A surface-enhanced Raman substrate with high film-substrate binding force and a preparation method thereof

Abstract

The present invention discloses a surface-enhanced Raman substrate with high film-substrate binding force and a preparation method thereof, belonging to the fields of molecular recognition and nanomanufacturing. In the present invention, a metal nanostructure with nano-gaps is prepared on the surface of a solid substrate, and an oxide with a nano-scale thickness is used to wrap the metal nanostructure by atomic layer deposition, and then the sample is rolled, so as to form a dense metal-oxide planar composite structure on the substrate, improving the binding force of the metal nanomaterial on the substrate. Subsequently, the wrapped oxide is removed by chemical etching to expose the gaps originally existing between the metal nanostructures, and a high-performance SERS substrate with high film-substrate binding force can be obtained.

Description

Technical Field

[0001] The present invention belongs to the fields of molecular recognition and nano-preparation, and particularly relates to a surface-enhanced Raman substrate with high film-substrate binding force and a preparation method thereof. Background Art

[0002] Surface-enhanced Raman scattering (SERS) can increase the conventional Raman scattering signal by several orders of magnitude. The electromagnetic enhancement and chemical enhancement are two generally recognized enhancement mechanisms. Among them, the electromagnetic enhancement mechanism plays a dominant role because local surface plasmons will be generated on the surface of noble metals, which will effectively amplify the optoelectrical field in certain specific parts of the nanostructure, thus generating enhanced Raman signals. Therefore, the SERS technology can be applied to the detection of trace substances.

[0003] All along, the preparation of high-performance SERS active substrates has been a key issue in this field. Among them, gold and silver are the most common noble metals used to prepare SERS active substrates. Many researchers have constructed metal nanostructures on solid substrates, such as nanoparticles, nanodendrites, nanorods, and nanowires. However, the binding force between noble metal nanostructures and solid substrates is usually weak, which makes the noble metal nanostructures extremely easy to fall off the substrate during actual storage and use, greatly affecting the stability and service life of the SERS substrate and limiting the practical application of the SERS technology. Summary of the Invention

[0004] The present invention provides a surface-enhanced Raman substrate with high film-substrate binding force and a preparation method thereof. A dense metal-oxide planar composite structure is formed on the substrate to improve the binding force of the metal nanomaterial on the substrate, and the wrapped oxide is removed to expose the gaps originally existing between the metal nanostructures, thereby obtaining a high-performance SERS substrate with high film-substrate binding force.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A surface-enhanced Raman substrate with high film-substrate binding force is prepared by preparing metal nanostructures on a metal substrate, rinsing the sample with deionized water, drying it in high-purity nitrogen, and then using atomic layer deposition to grow a controllable-thickness oxide thin film layer to obtain an ultrathin oxide-coated silver dendrite structure. Then, the substrate is rolled densely to form a metal silver-oxide planar composite structure, and the surface oxide is etched with acid or alkali to expose the nano-gaps between the silver dendrites, thereby obtaining a planar silver dendrite thin film structure as the surface Raman enhancement substrate with high film-substrate binding force. The metal nanostructure is preferably a silver nanodendrite.

[0007] The preparation method of the above-mentioned surface-enhanced Raman substrate with high film-substrate binding force includes the following steps:

[0008] 1) Preparation of the substrate: Select a metal foil / sheet material as the substrate, preferably copper foil, nickel foil, titanium sheet, or stainless steel sheet, and ultrasonically clean it with organic solvents and deionized water until it is clean;

[0009] 2) Deposition of silver dendrites: Using the method of electrochemical deposition, with a current density of 1 - 30 mA / cm 2 , and a deposition time of 30 - 360 seconds, silver dendrites are obtained on the substrate. After rinsing with deionized water, it is dried in high-purity nitrogen;

[0010] 3) ALD deposition of oxide thin films: Transfer the above silver dendrite substrate to the ALD reaction chamber, precisely control the thickness through the number of cycles, and deposit an oxide thin film with a thickness of 1 - 10 nm, preferably alumina or zinc oxide thin films, to form a silver dendrite structure wrapped by an oxide thin film (silver dendrite@oxide);

