A method for cleaning surface-enhanced Raman substrate and achieving reusability

Abstract

The present invention discloses a method for cleaning a surface enhanced Raman substrate and achieving reusability, which belongs to the field of molecular recognition and nano-preparation, and can clean the surface of a substrate without affecting the SERS activity of the substrate. The present invention targets a substrate with impurities and detection molecules, uses an atomic layer deposition technique to coat it with a uniform layer of oxide, and performs high-temperature annealing to decompose the pollutants on its surface, and finally removes the oxide coating on the surface by chemical corrosion, thereby obtaining a pure substrate, which can achieve the purpose of cleaning the substrate and making it reusable.

Description

Technical Field

[0001] The invention belongs to the field of molecular recognition and nano-preparation, and in particular relates to a method for cleaning a surface enhanced Raman substrate and achieving reusability. Background Art

[0002] Surface enhanced Raman spectroscopy (SERS) has experienced continuous development in the decades since its discovery. Compared with other detection methods, SERS technology has the advantages of non-destructive detection, high sensitivity and rapid detection. It has been applied to many fields, and researchers have manufactured various SERS substrates based on the SERS enhancement mechanism. Among the many methods for manufacturing SERS substrates, chemical synthesis of SERS active substrates has been favored by many researchers due to its simple operation, low cost and high efficiency. However, chemical synthesis of substrates often requires the participation of surfactants, and the formed SERS substrates are prone to surfactants. In addition, not only chemical but also physical synthesis of substrates are prone to adsorb organic impurities in the open environment, which directly causes the formation of surface pollutants. The presence of surfactants and pollutants will greatly affect the quantitative detection and analysis of SERS substrates, thereby directly reducing the actual use value of the substrates. In addition, most substrates cannot be used after adsorbing detection molecules, resulting in waste of raw materials and rising costs. How to make the used substrates reusable is an important research direction in the current SERS field. Summary of the invention

[0003] The present invention provides a method for cleaning a surface enhanced Raman substrate and achieving reusability. In view of the fact that conventional technologies cannot remove impurities remaining on the substrate surface and the difficulty in detecting molecules, an innovative method for obtaining a clean surface and achieving reusability is proposed without affecting the SERS activity of the substrate.

[0004] To achieve the above objectives, the present invention adopts the following technical solutions:

[0005] A method for cleaning a surface enhanced Raman substrate and achieving reusability, comprising the following steps:

[0006] 1) ALD deposition of oxide film: The SERS substrate containing impurities is transferred to the ALD reaction chamber, and the thickness is precisely controlled by the number of cycles to deposit an oxide film of 1-10 nm, preferably aluminum oxide or zinc oxide film, to form a composite structure wrapped with an oxide film (SERS substrate@oxide);

[0007] The parameters for ALD deposition of aluminum oxide are:

[0008] Reaction chamber temperature: room temperature ~ 200 ℃;

[0009] Reaction source: Trimethylaluminum and water were used to deposit aluminum oxide, and the source temperature was room temperature;

[0010] Pulse and cleaning time: The pulses of the metal source and water source are both 1 to 5 seconds. After each pulse, they are cleaned with high-purity nitrogen for 4 to 100 seconds to flush away the reaction by-products and residual reaction sources.

[0011] The parameters for ALD deposition of zinc oxide are:

[0012] Reaction chamber temperature: room temperature ~ 200 ℃;

[0013] Reaction source: Diethyl zinc and water are used to deposit zinc oxide, and the source temperature is room temperature;

[0014] Pulse and cleaning time: The pulses of the metal source and water source are both 1 to 5 seconds. After each pulse, they are cleaned with high-purity nitrogen for 4 to 100 seconds to flush away the reaction by-products and residual reaction sources.

