CN113621262B

CN113621262B - Polysaccharide long afterglow material and application thereof

Info

Publication number: CN113621262B
Application number: CN202110879683.2A
Authority: CN
Inventors: 朱泽策; 田迪; 曾立烦
Original assignee: Wuhan Textile University
Current assignee: Wuhan Textile University
Priority date: 2021-08-02
Filing date: 2021-08-02
Publication date: 2022-11-22
Anticipated expiration: 2041-08-02
Also published as: CN113621262A

Abstract

The invention discloses a polysaccharide long afterglow material and application thereof, wherein the long afterglow material is prepared by dehydrating polysaccharides such as cellulose, chitosan, oligosaccharide and the like serving as raw materials. The room temperature afterglow is caused by the luminescence of hydroxyl clusters in the polysaccharide, and the phosphorescence can last for more than 1 second. The materials can be used in the fields of anti-counterfeiting, information encryption, food drying indicators and the like. Compared with the existing long afterglow material, the long afterglow material disclosed by the invention is simple to prepare, and has the advantages of wide raw material source, low toxicity and less pollution.

Description

Polysaccharide long afterglow material and application thereof

Technical Field

The invention relates to a phosphorescent material with long afterglow and application thereof. The material belongs to a non-conjugated organic luminescent material, and can be used in the fields of anti-counterfeiting, information encryption, time resolution detection and the like.

Background

According to the resolution limit of naked eyes, the long afterglow material generally refers to a luminescent material with a luminescent lifetime of more than 0.1s after removing the radiation or excitation light source at room temperature (refer to Chinese patent CN 202010641989X). Due to their great potential in encryption, bio-imaging and sensing, many materials with long persistence luminescence have been developed. Conventional long afterglow materials are mainly transition metal inorganic compounds, and in order to reduce the dependence on metal resources and avoid heavy metal contamination, many organic long afterglow materials have been developed in recent years, most of which contain aromatic or heterocyclic rings (e.g. Carbazole derivatives, reference carbazoles isomers induced organic phosphorous Emission, nat. Mater. 2021, 20, 175-180), and further, some organic carbon nanodot materials also have long afterglow Luminescence (reference chloroslink-Enhanced Emission on Luminescence in Polymers: advances and perspectives. Angew. Chem. Int. Ed. 2020, 59, 9826-9840). However, the toxic and side effects and the environmental impact of the materials are not clear, and the preparation process of the materials often involves highly polluted and energy-consuming processes such as organic reaction or hydrothermal reaction, and is often accompanied by byproduct generation.

Cellulose is the oldest and most abundant renewable resource on earth, mainly derived from trees, cotton, hemp, cereals and other higher plants, and can also be produced by bacterial enzymatic processes (bacterial cellulose). (reference: wangeIn, zhang Li Na, progress on Natural Polymer materials research, journal of 2008, 7/66). Chitin is a natural polymer with second-order content to cellulose in nature, and chitosan is polysaccharide obtained by deacetylating chitin. (the references: mao Xiao Qiong, sun Qing Shen, zhao Kai, research progress of chitin and chitosan as natural biopolymer materials, high molecular report 2008, 2.45 pages). These natural polymer monomers are glucose or glucose derivatives and thus are polysaccharide organics. Different from the traditional organic luminescent materials, the polysaccharide organic matters do not contain conjugated structures such as benzene rings, heteroatom aromatic rings and the like, and generally do not emit light or emit light very weakly. In recent years, materials such as Cellulose have been found to have room temperature phosphorescence (refer to the Clustering-triggered Emission of Cellulose and Its derivatives. Chinese J. Polymer. Sci. 2019, 37, 409-415.), but they have weak luminescence, short phosphorescence lifetime, and do not have the characteristics of long afterglow luminescence. In addition, the mechanism of light emission of these non-conjugated materials is not clear, and it is difficult to regularly modify the materials to improve the phosphorescent intensity and lifetime.

