Preparation Method and Application of an Au-TiO2-SiO2 Composite Nanomaterial

Abstract

The present invention relates to a preparation method and application of an Au-TiO2-SiO2 composite nanomaterial, belonging to the technical field of composite nanomaterials. In the present invention, gold nanoparticles are first combined with titanium dioxide by means of gold loading to form gold-titanium dioxide nanocrystals, and then silicon dioxide is coated on the surface of the gold-titanium dioxide nanocrystals, enhancing the local surface plasmon resonance of the Au-TiO2-SiO2 composite nanomaterial; and by improving the acidity and alkalinity, active sites, electron density, etc. of the composite material surface, the photocatalytic activity of the Au-TiO2-SiO2 composite nanomaterial is improved, and the utilization range of titanium dioxide for visible light is expanded; the Au-TiO2-SiO2 composite nanomaterial prepared by the present invention has controllable morphology and size, good stability, mild preparation conditions, safe raw materials, and no harmful pollutants are generated during the preparation process, and it can play an important role in the fields of sewage treatment, environmental protection, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of composite nanomaterials, and particularly to a preparation method and application of an Au-TiO2-SiO2 composite nanomaterial. Background Art

[0002] In recent years, with the continuous improvement of people's living standards and the acceleration of the industrialization process, the problem of environmental pollution has become increasingly serious; among them, the pollution of water resources has received extensive attention, especially organic pollutants in water. Currently, there are various treatment methods for organic pollutants in water, but most of the treatment methods have problems such as low efficiency, low recovery rate, and secondary environmental pollution. Photocatalysis has been vigorously developed and widely explored due to its high efficiency, long lifespan, economic greenness, and simple maintenance. Among them, titanium dioxide (TiO2) has broad application prospects in the fields of photocatalytic degradation of organic pollutants and photocatalytic water splitting for hydrogen production due to its high photocatalytic activity, simple photocatalytic technology process, low cost, stable chemical properties, non-toxicity, and good biocompatibility. Currently, anatase TiO2 with a band gap of 3.2 eV is considered the most effective photocatalyst.

[0003] However, the degradation activity of TiO2 is affected by various factors; for example, its band gap and electron-hole pair recombination are both affected by the particle size of TiO2; in addition, the rapid charge recombination and absorption in the ultraviolet range limit the photocatalytic efficiency of TiO2 under visible light irradiation; in order to overcome the limitations of TiO2, many studies have been carried out to improve its visible light photocatalytic activity. One strategy to improve the photocatalytic efficiency of TiO2 is to load noble metals on its surface. Many reports show that loading noble metals can significantly enhance the photocatalytic activity of TiO2, but since the pores in noble metal nanoparticles (NPs) do not have strong oxidation ability, only slight or partial oxidation reactions can occur. In view of the problems existing in the above metal photocatalysts, a comprehensive study on the modification of non-metallic elements has been carried out in order to obtain titanium dioxide with stable visible light activity. It has been reported that covering noble metals with dielectric materials such as silica (SiO2) can further enhance the local surface plasmon resonance (LSPR) of noble metal NPs. In addition, compared with bare noble metal NPs, when SiO2-covered noble metals are loaded on the surface of TiO2, due to the presence of a dielectric layer in the noble metal, the electrons generated in TiO2 cannot be captured by the noble metal, and the electrons excited in the noble metal cannot be transferred to TiO2 either. It can be seen that in the system of loading SiO2-covered noble metals on TiO2, the enhancement of the local electric field is the main factor accelerating the photocatalytic reaction.

[0004] In summary, most of the current research in this field only modifies TiO2 nanomaterials in one aspect, such as noble metal loading or non-metal loading, lacking research on a more comprehensive modification method. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art and provide a preparation method and application of an Au-TiO2-SiO2 composite nanomaterial that can improve the photocatalytic activity of TiO2. The Au-TiO2-SiO2 composite nanomaterial prepared by the present invention has the advantages of controllable size, good stability, and large specific surface area.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a preparation method of an Au-TiO2-SiO2 composite nanomaterial, comprising the following steps:

[0007] S1. Uniformly mix an aqueous solution of cetyltrimethylammonium bromide (CTAB) of gold nanoparticles (AuNP S ) with ethanol (EtOH) and ammonia water (NH4OH), and let the mixture stand.

