Disclosure of Invention
Therefore, the invention provides the SERS substrate of the silver bromide nanowire, which has higher SERS performance. It is another object of the present invention to provide a method for preparing the substrate.
The substrate of the invention adopts the technical scheme that:
the SERS substrate of the silver bromide nanowire comprises a substrate, a silver film and the silver bromide nanowire, wherein the silver film is located on the substrate, and the silver bromide nanowire is located on the silver film.
Preferably, the thickness of the silver film is 100-400 nm.
Preferably, the silver bromide nanowires have the length of 0.6-6 mu m and the diameter of 30-150 nm.
Preferably, the substrate is a silicon wafer polished on a single surface, and the silicon wafer is a monocrystalline silicon wafer or a polycrystalline silicon wafer.
The invention relates to a preparation method of an SERS substrate of silver bromide nanowires, which comprises the following steps:
(1) preparing a silver film: sputtering a silver film with the thickness of 100-400 nm on a substrate by adopting a magnetron sputtering method;
(2) preparing silver bromide nanowires: and (2) soaking the silver film obtained in the step (1) in 1mL of mixed solution consisting of 50mM/L ferric nitrate nonahydrate, 40mM/L sodium bromide and 50mM/L polyvinylpyrrolidone for reaction for 0.5-8 h by adopting an in-situ silver oxide film method, wherein the obtained product is the SERS substrate of the silver bromide nanowire.
The invention provides a preparation method of an SERS substrate with a noble metal silver and semiconductor silver bromide nano mixed structure and an in-situ silver oxide film, aiming at the defects of non-uniformity and instability of the conventional SERS substrate. The noble metal silver nanoparticles have the plasma effect and excellent conductivity, so that the semiconductor material silver bromide can stably exist under visible light, and meanwhile, the interface between the noble metal silver and the semiconductor has strong charge transfer (chemical enhancement) and electromagnetic field (physical enhancement), thereby being beneficial to the substrate to generate uniform SERS signals with high strength and good stability.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention.
The SERS substrate of the embodiment comprises a silicon wafer with a polished single surface, a silver film on the polished surface of the silicon wafer and a silver bromide nanowire, wherein the chemical formula is Ag-AgBr, and the silver bromide nanowire is positioned on the silver film.
Example 1
(1) Preparing a silver film, and sputtering a layer of silver film with the thickness of 200nm on a silicon wafer by adopting magnetron sputtering.
(2) And (2) preparing silver bromide nanowires, namely soaking the silver film obtained in the step (1) in 1mL of mixed solution of ferric nitrate nonahydrate (50mM/L), sodium bromide (40mM/L) and polyvinylpyrrolidone (PVP, K-30, 50mM/L) for reaction for 0.5h by adopting an in-situ silver oxide film method to obtain an Ag-AgBr product.
The silver bromide nanowire structure on the substrate prepared by this example, as shown in fig. 1, the size of the nanowire bar is: the longitudinal length is 2 + -0.1 μm and the transverse diameter is 30 + -2 nm.
Example 2
(1) Preparing a silver film, and sputtering a layer of silver film with the thickness of 200nm on a silicon wafer by adopting magnetron sputtering.
(2) And (2) preparing silver bromide nanowires, namely soaking the silver film obtained in the step (1) in 1mL of mixed solution of ferric nitrate nonahydrate (50mM/L), sodium bromide (40mM/L) and polyvinylpyrrolidone (PVP 50mM/L) for reaction for 1h by adopting an in-situ silver oxide film method, and obtaining a product, namely Ag-AgBr.
The silver bromide nanowire structure on the substrate prepared by this example, as shown in fig. 2, the size of the nanowire bar is: the longitudinal length is 3 + -0.2 μm and the transverse diameter is 40 + -5 nm.
Example 3
(1) Preparing a silver film, and sputtering a layer of silver film with the thickness of 200nm on a silicon wafer by adopting magnetron sputtering.
(2) And (2) preparing silver bromide nanowires, namely soaking the silver film obtained in the step (1) in 1mL of mixed solution of ferric nitrate nonahydrate (50mM/L), sodium bromide (40mM/L) and polyvinylpyrrolidone (PVP, 50mM/L) for reaction for 2 hours by adopting an in-situ silver oxide film method, and obtaining the product, namely Ag-AgBr.
The silver bromide nanowire structure on the substrate prepared by this example, as shown in fig. 3, the size of the nanowire bar is: the longitudinal length is 2 + -0.02 μm and the transverse diameter is 150 + -10 nm. The corresponding XRD pattern of the substrate is shown in fig. 7.
Example 4
(1) Preparing a silver film, and sputtering a layer of silver film with the thickness of 200nm on a silicon wafer by adopting magnetron sputtering.
(2) And (2) preparing silver bromide nanowires, namely soaking the silver film obtained in the step (1) in 1mL of mixed solution of ferric nitrate nonahydrate (50mM/L), sodium bromide (40mM/L) and polyvinylpyrrolidone (PVP, 50mM/L) for reaction for 4 hours by adopting an in-situ silver oxide film method, and obtaining the product, namely Ag-AgBr.
