CN114031977B

CN114031977B - Fluorescent ink and preparation method and application thereof

Info

Publication number: CN114031977B
Application number: CN202111432835.0A
Authority: CN
Inventors: 田颜清; 蔡少勇; 宋光杰; 张国藩
Original assignee: Southwest University of Science and Technology
Current assignee: Southwest University of Science and Technology
Priority date: 2021-11-29
Filing date: 2021-11-29
Publication date: 2023-01-20
Anticipated expiration: 2041-11-29
Also published as: CN114031977A

Abstract

The invention relates to the technical field of printing ink, in particular to fluorescent printing ink and a preparation method and application thereof. The fluorescent ink comprises a fluorescent pigment, a binder and a solvent; the fluorescent pigment comprises curcumin and/or curcumin derivatives. The fluorescent ink adopts curcumin and/or curcumin derivatives as fluorescent pigments to prepare the fluorescent ink with different colors, can effectively detect volatile amine, and has the characteristics of high speed, high sensitivity and high selectivity. The fluorescent ink is coated on a printing stock to prepare the fluorescent indicating label with freshness detection and anti-counterfeiting functions, so that characteristic gas generated in the food spoilage process can be detected, and the food freshness information can be accurately obtained.

Description

Fluorescent ink and preparation method and application thereof

Technical Field

The invention relates to the technical field of printing ink, in particular to fluorescent printing ink and a preparation method and application thereof.

Background

During food production, transport and storage, enzymatic breakdown of proteins produces volatile amines, including ammonia (NH), that are closely related to food freshness ₃ ) Putrescine, cadaverine, tyramine, dimethylamine, and the like. Wherein by NH ₃ The sensor can effectively monitor NH in the package ₃ The concentration promotes the public consumers to efficiently and accurately obtain the freshness of the food. According to different materials and NH ₃ The difference in the principle of feedback information after molecular contact can be roughly divided into fluorescence sensors and conductance sensors. Wherein NH ₃ The fluorescence sensor mainly feeds back NH in the environment by means of color, chromatogram and the like ₃ And (4) concentration. Thus, it is possible to provideThe appropriate ammonia-sensitive material is searched to prepare the fluorescent ink, so that the NH in the package can be accurately, visually and timely detected ₃ A concentration of food freshness indicator label would be an effective way to replace shelf-life labels. In addition, due to low production cost and high anti-counterfeiting performance, the fluorescent ink is often applied to anti-counterfeiting printing of famous brand commodities such as currency, certificates, securities, high-grade cigarettes, wine, medicines, cosmetics and the like. In recent years, a preparation method for obtaining a highly sensitive gas indicator label by disposing a fluorescent ink based on the gas response characteristics of a fluorescent material has been favored.

Today, food freshness indicator labels prepared based on fluorescent inks primarily communicate the concentration of volatile amines in the package through a color change. However, since most fluorescent pigments have some toxicity, there is a risk of contaminating food. In addition, different ammonia-sensitive properties of different fluorescent pigments are different due to different response mechanisms, so that the feedback color information has the defects of complex transmission information, single change path or small color change range. For people with poor color sensitivity, such as people with poor color, these defects will likely result in incorrect freshness information transfer, thereby risking eating spoiled food by mistake.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

A first object of the present invention is to provide a fluorescent ink having excellent fluorescence properties, which can be used for detecting volatile amines.

The second purpose of the invention is to provide a preparation method of the fluorescent ink, which is simple to operate and can realize large-scale industrial production.

The third purpose of the invention is to provide the application of the fluorescent ink in the detection of volatile amine, which has the characteristics of rapidness, high sensitivity and high selectivity.

The fourth purpose of the invention is to provide a fluorescent indicating label, which can rapidly, sensitively and highly selectively detect the volatile amine and has a lower detection limit; meanwhile, the fluorescent indicating label has good stability and can be recycled.

The fifth purpose of the present invention is to provide a method for preparing a fluorescent indicating label, so as to prepare the fluorescent indicating label with excellent performance.

