Disclosure of Invention
The purpose of the invention is as follows: the invention aims to solve the defects in the prior art and provides a preparation method of an SERS substrate with an aluminum-based flower-shaped composite nano structure.
The technical scheme is as follows: the invention relates to a preparation method of an SERS substrate with an aluminum-based flower-shaped composite nano structure, which comprises the following steps:
step 1, preparing an aluminum substrate template with a highly ordered pit:
coating a thin layer of nail polish on the back of the aluminum foil to prevent the back of the aluminum foil from being oxidized, then applying direct current voltage to the aluminum foil by adopting an oxalic acid solution under the ice bath condition to carry out anodic oxidation so as to form a primary anodic oxidation layer on the aluminum foil, and removing the primary anodic oxidation layer on the aluminum foil by adopting a mixed acid solution at the water bath temperature to obtain an aluminum base template with highly ordered pits;
step 2, preparing a template with a highly ordered Ag nanoparticle array on the surface:
in AgNO3Dropwise adding a small amount of concentrated sulfuric acid into the aqueous solution to prepare electrolyte, applying alternating voltage, depositing silver nanoparticles on the aluminum base template with the highly ordered pits prepared in the step (1), placing the aluminum base template in a high-temperature tube furnace, and carrying out annealing treatment to obtain a template with a highly ordered Ag nanoparticle array on the surface;
step 3, preparing a flower-shaped composite Au/Ag nano composite array structure:
slowly dripping ascorbic acid solution into the mixed solution of chloroauric acid and sodium bromide until the color of the mixed solution is changed from bright yellow to colorless, and changing the concentration of chloroauric acid to prepare Au + solutions with different concentrations; and (3) immersing the template with the highly ordered Ag nano particle array on the surface in the step (2) into Au + solutions with different concentrations for 3min to obtain the SERS substrate with the aluminum-based flower-shaped composite nano structure.
Further, the step 1 specifically comprises: coating a thin layer of nail polish on the back of the aluminum foil to prevent the back of the aluminum foil from being oxidized, then applying 35V direct current voltage to the aluminum foil by adopting 0.3mol/L oxalic acid solution under the ice bath condition to carry out anodic oxidation for 2 hours, removing the primary anodic oxidation layer on the aluminum foil by adopting mixed acid solution at the water bath temperature of 60-70 ℃, and reacting for 2 hours to obtain the aluminum base template with the highly ordered pits.
Further, step 2 specifically comprises: at 0.5g/LAgNO3And (2) dropwise adding a small amount of concentrated sulfuric acid into the aqueous solution to prepare electrolyte, applying an alternating voltage of 5.0V, depositing silver nanoparticles on the aluminum base template with the highly ordered pits prepared in the step (1), placing the aluminum base template in a high-temperature tube furnace, and annealing to obtain the template with the highly ordered Ag nanoparticle array on the surface.
Further, in the annealing treatment, the temperature is uniformly and slowly raised to 500 ℃ under the protection of N2, and the annealing time is 4 hours.
Further, the ascorbic acid solution in the step 3 is 0.10mol/L ascorbic acid solution, the content of sodium bromide in the mixed solution is 30mmol/L, and the content of chloroauric acid in the mixed solution is 0.1-0.5 mmol/L.
Further, in the step 3, the template with the highly ordered Ag nanoparticle array on the surface is immersed in Au + solutions with different concentrations, and the reaction time is 3 min.
The invention provides a preparation method of an SERS substrate with an aluminum-based flower-shaped composite nano structure and the SERS substrate with the aluminum-based flower-shaped composite nano structure prepared by the method.
Has the advantages that: compared with the prior art, the preparation method of the SERS substrate with the aluminum-based flower-shaped composite nano structure and the SERS substrate have the following beneficial effects that:
(1) the preparation of the SERS substrate with the aluminum-based flower-shaped composite nano structure is obtained through reduction reaction of alternating current deposition and in-situ substitution, and the obtained structure is stable, ordered in arrangement and good in detection uniformity.
(2) The composite nano-structure substrate based on the highly-ordered pit aluminum substrate template not only has a flower-shaped stable and uniform structure, but also can further enhance the SERS effect through the electromagnetic coupling of gold and silver, and has the advantages of good SERS sensitivity, good repeatability, strong stability and large hot spot area.
