Transparent traceless long afterglow carbon dot pattern preparation method and application thereof

Abstract

The application discloses a transparent traceless long-afterglow carbon dot pattern preparation method and application thereof. In the preparation, a transparent film serving as a carbon dot precursor is prepared first; then, a preset carbon dot long-afterglow pattern is directly written on the transparent film by using a jumping laser direct writing method, and the carbon dot long-afterglow pattern is traceless and transparent under a fluorescent lamp; wherein, after a current point of the pattern is scanned, a next point which is not adjacent to the current point is scanned. The jumping laser direct writing method effectively reduces a heat affected zone, and avoids uneven heating of the substrate, so that the carbon dot long-afterglow pattern which is transparent, traceless and has high resolution is prepared. By adjusting laser parameters and carbon dot precursor types, a carbon dot pattern which has full color gamut and multi-modal emission can be obtained. The long-afterglow carbon dot pattern prepared by the application can be applied to in-situ manufacturing of flexible optoelectronic devices, including anti-fake automobile films, high-resolution codes and flexible displays.

Description

Technical Field

[0001] This invention relates to a method for preparing anti-counterfeiting chips, specifically a method for preparing long-afterglow carbon dot patterns. Background Technology

[0002] With the rapid development of the Internet of Things and big data, the demand for information storage chips with large data volumes and high security is becoming increasingly urgent. Long-persistence anti-counterfeiting labels, due to their rich excited-state characteristics, can continuously provide multiple optical states for extended periods, thus possessing enormous potential in advanced security applications. Currently, most methods for integrating long-persistence anti-counterfeiting patterns involve pre-designed masks, inkjet printing, or handwriting preparation. These methods are time-consuming and complex, hindering practical applications. Furthermore, long-persistence anti-counterfeiting patterns are typically prepared using monochromatic afterglow materials, resulting in poor processing performance, which significantly impedes their practical application.

[0003] Carbon dots (CDs) are a class of spherical nanoparticles with a size of less than 10 nm. Compared with traditional semiconductor quantum dots, they possess excellent photostability and low toxicity, demonstrating broad application prospects in numerous fields. Currently, the patterning process for afterglow CDs remains limited, exhibiting poor stability. Inkjet printing is the mainstream method for CD patterning. However, inkjet printing technology has high requirements for ink and matrix materials; currently, only a limited number of quantum dot materials and paper matrices are suitable for this method. Furthermore, because the ink bonds to the matrix through electrostatic or hydrogen bonding and is exposed on the matrix surface, it is susceptible to quenching by external environmental stimuli, resulting in poor stability. In addition, preparing high-resolution, traceless, and transparent afterglow patterned CDs remains a significant challenge. Summary of the Invention

[0004] Purpose of the invention: To address the aforementioned issues in the prior art, a transparent and traceless long-persistence carbon dot pattern preparation method is proposed to solve the problems of complex and time-consuming long-persistence patterning and integration processes, poor transparency, and unclear patterns.

[0005] Technical solution: A method for preparing a transparent, traceless, long-afterglow carbon dot pattern, comprising: first, preparing a transparent film as a carbon dot precursor; then, using a skip-type laser direct writing method to directly write a preset carbon dot long-afterglow pattern on the transparent film, wherein the carbon dot long-afterglow pattern is traceless and transparent under fluorescent light; wherein, the skip-type laser direct writing method is to scan the next point that is not adjacent to the current point of the pattern after scanning the current point of the pattern.

[0006] Furthermore, the preparation method of the carbon dot precursor includes: dissolving a nitrogen-containing compound and a polymer in deionized water and stirring thoroughly to mix them evenly, then spin-coating the mixture onto a glass surface and drying it to obtain the transparent film; wherein the nitrogen-containing compound includes one of pyrimidines, lycorine hydrochloride, and levofloxacin; and the polymer includes one of polyvinyl alcohol, polycarbonate, and polyvinylpyrrolidone.