The sixth purpose of the present invention is to provide a multicolor indicator, which is used in food detection, to solve the problem that the existing food freshness indicator label depends on a single color change channel or the color change range is too small, and to meet the requirement of more consumers on accurate freshness information acquisition.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

the invention provides fluorescent ink, which comprises fluorescent pigment, a binder and a solvent; the fluorescent pigment comprises curcumin and/or curcumin derivatives.

The invention also provides a preparation method of the fluorescent ink, and the fluorescent ink is obtained by uniformly mixing the raw materials.

The invention also provides application of the fluorescent ink in volatile amine detection.

The invention also provides a fluorescent indicating label which is mainly prepared from the fluorescent ink.

The invention also provides a preparation method of the fluorescent indicating label, and the fluorescent indicating label is obtained by coating the fluorescent ink on a printing stock and drying.

The invention also provides a multicolor indicator which comprises the fluorescent indicating label.

Compared with the prior art, the invention has the beneficial effects that:

(1) The invention provides fluorescent ink which is prepared from curcumin and/or curcumin derivatives serving as fluorescent pigments in different colors, can be used in the field of detection of volatile amine, can be used for effectively detecting the volatile amine, and particularly has the characteristics of high speed, high sensitivity and high selectivity in detection of ammonia gas.

(2) The invention adopts the fluorescent ink prepared by taking curcumin and/or curcumin derivatives as fluorescent pigment as the raw material, and prepares the fluorescent ink into the fluorescent indicating label with freshness detection and anti-counterfeiting functions; the characteristic gases generated in the food spoilage process, such as ammonia, dimethylamine, trimethylamine and the like, can be detected with high sensitivity, high selectivity and high speed. The fluorescent indicating label particularly shows more excellent detection performance on ammonia gas, and has low detection limit, wherein the lowest detection limit can reach 84.85ppb. Meanwhile, the fluorescent indicating label has good stability and can be repeatedly recycled.

(3) The invention provides a multicolor indicator, which can make the detection result more accurate and have high credibility by comprehensively analyzing the colors of a plurality of fluorescent indicating labels in the multicolor indicator, solve the problem that the food freshness indicating label depends on a single color change channel or the color change range is too small at present, and meet the requirements of more consumers, particularly patients with weak colors on accurate freshness information acquisition. And the multicolor indicator adopts 365nm ultraviolet light irradiation, so that accurate food freshness information can be directly acquired through naked eyes, and the cost and complexity of freshness information transmission are reduced.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 shows Cur, bur-BF ₂ And a Bur-NN ultraviolet-visible absorption spectrum (a) and a fluorescence spectrum (b).

Fig. 2 is a graph (a) of viscosity versus time, a graph (b) of viscosity versus shear rate, and a graph (c) of different fluorescent indicator labels prepared in example 1, example 5, example 6, and example 7.

FIG. 3 shows the ratio of the fluorescence intensity of SL-1, SL-2, SL-3 and SL-4 to NH ₃ Graph of concentration dependence.

FIG. 4 is a graph of the standard deviation of the response values of SL-3 andgraph (a) of the number of cycles detected and the intensity of fluorescence versus ultra-low NH ₃ Graph (b) of the linear relationship between concentrations.

FIG. 5 is a graph (a) of the fluorescence intensity of SL-3 as a function of cycle number and a graph (b) of the fluorescence response to different gases.

FIG. 6 shows NH at 0-100ppm for SL-1, SL-2, SL-3, and SL-4 ₃ Fluorescence color change map in atmosphere.

FIG. 7 is a picture of the color change of a multi-color indicator in different environments.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following detailed description, but those skilled in the art will understand that the following described examples are some, not all, of the examples of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The fluorescent ink, the preparation method and the application thereof of the embodiment of the invention are specifically described below.

Some embodiments of the present invention provide a fluorescent ink comprising a fluorescent pigment, a binder, and a solvent; the fluorescent pigment comprises curcumin and/or curcumin derivatives.