(3) By using crystal violet as a probe molecule and analyzing and comparing SERS spectra of flower-shaped composite gold and silver nano-structures obtained by chloroauric acid solutions with different concentrations, HAuCl with the concentration of 0.25 mmol/L can be obviously seen4The aluminum-based flower-shaped composite gold-silver nano structure prepared in the solution shows higher sensitivity, and the detection limit of the substrate is that the concentration of the probe molecule crystal violet reaches 10-8mol/L。
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, a method for preparing an aluminum-based flower-like composite nanostructure SERS substrate includes the following steps:
step 1, preparing an aluminum base template with highly ordered pits;
coating a thin layer of nail polish on the back of the aluminum foil to prevent the back of the aluminum foil from being oxidized, and then applying 35V direct current voltage to the system for anodic oxidation in 0.3mol/L oxalic acid solution under the ice bath condition for 2 hours; removing the formed primary anodic oxidation layer in a mixed solution of 1.8% Chromic Acid (CA) and 6.0% Phosphoric Acid (PA) at the water bath temperature of 60-70 ℃ for 2 h; preparing an aluminum base template with highly ordered pits; this is a prerequisite for the preparation of periodic array structures;
step 2, preparing a template with a highly ordered Ag nano-particle array on the surface;
at 0.5g/L AgNO3And dropwise adding a small amount of concentrated sulfuric acid into the aqueous solution to prepare electrolyte, applying an alternating voltage of 5.0V, and depositing the silver nanoparticles on the aluminum pit template. Placing the silver-deposited template in a high-temperature tube furnace, annealing, and performing N2And under protection, uniformly and slowly raising the temperature to 500 ℃, and annealing for 4 hours to obtain the template with the highly ordered Ag nanoparticle array on the surface.
Step 3, preparing a flower-shaped composite Au/Ag nano array structure:
slowly dripping 0.10mol/L Ascorbic Acid (AA) solution into the mixed solution of chloroauric acid and sodium bromide (30 mmol/L) until the color of the mixed solution changes from bright yellow to colorless, and changing the concentration of the chloroauric acid to prepare Au + solutions with different concentrations. Immersing the annealed template into Au + solutions with different concentrations, wherein the reaction time is 3 min; and preparing the SERS substrate with the aluminum-based flower-shaped composite nano structure.
Example 1
As shown in fig. 1, the preparation of the SERS substrate with highly ordered Ag nanoparticle array on the surface comprises the following steps:
step 1, preparing an aluminum substrate template with highly ordered pits comprises the following steps: coating a thin layer of nail polish on the back surface of the aluminum foil to prevent the back surface of the aluminum foil from being oxidized, and then applying 35V direct current voltage to the system to carry out anodic oxidation for 2 hours in 0.3mol/L oxalic acid solution under the ice bath condition. The formed primary anodized layer was removed in a mixed solution of 1.8% Chromic Acid (CA) and 6.0% Phosphoric Acid (PA) at a bath temperature of 65 ℃ for a reaction time of 2 hours, as shown in FIG. 2 (a).
Step 2, the preparation of the template with the highly ordered Ag nanoparticle array on the surface comprises the following steps: at 0.5g/L AgNO3And dropwise adding a small amount of concentrated sulfuric acid into the aqueous solution to prepare electrolyte, applying an alternating voltage of 5.0V, and depositing the silver nanoparticles on the aluminum pit template. Placing the silver-deposited template in a high-temperature tube furnace, annealing, and performing N2Under protection, the temperature is uniformly and slowly raised to 500 ℃, the annealing time is 4 hours, and the template with the highly ordered Ag nanoparticle array on the surface is obtained, as shown in fig. 2 (b), in the example, the flower-shaped composite Au/Ag nanoparticle array structure can be not prepared, and the template with the highly ordered Ag nanoparticle array on the surface is directly used as the SERS substrate.
Example 2
Example 2 differs from example 1 in that additional steps are added to prepare the composite nanostructure SERS substrate, and the specific steps of preparation are as follows:
as shown in figure 1, the preparation method comprises the following specific steps:
step 1, preparing an aluminum substrate template with highly ordered pits comprises the following steps: coating a thin layer of nail polish on the back surface of the aluminum foil to prevent the back surface of the aluminum foil from being oxidized, and then applying 35V direct current voltage to the system to carry out anodic oxidation for 2 hours in 0.3mol/L oxalic acid solution under the ice bath condition. The formed primary anodized layer was removed in a mixed solution of 1.8% Chromic Acid (CA) and 6.0% Phosphoric Acid (PA) at a bath temperature of 65 ℃ for a reaction time of 2 hours, as shown in FIG. 2 (a).
Step 2, the preparation of the template with the highly ordered Ag nanoparticle array on the surface comprises the following steps: at 0.5g/L AgNO3And dropwise adding a small amount of concentrated sulfuric acid into the aqueous solution to prepare electrolyte, applying an alternating voltage of 5.0V, and depositing the silver nanoparticles on the aluminum pit template. Placing the silver-deposited template in a high-temperature tube furnace, annealing, and performing N2Under protection, the temperature is uniformly and slowly raised to 500 ℃, and the annealing time is 4h, so that the template with the highly ordered Ag nanoparticle array on the surface is obtained, as shown in figure 2 (b).
