Preparation and visual detection application of Ag / {001} Bi2Fe4O9 nanosheet

Abstract

The invention discloses preparation and visual detection application of an Ag / {001} Bi2Fe4O9 nanosheet, relates to the technical field of visual ultra-sensitive detection of 2, 4-dichlorophenol, and aims to realize an in-situ and ultra-sensitive visual detection method for the 2, 4-dichlorophenol. The method comprises the following steps: uniformly mixing a xanthene dye fluorescein aqueous solution, an Ag / {001} Bi2Fe4O9 nanosheet suspension and a 2, 4-dichlorophenol aqueous solution to obtain a solution to be detected; the method comprises the following steps: putting a solution to be detected into a Pomfiley multi-channel photocatalytic reactor, carrying out dark adsorption by stirring without illumination, then starting visible light, carrying out sufficient illumination, filtering by adopting a 22-micron water-phase filtering membrane, and finally testing by adopting an ultraviolet and visible spectrophotometer, thereby completing photosensitization detection of 2, 4-dichlorophenol. According to the invention, the Ag / {001} Bi2Fe4O9 nanosheet can be prepared and applied to visual detection.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of visual super-sensitive detection of 2,4-dichlorophenol, in particular to a preparation method of Ag / {001}Bi2Fe4O9 nanosheets and application of the Ag / {001}Bi2Fe4O9 nanosheets in photosensitized detection of 2,4-dichlorophenol. BACKGROUND

[0002] Among numerous new pollutants, persistent organic new pollutants represented by chlorophenols have high biological toxicity such as environmental persistence, carcinogenicity, teratogenicity and mutagenicity, have extremely high environmental risk, and seriously harm the ecological environment and human health. Among them, 2,4-dichlorophenol is the most common chlorophenol compound in the water environment, is mainly used as a raw material for manufacturing 2,4-dichlorophenoxyacetate (herbicide) and its derivatives (fungicides and disinfectants), and is also used as an intermediate component in the production of preservatives and pharmaceutical products.

[0003] In addition, 2,4-dichlorophenol enters the environment as a by-product of chlorination treatment of drinking water and wastewater and a degradation product of the antibacterial agent trichloro, among others. Only a small part of it diffuses into the air and soil, while most of the 2,4-dichlorophenol enters the surface water and groundwater, posing a threat to human life and animals and plants. The content of the surface water and the groundwater has reached micrograms per liter, and the current environmental 2,4-dichlorophenol organic pollutants are usually at trace or ultratrace levels, so it is necessary to efficiently detect the content of 2,4-dichlorophenol.

[0004] The current detection methods mainly include traditional chromatography-mass spectrometry, liquid chromatography and other methods. Chromatography is based on the difference in physical and chemical properties of 2,4-dichlorophenol in the mixture between the stationary phase and the mobile phase (mainly methanol and acetonitrile), and the different residence times caused by the interaction between the two phases to realize separation and detection. This method requires specific professional large-scale detection equipment, a complex pretreatment process, toxic organic solvents such as methanol and acetonitrile, and high operation requirements for testers, and cannot realize on-site rapid detection, so the detection period is long. Therefore, it is necessary to develop an in-situ, super-sensitive visual detection method. SUMMARY

[0005] The purpose of the application is to realize an in-situ, super-sensitive visual detection method for 2,4-dichlorophenol, and to provide a preparation method of Ag / {001}Bi2Fe4O9 nanosheets and visual detection application.

[0006] The preparation method of the Ag / {001}Bi2Fe4O9 nanosheet is carried out according to the following steps:

[0007] Step S1, preparation of the {001} crystal face exposed Bi2Fe4O9 nanosheet:

[0008] Bi(NO3)3·5H2O was added to a glycol solution, and ultrasonic stirring was performed until complete dissolution to obtain solution A; FeCl3·6H2O was added to deionized water, and after sufficient stirring, solution B was obtained; solution B was added to solution A, and after sufficient stirring, solution C was obtained; NH3·H2O was added to solution C, and after the pH value was adjusted to 9-11, sufficient stirring was performed to obtain solution D; solution D was centrifuged to neutral, the supernatant was discarded, and the precipitate was collected; NaOH solution containing cetyltrimethylammonium bromide was added to the precipitate to obtain solution E;

[0009] After solution E was ultrasonically dispersed, it was placed in a high-temperature reaction kettle and reacted under hydrothermal conditions at 160-200 DEG C for 3-12 h, and a red powder was collected by centrifugation, then washed, dried overnight, the supernatant was discarded, and the remaining yellow product was collected, washed, dried and ground to obtain {001} crystal surface exposed Bi2Fe4O9 nanosheet;

[0010] Step S2, Ag / {001}Bi2Fe4O9 nanosheet was synthesized by low-temperature photodeposition method:

[0011] The {001} crystal surface exposed Bi2Fe4O9 nanosheet obtained in step S1 was added to an ethanol solution, and after ultrasonic dispersion, AgNO3 solution was added, and the mixture was stirred in the dark to obtain a suspension; after irradiation by a full-spectrum xenon lamp, the precipitate was collected, centrifuged and dried to obtain Ag / {001}Bi2Fe4O9 nanosheet.