In some embodiments of the invention, the curcumin derivative comprises bisdemethoxycurcumin (Bur), a boron trifluoride derivative of bisdemethoxycurcumin (Bur-BF) ₂ ) And an azole ring derivative of bisdemethoxycurcumin (Bur-NN).

In some embodiments of the invention, bisdemethoxycurcumin (Bur) has the structural formula:

in some embodiments of the invention, a boron trifluoride derivative of bisdemethoxycurcumin (Bur-BF) ₂ ) The structural formula of (A) is:

in some embodiments of the invention, the azole ring derivative of bisdemethoxycurcumin (Bur-NN) has the formula:

in some embodiments of the invention, curcumin (Cur) has the structural formula:

specifically, in some embodiments of the present invention, the fluorescent pigment in the fluorescent ink comprises Cur, bur-BF ₂ And Bur-NN; for example, the fluorescent pigment may be Cur, but also Bur, bur-BF ₂ Or Bur-NN.

Cur is mainly separated from rhizome of Curcuma longa L, has biological activities of oxidation resistance, tumor resistance, bacteriostasis and the like, and is widely applied to the fields of food, biological pharmacy and the like. Under alkaline conditions, the color of the phenolic oxyanion changes from yellow to orange due to the formation of the phenolic oxyanion, so that the phenolic oxyanion is often used as a pH response material and can be used for alkaline gas detection. However, the symmetrical planar structure of Cur makes it prone to intermolecular pi-stacking, leading to aggregate fluorescence quenching (ACQ) effects and obstruction of rapid reversible gas sensing. Many curcumin analogs have now been synthesized and have received extensive attention in medical applications, but few reports have indicated their use as fluorescent dyes for monitoring food freshness.

(Curcuma longa)The ammonia sensitive properties of the hormone derivatives can be explained by deprotonation reactions. With bis-Bur-BF ₂ For example, a donor-acceptor-donor (D-a-D) conjugate system within the molecular structure of a molecule is capable of generating Intramolecular Charge Transport (ICT) behavior. NH as electron donor ₃ The molecule is adsorbed to Bur-BF ₂ Deprotonation of the phenol groups in the molecular chain occurs. Thus, the formation of phenol groups results which enable enhanced ICT behavior. The strong ICT behavior will increase the efficiency of electron transport in the D-a direction in the molecule, greatly impairing the electronegativity of the receptor. Therefore, the curcumin and/or curcumin derivative-based fluorescent indicator label has excellent sensitivity on ammonia gas, and can quickly and accurately detect the ammonia gas concentration in a closed atmosphere.

In some embodiments of the invention, the binder comprises one or both of hydroxyethyl cellulose and sodium hydroxymethyl cellulose; typically, but not by way of limitation, the binder is, for example, hydroxyethyl cellulose or sodium hydroxymethyl cellulose; preferably, the binder has a viscosity of 1000 to 1500 mPas at 25 ℃.

The binder plays a role in adjusting the viscosity of the ink, so that the viscosity and the addition amount of the binder are not strictly limited, and the addition amount of the binder with high viscosity is changed along with the selection of the binder with high viscosity.

In some embodiments of the invention, the solvent comprises an alcohol solution.

In some embodiments of the invention, the alcohol solution comprises one or both of an aqueous solution of ethanol and an aqueous solution of methanol; preferably, in the solvent of the fluorescent ink, the weight ratio of alcohol to water is 1.5-9; typically, but not by way of limitation, the weight ratio of alcohol to water is 1.

In some embodiments of the present invention, the mass fraction of curcumin and/or curcumin derivatives in the fluorescent ink is 0.1 to 0.5 ‰; typically, but not limitatively, the curcumin and/or curcumin derivatives are present in the fluorescent ink, for example, in a mass fraction of 0.1%, 0.2%, 0.3%, 0.4% or 0.5%.