Disclosure of Invention

In order to develop a low-toxicity and environment-friendly long-afterglow material and reduce energy consumption and pollutant emission in the material preparation process, the invention adopts a polysaccharide high polymer material as a raw material to prepare the long-afterglow luminescent material. It has been found through a lot of experiments that polysaccharide organic substances contain more than 3% of bound water under normal conditions (refer to Molecular dynamics of hydrolysis in Cellulose/water crystals. Cellulose, 2015, 22: 2899-2910.), and the molecules are not tightly packed due to hydrogen bonding between water molecules and the polymers, so that the phosphorescence of the materials under normal conditions is weak and the service life is short. After the bound water in some polysaccharides is removed by heating or vacuum drying and the like, the fluorescence and phosphorescence are obviously enhanced, and the long-afterglow luminescence is obvious.

The invention discloses a long afterglow material, which is characterized in that: the luminescent component of the material is polysaccharide, the polysaccharide is selected from one or more of cellulose, hemicellulose, cellosugar, chitin, chitosan oligosaccharide, inulin, xylo-oligosaccharide, fructo-oligosaccharide, malto-oligosaccharide, isomalto-oligosaccharide and maltodextrin, and the mass percentage of the polysaccharide component is not less than 20%; in this material, the water of crystallization does not exceed 1%.

The preparation method of the long afterglow material comprises the following steps: selecting raw materials containing various polysaccharides, and air drying, heating or vacuum drying to volatilize water therein to obtain the final product. After the materials are dehydrated, the phosphorescence is obviously enhanced, the phosphorescence service life can reach hundreds of milliseconds, and after the materials are excited by an ultraviolet lamp with the wavelength of 310-370nm, the obvious long-afterglow luminescence can be seen by naked eyes. The phosphorescence of these materials is mainly between 400-600 nm, and the phosphorescence peak is mostly between 450-550 nm.

Compared with the artificially synthesized long afterglow material, most of the materials are nontoxic and pollution-free, and have wide sources. For example, cellulose, hemicellulose and inulin can be extracted from plants, chitin, chitosan oligosaccharide and oligosaccharide such as shrimp and crab shell can be obtained from shrimp and crab shell, and oligosaccharide such as maltodextrin can be obtained by hydrolyzing starch.

On the basis of the materials, the invention discloses a preferable long afterglow material, which is characterized in that:

the material comprises a polysaccharide and an inorganic salt; wherein the polysaccharide is selected from one or more of cellulose, hemicellulose, cellulose sugar, chitin, chitosan oligosaccharide, inulin, xylooligosaccharide, fructooligosaccharide, maltooligosaccharide, isomaltooligosaccharide, and maltodextrinA plurality of mixtures; the inorganic salt cation is selected from

group

1 and 2 metal ions and Al ³⁺ 、Sc ³⁺ 、Zn ²⁺ 、Y ³⁺ (ii) a The inorganic salt anion is selected from chloride, bromide, sulfur, sulfate, phosphate, carbonate, nitrate ions; polysaccharide mass concentration: 10 to 99.5 percent; mass concentration of inorganic salt: 0.5 to 90 percent; the water of crystallization content does not exceed 1%.

Preferably, it is characterized in that: the inorganic salt is selected from magnesium chloride, calcium chloride, zinc chloride, aluminum chloride, yttrium chloride, sodium bromide, magnesium sulfate, and zinc sulfate.

The inorganic salts function as follows: the metal ions can generate coulomb force, overcome electrostatic repulsion between lone-pair electrons of hydroxyl groups of the polysaccharide, and enhance the aggregation of functional groups containing lone-pair electrons, such as hydroxyl groups, thereby enhancing cluster luminescence and long-afterglow luminescence. In addition, some heavy atom inorganic salts, such as magnesium bromide and yttrium chloride, are doped in the organic material to enhance the intersystem crossing efficiency, so that the long-afterglow phosphorescent emission is enhanced; heavy atoms may also promote the phosphorescent transition rate, thereby modulating the phosphorescent lifetime.

The preparation method of the long afterglow material comprises the following steps: mixing polysaccharide with inorganic salt water solution, or mixing polysaccharide suspension, solution and inorganic salt, and heating or vacuum drying to volatilize water.

Conventional cellulose and chitosan have a high degree of polymerization and poor solubility in water, which may limit their processing and application, and the water solubility of polysaccharides can be significantly improved by reducing their degree of polymerization. On the basis of the long afterglow material disclosed in the foregoing, the patent discloses a preferable long afterglow material, which is characterized in that: the polysaccharide is selected from one or more of cellose, chitosan oligosaccharide, inulin, xylooligosaccharide, fructooligosaccharide, maltooligosaccharide, isomaltooligosaccharide, and maltodextrin.

