Method for utilizing bacillus.sp HZ3 to prepare biological NANO lead selenide quantum dots

Abstract

A method for utilizing Bacillus.sp HZ3 to prepare biological nano lead selenide quantum dots. The bred Bacillus.sp HZ3 can convert lead nitrate and sodium selenite so as to produce nano lead selenide PbSe. The preparation method comprises the following steps: (1) preparing a strain culture solution; (2) performing fermentation culture; (3) adding sodium selenite and lead nitrate; (4) adding an inducer; (5) performing induced synthesis of biological nano lead selenide; and (6) performing separation to extract lead selenide quantum dots. On the basis of the characteristics of synthesizing lead selenide by means of Bacillus.sp HZ3, an inducer beneficial to enhancing the synthesis effect of the nano lead selenide is added in the culture process, and a method of combining high-temperature culture, low-temperature induction culture and high-temperature culture is used, thereby improving the synthesis efficiency of the nano lead selenide to the greatest extent.

Description

A method for preparing bionano lead selenide quantum dots using Bacillus sp HZ3 Technical Field

[0001] The invention belongs to the technical field of microbial application, and particularly relates to a method for preparing biological nano-lead selenide quantum dots by utilizing Bacillus sp HZ3. Background Art

[0002] With the growing development of the information society, infrared semiconductor materials have demonstrated extremely important application value in various fields, including production, daily life, and the military. However, traditional infrared semiconductor materials typically have a narrow controllable range in the infrared band, which restricts their application across the entire infrared band. Therefore, the development of semiconductor materials with broad infrared coverage and simple preparation processes has become a research hotspot in the field of infrared semiconductor materials. As a new type of metal compound nanomaterial, lead selenide (PbSe) infrared colloidal semiconductor quantum dots have attracted widespread attention due to their spectral tunability in the infrared band, narrow half-width (FWHM), and solution processing. For example, in the optical communication band of 1300-1550 nm, PbSe quantum dots have the highest fluorescence quantum yield of all infrared semiconductor materials (nearly 90%), making them a highly sought-after material system.

[0003] However, PbSe quantum dots are extremely sensitive to air. When directly exposed to air, they will undergo oxidation and collision-induced dissociation processes in a short period of time, resulting in the weakening or loss of their optical activity, which greatly restricts the application of PbSe quantum dots.

[0004] To effectively passivate PbSe quantum dots and enhance their stability in air, PbSe quantum dots synthesized by traditional physical and chemical methods undergo passivation through methods such as shell coating or halogen ion passivation before use. This not only increases the difficulty and cost of manufacturing PbSe quantum dots, but also increases production costs. Biological methods for synthesizing PbSe quantum dots offer mild reaction conditions, low costs, and environmental friendliness. Furthermore, organisms contain many reducing and stable active components. These components, while synthesizing PbSe quantum dots, can also provide a covering and isolation effect on the prepared PbSe quantum dot particles, reducing interparticle aggregation. This makes the synthesized PbSe quantum dots more stable than lead selenide synthesized by conventional methods, eliminating the need for secondary passivation. Therefore, PbSe quantum dot synthesis has become a research hotspot. Currently, research on the microbial synthesis of PbSe quantum dots is limited, with reports limited to a few fungi, such as Trichoderma sp. and Aspergillus terreus. Moreover, these microorganisms synthesize PbSe quantum dots at a slow rate, requiring more than 5 days of culture to convert sodium selenite and lead nitrate into PbSe quantum dots, which greatly limits the large-scale rapid preparation and application of PbSe quantum dots.

[0005] Publication number CN103626139A, a Chinese patent, discloses a method for synthesizing lead selenide quantum dots by inducing local supersaturation using a nanosecond pulse laser. The method first uses lead acetate trihydrate and sulfur powder to prepare lead selenide nanocrystals in oleic acid. Then, using lead selenide raw materials, a 4ml PbSe(OA) solution is prepared at a concentration of 2.5mM. Nanosecond parallel laser light is used to act until clarified, with an ice bath as an aid. The laser parameters are 700V, 5Hz, and the reaction is carried out at room temperature and normal atmospheric pressure. 5ml of ethanol is then added to the resulting product solution, which is then centrifuged and circulated for cleaning. The resulting final product is then dispersed in cyclohexane to produce well-dispersed lead selenide quantum dots. The lead selenide quantum dots prepared by this method have good crystallinity and a relatively fast synthesis rate. However, this method still suffers from the problems of complex operating steps and low efficiency. Furthermore, the preparation method uses oleic acid and ammonium oleate, which are irritating to the human respiratory tract, posing health risks and environmental pollution risks.

