Ta2PdS6 nanobelt as well as preparation method and application thereof

Abstract

The invention discloses a Ta2PdS6 nanobelt as well as a preparation method and application thereof. The Ta2PdS6 nanobelt is a novel ternary two-dimensional transition metal sulfide, simultaneously contains a PdS4 quadrilateral structure and a TaS7 polyhedral structure, has a Van der Waals gap between layers, has a good charge transfer characteristic, is stable in air and is superior to most reported transition metal sulfides. The Ta2PdS6 has high stability and unique structure and physicochemical characteristics, so that the Ta2PdS6 has great potential in the aspect of surface Raman enhancement (SERS) technology application. The thin-layer Ta2PdS6 nano strip is obtained by carrying out lithium alkyl intercalation / ultrasonic stripping on a Ta2PdS6 crystal, and the Ta2PdS6 nano strip is used as a novel SERS (Surface Enhanced Raman Scattering) substrate to show excellent SERS performance on methyl blue (MB).

Description

Technical Field

[0001] The invention relates to a Ta2PdS6 nanobelt and a preparation method and application thereof, belonging to the technical field of two-dimensional multinary transition metal sulfide SERS sensing. Background Art

[0002] Surface enhanced Raman scattering (SERS) technology has attracted extensive attention from researchers due to its advantages such as convenient operation, high sensitivity, fast detection speed and good reproducibility. Two-dimensional transition metal sulfide materials have attracted widespread attention in the field of SERS technology due to their uniform chemical, electronic and optical properties on the surface. Organic dye molecules can be adsorbed on the surface of two-dimensional transition metal sulfide, and charge transfer occurs under light induction, which effectively enhances surface Raman scattering through chemical enhancement mechanism. Two-dimensional transition metal sulfide materials show excellent potential as SERS substrates. Two-dimensional multinary transition metal sulfide is a type of two-dimensional transition metal sulfide. It contains more elements in composition and chemical composition than two-dimensional binary transition metal sulfide. Therefore, the whole system has stronger degrees of freedom and controllability. At the same time, due to its stoichiometric changes and synergistic effects, two-dimensional multinary transition metal sulfide has more novel properties. Phase control technology can change the intrinsic physicochemical properties of two-dimensional multinary transition metal sulfide materials such as the number of layers, crystal phase, electronic structure, surface defects, etc., effectively control its charge transfer ability, thereby improving its SERS performance, and providing new possibilities for the development of new SERS substrate materials. Ta2PdS6 is a new type of two-dimensional ternary transition metal sulfide with special metallic properties. Therefore, it is of great significance to design and synthesize Ta2PdS6 nanoribbons with excellent SERS performance as a new generation of SERS substrate. Summary of the invention

[0003] Purpose of the invention: In order to solve the problem that the charge transfer ability of two-dimensional transition metal sulfides in semiconductor phase is weak, the present invention adopts high-temperature solid-phase synthesis method to prepare metallic Ta2PdS6 crystals, and then synthesizes Ta2PdS6 nanobelts with excellent charge transfer characteristics through n-butyllithium intercalation / ultrasonic exfoliation method, which provides new possibilities for the development of new SERS substrates.

[0004] The present invention is achieved through the following technical solutions: A Ta2PdS6 nanobelt is a ternary two-dimensional transition metal sulfide material, which contains PdS4 quadrilateral and TaS7 polyhedral structures, has van der Waals gaps between layers, and has the characteristic of charge transfer.

[0005] A method for preparing the Ta2PdS6 nanobelt as described above comprises the following steps: S1. Using iodine as an auxiliary agent, tantalum powder, palladium powder and sulfur powder as precursors, a high-temperature solid-phase synthesis method is used to obtain bulk Ta2PdS6 crystals; S2, grinding the Ta2PdS6 crystal into fine powder, adding n-butyl lithium solution with cyclohexane as solvent in an inert atmosphere, standing for 30 minutes to allow lithium ions to be fully embedded in the Ta2PdS6 crystal, taking the precipitate, adding n-hexane solution, after the first centrifugation, collecting the precipitate, and repeatedly centrifuging and washing with n-hexane solution three times to obtain a crude product; S3. Deoxygenated ultrapure water is added to the crude product, and a suspension is obtained after ultrasonic treatment. The suspension is centrifuged at a speed of 2000-3000 rpm for 5-10 min to remove unstripped Ta2PdS6 crystals, and then centrifuged at a speed of 14000-15000 rpm for 5-10 min. Finally, the suspension is repeatedly centrifuged and washed with ultrapure water to obtain Ta2PdS6 nanobelts.