Because of the important application of the long afterglow material in the anti-counterfeiting field, people develop some paints, printing ink and the like, and the long afterglow material is marked on the surfaces of some objects by various printing technologies. The long afterglow material disclosed by the patent can also be used in paint and printing ink, and is used in the fields of anti-counterfeiting, information encryption and the like. For example, the polysaccharide solution is used as ink, does not emit light, and after writing or printing and moisture is sufficiently volatilized, the polysaccharide is gathered to emit light, so that the polysaccharide solution can be used for long-afterglow anti-counterfeiting or encryption.

The conventional polysaccharide is mostly extracted from plant tissues, and in order to simplify the extraction process of the polysaccharide, the patent discloses a long afterglow material, which is characterized in that: is derived from plant tissue, the selected plant tissue has light color or low pigment content, and is prepared by drying and dehydrating, and the content of crystal water is not more than 1%.

Plant tissues are rich in cellulose, hemicellulose and other polysaccharide compounds, so that the plant tissues are likely to have phosphorescence of cellulose after dehydration. However, some plant tissues have high pigment content, such as chlorophyll in leaves and many pigments in bark and petals, which can quench cellulose phosphorescence. Namely, the dark plant tissues are dehydrated without obvious long-afterglow luminescence.

Many light-colored plant tissues, such as cotton, cucumber, white radish, carrot, lotus root, cabbage leaf and the like, have obvious long afterglow luminescence after dehydration treatment.

The long afterglow material prepared by using the edible vegetable, fruit and plant tissues as raw materials and dehydrating is nontoxic and pollution-free, can be used in the food processing industry and can be used as a dryness indicator.

Compared with powdery cellulose (such as microcrystalline cellulose, cellulose nanocrystalline and the like), the long-lasting phosphor is prepared by directly adopting light-colored plant tissues, and the processes of purification and the like can be omitted. In addition, the plant tissue contains inorganic salt, which is beneficial to enhancing the long-afterglow luminescence.

Because cellulose and chitosan are widely applied to papermaking and spinning, many cellulose paper, cotton cloth, chitosan non-woven fabric and the like also have long afterglow after dehydration, and compared with cellulose and chitosan powder, the long afterglow material in the form of paper and fabric has better practicability. The long afterglow material can be obtained by adopting the materials through dehydration treatment, can be compatible with the preparation and processing technology of the existing paper and cloth, and can be further used for preparing various paper-based and flexible long afterglow materials to meet the application requirements of different occasions.

Therefore, on the basis of the prior art, the patent discloses a long afterglow material, which is characterized in that:

the material is paper-like or cloth-like, and the polysaccharide is selected from cellulose or chitosan.

Preferably, the long-afterglow luminescent material can be doped with inorganic salt to regulate and control the long-afterglow luminescent characteristics.

Drawings

FIG. 1 is a graph of phosphorescence delay before and after cotton dehydration.

FIG. 2 is a graph showing changes in phosphorescence retardation curves of filter paper in air after drying.

FIG. 3 is a powder diffraction pattern of cellulose at various moisture contents.

FIG. 4 is a phosphorescence spectrum of cellulose and salt-doped cellulose.

FIG. 5 is a phosphorescence spectrum of salt doped cellulose.

FIG. 6 is a plot of the phosphorescent retardation of cellulose and doped salt cellulose.

FIG. 7 is a phosphorescent retardation curve of salt-doped cellulose.

FIG. 8 is a long persistence imaging of filter paper.

Fig. 9 is a long persistence imaging of plant tissue.

FIG. 10 is a graph of the phosphorescence spectra of chitosan and chitosan doped with inorganic salts.

FIG. 11 is a graph of phosphorescence retardation curves for chitosan and chitosan doped with inorganic salts.

FIG. 12 is a phosphorescence spectrum of magnesium bromide doped chitosan.

FIG. 13 is a graph of the phosphorescence retardation of magnesium bromide doped chitosan.

FIG. 14 shows phosphorescence spectra of various chitosans.

FIG. 15 is a long persistence trace plot written in maltodextrin solution.

