Long-life phosphorescent sulfur quantum dot, multicolor long-life phosphorescent sulfur quantum dot composition, and preparation method and application of multicolor long-life phosphorescent sulfur quantum dot composition

Abstract

The invention discloses a long-life phosphorescent sulfur quantum dot, a multicolor long-life phosphorescent sulfur quantum dot composition and a preparation method and application thereof, and belongs to the technical field of phosphorescent materials and information encryption. The preparation method comprises the following steps: carrying out solvothermal reaction on a sulfur source and ethylenediamine to obtain sulfur quantum dots, and adding a sulfur quantum dot aqueous solution into a boric acid matrix to react to prepare long-life phosphorescent sulfur quantum dots (SQDs-MA); the long-life phosphorescent sulfur quantum dots and a rhodamine B aqueous solution are blended and dried to prepare the multicolor long-life phosphorescent sulfur quantum dot composition (RhB / SQDs-MA). When excited by ultraviolet light, the SQDs-MA shows a wide absorption range of 200 to 700 nm. When excitation is carried out at 362 nm, the SQDs-MA shows a blue fluorescence emission peak at 436 nm. The SQDs-MA powder emits bright green phosphorescence after the irradiation of an ultraviolet lamp is turned off, and under the optimal excitation of 373 nm, the maximum phosphorescence emission value is displayed at 526 nm. Under the irradiation of ultraviolet light, the RhB / SQDs-MA can emit yellow, orange and red phosphorescence at the wavelength of 584 nm, 600 nm and 620 nm.

Description

Technical Field

[0001] The present invention belongs to the technical field of phosphorescent materials and information encryption, and specifically relates to a long-lifetime phosphorescent sulfur quantum dot, a multicolor long-lifetime phosphorescent sulfur quantum dot composition, and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Room temperature phosphorescence (RTP), defined as the continuous emission after the excitation source is stopped, has attracted extensive attention in photonics, electronics and bioelectronics due to its high exciton utilization, large Stokes shift and long emission lifetime. Conventional commercial RTP materials are currently limited to inorganic phosphors containing rare earth ions or transition metals, which have obvious disadvantages, including high toxicity, strict processing conditions and high cost. In contrast, organic molecules and polymers have become the focus of research due to their advantages such as low toxicity, flexible design and easy functionalization. In the past decade, a series of high-performance organic RTP materials have been successfully developed by introducing heavy / heteroatoms, functional groups and distorted molecular structures to enhance the spin-orbit coupling (SOC) process, and by using methods such as crystal engineering, polymer encapsulation, supramolecular assembly and host-guest doping to construct a rigid molecular environment to suppress non-radiative transitions. However, the inherent challenges of these materials in processability and biocompatibility significantly limit their ability to meet the diverse needs in photonic applications.

[0004] Luminescent quantum dots, especially metal-free quantum dots such as carbon, silicon, and sulfur, have attracted much attention due to their unique optical properties, cost-effectiveness, low toxicity, good biocompatibility, and remarkable water solubility, and have broad application prospects covering a wide range of fields from optoelectronic devices to biomedicine. Notably, sulfur quantum dots (SQDs) are derived from sublimated sulfur, a residual and recyclable petrochemical byproduct with environmental challenges. Sulfur quantum dots stand out among these quantum dots due to their sustainability, unique chemical properties, and remarkable intrinsic bioactivity, especially in antimicrobial therapy. In recent years, high-performance fluorescent sulfur quantum dots with multicolor emission, high quantum yield, and excellent stability have been successfully developed through innovative methods such as assembly fission, H2O2-assisted synthesis, oxygen acceleration, and surface functionalization. However, despite significant progress in revealing the relationship between fluorescence (FL) properties and sulfur quantum dot structure, the development of room temperature phosphorescent (RTP) materials based on sulfur quantum dot systems still faces major challenges. To the best of our knowledge, there are almost no reports on the generation of RTP from SQDs, which is mainly due to the weak SOC of sulfur element and the lack of obvious excited triplet states. At present, the emission colors of most room temperature phosphorescent materials are limited to blue and green. Compared with monochromatic phosphorescence, multicolor phosphorescence has more superior application potential in display, imaging, information encryption and anti-counterfeiting. Therefore, the development of multicolor phosphorescent materials based on sulfur quantum dot system has important scientific significance and practical value. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, the present invention provides a long-lifetime phosphorescent sulfur quantum dot, a multicolor long-lifetime phosphorescent sulfur quantum dot composition, and a preparation method and application thereof. The long-lifetime phosphorescent sulfur quantum dot exhibits bright green phosphorescence (RTP) at 526nm and a long lifetime of 221ms. In addition, through the efficient triplet-to-singlet conversion between the phosphorescent sulfur quantum dot and rhodamine B, the long-lifetime phosphorescent sulfur quantum dot exhibits bright green phosphorescence (RTP) at 526nm and a long lifetime of 221ms. A series of multicolor afterglow materials have been developed by resonance energy transfer (TS-FRET). Compared with organometallic complex materials, the phosphorescent sulfur quantum dots have the advantages of being simple, rapid, metal-free, long-lived, cost-effective, and low-toxic.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] In the first aspect, the present invention provides a long-lifetime phosphorescent sulfur quantum dot, which includes an S-S bond, an SC bond, a CN bond or a C=C bond, and the average particle size of the sulfur quantum dot is 3-5nm. When excited by ultraviolet light, the phosphorescent sulfur quantum dot emits blue fluorescence; after the ultraviolet light irradiation is turned off, it emits green phosphorescence.

