A IV-VI group single element quantum dot material and preparation method thereof

Abstract

The present invention discloses a single-element quantum dot material of IV-VI group and a preparation method thereof, and belongs to the technical field of fluorescent nanomaterials. The preparation method of single-element quantum dot material of IV-VI group is as follows: under the protection of inert gas, N-methylpyrrolidone is used as a dispersion liquid, single-element powder of IV-VI group is added, and a single ultrasound is performed at a power of 800-1000W to obtain suspension A; under ice bath conditions, suspension A is subjected to a secondary ultrasound at a power of 300-500W, and suspension B obtained after the end, suspension B is centrifuged once at a speed of 8000-10000rpm, and the supernatant is retained, and the supernatant is subjected to a secondary centrifugation at a speed of 13000-15000rpm to obtain single-element quantum dots of IV-VI group. The present invention prepares single-element quantum dot materials with high fluorescence quantum efficiency by a simple and convenient method.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent nanomaterials, and more specifically to a group IV-VI single-element quantum dot material and a preparation method thereof. Background Art

[0002] Quantum dots are a type of nanoscale semiconductor. By applying a certain electric field or light pressure to this nano-semiconductor material, they will emit light of a specific frequency. The frequency of the emitted light will change with the size of the semiconductor. Therefore, by adjusting the size of the nano-semiconductor, the color of the light it emits can be controlled. Since this nano-semiconductor has the property of confining electrons and electron holes (Electron holes), this property is similar to that of atoms or molecules in nature, and therefore it is called a quantum dot.

[0003] Quantum dots (QDs), usually with a diameter of 2-10 nanometers, have attracted much attention in areas including photocatalysis, bioimaging, nanomedicine, and solid-state lasers due to their unique structure and properties. In the early stages, QDs were prepared in binary, ternary, alloy, and other semiconductor core or core-shell / multi-shell forms. However, these QDs generally have problems such as low stability and high toxicity. At present, the research work on single-element, low-toxicity quantum dots, namely carbon quantum dots (CQDs), is relatively mature, and a large number of methods for preparing carbon quantum dots have been reported.

[0004] However, there is little research on single-element quantum dots, especially single-element quantum dots of metal elements, with similar performance to carbon quantum dots. At present, quantum dots prepared by ultrasound often have the problem of low fluorescence quantum efficiency. There is no report on the research that can prepare a large number of single-element quantum dots with high fluorescence quantum efficiency by simple and green methods. Summary of the invention

[0005] In view of the above problems, the present invention provides a group IV-VI single-element quantum dot material and a preparation method thereof, and a single-element quantum dot material with high fluorescence quantum efficiency is prepared by a simple and convenient method.

[0006] The first object of the present invention is to provide a method for preparing a single-element quantum dot material of group IV to VI, comprising the following steps:

[0007] Under the protection of inert gas, N-methylpyrrolidone is used as a dispersion liquid, and single element powders of groups IV to VI are added, and ultrasound is performed once at a power of 800-1000 W to obtain a suspension A;

[0008] Under ice bath conditions, suspension A is subjected to a second ultrasonic treatment at a power of 300-500 W. After the ultrasonic treatment, suspension B is obtained. Suspension B is centrifuged once at a speed of 8000-10000 rpm, and the supernatant is retained. The supernatant is centrifuged twice at a speed of 13000-15000 rpm to obtain group IV-VI single-element quantum dots.

[0009] In one embodiment of the present invention, the Group IV-VI single element powder is Si, P, S, Se, Te, Ge, Sn or Pb powder.

[0010] In one embodiment of the present invention, the powder of single element of Group IV to VI is larger than 100 mesh.

[0011] In one embodiment of the present invention, the ratio of the IV-VI group single element powder to N-methylpyrrolidone is 50-100 mg: 50-100 ml.

[0012] In one embodiment of the present invention, an ultrasonic cell pulverizer is used for pulverization, the ultrasonic time is 120-150 minutes, and the working frequency is 1-3kHz; during one ultrasonic operation, the ultrasonic probe works for 1-3 seconds, and rests for 2-4 seconds.