[0012] The application of Ag / {001}Bi2Fe4O9 nanosheet prepared by the above method, and the application of Ag / {001}Bi2Fe4O9 nanosheet in photosensitized detection of 2,4-dichlorophenol, the specific detection steps are as follows:

[0013] The xanthene dye fluorescein aqueous solution, the Ag / {001}Bi2Fe4O9 nanosheet suspension and the 2,4-dichlorophenol aqueous solution were mixed uniformly to obtain a to-be-detected solution; the to-be-detected solution was placed in a Perfit multi-channel photocatalytic reactor, and was first stirred in the dark for adsorption, then visible light was turned on, and after sufficient light irradiation, a 22 μm aqueous phase filter membrane was used for filtration, and finally an ultraviolet-visible spectrophotometer was used for testing to complete the photosensitized detection of 2,4-dichlorophenol.

[0014] The principle of the application is:

[0015] The xanthene dye fluorescein (FI) with bright color has unique spiro ring conversion characteristics, and can rapidly convert between open ring structure and closed ring structure under certain conditions, Figure 1The FI spiroligand conversion property is demonstrated to induce color change, which is an ideal probe for developing rapid visual detection system. More interestingly, FI can be photoexcited under visible light irradiation to cause the excited state electron of the dye to quickly transfer to the lower energy level of the semiconductor conduction band (CB), at which time the FI loses an electron and can be converted from the colored open ring structure to the colorless closed ring structure, thereby inducing the rapid photosensitized decolorization of FI. Based on this property, if the semiconductor can compete for the adsorption of 2,4-dichlorophenol, 2,4-dichlorophenol can block the electron transfer between the dye FI and the semiconductor, thereby inhibiting the photosensitized decolorization process of FI and realizing the color change of FI. Therefore, the degree of inhibition of 2,4-dichlorophenol on the photosensitized decolorization of FI in the FI-semiconductor photosensitized system can be used to establish a new method for visual detection of 2,4-dichlorophenol.

[0016] Another core component of the photosensitized detection system is the semiconductor that matches the energy level of FI. The lowest unoccupied orbital energy level (LUMO) of the FI dye should be more negative than the conduction band (CB) of the semiconductor, which thermodynamically provides the possibility of electron injection into the semiconductor. The CB of the compound of the metal element bismuth is usually more positive, and the specific chemical adsorption of bismuth atoms and chlorine atoms provides the possibility for the detection of chlorine-containing pollutants. Bi2Fe4O9 is a new type of bismuth-based semiconductor photocatalytic material. Compared with traditional photocatalytic materials, it has a suitable energy band structure, is easy to receive photoexcited electrons of the FI dye, and its high crystallinity and two-dimensional layered structure are more conducive to the surface charge transport and thus promote the photosensitized decolorization.

[0017] In addition, how to improve the selective adsorption of Bi2Fe4O9 to 2,4-dichlorophenol is the key to realizing high-performance detection. The ultrathin structure of Bi2Fe4O9 and the large exposure area of the {001} surface can realize the exposure of Bi and Fe double metals of Bi2Fe4O9, while 2,4-dichlorophenol is a planar structure containing double chlorine atoms, and the double metal exposure provides the possibility for the planar adsorption of 2,4-dichlorophenol; at the same time, using the strong chemical adsorption characteristics of silver (Ag) atoms to chlorine atoms, Ag atoms can be modified on the surface of Bi2Fe4O9 to further enhance the selective adsorption of 2,4-dichlorophenol.

[0018] Based on this, the application differs from the principle and steps of the traditional detection method, and a new dye-semiconductor photosensitization detection method is proposed, and a visual detection method for Ag / {001}Bi2Fe4O9 is constructed based on the prepared Ag / {001}Bi2Fe4O9 and FI. The specific detection principle is that FI can photosensitize Ag / {001}Bi2Fe4O9 under visible light irradiation, and the excited state electrons of FI are quickly transferred to the conduction band (CB) of Ag / {001}Bi2Fe4O9 with a lower energy level, at this time, FI loses electrons and can be converted from a colored open ring structure to a colorless closed ring structure, thereby causing the rapid photosensitization decolorization of FI. However, when 2,4-dichlorophenol is adsorbed on the exposed Ag, Bi and Fe of Ag / {001}Bi2Fe4O9 through coordination, the competitive selective adsorption of Bi2Fe4O9 to 2,4-dichlorophenol is improved, and then 2,4-dichlorophenol can block the electron transfer between the dye FI and Ag / {001}Bi2Fe4O9, thereby inhibiting the photosensitization decolorization process of FI, resulting in the color change of FI. Therefore, the inhibition degree of 2,4-dichlorophenol to the photosensitization decolorization of FI in the FI-Ag / {001}Bi2Fe4O9 photosensitization system, that is, the change of the visible light absorption intensity or the color of FI, is used to establish a new visual detection method for 2,4-dichlorophenol.