[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned long-life phosphorescent sulfur quantum dots, comprising the following steps:

[0009] The sulfur source and ethylenediamine undergo a solvothermal reaction to obtain sulfur quantum dots, and an aqueous solution of the sulfur quantum dots is added into a boric acid matrix to react and prepare phosphorescent sulfur quantum dots.

[0010] In a third aspect, the present invention provides a multicolor long-lifetime phosphorescent sulfur quantum dot composition, comprising the long-lifetime phosphorescent sulfur quantum dots according to claim 1 and rhodamine B;

[0011] Under ultraviolet light irradiation, the multicolor long-lifetime phosphorescent sulfur quantum dot composition exhibits yellow, orange and red phosphorescent emissions at 584 nm, 600 nm and 620 nm.

[0012] In a fourth aspect, the present invention provides a method for preparing the above-mentioned multicolor long-lifetime phosphorescent sulfur quantum dot composition, comprising the following steps: blending the long-lifetime phosphorescent sulfur quantum dots described in claim 1 and an aqueous solution of Rhodamine B, and drying to prepare a multicolor long-lifetime phosphorescent sulfur quantum dot composition.

[0013] In a fifth aspect, the present invention provides applications of the above-mentioned long-lived phosphorescent sulfur quantum dots and the above-mentioned multicolor long-lived phosphorescent sulfur quantum dot composition in the fields of phosphorescent display, anti-counterfeiting security or optical information encryption.

[0014] In a sixth aspect, the present invention provides a photoelectric device for phosphorescent display, comprising an emission layer and an LED array, wherein the above-mentioned long-life phosphorescent sulfur quantum dot powder is used as the emission layer.

[0015] In a seventh aspect, the present invention provides a carrier for information encryption, wherein the long-lifetime phosphorescent sulfur quantum dots are used as fluorescent powders, and a quick response code containing encrypted information is printed on the carrier; preferably, the carrier is paper.

[0016] In an eighth aspect, the present invention provides a dynamic information encryption system, comprising the above-mentioned long-lived phosphorescent sulfur quantum dots and the above-mentioned multi-color long-lived phosphorescent sulfur quantum dot composition.

[0017] In a ninth aspect, the present invention provides a Morse code encryption product, comprising the above-mentioned long-lifetime phosphorescent sulfur quantum dots and the above-mentioned multi-color long-lifetime phosphorescent sulfur quantum dot composition.

[0018] The reaction mechanism of the present invention is as follows: the sulfur quantum dots, long-lifetime phosphorescent sulfur quantum dots and multicolor long-lifetime phosphorescent sulfur quantum dot compositions provided by the present invention use sublimated sulfur powder as a sulfur source precursor and ethylenediamine (EDA) as a solvent, and react under high temperature and high pressure conditions. EDA cleaves the sulfur ring through the thiamine reaction and is incorporated into the sulfur ring by forming a CS bond, thereby synthesizing sulfur quantum dots (SQDs). Boric acid (BA) is further heat-treated, first dehydrated and cyclized to form metaboric acid (MA), and then deaminated and oxidized with SQDs to form a CB bond, ultimately generating long-lifetime phosphorescent sulfur quantum dots (SQDs-MA). Under ultraviolet light, green phosphorescence can be emitted. SQDs-MA is mixed with an aqueous solution of rhodamine B (RhB) and then reacted with the mixture. Resonance energy transfer produces a multicolor long-lifetime phosphorescent sulfur quantum dot composite (RhB / SQDs-MA), which can emit yellow, orange and red phosphorescence under ultraviolet light.

[0019] One or some of the above technical solutions have the following advantages or beneficial effects:

[0020] 1. The long-lifetime phosphorescent sulfur quantum dots (SQDs-MA) and multicolor long-lifetime phosphorescent sulfur quantum dot compositions (RhB / SQDs-MA) provided by the present invention exhibit a wide absorption range of 200-700nm when excited by ultraviolet light, and exhibit a blue fluorescence emission peak at 436nm (lifetime of 2.73ns) when excited at 362nm. The SQDs-MA powder emits bright green phosphorescence after the ultraviolet light irradiation is turned off, and exhibits a phosphorescence emission maximum at 526nm (lifetime of 221ms) under the optimal excitation of 373nm. Under ultraviolet light irradiation, RhB / SQDs-MA exhibits yellow, orange and red phosphorescence emissions at 584nm, 600nm and 620nm. Matrix constraints are used to suppress non-radiative transitions and stabilize the triplet state of SQDs, thereby achieving high-performance multicolor RTP.