[0011] The parameters for ALD deposition of alumina are:

[0012] Reaction chamber temperature: room temperature ~ 100 o °C;

[0013] Reaction sources: Trimethylaluminum and water are used for depositing alumina, and the source temperatures are both room temperature;

[0014] Pulse and cleaning time: The pulses of both the metal source and the water source are 1 - 5 s; after each pulse, it is immediately followed by cleaning with high-purity nitrogen for 4 - 30 s to wash away reaction by-products and residual reaction sources;

[0015] The parameters for ALD deposition of zinc oxide are:

[0016] Reaction chamber temperature: room temperature ~ 100 o °C;

[0017] Reaction sources: Diethylzinc and water are used for depositing zinc oxide, and the source temperatures are both room temperature;

[0018] Pulse and cleaning time: The pulses of both the metal source and the water source are 1 - 5 s; after each pulse, it is immediately followed by cleaning with high-purity nitrogen for 4 - 30 s to wash away reaction by-products and residual reaction sources;

[0019] 4) Rolling densification: Roll the above silver nanodendrites wrapped with oxide to transform the loose silver dendrite nanostructure into a dense silver-oxide planar composite structure (silver dendrite@oxide - rolled);

[0020] 5) Chemical etching: Immerse the above dense silver-oxide composite structure in an acid or alkali solution for 30 - 300 s to remove the oxide in the structure, exposing the nano-gaps between the silver dendrites, and obtaining a planar silver dendrite thin film structure with nano-gaps (silver dendrite@oxide - rolled - etched).

[0021] Advantageous effects: The present invention provides a surface Raman enhancement substrate with high film-substrate adhesion and a preparation method thereof. A metal nanostructure with nano-gaps (such as silver nanodendrites) is prepared on the surface of a solid substrate. By utilizing the excellent three-dimensional conformality and the advantage of precisely controlling the thickness of atomic layer deposition technology, a nano-scale thin oxide layer is uniformly coated on the surface of the silver nanodendrites, and the sample is pressed into a dense metal-oxide composite film by rolling, so as to improve the adhesion of the metal nanomaterial on the substrate. The oxide is removed by chemical etching to expose the gaps originally existing between the metal nanostructures, thereby forming a planar silver dendrite structure. This structure not only retains the nano-gap "hot spots" in the silver nanodendrite structure and has excellent Raman enhancement performance, but also after the metal nanostructures are rolled and densified, the adhesion with the substrate is greatly enhanced. This SERS substrate has good stability and effectively improves the stability and service life during transportation, storage, and detection in practical applications. Description of the Drawings

[0022] Figure 1 It is the flow chart of the preparation method in the embodiment of the present invention; A: Electrochemical deposition of silver dendrites; B: ALD coating of aluminum oxide; C: Rolling and densification; D: Chemical etching;

[0023] Figure 2 It is the scanning electron microscope pictures of (a) silver dendrites, (b) silver dendrites@aluminum oxide, (c) silver dendrites@aluminum oxide-rolled, and (d) silver dendrites@aluminum oxide-rolled-etched in the embodiment of the present invention;

[0024] Figure 3 It is that the silver dendrites@aluminum oxide-rolled structure in the embodiment of the present invention is used for the detection of methylene blue (MB) after being corroded in 1 M KOH solution for 0 - 180 seconds: (a) Raman spectra and (b) peak intensity (@1624 cm -1 ) versus corrosion time;

[0025] Figure 4 It is the comparison chart of the surface peeling force between silver dendrites and silver dendrites@aluminum oxide-rolled-etched in the embodiment of the present invention;

[0026] Figure 5 It is the photos of silver dendrites in the embodiment of the present invention before (a) and after (b) 1 minute of ultrasonic treatment;

[0027] Figure 6 It is the photos of silver dendrites@aluminum oxide-rolled-etched for 60 seconds after ultrasonic treatment for different times in the embodiment of the present invention: (a) 0, (b) 1, (c) 3, and (d) 5 minutes;