[0015] 2) High temperature annealing: The oxide-wrapped SERS substrate is subjected to high temperature annealing in air at a temperature of 300-600° C. for 1-120 minutes to remove impurities on the substrate surface;

[0016] 3) Chemical etching: Soak the annealed substrate in an acid or alkaline solution for 30-180 seconds. The optional acids include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, etc., and the optional alkaline solutions include sodium hydroxide, potassium hydroxide, etc., to remove the oxides in the structure and obtain a pure substrate.

[0017] Beneficial effects: The present invention provides a method for cleaning a surface enhanced Raman substrate and achieving reuse. A SERS substrate containing impurities or detection molecules is taken as the object, and an oxide film layer with controllable thickness is coated on it by atomic layer deposition, and then high-temperature annealing is performed on it, and then the surface oxide is corroded by acid or alkali to expose the morphology and "hot spots" of the original substrate, so as to clean the substrate or achieve reuse. The advantages of excellent three-dimensional conformality and precise thickness control of atomic layer deposition technology are utilized to coat an ultra-thin oxide coating on the surface of a noble metal substrate, and the thickness is precisely controlled by the number of cycles. After the noble metal nanostructure is completely coated, high-temperature annealing is performed, and impurities or detection molecules on the surface of the substrate are decomposed by high temperature, and the morphology, structure and composition are not changed under the protection of the oxide film. Finally, chemical corrosion is used to remove the oxide on the surface of the substrate to obtain a pure original nanostructure substrate. Compared with the original substrate, the substrate treated by the method of the present invention has non-destructive SERS performance, high purity and reusability, effectively removes interference signals existing in the SERS substrate during actual use, improves detection sensitivity, and can be recycled, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Scanning electron microscope images of (a) initial silver dendrites, (b) silver dendrites after annealing, (c) silver dendrites @ alumina after annealing, and (d) pure silver dendrites during the treatment process in the embodiment of the present invention;

[0019] Figure 2 : is the Raman spectrum of impurities on the I-VI structure in the embodiment of the present invention, where I is the initial silver dendrite, II is the silver dendrite rinsed with deionized water several times, III is the silver dendrite centrifuged and cleaned 10 times, IV is the silver dendrite annealed at high temperature, V is the silver dendrite @ alumina annealed at high temperature, and VI is V corroded by KOH;

[0020] Figure 3 Initial silver dendrites and cleaned silver dendrites were used for the detection of rhodamine 6G (R6G) in the present invention: (a) Raman spectra and (b) peak intensity (@609 cm -1 );

[0021] Figure 4 1 is the Raman spectra of the initial silver dendrites and the cleaned silver dendrites in the embodiment of the present invention;

[0022] Figure 5 This is the effect of silver dendrites being used twice to detect R6G molecules in an embodiment of the present invention;

[0023] Figure 6 This is the Raman spectra of the gold nanoparticles before and after cleaning treatment after they are used to detect R6G molecules in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0025] Example 1

[0026] A method for cleaning a surface enhanced Raman substrate and achieving reusability, comprising the following steps:

[0027] 1) Ultrasonic cleaning of the titanium sheet was performed in acetone, isopropanol, ethanol and deionized water for 5 minutes in sequence;

[0028] 2) Deposit silver nanodendrites (denoted as I) on the titanium sheet by electrochemical deposition, such as Figure 1 (a) shows the scanning electron microscope image of the obtained silver dendrite;

[0029] 3) The initial silver dendrites were rinsed with deionized water several times, centrifuged and cleaned 10 times, and annealed at 500°C for 30 minutes (respectively marked as II, III, and IV). Figure 1 (b) is a scanning electron microscope image of silver dendrites after direct annealing;

[0030] 4) The untreated initial silver dendrite substrate was transferred to the ALD reaction chamber, and a 2 nm aluminum oxide film was deposited to form an aluminum oxide-wrapped silver dendrite structure (silver dendrite@aluminum oxide). The parameters for ALD deposition of aluminum oxide were as follows: reaction chamber temperature: 80°C; reaction source: trimethylaluminum and H2O were used to deposit aluminum oxide, and the source temperature was room temperature; pulse and cleaning time: the pulses of the metal source and the water source were both 2 s; each pulse was followed by a high-purity nitrogen gas cleaning for 8 s to wash away the reaction byproducts and residual reaction sources;