[0013] In one embodiment of the present invention, the ice bath temperature is 0-4°C, and the ultrasound time of the secondary ultrasound is 8-12h.

[0014] In one embodiment of the present invention, the time for one centrifugation is 15-20 min, and the number of centrifugation is 3 times.

[0015] In one embodiment of the present invention, the secondary centrifugation time is 20-30 min, and the number of centrifugation is 3 times.

[0016] The second object of the present invention is to provide the above-mentioned preparation method to prepare IV-VI group single element quantum dot materials.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention provides a type of IV-VI group single-element quantum dot material and a preparation method thereof, which uses low-cost raw materials, is simple and convenient, has high repeatability, and is highly universal.

[0019] (2) The single-element quantum dot material provided by the present invention is similar to C quantum dots, both of which have the characteristic that the fluorescence emission wavelength red-shifts with the excitation wavelength, and have broad application prospects in the field of sensors.

[0020] (3) The single-element quantum dot material provided by the present invention can be doped with different elements according to the electronic configuration of the element, and thus can be used in many applications such as anatase TiO2 photocatalysis or quantum dot doping modification, and has a promising development prospect.

[0021] (4) The single-element quantum dot material prepared by the present invention has a maximum fluorescence efficiency of 21.8%, has good fluorescence properties, and meets the requirements of high-quality luminescent materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A roadmap for preparing single-element quantum dots of groups IV to VI according to the present invention;

[0023] Figure 2 Microscopic morphology of Si (a), P (b), S (c), Se (d), Te (e) single element quantum dots prepared in Examples 1 to 5 of the present invention and a physical image of the single element quantum dots (f);

[0024] Figure 3 The particle size distribution diagram of Si (a), P (b), S (c), Se (d), and Te (e) single element quantum dots prepared in Examples 1 to 5 of the present invention;

[0025] Figure 4 Fluorescence spectra of Si(a), P(b), S(c), Se(d), Te(e), Ge(f), Sn(g), and Pb(h) single element quantum dots prepared in Examples 1 to 8 of the present invention;

[0026] Figure 5 The graph is a relationship between the fluorescence integrated area and the UV-visible absorbance of the single element quantum dots of Si (b), P (c), S (d), Se (e), and Te (f) prepared in Examples 1 to 5 of the present invention;

[0027] Figure 6 1 is a graph showing the relationship between the fluorescence integrated area and the UV-visible absorbance of the Rhodamine B (a) in the present invention and the Si (b) single element quantum dots prepared in Comparative Example 1. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] This application adopts the green and environmentally friendly solution stripping method for preparation, and the preparation route is as follows Figure 1As shown, the specific preparation method is as follows:

[0030] Weigh IV to VI group single element powder, add N-methylpyrrolidone (NMP) solution, use ultrasonic cell crusher to perform ultrasonic treatment once, use ultrasonic cleaning machine to perform ultrasonic treatment twice under ice bath condition after the first ultrasonic treatment, after the second ultrasonic treatment, the obtained suspension is centrifuged once, and the obtained supernatant is centrifuged twice again to obtain IV to VI group single element quantum dots.

[0031] Wherein NMP can be purchased conventionally through commercial channels, and the present invention does not make any special limitation here. The purity of NMP used in the present invention is 99.5%, anhydrous, and is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The quantum dots prepared by the present invention using NMP as a solution will not agglomerate, and the quantum dots obtained by using other solvents such as n-hexane as a solvent for preparation will quickly agglomerate.

[0032] The single element powder of Group IV to VI is Si, P, S, Se, Te, Ge, Sn or Pb powder. The Si, P, S, Se, Te, Ge, Sn or Pb powder can be purchased through conventional commercial channels, and the present invention does not make any special restrictions here.

[0033] The powder content used in the present invention is greater than 99.5%, and is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The size of the IV-VI group single element powder is above 100 mesh. Since the size of the quantum dots themselves in three dimensions is below 100nm, the initial powder selected cannot be too large, otherwise the energy consumption in the preparation process is high and it is difficult to obtain the product.

[0034] The technical parameters of the ultrasonic cell crusher are set as follows:

[0035] Ultrasonic power is 800-1000W;

[0036] Ultrasound time is 120-150min;

[0037] The operating frequency is controlled at 1-3kHz;

[0038] The ultrasound probe works for 1-3 seconds and rests for 2-4 seconds.