Detailed Description

Example 1

Cellulose long afterglow material

The preparation method comprises the following steps: respectively putting alpha cellulose (purchased from Shanghai Allatin), microcrystalline cellulose (purchased from Wanbang industries, ltd., henan) and cellulose nanocrystalline (purchased from the Kannus technology) into an oven at 90-110 ℃ for drying for more than 30 minutes to remove water sufficiently, and obtaining the long-afterglow luminescent powder. Taking out the powder to be excited by a 365nm ultraviolet LED in a dark room at room temperature, and after turning off the lamp, the yellow-green afterglow can be seen by naked eyes.

The main component of cotton and filter paper is cellulose, and the content of cellulose is above 90%. And (3) drying the absorbent cotton and the qualitative filter paper in an oven at the temperature of 90-110 ℃ for more than 30 minutes to remove water sufficiently, thus obtaining the long-afterglow luminescent cotton and the filter paper. The phosphorescence lifetime of cotton was measured by Hitachi F-4700 spectrometer, and the excitation wavelength was set at 310nm and the detection wavelength was set at 500nm, and as shown in FIG. 1, the phosphorescence of the dried cotton was significantly enhanced as compared with that of the sample that had not been dried, and the lifetime reached several hundred milliseconds or more, and the cotton had long-lasting luminescence.

The filter paper after drying was exposed to air, the phosphorescence lifetime was measured by Hitachi F-4700 spectrometer, the excitation wavelength was set to 310nm, and the detection wavelength was set to 500nm, and as a result, as shown in FIG. 2, the afterglow of the filter paper lasted for several seconds, but as the standing time increased, the filter paper gradually absorbed water from the air, resulting in gradual decrease in the afterglow intensity and duration.

Cellulose phosphorescence is derived from hydroxyl cluster luminescence, reported in the literature (Clustering-clustered Emission of Cellulose and Its derivatives, chinese J. Polymer. Sci. 2019, 37, 409-415.). X-ray powder diffraction tests were performed on cellulose before and after dehydration, and it was found that the characteristic diffraction peak (14-17 °) signal of cellulose after water absorption was significantly decreased (fig. 3), and it is presumed that water can form a hydrogen bond with the polysaccharide chains of cellulose, thereby disrupting the close packing between polysaccharide chains, i.e., water molecules disrupt the hydroxyl clusters in cellulose, resulting in quenching of luminescence. In the dried cellulose, stronger hydrogen bond action is formed among cellulose chains, hydroxyl clusters are enhanced, and further the characteristic diffraction peak (14-17 ℃) and long-afterglow luminescence of the cellulose are enhanced.

The long afterglow materials can be obtained by drying by adopting different types of cellulose and cellulose-rich materials in the above embodiments, and the afterglow luminescence of the dried cellulose is fully proved. Based on the above, other materials rich in cellulose can become long afterglow materials after being fully dehydrated, and play a role in related fields. Compared with artificially synthesized inorganic and organic long afterglow materials, the cellulose is a degradable and reproducible natural material, has wide sources, is cheap and easy to obtain, and is non-toxic and pollution-free.

Example 2

Inorganic salt doped cellulose long afterglow material

The preparation method comprises the following steps: 32 mg (0.2 mmol of sugar monomer) alpha cellulose (purchased from Shanghai Aladdin) and inorganic salt aqueous solution containing 0.2mmol are fully mixed, and then the mixture is put into a 105 ℃ oven to be dried and dehydrated, thus obtaining the long afterglow powder. Sodium chloride, potassium chloride, magnesium chloride, calcium chloride, zinc chloride, yttrium chloride, sodium bromide and magnesium bromide are respectively used as inorganic salts to prepare the long-afterglow powder of various celluloses. The delayed luminescence of these powders was measured by the method of example 1, and as a result, as shown in fig. 4 and 5, the phosphorescent intensity was significantly enhanced by doping the inorganic salt compared to the alpha-cellulose containing no inorganic salt, wherein the enhancement effect of the divalent salt and the trivalent salt was more significant than that of the monovalent salt.