[0031] 5) The above silver dendrite@alumina structure was placed in an air environment and annealed at 500°C for 30 minutes (denoted as V). The SEM image is as follows: Figure 1 (c) as shown;

[0032] 6) The annealed silver dendrite@alumina structure was corroded with 1M KOH solution for 60 seconds to obtain pure silver dendrites (denoted as VI). Figure 1 (d) SEM image;

[0033] 7) Use Raman testing to characterize I-VI samples, such as Figure 2 As shown in the figure, many impurity peaks were measured for the electrochemically deposited silver dendrites, which were caused by the adsorption of citric acid on the surface of the silver dendrites during the formation of the silver dendrites. In order to obtain a clean substrate, the conventional cleaning methods, i.e., deionized water cleaning and centrifugal cleaning, have been proven to be ineffective. The sample after high temperature annealing showed a clean Raman signal, which proved that the contaminants on the surface of the silver dendrites were completely removed, and the same effect was also shown after KOH corrosion.

[0034] like Figure 1 (b) The results of scanning electron microscopy show that the structure of silver dendrites is destroyed after direct high-temperature annealing, and they condense from dendrites to particles; while the original morphology of silver dendrites wrapped by ALD remains unchanged after high-temperature annealing and remains unchanged after chemical corrosion.

[0035] 8) The silver dendrite samples before and after cleaning were used to characterize 10 -7 M R6G molecule, Raman spectrum Figure 3 As shown in a, the silver dendrite structure after cleaning by the method of the present invention shows a pure R6G Raman signal, while the initial silver dendrite has many more impurity peaks while detecting R6G, which will greatly affect the actual use of the silver dendrite. In addition, while obtaining a pure substrate, it does not affect its SERS performance, as shown in FIG. Figure 3 As shown in b.

[0036] Example 2

[0037] A method for cleaning a surface enhanced Raman substrate and achieving reusability, comprising the following steps:

[0038] 1) Ultrasonic cleaning of the titanium sheet was performed in acetone, isopropanol, ethanol and deionized water for 5 minutes in sequence;

[0039] 2) Deposition of silver nanodendrites on titanium sheets by electrochemical deposition;

[0040] 3) The untreated initial silver dendrite substrate was transferred to the ALD reaction chamber, and a 10 nm aluminum oxide film was deposited to form an aluminum oxide-wrapped silver dendrite structure (silver dendrite@aluminum oxide). The parameters for ALD deposition of aluminum oxide were as follows: reaction chamber temperature: 80 °C; reaction source: aluminum oxide was deposited using trimethylaluminum and H2O, and the source temperature was room temperature; pulse and cleaning time: the pulse of the metal source and the water source was 4 s; each pulse was followed by a 20 s cleaning with high-purity nitrogen to wash away the reaction byproducts and residual reaction sources;

[0041] 4) placing the silver dendrite@alumina structure in an air environment and annealing at 500 °C for 30 minutes;

[0042] 5) The annealed silver dendrite@alumina structure was etched with 1M KOH solution for 60 seconds to obtain pure silver dendrites;

[0043] 6) Use Raman testing to characterize the initial silver dendrites and the silver dendrites after cleaning, such as Figure 4 As shown, the silver dendrites obtained after treatment have no interference signals.