[0006] Summary of the Invention

[0007] The technical problem to be solved by the present invention is to avoid the problems of complex operation, high production cost, low efficiency, potential health risks and environmental pollution risks in the preparation of PbSe quantum dots by traditional physical and chemical methods.

[0008] The present invention solves the above technical problems through the following technical means:

[0009] Strain description: The Bacillus.sp HZ3 used in the present invention, deposit number: CCTCC M 20221472, deposit date: September 21, 2022, deposit unit: China Center for Type Culture Collection (CCTCC), deposit address: Luojia Mountain, Bayi Road, Wuchang District, Wuhan City, Hubei Province.

[0010] The present invention provides a method for preparing bionano lead selenide quantum dots using Bacillus sp HZ3, comprising the following steps:

[0011] (1) Preparation of bacterial culture fluid: a single colony of Bacillus sp HZ3 was selected and added to YNP medium to obtain bacterial culture fluid;

[0012] (2) Fermentation culture: The culture fluid obtained in step (1) was added to the fermentation medium and cultured until the number of Bacillus.sp HZ3 bacteria in the culture fluid reached 10 7 CFU / mL;

[0013] (3) Adding sodium selenite (Na2SeO3) and lead nitrate (Pb(NO3)2): Add sodium selenite solution to the culture medium obtained in step (2) and then add lead nitrate solution and continue culturing;

[0014] (4) Adding an inducer: adding an inducer to the culture solution obtained in step (3);

[0015] (5) Induced synthesis of biological nano-lead selenide: After adding the inducer, the culture is first cultured at room temperature, then transferred to low temperature culture, and then transferred to room temperature culture again. The culture is cultured until the color of the culture medium changes from light yellow to gray-brown and the color no longer darkens, indicating that the nano-lead selenide quantum dots are completely generated;

[0016] (6) Separating and extracting lead selenide quantum dots: The culture solution obtained in step (5) is placed in a centrifuge tube, subjected to a preliminary centrifugation operation, the bacterial precipitate is discarded, and the supernatant is collected; the supernatant is then placed in a clean centrifuge tube, subjected to a secondary centrifugation operation, and the obtained precipitate is resuspended in double-distilled water to obtain the prepared nano-lead selenide quantum dots.

[0017] Beneficial effects: The present invention adopts a special strain of Bacillus sp HZ3 to synthesize nanomaterials by biological method, with mild reaction conditions, low cost, simple operation, and improved efficiency in preparing nano-lead selenide quantum dots.

[0018] Preferably, the YNP medium in step (1) is prepared from 5-10 g of peptone, 3-5 g of beef powder, 5-10 g of yeast powder, 1-3 mg of vitamin B2, 0.1-0.3 g of sodium nitrate, and 1000 mL of pure water.

[0019] Preferably, in step (2), the bacterial culture solution obtained in step (1) is added to the fermentation medium at a ratio of 1-3% (v / v).

[0020] Preferably, the fermentation medium in step (2) is prepared from 3-5 g of peptone, 3-5 g of beef powder, 3-5 g of yeast powder, 1-3 g of glucose, 1-2 g of ammonium nitrate, 0.01-0.04 g of calcium chloride, 1-3 mg of vitamin B2, and 1000 mL of pure water.

[0021] Preferably, the inducer in step (3) is one or more of sodium sulfite, CTAB, and thioredoxin.

[0022] Preferably, the concentration of the inducer in step (3) is 1-15 mg / L.

[0023] Preferably, in step (4), the concentration of the sodium selenite solution is 1 mol / L, the concentration of the lead nitrate solution is 100 mol / L, the volume ratio of the sodium selenite solution to the culture medium is (1-5):1000; the volume ratio of the lead nitrate solution to the culture medium is (1-5):100.

[0024] Preferably, in step (5), normal temperature refers to 28-37°C, and low temperature refers to 15-20°C.

[0025] Preferably, in step (5), the culture is first cultured at 28-37°C and 150-200 rpm for 8-14 h, then transferred to low-temperature culture, and cultured at 15-20°C and 150-200 rpm for another 8-14 h, and then transferred to 28-37°C and 150-200 rpm for shaking culture.