[0006] As a preferred embodiment, the specific operation of the high temperature solid phase synthesis method is: Fill the first end of the quartz tube with tantalum powder and palladium powder, fill the second end of the quartz tube with sulfur powder and iodine, evacuate the quartz tube, seal it, and place it in a tube furnace, so that the first end of the quartz tube is placed in the first reaction area of ​​the tube furnace, and the second end of the quartz tube is placed in the second reaction area of ​​the tube furnace; The first reaction zone is heated to 800-900°C, and the second reaction zone is kept at 850-950°C for 150-250 hours.

[0007] As a preferred embodiment, the mass ratio of the tantalum powder, palladium powder and sulfur powder is 2:1:6.

[0008] As a preferred embodiment, the rotation speed of the first centrifugal separation in step S2 is 6000 rpm.

[0009] A use of the Ta2PdS6 nanoribbon as described above in a SERS substrate.

[0010] A method for preparing the SERS substrate as described above comprises the following steps: Making silicon wafer substrate; The Ta2PdS6 nanobelts are dispersed in ethanol, and then drop-coated on the surface of the silicon wafer substrate. After vacuum drying, a SERS substrate is obtained.

[0011] As a preferred solution, the method for making the silicon wafer substrate is: After the silicon wafer was cut into squares with a side length of 0.4 cm, it was ultrasonically treated in a mixed solvent of acetone and water for 20 min, then rinsed with deionized water and dried with nitrogen to obtain a primary product; The primary product was further cleaned by immersing it in a piranha solution and keeping it at 120° C. for 1 h. After the piranha solution was cooled, it was taken out, washed thoroughly with deionized water, dried with nitrogen, and soaked in anhydrous ethanol for later use.

[0012] As a preferred embodiment, the volume ratio of acetone to water is 1:1 Compared with the prior art, the present invention has the following advantages: The Ta2PdS6 nanobelt in the present invention is a new two-dimensional ternary transition metal sulfide material with strong stability and can remain stable in the air for one year. The prepared Ta2PdS6 nanobelt has good charge transfer characteristics, and its high stability and unique structure and physicochemical properties make it very potential for application in SERS technology. As a new type of SERS substrate, Ta2PdS6 nanobelt exhibits excellent SERS performance for methyl blue (MB).

[0013] The Ta2PdS6 nanobelt prepared by the present invention has a strip-like morphology, a length of up to micrometer level, and a width of about 400-700nm. MB dye molecules were selected as probes to test the Ta2PdS6 nanobelt substrate. The results showed that the detection limit of the Ta2PdS6 nanobelt substrate for MB can reach 10-10M, and the enhancement factor is 6.96×107. Due to the high stability of the Ta2PdS6 nanobelt and its good charge transfer characteristics, it exhibits excellent SERS performance as a substrate.

[0014] In summary, the Ta2PdS6 nanobelts prepared by the present invention exhibit good SERS performance. The thin-layer two-dimensional ternary transition metal sulfide nanobelts with excellent SERS performance are prepared by treating two-dimensional ternary transition metal sulfide crystals with phase control technology, which provides new possibilities for the development of new SERS substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 TEM image of the Ta2PdS6 crystal prepared in Example 1 of the present invention; Figure 2 This is a SEM image of the Ta2PdS6 crystal prepared in Example 1 of the present invention; Figure 3 TEM image of the Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Figure 4 HRTEM image of the Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Figure 5HRTEM image of the Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Figure 6 The Raman spectra of the Ta2PdS6 crystal and Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Figure 7 High-resolution Ta 4f XPS spectra of Ta2PdS6 crystals and Ta2PdS6 nanobelts prepared in Example 1 of the present invention; Figure 8 High-resolution Pd 3d XPS spectra of Ta2PdS6 crystals and Ta2PdS6 nanobelts prepared in Example 1 of the present invention; Fig. 9 High-resolution S 2pXPS spectra of Ta2PdS6 crystals and Ta2PdS6 nanobelts prepared in Example 1 of the present invention; Fig.10 This is the XRD characterization diagram of the Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Fig.11 The Raman detection spectra of the substrate of Ta2PdS6 nanobelt prepared in Example 1 of the present invention for different concentrations of MB; Fig.12 The Raman spectra of MB detected at 30 different points on the substrate of Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Fig.13 1625 cm on the substrate of Ta2PdS6 nanobelt prepared in Example 1 of the present invention -1 The log-linear relationship between the peak intensity at and the MB molecular concentration; Fig.14 This is a graph showing the average Raman signal intensity of 30 test points of MB tested on the substrate of Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Fig.15 This is a photostability test diagram of the SERS substrate of Ta2PdS6 nanobelt prepared in Example 1 of the present invention; Fig.16 This is a comparison chart of the Raman spectra of MB detected at different excitation wavelengths on the substrate of Ta2PdS6 nanobelt prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0016] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0017] The raw materials in the present invention are all commercially available.