[0019] The application has the following beneficial effects:

[0020] The application successfully establishes a FI-Ag / {001}Bi2Fe4O9 photosensitization system for the portable visual rapid detection of 2,4-dichlorophenol, which only needs a visible light source to irradiate the detection system, and then the visual detection of 2,4-dichlorophenol can be realized by detecting the color change degree of the detection system. In the detection system, we use a new synthesis method to synthesize Ag / {001}Bi2Fe4O9 nanosheet material, use the constructed {001} exposed Bi2Fe4O9, and introduce Ag adsorption sites to realize the selective adsorption and enrichment of 2,4-dichlorophenol, and then improve the selectivity and ultra-sensitivity of the detection of 2,4-dichlorophenol.

[0021] The application proposes to construct a new visual fluorescent dye-Ag / {001}Bi2Fe4O9 photosensitization detection system, which is based on the rapid decolorization of FI caused by the photosensitization of FI dye to Ag / {001}Bi2Fe4O9 and the inhibition of the photosensitization decolorization of the dye after the selective adsorption of 2,4-dichlorophenol to the dye, and realizes the quantitative and visual detection of 2,4-dichlorophenol through the change of the absorbance and color of FI.

[0022] The application can obtain the preparation of Ag / {001}Bi2Fe4O9 nanosheet and the visual detection application. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Representing the spirocyclization colorless and colored conversion properties of the xanthene dye fluorescein;

[0024] Figure 2 Representing the SEM image of the {001} facet exposed Bi2Fe4O9 nanosheets prepared in Example 1;

[0025] Figure 3 Representing the AFM image and corresponding height of Ag / {001}Bi2Fe4O9 prepared in Example 1;

[0026] Figure 4 Representing the XRD pattern of Ag / {001}Bi2Fe4O9 prepared in Example 1;

[0027] Figure 5 Representing the FT-IR pattern of Ag / {001}Bi2Fe4O9 prepared in Example 1;

[0028] Figure 6 Representing the discoloration effect of the dye FI in different cases under visible light irradiation in Example 1, ●, ▼ and ■ represent FI alone, FI-Ag / {001}Bi2Fe4O9 system and the blocking of the photosensitized discoloration of FI-Ag / {001}Bi2Fe4O9 after the introduction of 2,4-dichlorophenol, respectively;

[0029] Figure 7 Representing the color response effect of the Ag / {001}Bi2Fe4O9 photosensitized detection system in Example 1 when different concentrations of 2,4-dichlorophenol are added;

[0030] Figure 8 Representing the UV-Vis absorption spectrum of FI when different concentrations of 2,4-dichlorophenol are added to the Ag / {001}Bi2Fe4O9 photosensitized detection system in Example 1;

[0031] Figure 9 Representing the fitting linear relationship between lg(C 2,4-二氯酚 ) and in Example 1;

[0032] Figure 10 Representing the detection response of other pollutants and 2,4-dichlorophenol in Example 1. DETAILED DESCRIPTION

[0033] Detailed implementation one: the preparation method of the Ag / {001}Bi2Fe4O9 nanosheet in the embodiment, which is carried out according to the following steps:

[0034] Step S1, preparing the {001} facet exposed Bi2Fe4O9 nanosheet:

[0035] Bi(NO3)3·5H2O was added to the ethylene glycol solution, and ultrasonic stirring was performed until complete dissolution to obtain solution A; FeCl3·6H2O was added to deionized water, and after sufficient stirring, solution B was obtained; solution B was added to solution A, and after sufficient stirring, solution C was obtained; NH3·H2O was added to solution C, and after the pH value was adjusted to 9-11, sufficient stirring was performed to obtain solution D; solution D was centrifuged to neutral, the supernatant was discarded, and the precipitate was collected; NaOH solution containing cetyltrimethylammonium bromide was added to the precipitate to obtain solution E;

[0036] After solution E was ultrasonically dispersed, it was placed in a high-temperature reaction kettle and reacted under hydrothermal conditions at 160-200°C for 3-12h. Red powder was collected by centrifugation, then washed, dried overnight, the supernatant was discarded, and the remaining yellow product was collected, washed, dried, and ground to obtain {001} crystal surface exposed Bi2Fe4O9 nanosheets;

[0037] Step S2, Ag / {001}Bi2Fe4O9 nanosheets were synthesized by low-temperature photodeposition:

[0038] The {001} crystal surface exposed Bi2Fe4O9 nanosheets obtained in step S1 were added to an ethanol solution, ultrasonically dispersed, and then AgNO3 solution was added. After sufficient stirring in the dark, a suspension was obtained. After irradiation by a full-spectrum xenon lamp, the precipitate was collected, centrifuged, and dried to obtain Ag / {001}Bi2Fe4O9 nanosheets.