[0008] S2. Add the TiO2 dispersion to the mixture obtained in step S1 under vigorous stirring and mix well to obtain Au-TiO2 nanocrystals.

[0009] S3. Add tetraethyl orthosilicate (TEOS) to the mixed solution obtained in step S2 and continue stirring to obtain the Au-TiO2-SiO2 composite nanomaterial.

[0010] The present invention uses a three-step method to prepare the Au-TiO2-SiO2 composite nanomaterial. First, the AuNP S is combined with TiO2 by Au loading to form a nanoatomic cluster. Utilizing the difference in Fermi levels between the two, the electrons and holes generated by light irradiation are effectively separated, promoting the separation and transfer of photogenerated carriers. The AuNP S absorbs photons corresponding to the wavelength of its plasma absorption band, generating strong LSPR, stimulating the bandgap excitation of TiO2 particles near the AuNP S , and more electron-hole pairs can be generated in the TiO2 in the formed Au-TiO2 nanocrystals. Then, TEOS is used to provide SiO2 to cover the Au-TiO2 nanocrystals, further enhancing the LSPR of the composite material, and improving the photocatalytic activity of the Au-TiO2-SiO2 composite nanomaterial by improving the surface acidity and alkalinity, active sites, electron density, etc. of the composite material. At the same time, the excitation energy of TiO2 can be reduced by reducing the bandgap energy or creating intermediate energy levels between the valence band and the conduction band, overcoming the limitation of the fast charge recombination and absorption in the ultraviolet range on the photocatalytic efficiency of TiO2 under visible light irradiation, and expanding the utilization range of the Au-TiO2-SiO2 nanocomposite material for visible light.

[0011] Preferably, in step S1, the AuNP SThe volume ratio of the CTAB suspension, EtOH, and NH4OH for AuNP S is CTAB suspension:EtOH:NH4OH = 3:1:0.02.

[0012] Preferably, in the step S1, the time for standing the mixture is 5 - 8 min.

[0013] Preferably, in the step S1, for AuNP S the preparation method of the CTAB suspension is: Mix chloroauric acid (HAuCl4) and the CTAB solution and stir for 5 - 8 min, then add sodium borohydride (NaBH4) to the mixed solution and continue stirring for 13 - 17 min until the solution turns dark red, then place it at 4 - 8 °C for 10 - 12 h, and finally add NH4OH to adjust the pH of the mixed solution to 9 - 10, thus obtaining the CTAB suspension of AuNP S CTAB suspension.

[0014] More preferably, in the step S1, for AuNP S the concentration of the CTAB suspension is 49.2 μg / mL. The inventor found through experiments that when the CTAB suspension of AuNP S adopts the above concentration, the photocatalytic activity of the final Au - TiO2 - SiO2 composite nanomaterial is the best.

[0015] Most preferably, when the concentration of the CTAB suspension of AuNP S is 49.2 μg / mL, the molar concentration ratio of HAuCl4 to NaBH4 is HAuCl4:NaBH4 = 1:0.0025.

[0016] It should be noted that in the step S2, the TiO2 dispersion is added to the mixture in step S1 in a slow - dropping manner. After the dropping is completed, continue to stir vigorously for 30 - 35 min. The above operation can make the composite of AuNP S and TiO2 more sufficient.

[0017] Preferably, in the step S2, the volume ratio of the mixture in step S1 to the TiO2 dispersion is mixture in step S1:TiO2 dispersion = 4:1. The inventor found through experiments that at this volume ratio, the composite of AuNP S and TiO2 can be more sufficient.

[0018] More preferably, in the step S2, the TiO2 dispersion is an aqueous TiO2 solution with a concentration of 5 mg / mL.