[0039] When performing an ultrasonic treatment, nitrogen or argon needs to be used to protect the reaction gas. Comparing the fluorescence quantum efficiency of Si element quantum dots in comparative example 1 and embodiment 1, it can be seen that under the protection of inert gas, after the powder is crushed, the element can be guaranteed not to be oxidized, which is conducive to improving the fluorescence quantum efficiency of quantum dots.

[0040] Preferably, the ratio of the IV-VI group single element powder to N-methylpyrrolidone is 50-100 mg / 50-100 mL.

[0041] The technical parameters of the ultrasonic cleaning machine are set as follows:

[0042] Ultrasonic power is 300-500W;

[0043] Ultrasound time is 8-12h;

[0044] When performing the secondary ultrasonic treatment, it needs to be done under ice bath conditions;

[0045] In some preferred embodiments, the ice bath temperature is in the range of 0-4°C.

[0046] The present invention performs secondary ultrasound under ice bath conditions, with a long ultrasound time (8-12h) and a low temperature (0-4°C). During the ultrasound process, there is sufficient time for the solvation effect to occur (the solvent on the surface of the quantum dots plays a role in stabilizing the performance of the quantum dots), and the low temperature further prevents the quantum dots from agglomerating, which is conducive to the full dispersion of the quantum dots. In addition, this step can ensure that a monodisperse quantum dot suspension is obtained after centrifugation.

[0047] During the first centrifugation, when the supernatant is collected at a speed of 8000-10000 rpm, the centrifugation time is controlled to be 15-20 minutes per time, and the number of centrifugations is 3 times. The supernatant is subjected to a second centrifugation at a speed of 13000-15000 rpm to remove impurities, the centrifugation time is controlled to be 20-30 minutes per time, and the total number of centrifugations is 3 times. After the centrifugation, the supernatant obtained is the IV-VI group single element quantum dots.

[0048] The following is further described in conjunction with specific embodiments.

[0049] In the following specific examples, unless otherwise specified, all raw materials can be sourced from commercial sources.

[0050] Example 1

[0051] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI, wherein the single-element quantum dot of group IV to VI is specifically a silicon quantum dot. Silicon (Si) quantum dots are prepared by a solution stripping method.

[0052] The specific preparation method is as follows:

[0053] Weigh 75 mg of 100-mesh Si powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 135 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0054] Subsequently, the mixture was ultrasonicated in an ice bath at a power of 400 W for additional 10 h to obtain a suspension.

[0055] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the centrifugation time was 20 min per time, and finally the Si quantum dot solution was obtained for standby use.

[0056] The concentration of the prepared Si quantum dot solution was 1.0 mg mL -1 .

[0057] Comparative Example 1

[0058] In the preparation process of this comparative example, the cell crushing step is not performed under the protection of an inert gas atmosphere, and the remaining steps are the same as those of Example 1. The quantum dots in this comparative example are specifically Si quantum dots. The Si quantum dots are prepared by a solution stripping method.

[0059] The specific preparation method is as follows:

[0060] Weigh 75 mg of 100-mesh Si powder and add 75 mL of NMP solution. Use an ultrasonic cell crusher at 900 W for 135 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0061] Subsequently, the mixture was ultrasonicated in an ice bath at a power of 400 W for additional 10 h to obtain a suspension.

[0062] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the centrifugation time was 20 min per time, and finally the Si quantum dot solution was obtained for standby use.

[0063] The concentration of the prepared comparative Si quantum dot solution was 1.0 mg·mL -1 .

[0064] Example 2

[0065] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI. The single-element quantum dots of group IV to VI are specifically phosphorus (P) quantum dots. The P quantum dots are prepared by a solution stripping method.

[0066] The specific preparation method is as follows:

[0067] Weigh 75 mg of 100-mesh P powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 120 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0068] Subsequently, the resulting suspension was additionally sonicated for 10 h in an ice bath at a power of 400 W using an ultrasonic cleaner.

[0069] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the centrifugation time was 20 min per time, and finally the P quantum dot solution was obtained for standby use.

