CN109752360A - Detection method of 2,4,6-trinitrotoluene - Google Patents

Abstract

The invention discloses one kind 2,4, the detection method of 6- trinitrotoluene, poly- (bisphenol-A) carbonic ester film of doping Nano silver grain is set as surface enhanced Raman scattering substrate in substrate surface first, L-cysteine molecule is grafted on into substrate surface again, and TNT molecule can with the formation Mason sea of L-cysteine specificity write from memory compound, to realize identification and enrichment of the substrate to TNT；Finally, it will be grafted in above-mentioned composite substrate with the positive charge Nano silver grain for haling very much graceful active mark molecule 4- mercaptoaniline by TNT, it forms Ag-TNT-Ag composite construction and then generates more nanoscale gaps, it is in this characteristic of fixed proportion using TNT molecular amounts and the positive charge silver particles quantity with mark molecule of absorption, the Raman signal intensity by measuring mark molecule calculates TNT concentration in sample to be tested.For the present invention in the quantitative detection to TNT, accuracy is high, low in cost, has good specific recognition capability and surface-enhanced Raman effects.

Description

Detection method of 2,4,6-trinitrotoluene

technical field

The invention belongs to the technical field of organic matter detection, and relates to a detection method for 2,4,6-trinitrotoluene.

Background technique

As the most widely used explosive at present, 2,4,6-trinitrotoluene (TNT) will produce a large amount of industrial wastewater containing TNT in the production and use process, which has the characteristics of refractory degradation, high toxicity and complex composition. Sensitive and accurate determination of TNT content in wastewater is an important guarantee to ensure its effective treatment. At present, many conventional methods such as chromatography and mass spectrometry have great limitations in the detection of TNT wastewater with concentrations below 10 ^-4 M.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for detecting 2,4,6-trinitrotoluene.

The present invention realizes through the following technical solutions:

A detection method for 2,4,6-trinitrotoluene. Firstly, a poly(bisphenol A) carbonate film doped with silver nanoparticles is arranged on the surface of a substrate as a surface-enhanced Raman scattering (SERS) substrate. The countless silver nanoparticles loaded on it are the reaction sites, and L-cysteine molecules are grafted; then the Meisenheimer complexes formed by L-cysteine molecules and TNT molecules are used to capture TNT; Finally, the positively charged silver nanoparticles with the labeled molecule 4-mercaptoaniline are adsorbed on the electron-deficient aromatic ring of the TNT molecule by electrostatic adsorption, and the number of TNT molecules and the number of positively charged silver particles with the labeled molecule are fixed Based on the characteristic of ratio, the concentration of TNT in the sample to be tested can be estimated by measuring the Raman signal intensity of the labeled molecule.

Further, the substrate is a glass substrate, a silicon substrate or an aluminum foil substrate.

Further, in the surface-enhanced Raman substrate, the mass ratio of silver nanoparticles to poly(bisphenol A) carbonate is 1:1000-1:39.4.

Further, the detection range of the TNT to be tested is 1×10 ^-8 M to 1×10 ^-12 M, and the detection limit under triple signal-to-noise ratio is 2.05×10 ^-13 M.

Further, the grafting of L-cysteine on the SERS substrate was achieved by soaking the substrate in a 1 mM L-cysteine aqueous solution for 10–12 h.

Further, the capture of the analyte 2,4,6-trinitrotoluene (TNT) was achieved by soaking the substrate after grafting L-cysteine in the TNT sample to be tested for 20-24h.

Further, the adsorption of positively charged silver nanoparticles with labeled molecule 4-mercaptoaniline to the electron-deficient aromatic ring of TNT molecule by electrostatic adsorption was performed by soaking the substrate capturing TNT molecules in the labeled molecule 4-mercaptoaniline. The positively charged silver nanoparticles were soaked in the solution for more than 12h.

Further, the positively charged silver nanoparticles with the labeled molecule 4-mercaptoaniline are prepared by mixing the positively charged silver nanoparticles solution and the 4-mercaptoaniline solution in the dark for more than 10 hours, and ensuring that the 4-mercaptoaniline is mixed after mixing. The concentration is 1.0×10 ^-4 M, and the obtained precipitate is obtained after centrifugal washing and redispersion. The positively charged silver nanoparticle solution is prepared by reducing silver nitrate with a concentration of 2.0×10 ^-3 M and excess reducing agent. have to.