Due to the fact that the divalent and trivalent metal ions have stronger coulomb force, electrostatic repulsion between hydroxyl lone pair electrons can be overcome, and cluster luminescence is enhanced. Therefore, the metal ions in the inorganic salt can play a role in enhancing cluster luminescence, so that the phosphorescence of the cellulose can be enhanced by selecting metal salts of other anions. The doped cellulose is prepared by selecting inorganic salts such as sodium carbonate, sodium dihydrogen phosphate, sodium sulfate, sodium sulfide, magnesium sulfate, zinc nitrate and the like, and the phosphorescence enhancement of different degrees can be observed.

Furthermore, the phosphorescence intensity of heavy atom-containing salts is generally higher than that of heavy atom-free salts of equivalent, for example, the order of phosphorescence intensity: sodium bromide > sodium chloride; magnesium bromide > magnesium chloride. The phosphorescence delay curves of fig. 6 and 7 show that the decay rate of phosphorescence with light element salt doping is slower, while the deceleration rate of heavy element salt is faster. This is due to the fact that heavy atoms enhance the efficiency of intersystem crossing, thereby enhancing phosphorescence and reducing the lifetime of phosphorescence, as is common knowledge in the art.

Example 3

Inorganic salt doped filter paper long afterglow material

Preparing sodium chloride, potassium chloride, magnesium chloride and calcium chloride solution with mass concentration of 2M, and adsorbing a small amount of salt solution on different areas of the same filter paper by using a capillary spotting method, as shown in FIG. 8. The filter paper is put into an oven at 105 ℃ for drying for more than 10 minutes, taken out, excited by a 365nm LED at room temperature, and photographed by a Huazhimate 10 mobile phone, a specific method reference (Luminescence lifetime imaging of ultra-long room temperature phosphor on a smart phone, analytical and biochemical Chemistry, 2021, 413, 3291-3297), and the imaging result is shown in FIG. 8, after the lamp is turned off, the phosphorescence of the filter paper area containing salt is obviously stronger than that of a blank filter paper, and the phosphorescence of the divalent salt area is stronger than that of the monovalent salt area. The results are consistent with the experimental results for alpha cellulose powder in example 2, demonstrating the enhancement of cellulose phosphorescence by inorganic salts.

Example 4

Preparation of long afterglow material from plant tissue

Cellulose is a major component of plant cell walls, and thus plants are rich in cellulose, hemicellulose, and in addition, plant tissues contain other polysaccharide components such as inulin, fructo-oligosaccharides, xylo-oligosaccharides, and the like. The removal of water from the plant tissue may cause the polysaccharides therein to develop a long persistence. Some plant tissues were selected including: cucumber slices, white radish slices, carrot slices, lotus root slices, cabbage core leaves, bamboo leaves and red Chinese rose petals; after the tissues were dried in an oven at 110 ℃ for 30 minutes or more and sufficiently dehydrated, the apparatus of example 3 was used to image, and it was found that white radish slices, carrot slices, lotus root slices, and cabbage core leaves had significant afterglow luminescence, and the afterglow duration was 1 second as shown in fig. 9. The white radish slices, the carrot slices, the lotus root slices and the Chinese cabbage core leaves are sequentially arranged from the left.

The dried bamboo leaves and red rose petals do not show long afterglow, and presumably because the colors of the bamboo leaves and the red rose petals are darker, most ultraviolet light is absorbed by pigments in the bamboo leaves and the red rose petals, so that cellulose is difficult to excite, and the pigments can quench cellulose phosphorescence through excited state energy transfer. In contrast, plant tissues with significant long persistence have low pigment content and are light in color. It is presumed that other light-colored plant tissues have long-lasting luminescence after drying and water removal.

The long afterglow material prepared by the method omits the extraction and purification process of cellulose, and the prepared long afterglow material has the appearance of plant tissues. Some of these long persistence materials are edible plant tissues that can be used in food packaging as indicators of dryness, quenching their long persistence luminescence once the package has entered moisture. Compared with drying indicators such as allochroic silica gel, the drying indicators are safer and more environment-friendly.

Example 5

Chitosan long afterglow material

Chitosan with 90% deacetylation degree (purchased from Shanghai, such as Ji Biotech development Co., ltd.) was mixed with various inorganic salt solutions according to the method of example 2, and then sufficiently dried to obtain the chitosan long afterglow material.