[0018] Iodine, palladium powder, tantalum powder, sulfur powder, n-butyl lithium solution, concentrated sulfuric acid, and acetone were purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd. Methylene blue was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0019] Example 1 This embodiment provides a method for preparing Ta2PdS6 nanoribbons, which specifically includes the following steps: First, Ta2PdS6 bulk crystals were prepared by high-temperature solid-phase synthesis. Iodine was selected as the transmission gas, and well-formed bulk Ta2PdS6 crystals were finally synthesized by chemical vapor transmission. 0.3 g of high-purity tantalum powder, palladium powder and sulfur powder (Ta: Pd: S = 2: 1: 6) (mass ratio) and 120 mg of iodine were sealed in a vacuum quartz tube of 20 cm in length, which was placed in a vacuum state of 10-6Torr and placed in a double-temperature zone furnace. When filling, the quartz tube filled with tantalum powder and palladium powder was marked as the first end, and the sulfur powder and iodine were filled at the other end of the quartz tube, which was marked as the second end. Next, the reaction zone (the area where the first end of the quartz tube is located) is slowly heated to 850°C, and the other area (the area where the second end of the quartz tube is located) is always maintained at 900°C. After the reaction is carried out for 200 hours, the reaction furnace is naturally cooled to room temperature, the product is taken out, and then the iodine on the surface of the product is washed away with acetone to obtain bulk Ta2PdS6 crystals.

[0020] The bulk Ta2PdS6 crystal synthesized above was ground into fine powder, 100 mg of Ta2PdS6 solid powder was placed in a 20 mL glass bottle, 6 mL of n-butyl lithium solution (concentration of 2M) with cyclohexane as solvent was added in a glove box with helium atmosphere, and the solution was allowed to stand for 30 min to allow lithium ions to be fully embedded in the Ta2PdS6 crystal. The upper solution of n-butyl lithium was carefully removed, leaving the precipitate, and 5 mL of n-hexane solution was added to the precipitate, which was then centrifuged at 6000 rpm for 10 min, the supernatant was discarded, and the precipitate was repeatedly centrifuged and washed three times with n-hexane solution, and the precipitate was naturally dried in the glove box. The dried material was taken out of the glove box, 50 mL of deoxygenated ultrapure water was added, and then ultrasonicated for 30 min. The suspension obtained by ultrasound was first centrifuged at 2500 rpm for 5 min to remove the unpeeled Ta2PdS6 crystals, then centrifuged at 14800 rpm for 5 min, and then repeatedly centrifuged and washed three times with ultrapure water to obtain the final product, metallic Ta2PdS6 nanobelts.