[0021] 2. The preparation method of the long-lifetime phosphorescent sulfur quantum dots and the multicolor long-lifetime phosphorescent sulfur quantum dot composition of the present invention uses sublimated sulfur powder as a sulfur source precursor and ethylenediamine (EDA) as a solvent to react under high temperature and high pressure conditions to synthesize sulfur quantum dots (SQDs). Boric acid (BA) is further heat-treated to form a CB bond with SQDs through deamination and oxidation, and finally generates phosphorescent sulfur quantum dots (SQDs-MA). SQDs-MA is mixed with an aqueous solution of rhodamine B and then Resonance energy transfer obtains a multicolor long-lifetime phosphorescent sulfur quantum dot composition (RhB / SQDs-MA). Its preparation process is simple and fast, easy to operate, and has a high yield; the preparation process does not require complex and expensive equipment, has a low cost, and does not produce other harmful substances during the preparation process, and is easy to achieve industrial production. Therefore, the preparation process of the multicolor long-lifetime phosphorescent sulfur quantum dot composition has the advantages of being simple, fast, metal-free, long-life, economical and effective, and low toxicity.

[0022] 3. The long-lifetime phosphorescent sulfur quantum dots (SQDs-MA) and multicolor long-lifetime phosphorescent sulfur quantum dot compositions (RhB / SQDs-MA) prepared by the present invention are phosphorescent materials that can produce different phosphorescence lifetimes after receiving excitation. Based on the above characteristics of the material, the material has good application prospects in the fields of information encryption and optical information storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 The fluorescence excitation and emission of the SQDs solution and the liquid UV-visible absorption spectrum in Example 1;

[0025] Figure 2 It is the fluorescence excitation emission MAP spectrum of the SQDs solution in Example 1;

[0026] Figure 3 The fluorescence lifetime decay spectrum of the SQDs solution in Example 1;

[0027] Figure 4 The fluorescence excitation and emission spectra of the SQDs-MA prepared in Example 1;

[0028] Figure 5 The fluorescence excitation emission MAP spectrum of SQDs-MA prepared in Example 1;

[0029] Figure 6 The fluorescence lifetime decay spectrum of SQDs-MA prepared in Example 1;

[0030] Figure 7 Phosphorescence excitation and emission and solid UV-visible absorption spectrum of SQDs-MA prepared in Example 1;

[0031] Figure 8 This is the phosphorescence excitation emission MAP spectrum of the SQDs-MA prepared in Example 1;

[0032] Fig. 9This is the phosphorescence lifetime decay spectrum of the SQDs-MA prepared in Example 1;

[0033] Fig.10 The phosphorescence emission spectra of the SQDs-MA prepared in Example 1 at different reaction temperatures; wherein the reaction temperatures are 160°C, 180°C, 200°C, 220°C and 240°C respectively;

[0034] Fig.11 The phosphorescence lifetime decay spectrum of SQDs-MA prepared in Example 1 at different reaction temperatures;

[0035] Fig.12 The phosphorescence emission spectra of SQDs-MA prepared in Example 1 at different reaction times; wherein the reaction times are 1h, 2h, 3h, 4h and 5h respectively;

[0036] Fig.13 The phosphorescence lifetime decay spectrum of the SQDs-MA prepared in Example 1 at different reaction times;

[0037] Fig.14 The phosphorescence emission spectra of the SQDs-MA prepared in Example 1 at different SQDs doping ratios; wherein the doping ratios are 0.19%, 0.24%, 0.33%, 0.49% and 0.99% respectively;

[0038] Fig.15 The phosphorescence lifetime decay spectrum of the SQDs-MA prepared in Example 1 at different SQDs doping ratios;

[0039] Fig.16 The phosphorescence emission spectra of the SQDs-MA prepared in Example 1 at different temperatures; wherein the temperatures are 60K, 100K, 140K, 180K, 220K, 260K and 300K respectively;

[0040] Fig.17 The phosphorescence lifetime decay spectrum of the SQDs-MA prepared in Example 1 at different temperatures;

[0041] Fig.18 The phosphorescence emission photos of the SQDs-MA prepared in Example 1 in different solvents; wherein the solvents are water, N,N-dimethylformamide (DMF), acetone (AC), dimethyl sulfoxide (DMSO), n-hexane (n-Hexane) and ethanol (EA);

[0042] Fig.19 The phosphorescence lifetime decay spectra of SQDs-MA prepared in Example 1 in different solvents;

[0043] Fig. 20The curve of the fluorescence emission spectrum of the SQDs-MA prepared in Example 1 after irradiation with excitation light for 100 minutes as a function of time (5-minute intervals);

[0044] Fig.21 The curve of the phosphorescence emission spectrum of the SQDs-MA prepared in Example 1 after 100 minutes of excitation light irradiation as a function of time (5 minutes interval);

[0045] Fig. 22 The fluorescence and phosphorescence emission intensities of the SQDs-MA prepared in Example 1 after 100 minutes of excitation light irradiation;

[0046] Fig.23 The phosphorescence emission spectra of the SQDs-MA prepared in Example 1 under different atmospheres; wherein the atmospheres are Ar, N2, O2 and air respectively;

[0047] Fig.24 The phosphorescence lifetime decay spectra of the SQDs-MA prepared in Example 1 under different atmospheres;

[0048] Fig.25 The phosphorescence emission intensity spectrum of SQDs-MA prepared in Example 1 at different pH values;

[0049] Fig.26 The phosphorescence lifetime decay spectrum of SQDs-MA prepared in Example 1 at different pH values;