The phosphorescence lifetime was measured by Hitachi F-4700 spectrometer, and the excitation wavelength was set at 315nm, and the result is shown in FIG. 10, in which chitosan doped with inorganic salts had stronger phosphorescence, in which yttrium chloride was the strongest, followed by divalent salts, and again aluminum chloride, sodium chloride, and potassium chloride. Similar to the cellulose long afterglow material doped with salt, the more the metal ion charge, the stronger the coulomb force, and the more remarkable the phosphorescence enhancement.

The excitation wavelength was set at 315nm, the detection wavelength was set at 500nm, and the phosphorescence exhibited a decay change with time as shown in FIG. 11, and the phosphorescence of these materials was continued for 1 second or more.

Tests also show that the phosphorescence of the chitosan is gradually enhanced (figure 12) and the phosphorescence life is gradually reduced (figure 13) with the increase of the concentration of the doped magnesium bromide, and the typical heavy atom effect indicates that the excited state of the chitosan is regulated by heavy atoms.

Various chitosans (purchased from Shanghai Maxim Biochemical technology Co., ltd.) were mixed with magnesium bromide solution according to the method of example 2, and then fully dried to obtain various chitosan long afterglow materials. The phosphorescence lifetime of the materials was measured by Hitachi F-4700 spectrometer, and the excitation wavelength was set at 315nm, and the results are shown in FIG. 14, where the materials all showed significant long afterglow luminescence, and the phosphorescence intensity of chitosan with different deacetylation degrees was comparable except for chitosan oligosaccharide.

Example 6

Maltodextrin long afterglow: an aqueous solution was prepared containing 3.4% maltodextrin and 3.7% magnesium bromide, and the resulting solution was filled in a pen, written on printing paper, oven-dried at 105 ℃ for 10 minutes or more, and then taken out, and imaged by the apparatus and method of example 3, and as a result, as shown in fig. 15, the written area had a significant green afterglow.

The above examples demonstrate the long-lasting luminescence of various polysaccharides, and it is presumed that some other similar polysaccharides or polysaccharide analogs have long-lasting luminescence after dehydration, and the long-lasting luminescence can be significantly enhanced by doping with inorganic salts. The materials have the advantages of wide sources, simple preparation and low toxicity.

Claims

1. A long afterglow material, characterized in that: the luminescent component of the material is polysaccharide, the polysaccharide is selected from one or more of cellulose, hemicellulose, cellosugar, chitin, chitosan oligosaccharide, inulin, xylooligosaccharide, fructooligosaccharide, maltooligosaccharide, isomaltooligosaccharide and maltodextrin, and the mass percentage of the polysaccharide component is not less than 20%; in this material, the water of crystallization does not exceed 1%.

2. A long afterglow material, characterized in that: the material comprises a polysaccharide and an inorganic salt; wherein the polysaccharide is selected from one or more of cellulose, hemicellulose, cellulose sugar, chitin, chitosan oligosaccharide, inulin, xylooligosaccharide, fructooligosaccharide, maltooligosaccharide, isomaltooligosaccharide, and maltodextrin; the inorganic salt cation is selected from group 1 and 2 metal ions and Al ³⁺ 、Sc ³ ⁺ 、Zn ²⁺ 、Y ³⁺ (ii) a The inorganic salt anion is selected from chlorine,Bromine, sulfur, sulfate, phosphate, carbonate, nitrate ions; polysaccharide mass concentration: 10 to 99.5 percent; mass concentration of inorganic salt: 0.5-90%; the water of crystallization content does not exceed 1%.

3. The long afterglow material of claim 2, wherein:

the inorganic salt is selected from magnesium chloride, calcium chloride, zinc chloride, aluminum chloride, yttrium chloride, sodium bromide, magnesium sulfate, and zinc sulfate.

4. The long persistent material of claim 3, wherein: the polysaccharide is selected from one or more of cellose, chitosan oligosaccharide, inulin, xylooligosaccharide, fructooligosaccharide, maltooligosaccharide, isomaltooligosaccharide, and maltodextrin.

5. The use of the long after glow material of claim 4 in paints and inks.

6. A long afterglow material is characterized in that: is derived from plant tissue, the selected plant tissue has light color or low pigment content, and is prepared by drying and dehydrating, and the content of crystal water is not more than 1%.

7. Use of the long after glow material according to claim 6 as an indicator of dryness.