[0044] Example 3

[0045] A method for cleaning a surface enhanced Raman substrate and achieving reusability, comprising the following steps:

[0046] 1) Ultrasonic cleaning of the titanium sheet was performed in acetone, isopropanol, ethanol and deionized water for 5 minutes in sequence;

[0047] 2) electrochemically depositing the treated titanium sheet to grow initial silver dendrites;

[0048] 3) Soak the above silver dendrites in 10 -6 M R6G solution for 3 hours, then take it out and rinse it with deionized water and blow dry it with high-purity nitrogen. Figure 5 As shown in A, a strong Raman signal can be detected at this time;

[0049] 4) Subsequently, the silver dendrite substrate carrying R6G was transferred to the ALD reaction chamber, and 20 cycles of aluminum oxide film were deposited to form an aluminum oxide-wrapped silver dendrite structure (silver dendrite@aluminum oxide). The parameters of ALD deposition of aluminum oxide were as follows: reaction chamber temperature: 80 °C; reaction source: aluminum oxide was deposited using trimethylaluminum and H2O, and the source temperature was room temperature; pulse and cleaning time: the pulse of the metal source and the water source was 1 s; each pulse was followed by a high-purity nitrogen gas cleaning for 8 s to wash away the reaction byproducts and residual reaction sources;

[0050] 5) annealing the silver dendrite@alumina structure in an air environment at 500 °C for 30 minutes;

[0051] 6) The annealed silver dendrite@alumina structure was corroded with 1M KOH solution for 60 seconds. At this time, the signal of R6G molecules could no longer be detected. Figure 5 As shown in B, the R6G molecule was successfully removed;

[0052] 7) The above samples were soaked in the same concentration of R6G solution for 3 hours, then taken out and rinsed with deionized water, dried with high-purity nitrogen, and Raman testing was used again to detect R6G. Figure 5 As shown in C, an enhanced R6G signal was still obtained, proving that this method can make silver dendrites reusable.

[0053] Example 4

[0054] A method for cleaning a surface enhanced Raman substrate and achieving reusability, comprising the following steps:

[0055] 1) Drop the purchased gold nanoparticles on the silicon wafer and dry them before use;

[0056] 2) Soak the gold nanoparticles in -5 M R6G solution for 3 hours, then taken out, rinsed with deionized water, and dried with high-purity nitrogen;

[0057] 3) The gold nanoparticles containing R6G were transferred to the ALD reaction chamber and 40 cycles of aluminum oxide film were deposited to form an aluminum oxide-wrapped gold nanoparticle structure (gold nanoparticles@aluminum oxide). The parameters for ALD deposition of aluminum oxide were as follows: reaction chamber temperature: room temperature; reaction source: aluminum oxide was deposited using trimethylaluminum and H2O, and the source temperature was room temperature; pulse and cleaning time: the pulses of the metal source and the water source were both 5 s; each pulse was followed by a 100 s cleaning with high-purity nitrogen to wash away the reaction byproducts and residual reaction sources;

[0058] 4) placing the gold nanoparticles@alumina in an air environment and annealing at 500 °C for 30 minutes;

[0059] 5) The annealed gold nanoparticle@alumina structure was etched with 1M KOH solution for 120 seconds;

[0060] 6) Use Raman testing to characterize the signal of R6G molecules, such as Figure 6 As shown, the R6G signal no longer exists on the cleaned substrate, achieving a cleaning effect on the used SERS substrate.

[0061] Example 5

[0062] A method for cleaning a surface enhanced Raman substrate and achieving reusability, comprising the following steps:

[0063] 1) Using chemically prepared silver nanoflowers containing polyvinyl pyrrolidone (PVP) as the substrate;

[0064] 2) The untreated silver nanoflower substrate was transferred to the ALD reaction chamber, and a 10 nm aluminum oxide film was deposited to form an aluminum oxide-wrapped silver nanoflower structure (silver nanoflower@zinc oxide). The parameters for ALD deposition of zinc oxide were as follows: reaction chamber temperature: 100 °C; reaction source: diethyl zinc and H2O were used to deposit aluminum oxide, and the source temperature was room temperature; pulse and cleaning time: the pulse of the metal source and the water source was 4 s; each pulse was followed by a 20 s cleaning with high-purity nitrogen to wash away the reaction byproducts and residual reaction sources;

[0065] 4) Place the silver nanoflower@zinc oxide structure in an air environment and anneal at 300 °C for 10 minutes;

[0066] 5) The annealed silver nanoflower@alumina structure was corroded with 1M HCl solution for 180 seconds to obtain pure silver nanoflowers.

