CN108519365B - Surface enhanced Raman spectroscopy sensor based on electrochemical deposition and molecular imprinting and preparation method thereof - Google Patents
Surface enhanced Raman spectroscopy sensor based on electrochemical deposition and molecular imprinting and preparation method thereof Download PDFInfo
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- 238000000034 method Methods 0.000 claims abstract description 19
- 229920000344 molecularly imprinted polymer Polymers 0.000 claims abstract description 18
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- 238000001069 Raman spectroscopy Methods 0.000 claims abstract description 11
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims abstract description 9
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- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
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Abstract
The invention discloses a surface-enhanced Raman spectroscopy sensor based on electrochemical deposition and molecular imprinting and a preparation method thereof. According to the invention, based on a molecular imprinting technology, a template molecule and functional monomer aniline are electropolymerized on the surface of a GCE (glassy carbon electrode) to form molecularly imprinted polymer thin films (MIPs); then synthesizing nano silver particles AgNPs on the surface of the MIPs by adopting an electrochemical deposition method; and finally, eluting and removing template molecules to obtain the electrode sensor modified by the nano-silver-molecularly imprinted polymer film. The preparation method is simple and quick; the obtained sensor can realize rapid, sensitive and selective detection of target molecules. The invention combines the portable Raman spectrometer, and can meet the actual detection requirements of on-site, high speed and high flux.
Description
Technical Field
The invention relates to the technical field of nano material preparation and surface enhanced Raman spectroscopy detection, and particularly relates to a surface enhanced Raman spectroscopy sensor based on electrochemical deposition and molecular imprinting and a preparation method thereof.
Background
At present, the analysis and detection of target substances in actual samples still face certain challenges, because actual sample matrixes are often very complex, the structural analogs of target molecules are more, or the content of target molecules in the samples is very low, the analysis method is required to have better anti-interference capability and higher sensitivity. The Molecular Imprinting (MIT) technology takes a target molecule as a template, can specifically identify and separate the target molecule in a complex matrix, achieves the effect of effective separation and enrichment, and is widely applied to analysis and detection in the fields of environment, medicine and the like. The Surface Enhanced Raman Spectroscopy (SERS) technique is a spectroscopic technique based on the strong amplification of signals from active molecules on metal surfaces, has high sensitivity, and can acquire characteristic spectra of molecules. However, most of the current work aims at researching the influence of the morphological structure of the metal substrate on the SERS performance, and the problem of poor selectivity of the metal substrate is less researched.
Thus, combining MIT and SERS techniques provides an analytical method with both high selectivity and high sensitivity. However, most of the existing methods are to prepare nano noble metal microspheres by a sol-gel method, and then coat a molecularly imprinted polymer film on the microspheres to form a core-shell structure, so that although good detection sensitivity can be obtained, the preparation process is complex, and the problems of detection reproducibility and repeatability decrease caused by uncontrollable conditions or poor combination of imprinted polymers and noble metals exist. Researches show that the electrochemical technology can polymerize a molecularly imprinted film or deposit nano noble metal particles on the surface of an electrode, the preparation process is simple, rapid and green, and the preparation conditions are controllable.
Disclosure of Invention
Aiming at the defects of the existing analysis method in actual sample detection, the invention provides a novel surface-enhanced Raman spectroscopy sensor based on electrochemical deposition and molecular imprinting and a preparation method thereof. The nano silver-molecularly imprinted polymer electrode sensor with both specific recognition capability and SERS activity is prepared by utilizing electrochemical polymerization and electrochemical deposition technology, and has the advantages of simple preparation process, low cost, rapidness and greenness; the sensor of the invention has the advantages of both specific recognition capability and SERS enhancement capability, high detection speed and good sensitivity, and can be used for carrying out on-site in-situ detection on actual samples by combining with a portable Raman spectrometer without complex sample pretreatment.
The technical scheme of the invention is specifically introduced as follows.
A preparation method of a surface-enhanced Raman spectrum sensor based on electrochemical deposition and molecular imprinting comprises the steps of electropolymerizing a template molecule and functional monomer aniline on the surface of a glassy carbon electrode GCE based on a molecular imprinting technology to form molecularly imprinted polymer thin film MIPs; then synthesizing nano silver particles on the surfaces of the MIPs by adopting an electrochemical deposition method; and finally, eluting and removing template molecules to obtain the electrode sensor modified by the nano-silver-molecularly imprinted polymer film.
In the present invention, the template molecule is selected from any one of theophylline (ThPh), theophylline-7-acetic acid (7-TAA), caffeine and guanine (A).