In some embodiments of the invention, the mass fraction of the binder in the fluorescent ink is 2% to 5%; typically, but not by way of limitation, for example, the mass fraction of binder in the fluorescent ink is 2%, 3%, 4%, or 5%; preferably, the mass fraction of the binder in the fluorescent ink is 3%.

Some embodiments of the present invention further provide a preparation method of the fluorescent ink, wherein the fluorescent ink is obtained by uniformly mixing the raw materials.

Specifically, in some embodiments of the present invention, the method for preparing the fluorescent ink comprises the following steps:

uniformly mixing the transparent ink and the fluorescent pigment mother solution to obtain fluorescent ink;

the transparent ink is mainly prepared by uniformly mixing a binder and a solvent; the fluorescent pigment mother liquor is mainly prepared by uniformly mixing fluorescent pigment and solvent.

The solvent in the transparent ink comprises an aqueous solution of ethanol or an aqueous solution of methanol; the solvent in the fluorescent pigment mother liquor comprises ethanol or methanol; preferably, the weight percentage of the ethanol or the methanol in the ethanol aqueous solution or the methanol aqueous solution is 10 to 40 percent. Specifically, in some embodiments of the present invention, the solvent in the transparent ink is an aqueous solution of ethanol with a weight percentage of 10% to 40%.

Some embodiments of the present invention also provide for the use of the above-described fluorescent inks in the detection of volatile amines.

The fluorescent ink of the invention respectively adopts the Cur, the Bur and the Bur-BF ₂ Or Bur-NN is used as fluorescent pigment, and the concentration condition of the volatile amine can be sensitively detected through the change of color; and the fluorescent pigment has no toxicity and is safer in practical application.

In some embodiments of the invention, the volatile amine comprises one or more of ammonia, dimethylamine, and trimethylamine.

Some embodiments of the present invention also provide a fluorescent indicator label, which is prepared from the fluorescent ink.

Specifically, in some embodiments of the present invention, fluorescent indicator labels are separately usedWith Cur, bur-BF ₂ Or Bur-NN as the fluorescent pigment, and they were named SL-1, SL-2, SL-3, and SL-4, respectively.

The invention also provides a preparation method of the fluorescent indicating label, which comprises the steps of coating the fluorescent ink on a printing stock, and drying to obtain the fluorescent indicating label.

In some embodiments of the present invention, the coating comprises screen printing or ink jet printing; preferably, the screen-printed screen is 200 to 500 mesh.

In some embodiments of the invention, the substrate comprises one or more of security paper, glass and cotton.

Specifically, in some embodiments of the present invention, a method for preparing a fluorescent indicator label comprises the following steps: 1-3 g of printing ink is transferred to security paper by screen printing (a screen plate with 200-500 meshes), and the security paper is dried in the atmosphere of 40-70 ℃ to obtain fluorescent indicating labels with different colors.

The mesh number of the screen printing plate is changed along with the change of viscosity, and the larger the mesh number is, the viscosity of the adopted ink needs to be reduced so as to ensure that the ink can smoothly pass through the meshes. The film forming method can be replaced by ink-jet printing by screen printing, but the required viscosity is low.

Some embodiments of the present invention also provide a multicolor indicator comprising the fluorescent indicator label described above.

In some embodiments of the invention, the multicolor indicator is excited with ultraviolet light of 350-370 nm. The multicolor emission of the indicator can be achieved by only one emitter, for example, by irradiation with a 365nm ultraviolet lamp; the method is a very ideal characteristic, can reduce the cost and complexity of freshness information transmission, and can be widely popularized in real life.