[0021] The Ta2PdS6 crystal prepared in Example 1 was characterized. From the TEM image ( Figure 1 ) and SEM ( Figure 2) The Ta2PdS6 crystal morphology obtained by image observation is strip-shaped, with a length of up to micrometers and a width of about 400-700 nm. The morphology and structure of Ta2PdS6 nanobelts prepared by alkyl lithium intercalation / ultrasonic exfoliation of Ta2PdS6 crystals were observed by TEM ( Figure 3 ) and HRTEM characterization ( Figure 4 , 5 ). Figure 3 It shows that the product after peeling still maintains a strip shape and a thin layer structure. Figure 4 and Figure 5 The lattice fringes of Ta2PdS6 nanobelts are clearly shown, and the lattice spacing is about 0.17nm, corresponding to the (112) crystal plane of Ta2PdS6 crystals. In order to obtain the structural information of Ta2PdS6 crystals and Ta2PdS6 nanobelts, their Raman spectra were tested and characterized respectively. Figure 6 As shown in the figure, the Raman characteristic peak of Ta2PdS6 nanoribbons is slightly red-shifted compared with that of Ta2PdS6 crystal, and the peak at 163.2 cm -1 The corresponding peak disappears. The atomic valence states in the Ta2PdS6 nanoribbons are determined by XPS, such as Figure 7 , 8 As shown in Figures 9 and 10, the XPS spectrum peaks of Ta 4f are located at 26.0 eV and 24.0 eV, corresponding to Ta 4f5 / 2 and Ta 4f7 / 2 of Ta2PdS6, respectively. The XPS spectrum peaks of Pd 3d are located at 342.6 eV and 337.3 eV, respectively belonging to Pd 3d3 / 2 and Pd 3d5 / 2 of Ta2PdS6. The XPS spectrum peaks of S2p are located at 162.6 eV and 161.4 eV, corresponding to S 3p1 / 2 and S 2p3 / 2 of Ta2PdS6, respectively. Fig.10 This is the XRD characterization diagram of the Ta2PdS6 nanobelt prepared in Example 1. As can be seen from the figure, the XRD peaks of the Ta2PdS6 nanobelt prepared by exfoliation correspond well to the XRD characteristic peaks of the theoretically simulated Ta2PdS6, indicating that the prepared Ta2PdS6 nanobelt maintains a good high crystallinity. TEM, SEM, HRTEM and XPS characterization further prove the successful preparation of the Ta2PdS6 nanobelt.

[0022] The Ta2PdS6 nanobelt prepared in Example 1 is used to make a substrate.

[0023] First, a silicon wafer substrate was prepared. The silicon wafer was cut into 0.4 cm × 0.4 cm size using a glass knife, and ultrasonically treated in a mixed solvent of acetone and water (v:v=1:1) for 20 min, then rinsed with deionized water, and dried with nitrogen. The treated silicon wafer was further cleaned by immersing it in a piranha solution (a mixed solution of 98% H2SO4 and 30% H2O2, with a volume ratio of 7:3) and kept at 120°C for 1 h. After the solution cooled, the silicon wafer was taken out, thoroughly washed with deionized water, and dried with nitrogen. The cleaned silicon wafer was immersed in anhydrous ethanol for later use. The Ta2PdS6 nanobelt prepared in Example 1 was ultrasonically homogenized, and 40 μL of the Ta2PdS6 nanobelt solution was drop-coated on the cleaned silicon wafer, and dried in a vacuum drying oven to obtain a SERS substrate based on Ta2PdS6 nanobelts. After that, different concentrations of MB dye molecule solutions were prepared, with a concentration gradient of 10 -4 ~ 10 -10 M, carefully remove the Ta2PdS6 nanobelt substrate, clean the unadsorbed dye molecules on the surface with deionized water and anhydrous ethanol, then blow dry the substrate material with nitrogen gas and prepare for Raman testing at room temperature.

[0024] The Ta2PdS6 nanobelt substrate prepared above was used for SERS signal detection. The Raman test conditions were set to laser 785 nm and the scanning wave number range was 800~2000 cm -1 , 30 test points were selected on each substrate, the test power was 0.1 mW, and the exposure time was 1 s. Fig.11 The Raman detection spectra of MB with different concentrations on the substrate of Ta2PdS6 nanobelts show that the MB dye molecule has three obvious characteristic peaks, located at 1303 cm-1, 1397 cm-1, and 1625 cm-1. The intensity of the Raman characteristic peaks of MB with different concentrations gradually weakens as the concentration of MB decreases. The detection limit of MB on the substrate of Ta2PdS6 nanobelts can reach 7.76×10-9M, and the enhancement factor is 6.96×107; Fig.12 This is the Raman spectrum of 30 different points on the Ta2PdS6 nanobelt substrate, from which the uniformity of the Raman signal can be seen. Fig.13 This is a log-linear relationship diagram between the Raman peak intensity at 1625 cm-1 and the concentration of MB dye molecules on the Ta2PdS6 nanobelt substrate. As shown in the figure, the Raman peak intensity at 1625 cm-1 shows a good linear relationship with the concentration of MB. Fig.14 The figure is the average Raman signal intensity of 30 test points on the Ta2PdS6 nanobelt substrate. The average intensity of the Raman signal is 3542.77, and the relative error is 6.11%. It can be seen that the signal uniformity of the substrate is good and the error is small. The photostability test results of the Ta2PdS6 nanobelt substrate are shown in Figure 1. Fig.15 As shown in the figure, the spectrum was collected every 30 seconds at the same point on the Ta2PdS6 nanobelt substrate, and a total of 12 times were collected. It can be seen that there is no significant difference in the 12 Raman spectra, indicating that the Ta2PdS6 nanobelt substrate has good photostability, which lays the foundation for its practical application in SERS analysis technology. In addition, the Raman spectra of MB detected by Ta2PdS6 nanobelt substrate under different excitation wavelengths were compared, as shown in the figure. Fig.16 As shown in the figure, the Raman spectrum belonging to MB can be clearly seen at an excitation wavelength of 785 nm, while the characteristic Raman peak of MB cannot be observed at an excitation wavelength of 532 nm, indicating that the SERS enhancement effect can only be achieved at the corresponding excitation wavelength.