[0039] Specific implementation method two: the difference between this implementation method and specific implementation method one is that in step S1, the ratio of the amount of substance of Bi(NO3)3·5H2O to the volume of ethylene glycol solution is (1-5) mmol:100 mL; the ratio of the amount of substance of FeCl3·6H2O to the volume of deionized water is (1-5) mmol:100 mL; the ratio of the amount of substance of Bi(NO3)3·5H2O, the amount of substance of FeCl3·6H2O, and the volume of NaOH solution is (1-5) mmol:(2-4) mmol:(20-40) mL, the concentration of the NaOH solution is 3-6 mol / L, and the mass of cetyltrimethylammonium bromide in the NaOH solution is 0.1-0.4 mg.

[0040] The other steps are the same as specific implementation method one.

[0041] Specific implementation method three: the difference between this implementation method and specific implementation method one or two is that in step S1, Bi(NO3)3·5H2O is added to the ethylene glycol solution, and the ultrasonic time is 10-60 min, and the stirring time is 10-60 min.

[0042] Other steps are the same as embodiment one or two.

[0043] Embodiment four: the difference between this embodiment and one of embodiments one to three is that in step S1, solution B is added to solution A, and after stirring for 10-60 min, solution C is obtained; NH3·H2O is added to solution C, and after adjusting the pH value to 9-11, and stirring for 1-3 h, solution D is obtained; solution D is centrifuged at a speed of 2500-4500 r / min for 1-5 min, the supernatant is discarded, and the precipitate is collected.

[0044] Other steps are the same as embodiments one to three.

[0045] Embodiment five: the difference between this embodiment and one of embodiments one to four is that in step S1, solution E is ultrasonically dispersed for 1-6 min and then placed in a high-temperature reaction kettle; the red powder is collected by centrifugation, then washed with ethanol and deionized water for 3-5 times, and then dried in a vacuum oven at 60-80℃ overnight; the supernatant is discarded, the remaining yellow product is collected, washed, dried in a vacuum oven at 60-80℃, and ground to obtain {001} crystal surface exposed Bi2Fe4O9 nanosheets.

[0046] Other steps are the same as embodiments one to four.

[0047] Embodiment six: the difference between this embodiment and one of embodiments one to five is that in step S2, the mass of {001} crystal surface exposed Bi2Fe4O9 nanosheets, the volume of ethanol solution, and the volume of AgNO3 solution are (40-60) mg: 20 mL: 1 mL, and the mass concentration of AgNO3 in the AgNO3 solution is 780-790 mg / L.

[0048] Other steps are the same as embodiments one to five.

[0049] Embodiment seven: the difference between this embodiment and one of embodiments one to six is that in step S2, after ultrasonic dispersion, AgNO3 solution is added, and after stirring in the dark for 10-60 min, a suspension is obtained.

[0050] Other steps are the same as embodiments one to six.

[0051] Embodiment eight: the difference between this embodiment and one of embodiments one to seven is that in step S2, after irradiation by a 150-300 W full-spectrum xenon lamp for 10-60 min, the precipitate is collected and centrifuged, and then dried in a vacuum oven at 60-80℃ for 11-13 h to obtain Ag / {001}Bi2Fe4O9 nanosheets.

[0052] Other steps are the same as the first to seventh embodiments.

[0053] Ninth embodiment: application of the Ag / {001}Bi2Fe4O9 nanosheet prepared by the method described above, application of the Ag / {001}Bi2Fe4O9 nanosheet in photosensitization detection of 2,4-dichlorophenol, and the specific detection steps are as follows:

[0054] The xanthene dye fluorescein aqueous solution, the Ag / {001}Bi2Fe4O9 nanosheet suspension and the 2,4-dichlorophenol aqueous solution are uniformly mixed to obtain a to-be-detected solution; the to-be-detected solution is placed in a Perfit multi-channel photocatalytic reactor, and dark adsorption is performed by stirring in the dark first, then visible light is turned on, and after sufficient light irradiation, 22 μm water phase filter membrane is used for filtration, and finally ultraviolet-visible spectrophotometry is used for testing to complete the photosensitization detection of 2,4-dichlorophenol.

[0055] Tenth embodiment: the difference between the tenth embodiment and the ninth embodiment is that the xanthene dye fluorescein aqueous solution is prepared by the following steps:

[0056] 0.001~0.004 g xanthene dye fluorescein is diluted to 1000 mL deionized water to obtain 1~4 mg·L -1 Xanthene dye fluorescein aqueous solution;

[0057] The Ag / {001}Bi2Fe4O9 nanosheet suspension is prepared by the following steps:

[0058] 0.1~0.2 g Ag / {001}Bi2Fe4O9 nanosheet is placed in a 100 mL volumetric flask, and deionized water is used for constant volume, and after sufficient ultrasonic and stirring, 1~2 g·L -1 Ag / {001}Bi2Fe4O9 nanosheet suspension;

[0059] The 2,4-dichlorophenol aqueous solution is prepared by the following steps:

[0060] 2,4-dichlorophenol powder is added to a 100 mL volumetric flask, and deionized water is used for constant volume, and after ultrasonic and stirring until the 2,4-dichlorophenol is fully dissolved, a 2,4-dichlorophenol aqueous solution is obtained.