[0019] Most preferably, in the step S2, the preparation method of the TiO2 dispersion is as follows: After mixing titanium isopropoxide (TTIP) and isopropanol (IPA) evenly, pour them into a nitric acid aqueous solution with a pH of 4.8 - 5 and stir for 30 - 35 min until fully mixed. Then place the mixed solution at a temperature of 60 - 65 °C and dry for 10 - 12 h, and then wash it to obtain the TiO2 dispersion.

[0020] Most most preferably, in the step S2, the volume ratio of TTIP, IPA and H2O is TTIP:PIA:H2O = 1:3:50.

[0021] It should be noted that when drying the TiO2 dispersion, there is no need to seal it to prevent gas release caused by temperature rise.

[0022] Preferably, in the step S3, the volume ratio of TEOS to the TiO2 dispersion in the step S2 is TEOS:TiO2 dispersion = 0.03:1.

[0023] Preferably, in the step S3, the continuous stirring time after adding TEOS is 23 - 25 h.

[0024] More preferably, in the step S3, after continuously stirring with the addition of TEOS, the remaining CTAB solution in the solution needs to be removed.

[0025] Most preferably, in the step S3, the step of removing the remaining CTAB solution in the solution is as follows: After adding 10 mL of ammonium nitrate (NH4NO3) buffer solution, centrifuge and take out the supernatant. Repeat adding 10 mL of NH4NO3 buffer solution to the remaining solution 2 - 3 times and take out the supernatant. Finally, add the remaining solution to anhydrous EtOH and dissolve it by ultrasonic treatment to remove the CTAB solution.

[0026] As a preferred embodiment of the preparation method of the Au-TiO2-SiO2 composite nanomaterial of the present invention, the ammonium nitrate buffer solution is an EtOH solution of NH4NO3.

[0027] As a more preferred embodiment of the preparation method of the Au-TiO2-SiO2 composite nanomaterial of the present invention, the concentration of NH4NO3 in the ammonium nitrate buffer solution is 20 g / L.

[0028] As a preferred embodiment of the preparation method of the Au-TiO2-SiO2 composite nanomaterial of the present invention, the centrifugation parameters in the step of removing the remaining CTAB solution in the solution are: relative centrifugal force (RCF) is 18000 - 20000, the centrifugation time is 10 - 12 min, and the centrifugation temperature is 10 - 12 °C.

[0029] The present invention also provides an application of the above Au-TiO2-SiO2 composite nanomaterial in sewage treatment.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a preparation method and an application of an Au-TiO2-SiO2 composite nanomaterial. First, AuNP is combined with TiO2 by Au loading to form a nanoatomic cluster, so that more electron-hole pairs can be generated in the formed Au-TiO2 nanocrystal; then TEOS is used to provide SiO2 to cover the Au-TiO2 nanocrystal, further enhancing the LSPR of the composite material, and improving the photocatalytic activity of the Au-TiO2-SiO2 composite nanomaterial by improving the surface acidity and alkalinity, active sites, electron density, etc. of the composite material; at the same time, the excitation energy of TiO2 can be reduced by reducing the band gap energy or creating intermediate energy levels between the valence band and the conduction band, overcoming the limitation of the fast charge recombination and absorption in the ultraviolet range on the photocatalytic efficiency of TiO2 under visible light irradiation, and expanding the utilization range of the Au-TiO2-SiO2 nanocomposite material for visible light; the preparation conditions of the composite material of the present invention are mild, the raw materials are relatively safe, and no harmful pollutants are generated during the preparation process, which can play an important role in the fields of sewage treatment, environmental protection, etc. S Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a preparation method and an application of an Au-TiO2-SiO2 composite nanomaterial. First, AuNP is combined with TiO2 by Au loading to form a nanoatomic cluster, so that more electron-hole pairs can be generated in the formed Au-TiO2 nanocrystal; then TEOS is used to provide SiO2 to cover the Au-TiO2 nanocrystal, further enhancing the LSPR of the composite material, and improving the photocatalytic activity of the Au-TiO2-SiO2 composite nanomaterial by improving the surface acidity and alkalinity, active sites, electron density, etc. of the composite material; at the same time, the excitation energy of TiO2 can be reduced by reducing the band gap energy or creating intermediate energy levels between the valence band and the conduction band, overcoming the limitation of the fast charge recombination and absorption in the ultraviolet range on the photocatalytic efficiency of TiO2 under visible light irradiation, and expanding the utilization range of the Au-TiO2-SiO2 nanocomposite material for visible light; the preparation conditions of the composite material of the present invention are mild, the raw materials are relatively safe, and no harmful pollutants are generated during the preparation process, which can play an important role in the fields of sewage treatment, environmental protection, etc. Description of the Drawings