Step 3, preparing flower-shaped composite Au/Ag nanoThe rice composite array structure comprises the following steps: slowly adding 0.10mol/L Ascorbic Acid (AA) solution dropwise into chloroauric acid (0.1 mmol/L HAuCl)4) And sodium bromide (30 mmol/L) until the color of the mixed solution is changed from bright yellow to colorless Au + solution, and immersing the annealed template for 3min to obtain the SERS substrate with the aluminum-based flower-shaped composite nanostructure, as shown in FIG. 2 (c).
Example 3
Example 3 is different from example 1 in that additional steps are added to prepare a composite nanostructure SERS substrate, example 3 is different from example 2 in that chloroauric acid solutions with different concentrations are used, and the preparation steps are as follows:
as shown in figure 1, the preparation method comprises the following specific steps:
step 1, preparing an aluminum substrate template with highly ordered pits comprises the following steps: coating a thin layer of nail polish on the back surface of the aluminum foil to prevent the back surface of the aluminum foil from being oxidized, and then applying 35V direct current voltage to the system to carry out anodic oxidation for 2 hours in 0.3mol/L oxalic acid solution under the ice bath condition. The formed primary anodized layer was removed in a mixed solution of 1.8% Chromic Acid (CA) and 6.0% Phosphoric Acid (PA) at a bath temperature of 65 ℃ for a reaction time of 2 hours, as shown in FIG. 2 (a).
Step 2, the preparation of the template with the highly ordered Ag nanoparticle array on the surface comprises the following steps: at 0.5g/L AgNO3And dropwise adding a small amount of concentrated sulfuric acid into the aqueous solution to prepare electrolyte, applying an alternating voltage of 5.0V, and depositing the silver nanoparticles on the aluminum pit template. Placing the silver-deposited template in a high-temperature tube furnace, annealing, and performing N2Under protection, the temperature is uniformly and slowly raised to 500 ℃, and the annealing time is 4h, so that the template with the highly ordered Ag nanoparticle array on the surface is obtained, as shown in figure 2 (b).
Step 3, the preparation of the flower-shaped composite Au/Ag nano composite array structure comprises the following steps: 0.10M Ascorbic Acid (AA) solution was slowly added dropwise to chloroauric acid (0.25 mmol/L HAuCl)4) And sodium bromide (30 mmol/L) until the mixed solutionAnd (3) after the solution color is changed from bright yellow to colorless Au + solution, immersing the annealed template into the solution for reaction for 3min to obtain the SERS substrate with the aluminum-based flower-shaped composite nano structure, wherein the solution color is changed from bright yellow to colorless Au + solution, and the SERS substrate with the aluminum-based flower-shaped composite nano structure is shown in fig. 2 (d).
Example 4
Example 4 is different from example 1 in that additional steps are added to prepare a composite nanostructure SERS substrate, example 4 is different from examples 2 and 3 in that chloroauric acid solutions with different concentrations are used, and the preparation steps are as follows:
as shown in figure 1, the preparation method comprises the following specific steps:
step 1, the preparation of the aluminum substrate template with the highly ordered pits comprises the following steps: coating a thin layer of nail polish on the back surface of the aluminum foil to prevent the back surface of the aluminum foil from being oxidized, and then applying 35V direct current voltage to the system to carry out anodic oxidation for 2 hours in 0.3mol/L oxalic acid solution under the ice bath condition. The formed primary anodized layer was removed in a mixed solution of 1.8% Chromic Acid (CA) and 6.0% Phosphoric Acid (PA) at a bath temperature of 65 ℃ for a reaction time of 2 hours, as shown in FIG. 2 (a).
Step 2, the preparation of the template with the highly ordered Ag nanoparticle array on the surface comprises the following steps: at 0.5g/L AgNO3And dropwise adding a small amount of concentrated sulfuric acid into the aqueous solution to prepare electrolyte, applying an alternating voltage of 5.0V, and depositing the silver nanoparticles on the aluminum pit template. Placing the silver-deposited template in a high-temperature tube furnace, annealing, and performing N2Under protection, the temperature is uniformly and slowly raised to 500 ℃, and the annealing time is 4h, so that the template with the highly ordered Ag nanoparticle array on the surface is obtained, as shown in figure 2 (b).
Step 3, the preparation of the flower-shaped composite Au/Ag nano composite array structure comprises the following steps: 0.10M Ascorbic Acid (AA) solution was slowly added dropwise to chloroauric acid (0.5 mmol/L HAuCl)4) And (3) mixing the solution with sodium bromide (30 mmol/L) until the color of the mixed solution is changed from bright yellow to colorless Au + solution, and immersing the annealed template for 3min to obtain the SERS substrate with the aluminum-based flower-shaped composite nanostructure.