[0028] Figure 7Raman spectra of silver dendrite-rolling and silver dendrite@4 nm alumina-rolling-corrosion for 60 s on MB in the embodiments of the present invention. Detailed implementation manners

[0029] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0030] Embodiment 1

[0031] As Figure 1 shown, a preparation method of a surface Raman enhancement substrate with high film-substrate adhesion includes the following steps:

[0032] 1) Ultrasonically clean the titanium sheet with acetone, isopropanol, ethanol, and deionized water for 5 minutes respectively;

[0033] 2) Using 0.01 M silver nitrate and 0.2 M citric acid as the electrolyte, with a current density of 2 mA / cm 2 , and a deposition time of 300 s, grow silver dendrites on the treated titanium sheet, rinse with deionized water, and dry in high-purity nitrogen. As Figure 2 (a) shows the scanning electron microscope photograph of the obtained silver dendrites;

[0034] 3) Transfer the above silver dendrite substrate to the ALD reaction chamber, deposit 20 cycles to form a 2 nm alumina thin film, and form a silver dendrite structure wrapped with alumina (silver dendrite@alumina). Figure 2 (b) is its scanning electron microscope picture. The parameters for ALD deposition of alumina are:

[0035] Reaction chamber temperature: 80 o °C;

[0036] Reaction source: Trimethylaluminum and H2O are used for depositing alumina, and the source temperatures are both at room temperature;

[0037] Pulse and cleaning time: The pulses of the metal source and the water source are both 2 s; after each pulse, it is immediately followed by cleaning with high-purity nitrogen for 8 s to wash away the reaction by-products and residual reaction sources;

[0038] 4) Roll the above silver metal dendrite@alumina structure under a rolling mill to form a silver-alumina planar composite structure (silver dendrite@alumina-rolling), and its scanning electron microscope image is shown in 2(c);

[0039] 5) Corrode it with 1 M KOH solution for 0 - 180 s. Figure 2 (d) is the scanning electron microscope picture after corrosion for 60 s;

[0040] 6) Immerse the above structure in a 10 -5 M MB solution for 3 hours, rinse with deionized water, and dry with high-purity nitrogen;

[0041] 7) Use Raman testing to characterize the signal of MB molecules. As Figure 3 shown in (a), the uncorroded silver-aluminum oxide composite film structure exhibits extremely weak Raman signals because the gaps between metal nanostructures are filled with oxides, resulting in no hot spots in the silver-aluminum oxide composite film structure that can enhance Raman signals and thus no Raman enhancement effect. However, as the corrosion time increases, the Raman signal of MB rapidly increases to the maximum (0 - 60 seconds) and then slowly decreases (60 - 180 seconds); because at shorter corrosion times, the KOH solution cannot cause the complete degradation of aluminum oxide; at longer times, KOH not only corrodes all of the aluminum oxide but may also corrode the metallic silver. As Figure 3 shown in (b), the silver-aluminum oxide composite film structure has the best Raman performance after being corroded by potassium hydroxide for 60 seconds.

[0042] Example 2

[0043] As Figure 1 shown, a preparation method for a surface Raman enhancement substrate with high film-substrate binding force includes the following steps:

[0044] 1) Ultrasonically clean the titanium sheet with acetone, isopropyl alcohol, ethanol, and deionized water for 5 minutes each;

[0045] 2) Use 0.01 M silver nitrate and 0.2 M citric acid as the electrolyte, with a current density of 2 mA / cm 2 , a deposition time of 300 s, rinse with deionized water, and dry in high-purity nitrogen;

[0046] 3) Transfer the above silver dendrite substrate to the ALD reaction chamber and deposit a 2-nm aluminum oxide film to form a silver dendrite structure wrapped with aluminum oxide (silver dendrite@aluminum oxide). The parameters for ALD deposition of aluminum oxide are:

[0047] Reaction chamber temperature: 80 °C;

[0048] Reaction sources: Trimethylaluminum and H2O are used for depositing aluminum oxide, and the source temperatures are both at room temperature;