[0031] Figure 1 It is the ultraviolet-visible spectrum diagram of the TiO2 dispersion liquid in Example 1 of the present invention;

[0032] Figure 2 It is the particle size distribution diagram of the TiO2 dispersion liquid in Example 1 of the present invention;

[0033] Figure 3 It is the scanning electron microscope diagram of the TiO2 dispersion liquid in Example 1 of the present invention;

[0034] Figure 4 It is the ultraviolet-visible spectrum diagram of the Au-TiO2-SiO2 composite nanomaterial prepared in Example 1 of the present invention;

[0035] Figure 5 It is the particle size distribution diagram of the Au-TiO2-SiO2 composite nanomaterial prepared in Example 1 of the present invention;

[0036] Figure 6 It is the scanning electron microscope diagram of the Au-TiO2-SiO2 composite nanomaterial prepared in Example 1 of the present invention;

[0037] Figure 7 It is the ultraviolet-visible spectrum diagram of AuNP in Example 2 of the present invention S ;

[0038] Figure 8 The particle size distribution diagram of AuNP in Example 2 of the present invention S ;

[0039] Figure 9 The scanning electron microscope image of AuNP in Example 2 of the present invention S ;

[0040] Figure 10 The ultraviolet-visible spectrum diagram of AuNP loaded with TiO2 nanocrystals in Example 2 of the present invention S ;

[0041] Figure 11 The particle size distribution diagram of AuNP loaded with TiO2 nanocrystals in Example 2 of the present invention S ;

[0042] Figure 12 The scanning electron microscope image of AuNP loaded with TiO2 nanocrystals in Example 2 of the present invention S ;

[0043] Figure 13 The ultraviolet-visible spectrum diagram of the TiO2-SiO2 composite nanomaterial in Example 3 of the present invention

[0044] Figure 14 The particle size distribution diagram of the TiO2-SiO2 composite nanomaterial in Example 3 of the present invention

[0045] Figure 15 The scanning electron microscope image of the TiO2-SiO2 composite nanomaterial in Example 3 of the present invention

[0046] Figure 16 The ultraviolet-visible spectrum diagram of the CTAB suspension of AuNP in Example 1 of the present invention S ;

[0047] Figure 17 The particle size distribution diagram of the CTAB suspension of AuNP in Example 1 of the present invention S ;

[0048] Figure 18 The scanning electron microscope image of the CTAB suspension of AuNP in Example 1 of the present invention S ;

[0049] Figure 19 The absorbance change curve of the Au-TiO2-SiO2 composite nanomaterial in Example 1 of the present invention under the irradiation of a 365nm ultraviolet lamp

[0050] Figure 20 The AuNP in Example 2 of the present invention SAbsorbance change curve of the loaded TiO2 nanocrystals under irradiation of a 365 nm ultraviolet lamp;

[0051] Figure 21 This is the absorbance change curve of the TiO2-SiO2 composite nanomaterial in Example 3 of the present invention under irradiation of a 365 nm ultraviolet lamp;

[0052] Figure 22 This is the absorbance change curve of the Au-TiO2-SiO2 composite nanomaterial in Example 1 of the present invention under irradiation of a fluorescent lamp;

[0053] Figure 23 This is AuNP in Example 2 of the present invention S Absorbance change curve of the loaded TiO2 nanocrystals under irradiation of a fluorescent lamp;