Test example 1: scanning by electron microscope
Scanning an electron microscope on the aluminum substrate template with the highly ordered pits, the template with the highly ordered Ag nanoparticle array on the surface, and the SERS substrate with the flower-like composite Au/Ag nano array structure obtained in examples 1 to 4 respectively to obtain characterization results shown in FIG. 2. Wherein, fig. 2 (a) an aluminum base template of highly ordered pits; (b) a template of an aluminum-based Ag nanoparticle array; (c) and (d) preparing the Au + solution from the chloroauric acid solutions with different concentrations to form different flower-shaped composite gold and silver nano structures. It can be seen that the aluminum substrate prepared in fig. 2 (a) has a periodic nano-pore structure and uniform pore size, and the remaining aluminum substrate is conductive due to the removal of the primary oxidized oxide layer, and has an average pore size of about 60 nm and an average wall thickness between two adjacent pits of about 45 nm. Fig. 2 (b) shows an array of silver nanoparticles formed by annealing a template for silver electrodeposition, the silver nanoparticles having an average diameter of about 57 nm and a distance between two adjacent silver nanoparticles of about 48 nm. As can be observed in fig. 2 (c), after the in-situ reduction reaction, the larger silver nanoparticles are decorated with many smaller gold nanoparticles, just like the nanospheres, and many gold nanoparticles are irregularly scattered around the nanospheres. The spherical nano-flower particle size in fig. 2 (d) increases with the increase of the concentration of the chloroauric acid solution in the preparation process, and the petal structure is more obvious, which shows that the gold nanoparticles generated by reduction increasingly replace the original positions of the silver nanoparticles and are further aggregated, the distance between two adjacent flower-shaped nano-spheres is also reduced to be less than 10 nm, and a hot spot is formed, which is one of the keys for generating a stronger SERS effect. It can be seen that each structure of fig. 2 shows high uniformity and stability, which indicates that the method is a reliable technical means in the field of micro-nano structure preparation.
Test example 2: applied analysis for crystal violet detection
The template with highly ordered Ag nanoparticle array on the surface prepared in example 1 and the SERS substrate with aluminum-based flower-like composite nanostructure prepared in examples 2-4 were testedAnalyzing; using the samples prepared in the respective steps as SERS active substrates, the prepared substrates were immersed in 10-6Standing for 30 min in mol/L crystal violet/ethanol solution, then slowly leaching for several times by using ultrapure water, naturally drying, and detecting the SERS activity of the sample by using a Raman instrument. Wherein the excitation wavelength of the Raman spectrum is 785 nm, and the integration time is 5 s. The characterization result of the raman spectrometer as shown in fig. 3 is obtained.
FIG. 3 shows that the concentration of crystal violet is 10-6 SERS spectra of different nanostructures in M (a) aluminum-based flower-like composite gold and silver nanostructures (0.25 mM HAuCl)4Prepared in solution); (b) aluminum-based flower-like composite gold and silver nano structure (0.1 mM HAuCl)4Prepared in solution); (c) aluminum-based flower-like composite gold and silver nano structure (0.5 mM HAuCl)4Prepared in solution); (d) a substrate of an aluminum-based Ag nanoparticle array. The SERS spectrum detected in example 1 is shown in fig. 3 (d); the SERS spectrum detected in example 2 is shown in fig. 3 (b); the SERS spectrum detected in example 3 is shown in fig. 3 (a); the SERS spectrum detected in example 4 is shown in fig. 3 (c); the SERS spectra of the flower-shaped composite gold and silver nano-structure obtained by the aluminum-based silver film obtained by the AC electrodeposition method and the chloroauric acid solution with different concentrations are analyzed and compared, and the HAuCl with the concentration of 0.25 mM can be obviously seen4The aluminum-based flower-shaped composite gold-silver nano structure prepared in the solution has higher sensitivity.
FIG. 4 is a graph comparing SERS spectra under the effect of probe molecules with different concentrations, wherein the substrate is an aluminum-based flower-shaped composite gold-silver nanostructure (0.25 mM HAuCl)4Prepared in solution), wherein the concentrations of the corresponding probe molecules are: (a) 10. the method of the present invention-6 M;(b)10-7 M;(c)10-8 M;(d)10-9 And M. It can be seen that the detection limit of the substrate can reach 10-8M (crystal violet solution).
FIG. 5 shows the results of Raman spectroscopy on the target product containing the probe molecule crystal violet at different positions on the same substrate. The concentration of the probe molecule crystal violet is 10-7M, in the examples, aluminium baseFlower-shaped composite gold and silver nano structure (0.25 mM HAuCl)4Prepared in solution) as an example, (a) a 3D surface enhanced raman spectrum with 40 probe spots randomly selected on the same substrate for SERS detection, (b) based on crystal violet 1160 cm-1A statistical plot of SERS intensity versus standard deviation of characteristic peaks.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.