[0067] Example 6

[0068] A method for cleaning a surface enhanced Raman substrate and achieving reusability, comprising the following steps:

[0069] 1) Using gold nanoparticles with organic impurities attached prepared by solution method as substrate;

[0070] 2) The untreated gold nanoparticle substrate was transferred to the ALD reaction chamber and a 10 nm aluminum oxide film was deposited to form an aluminum oxide-wrapped gold nanoparticle structure (gold nanoparticles@aluminum oxide). The parameters for ALD deposition of aluminum oxide were:

[0071] Reaction chamber temperature: 200 °C;

[0072] Reaction source: Trimethylaluminum and H2O were used to deposit aluminum oxide, and the source temperature was room temperature;

[0073] Pulse and purge time: The pulses of the metal source and water source are both 2 s; each pulse is followed by a 30 s purge with high-purity nitrogen to flush out the reaction byproducts and residual reaction sources;

[0074] 4) placing the gold nanoparticle@alumina structure in an air environment and annealing at 600 °C for 120 minutes;

[0075] 5) The annealed gold nanoparticles@alumina structure was etched with 1M phosphoric acid solution for 180 seconds to obtain pure gold nanoparticles.

[0076] The above are only preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements made are all protected by the present invention.

Claims

1. A method for cleaning a surface enhanced Raman substrate and achieving reusability, characterized in that: The following steps are involved: 1) ALD deposition of oxide film: an oxide film with a thickness of 1-10 nm is deposited on the SERS substrate containing impurities by ALD technology to form a SERS substrate wrapped with an oxide film, wherein the oxide film is an aluminum oxide film or a zinc oxide film; 2) High temperature annealing: The SERS substrate wrapped with the oxide film obtained in step 1) is subjected to high temperature annealing in air at a temperature of 300-600°C for a time of 1-120 minutes to remove impurities on the surface of the substrate. The SERS substrate is not changed under the protection of the oxide film. 3) Chemical etching: Immerse the annealed substrate in an acid or alkaline solution to remove oxides in the structure and obtain a pure and reusable substrate.

2. The method for cleaning a surface-enhanced Raman substrate and achieving reusability according to claim 1, characterized in that: The parameters for ALD deposition of aluminum oxide are: the reaction chamber temperature is room temperature ~ 200 ° C; the reaction sources are trimethylaluminum and water; the source temperature is room temperature; the pulse and cleaning time are 1 ~ 5 s for both the metal source and the water source. After each pulse, it is immediately cleaned with high-purity nitrogen for 4 ~ 100 s to wash away the reaction by-products and residual reaction sources.

3. The method for cleaning a surface-enhanced Raman substrate and achieving reusability according to claim 1, characterized in that: The parameters for ALD deposition of zinc oxide are: the reaction chamber temperature is room temperature ~ 200 °C; the reaction sources are diethyl zinc and water; the source temperature is room temperature; the pulse and cleaning time are 1 ~ 5 s for both the metal source and the water source. After each pulse, it is immediately cleaned with high-purity nitrogen for 4 ~ 100 s to wash away the reaction by-products and residual reaction sources.

4. The method for cleaning a surface-enhanced Raman substrate and achieving reusability according to claim 1, characterized in that: In step 3), the soaking time is 30-180 seconds.

5. The method for cleaning a surface-enhanced Raman substrate and achieving reusability according to claim 1 or 4, characterized in that: The acid in step 3) is hydrochloric acid, nitric acid, sulfuric acid or phosphoric acid.

6. The method for cleaning a surface-enhanced Raman substrate and achieving reusability according to claim 1 or 4, characterized in that: The base in step 3) is sodium hydroxide or potassium hydroxide.

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