The preparation method comprises the following specific steps:
(1) immersing the activated glassy carbon electrode GCE into an electropolymerization solution, and performing in-situ deposition by adopting a cyclic voltammetry method, wherein the scanning potential range is 0.0-0.8V, and the scanning speed is 50 mV.s-1Stably scanning for 15-25 circles to obtain a molecularly imprinted polymer film MIPs modified electrode; wherein: the electropolymerization liquid is obtained by mixing an o-phenylenediamine (o-Pd) ethanol solution, a template molecule aqueous solution and a HAc-NaAc buffer solution with the pH value of 5.2 according to the volume ratio of 1:1: 2; the molar concentration of the o-phenylenediamine ethanol solution is equal to that of the template molecule solution, and the molar concentration is 0.01-0.03 mol.L-1To (c) to (d);
(2) immersing a molecularly imprinted polymer film MIPs modified electrode into a solution containing 4-8 multiplied by 10-3mol·L-1Silver nitrate and 0.2 g.L-1Depositing 250-350s in a mixed solution of a surfactant sodium dodecyl sulfate under a potential of-0.2V by adopting a current-time curve method to obtain a nano silver-MIPs film modified electrode;
(3) and (3) taking a mixed solution of ethanol and acetic acid as a template molecular eluent, carrying out ultrasonic elution on the nano-silver-MIPs thin film modified electrode obtained in the step (2) for 20-40 minutes, and repeating for multiple times until an ultraviolet-visible spectrophotometer is used for detecting template-free molecules in the mixed solution, so as to obtain the nano-silver-molecularly imprinted polymer thin film modified electrode sensor.
The invention also provides a surface-enhanced Raman spectrum sensor based on electrochemical deposition and molecular imprinting, which is prepared by the preparation method.
The nano silver particles electrodeposited by the method are used as a surface enhanced Raman substrate, so that the fingerprint spectrum of the molecules to be detected can be obtained, the Raman intensity of the molecules to be detected adsorbed on the surface can be greatly improved, and the sensitivity of the sensor is further improved. The MIPs film prepared by the method can be effectively combined with the nano silver particles to form a three-dimensional sensing substrate, so that more binding sites of molecules to be detected are formed, larger surface adsorption capacity is obtained, and the selectivity of the sensor is further improved. In combination with a portable Raman spectrometer, the sensor prepared by the invention can be conveniently carried to the site for high-flux rapid in-situ detection, and the integrated and miniaturized development of the sensor is promoted. Compared with the prior art, the invention has the following beneficial effects:
the invention can detect target molecules in the mixed sample quickly, sensitively and specifically. The SERS substrate prepared by electrochemistry and molecular imprinting technology can selectively adsorb and enrich theophylline or other target molecules, and carry out in-situ detection, and is suitable for the detection of complex actual samples; by combining with a portable Raman spectrometer, the molecular imprinting sensor can complete the adsorption and enrichment functions on a sample and the Raman spectrum information acquisition within 5min, has high sensitivity and high detection speed, and is suitable for on-site and high-throughput detection.
In addition, the invention provides a general preparation method of the molecular imprinting-SERS sensor, and the template molecules are not limited to theophylline.
Drawings
FIG. 1 is a schematic diagram of a preparation process of a molecular imprinting-SERS sensor.
FIG. 2 is a cyclic voltammogram of GCE in the prepared electropolymerization solution, the scanning potential range is 0.0-0.8V, and the scanning speed is 50 mV.s-1The number of scanning turns is 20.
FIG. 3 shows the Raman spectrum (a) after elution with Ag/p-o-PD/ThPh/GCE and adsorption of theophylline (2.5X 10)-4mol·L-1) Raman spectrum (b) after 3 hours, excitation wavelength 532nm, integration time 20 s.
FIG. 4 shows adsorption of theophylline (5.0X 10) after elution with Ag/p-o-PD/ThPh/GCE-5mol·L-1) The Raman spectrum (a) after the adsorption of theophylline, theophylline-7-acetic acid and guanine (concentrations of 5.0X 10 each)-5mol·L-1) Raman spectrum (b) of the mixed solution after 3 hours, excitation wavelength 532nm, integration time 20 s.
Detailed Description
The invention provides a preparation method of a molecular imprinting-SERS sensor, and comprises application of the sensor, in particular to rapid detection of theophylline by using the sensor.
The embodiments of the invention will now be described in detail with reference to the accompanying drawings and examples:
example 1
In this embodiment, a schematic flow chart of the preparation of the theophylline molecular imprinting-SERS sensor based on the electrochemical technology is shown in fig. 1, and the preparation method includes the following steps:
(1) pretreating a glassy carbon electrode: firstly, placing GCE on chamois leather, polishing by using alumina powder with the particle size of 1.0 mu m and the particle size of 0.05 mu m in sequence, and then performing ultrasonic treatment in deionized water for 3min respectively; then, in a potassium ferricyanide solution, cyclic voltammetry scanning is carried out within a voltage range of-0.3-0.6V until a reversible and stable redox peak appears; finally, the GCE is measured at 0.1 mol.L by using a current-time curve technology-1The activation was carried out in PBS solution at pH 7.0, at an activation potential of 2.0V for 200 s.