Specifically, in some embodiments of the invention, the multicolor indicator comprises four fluorescent indicator labels SL-1, SL-2, SL-3, and SL-4. The four indicating labels are subjected to comprehensive color analysis, so that the concentration condition of the volatile amine can be accurately obtained, and the requirement that human beings can accurately obtain the freshness of the food through naked eyes can be met when the four indicating labels are used for detecting the freshness of the food.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

The preparation method of the fluorescent ink provided in this embodiment includes the following steps:

dissolving 3g of hydroxyethyl cellulose (HEC) in 20% by weight aqueous ethanol (w/w) to obtain 10g of a transparent ink;

dissolving 36.8mg of curcumin in 5mL of ethanol to obtain a mother solution with the concentration of 0.02 mol/L;

transferring 200 mu L of mother liquor into the transparent ink, and uniformly stirring to obtain the fluorescent ink.

Example 2

This example refers to the preparation process of example 1, except that 36.8mg of curcumin in example 1 was replaced with 30.8mg of bisdemethoxycurcumin.

Example 3

This example refers to the preparation process of example 1, except that 36.8mg of curcumin in example 1 was replaced with 35.6mg of a boron trifluoride derivative of bisdemethoxycurcumin (Bur-BF) ₂ )。

Example 4

This example refers to the preparation of example 1, except that 36.8mg of curcumin in example 1 was replaced with 30.6mg of an azole ring derivative of bisdemethoxycurcumin (Bur-NN).

Examples 5 to 7

This example refers to the preparation of example 1, with the only difference that the mass of hydroxyethyl cellulose (HEC) is 2g, 4g or 5g, respectively.

Example 8

This example refers to the preparation of example 1, except that 2g of hydroxyethyl cellulose (HEC) was dissolved in 10% by weight aqueous ethanol (w/w) to give 10g of clear ink.

Example 9

This example refers to the preparation of example 1, except that 2g of hydroxyethyl cellulose (HEC) was dissolved in 40% by weight aqueous ethanol (w/w) to give 10g of clear ink.

Example 10

The preparation method of the fluorescent indicating label provided by the embodiment comprises the following steps:

10g of fluorescent ink is transferred to security paper by screen printing (250-mesh screen plate) and dried at 40 ℃ to obtain a fluorescent indicating label;

the fluorescent ink is obtained in example 1, example 2, example 3 or example 4, and the prepared fluorescent indicator labels are named as SL-1, SL-2, SL-3 and SL-4 respectively.

Test example 1

10 mu.L of 0.02mol/L Cur, bur-BF were transferred separately ₂ And Bur-NN was further diluted with ethanol to 3mL, followed by uv-vis absorption spectrum analysis of each sample to obtain their absorption peaks, respectively, as shown in fig. 1 (a). Further, fluorescence emission spectra of samples were obtained under excitation at respective absorption maxima, and the results are shown in fig. 1 (b).

As can be seen from FIGS. 1 (a) and 1 (b), cur and Bur show significantly similar absorption spectra in ethanol, with absorption peaks of 430nm and 420nm, respectively, i.e., a strong absorption band in the 300-500nm region. The slight blue shift in the absorption spectrum of Bur compared to Cur can be attributed to the absence of methoxy groups reducing the electron absorption capacity of the molecule. The fluorescence emission peaks of Cur and Bur appear at 545nm and 515nm, respectively. After the addition of the modifying group, both the absorption spectrum and the emission spectrum of Bur were changed. Bur-BF ₂ Complexed with BF having a strong electron absorbing capacity ₂ The group causes a red-shift in both its absorption (490 nm) and emission (560 nm) spectra. For Bur-NN, it was observed that the absorption and emission spectra were blue-shifted to 320nm and 395nm, respectively, due to the excellent electron donating ability of the azole ring in Bur-NN.

Test example 2

In order to achieve a stable sensor coating on the substrate for optical characterization, the rheological properties of fluorescent inks of different HEC content were explored by dynamic viscosity, flow curve and 3-step recovery test.

At a shear rate of 0.1s ^-1 The fluorescent inks obtained in example 1 and examples 5 to 7 were subjected to a dynamic viscosity test under the conditions of (a) to obtain a graph of the relationship between the viscosity of the fluorescent ink and time, and the result is shown in fig. 2 (a).