[0007] Furthermore, in the aforementioned skip laser direct writing method, the laser wavelength is 1064nm, the laser power is 5-16W, the laser frequency is 10-25kHz, the scanning speed is 100-300mm / s, and the number of scans is 100-500.

[0008] Furthermore, the mass ratio of the nitrogen-containing compound to the polymer is 1:10 to 100.

[0009] Application of the long-persistence carbon dot pattern obtained by the method in flexible optoelectronic devices for display and information security.

[0010] Beneficial effects: 1. Compared with the traditional laser direct writing method, the laser skip scanning method proposed in this invention scans non-adjacent points after scanning one point, avoiding the problem of decreased pattern transparency and low resolution caused by heat accumulation between two adjacent points due to continuous scanning. The pattern obtained by this method is transparent and traceless, with high resolution and a minimum linewidth of 80μm, which is better than the highest value of carbon dot patterns prepared by existing methods.

[0011] 2. The long-persistence carbon dot patterns prepared by this invention have good stability and optical properties. By changing the laser parameters and carbon dot precursors, full-gamut, multimode (time-response) long-persistence phosphorescent patterns can be prepared, and the integration of multicolor, multimode long-persistence carbon dot patterns on the same thin film can be achieved. For example, the carbon dot afterglow pattern made from levofloxacin has time-response color-changing phosphorescence characteristics, and the phosphorescence color changes from orange to green over time after irradiation with ultraviolet light.

[0012] 3. The afterglow carbon dot pattern prepared by this invention can be applied to flexible optoelectronic devices, including anti-counterfeiting automotive films, high-resolution codes, and flexible displays. It also provides a design idea for the efficient and low-cost preparation of large-scale patterned afterglow carbon dot films. Attached Figure Description

[0013] Figure 1 Digital photographs of the patterned area before and after irradiation with 365nm ultraviolet light;

[0014] Figure 2 Fluorescence microscope images obtained using the skip laser direct writing method;

[0015] Figure 3The UV transmission spectra of the patterned area and the blank sample are shown; the inset shows a photograph of the pattern under sunlight.

[0016] Figure 4 The fluorescence and afterglow spectra of the patterned region under different scan times under 365nm ultraviolet irradiation;

[0017] Figure 5 Transmission electron microscopy images of CDs at different scan numbers;

[0018] Figure 6 Multicolor dynamic afterglow image of levofloxacin CD film;

[0019] Figure 7 For flexible display and information security applications, the designs include letters and safety exit patterns, as well as protective patterns for mobile phones and cars. Detailed Implementation

[0020] The invention will now be further explained with reference to the accompanying drawings.

[0021] Example 1:

[0022] 0.1 g of 4-diamino-6-hydroxypyrimidine was dissolved in 3 g of a 7% (w / w) PVA (polyvinyl alcohol) aqueous solution and mixed thoroughly. The mixture was then spin-coated onto a glass slide and allowed to air dry to remove residual moisture, yielding a transparent film as a carbon dot precursor. A pre-defined carbon dot afterglow pattern was directly written onto the transparent film using a pulsed laser with a wavelength of 1064 nm, a power of 16 W, and a frequency of 10 kHz. The skip-stroke laser writing method involves scanning one dot of the pattern, then scanning the next non-adjacent dot, ultimately forming the pre-defined pattern from consecutive dots. At a laser scanning speed of 200 mm / s and 200 scans, the pattern exhibited blue fluorescence under ultraviolet light. As the number of scans increased from 300 to 500, afterglow appeared, gradually changing from green to yellowish-green.

[0023] The carbon dot afterglow pattern obtained in this embodiment is detected, such as... Figures 1 to 5 .

[0024] Figure 1 The image shows digital photographs of a laser-written pattern before and after irradiation with 365nm ultraviolet light, taken at a scanning speed of 200mm / s and 300 scans. As can be seen from the image, the pattern exhibits blue fluorescence and green afterglow before and after ultraviolet light irradiation, respectively.

