Device and method for preparing rare earth ion doped nanocrystals through femtosecond laser ablation

Abstract

The invention provides a device and a method for preparing rare earth ion doped nanocrystals by femtosecond laser ablation. Comprising a femtosecond laser used for emitting femtosecond pulse laser, an optical element group used for focusing the femtosecond pulse laser on the surface of a blocky rare earth ion doped crystal in a beaker, and an electric control rotating table used for driving the beaker to rotate, the method has the beneficial effects that the rare earth ion doped nanocrystal is prepared in the surfactant solution by femtosecond pulse laser ablation, and meanwhile, in the laser ablation process, the ablation crystal and the surfactant solution in the beaker are rotated through the electric control rotary table; the ultrafast femtosecond laser is applied and the surfactant is reasonably used, so that the aggregation of the nanocrystal in the preparation process can be remarkably inhibited, the size of the nanocrystal is further reduced, and the uniformity of the size of the nanocrystal is improved; the method has the advantages of simple preparation equipment, green and environment-friendly production process, good nanocrystal size uniformity and the like.

Description

Technical Field

[0001] The invention relates to the technical field of laser processing and nano material preparation, and in particular to a device and method for preparing rare earth ion-doped nano crystals by femtosecond laser ablation. Background Art

[0002] Rare earth ion doped nanocrystals have attracted extensive attention as a biomarker material with great potential due to their low toxicity and high photostability. Wet chemistry is a common technique for preparing nanoparticles. However, it has the problems of complex procedures, long time consumption and residual toxicity, which limits the wide application of wet chemistry in the biomedical field. Pulsed laser ablation is a simple and efficient method for preparing nanoparticles. Nanoparticles can be prepared directly from bulk materials. Generally speaking, it can be carried out in a variety of environments, including vacuum, gas and liquid environments. Compared with pulsed laser ablation in vacuum or gas environments, pulsed laser ablation in liquid environments has more extreme conditions, such as higher temperature, stronger plasma confinement and greater shock pressure. These factors may limit the growth of nanoparticles and help reduce the size of nanoparticles.

[0003] Compared with picosecond and nanosecond pulse lasers, femtosecond lasers have unique advantages. Femtosecond pulse lasers can rapidly cool the ablated particles during the ablation process, thereby inhibiting particle aggregation and reducing particle size. Therefore, the preparation of rare earth-doped nanocrystals by femtosecond lasers has the advantages of simple preparation equipment, small nanoparticle size, and green preparation process. Therefore, a method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation is urgently needed. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an apparatus and method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation, so as to solve the problems of the existing preparation technology, such as complex preparation equipment, large nanoparticle size and non-green preparation process.

[0005] In order to achieve the above-mentioned purpose and other related purposes, the present invention provides the following technical solutions:

[0006] A device for preparing rare earth ion doped nanocrystals by femtosecond laser ablation comprises a femtosecond laser for emitting femtosecond pulse laser, an optical element group for focusing the femtosecond pulse laser on the surface of a bulk rare earth ion doped crystal in a beaker, and an electric and electrically controlled rotating table for placing the beaker containing the bulk rare earth ion doped crystal and driving the beaker to rotate, wherein the optical element group is located on the emission light path of the femtosecond laser, and the electric and electrically controlled rotating table is located below the optical element group.

[0007] In one embodiment of the present invention, the optical element group includes a first convex lens and a concave lens for reducing the diameter of the femtosecond pulse laser beam, a reflector for reflecting the reduced femtosecond pulse laser, and a second convex lens for focusing the reflected femtosecond pulse laser on the surface of a bulk rare earth ion-doped crystal in a beaker; wherein the first convex lens is located between the femtosecond laser and the concave lens, the concave lens is located between the first convex lens and the reflector, the second convex lens is located below the reflector, and the electric and electrically controlled rotating stage is located below the second convex lens.

[0008] A method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation, based on the device for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation, comprises the following steps: adding a surfactant aqueous solution into a beaker, and placing the beaker on an electric and electrically controlled rotating table; placing a block of rare earth ion-doped crystals at the bottom of the beaker containing the surfactant aqueous solution; using a femtosecond laser to emit a femtosecond pulse laser, and using the femtosecond pulse laser as a laser ablation light source, wherein the beam diameter of the femtosecond pulse laser is reduced after the femtosecond pulse laser passes through a concave lens and a first convex lens;

[0009] The femtosecond pulse laser after being shrunken is focused on the surface of the bulk rare earth ion doped crystal through a reflector and a second convex lens, so that rare earth ion doped nanocrystals can be prepared from the bulk rare earth ion doped crystal; at the same time, during the ablation process, the electric and electrically controlled rotating table drives the beaker and the liquid and crystal inside it to rotate through its own rotation.