[0050] Fig. 27 TEM image of SQDs-MA prepared in Example 1;

[0051] Fig.28 The size distribution of SQDs-MA prepared in Example 1;

[0052] Fig.29 X-ray diffraction analysis patterns of SQDs, SQDs-MA and standard card (JCPDF:08-0247) prepared in Example 1;

[0053] Fig.30 X-ray diffraction analysis patterns of SQDs-MA prepared in Example 1 and a standard card (JCPDF: 77-0425);

[0054] Fig.31 IR spectra of SQDs, SQDs-MA and BA prepared in Example 1;

[0055] Fig.32 Electron paramagnetic resonance images of SQDs and SQDs-MA prepared in Example 1;

[0056] Fig.33This is the X-ray photoelectron spectrum of the SQDs-MA prepared in Example 1;

[0057] Fig.34 The phosphorescence emission spectrum, the fluorescence emission spectrum and the UV-visible absorption spectrum of the SQDs-MA prepared in Example 1 are shown in FIG.

[0058] Fig.35 The fluorescence emission spectra of RhB / SQDs-MA (RhB with different doping ratios) prepared in Example 1;

[0059] Fig.36 The fluorescence lifetime decay spectra of RhB / SQDs-MA (RhB with different doping ratios) prepared in Example 1;

[0060] Fig.37 The phosphorescence emission spectra of RhB / SQDs-MA (RhB with different doping ratios) prepared in Example 1;

[0061] Fig.38 The color coordinate spectrum of RhB / SQDs-MA (RhB with different doping ratios) prepared in Example 1;

[0062] Fig.39 The phosphorescence lifetime decay spectrum of RhB / SQDs-MA (RhB with different doping ratios) prepared in Example 1;

[0063] Fig.40 Application of RhB / SQDs-MA prepared in Example 1 in the field of phosphorescent display;

[0064] Fig.41 Application 1 of the SQDs-MA prepared in Example 1 in the field of optical information encryption;

[0065] Fig.42 Application 2 of the RhB / SQDs-MA prepared in Example 1 in the field of optical information encryption;

[0066] Fig.43 Application 3 of the RhB / SQDs-MA prepared in Example 1 in the field of optical information encryption. DETAILED DESCRIPTION

[0067] As described in the background technology, in view of the shortcomings of existing phosphorescent materials such as high cost, strong toxicity, and complex preparation process, and there are almost no reports on the generation of RTP by SQDs, in order to solve the above technical problems, the present invention proposes a long-lifetime phosphorescent sulfur quantum dot, a multicolor long-lifetime phosphorescent sulfur quantum dot composition, and its preparation method and application. The preparation method comprises the following steps: using sublimated sulfur powder as a sulfur source precursor and ethylenediamine (EDA) as a solvent, reacting under high temperature and high pressure conditions to obtain sulfur quantum dots (SQDs). Adding an aqueous solution of SQDs to a boric acid (BA) matrix, phosphorescent sulfur quantum dots (SQDs-MA) are prepared under high temperature and high pressure conditions. SQDs-MA is blended with an aqueous solution of rhodamine B, and a multicolor long-lifetime phosphorescent sulfur quantum dot composition (RhB / SQDs-MA) is prepared by freeze drying. If the reaction time, reaction temperature, solvent, and matrix are changed, the generation of long-lifetime phosphorescent sulfur quantum dots and multicolor long-lifetime phosphorescent sulfur quantum dot compositions will be affected, thereby reducing the phosphorescence decay life and the delay time at room temperature.

[0068] The present invention has found that the reaction solvent ethylenediamine and the boric acid matrix are very important for preparing long-life phosphorescent sulfur quantum dots. If the reaction solvent is replaced with other solvents such as propylenediamine and diethylenetriamine, and other reaction conditions remain the same, the obtained sulfur quantum dots have no fluorescence or very weak fluorescence. If the reaction matrix is ​​replaced with other matrices such as cyanuric acid, melamine, polyvinyl alcohol and silicon dioxide, the obtained long-life phosphorescent sulfur quantum dots have no phosphorescence or very weak phosphorescence.

[0069] In a first typical embodiment, the present invention provides a long-lifetime phosphorescent sulfur quantum dot, which includes an S-S bond, an SC bond, a CN bond or a C=C bond, and the average particle size of the sulfur quantum dot is 3-5nm. When excited by ultraviolet light, the phosphorescent sulfur quantum dot emits blue fluorescence; after the ultraviolet light irradiation is turned off, green phosphorescence is emitted.

[0070] When excited by ultraviolet light, the sulfur quantum dot aqueous solution produces a blue fluorescence emission peak with a wavelength of 428nm (lifetime of 3.74ns) at the optimal excitation wavelength of 350nm. SQDs-MA powder shows a phosphorescence emission maximum at 526nm (lifetime of 221ms) under the optimal excitation of 373nm. When excited by ultraviolet light, SQDs-MA exhibits a wide absorption range of 200-700nm.

[0071] In a second typical embodiment, the present invention provides a method for preparing the above-mentioned long-lifetime phosphorescent sulfur quantum dots, comprising the following steps:

[0072] Sulfur quantum dots (SQDs) are obtained by solvothermal reaction between a sulfur source and ethylenediamine, and an aqueous solution of sulfur quantum dots is added into a boric acid (BA) matrix to react and prepare phosphorescent sulfur quantum dots (SQDs-MA).