The silver bromide nanowire structure on the substrate prepared by this example, as shown in fig. 4, the size of the nanowire bar is: the longitudinal length is 6 + -0.5 μm and the transverse diameter is 70 + -5 nm.
Example 5
(1) Preparing a silver film, and sputtering a layer of silver film with the thickness of 200nm on a silicon wafer by adopting magnetron sputtering.
(2) And (2) preparing silver bromide nanowires, namely soaking the silver film obtained in the step (1) in 1mL of mixed solution of ferric nitrate nonahydrate (50mM/L), sodium bromide (40mM/L) and polyvinylpyrrolidone (PVP, 50mM/L) for reaction for 6h by adopting an in-situ silver oxide film method, and obtaining the product, namely Ag-AgBr.
The silver bromide nanowire structure on the substrate prepared by this example, as shown in fig. 5, the size of the nanowire bar is: the longitudinal length is 4 + -0.3 μm and the transverse diameter is 40 + -4 nm.
Example 6
(1) Preparing a silver film, and sputtering a layer of silver film with the thickness of 200nm on a silicon wafer by adopting magnetron sputtering.
(2) And (2) preparing silver bromide nanowires, namely soaking the silver film obtained in the step (1) in 1mL of mixed solution of ferric nitrate nonahydrate (50mM/L), sodium bromide (40mM/L) and polyvinylpyrrolidone (PVP, 50mM/L) for reaction for 8 hours by adopting an in-situ silver oxide film method, and obtaining the product, namely Ag-AgBr.
The silver bromide nanowire structure on the substrate prepared by this example, as shown in fig. 6, the size of the nanowire bar is: the longitudinal length is 0.6 + -0.05 μm and the transverse diameter is 50 + -3 nm.
Example 7
This example provides an implementation process for linking the Ag-AgBr substrate prepared in examples 1 to 6 to a raman labeled molecule and detecting its SERS spectrum. The method comprises the following specific steps:
(1) p-mercaptobenzoic acid (4MBA) was used as a Raman labeling molecule to prepare a solution of p-mercaptobenzoic acid (4MBA) at a concentration of 10 mM.
(2) And (3) soaking the Ag-AgBr substrate prepared in the embodiment 1-6 in a 4MBA solution drop, placing the solution at room temperature for 3 hours, after full linkage, washing the 4MBA labeled molecules which are not linked to the substrate with deionized water, washing for 2-3 times, and then placing the substrate at room temperature for natural drying.
(3) Measuring the SERS spectrum of the 4 MBA-labeled molecules linked from the Ag-AgBr substrate prepared in step (2). For detection, a small raman spectrometer (BWS415, B & W Tek Inc.) was used, and the characteristic SERS spectrum of the 4 MBA-labeled molecule recorded by the raman spectrometer is shown in fig. 8. The integration time for collecting the SERS spectrum is 10s, the power of the irradiation laser is 26mw, and the laser wavelength is 785 nm.
As can be seen from FIG. 8, the substrates prepared in examples 1 to 6 have excellent SERS characteristics. Among them, the substrate prepared in example 4 has the optimal SERS activity.
Example 8
This example shows an implementation of linking the Ag-AgBr substrate prepared in example 4 with raman labeled molecules of different concentrations and detecting its SERS spectrum. The method comprises the following specific steps:
(1) p-mercaptobenzoic acid (4MBA) is used as a Raman marker molecule, and the preparation concentration is 10-2M~10-7M in p-mercaptobenzoic acid (4 MBA).
(2) And (3) soaking a plurality of Ag-AgBr substrates prepared in the embodiment 4 in 4MBA solutions with different concentrations, placing the substrates at room temperature for 3 hours, after full linking, washing the 4MBA labeled molecules which are not linked to the substrates by using deionized water, washing for 2-3 times, and then placing the substrates at room temperature for natural drying.
(3) Measuring the SERS spectrum of the Ag-AgBr substrate-linked 4MBA labeled molecule prepared in the step (2). For detection, a small raman spectrometer (BWS415, B & W Tek Inc.) was used, and the characteristic SERS spectrum of the 4 MBA-labeled molecule recorded by the raman spectrometer is shown in fig. 9. The integration time for collecting the SERS spectrum is 10s, the power of the irradiation laser is 26mw, and the laser wavelength is 785 nm.
As can be seen from FIG. 9, the SERS spectrum intensity decreases with the decrease of the 4MBA concentration, and when the 4MBA concentration is 10-71078 and 1560cm of labeled molecule can be still clearly seen at M-1Characteristic peak of (2). The Ag-AgBr substrate has excellent sensitivity and can be used for molecular detection.
The above description is only a preferred embodiment of the present invention, and it should be noted that any simple modification and modification of the above embodiments according to the technical essence of the present invention are still within the protection scope of the technical solution of the present invention for those skilled in the art without departing from the content of the technical solution of the present invention.