[0026] Preferably, the speed of the preliminary centrifugation in step (6) is 6000-10000 r / min, and the time is 3-8 min.

[0027] Preferably, the rotation speed of the secondary centrifugation in step (6) is 20,000-30,000 r / min, and the time is 10-20 min.

[0028] Preferably, the culture conditions in step (1), step (2) and step (3) are all 28-37° C. and 150-200 rpm shaking culture.

[0029] Preferably, the culturing time in step (1) is 12-14 hours; the culturing time in step (2) is 6-8 hours; and the culturing time in step (3) is 1-2 hours.

[0030] Experimental results: The resulting lead selenide quantum dot (PbSe) particles were measured using a nano-laser particle size analyzer, with particle sizes ranging from 10 to 40 nm. Scanning electron microscopy coupled with an energy dispersive spectroscopy (SEM-EDX) revealed nanoparticles with sizes ranging from 10 to 30 nm. The EDX spectrum displayed characteristic peaks for Pb and Se, confirming that the prepared nanoparticles were lead selenide quantum dot (PbSe) particles.

[0031] The advantages of the present invention are:

[0032] (1) The present invention adopts a special strain of Bacillus sp HZ3 to synthesize nanomaterials by biological method, which has mild reaction conditions, low cost, simple operation, and improves the efficiency of preparing nano-lead selenide quantum dots.

[0033] (2) The lead selenide quantum dot (PbSe) synthesis strain Bacillus spHZ3 used in the present invention has very strong tolerance and reducing ability to heavy metals (Cu, Pb, Ag, etc.) and selenium (Se). This strain can tolerate 10mM lead nitrate (Pb(NO3)2) and 10mM sodium selenite, and can continuously synthesize lead selenide quantum dots (PbSe) during its growth, thereby greatly reducing the production cost of lead selenide quantum dots (PbSe).

[0034] (3) The present invention is based on the characteristics of Bacillus.spHZ3 in synthesizing lead selenide quantum dots (PbSe). A special inducer is added during the synthesis process, and a method combining high-temperature culture-low-temperature culture-high-temperature culture is adopted, thereby further improving the synthesis efficiency of lead selenide quantum dots (PbSe). Bacillus.spHZ3 can convert 4mM lead nitrate and 4mM sodium selenite into lead selenide quantum dots (PbSe) within 48 hours, greatly improving the synthesis efficiency of nano-lead selenide. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a comparative diagram of the growth of Bacillus spHZ3 in a culture medium containing sodium selenite or lead nitrate;

[0036] FIG2 is a transmission electron microscopy observation and particle size analysis diagram of lead selenide quantum dots synthesized by Bacillus spHZ3 in Example 2 of the present invention;

[0037] FIG3 is an EDX analysis chart of the elemental composition of lead selenide quantum dots synthesized by Bacillus spHZ3 in Example 2 of the present invention;

[0038] FIG4 is an X-ray diffraction pattern of lead selenide quantum dots synthesized by Bacillus spHZ3 in different embodiments;

[0039] FIG5 is a fluorescence spectrum analysis diagram of lead selenide quantum dots synthesized by Bacillus spHZ3 in different embodiments;

[0040] FIG6 is a graph showing the effect of adding inducers on the synthesis of lead selenide quantum dots by Bacillus spHZ3. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0043] Example 1:

[0044] A method for preparing bionano lead selenide quantum dots using Bacillus sp HZ3 comprises the following steps:

[0045] (1) Preparation of bacterial culture medium: A single colony of Bacillus sp HZ3 was picked and added to YNP medium. The culture was shaken at 28°C and 150 rpm for 14 h to obtain bacterial culture medium. YNP medium was prepared from 5 g of peptone, 3 g of beef powder, 5 g of yeast powder, 1 mg of vitamin B2, 0.1 g of sodium nitrate, and 1000 mL of purified water.

[0046] (2) Fermentation culture: The culture solution obtained in step (1) was added to the fermentation medium at 1% (v / v), and cultured at 28°C and 150 rpm for 8 h until the number of Bacillus.sp HZ3 bacteria in the culture solution reached 10 7 CFU / mL; fermentation medium was prepared by peptone 5g, beef powder 5g, yeast powder 5g, glucose 3g, ammonium nitrate 2g, calcium chloride 0.04g, vitamin B2 3mg, and purified water 1000mL;

[0047] (3) Adding sodium selenite (Na2SeO3) and lead nitrate (Pb(NO3)2): Add 0.1 mL of 1 mol / L sodium selenite solution to the culture medium obtained in step (2), shake culture at 28°C and 150 rpm for 2 h, then add 1 mL of 100 mol / L lead nitrate solution, and continue shaking culture at 28°C and 150 rpm;

[0048] (4) Adding an inducer: Add an inducer (sodium sulfite) to the culture solution obtained in step (3) to a final concentration of 1 mg / L.