[0073] In some examples of this embodiment, the sulfur source is sublimated sulfur powder. The purity of the sublimated sulfur powder is 99% or more. The purity of anhydrous ethylenediamine is 99% or more.

[0074] In some examples of this embodiment, the mass volume ratio of the sulfur source to ethylenediamine is (0.2-0.6 g):(2-6 mL).

[0075] In some examples of this embodiment, the sulfur source and ethylenediamine are stirred at room temperature for 5-10 minutes before the solvothermal reaction. Preferably, the mixed solution can be ultrasonically treated to make the mixed solution more uniform.

[0076] In some examples of this embodiment, the solvent thermal reaction has a reaction temperature of 140-190° C. and a heating time of 1-7 hours. If the temperature is too high, the reaction is excessive and the fluorescence becomes weak; if the temperature is too low, the fluorescence becomes weak and the quantum yield decreases.

[0077] In some examples of this embodiment, the sulfur quantum dots are further subjected to rotary evaporation, washing and purification, centrifugal drying, and other steps to finally obtain sulfur quantum dot powder. The drying is performed by heating in a drying oven, and the washed sulfur quantum dots are heated in the open air.

[0078] In some examples of this embodiment, the purity of the boric acid is 99% or more.

[0079] In some examples of this embodiment, the usage ratio of sulfur quantum dots, boric acid and water is (0.01-0.03g):(1-5g):(5-10mL), preferably 0.01g:(1-5g):5mL, and further preferably 0.01g:(2-3g):5mL.

[0080] In some examples of this embodiment, before reacting to prepare phosphorescent sulfur quantum dots, the sulfur quantum dots, boric acid and water are mixed and stirred at room temperature for 5-15 minutes. Preferably, the mixed solution can be ultrasonically treated to make the mixed solution more uniform.

[0081] In some examples of this embodiment, during the reaction to prepare phosphorescent sulfur quantum dots, the reaction temperature is 160-240°C and the heating time is 1-5 hours. Preferably, the reaction temperature is 200-220°C and the heating time is 2-3 hours. If the temperature is too high, the reaction is excessive and the phosphorescence becomes weak; if the temperature is too low, bonding is difficult, and there is no phosphorescence or the phosphorescence becomes weak.

[0082] In some examples of this embodiment, the mixed reaction solution obtained after the reaction of the sulfur quantum dot aqueous solution and the boric acid (BA) matrix is ​​dried for 2-5 hours to obtain SQDs-MA powder. The drying is drying in a drying oven, and the specific drying process is to heat the lining after the reaction in a drying oven to obtain SQDs-MA powder.

[0083] In a third typical embodiment, the present invention provides a multicolor long-lived phosphorescent sulfur quantum dot composition, comprising the above-mentioned long-lived phosphorescent sulfur quantum dots and rhodamine B; under ultraviolet light irradiation, the multicolor long-lived phosphorescent sulfur quantum dot composition exhibits yellow, orange and red phosphorescent emissions at 584nm, 600nm and 620nm.

[0084] In a fourth typical embodiment, the present invention provides a method for preparing the above-mentioned multicolor long-lifetime phosphorescent sulfur quantum dot composition, comprising the following steps: mixing the above-mentioned phosphorescent sulfur quantum dots and a rhodamine B (RhB) aqueous solution, and drying to prepare a multicolor long-lifetime phosphorescent sulfur quantum dot composition (RhB / SQDs-MA).

[0085] In some examples of this embodiment, the purity of rhodamine B is 95% or more. The concentration of the rhodamine solution is 5-6 mg / mL.

[0086] In some examples of this embodiment, the mass volume ratio of phosphorescent sulfur quantum dots, rhodamine B and water is (250-300 mg):(3-150 μL):(5-10 mL), preferably 300 mg:(3-150 μL):5 mL.

[0087] In some examples of this embodiment, during the blending, stirring is performed at room temperature for 5-15 minutes. Preferably, the mixed solution can be subjected to ultrasonic treatment to make the mixed solution more uniform.

[0088] In some examples of this embodiment, the drying is freeze-drying, and the drying time is 24-48 hours.

[0089] In a fifth typical embodiment, the present invention provides applications of the above-mentioned long-lifetime phosphorescent sulfur quantum dots and multicolor long-lifetime phosphorescent sulfur quantum dot compositions in the fields of phosphorescent display, anti-counterfeiting security or optical information encryption.

[0090] In a sixth typical embodiment, the present invention provides a phosphorescent display optoelectronic device, including an emission layer and an LED array, wherein the above-mentioned SQDs-MA powder is used as the emission layer.

[0091] In a seventh typical embodiment, the present invention provides an information encrypted carrier, wherein the above-mentioned SQDs-MA is used as a phosphor, and a quick response code containing encrypted information is printed on the carrier. Preferably, the carrier may be paper. After the ultraviolet excitation light source is turned off, the code can still be scanned and recognized.