[0061] Other steps are the same as the ninth embodiment.

[0062] The following examples are used to verify the beneficial effects of the present application:

[0063] Example 1:

[0064] 1. Preparation method of Ag / {001}Bi2Fe4O9 nanosheets, according to the following steps:

[0065] Step S1: preparing Bi2Fe4O9 nanosheets with exposed {001} crystal planes:

[0066] 3 mmol Bi(NO3)3·5H2O was added to 100 mL ethylene glycol solution, ultrasonicated for 30 min, and vigorously stirred for 30 min until completely dissolved to obtain solution A; 3 mmol FeCl3·6H2O was added to 100 mL deionized water and stirred thoroughly to obtain solution B; solution B was added to solution A and stirred for 30 min to obtain solution C; NH3·H2O was added to solution C, the pH value was adjusted to 10.5, and then vigorously stirred for 1 h to obtain solution D; solution D was centrifuged at 4000 r / min for 1 min until neutral, the supernatant was discarded, and the precipitate was collected; 20 mL of NaOH solution (concentration of 5 mol / L) containing 0.2 mg hexadecyltrimethylammonium bromide was added to the precipitate to obtain solution E;

[0067] Solution E was ultrasonically dispersed for 5 minutes and then placed in a 50 mL high-temperature reactor. The mixture was reacted under hydrothermal conditions at 180°C for 6 hours. The red powder was collected by centrifugation and then washed with ethanol and deionized water 3 to 5 times in sequence. The powder was then dried in a vacuum oven at 60°C overnight. The supernatant was discarded and the remaining yellow product was collected. After washing, it was dried and ground in a vacuum oven at 60°C to obtain Bi2Fe4O9 nanosheets with exposed {001} crystal faces.

[0068] Step S2: synthesizing Ag / {001}Bi2Fe4O9 nanosheets by low-temperature photodeposition:

[0069] 50 mg of Bi2Fe4O9 nanosheets with exposed {001} crystal faces were added to 20 mL of ethanol solution, and after ultrasonic dispersion, 1 mL of AgNO3 solution (mass concentration of AgNO3 was 787 mg / L) was added. After stirring in the dark for 30 minutes, a suspension was obtained. After irradiation with a 300 W full-spectrum xenon lamp for 30 minutes, the precipitate was collected and centrifuged, and then dried in a vacuum oven at 60°C for 12 hours to obtain Ag / {001}Bi2Fe4O9 nanosheets.

[0070] 2. Characterization of Ag / {001}Bi2Fe4O9 material:

[0071] Figure 2 The SEM image of the Bi2Fe4O9 nanosheets with exposed {001} crystal plane prepared in Example 1 is shown; Figure 2As shown, Ag / {001}Bi2Fe4O9exhibited an ultrathin sheet structure, and then atomic force microscopy (AFM) was employed to determine the thickness of Ag / {001}Bi2Fe4O9. Figure 3 AFM images and corresponding heights of Ag / {001}Bi2Fe4O9prepared in Example 1; as Figure 3 As shown, the thickness of Bi2Fe4O9nanosheets was observed to be close to 3 nm.

[0072] Figure 4 XRD pattern of Ag / {001}Bi2Fe4O9prepared in Example 1; as Figure 4 As shown, the material detected obvious diffraction peaks at 14.7°, 28.2°, 28.9°, 29.7°, 33.7°, 47.0°, 56.6°, corresponding to the (001), (121), (211), (002), (130), (141) and (332) crystal face characteristic diffraction peaks of rhombic Bi2Fe4O9(JCPDS No. 25-0090), respectively, indicating that Bi2Fe4O9with {001} crystal face exposure was successfully synthesized. In addition, the peak intensity and position of XRD did not change significantly after the introduction of Ag, indicating that the Bi2Fe4O9main structure and crystal structure were not affected.

[0073] Figure 5 FT-IR pattern of Ag / {001}Bi2Fe4O9prepared in Example 1; as Figure 5 As shown, the stretching vibration of Bi-O resulted in the detection of a characteristic peak at 440 cm -1 , while the characteristic peaks detected at 484 cm -1 and 810 cm -1 were attributed to the stretching vibration of Fe-O in FeO6and FeO4structural units. In addition, the characteristic peaks detected at 525 cm -1 and 609 cm -1 corresponded to the stretching vibration of O-Fe-O and Fe-O-Fe. It was indicated that Bi2Fe4O9was successfully synthesized, and the main group structure of Bi2Fe4O9was not significantly changed after the introduction of Ag.

