again, and the soaking, shaking reaction and drying steps are repeated several times, then the filter paper is taken out and hydrolyzed in deionized water, and a TiO2 cellulose filter paper is obtained after hydrolysis; Step two, preparation of TiO2 / OTS functionalized cellulose filter paper: The TiO2 cellulose filter paper obtained in step one 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 a TiO2 / OTS cellulose filter paper; Then a glass cover plate is covered on the TiO2 / OTS cellulose filter paper and irradiated under a UV lamp for 40 min, and the cellulose filter paper is washed with anhydrous ethanol after irradiation to obtain a TiO2 / OTS functionalized cellulose filter paper with circular hydrophilic color-sensitive spot sample area and hydrophobic isolation area; the cover plate is consistent with the area of the TiO2 / OTS cellulose filter paper, and a plurality of circular holes are evenly distributed on the cover plate; Step three, preparation of ultraviolet-degradable and functionalized cellulose paper-based colorimetric sensor: First, a colorimetric material solution is prepared; the colorimetric material solution is composed of A solution and B solution; wherein the A solution includes a dichloromethane solution of metal porphyrin and a dichloromethane solution of fluoroboropyrrole, and the B solution is an ethanol solution of a pH indicator; the metal porphyrin includes tetraphenylporphyrin manganese; the fluoroboropyrrole includes 8-(4-methoxyphenyl)-4,4-difluoro-2,6-dibromoborondipyrrylmethane; and the pH indicator includes bromothymol blue, bromocresol green, methyl red, bromophenol blue, cresol red and aniline violet; the amount ratio of metal porphyrin or fluoroboropyrrole to dichloromethane in the A solution is 2mg:1mL; and the amount ratio of the pH indicator to ethanol in the B solution is 2mg:1mL; Then the colorimetric material solution is added dropwise on the circular hydrophilic spot sample area of the TiO2 / OTS functionalized cellulose filter paper prepared in step two to prepare an ultraviolet-degradable and functionalized cellulose paper-based colorimetric sensor; Step four, use of the ultraviolet-degradable and functionalized cellulose paper-based colorimetric sensor for food quality monitoring: (1) Establishment of food quality evaluation model: Select samples, different volatile odorants corresponding to different sample processing degrees, and different volatile odorants will cause different color changes of the colorimetric sensor; the samples include tea samples; Firstly, the image of the UV-degradable cellulose-based colorimetric sensor before reaction is obtained by using a camera; then the sample is placed in a reaction container, and the colorimetric sensor and the sample are stored in the same sealed reaction container, so that the volatile odor substances of the colorimetric sensor and the sample can fully react for a period of time; after the reaction, the image of the colorimetric sensor after the reaction is obtained by using the camera, and the obtained image is saved in the computer; the positions of the colorimetric units in the images before and after the reaction are located by using the computer, the color features are extracted, and the gray mean values of each colorimetric unit before and after the reaction are subtracted to obtain the difference value of the gray mean value, which is the characteristic variable of the colorimetric unit; The characteristic variables contained in all samples are combined to obtain a characteristic matrix, and the long-short time memory recurrent neural network model for food quality evaluation is constructed by taking the characteristic matrix as the input and the quality grade of the detection sample as the output, that 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 the characteristic variable; the characteristic variable of the sample to be tested is brought into the LSTM model constructed in (1) to obtain the quality grade information of the sample to be tested, thereby realizing the rapid evaluation of food quality.

2. Use of the ultraviolet degradable, functionalized cellulose paper-based colorimetric sensor for food quality monitoring according to claim 1, characterized in that, The filter paper in step one is qualitative filter paper, and the size is 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℃, and the drying time is not more than 20min; The shaking speed of the shaking table is 180-200r / min, and the shaking time is 30-60min; the number of repeated soaking, shaking and drying steps is 3-5 times; the hydrolysis temperature is 85-95℃, and the hydrolysis time is 2-5h.

3. Use of the UV-degradable, functionalized cellulose paper-based colorimetric sensor according to claim 1 for food quality monitoring, characterized in that, The volume ratio of octadecyltrichlorosilane to n-hexane in step two is 1000:1, and the soaking time is 5min; the n-hexane and anhydrous ethanol are washed for 3-5 times; the drying temperature is 30-50℃, and the drying time is not more than 20min; The cover plate is a cuboid, 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 hole is 6mm; the ultraviolet lamp is a 185 and 254nm dual-emission wavelength ultraviolet lamp; the cover plate is below the ultraviolet lamp, and the distance between the ultraviolet lamp and the glass cover plate is 1-2cm; after the TiO2 / OTS cellulose filter paper is irradiated by the ultraviolet lamp, the cover plate covers the area that is not degraded by ultraviolet radiation, forming a hydrophobic isolation zone; after the TiO2 / OTS cellulose filter paper in the circular hole area is irradiated by the ultraviolet lamp, the OTS is decomposed, forming a hydrophilic spotting area with a diameter of 6mm on the TiO2 / OTS cellulose filter paper.

4. Use of the ultraviolet degradable, functionalized cellulose paper-based colorimetric sensor according to claim 1 for food quality monitoring, characterized in that, The amount of colorimetric material solution fixed on the TiO2 / OTS functionalized cellulose filter paper in step three is 1.5-2μL.

5. Use of the ultraviolet degradable, functionalized cellulose paper-based colorimetric sensor according to claim 1 for food quality monitoring, characterized in that, The amount of sample in step four (1) is 0.5-1.5g, the reaction time is 10-30min, and the colorimetric sensor is fixed at the top of the reaction container. The color features described in step four (1) include hue (denoted as H), saturation (denoted as S), brightness (denoted as V), brightness of color (denoted as L), red-green value (denoted as a), and yellow-blue value (denoted as b); according to Calculate the Euclidean distance; the 10 color feature variables of a single color-sensitive unit are ΔR, ΔG, ΔB, ΔH, ΔS, ΔV, ΔL, Δa, Δb, and ED, and X color-sensitive units obtain Y feature variables, where Y = 10X; The sample number for constructing the food quality evaluation model is N, wherein n treatment degrees are included, and m samples are included in each degree, that is, N=n*m; n is a positive integer not less than 2, and m and N are positive integers; The feature matrix is denoted as S, S is N*Y, wherein N is the sample number, and Y is the feature variable included in the X color-sensitive units; Input The 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 into an output matrix H' through a full connection layer, H' = f(W h *H+b h ), wherein f is an activation function, W h is a weight matrix, and b h is a bias variable; In step four (2), the rapid evaluation of food quality is as follows: Y feature variables of M to-be-tested samples are obtained according to the method in step (1), A feature variable matrix R is formed, and R is an M*Y matrix; An LSTM evaluation model constructed in step (1) is called, the feature matrix R is taken as an input value, and output values Q correspond to the treatment degree information of the M to-be-tested samples respectively, so that the rapid evaluation of food quality is realized.

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