Further, the poly(bisphenol A) carbonate thin film SERS substrate doped with silver nanoparticles is realized by the following steps:

(1) Dissolve poly(bisphenol A) carbonate in an organic solvent according to a certain content, add a certain content of silver nitrate, and electrospin on the substrate under the conditions of positive high pressure 13.0 ~ 15.0kv and negative high pressure -1.5kv ;

(2) using a reducing agent to reduce the electrospun substrate in step (1) to obtain the substrate,

in,

In step (1), the content of poly(bisphenol A) carbonate in the organic solvent is 14 wt%, the content of silver nitrate in the organic solvent is 0.5 wt%-5 wt%, and the spinning temperature is 30 ℃-40 ℃; the electrospinning time is 5min-10min; the organic solvent is a mixed solvent of tetrahydrofuran and dimethylformamide in a volume ratio of 6:4; in step (2), sodium borohydride is used as the reducing agent, and the concentration of the reducing agent is 1 mM-100 mM, the reduction time is 5s-10 min.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The polycarbonate/silver-silver composite surface-enhanced Raman substrate of the present invention has low cost, high sensitivity and high accuracy. At the same time, poly(bisphenol A) carbonate is used as the support material, and its stable chemical structure and excellent optical properties can ensure the maximum SERS enhancement of the supported silver particles, and the substrate material itself will not have any influence on the measurement.

(2) The particle size of silver nanoparticles can be adjusted by the reduction time, and the crisscross spatial structure of the spinning fibers further increases the number of "hot spots" and thus improves the enhancement effect. In addition, the substrate has a high specific surface area, which can provide more adsorption sites for the molecules to be tested, without causing any interference to the measurement, with good repeatability and controllable process.

(3) The introduction of positively charged silver nanoparticles with labeled molecules can not only form an Ag-TNT-Ag composite structure with the TNT to be tested in the middle with the original silver particles to enhance the SERS signal, but also make the number of labeled molecules and the number of TNTs A fixed linear relationship was formed, which was used as the basis for quantitative detection of TNT.

Description of drawings

Figure 1 is a schematic diagram of the preparation of the polycarbonate/Ag-Ag composite surface-enhanced Raman substrate.

Figure 2 is the scanning electron microscope pictures before and after in-situ chemical reduction of the polycarbonate/Ag surface-enhanced Raman substrate prepared in Example 1 (a. before reduction; b. after reduction).

Figure 3 is a scanning electron microscope image of the composite substrate under different TNT concentrations. (a. No TNT; b. ^10-11 M TNT; c. ^10-9 M TNT; d. ^10-7 M TNT).

FIG. 4 is a standard curve diagram of the relationship between the concentration of TNT and the intensity of the Raman peak at 1436 cm ^-1 of the labeled molecule 4-mercaptoaniline.

Detailed ways

The present invention will be further described below with reference to specific embodiments and accompanying drawings, but should not be construed as limiting the protection scope of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art according to the above-mentioned contents of the present invention should be covered within the protection scope of the present invention.

In the invention, a poly(bisphenol A) carbonate nanofiber membrane containing silver nitrate is electrospun on the surface of the substrate, and then a layer of silver nanoparticles with uniform particle size and dense arrangement is prepared on the surface thereof through chemical reduction; L-cysteine captures the analyte 2,4,6-trinitrotoluene (TNT), and finally relies on electrostatic interaction to adsorb positively charged silver particles with labeled molecule 4-mercaptoaniline on TNT to form polycarbonate Ester/Ag-TNT-Ag composite structure. Since the number of TNT molecules is proportional to the number of positively charged silver particles with labeled molecules adsorbed, the concentration of TNT in the sample to be tested can be estimated by measuring the Raman signal intensity of the labeled molecules. The substrate has good surface-enhanced Raman effect and specific recognition ability for TNT, and can effectively measure trace amounts of TNT molecules down to the order of 10 ^-13 M.

As shown in Figure 1, nanofibers were prepared by electrospinning from poly(bisphenol A) carbonate solution doped with silver nitrate (step a). After reduction with sodium borohydride, a large number of uniform and fine silver nanoparticles appeared on the surface of the fibers. (step b). Due to the intricate three-dimensional structure of the spun fibers, sufficient nanogaps (i.e., Raman "hot spots") are formed between these nanosilver particles. Then, using these silver particles as reaction sites, L-cysteine was grafted on it by soaking treatment, and then the substrate was soaked in the TNT solution to be tested to make L-cysteine react with TNT to realize the substrate to TNT Molecular specific adsorption (step d); finally, the positively charged silver particles with the label are adsorbed on the TNT molecule through electrostatic interaction, and finally the Ag-TNT-Ag composite structure is formed on the spinning fiber (step c). This is used for SERS measurements.