[0054] Figure 24 This is the absorbance change curve of the TiO2-SiO2 composite nanomaterial in Example 3 of the present invention under irradiation of a fluorescent lamp;

[0055] Figure 25 This is the absorbance change curve of the TiO2 dispersion in Experimental Example 3 of the present invention under irradiation of a 365 nm ultraviolet lamp;

[0056] Figure 26 This is the absorbance change curve of the TiO2 dispersion in Experimental Example 3 of the present invention under irradiation of a fluorescent lamp. Detailed implementation manners

[0057] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. The materials used in the embodiments of the present invention can be obtained from commercial channels without special instructions.

[0058] Example 1

[0059] An embodiment of the preparation method of the Au-TiO2-SiO2 composite nanomaterial described in the present invention. The preparation method of the TiO2 dispersion in this embodiment is as follows: Mix 5 mL of TTIP with a molar concentration of 3.36 M and 15 mL of IPA evenly, then pour it into a nitric acid aqueous solution with a pH of 5 and continue to stir and mix for 30 - 35 min. The volume of water in the nitric acid aqueous solution is 250 mL, and the volume of nitric acid is about 20 μl; Place the above mixed solution in an oven at 60 °C and dry it for 12 h, then perform ultrasonic cleaning, and then store it at 4 °C for standby, that is, the TiO2 dispersion is obtained. The ultraviolet-visible spectrum of the TiO2 dispersion is as Figure 1 shown, and the particle size distribution diagram is as Figure 2 shown, Figure 2 showing that the size distribution of the TiO2 nanoparticles is relatively uniform. The scanning electron microscope is as Figure 3 shown.

[0060] The preparation method of the Au-TiO2-SiO2 composite nanomaterial described in this embodiment includes the following steps:

[0061] S1. Uniformly mix 6 mL of a CTAB suspension with a concentration of 49.2 μg / mL of AuNP S , 2 mL of EtOH, and 40 μL of NH4OH, and let the mixture stand for 5 min;

[0062] S2. Under the condition of vigorous stirring, drop 2 mL of a TiO2 dispersion with a concentration of 5 mg / mL into the mixture obtained in step S1 and mix well. After mixing, continue to sonicate for 30 min to obtain Au-TiO2 nanocrystals;

[0063] S3. Slowly add 60 μL of TEOS to step S2 and continuously stir for 24 h to remove CTAB in the solution, thereby obtaining the Au-TiO2-SiO2 composite nanomaterial. The ultraviolet-visible spectrogram of the Au-TiO2-SiO2 composite nanomaterial is as shown in Figure 4 , the particle size distribution diagram is as shown in Figure 5 , and the scanning electron microscope is as shown in Figure 6 . Figure 6 It shows that the Au-TiO2-SiO2 composite nanomaterial has a clear core-shell structure.

[0064] The step of removing CTAB in this embodiment is as follows: Add 10 mL of NH4NO3 buffer solution to the mixed solution after stirring for 24 h in step S3. The buffer solution is prepared by mixing 2 g of NH4NO3 with 100 mL of anhydrous EtOH; then centrifuge the above mixture at RCF 20000 and 12 °C for 12 min. After centrifugation, pour out the supernatant. Repeat adding 10 mL of NH4NO3 buffer solution to the remaining solution 2 - 3 times and take out the supernatant. Finally, add anhydrous EtOH to the remaining solution and dissolve it by sonication to remove the CTAB solution.