[0092] In an eighth typical embodiment, the present invention provides a dynamic information encryption system, comprising the above-mentioned SQDs-MA and RhB / SQDs-MA materials, wherein when ultraviolet light is excited, a dot pattern displaying blue and red FL will show unrecognizable invalid information; when the excitation light source is terminated, two dot patterns of different colors appear at 1 second and 2 seconds, and two misleading codes are generated by converting the binary code into ASCII code; after the ultraviolet light is turned off, after an interval of 3 seconds, the remaining code composed of the green afterglow emitted by the SQDs-MA becomes clearly visible and corresponds to the ASCII representation.

[0093] In a ninth typical embodiment, the present invention provides a Morse code encryption product, comprising the above-mentioned SQDs-MA and RhB / SQDs-MA materials.

[0094] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0095] Example 1

[0096] 1. Preparation of sulfur quantum dots:

[0097] 0.5 g of sublimated sulfur powder was dissolved in 5 mL of EDA and stirred at room temperature for 5 minutes. The mixture was transferred to a 50 mL Teflon-lined stainless steel autoclave and heated at 170 °C for 5 hours. After the reaction was completed, the excess EDA was removed by rotary evaporation. The product was then washed with ethanol several times and centrifuged to obtain sulfur quantum dots (SQDs) powder.

[0098] 2. Preparation of long-life phosphorescent sulfur quantum dots:

[0099] 0.01 g of SQDs powder and 3 g of BA were dissolved in 5 mL of deionized water and stirred at room temperature for 5 minutes. The mixture was transferred to a 50 mL Teflon-lined stainless steel autoclave, heated at 200 ° C for 2 hours, and then cooled naturally to room temperature. The resulting solution was dried in an oven at 100 ° C for 3 hours to obtain phosphorescent sulfur quantum dots (SQDs-MA) powder.

[0100] In this experimental procedure, the doping rate of SQDs is 0.33%. The steps of other doping ratios (0.99%, 0.49%, 0.24% and 0.19%) are the same as this step, the only difference is the amount of boric acid added (1g, 2g, 4g and 5g respectively). That is, the doping amount of boric acid in the long-life phosphorescent sulfur quantum dots is 0.19% to 0.99%.

[0101] SQDs doping rate = SQDs amount / (BA amount + SQDs amount)*100%

[0102] 3. Preparation of multicolor long-lifetime phosphorescent sulfur quantum dot composition:

[0103] 300 mg SQDs-MA powder and different amounts of RhB solution (3, 8, 20, 60 and 150 μL) were dissolved in 5 mL of deionized water and stirred at room temperature for 10 minutes. RhB / SQDs-MA was obtained by freeze drying. Among them, the concentration of RhB solution was 5 mg / mL. The doping ratios were 0.005%, 0.013%, 0.03%, 0.1% and 0.25%, respectively. That is, in the multi-color long-lifetime phosphorescent sulfur quantum dot composition, the doping amount of RhB was 0.005% to 0.25%.

[0104] RhB doping rate = RhB amount / (SQDs-MA amount+RhB amount)*100%

[0105] like Figure 1 As shown, the sulfur quantum dot aqueous solution prepared in this example emits bright blue fluorescence under ultraviolet light (365nm), and the maximum emission peak is 428nm at the optimal excitation wavelength of 350nm. The sulfur quantum dot aqueous solution exhibits a significant absorption peak centered at 338nm, accompanied by a wide absorption range of 230 to 500nm. Figure 2 As shown in Figure 2, the fluorescence excitation (FL) emission peak of sulfur quantum dot aqueous solution does not change with the excitation wavelength, indicating that it has no excitation dependence. Figure 3 As shown, the fluorescence decay lifetime of sulfur quantum dots aqueous solution can reach up to 3.74ns. SQDs-MA powder emits bright blue fluorescence under ultraviolet light (365nm).

[0106] like Figure 4 As shown in Figure 2, the maximum emission peak of SQDs-MA powder is 436 nm at the optimal excitation wavelength of 362 nm. Figure 5 As shown in Figure 2, the FL emission peak of SQDs-MA powder does not change with the excitation wavelength, indicating that it has no excitation dependence. Figure 6 As shown, the fluorescence decay lifetime of SQDs-MA powder can reach up to 2.73ns.

[0107] like Figure 7As shown, the SQDs-MA powder emits bright green phosphorescence after the UV lamp irradiation is turned off, and the maximum emission peak is 526nm at the optimal excitation wavelength of 373nm. The UV-visible absorption spectrum of SQDs-MA shows an obvious peak at about 215nm and a broad absorption band centered at 316nm, which can be attributed to the (n, σ*) transition of non-bonding electrons from sulfur atoms and the band gap transition of zero-valent sulfur, respectively. In addition, the other two absorption peaks at 273nm and 380nm may be due to the (π, π*) and (n, π*) transitions in SQDs-MA. As shown Figure 8 As shown in Figure 2, the RTP emission peak of SQDs-MA powder changes with the excitation wavelength, indicating that it is excitation-dependent. Fig. 9 As shown, the phosphorescence decay lifetime of SQDs-MA powder can reach up to 221ms.

[0108] like Figure 10-15 As shown, the optimal conditions for preparing SQDs-MA powder are 200 °C and 2 h, and the optimal doping ratio is 0.33%.