[0070] The concentration of the prepared P quantum dot solution was 1.0 mg mL -1 .

[0071] Example 3

[0072] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI, wherein the single-element quantum dot of group IV to VI is specifically a sulfur (S) quantum dot. The sulfur (S) quantum dot is prepared by a solution stripping method.

[0073] The specific preparation method is as follows:

[0074] Weigh 75 mg of 100-mesh S powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 140 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0075] Subsequently, the resulting suspension was additionally sonicated for 10 h in an ice bath at a power of 400 W using an ultrasonic cleaner.

[0076] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the single centrifugation time was 20 min, and finally the S quantum dot solution was obtained for standby use.

[0077] The concentration of the prepared S quantum dot solution was 1.0 mg mL -1 .

[0078] Example 4

[0079] This embodiment provides a method for preparing a group IV-VI single-element quantum dot material. The group IV-VI single-element quantum dots are specifically selenium (Se) quantum dots, and the Se quantum dots are prepared by a solution stripping method.

[0080] The specific preparation method is as follows:

[0081] Weigh 75 mg of 100-mesh Se powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 150 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0082] Subsequently, the resulting suspension was additionally sonicated for 10 h in an ice bath at a power of 400 W using an ultrasonic cleaner.

[0083] The obtained suspension was centrifuged to collect the clear liquid. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained clear liquid was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the single centrifugation time was 20 min, and finally the Se quantum dot solution was obtained for standby use.

[0084] The concentration of the prepared Se quantum dot solution was 1.0 mg mL -1 .

[0085] Example 5

[0086] This embodiment provides a method for preparing a group IV-VI single-element quantum dot material. The group IV-VI single-element quantum dots are specifically tellurium (Te) quantum dots, and the Te quantum dots are prepared by a solution stripping method.

[0087] The specific preparation method is as follows:

[0088] Weigh 75 mg of 100-mesh Te powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 150 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0089] Subsequently, the resulting suspension was additionally sonicated for 10 h in an ice bath at a power of 400 W using an ultrasonic cleaner.

[0090] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the centrifugation time was 20 min per time, and finally the Te quantum dot solution was obtained for standby use.

[0091] The concentration of the prepared Te quantum dot solution was 1.0 mg mL -1 .

[0092] Example 6

[0093] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI. The single-element quantum dots of group IV to VI are specifically germanium (Ge) quantum dots, and the Ge quantum dots are prepared by a solution stripping method.

[0094] The specific preparation method is as follows:

[0095] Weigh 75 mg of 100-mesh Ge powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 150 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0096] Subsequently, the mixture was ultrasonicated in an ice bath at a power of 400 W for additional 10 h to obtain a suspension.

[0097] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the centrifugation time was 20 min per time, and finally the Ge quantum dot solution was obtained for standby use.

[0098] The concentration of the prepared Ge quantum dot solution was 1.0 mg mL -1 .

[0099] Example 7

[0100] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI. The single-element quantum dots of group IV to VI are specifically tin (Sn) quantum dots. The Sn quantum dots are prepared by a solution stripping method.

[0101] The specific preparation method is as follows:

[0102] Weigh 75 mg of 100-mesh Sn powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 150 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0103] Subsequently, the mixture was ultrasonicated in an ice bath at a power of 400 W for additional 10 h to obtain a suspension.

[0104] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the centrifugation time was 20 min per time, and finally the Sn quantum dot solution was obtained for standby use.

[0105] The concentration of the prepared Sn quantum dot solution was 1.0 mg mL -1 .

[0106] Example 8

[0107] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI. The single-element quantum dots of group IV to VI are specifically lead (Pb) quantum dots, and the Pb quantum dots are prepared by a solution stripping method.

[0108] The specific preparation method is as follows:

[0109] Weigh 75 mg of 100-mesh Pb powder and add 75 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 900 W for 150 min. The operating frequency of the ultrasonic cell crusher is controlled at 2 kHz. The ultrasonic probe works for 2 seconds and rests for 3 seconds.

[0110] Subsequently, the resulting suspension was additionally sonicated for 10 h in an ice bath at a power of 400 W using an ultrasonic cleaner.