The components undergo irregular brownian motion in the ink system, wherein the density of the HEC network determines the viscosity value of the ink. As can be seen from FIG. 2 (a), the ink containing 2wt% HEC, 3wt% HEC, 4wt% HEC and 5wt% HEC exhibited a low shear rate (0.1 s) ^-1 ) The values of viscosity at the lower end were 2.35 pas, 16.94 pas, 74.59 pas and 215.32 pas, respectively, demonstrating that the viscosity of the fluorescent ink increases with increasing HEC content.

The viscosity curve test was performed on the fluorescent inks obtained in example 1 and examples 5 to 7, respectively, to obtain a relationship curve between the viscosity and the shear rate of the fluorescent ink, and the result is shown in fig. 2 (b).

It can be seen from fig. 2 (b) that viscosity rapidly decreases (from 0.1 s) with increasing shear rate due to disruption of the HEC network ^-1 To 1000s ^-1 180 s). In addition, the shear thinning behavior indicates that these inks are non-newtonian fluids.

The fluorescent ink (10 g) disposed in example 3 was printed on paper through a screen (250 mesh) having different patterns (emblem, two-dimensional code, or english alphabet) depending on the patterning customization function of the screen printing screen, and the result was shown in fig. 2 (c) in which fluorescent indication labels having different patterns were mounted.

As can be seen from fig. 2 (c), the appropriate viscosity of the ink is beneficial to improving the precision of the printed pattern, so that the patterning of the indicator label is realized, and the anti-counterfeiting potential of the fluorescent ink of the present invention is shown.

Test example 3

By fluorescence spectrum test, four kinds of fluorescence indicating labels SL-1, SL-2, SL-3 and SL-4 are obtained to different NH ₃ Response characteristics of concentration; the results are shown in FIG. 3, wherein (a) SL-1, (b) SL-2, (c) SL-3 and (d) SL-4 are plotted as fluorescence intensity ratios (I) ₀ I) and NH ₃ Graph of concentration dependence. By standard deviation test of response values to SL-3, the mean value of the standard deviation, and the fluorescence intensity and ultra-low NH were obtained by 10 consecutive measurements ₃ The results are shown in FIG. 4, which is a linear relationship between concentrations.

The preparation method of ammonia gas with different concentrations comprises the following steps: 50mL of ammonia water with different concentrations are sealed in a 200mL conical flask and placed at room temperature overnight according to the following formula; and then obtaining saturated vapor of ammonia with different concentrations, and adopting a portable ammonia gas detector produced by Shenzhen Xin Hai scientific and technological development Limited to calibrate the ammonia gas concentration. The four types of SL-1, SL-2, SL-3 and SL-4 fluorescent indicator labels are respectively exposed to environments with different concentrations of ammonia gas. The prepared indicator labels are difficult to test using uv-vis absorption spectroscopy due to the opacity of the paper. Therefore, cur, bur-BF measured according to FIG. 1 (a) ₂ And the maximum absorption peaks of Bur-NN are respectively 430nm, 420nm, 490nm and 320nm, and the changes of the fluorescence intensity of the four fluorescence indicator labels SL-1, SL-2, SL-3 and SL-4 under different ammonia gas concentrations are tested by taking the maximum absorption peaks as excitation wavelengths.

The above formula is:

wherein, C _gas Representing the desired gas concentration (ppm), V _liquid Is the liquid NH to be injected ₃ ·H ₂ Volume of O (mL) (. Rho.) _liquid Is NH ₃ ·H ₂ Density of O (g mL) ^-1 )。MW _gas Is NH ₃ ·H ₂ Molecular weight of O (g mol) ^-1 )，V _vessel Is the volume of the container (300 mL), T _s And T _r Ambient temperature (K) and room temperature (298K), respectively.

As can be seen from FIG. 3, with NH ₃ The quenching phenomenon appears in the fluorescence intensity of the four fluorescence indicator labels when the concentration is increased (0-100 ppm). The inset illustrates the fluorescence intensity ratio (I) of the indicator label ₀ I) and NH ₃ The concentration (at least 0-50 ppm) is linear. SL-3 appears to be more pronounced than other labels during fluorescence quenchingHigher NH ₃ And (4) sensitivity.