[0109] like Figure 16-17 As shown, the RTP strength and lifetime of SQDs-MA powders become stronger and longer as the temperature decreases.

[0110] like Figure 18-26 As shown in Figure 2, SQDs-MA still maintains good RTP stability under various solvents, excitation light, atmosphere and pH conditions. This may be due to the strong protection and sealing effect provided by the highly rigid and stable MA.

[0111] like Figure 27-28 As shown, the SQDs are firmly and densely embedded in the rigid matrix MA, which helps to activate the (n, π*) transition of SQDs, with an average particle size of 4.08 nm.

[0112] like Figure 29-30 As shown, the X-ray diffraction (XRD) pattern of SQDs is similar to some diffraction peaks observed in the orthorhombic S8 phase (JCPDF:08-0247), which confirms the characteristics of SQDs nanoparticles. The XRD pattern of SQDs-MA shows multiple sharp peaks corresponding to the characteristic peaks of MA (PDF:77-0425), indicating that BA undergoes dehydration condensation to form MA during heat treatment.

[0113] like Fig.31 As shown in Figure 2, the chemical structures of SQDs and SQDs-MA were characterized by Fourier transform infrared spectroscopy. The Fourier transform infrared spectra of SQDs were 1616, 1192, 671 and 536 cm -1Characteristic peaks appeared at 1050 cm-1, corresponding to the stretching vibrations of C=C, CN, CS and SS bonds. The results showed that EDA successfully modified the surface of SQDs by forming CS bonds. A careful comparison of the Fourier transform infrared spectra of SQDs-MA and BA revealed that SQDs-MA had a peak at 1050 cm-1. -1 A new absorption peak appeared at 925 cm, which may correspond to the stretching vibration of the BOB bond. The formation of the BOB bond may be due to the polycondensation process of BA, resulting in the production of cyclized MA. In addition, compared with the single SQDs, the Fourier transform infrared spectrum of SQDs-MA showed a strong peak at 925 cm -1 The prominent CB bond vibration is shown at , which confirms the existence of covalent bonds between SQDs and MA in addition to encapsulation. This interaction greatly helps to establish a stable confinement environment, effectively restricting the vibration and rotation of SQDs.

[0114] like Fig.32 As shown in Figure 3, the covalent bond binding effect of the highly rigid MA matrix played a key role in activating the RTP of SQDs-MA, which was further confirmed by electron spin resonance (EPR) spectroscopy. Fig.33 As shown, the X-ray photoelectron spectroscopy spectrum of SQDs-MA also clearly shows the related bond types of C=C, C–B, C–N / C–S, B–O–B, B–OH and S–S.

[0115] like Fig.34 As shown, RhB is a widely used commercial fluorescent dye that has a significant absorbance overlap with the RTP spectrum of the donor SQDs-MA and was therefore selected as the sensitizing acceptor to tune the afterglow color of SQDs-MA.

[0116] like Figure 35-39 As shown in the figure, with the increase of RhB doping concentration, the steady-state FL emission spectrum of RhB / SQDs-MA shows that the FL emission of SQDs-MA gradually weakens, while the FL emission of RhB significantly enhances. At the same time, the fluorescence lifetime of SQDs-MA decreases with the increase of RhB doping concentration, which is due to the singlet exciton to singlet exciton FRET (SS-FRET) process from SQDs-MA to RhB. In addition, with the increase of RhB doping concentration, the delayed fluorescence intensity of RhB is significantly enhanced, while the phosphorescence intensity of SQDs-MA gradually weakens, which confirms the existence of TS-FRET from SQDs-MA to RhB. It is worth noting that with the increase of doping concentration, the visible afterglow color of RhB / SQDs-MA gradually transitions from green to red, which is consistent with the quantitative characteristics of the International Commission on Illumination (CIE) coordinates, clearly demonstrating the effectiveness of the TS-FRET strategy in achieving multicolor afterglow.

[0117] Application Example 1: Application in phosphorescent display field

[0118] The optoelectronic device for emergency safety signs was fabricated by using SQDs-MA powder as the emission layer and integrating an LED array through a circuit diagram. The switching of the LED array is precisely controlled by a corresponding computer program. Fig.40 As shown, when the power is cut off, the unit will emit a bright green "EXIT" residual light.

[0119] Application Example 2 Application of Information Encryption 1

[0120] The potential of SQDs-MA materials in multi-level information encryption is demonstrated. Fig.41 As shown in the figure, we used SQDs-MA as a phosphor to print a quick response (QR) code containing the information "Room Temperature Phosphores cent Material: Sulfur Quantum Dots" on paper by offset printing. Due to the long lifetime of SQDs-MA, the code can still be scanned and recognized after the UV excitation light source is turned off. Impressively, even after the excitation light source is turned off for 3 seconds, the information can still be immediately recognized in a dark environment due to the extremely high brightness and resolution of the green afterglow.