[0010] In one embodiment of the present invention, the surfactant aqueous solution is 12 ml of dodecyldimethylaminoacetic acid betaine (LDA) aqueous solution, wherein the concentration of the LDA aqueous solution is 0.1 mol / L.

[0011] In one embodiment of the present invention, the femtosecond pulse laser is an ultrashort pulse laser with a wavelength of 515 nm and a repetition frequency of 1 kHz. The ablation energy density of the femtosecond pulse laser is about 0.29 J / cm 2 .

[0012] In one embodiment of the present invention, during the ablation process, the electric and electrically controlled rotating table drives the beaker and the liquid and crystal therein to rotate at a speed of 30 revolutions per minute.

[0013] As described above, the device and method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation of the present invention have the following beneficial effects: the present invention uses femtosecond pulse laser ablation in a surfactant solution to prepare rare earth ion-doped nanocrystals, and during the laser ablation process, the ablated crystals and the surfactant solution in the beaker are rotated by an electric and electrically controlled rotating table; the present invention can significantly inhibit the aggregation of nanocrystals during the preparation process by using ultrafast femtosecond lasers and reasonably using surfactants, thereby further reducing the size of the nanocrystals and improving the uniformity of the nanocrystal size; the present invention has the advantages of simple preparation equipment, green and environmentally friendly production process, and good uniformity of nanocrystal size. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Shown is a schematic diagram of the overall structure of a device for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation disclosed in an embodiment of the present invention;

[0015] Figure 2 Shown is a schematic diagram of the overall process of the method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation disclosed in an embodiment of the present invention;

[0016] Figure 3 The YAG:Ce prepared in LDA aqueous solution in the method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation disclosed in the embodiment of the present invention is shown. 3+ Schematic representation of a transmission electron microscope image of a nanoparticle.

[0017] Component number description

[0018] 1. Femtosecond laser; 2. First convex lens; 3. Concave lens; 4. Reflector; 5. Second convex lens; 6. Beaker; 7. Electric and electrically controlled rotating table. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0020] The first embodiment of the present invention relates to a device for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation. Figure 1 , comprising a femtosecond laser 1 for emitting femtosecond pulse laser, an optical element group for focusing the femtosecond pulse laser on the surface of a bulk rare earth ion-doped crystal in a beaker 6, and an electric and electrically controlled rotating table 7 for placing the beaker 6 containing the bulk rare earth ion-doped crystal and driving the beaker 6 to rotate, the optical element group being located on the emission light path of the femtosecond laser 1, and the electric and electrically controlled rotating table 7 being located below the optical element group;

[0021] The optical element group includes a first convex lens 2 and a concave lens 3 for reducing the diameter of the femtosecond pulse laser beam, and the first convex lens 2 is located between the femtosecond laser 1 and the concave lens 3; the optical element group also includes a reflector 4 for reflecting the femtosecond pulse laser after the beam is reduced, and a second convex lens 5 for focusing the reflected femtosecond pulse laser on the surface of the block rare earth ion doped crystal in the beaker 6, the concave lens 3 is located between the first convex lens 2 and the reflector 4, the second convex lens 5 is located below the reflector 4, and the electric and electrically controlled rotating stage 7 is located below the second convex lens 5;

[0022] Specifically, the femtosecond laser 1 is a femtosecond laser ablation light source. The beam diameter of the femtosecond pulse laser emitted by the femtosecond laser 1 will be reduced after passing through the first convex lens 2 and the concave lens 3; the reduced beam of the femtosecond pulse laser enters the reflector 4 at an angle of 45 degrees, and the reflected femtosecond pulse laser passes through the second convex lens 5 and is focused on the surface of the block crystal in the beaker 6. At the same time, during the ablation process, the beaker 6 and the liquid and crystal inside it are rotated by the electric and electrically controlled rotating table 7.

[0023] The second embodiment of the present invention relates to a method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation. The method uses a femtosecond laser to prepare rare earth ion-doped nanocrystals in an aqueous solution of an amphoteric surfactant. The process is as follows: Figure 2 As shown, the details are as follows:

[0024] Step 101 , add a surfactant aqueous solution into a beaker 6 , and place the beaker 6 on an electric and electrically controlled rotating table 7 .

[0025] Specifically, the surfactant aqueous solution is 12 ml of dodecyldimethylaminoacetic acid betaine (LDA) aqueous solution, wherein the concentration of the LDA aqueous solution is 0.1 mol / L.

[0026] Step 102 , placing a block of rare earth ion-doped crystals at the bottom of a beaker 6 containing an aqueous surfactant solution.