(2) preparation of p-o-Pd/ThPh/GCE: preparing electropolymerization liquid, weighing functional monomer o-phenylenediamine (o-Pd) and template molecule theophylline (ThPh), respectively dissolving in ethanol and deionized water, dissolving and shaking to obtain a solution with a concentration of 0.01 mol.L-1Storing the o-phenylenediamine and theophylline solution at room temperature; mixing acetic acid and sodium acetate trihydrate to obtain 0.02 mol.L with pH value of 5.2-1HAc-NaAc buffer solution. And mixing the o-phenylenediamine, the theophylline and the buffer solution according to the volume ratio of 1:1:2 to obtain the electropolymerization solution. The preparation of the MIPs film modified electrode adopts an electrochemical workstation three-electrode system (Shanghai Chenghua): Ag/AgCl is used as a reference electrode, and a Pt wire electrode is used as a counter electrode. The preparation method is cyclic voltammetry, figure 2 is a cyclic voltammetry diagram of GCE in the electropolymerization liquid, and the cyclic scanning is carried out for 20 circles within the potential range of 0.0-0.8V at the scanning speed of 50 mV.s-1And obtaining the theophylline molecularly imprinted polymer membrane modified electrode (p-o-Pd/ThPh/GCE).
(3) Preparation and elution of AgNPs/p-o-Pd/ThPh/GCE: the prepared p-o-PD/ThPh/GCE was immersed in silver nitrate (5.0X 10)-3mol·L-1) And surfactant sodium dodecyl sulfate (0.2 g.L)-1) In the mixed solution, the solution is deposited for 300s at a potential of-0.2V by adopting a current-time curve method, and thenAnd reducing silver nitrate into nano silver particles to prepare the nano silver-MIPs film modified electrode (AgNPs/p-o-Pd/ThPh/GCE). After the electrodeposition process is finished, the modified electrode is immersed in an eluent, the eluent is a mixed solution of ethanol and acetic acid (ethanol: acetic acid: 9:1), and the elution is carried out by ultrasonic treatment for 30 minutes and repeated for multiple times. Monitoring the absorbance value of theophylline at 271.6nm by using an ultraviolet-visible spectrophotometer until theophylline is completely eluted. And taking out the electrode, washing with deionized water, and air-drying for later use.
Example 2
This embodiment differs from example 1 in that: in the second step, the template molecule is theophylline-7-acetic acid. Otherwise in the same manner as in example 1.
Example 3
This embodiment differs from example 1 in that: in the second step, the template molecule is guanine. Otherwise in the same manner as in example 1.
Example 4
The method for detecting the SERS spectrum of the target molecule (theophylline) by utilizing the nano-silver surface molecularly imprinted polymer comprises the following steps:
firstly, deionized water is used for preparing the solution with the concentration of 10-8～10-3mol·L-1The target molecule of theophylline is preserved at 4 ℃; and then completely eluting the AgNPs/p-o-Pd/ThPh/GCE modified electrode to remove theophylline, soaking the electrode in a theophylline solution with a corresponding concentration, adsorbing for 3 hours, and washing with deionized water after the adsorption is finished. In-situ collecting Raman enhanced spectrum of the electrode after completely eluting and removing theophylline and adsorbing 2.5 multiplied by 10 by using a portable Raman spectrometer-4mol·L-1Comparing the Raman enhanced spectra of theophylline after 3 hours, the excitation wavelength is 532nm, the integration time is 20s, and the result (figure 3) shows that the spectrogram after absorbing theophylline has obvious characteristic peak (such as 577 cm)-1,603cm-1,1145cm-1,1392cm-1Etc.); collecting SERS spectrograms of theophylline under different integration time and integration intensity, and optimizing experimental conditions; comparing the obtained SERS spectrogram with a Raman spectrogram of a solid theophylline molecule, and referring to related documents for spectrum peak attribution; under the same experimental condition, SERS spectrograms of theophylline molecules with different concentrations are collectedReading the peak intensity of the characteristic peak, researching the relation between the characteristic peak and the corresponding concentration, and realizing the SERS detection of theophylline by utilizing the nano-silver surface molecularly imprinted polymer. Monitoring the stability of the same AgNPs/p-o-Pd/ThPh/GCE modified electrode to a theophylline SERS response signal every 24h, wherein the result shows that the stability of the modified electrode is good within 8 days; the SERS response repeatability of different AgNPs/p-o-Pd/ThPh/GCE modified electrodes to theophylline is inspected, and the result shows that the relative standard deviation of response signals of the electrodes is less than 5%, and the repeatability of the modified electrodes is good.