[0065] The AuNP with a concentration of 49.2 μg / mL in this embodiment SThe preparation method of the CTAB suspension is as follows: (1) Place 250 μL of HAuCl4 with a molar concentration of 0.1 M in a 250 mL beaker, and add 100 mL of H2O for dilution to obtain an HAuCl4 aqueous solution with a molar concentration of 0.00025 M; (2) Add 30 mg of CTAB solution to the HAuCl4 aqueous solution with a molar concentration of 0.00025 M in step (1), and mix and stir for 5 min; (3) Add an aqueous solution of NaBH4 with a molar concentration of 0.1 M to the solution in step (2) and mix well for 15 min. At this time, the solution is dark red. The aqueous solution of NaBH4 with a molar concentration of 0.1 M is obtained by mixing 37.8 mg of NaBH4 with 10 mL of H2O; (4) Let the solution in step (3) stand at a temperature of 4 - 8 °C for 10 - 12 h, and finally add 40 μL of NH4OH to adjust the pH of the mixed solution to 9 - 10, thus obtaining the AuNP with a concentration of 49.2 μg / mL S CTAB suspension, and the AuNP with a concentration of 49.2 μg / mL S The ultraviolet-visible spectrum of the CTAB suspension is as Figure 16 shown, and the particle size distribution diagram is as Figure 17 shown, and the scanning electron microscope is as Figure 18 shown.

[0066] Example 2

[0067] The difference between this example and Example 1 is that in this example, only AuNP with a specific concentration is used S to load TiO2. The specific preparation steps are as follows: Mix 25 mL of AuNP with a concentration of 0.0365 mg / mL S , 23 mL of H2O, 1.4 mL of sodium citrate (SC) aqueous solution, and 0.7 mL of potassium carbonate (K2CO3) aqueous solution in a three-necked flask. After continuously stirring and heating the mixed solution to 90 °C, add 1 mL of TTIP aqueous solution with a molar concentration of 10 mM, and heat the above mixed solution to boiling and continue for 2 h to obtain AuNP S loaded TiO2 nanocrystals; The ultraviolet absorption spectrum of the AuNP with a concentration of 0.0365 mg / mL S is as Figure 7 shown, and the particle size distribution diagram is as Figure 8 shown, and the scanning electron microscope image is as Figure 9 shown; The ultraviolet absorption spectrum of the AuNP S loaded TiO2 nanocrystals is as Figure 10 shown, and the particle size distribution diagram is as Figure 11 shown, and the scanning electron microscope image is as Figure 12 shown.

[0068] In this example, the molar concentration of the SC aqueous solution is 100 mM, and the preparation method is as follows: Weigh 0.041 g of SC into a 1.5 mL centrifuge tube, add 1.4 mL of H2O to dissolve it. The molar concentration of the K2CO3 aqueous solution is 150 mM, and the preparation method is as follows: Weigh 0.015 g of K2CO3 into a 1.5 mL centrifuge tube, add 0.7 mL of H2O to dissolve it; The preparation method of the TTIP aqueous solution with a molar concentration of 10 mM is as follows: Take 30 μL of TTIP into a 1.5 mL centrifuge tube, add 0.97 mL of H2O and mix well for dilution.

[0069] Example 3

[0070] The difference between this example and Example 1 is that in this example, only SiO2 is used to load TiO2, that is, to prepare TiO2-SiO2 composite nanomaterials. The steps are as follows:

[0071] S1. Uniformly mix 3.3 mL of a TiO2 dispersion with a concentration of 5 mg / mL, 3.9 mL of H2O, 1.8 mL of EtOH, and 40 μL of NH4OH, and let the mixture stand for 5 min;

[0072] S2. Drop the mixture of 30 mL of CTAB solution, 0.8 mL of H2O, and 0.2 mL of EtOH into the mixture obtained in step S1 under vigorous stirring, and continue to ultrasonicate for 30 min after mixing;

[0073] S3. Slowly add 60 μL of TEOS to step S2 and continuously stir for 24 h to remove CTAB from the solution, that is, to obtain TiO2-SiO2 composite nanomaterials. The method for removing CTAB from the solution in this example is the same as that in Example 1. The ultraviolet-visible spectrum of the TiO2-SiO2 composite nanomaterials in this example is as Figure 13 shown, the particle size distribution diagram is as Figure 14 shown, and the scanning electron microscope is as Figure 15 shown.