[0027] Step 103, using the femtosecond laser 1 to emit femtosecond pulse laser, and using the femtosecond pulse laser as a laser ablation light source, the beam diameter of the femtosecond pulse laser will be reduced after the femtosecond pulse laser passes through the first convex lens 2 and the concave lens 3.

[0028] Specifically, the femtosecond pulse laser is an ultrashort pulse laser with a wavelength of 515nm and a repetition frequency of 1kHz. The ablation energy density of the femtosecond pulse laser is about 0.29J / cm 2 .

[0029] In step 104, the femtosecond pulse laser after being shrunk is focused on the surface of the bulk rare earth ion-doped crystal through the reflector 4 and the second convex lens 5, so that rare earth ion-doped nanocrystals can be prepared from the bulk rare earth ion-doped crystal; at the same time, during the ablation process, the electric and electrically controlled rotating table 7 drives the beaker 6 and the liquid and crystal inside it to rotate through its own rotation.

[0030] Specifically, during the ablation process, the electric and electrically controlled rotating table 7 drives the beaker 6 and the liquid and crystals therein to rotate at a speed of 30 revolutions per minute.

[0031] More specifically, a method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation in the present invention can also be described in detail as follows: first, a bulk rare earth ion-doped crystal is placed at the bottom of a beaker 6, and the beaker 6 is filled with 12 ml of a dodecyldimethylaminoacetic acid betaine (LDA) aqueous solution, and the concentration of the LDA aqueous solution is 0.1 mol / L; then, an ultrashort femtosecond pulse laser with a wavelength of 515 nm and a repetition frequency of 1 kHz is used as a laser ablation light source, and the laser ablation light source is reduced in beam diameter after passing through a first convex lens 2 and a concave lens 3; the reduced laser ablation light source is focused on the surface of the bulk rare earth ion-doped crystal through a reflector 4 and a second convex lens 5, and the ablation energy density of the femtosecond pulse laser is about 0.29 J / cm 2 Moreover, during the ablation process, the beaker 6 is rotated at a speed of 30 revolutions per minute by using an electric and electrically controlled rotating table 7, thereby improving the ablation efficiency.

[0032] Further, the principle of the present invention is: when a femtosecond pulse laser is irradiated onto the surface of a material, since the pulse width is much shorter than the electron-phonon coupling time, the ablation process mainly manifests as non-equilibrium heating, and a high-temperature and high-pressure plasma is generated through multi-photon absorption and avalanche ionization, thereby achieving ablation;

[0033] The liquid environment allows for more extreme conditions during pulsed laser ablation of bulk materials, such as higher temperature, stronger plasma confinement and greater impact pressure, which can limit the growth of nanoparticles. In addition, the LDA solution selected in the present invention is used as a surfactant for preparing rare earth ion-doped nanocrystals because LDA molecules, as amphoteric surfactant molecules, have better attraction with rare earth ion-doped nanocrystals. In the interface region between the expanding plasma and the liquid, when the instantaneous temperature is higher than the melt temperature, oxygen vacancies are easily generated, and the surface of the quenched rare earth ion-doped nanocrystal clusters is positively charged. As an anionic surfactant, LDA molecules have local negative charges. Therefore, in the LDA aqueous solution, due to the attraction between the positively charged surface of the rare earth ion-doped nanocrystals and the negatively charged LDA molecules, the rare earth ion-doped nanocrystals are surrounded by the LDA molecules to form double-layer micelles, which limits the agglomeration of the rare earth ion-doped nanocrystals, thereby resulting in smaller sizes of the prepared rare earth ion-doped nanocrystals.

[0034] Furthermore, YAG:Ce was prepared in LDA aqueous solution by femtosecond pulse laser. 3+ Taking nanocrystals as an example, under femtosecond pulse laser ablation with a wavelength of 515nm and a repetition frequency of 1kHz, YAG:Ce with a size of about 4nm was obtained. 3+ Nanocrystals; Figure 1 The invention relates to a device for preparing rare earth ion doped nanocrystals by femtosecond pulse laser ablation in a surfactant solution environment. A femtosecond laser 1 reduces the diameter of a femtosecond pulse laser beam through a first convex lens 2 and a concave lens 3. The reduced femtosecond pulse laser enters a reflector 4 at an angle of 45 degrees. The reflected femtosecond pulse laser passes through a second convex lens 5 and is focused on the surface of a block crystal in a beaker 6. The beaker 6 and the liquid and crystal inside the beaker 6 are rotated by an electric and electrically controlled rotating table 7.