[0121] Application Example 3: Information Encryption Application 2

[0122] The successful application of a single material in optical encryption has prompted us to further explore the use of different emission colors and time-varying properties for innovative functional integration. Fig.42 As shown in the figure, we proposed a dynamic information encryption system based on a 4×6 dot pattern by taking advantage of the time-varying multi-color afterglow characteristics of SQDs-MA and RhB / SQDs-MA materials. The operation rules are as follows: These quaternions are then combined in sequence, converted into binary, and decoded into information using the ASCII (American Standard Code for Information Interchange) code table. When excited by ultraviolet light, the dot pattern showing blue and red FL appears as invalid information that cannot be recognized. Subsequently, when the excitation light source is terminated, two dot patterns of different colors appear at 1 second and 2 seconds, and two misleading codes are generated by converting the binary code into ASCII code. After the ultraviolet light is turned off, after an interval of 3 seconds, the remaining code composed of the green afterglow emitted by SQDs-MA becomes clearly visible and corresponds to the ASCII representation showing the 16-digit sequence "AEOTDNULASOH".

[0123] Application Example 4 Application of Information Encryption 3

[0124] like Fig.43In addition, a Morse code encryption technique using SQDs-MA and RhB / SQDs-MA materials is proposed, in which different afterglow colors are assigned to the dots represented by “●” and The time-varying afterglow encryption pattern is initially converted into binary code through Morse code transformation and then into alphabetic information. After removing the excitation light source for different durations, different Morse code patterns are generated, corresponding to different characters. Specifically, after stopping the excitation light for 1 to 3 seconds, the generated characters are decoded as "OFY9", "TNNG" and "TT", respectively. Therefore, by adopting time-varying multi-color afterglow materials, Morse code, as a globally recognized encryption method, can be further enhanced, thereby improving the confidentiality of the code and promoting its universal applicability.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A long-lifetime phosphorescent sulfur quantum dot, characterized in that: The sulfur quantum dots include S-S bonds, SC bonds, CN bonds or C=C bonds, and the average particle size of the sulfur quantum dots is 3-5nm. When excited by ultraviolet light, the phosphorescent sulfur quantum dots emit blue fluorescence; and emit green phosphorescence after the ultraviolet light irradiation is turned off.

2. The method for preparing long-lifetime phosphorescent sulfur quantum dots according to claim 1, characterized in that: The following steps are involved: The sulfur source and ethylenediamine undergo a solvothermal reaction to obtain sulfur quantum dots, and an aqueous solution of the sulfur quantum dots is added into a boric acid matrix to react and prepare phosphorescent sulfur quantum dots.

3. The preparation method according to claim 2, characterized in that: The sulfur source is sublimated sulfur powder; Preferably, the mass volume ratio of the sulfur source and ethylenediamine is (0.2-0.6 g): (2-6 mL); Preferably, the solvent thermal reaction has a reaction temperature of 140-190° C. and a heating time of 1-7 hours; Preferably, the usage ratio of sulfur quantum dots, boric acid and water is (0.01-0.03 g):(1-5 g):(5-10 mL); preferably 0.01 g:(1-5 g):5 mL; Preferably, in the process of preparing phosphorescent sulfur quantum dots by the reaction, the reaction temperature is 160-240° C. and the heating time is 1-5 hours.

4. A multicolor long-lifetime phosphorescent sulfur quantum dot composition, characterized in that: Comprising the long-lifetime phosphorescent sulfur quantum dots according to claim 1 and rhodamine B; Under ultraviolet light irradiation, the multicolor long-lifetime phosphorescent sulfur quantum dot composition exhibits yellow, orange and red phosphorescent emissions at 584 nm, 600 nm and 620 nm.

5. The method for preparing the multicolor long-lifetime phosphorescent sulfur quantum dot composition according to claim 4, characterized in that: The method comprises the following steps: mixing the long-lifetime phosphorescent sulfur quantum dots described in claim 1 with an aqueous solution of rhodamine B, and drying to prepare a multicolor long-lifetime phosphorescent sulfur quantum dot composition; Preferably, the concentration of the rhodamine B solution is 5-6 mg / mL; Preferably, the mass volume ratio of phosphorescent sulfur quantum dots, rhodamine B and water is (250-300 mg):(3-150 μL):(5-10 mL), preferably 300 mg:(3-150 μL):5 mL; Preferably, the drying is freeze drying, and the drying time is 24-48 hours.

6. Application of the long-lived phosphorescent sulfur quantum dots according to claim 1 and the multicolor long-lived phosphorescent sulfur quantum dot composition according to claim 4 in the fields of phosphorescent display, anti-counterfeiting security or optical information encryption.

7. A phosphorescent display optoelectronic device, characterized in that: It comprises an emission layer and an LED array, wherein the long-life phosphorescent sulfur quantum dot powder described in claim 1 is used as the emission layer.

8. An information encrypted carrier, characterized in that: The long-life phosphorescent sulfur quantum dots described in claim 1 are used as phosphors, and a quick response code containing encrypted information is printed on a carrier; preferably, the carrier is paper.

9. A dynamic information encryption system, characterized in that: The invention comprises the long-lifetime phosphorescent sulfur quantum dots as described in claim 1 and the multicolor long-lifetime phosphorescent sulfur quantum dots composition as described in claim 4.

10. A Morse code encryption product, characterized in that: The invention comprises the long-lifetime phosphorescent sulfur quantum dots as described in claim 1 and the multicolor long-lifetime phosphorescent sulfur quantum dots composition as described in claim 4.

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