[0049] Pulse and cleaning times: The pulses of both the metal source and the water source are 2 s; after each pulse, it is immediately followed by cleaning with high-purity nitrogen for 8 s to wash away reaction by-products and residual reaction sources;

[0050] 4) Roll the above silver dendrite@aluminum oxide structure under a rolling mill to form a silver-aluminum oxide planar composite structure (silver dendrite@aluminum oxide - rolled);

[0051] 5) Etch it with 1 M KOH solution for 60 seconds to form a planar silver dendrite thin film structure (silver dendrite @ alumina - rolling - etching);

[0052] 6) Use the tape stripping method to evaluate the bonding strength between the above samples and the silver dendrites and the substrate. As Figure 4 shown, the peeling force on the surface of the pure silver dendrite structure is only about 0.8 N / cm, while the peeling force of the silver dendrite planar structure can reach about 2.4 N / cm. Compared with the pure silver dendrite structure, the bonding strength between the silver dendrite planar structure and the titanium substrate is increased by two times;

[0053] 7) Use ultrasonic cleaning to test the bonding force between the silver nanostructure and the substrate, simulating the phenomena of substrate vibration and friction in actual applications; Figure 5 Pictures of the pure silver dendrites before and after 1 minute of ultrasound are shown. It can be seen that almost all the silver nanodendrites on the surface of the titanium substrate are separated and fall off, indicating a weak bonding force with the substrate; As Figure 6 shown, the samples of silver dendrite @ alumina - rolling - etching for 60 seconds still maintain their original morphology after 1 - 5 minutes of ultrasound and do not change significantly, indicating that there is a strong bonding force between the silver dendrites and the substrate at this time.

[0054] Example 3

[0055] As Figure 1 shown, a preparation method of a surface Raman enhancement substrate with high film - substrate bonding force includes the following steps:

[0056] 1) Ultrasonically clean the titanium sheet with acetone, isopropanol, ethanol, and deionized water for 5 minutes respectively;

[0057] 2) Use 0.01 M silver nitrate and 0.2 M citric acid as the electrolyte, with a current density of 2 mA / cm 2 , a deposition time of 300 s, rinse with deionized water and dry in high - purity nitrogen;

[0058] 3) Transfer the above silver dendrite substrate to the ALD reaction chamber, deposit a 4 - nm alumina thin film to form an alumina - wrapped silver dendrite structure (silver dendrite @ alumina). The parameters for ALD deposition of alumina are:

[0059] Reaction chamber temperature: 80 °C;

[0060] Reaction source: Trimethylaluminum and H2O are used for depositing alumina, and the source temperatures are both at room temperature;

[0061] Pulse and cleaning time: The pulses of the metal source and the water source are both 2 s; After each pulse, it is immediately cleaned with high - purity nitrogen for 8 s to wash away the reaction by - products and residual reaction sources;

[0062] 4) Roll the above silver dendrite @ alumina structure under a rolling mill to form a silver-alumina planar composite structure (silver dendrite @ alumina - rolled), and in addition, directly roll pure silver nanodendrites for comparison;

[0063] 5) Corrode it with 1 M KOH solution for 60 seconds to form a planar silver dendrite thin film structure (silver dendrite @ alumina - rolled - corroded);

[0064] 6) Immerse the silver dendrite @ alumina - rolled - corroded and silver dendrite - rolled in an MB solution with a concentration of 10 -5 M for 3 hours, rinse with deionized water, and dry with high - purity nitrogen;

[0065] 7) Use Raman testing to characterize the signal of MB molecules. As Figure 7 shown, the signal of the sample with 4 nm alumina coating is much greater than that of the directly rolled silver dendrites. This is because the directly rolled silver dendrites will be transformed into a dense thin film, and there are no "hot spots" that can enhance the Raman signal, while the alumina coating can retain the nano - gaps in the silver dendrites, thus having a higher Raman signal.