[0025] Figure 2 Fluorescence micrographs taken at a scanning speed of 200 mm / s and 200 scans. Figure 2 This indicates that a high-resolution pattern with a minimum linewidth of 80 micrometers can be obtained using the skip laser direct writing method.

[0026] Figure 3 The images show the ultraviolet transmission spectra of the blank sample and the direct-write area; the inset shows a photograph of the pattern under sunlight. As can be seen from the figure, the transmittance of the pattern area is as high as 95% in the wavelength range of 400-800 nm, similar to that of the blank sample. This is very important for practical applications, especially in the field of optoelectronic devices.

[0027] Figure 4 The fluorescence (left) and afterglow (right) spectra of the patterned region under different scan numbers under 365nm ultraviolet irradiation are shown. The fluorescence spectrum shows that the fluorescence intensity gradually increases. Under 365nm ultraviolet excitation, the emission redshifts from 415nm to 470nm. After 300 scans, the fluorescence is detected to switch to afterglow. As the number of scans is further increased to 500, the afterglow peak moves from 415nm to 525nm, corresponding to the color change from blue to greenish-yellow.

[0028] Figure 5 The images are transmission electron microscope (TEM) images of CDs at a scanning speed of 200 mm / s. Figure (a) corresponds to 200 scans, Figure (b) corresponds to 300 scans, and Figure (c) corresponds to 500 scans. The TEM images show that the synthesized carbon dots exhibit a uniform and well-dispersed quasi-spherical morphology with average sizes of approximately 7.5, 8.5, and 9.8 nm.

[0029] Example 2

[0030] 0.1g of levofloxacin was dissolved in 3g of a 7% (w / w) PC (polycarbonate) aqueous solution and mixed thoroughly. The mixture was then spin-coated onto a glass slide and allowed to air dry to remove residual moisture, resulting in a transparent film serving as a carbon dot precursor. A pre-defined carbon dot afterglow pattern was directly written onto the transparent film using a 1064nm pulsed laser with a power of 10W and a frequency of 15kHz. In this method, after scanning one dot of the pattern, the next non-adjacent dot is scanned, ultimately forming the pre-defined pattern from consecutive dots. At a scanning speed of 100mm / s and 200 scans, the written pattern exhibited a unique time-dependent response after 1 second of 395nm illumination, with the phosphorescence color changing from orange to green over time. Red phosphorescence was observed after 425nm illumination.

[0031] Figure 6 This is a multicolor dynamic afterglow image of a levofloxacin CD film. The image shows that the CD mode exhibits a unique time-dependent phosphorescence change from orange to green one second after the 395nm lamp is turned off. Furthermore, red phosphorescence is observed after 425nm illumination. This unique phenomenon originates from the presence of dual phosphorescent centers with different attenuation rates within the CD.

[0032] Example 3

[0033] 0.1g of lycorine hydrochloride was dissolved in 3g of a 7% (w / w) PVP (polyvinylpyrrolidone) aqueous solution. After thorough mixing, the solution was spin-coated onto a glass slide and allowed to air dry to remove residual moisture, resulting in a transparent film as a carbon dot precursor. A pre-defined carbon dot afterglow pattern was directly written onto the transparent film using a 1064nm pulsed laser with a power of 5W and a frequency of 25kHz. The hop-step laser writing method involves scanning one dot of the pattern, then scanning the next non-adjacent dot, ultimately forming the pre-defined pattern from consecutive dots. At a scanning speed of 300mm / s and 100 scans, the written pattern exhibited green phosphorescence after UV irradiation.