[0111] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 9000 rpm, the centrifugation time was controlled to be 15 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 13000 rpm to remove impurities, and the centrifugation time was 20 min per time, and finally the Pb quantum dot solution was obtained for standby use.

[0112] The concentration of the prepared Pb quantum dot solution was 1.0 mg mL -1 .

[0113] Example 9

[0114] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI, wherein the single-element quantum dot of group IV to VI is specifically Si quantum dot. The Si quantum dot is prepared by a solution stripping method.

[0115] The specific preparation method is as follows:

[0116] Weigh 50 mg of 100-mesh Si powder and add 100 mL of NMP solution. Under the protection of argon, use an ultrasonic cell crusher at a power of 800 W for 130 min. The operating frequency of the ultrasonic cell crusher is controlled at 1 kHz. The ultrasonic probe works for 1 second and rests for 2 seconds.

[0117] Subsequently, the mixture was sonicated for additional 12 h in an ice bath at a power of 300 W using an ultrasonic cleaner to obtain a suspension.

[0118] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 8000 rpm, the centrifugation time was controlled to be 20 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 15000 rpm to remove impurities, and the centrifugation time was 30 min per time, and finally the Si quantum dot solution was obtained for standby use.

[0119] The concentration of the prepared Si quantum dot solution was 0.5 mg mL -1 .

[0120] Example 10

[0121] This embodiment provides a method for preparing a single-element quantum dot material of group IV to VI, wherein the single-element quantum dot of group IV to VI is specifically an S quantum dot. The S quantum dot is prepared by a solution stripping method.

[0122] The specific preparation method is as follows:

[0123] Weigh 100 mg of 100-mesh S powder and add 50 mL of NMP solution. Under the protection of N2, use an ultrasonic cell crusher at a power of 1000 W for 120 min. The operating frequency of the ultrasonic cell crusher is controlled at 3 kHz. The ultrasonic probe works for 3 seconds and rests for 4 seconds.

[0124] Subsequently, the resulting suspension was additionally sonicated for 8 h in an ice bath at a power of 500 W using an ultrasonic cleaner.

[0125] The obtained suspension was centrifuged to collect the supernatant. The centrifugation speed was 10000 rpm, the centrifugation time was controlled to be 18 min, and the number of centrifugations was 3 times. The obtained supernatant was centrifuged 3 times at a speed of 14000 rpm to remove impurities, and the single centrifugation time was 25 min, and finally the S quantum dot solution was obtained for standby use.

[0126] The concentration of the prepared S quantum dot solution was 2.0 mg mL -1 .

[0127] Performance Test:

[0128] 1. Microscopic morphology test

[0129] The morphologies of Si, P, S, Se and Te quantum dots prepared in Examples 1 to 5 were observed using a Hitachi, Japan field emission transmission electron microscope.

[0130] All quantum dot solutions were diluted to 0.001 mg mL before testing. -1 , and then immerse the ultra-thin copper mesh supported by the carbon film into the diluted quantum dot solution. After the copper mesh is adsorbed for about 15 minutes, the copper mesh loaded with the sample is taken out and placed on filter paper, and dried naturally at room temperature. After the sample is fully dried, it is placed in a field emission transmission electron microscope with a tube voltage of 120KV for observation. Using Digital Micrograph software, 10 different areas in the TEM photo are selected to measure the size of the quantum dots and calculate their average value, and the size of the Si quantum dot sample is obtained by calculation.

[0131] from Figure 2 It can be seen that the size of all samples is within 2-8nm, and the morphology is elliptical, indicating that Si, P, S, Se and Te quantum dots have been successfully prepared.

[0132] 2. Particle size distribution test

[0133] The particle size of quantum dots was tested using a dynamic particle size analyzer, ZetasizerNano ZS90. Before testing, the concentration of the samples was diluted to 0.01 mg mL -1 .

[0134] Analytical Spectrum ( Figure 3 ) It can be seen that the sizes of Si, P, S, Se and Te quantum dots are between 2.5±0.4nm, 2.9±0.4nm, 3.4±1.3nm, 2.2±0.5nm and 3.4±0.7nm.