[0066] Example 4

[0067] As Figure 1 shown, a preparation method of a surface Raman - enhanced substrate with high film - substrate adhesion includes the following steps:

[0068] 1) Ultrasonically clean the copper foil with acetone, isopropyl alcohol, ethanol, and deionized water for 8 minutes respectively;

[0069] 2) Use 0.02 M silver nitrate and 0.3 M citric acid as the electrolyte, with a current density of 3 mA / cm 2 , a deposition time of 180 s, rinse with deionized water, and dry in high - purity nitrogen;

[0070] 3) Transfer the above silver dendrite substrate to the ALD reaction chamber and deposit a 6 - nm zinc oxide thin film to form a zinc - oxide - coated silver dendrite structure (silver dendrite @ zinc oxide). The parameters for ALD deposition of zinc oxide are:

[0071] Reaction chamber temperature: 60 °C;

[0072] Reaction source: Diethylzinc and H2O are used for depositing zinc oxide, and the source temperatures are both at room temperature;

[0073] Pulse and cleaning time: The pulses of the metal source and the water source are both 5 s; after each pulse, it is immediately followed by cleaning with high - purity nitrogen for 25 s to wash away the reaction by - products and residual reaction sources;

[0074] 4) Roll the above silver metal dendrite @ zinc oxide structure under a rolling mill to form a silver-zinc oxide planar composite structure (silver dendrite @ zinc oxide - rolled);

[0075] 5) Corrode it with 2 M HCl solution for 80 seconds to form a planar silver dendrite thin film structure (silver dendrite @ zinc oxide - rolled - corroded).

[0076] Example 5

[0077] As Figure 1 shown, a preparation method of a surface Raman enhancement substrate with high film-substrate adhesion includes the following steps:

[0078] 1) Ultrasonically clean the nickel foil with acetone, isopropanol, ethanol, and deionized water for 10 minutes respectively.

[0079] 2) Using 0.1 M silver nitrate and 1 M citric acid as the electrolyte, with a current density of 5 mA / cm 2 , the deposition time is 200 s. After rinsing with deionized water, dry it in high-purity nitrogen.

[0080] 3) Transfer the above silver dendrite substrate to the ALD reaction chamber and deposit a 10 nm zinc oxide thin film to form a zinc oxide-wrapped silver dendrite structure (silver dendrite @ zinc oxide); The parameters for ALD deposition of zinc oxide are:

[0081] Reaction chamber temperature: room temperature 25 °C;

[0082] Reaction source: Diethylzinc and H2O are used for depositing zinc oxide, and the source temperatures are both room temperature;

[0083] Pulse and cleaning time: The pulses of the metal source and the water source are both 1 s; After each pulse, immediately clean it with high-purity nitrogen for 30 s to wash away the reaction by-products and residual reaction sources;

[0084] 4) Roll the above silver dendrite @ zinc oxide structure under a rolling mill to form a silver-zinc oxide planar composite structure (silver dendrite @ zinc oxide - rolled);

[0085] 5) Corrode it with 1 M NaOH solution for 100 seconds to form a planar silver dendrite thin film structure (silver dendrite @ zinc oxide - rolled - corroded).

[0086] Example 6

[0087] As Figure 1 shown, a preparation method of a surface Raman enhancement substrate with high film-substrate adhesion includes the following steps:

[0088] 1) Ultrasonically clean the stainless steel with acetone, isopropanol, ethanol, and deionized water for 8 minutes respectively.

[0089] 2) Using 0.1 M silver nitrate and 1 M citric acid as the electrolyte, with a current density of 10 mA / cm 2 , the deposition time was 50 s. After rinsing with deionized water, it was dried in high-purity nitrogen gas.

[0090] 3) Transfer the above silver dendrite substrate to the ALD reaction chamber and deposit a 1 nm aluminum oxide film to form a silver dendrite structure wrapped with aluminum oxide (silver dendrite@aluminum oxide); the parameters for ALD deposition of aluminum oxide are as follows:

[0091] Reaction chamber temperature: 50 °C;

[0092] Reaction sources: Trimethylaluminum and H2O were used for depositing aluminum oxide, and the source temperatures were both at room temperature;

[0093] Pulse and cleaning time: The pulses of the metal source and the water source were both 2 s; after each pulse, it was immediately cleaned with high-purity nitrogen gas for 20 s to wash away the reaction by-products and residual reaction sources;

[0094] 4) Roll the above silver dendrite@aluminum oxide structure under a rolling mill to form a silver-aluminum oxide planar composite structure (silver dendrite@aluminum oxide - rolled).