As can be seen from FIG. 4 (a), the standard deviation test of the response values for SL-3 resulted in an average value of 1044.18 for the standard deviation of the response values (. DELTA.I). As can be seen from FIG. 4 (b), the fluorescence intensity of SL-3 with ultra-low NH ₃ The slope (slope) in a well linear relationship between concentrations was-36.92. The value of the detection limit is calculated by the following formula. The SL-3 has a minimum limit of detection (LOD) for ammonia calculated to be 84.85ppb.

Wherein, the calculation formula of LOD is:

the SL-3 is added at 50ppm NH ₃ And a cycle exposure experiment was performed in a fresh air atmosphere, and the change in fluorescence intensity of the label at 560nm during the cycle test was observed by excitation at a wavelength of 490nm, the result of which is shown in fig. 5 (a).

As can be seen from FIG. 5 (a), NH of SL-3 ₃ The reaction is reversible. When the indicator label is exposed to NH ₃ Then, fluorescence quenching occurs, and after the test is exposed in fresh air, the fluorescence intensity is restored to the original state, and the test process can be used for at least 5 times of continuous cycle detection and has excellent cycle stability.

SL-3 was mixed with 50ppm putrefactive gas (NH) respectively ₃ Dimethylamine and trimethylamine) and a high concentration gas (N) ₂ 、O ₂ And CO ₂ ) Contacted and excited at 490nm wavelength to observe the change in fluorescence intensity of the label at 560nm before and after exposure to the gas, the result of which is shown in FIG. 5 (b).

As can be seen from FIG. 5 (b), the characteristic gas (NH) generated in the process of seafood putrefaction is removed ₃ Dimethylamine and trimethylamine) and a commonly used fill gas (N) for air-conditioning packaging ₂ 、O ₂ And CO ₂ ) By sequential introduction into the test chamber, it can be seen that SL-3 is only responsive to putrefactive gases, especially to NH ₃ Is the most sensitive.

Test example 4

Using 365nm ultraviolet lamp as excitation light source, recording NH of SL-1, SL-2, SL-3 and SL-4 at 0-100ppm respectively ₃ The fluorescence color in the atmosphere changed, and the result thereof is shown in fig. 6.

As can be seen from FIG. 6, the colors of SL-1 and SL-3 change from green and yellow-green to violet-blue and light-blue, which may be due to weak fluorescence (blue) of the paper. In contrast, the color of SL-2 changes from light green to light orange. From FIG. 3b, it can be seen that SL-2 is coupled to NH ₃ A weak fluorescence peak appears at about 580nm in the response process, and the light orange appears after the fluorescence color of the self and the background is superposed. In contrast, SL-4 is at a different NH ₃ The color of the fluorescence does not change much below the concentration and shows blue fluorescence all the time.

In order to verify the practical application condition of the fluorescent indicating label, a multicolor indicator consisting of four kinds of the fluorescent indicating labels SL-1, SL-2, SL-3 and SL-4 is used for monitoring the freshness of the shrimps. The multicolor indicator is respectively placed in two shrimp packing boxes, wherein one is an environment at 6 ℃ and the other is an environment at-20 ℃, and the change of the multicolor indicator is shown in figure 7 under the irradiation of 365nm ultraviolet light.

A multi-color indicator is placed in a shrimp box and stored in two different environments. As can be seen from FIG. 7, the fluorescent color of the multicolor indicator is quenched when the shrimp are stored in an environment at 6 ℃ for 1 day. And in the environment of 20 ℃ below zero, because the deterioration of the shrimps can be effectively inhibited due to lower temperature, the shrimps are stored for 3 days in the environment of 20 ℃ below zero, and the fluorescence color of the multicolor indicator is not completely quenched. Therefore, the four fluorescent labels in the multicolor indicator are subjected to comprehensive color analysis, so that the concentration of the volatile amine in the packaging box can be accurately displayed, and the requirement that human beings accurately obtain the freshness of food through naked eyes is met.