[0034] Example 4

[0035] 0.021 g of 4-diamino-6-hydroxypyrimidine was dissolved in 3 g of a 7% (w / w) PVA (polyvinyl alcohol) aqueous solution and mixed thoroughly. The mixture was then spin-coated onto a glass slide and allowed to air dry to remove residual moisture, yielding a transparent film as a carbon dot precursor. A pre-defined carbon dot afterglow pattern was directly written onto the transparent film using a pulsed laser with a wavelength of 1064 nm, a power of 16 W, and a frequency of 10 kHz. The skip-stroke laser writing method involves scanning one dot of the pattern, then scanning the next non-adjacent dot, ultimately forming the pre-defined pattern from consecutive dots. At a laser scanning speed of 200 mm / s and 200 scans, the pattern exhibited blue fluorescence under ultraviolet light. As the number of scans increased from 300 to 500, afterglow appeared, gradually changing from green to yellowish-green.

[0036] Example 5

[0037] 0.0021 g of 4-diamino-6-hydroxypyrimidine was dissolved in 3 g of a 7% (w / w) PVA (polyvinyl alcohol) aqueous solution and mixed thoroughly. The mixture was then spin-coated onto a glass slide and allowed to air dry to remove residual moisture, yielding a transparent film as a carbon dot precursor. A pre-defined carbon dot afterglow pattern was directly written onto the transparent film using a pulsed laser with a wavelength of 1064 nm, a power of 16 W, and a frequency of 10 kHz. The skip-step laser writing method involves scanning one dot of the pattern, then scanning the next non-adjacent dot, ultimately forming the pre-defined pattern from consecutive dots. At a laser scanning speed of 200 mm / s and 200 scans, the pattern exhibited blue fluorescence under ultraviolet light. As the number of scans increased from 300 to 500, afterglow appeared, gradually changing from green to yellowish-green.

[0038] Implementation Case 6

[0039] Application of the long-persistence carbon dot patterns obtained in Examples 1 to 4 in flexible optoelectronic devices for display and information security.

[0040] Based on a skip-type laser direct writing method, carbon dot luminescent patterns of different shapes were prepared by adjusting laser parameters, demonstrating its potential applications in display and anti-counterfeiting. QR codes with implicit information were directly written onto a glass surface. During the day, the QR codes cannot be recognized due to the seamlessness and high transparency of the thin film. Encrypted blue fluorescent and green afterglow QR codes were obtained before and after irradiation with 365nm ultraviolet light, respectively, and can be recognized by a scanner.

[0041] like Figure 7 As shown, patterns such as letters and emergency exit symbols can also be directly laser-written onto the film, displaying different color patterns before and after ultraviolet light excitation. Furthermore, patterned CD films with ultra-high transparency and excellent flexibility can be used in mobile phone and automotive protective films. Their transparent and residue-free properties make these CD films ideal for display and information security applications.

[0042] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Unless otherwise specified in the embodiments, the conditions are performed according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

Claims

1. A method for preparing transparent, traceless, long-afterglow carbon dot patterns, characterized in that, include: First, a transparent thin film was prepared as a carbon dot precursor. Then, a preset carbon dot long afterglow pattern is directly written on the transparent film using a skip laser direct writing method. The carbon dot long afterglow pattern is invisible and transparent under fluorescent light. The skip laser direct writing method is to scan the next point that is not adjacent to the current point after scanning the current point of the pattern. The method for preparing the carbon dot precursor includes: dissolving a nitrogen-containing compound and a polymer in deionized water and stirring thoroughly to mix them evenly, then spin-coating the mixture onto a glass surface and drying it to obtain the transparent film; wherein the nitrogen-containing compound is one of 4-diamino-6-hydroxypyrimidine, lycorine hydrochloride, and levofloxacin; and the polymer is one of polyvinyl alcohol, polycarbonate, and polyvinylpyrrolidone. In the aforementioned skip laser direct writing method, the laser wavelength is 1064 nm, the laser power is 5~16 W, the laser frequency is 10~25 kHz, the scanning speed is 100~300 mm / s, and the number of scans is 100~500. The mass ratio of the nitrogen-containing compound to the polymer is 1:10~100.

2. The application of the long-persistence carbon dot pattern obtained by the method according to claim 1 in flexible optoelectronic devices for display and information security.

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