[0049] (5) Induced synthesis of biological nano-lead selenide: After adding the inducer, first adopt 28 ° C, 150 rpm shaking culture for 14 hours, then transfer to low temperature culture, 15 ° C, 150 rpm shaking culture for another 14 hours, then transfer to 28 ° C, 150 rpm shaking culture again, and culture until the color of the culture medium changes from light yellow to gray-brown and the color no longer darkens, indicating that the nano-lead selenide quantum dots are completely generated;

[0050] (6) Separation and extraction of lead selenide quantum dots: The culture solution obtained in step (5) was placed in a centrifuge tube and subjected to a preliminary centrifugation at 6000 r / min for 8 min. The bacterial precipitate was discarded and the supernatant was collected. The supernatant was then placed in a clean centrifuge tube and subjected to a secondary centrifugation at 20000 r / min for 20 min. The obtained precipitate was resuspended in double-distilled water to obtain the prepared nano-lead selenide quantum dots.

[0051] Experimental Results: ICP-AES analysis revealed that 47.5% of the added Pb(NO3)2 and Na2SeO3 were converted into lead selenide quantum dots (PbSe). The resulting PbSe nanoparticles, measured using a nano-laser particle size analyzer, had a particle size range of 10-40 nm. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDX) revealed nanoparticles with a size of 10-30 nm. The EDX spectrum displayed characteristic peaks for Pb and Se, confirming that the prepared nanoparticles were lead selenide quantum dots.

[0052] Example 2:

[0053] A method for preparing bionano lead selenide quantum dots using Bacillus sp HZ3 comprises the following steps:

[0054] (1) Preparation of bacterial culture medium: A single colony of Bacillus sp HZ3 was picked and added to YNP medium. The culture was shaken at 32°C and 180 rpm for 13 h to obtain bacterial culture medium. YNP medium was prepared from 8 g of peptone, 4 g of beef powder, 8 g of yeast powder, 2 mg of vitamin B2, 0.2 g of sodium nitrate, and 1000 mL of purified water.

[0055] (2) Fermentation culture: The culture solution obtained in step (1) was added to the fermentation medium at 2% (v / v), and cultured at 32°C and 180 rpm for 7 h until the number of Bacillus.sp HZ3 bacteria in the culture medium reached 10 7CFU / mL; fermentation medium was prepared by peptone 4g, beef powder 4g, yeast powder 4g, glucose 2g, ammonium nitrate 1.5g, calcium chloride 0.03g, vitamin B2 2mg, and purified water 1000mL;

[0056] (3) Adding sodium selenite (Na2SeO3) and lead nitrate (Pb(NO3)2): Add 0.3 mL of 1 mol / L sodium selenite solution to the culture medium obtained in step (2), shake culture at 32°C and 180 rpm for 1.5 h, then add 3 mL of 100 mol / L lead nitrate solution, and continue shaking culture at 32°C and 180 rpm;

[0057] (4) Adding inducer: Add inducer (sodium sulfite, CTAB, thioredoxin, mass ratio 1:2:2) to the culture solution obtained in step (3) to make the final concentration of the inducer 10 mg / L;

[0058] (5) Induced synthesis of biological nano-lead selenide: After adding the inducer, first adopt 32 ° C, 180 rpm shaking culture for 12 hours, then transfer to low temperature culture, 18 ° C, 180 rpm shaking culture for another 12 hours, then transfer to 32 ° C, 180 rpm shaking culture, and culture until the color of the culture medium changes from light yellow to gray-brown and the color no longer darkens, indicating that the nano-lead selenide quantum dots are completely generated;

[0059] (6) Separation and extraction of lead selenide quantum dots: The culture solution obtained in step (5) was placed in a centrifuge tube and subjected to a preliminary centrifugation at 8000 r / min for 5 min. The bacterial precipitate was discarded and the supernatant was collected. The supernatant was then placed in a clean centrifuge tube and subjected to a secondary centrifugation at 25000 r / min for 15 min. The obtained precipitate was resuspended in double-distilled water to obtain the prepared nano-lead selenide quantum dots.