[0074] Experimental Example 1

[0075] The photocatalytic performance of the nanomaterials in Examples 1-3 of the present invention was tested through the photocatalytic degradation of Rhodamine B (RhB) experiment. The specific experimental steps are as follows: (1) Prepare a 2.5 mM RhB solution: Weigh 120 mg of RhB powder and dissolve it in 100 mL of water; (2) Take 0.4 mL of the 2.5 mM RhB solution and dissolve it in 9.6 mL of the nanomaterials in Examples 1-3 with a concentration of 3 mg / mL respectively, and stir evenly; (3) Stir the solution in step (2) for 10 min at 15000 rpm and 12 °C, and then remove the supernatant; (4) Place the remaining mixed solutions under a 365 nm ultraviolet lamp for irradiation. After irradiation for 0 min, 20 min, 60 min, 100 min, 140 min, 180 min, and 220 min, take 1 mL of the mixed solutions in Examples 1-3 respectively, centrifuge at 15000 rpm and 12 °C for 10 min. After centrifugation, take 0.9 mL of the supernatant, dilute it by 2 times, stir evenly, and characterize it with a UV spectrophotometer. The absorbance change curves of Examples 1-3 when irradiated by a 365 nm ultraviolet lamp are as Figures 19 - 21 shown.

[0076] Experimental Example 2

[0077] The difference between this experimental example and Experimental Example 1 is only that: in step (4), the remaining mixed solutions are placed under a fluorescent lamp for irradiation, and the rest of the steps are the same as those in Experimental Example 1. Characterize with a UV spectrophotometer. The absorbance change curves of Examples 1-3 when irradiated by a fluorescent lamp are as Figures 22 - 24 shown.

[0078] Experimental Example 3

[0079] The difference between this experimental example and Experimental Example 1 is only that: the nanomaterials in Examples 1-3 are replaced with ultrapure water, TiO2 dispersion, and AuNP S , respectively, and the rest of the steps are the same as those in Experimental Example 1. Characterize with a UV spectrophotometer. The absorbance of ultrapure water and AuNP S shows almost no change. The absorbance change curve of TiO2 dispersion when irradiated by a 365 nm ultraviolet lamp is as Figure 25 shown.

[0080] Experimental Example 4

[0081] The difference between this experimental example and Experimental Example 1 is only that: the nanomaterials in Examples 1-3 are replaced with ultrapure water, TiO2 dispersion, and AuNP S , respectively, and irradiated under a fluorescent lamp. The rest of the steps are the same as those in Experimental Example 1. Characterize with a UV spectrophotometer. The absorbance of ultrapure water and AuNP S shows almost no change. The absorbance change curve of TiO2 dispersion when irradiated by a fluorescent lamp is as Figure 26 shown.

[0082] Figure 1 The results show that the UV-visible spectrum of the TiO2 dispersion is around 250 nm, indicating that TiO2 has been successfully prepared in this invention; Figure 7 、 22 The results show that AuNP S and AuNP S both have UV absorption peaks at 540 nm in the CTAB suspension, indicating that AuNP S has been successfully prepared in this invention, and AuNP also exists in its CTAB suspension S ; Figure 10 The results show that the AuNP S loaded TiO2 nanocrystals exhibit two characteristic absorption peaks of Au and TiO2, proving that Au has been successfully loaded on the surface of TiO2 in this invention; Figure 4 The results show that the UV absorption peak of the Au-TiO2-SiO2 composite nanomaterial prepared in this invention appears at around 300 nm;

[0083] From Figures 19 - 21 the results of 25, it can be seen that the absorbance changes of the Au-TiO2-SiO2 composite nanomaterial in Example 1 and the TiO2-SiO2 composite nanomaterial in Example 3 of this invention are more obvious when irradiated with a 365 nm UV lamp, and the decreasing trend of the absorbance in Example 1 is stronger than that in Examples 2, 3, and TiO2;

[0084] From Figures 22 - 24 the results of 26, it can be seen that the absorbance changes of the Au-TiO2-SiO2 composite nanomaterial in Example 1 and the TiO2-SiO2 composite nanomaterial in Example 3 of this invention are more obvious when irradiated with a fluorescent lamp, and the decreasing trend of the absorbance in Example 1 is stronger than that in Examples 2, 3, and TiO2;

[0085] In summary, the Au-TiO2-SiO2 composite nanomaterial prepared by the method described in this invention has strong photocatalytic performance, and its photocatalytic performance is stronger than that of only using noble metal or non-metal loading.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this invention rather than to limit the protection scope of this invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of this invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of this invention.