[0025] The Raman detection of MB molecules showed a low detection limit and good signal uniformity, indicating that the synthesized Ta2PdS6 nanobelts have good SERS performance. At the same time, the high stability of Ta2PdS6 nanobelts also ensures that it can be used as a SERS substrate with good test repeatability.

[0026] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A Ta2PdS6 nanobelt is a ternary two-dimensional transition metal sulfide material, which contains PdS4 quadrilateral and TaS7 polyhedral structures, has van der Waals gaps between layers, and has the characteristics of charge transfer.

2. A method for preparing Ta2PdS6 nanobelts as claimed in claim 1, characterized in that: The steps include: S1. Using iodine as an auxiliary agent, tantalum powder, palladium powder and sulfur powder as precursors, a high-temperature solid-phase synthesis method is used to obtain bulk Ta2PdS6 crystals; S2, grinding the Ta2PdS6 crystal into fine powder, adding n-butyl lithium solution with cyclohexane as solvent in an inert atmosphere, standing for 30 min to allow lithium ions to be fully embedded in the Ta2PdS6 crystal, taking the precipitate, adding n-hexane solution, after the first centrifugation, collecting the precipitate, and repeatedly centrifuging and washing with n-hexane solution three times to obtain a crude product; S3. Deoxygenated ultrapure water is added to the crude product, and a suspension is obtained after ultrasonic treatment. The suspension is centrifuged at a speed of 2000-3000 rpm for 5-10 min to remove unstripped Ta2PdS6 crystals, and then centrifuged at a speed of 14000-15000 rpm for 5-10 min. Finally, the suspension is repeatedly centrifuged and washed with ultrapure water to obtain Ta2PdS6 nanobelts.

3. The method for preparing Ta2PdS6 nanoribbons according to claim 2, characterized in that: The specific operation of the high temperature solid phase synthesis method is: Fill the first end of the quartz tube with tantalum powder and palladium powder, fill the second end of the quartz tube with sulfur powder and iodine, evacuate the quartz tube, seal it, and place it in a tube furnace, so that the first end of the quartz tube is placed in the first reaction area of ​​the tube furnace, and the second end of the quartz tube is placed in the second reaction area of ​​the tube furnace; The first reaction zone is heated to 800-900° C., and the second reaction zone is kept at 850-950° C. for 150-250 hours.

4. The method for preparing Ta2PdS6 nanobelts according to claim 3, characterized in that: The mass ratio of the tantalum powder, palladium powder and sulfur powder is 2:1:

6.

5. The method for preparing Ta2PdS6 nanobelts according to claim 2, characterized in that: The rotation speed of the first centrifugal separation in step S2 is 6000 rpm.

6. Use of the Ta2PdS6 nanoribbon as claimed in claim 1 in a SERS substrate.

7. A method for preparing a SERS substrate as claimed in claim 5, characterized in that: The steps include: Making silicon wafer substrate; The Ta2PdS6 nanobelts are dispersed in ethanol, and then drop-coated on the surface of the silicon wafer substrate. After vacuum drying, a SERS substrate is obtained.

8. The method for preparing a SERS substrate according to claim 7, wherein: The method for making the silicon wafer substrate is as follows: After the silicon wafer was cut into squares with a side length of 0.4 cm, it was ultrasonically treated in a mixed solvent of acetone and water for 20 min, then rinsed with deionized water and dried with nitrogen to obtain a primary product; The primary product was further cleaned by immersing it in a piranha solution and keeping it at 120° C. for 1 h. After the piranha solution was cooled, it was taken out, washed thoroughly with deionized water, dried with nitrogen, and soaked in anhydrous ethanol for later use.

9. The method for preparing a SERS substrate according to claim 8, characterized in that: The volume ratio of the acetone to the water is 1:1.

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