[0035] Figure 3 YAG:Ce prepared in LDA aqueous solution 3+ Transmission electron microscopy images of nanoparticles, such as Figure 3 As shown in the transmission electron microscopy image, multiple spherical particles of equal size and dispersion are presented, which indicates that the YAG:Ce prepared in LDA aqueous solution 3+ The nanoparticles have good dispersion, less agglomeration and good uniformity of particle size; the inset is a high-resolution transmission electron microscopy image of the nanoparticles, which shows parallel and orderly stripes, indicating that the YAG:Ce prepared in LDA solution 3+ The nanoparticles have good crystallinity, and the lattice spacing of the prepared nanocrystals is 0.269nm, which is similar to that of YAG:Ce 3+The (420) crystal plane of the crystal corresponds to that of the (420) crystal, which confirms that the femtosecond laser ablation process does not destroy the crystalline properties of the bulk crystal target; thus, rare earth ion-doped nanocrystals can be prepared efficiently and quickly by femtosecond laser ablation in a surfactant solution.

[0036] In summary, the present invention uses femtosecond pulse laser ablation in a surfactant solution to prepare rare earth ion-doped nanocrystals. During the laser ablation process, the ablated crystals and the surfactant solution in the beaker 6 are rotated by an electric and electrically controlled rotating table 7. The present invention can significantly inhibit the aggregation of nanocrystals during the preparation process by using ultrafast femtosecond lasers and reasonably using surfactants, thereby further reducing the size of the nanocrystals and improving the uniformity of the size of the nanocrystals. The present invention has the advantages of simple preparation equipment, green and environmentally friendly production process, and good uniformity of the size of the nanocrystals.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. All equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A device for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation, characterized in that: The invention comprises a femtosecond laser (1) for emitting femtosecond pulse laser light, an optical element group for focusing the femtosecond pulse laser light on the surface of a bulk rare earth ion doped crystal in a beaker (6), and an electric and electrically controlled rotating table (7) for placing the beaker (6) containing the bulk rare earth ion doped crystal and driving the beaker (6) to rotate, wherein the optical element group is located on the emission light path of the femtosecond laser (1), and the electric and electrically controlled rotating table (7) is located below the optical element group.

2. The device for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation according to claim 1, characterized in that: The optical element group comprises a first convex lens (2) and a concave lens (3) for reducing the diameter of the femtosecond pulse laser beam, a reflector (4) for reflecting the femtosecond pulse laser beam after the beam reduction, and a second convex lens (5) for focusing the reflected femtosecond pulse laser beam on the surface of a bulk rare earth ion doped crystal in a beaker (6); The first convex lens (2) is located between the femtosecond laser (1) and the concave lens (3), the concave lens (3) is located between the first convex lens (2) and the reflector (4), the second convex lens (5) is located below the reflector (4), and the electric and electrically controlled rotating platform (7) is located below the second convex lens (5).

3. A method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation, characterized in that: The device for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation according to any one of claims 1 to 2 comprises the following steps: Adding a surfactant aqueous solution into a beaker (6), and placing the beaker (6) on an electric and electrically controlled rotating table (7); Placing a bulk rare earth ion-doped crystal at the bottom of a beaker (6) containing an aqueous surfactant solution; A femtosecond laser (1) is used to emit femtosecond pulse laser light, and the femtosecond pulse laser light is used as a laser ablation light source, wherein the beam diameter of the femtosecond pulse laser light is reduced after the femtosecond pulse laser light passes through a first convex lens (2) and a concave lens (3); The femtosecond pulse laser after being condensed is focused on the surface of the bulk rare earth ion doped crystal through a reflector (4) and a second convex lens (5), so that rare earth ion doped nanocrystals can be prepared from the bulk rare earth ion doped crystal; at the same time, during the ablation process, the electric and electrically controlled rotating table (7) drives the beaker (6) and the liquid and crystal inside thereof to rotate through its own rotation.

4. The method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation according to claim 3, characterized in that: The surfactant aqueous solution is 12 ml of dodecyldimethylaminoacetic acid betaine (LDA) aqueous solution, wherein the concentration of the LDA aqueous solution is 0.1 mol / L.

5. The method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation according to claim 3, characterized in that: The femtosecond pulse laser is an ultrashort pulse laser with a wavelength of 515nm and a repetition frequency of 1kHz. The ablation energy density of the femtosecond pulse laser is about 0.29J / cm 2 .

6. The method for preparing rare earth ion-doped nanocrystals by femtosecond laser ablation according to claim 3, characterized in that: During the ablation process, the electric and electrically controlled rotating table (7) drives the beaker (6) and the liquid and crystals therein to rotate at a speed of 30 revolutions per minute.

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