In summary, the invention adopts Cur, bur and Bur-BF ₂ Or the Bur-NN is used as fluorescent pigment to obtain fluorescent ink with different colors, can effectively detect volatile amine, especially ammonia gas, and has the characteristics of high speed, high sensitivity and high selectivity. And the fluorescent ink can be prepared into a fluorescent indicating label with freshness detection and anti-counterfeiting functions. It can be used for checking food freshnessIn the method, accurate food freshness information can be obtained by a simple method (365 nm ultraviolet lamp irradiation), the problem that the food freshness indication label depends on a single color change channel or the color change range is too small at present is solved, and the requirements of more consumers, particularly patients with color weakness on the acquisition of the accurate freshness information are met.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made without departing from the spirit and principle of the present invention shall fall within the protection of the present invention.

Claims

1. The fluorescent ink for detecting the volatile amine is characterized by comprising a fluorescent pigment, a connecting material and a solvent;

the fluorescent pigment comprises curcumin derivatives;

the curcumin derivative is any one of a boron trifluoride derivative of bisdemethoxycurcumin and an azole ring derivative of bisdemethoxycurcumin;

the structural formula of the boron trifluoride derivative of bisdemethoxycurcumin is as follows:

the structural formula of the azole ring derivative of bisdemethoxycurcumin is as follows:

the connecting material comprises one or two of hydroxyethyl cellulose and sodium carboxymethyl cellulose;

the viscosity of the connecting material is 1000-1500 mPa.s;

the mass fraction of curcumin derivatives in the fluorescent ink is 0.1-0.5 per mill;

the mass fraction of the binder in the fluorescent ink is 2-5%.

2. The fluorescent ink for volatile amine detection according to claim 1, wherein the solvent comprises an alcohol solution.

3. The fluorescent ink for volatile amine detection according to claim 2, wherein the alcohol solution comprises one or both of an aqueous solution of ethanol and an aqueous solution of methanol.

4. A fluorescent ink for volatile amine detection according to claim 1, characterized in that the weight ratio of alcohol to water in the solvent of the fluorescent ink is 1.

5. A method for preparing the fluorescent ink for detecting volatile amine according to any one of claims 1 to 4, characterized in that the fluorescent ink is obtained by uniformly mixing the raw materials.

6. The method of claim 5 for preparing a fluorescent ink for volatile amine detection, comprising the steps of:

uniformly mixing transparent ink with fluorescent pigment mother liquor to obtain the fluorescent ink;

the transparent ink is mainly prepared by uniformly mixing a binder and a solvent; the fluorescent pigment mother liquor is mainly prepared by uniformly mixing a fluorescent pigment and a solvent.

7. The method of claim 6, wherein the solvent in the clear ink comprises an aqueous solution of ethanol or an aqueous solution of methanol;

and/or the solvent in the fluorescent pigment mother liquor comprises ethanol or methanol.

8. The method for preparing fluorescent ink for detecting volatile amine according to claim 7, wherein the weight percentage of ethanol or methanol in the aqueous solution of ethanol or methanol is 10-40%.

9. A fluorescent indicating label prepared mainly from the fluorescent ink for volatile amine detection according to any one of claims 1 to 4.

10. A method for preparing the fluorescent indicating label according to claim 9, wherein the fluorescent ink for detecting volatile amine according to any one of claims 1 to 4 is coated on a substrate and dried to obtain the fluorescent indicating label.

11. The method of making a fluorescent indicator label of claim 10, wherein the applying comprises screen printing or ink jet printing.

12. A multicolor indicator comprising the fluorescent indicator label of claim 9.

13. The multi-color indicator of claim 12, wherein the multi-color indicator is excited with ultraviolet light of 350-370 nm.