[0074] III. Visualization detection of 2,4-dichlorophenol by FI-Ag / {001}Bi2Fe4O9system:

[0075] The xanthene dye fluorescein aqueous solution was prepared according to the following steps:

[0076] 0.003 g of xanthene dye fluorescein was diluted to 1000 mL of deionized water to obtain a 3 mg·L -1 xanthene dye fluorescein aqueous solution;

[0077] The Ag / {001}Bi2Fe4O9 nanosheet suspension is prepared by the following steps:

[0078] 0.15 g of Ag / {001}Bi2Fe4O9 nanosheets is placed in a 100 mL volumetric flask, and then deionized water is added to the mark, and after sufficient ultrasonic and stirring, 1.5 g·L -1 Ag / {001}Bi2Fe4O9 nanosheet suspension is obtained.

[0079] The 2,4-dichlorophenol aqueous solution is prepared by the following steps:

[0080] 2,4-dichlorophenol powder is added to a 100 mL volumetric flask, and then deionized water is added to the mark, and after ultrasonic and stirring until the 2,4-dichlorophenol is fully dissolved, a 2,4-dichlorophenol aqueous solution is obtained.

[0081] Detection process:

[0082] Take 50 mL weighing bottles, respectively, add 10 mL of 3 mg·L -1 FI aqueous solution, 3 mL of 1.5 g·L -1 Ag / {001}Bi2Fe4O9 suspension, 1 mL of 2,4-dichlorophenol aqueous solution with different concentrations, and mix to obtain the solution to be detected, the concentration of the FI aqueous solution is 1.43 mg·L -1 , the concentration of the Ag / {001}Bi2Fe4O9 suspension is 0.32 g·L -1 ; place all the weighing bottles of the solution to be detected in the Perfitel multi-channel photocatalytic reactor, first stir in the dark for 5 min without light, then turn on the visible light, after a certain time of light irradiation, the liquid in the weighing bottle is filtered with a 22 μm water phase filter membrane, and the filtrate is tested with a UV-visible spectrophotometer to complete the photosensitization detection of 2,4-dichlorophenol.

[0083] Figure 6 The figure shows the decolorization effect of dye FI under different conditions in visible light in Example 1, ●, ▼ and ■ represent FI alone, FI-Ag / {001}Bi2Fe4O9 system, and 2,4-dichlorophenol after introduction, respectively, the blocking of photosensitization decolorization of FI-Ag / {001}Bi2Fe4O9; as Figure 6As shown, FI has a certain self-sensitization decolorization under light in the absence of Ag / {001}Bi2Fe4O9, but the decolorization ability is weak; on the contrary, when Ag / {001}Bi2Fe4O9 is introduced, the photoexcited electrons of FI quickly transfer to Ag / {001}Bi2Fe4O9 to occur photosensitized decolorization, and complete photosensitized decolorization can be basically achieved in 5 minutes of light irradiation; however, when 2,4-dichlorophenol is added to the system, the photosensitized decolorization of FI is blocked, so that the photosensitized decolorization of FI is inhibited, and thus the inhibition degree is related to the content of 2,4-dichlorophenol introduced.

[0084] Figure 7 The color response effect diagram of adding different concentrations of 2,4-dichlorophenol in the Ag / {001}Bi2Fe4O9 photosensitized detection system of Example 1 is shown as follows: Figure 7 As shown, when 2,4-dichlorophenol is added to the system, 2,4-dichlorophenol can be selectively adsorbed on Ag / {001}Bi2Fe4O9, which will block the photosensitized decolorization of FI, causing the absorption spectrum intensity of FI to increase, as shown in Figure 7 The degree of photosensitized decolorization of 2,4-dichlorophenol on FI is represented by the blocking rate of FI photosensitized decolorization after adding 2,4-dichlorophenol; The formula (1) is used for calculation:

[0085] (1);

[0086] In the formula, ƞ I represents the blocking rate of FI photosensitized decolorization after adding 2,4-dichlorophenol;

[0087] C I represents the concentration of FI in the detection system after adding 2,4-dichlorophenol, with the unit of mg·L -1 ;

[0088] C represents the concentration of FI after photosensitized decolorization without 2,4-dichlorophenol, with the unit of mg·L -1 ;

[0089] represents the concentration of FI after dark adsorption filtration by Ag / Bi2Fe4O9, with the unit of mg·L -1 .

[0090] The results show that when the introduced concentration of 2,4-dichlorophenol is in the range of 2 ng·L -1 ~ 1 mg·L -1 , the logarithm of the blocking rate of FI has a linear fitting relationship with the logarithm of the concentration of 2,4-dichlorophenol lg[c]; Figure 8 ​UV-Vis absorption spectra of FI in the presence of different concentrations of 2,4-dichlorophenol in the Ag / {001}Bi2Fe4O9 photo-sensitized detection system in Example 1; as shown in Figure 8 the linear fitting equation is = 0.0713lg[C 2,4-二氯酚 ]-0.6184, the linear correlation coefficient R 2 value is 0.990, and the lowest quantitative limit is 2 ng·L -1 .