Claims

1. A preparation method of an Au-TiO2-SiO2 composite nanomaterial, characterized in that, It includes the following steps: S1. Uniformly mix the cetyltrimethylammonium bromide suspension of gold nanoparticles, ethanol, and ammonia water, and let the mixed solution stand still; S2. Add the mixed solution described in step S1 to the titanium dioxide dispersion under vigorous stirring and mix well to obtain the gold-titanium dioxide nanocrystal mixed solution; S3. Add tetraethyl orthosilicate to the mixed solution obtained in step S2 and continuously stir to obtain the Au-TiO2-SiO2 composite nanomaterial; In step S1, the volume ratio of the cetyltrimethylammonium bromide suspension of gold nanoparticles, ethanol, and ammonia water is cetyltrimethylammonium bromide suspension of gold nanoparticles:ethanol:ammonia water = 3:1:0.02; In step S1, the preparation method of the cetyltrimethylammonium bromide suspension of gold nanoparticles is as follows: Mix chloroauric acid and cetyltrimethylammonium bromide solution and stir for 5 - 8 min, then add sodium borohydride to the mixed solution and continue to stir for 13 - 17 min until the solution turns dark red, then place it at a temperature of 4 - 8 °C for 10 - 12 h, and finally add ammonia water to adjust the pH of the mixed solution to 9 - 10 to obtain the cetyltrimethylammonium bromide suspension of gold nanoparticles; In step S1, the concentration of the cetyltrimethylammonium bromide suspension of gold nanoparticles is 49.2 μg / mL, and the molar concentration ratio of chloroauric acid to sodium borohydride is chloroauric acid:sodium borohydride = 1:0.0025; In step S2, the volume ratio of the mixed solution described in step S1 to the titanium dioxide dispersion is the mixed solution described in step S1:titanium dioxide dispersion = 4:1; In step S2, the TiO2 dispersion is a TiO2 aqueous solution with a concentration of 5 mg / mL; In step S3, after adding tetraethyl orthosilicate and continuously stirring, the remaining cetyltrimethylammonium bromide in the solution is removed; In step S3, the volume ratio of tetraethyl orthosilicate to the titanium dioxide dispersion in step S2 is tetraethyl orthosilicate:titanium dioxide dispersion = 0.03:

1.

2. The preparation method of the Au-TiO2-SiO2 composite nanomaterial according to claim 1, characterized in that, In step S2, the preparation method of the titanium dioxide dispersion is as follows: Mix titanium isopropoxide and isopropanol evenly, pour it into a nitric acid aqueous solution with a pH of 4.8 - 5 and stir for 30 - 35 min until fully mixed, then dry the mixed solution at a temperature of 60 - 65 °C for 10 - 12 h, and then perform ultrasonic cleaning to obtain the titanium dioxide dispersion.

3. The preparation method of the Au-TiO2-SiO2 composite nanomaterial according to claim 1, characterized in that, The step of removing the remaining cetyltrimethylammonium bromide solution in the solution is as follows: Add 10 mL of ammonium nitrate buffer solution, centrifuge and take out the supernatant, repeat adding 10 mL of ammonium nitrate buffer solution to the remaining solution 2 - 3 times and take out the supernatant, and finally add the remaining solution to anhydrous ethanol and dissolve it by ultrasonic wave to remove the cetyltrimethylammonium bromide solution.

4. The preparation method of the Au-TiO2-SiO2 composite nanomaterial according to claim 3, wherein, In step S3, the ammonium nitrate buffer solution is an ethanol solution of ammonium nitrate with a concentration of 20 g / L.

5. Application of the Au-TiO2-SiO2 composite nanomaterial prepared by the preparation method according to any one of claims 1 - 4 in sewage treatment.

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