In addition, the invention selects theophylline-7-acetic acid, guanine and other purine alkaloids with similar structures with theophylline molecules as interferents to verify the selectivity of the method. The concentration of the prepared theophylline and the concentration of the interferent are both 5.0 multiplied by 10-5mol·L-1The AgNPs/p-o-Pd/ThPh/GCE modified electrode prepared in the method is completely eluted to remove theophylline, and then is soaked in the mixed solution for adsorption, and SERS detection is carried out after adsorption for 3 hours. Compared with the SERS spectrogram for detecting theophylline solution with the same concentration (figure 4), the SERS signal of the interferent is weaker, and the characteristic peak of theophylline is clear and visible (577 cm)-1,603cm-1,1145cm-1,1392cm-1) Characteristic peak for quantitation 603cm-1The strength of the two components are respectively theophylline-7-acetic acid (513 cm)-1) And guanine (1115 cm)-1) 25 and 10 times higher. The prepared theophylline molecular imprinting-SERS sensor is good in selectivity.
Example 5
This example investigates the accuracy of SERS spectroscopy detection of theophylline using a nano-silver surface molecularly imprinted polymer:
deionized water is used for preparing the solution with the concentration of 10-8、10-7、10-6、10-5、10-4、10-3mol·L-1The method of example 4 is followed, SERS detection is carried out under the determined optimal experimental conditions, 5 times of measurement are carried out on each sample to obtain the average value of the characteristic peak intensity, a standard curve is made, a linear equation y is fitted to be 1.212x-29.543, the correlation coefficient is 0.9906, and the detection limit is 7.2 x 10-9mol·L-1(S/N＝3)。
Preparing theophylline solution samples with different concentrations, and verifying the accuracy of the result by a labeling recovery method. The samples were tested under the same experimental conditions as the standard solutions, and the corresponding concentration values were calculated from the average intensities of the characteristic peaks, thereby obtaining the recovery rates for spiking (table 1).
TABLE 1 experiment of standard recovery rate of theophylline in actual water sample
The present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents and are included in the scope of the present invention.
Claims (3)
1. A preparation method of a molecular imprinting-surface enhanced Raman spectroscopy sensor based on electrochemical technology is characterized in that firstly, based on electrochemical polymerization molecular imprinting technology, template molecules and functional monomer aniline are electropolymerized on the surface of a glassy carbon electrode GCE to form molecularly imprinted polymer thin film MIPs, wherein the template molecules are any one of theophylline, theophylline-7-acetic acid, caffeine and guanine; then depositing nano silver particles AgNPs with Raman activity on the surface of the MIPs by adopting a time-current curve method; and finally, eluting and removing template molecules to obtain the surface-enhanced Raman spectrum sensor based on the nano silver-molecularly imprinted polymer film modification.
2. The preparation method according to claim 1, comprising the following steps:
(1) immersing the activated glassy carbon electrode GCE into an electropolymerization solution, and performing in-situ deposition by adopting a cyclic voltammetry method, wherein the scanning potential range is 0.0-0.8V, and the scanning speed is 50 mV.s-1Scanning for 15-25 circles stably to obtain a molecularly imprinted polymer film MIPs modified electrode on a glassy carbon electrode GCE; wherein: the electropolymerization solution consists of an o-phenylenediamine ethanol solution, a template molecule aqueous solution and a HAc-NaAc buffer solution with the pH value of 5.2Mixing according to the volume ratio of 1:1: 2; the molar concentration of the o-phenylenediamine ethanol solution is equal to that of the template molecule solution, and the molar concentration is 0.01-0.03 mol.L-1To (c) to (d);
(2) immersing a molecularly imprinted polymer film MIPs modified electrode into a solution containing 4.0-8.0 x 10-3mol·L-1Silver nitrate and 0.2 g.L-1Depositing 250-350s in a mixed solution of a surfactant sodium dodecyl sulfate under a potential of-0.2V by adopting a time-current curve method to obtain a nano silver-MIPs film modified electrode;
(3) the volume ratio is 9: and 1, taking a mixed solution of ethanol and acetic acid as a template molecule eluent, carrying out ultrasonic elution on the nano-silver-MIPs thin film modified electrode obtained in the step 2 for 20-40 minutes, and repeating the steps for multiple times until an ultraviolet-visible spectrophotometer is used for detecting template-free molecules in the mixed solution, so as to obtain the SERS sensor based on nano-silver-molecularly imprinted polymer thin film modification.
3. A surface-enhanced raman spectroscopy sensor based on electrochemical deposition and molecular imprinting, prepared according to the preparation method of claim 1 or 2.
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