[0091] Figure 9 The relationship between lg(C 2,4-二氯酚 ) and in Example 1 is shown in the figure; other organic pollutants often coexist in the actual environmental system, in order to explore the selectivity of the Ag / {001}Bi2Fe4O9 photo-sensitized detection system for 2,4-dichlorophenol, Figure 9 several potential interfering substances are shown, and the influence on the detection of 2,4-dichlorophenol after the addition of Ag / {001}Bi2Fe4O9, the results show that in the absence of 2,4-dichlorophenol, the other coexisting interfering substances have low blocking rate of the photo-sensitized decolorization of FI, and the system presents a transparent decolorization state, that is, the photo-sensitized system has no obvious response to other interfering substances; but in the presence of 2,4-dichlorophenol in the system, FI presents light green color, it can be seen that the detection system has obvious selective response to 2,4-dichlorophenol, which shows that the interference of the environment has little effect on the detection result of 2,4-dichlorophenol, so the method realizes excellent selective detection of 2,4-dichlorophenol.

[0092] Other organic pollutants often coexist in the actual environmental system, in order to explore the selectivity of the FI-Ag / {001}Bi2Fe4O9 photo-sensitized detection system for 2,4-dichlorophenol; Figure 10 The influence of other pollutants on the detection of 2,4-dichlorophenol in Example 1 is shown in the figure; as shown in Figure 10 in the absence of 2,4-dichlorophenol, the other interfering substances have low blocking rate of FI, and the system presents a decolorization state, that is, the photo-sensitized system has no obvious response to other interfering substances; but in the presence of 2,4-dichlorophenol in the system, FI presents light green color, it can be seen that the detection system has obvious selective response to 2,4-dichlorophenol, which shows that the interference of the environment has little effect on the detection result of 2,4-dichlorophenol, so the method realizes excellent selective detection of 2,4-dichlorophenol.

[0093] Fourth, the innovation points of the present embodiment:

[0094] The present example successfully establishes the FI-Ag / {001}Bi2Fe4O9 photosensitization system for the first time for the visual rapid detection of 2,4-dichlorophenol: the system can realize the rapid photosensitization decolorization of FI, further utilize the interaction between the exposed rich Bi and Fe sites on the {001} crystal surface of Bi2Fe4O9 and the introduced Ag sites and 2,4-dichlorophenol to improve the selective adsorption and enrichment capacity of 2,4-dichlorophenol, and further improve the selectivity and ultra-sensitivity of the detection of 2,4-dichlorophenol, and realize the portable visual detection of 2,4-dichlorophenol based on the inhibition effect of 2,4-dichlorophenol on the photosensitization decolorization of FI.

Claims

1. Preparation method of Ag / {001}Bi2Fe4O9 nanosheets, characterized in that The preparation method is carried out according to the following steps: Step S1: preparing Bi2Fe4O9 nanosheets with exposed {001} crystal planes: Bi(NO3)3·5H2O was added to an ethylene glycol solution and ultrasonically stirred until completely dissolved to obtain solution A; FeCl3·6H2O was added to deionized water and stirred thoroughly to obtain solution B; solution B was added to solution A and stirred thoroughly to obtain solution C; NH3·H2O was added to solution C, the pH value was adjusted to 9-11, and the solution was stirred thoroughly to obtain solution D; solution D was centrifuged to neutrality, the supernatant was discarded, and the precipitate was collected; and a NaOH solution containing hexadecyltrimethylammonium bromide was added to the precipitate to obtain solution E; Solution E was ultrasonically dispersed and placed in a high-temperature reactor for reaction at 160-200°C for 3-12 hours. The red powder was collected by centrifugation, then washed and dried overnight. The supernatant was discarded, and the remaining yellow product was collected, washed, dried, and ground to obtain Bi2Fe4O9 nanosheets with exposed {001} crystal faces. Step S2: synthesizing Ag / {001}Bi2Fe4O9 nanosheets by low-temperature photodeposition: The Bi2Fe4O9 nanosheets with exposed {001} crystal planes obtained in step S1 were added to an ethanol solution, and after ultrasonic dispersion, an AgNO3 solution was added, and the mixture was stirred thoroughly in the dark to obtain a suspension; After irradiation with a full-spectrum xenon lamp, the precipitate was collected, centrifuged, and dried to obtain Ag / {001}Bi2Fe4O9 nanosheets.