[0135] 3. Fluorescence spectrum test

[0136] The fluorescence emission spectrum and temperature-dependent fluorescence emission spectrum of the quantum dot solution were measured using a Varian Cary 50 fluorescence spectrophotometer.

[0137] Depend on Figure 4 It can be seen that when the fluorescence excitation wavelength is changed (330nm-450nm), the fluorescence emission peaks of Si, P, S, Se, Te, Ge, Sn and Pb quantum dots show a red shift phenomenon, and at the same time, their fluorescence intensity decreases with the increase of the excitation wavelength. This shows that the fluorescence emission peaks of Si, P, S, Se, Te, Ge, Sn and Pb quantum dots are dependent on the excitation wavelength.

[0138] During the preparation process, the ice bath ultrasonic time is long and the temperature is low, which causes the quantum dots of different sizes in the original cell fragmentation process to be further solvated, the surface structure is stabilized, and no agglomeration or precipitation occurs, resulting in the characteristic of red shift in the fluorescence spectrum.

[0139] It should be noted that Figure 4 According to the direction of the arrow, the excitation wavelengths are 350nm, 360nm, 370nm, 380nm, 390nm, 400nm, 410nm, 420nm, and 430nm respectively.

[0140] 4. Fluorescence quantum yield test

[0141] The fluorescence quantum efficiency of quantum dots is an important parameter. Formula (1) is used to calculate the fluorescence quantum efficiency of Si, P, S, Se and Te quantum dots.

[0142]

[0143] Among them, n in formula (1) QD ≈n standard , QY standard =0.96, n is the refractive index.

[0144] Rhodamine B was used as a standard substance to establish the relationship between the fluorescence integrated area and the UV-visible absorbance, such as Figure 5 As shown, the fluorescence quantum efficiencies of Si, P, S, Se and Te-dot are 19.9%, 9.8%, 2.8%, 9.3% and 21.8% respectively. Similarly, according to the preparation method of Comparative Example 1, the fluorescence quantum efficiency of Si quantum dots prepared without inert atmosphere protection is 1.4%, which further proves that the protection of inert gas can improve the fluorescence efficiency of quantum dots.

[0145] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiment, in order to avoid redundancy, the present invention describes a preferred embodiment.

[0146] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0147] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing single-element quantum dot materials of groups IV to VI, characterized in that: The following steps are involved: Under the protection of inert gas, N-methylpyrrolidone is used as a dispersion liquid, and a single element powder of group IV to VI is added, and the first ultrasonication is performed at a power of 800-1000W to obtain a suspension A; the single element powder of group IV to VI is Si, P, S, Se, Te, Ge, Sn or Pb powder; the first ultrasonication is performed by using an ultrasonic cell crusher for pulverization, the ultrasonication time is 120-150min, and the working frequency is 1-3kHz; during the first ultrasonication, the ultrasonic probe works for 1-3s, and rests for 2-4s; Under ice bath conditions, the suspension A is subjected to a second ultrasonic treatment at a power of 300-500 W, and a suspension B is obtained after the treatment. The ice bath temperature is 0-4° C., and the ultrasonic treatment time of the second ultrasonic treatment is 8-12 h. The suspension B is centrifuged for the first time at a rotation speed of 8000-10000 rpm, and the supernatant is retained. The supernatant is centrifuged for the second time at a rotation speed of 13000-15000 rpm to obtain group IV-VI single-element quantum dots.

2. The method for preparing a single-element quantum dot material of group IV to VI according to claim 1, characterized in that: The single element powder of Group IV to VI is above 100 mesh.

3. The method for preparing a single-element quantum dot material of group IV to VI according to claim 1, characterized in that: The ratio of IV-VI group single element powder to N-methylpyrrolidone is 50-100 mg:50-100 ml.

4. The method for preparing a single-element quantum dot material of group IV to VI according to claim 1, characterized in that: The first centrifugation time is 15-20 minutes, and the number of centrifugation is 3 times.

5. The method for preparing a single-element quantum dot material of group IV to VI according to claim 1, characterized in that: The second centrifugation time is 20-30 minutes, and the number of centrifugation is 3 times.

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