[0060] Experimental Results: ICP-AES analysis showed that the added Pb(NO₃)₂ and sodium selenite Na₂SeO₃ were completely (100%) converted into lead selenide quantum dots (PbSe). The resulting lead selenide nanoparticles, measured using a nano-laser particle size analyzer, had a particle size range of 10-40 nm. Scanning electron microscopy coupled with an energy dispersive spectroscopy (SEM-EDX) observed nanoparticles with a particle size of 10-30 nm. The EDX spectrum displayed characteristic peaks for Pb and Se, confirming that the prepared nanoparticles were lead selenide nanoparticles.

[0061] Example 3:

[0062] A method for preparing bionano lead selenide quantum dots using Bacillus sp HZ3 comprises the following steps:

[0063] (1) Preparation of bacterial culture medium: A single colony of Bacillus sp HZ3 was picked and added to YNP medium. The culture was shaken at 37°C and 200 rpm for 12 h to obtain bacterial culture medium. YNP medium was prepared from 10 g of peptone, 5 g of beef powder, 10 g of yeast powder, 3 mg of vitamin B2, 0.3 g of sodium nitrate, and 1000 mL of purified water.

[0064] (2) Fermentation culture: The culture solution obtained in step (1) was added to the fermentation medium at a rate of 3% (v / v), and cultured at 37°C and 200 rpm for 6 h until the number of Bacillus.sp HZ3 bacteria in the culture medium reached 10 7 CFU / mL; fermentation medium was prepared by peptone 3g, beef powder 3g, yeast powder 3g, glucose 1g, ammonium nitrate 1g, calcium chloride 0.01g, vitamin B2 1mg, and pure water 1000mL;

[0065] (3) Adding sodium selenite (Na2SeO3) and lead nitrate (Pb(NO3)2): Add 0.5 mL of 1 mol / L sodium selenite solution to the culture medium obtained in step (2), shake culture at 37°C and 200 rpm for 1 h, then add 5 mL of 100 mol / L lead nitrate solution, and continue shaking culture at 37°C and 200 rpm;

[0066] (4) Adding inducer: Add inducer (sodium sulfite and CTAB, mass ratio 1:2) to the culture solution obtained in step (3) to make the final concentration of the inducer 15 mg / L;

[0067] (5) Induced synthesis of biological nano-lead selenide: After adding the inducer, the culture was first cultured at 37°C and 200 rpm for 8 h, then transferred to low-temperature culture and cultured at 20°C and 200 rpm for another 8 h, then transferred to 37°C and 200 rpm for culture again, and cultured until the color of the culture medium changed from light yellow to gray-brown and did not darken any more, indicating that the nano-lead selenide quantum dots were completely generated;

[0068] (6) Separation and extraction of lead selenide quantum dots: The culture solution obtained in step (5) was placed in a centrifuge tube and subjected to a preliminary centrifugation at 10,000 r / min for 3 min, the bacterial precipitate was discarded, and the supernatant was collected; the supernatant was then placed in a clean centrifuge tube and subjected to a secondary centrifugation at 30,000 r / min for 10 min. The obtained precipitate was resuspended in double-distilled water to obtain the prepared nano-lead selenide quantum dots.

[0069] Experimental Results: ICP-AES analysis revealed that 76.5% of the added Pb(NO₃)₂ and Na₂SeO₃ was converted into lead selenide (PbSe). The resulting lead selenide nanoparticles, measured using a nano-laser particle size analyzer, had a particle size range of 10-40 nm. Scanning electron microscopy coupled with an energy dispersive spectroscopy (SEM-EDX) revealed nanoparticles with a size of 10-30 nm. The EDX spectrum displayed characteristic peaks for Pb and Se, confirming that the prepared nanoparticles were lead selenide nanoparticles.

[0070] Figure 1 is a comparative graph showing the growth of Bacillus spHZ3 in a culture medium containing sodium selenite or lead nitrate. As can be seen from the figure, when sodium selenite and lead nitrate are added simultaneously, the culture medium turns brown, indicating the formation of lead selenide quantum dots.