[0095] 5) Corrode it with 5% phosphoric acid for 300 s to form a planar silver dendrite thin film structure (silver dendrite@aluminum oxide - rolled - corroded).

[0096] The above are only the 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 noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements made all fall within the protection scope of the present invention.

Claims

1. A preparation method of a surface-enhanced Raman substrate with high film-substrate binding force, characterized in that, It includes the following steps: 1) Substrate preparation: Select a metal foil or sheet material as the substrate and clean it thoroughly; 2) Deposition of metal dendrites: Use the method of electrochemical deposition to obtain metal dendrites on the substrate, rinse and then dry them; 3) ALD deposition of oxide film: Use ALD to precisely control the thickness and deposit an oxide film with a thickness of 1 - 10 nm on the metal dendrites to form a metal dendrite structure wrapped by the oxide film; 4) Rolling densification: Roll the metal dendrite structure wrapped by the oxide film so that the loose metal dendrite nanostructure is transformed into a dense metal-oxide planar composite structure; 5) Chemical etching: Immerse the dense metal-oxide planar composite structure in an acid or alkali solution for 30 - 300 s to remove the oxide in the structure, expose the nano-gaps between the metal dendrites, and obtain a planar metal dendrite film structure containing nano-gaps.

2. The preparation method of the surface-enhanced Raman substrate with high film-substrate binding force according to claim 1, wherein In step 2), the current density for electrochemical deposition is 1-30 mA / cm 2 , and the deposition time is 30-360 seconds.

3. The preparation method of the surface-enhanced Raman substrate with high film-substrate binding force according to claim 1, wherein, In step 3), the oxide film is an alumina or zinc oxide film.

4. The preparation method of the surface-enhanced Raman substrate with high film-substrate binding force according to claim 3, characterized in that, The parameters for ALD deposition of alumina are: Reaction chamber temperature: room temperature ~ 100 °C; Reaction sources: Trimethylaluminum and water are used for depositing alumina, and the source temperatures are both room temperature; Pulse and cleaning time: The pulses of the metal source and the water source are both 1 - 5 s; After each pulse, it is immediately followed by purging with high-purity nitrogen for 4 - 30 s to wash away the reaction by-products and residual reaction sources.

5. The preparation method of the surface-enhanced Raman substrate with high film-substrate binding force according to claim 3, characterized in that, The parameters for ALD deposition of zinc oxide are: Reaction chamber temperature: room temperature ~ 100 °C; Reaction sources: Diethylzinc and water are used for depositing zinc oxide, and the source temperatures are both room temperature; Pulse and cleaning time: The pulses of the metal source and the water source are both 1 - 5 s; After each pulse, it is immediately followed by purging with high-purity nitrogen for 4 - 30 s to wash away the reaction by-products and residual reaction sources.

6. The surface-enhanced Raman substrate with high film-substrate binding force prepared by the method according to any one of claims 1-5, characterized in that, The substrate is a planar metal nanofilms structure, and there are nano-gaps between the planar metal nanofilms structures.

7. The surface-enhanced Raman substrate with high film-substrate binding force according to claim 6, characterized in that The planar metal nanofilms structure is a planar silver dendrite film structure.

8. The surface-enhanced Raman substrate with high film-substrate binding force according to claim 6 or 7, characterized in that, Prepare an ultrathin oxide-wrapped silver nanodendrite structure on the substrate, roll it to densify to form a metal silver-oxide planar composite structure, remove the surface oxide to expose the nano-gaps between the silver dendrites, and obtain a planar silver dendrite film structure as a surface Raman enhancement substrate with high film-substrate adhesion.

Images