2. The method for preparing Ag / {001}Bi2Fe4O9 nanosheets according to claim 1, characterized in that The ratio of the amount of Bi(NO3)3·5H2O described in step S1 to the volume of the ethylene glycol solution is (1-5) mmol:100 mL; the ratio of the amount of FeCl3·6H2O described in step S1 to the volume of deionized water is (1-5) mmol:100 mL; the ratio of the amount of Bi(NO3)3·5H2O and the amount of FeCl3·6H2O described in step S1 to the volume of the NaOH solution is (1-5) mmol:(2-4) mmol:(20-40) mL, the concentration of the NaOH solution is 3-6 mol / L, and the mass of hexadecyltrimethylammonium bromide in the NaOH solution is 0.1-0.4 mg.

3. The method for preparing Ag / {001}Bi2Fe4O9 nanosheets according to claim 1, characterized in that In step S1, Bi(NO3)3·5H2O is added to the ethylene glycol solution, the ultrasonic time is 10-60 min, and the stirring time is 10-60 min.

4. The method for preparing Ag / {001}Bi2Fe4O9 nanosheets according to claim 1, characterized in that In step S1, solution B is added to solution A, and the mixture is stirred for 10 to 60 minutes to obtain solution C; NH3·H2O is added to solution C, the pH value is adjusted to 9 to 11, and the mixture is stirred for 1 to 3 hours to obtain solution D; Centrifuge solution D at 2500-4500 r / min for 1-5 min, discard the supernatant, and collect the precipitate.

5. The method for preparing Ag / {001}Bi2Fe4O9 nanosheets according to claim 1, characterized in that In step S1, solution E is ultrasonically dispersed for 1 to 6 minutes and then placed in a high-temperature reactor; the red powder is collected by centrifugation, and then washed with ethanol and deionized water 3 to 5 times in sequence, and then dried in a vacuum oven at 60 to 80°C overnight. The supernatant is discarded, and the remaining yellow product is collected, washed, and then dried and ground in a vacuum oven at 60 to 80°C to obtain Bi2Fe4O9 nanosheets with exposed {001} crystal planes.

6. The method for preparing Ag / {001}Bi2Fe4O9 nanosheets according to claim 1, characterized in that The ratio of the mass of the Bi2Fe4O9 nanosheets with exposed {001} crystal planes in step S2, the volume of the ethanol solution, and the volume of the AgNO3 solution is (40-60) mg:20 mL:1 mL, and the mass concentration of AgNO3 in the AgNO3 solution is 780-790 mg / L.

7. The method for preparing Ag / {001}Bi2Fe4O9 nanosheets according to claim 1, characterized in that After ultrasonic dispersion in step S2, AgNO3 solution is added and stirred in the dark for 10 to 60 minutes to obtain a suspension.

8. The method for preparing Ag / {001}Bi2Fe4O9 nanosheets according to claim 1, characterized in that In step S2, after irradiation with a 150-300W full-spectrum xenon lamp for 10-60 minutes, the precipitate is collected and centrifuged, and then placed in a vacuum oven at 60-80°C for 11-13 hours to obtain Ag / {001}Bi2Fe4O9 nanosheets.

9. Use of Ag / {001}Bi2Fe4O9 nanosheets prepared by the method according to any one of claims 1 to 8, characterized in that The application of the Ag / {001}Bi2Fe4O9 nanosheets in photosensitization detection of 2,4-dichlorophenol, the specific detection steps are as follows: An aqueous solution of xanthene dye fluorescein, a suspension of Ag / {001}Bi2Fe4O9 nanosheets, and an aqueous solution of 2,4-dichlorophenol were uniformly mixed to obtain a test solution. The test solution was placed in a Porphyridium multi-channel photocatalytic reactor and first subjected to dark adsorption with stirring without light. Then, visible light was turned on and, after sufficient illumination, the solution was filtered using a 22 μm aqueous filter membrane. Finally, the solution was tested using a UV-visible spectrophotometer to complete the photosensitization detection of 2,4-dichlorophenol.

10. The use of the Ag / {001}Bi2Fe4O9 nanosheets according to claim 9, characterized in that The xanthene dye fluorescein aqueous solution is prepared according to the following steps: 0.001-0.004 g of xanthene dye fluorescein was diluted to 1000 mL of deionized water to obtain 1-4 mg·L -1 Aqueous solution of xanthene dye fluorescein; The Ag / {001}Bi2Fe4O9 nanosheet suspension is prepared according to the following steps: 0.1~0.2 g of Ag / {001}Bi2Fe4O9 nanosheets were placed in a 100 mL volumetric flask and fixed to volume with deionized water. After thorough ultrasonication and stirring, 1~2 g·L -1 Ag / {001}Bi2Fe4O9 nanosheet suspension; The 2,4-dichlorophenol aqueous solution is prepared according to the following steps: Add 2,4-dichlorophenol powder into a 100 mL volumetric flask, dilute to volume with deionized water, and sonicate and stir until 2,4-dichlorophenol is fully dissolved to obtain a 2,4-dichlorophenol aqueous solution.

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