[0071] FIG2 is a transmission electron microscopy observation and particle size analysis of lead selenide quantum dots synthesized by Bacillus spHZ3 in Example 2 of the present invention. As can be seen from the figure, the particle size distribution of the synthesized lead selenide quantum dots is between 15-30 nm;

[0072] FIG3 is an EDX analysis chart of the elemental composition of lead selenide quantum dots synthesized by Bacillus spHZ3 in Example 2 of the present invention;

[0073] FIG4 is an X-ray diffraction pattern of lead selenide quantum dots synthesized by Bacillus spHZ3 in different embodiments;

[0074] FIG5 is a fluorescence spectrum analysis diagram of lead selenide quantum dots synthesized by Bacillus spHZ3 in different embodiments;

[0075] Figure 6 shows the effect of adding inducers on the synthesis of lead selenide quantum dots by Bacillus spHZ3 (A: no inducer added, B: Example 2 (addition of sodium sulfite, CTAB and thioredoxin), C: Example 3 (addition of sodium sulfite and CTAB). It can be seen from the figure that different inducers have different effects on the synthesis efficiency of lead selenide quantum dots.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3, comprising the following steps: (1) Preparing bacterial culture fluid: picking a single colony of Bacillus.sp HZ3 and adding it to YNP medium for cultivation to obtain bacterial culture fluid; (2) Fermentation culture: The culture fluid obtained in step (1) was added to the fermentation medium and cultured until the number of Bacillus.sp HZ3 colonies in the culture fluid reached 10 7 CFU / mL; (3) adding sodium selenite and lead nitrate: adding sodium selenite solution to the culture solution obtained in step (2), culturing, and then adding lead nitrate solution, and continuing culturing; (4) adding an inducer: adding an inducer to the culture solution obtained in step (3); (5) Inducing the synthesis of biological nano-lead selenide: After adding the inducer, first culture at room temperature, then transfer to low temperature culture, and then transfer to room temperature culture again, and culture until the color of the culture medium changes from light yellow to gray brown and the color no longer darkens, the nano-lead selenide quantum dots are completely generated; (6) Separating and extracting lead selenide quantum dots: The culture solution obtained in step (5) is placed in a centrifuge tube, subjected to a preliminary centrifugation operation, the bacterial precipitate is discarded, and the supernatant is collected; the supernatant is then placed in a clean centrifuge tube, subjected to a secondary centrifugation operation, and the obtained precipitate is resuspended in double distilled water to obtain the prepared nano-lead selenide quantum dots.

2. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 1, characterized in that: The YNP medium in step (1) is prepared from 5-10 g of peptone, 3-5 g of beef powder, 5-10 g of yeast powder, 1-3 mg of vitamin B2, 0.1-0.3 g of sodium nitrate, and 1000 mL of pure water.

3. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 1 or 2, characterized in that: In the step (2), the bacterial culture solution obtained in the step (1) is added to the fermentation medium at 1-3% (v / v).

4. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 3, characterized in that: In the step (2), the fermentation medium is prepared from 3-5 g of peptone, 3-5 g of beef powder, 3-5 g of yeast powder, 1-3 g of glucose, 1-2 g of ammonium nitrate, 0.01-0.04 g of calcium chloride, 1-3 mg of vitamin B2, and 1000 mL of pure water.

5. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 4, characterized in that: In step (3), the inducer is one or more of sodium sulfite, CTAB, and thioredoxin; the concentration of the inducer is 1-15 mg / L.

6. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 1, characterized in that: In the step (4), the concentration of the sodium selenite solution is 1 mol / L, the concentration of the lead nitrate solution is 100 mol / L, the volume ratio of the sodium selenite solution to the culture medium is (1-5):1000; the volume ratio of the lead nitrate solution to the culture medium is (1-5):

100.

7. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 1, characterized in that: In the step (5), normal temperature refers to 28-37°C, and low temperature refers to 15-20°C.

8. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 1, characterized in that: In the step (6), the speed of the initial centrifugation is 6000-10000 r / min, and the time is 3-8 min; the speed of the secondary centrifugation is 20000-30000 r / min, and the time is 10-20 min.

9. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 1, characterized in that: The culture conditions in step (1), step (2) and step (3) are all 28-37° C. and 150-200 rpm shaking culture.

10. The method for preparing bio-nano lead selenide quantum dots using Bacillus sp HZ3 according to claim 1, characterized in that: The culturing time in step (1) is 12-14 hours; the culturing time in step (2) is 6-8 hours; and the culturing time in step (3) is 1-2 hours.

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