Example 1

This embodiment discloses a method for preparing a polycarbonate/silver composite surface-enhanced Raman substrate by combining electrospinning and in-situ chemical reduction technology, which specifically includes the following steps:

(1) Poly(bisphenol A) carbonate particles and silver nitrate were dissolved in a mixed solvent of tetrahydrofuran and dimethylformamide (volume ratio 6:4) according to the mass fraction of 14 wt% and 4.5 wt%, respectively, to prepare a polymer solution;

(2) Fix the aluminum foil on the receiving device of the electrospinning machine, put the polymer solution into the syringe and place it on the injection table, adjust the positive high pressure to 15.0kv, the negative high pressure to -1.5kv, and the injection speed of 0.5 ml/L , the experimental temperature was 30 °C, the humidity was 20%, and the spinning time was 5 min to obtain polycarbonate nanofibers containing silver nitrate;

(3) The nanofibers obtained in step (2) were placed in a ₁₀ mM NaBH solution for 25 s to obtain a polycarbonate/silver composite surface-enhanced Raman substrate.

The SEM photo of the polycarbonate nanofibers containing silver nitrate prepared above is shown in Figure 2. It can be seen that the surface of the spinning fibers is relatively smooth before chemically reducing the fiber membrane (Figure 2a). After in-situ chemical reduction, uniform and compact silver nanoparticles appeared on the surface of the spinning membrane (Fig. 2b).

Example 2

This embodiment discloses a method for preparing a polycarbonate/Ag-Ag composite surface-enhanced Raman substrate by combining electrospinning, in-situ chemical reduction and chemical modification techniques (as shown in Figure 1), which specifically includes the following steps:

(1) Poly(bisphenol A) carbonate particles and silver nitrate were dissolved in a mixed solvent of tetrahydrofuran and dimethylformamide according to the mass fraction of 14 wt% and 2.3 wt%, respectively (volume ratio 6:4) to prepare a polymer solution;

(2) Fix the aluminum foil on the receiving device of the electrospinning machine, put the polymer solution into the syringe and place it on the injection table, adjust the positive high pressure to 14.0kv, the negative high pressure to -1.5kv, and the injection speed of 0.6 ml/L , the experimental temperature was 40 °C, the humidity was 25%, and the spinning time was 10 min to obtain polycarbonate nanofibers containing silver nitrate;

(3) The nanofibers obtained in step (2) were placed in a 20 mM sodium borohydride solution for 10 s to obtain a polycarbonate/Ag composite surface-enhanced Raman substrate.

(4) Add 0.034 g of silver nitrate to 100 ml of 0.4 M ammonia water, then add 0.018 g of cetyltrimethylammonium bromide, and add this solution dropwise to 100 ml of 0.03 g of sodium borohydride and 0.018 g of sodium borohydride. The mixed solution of cetyltrimethylammonium bromide was stirred under an ice-water bath for 4 hours. After the reaction was completed, the solution was heated to remove residual ammonia and decompose excess sodium borohydride; then the labeled molecule 4-mercaptoaniline was added to make the concentration reach 1.0×10 ^-4 M, stirred in the dark for 10 hours, and centrifuged at 12,000 rpm for 10 minutes to remove excess 4-mercaptoaniline molecule, washed three times with high-purity water.

(5) Immerse the polycarbonate/Ag composite substrate obtained in step (3) in L-cysteine at a concentration of 1 mM for 10 hours to form an L-cysteine monolayer on the surface; wash After drying, it was immersed in a known concentration of TNT standard solution for 24 hours. At this time, the TNT molecules in the solution would specifically combine with L-cysteine to form a Messenheimer complex; finally, the substrate was immersed in the step ( 4) The 4-mercaptoaniline-labeled positively charged silver particle solution was placed in the solution for 12 hours. After cleaning and drying, Raman measurement was carried out. The scanning electron microscope results are shown in Figure 3. It can be seen that with the increase of TNT concentration, spinning The positively charged silver nanoparticles adsorbed on the fibers gradually increased, and aggregated on the surface and joints of the spinning fibers, resulting in a rougher morphology and more nanoscale gaps (Raman "hot spots").

(6) Take the Raman peak intensity at 1436 cm ^-1 , the strongest Raman peak in the Raman spectra of TNT standard samples with different concentrations obtained in step (5), as the ordinate, and the TNT concentration as the abscissa, make a standard curve, and obtain a linear equation with the correlation coefficient (Figure 4, error bars are 5 measurements).

(7) Repeat step (5), wherein the known concentration of TNT solution is replaced with the unknown concentration of TNT to be tested. The SERS spectrum shows that the Raman peak intensity at 1436 cm ^-1 is 7621.5. Putting it into the standard equation y = 1871.3x+24445, the concentration of the TNT water sample to be tested can be obtained as 1.023×10 ^-9 M.

Claims (10)

1. The detection method of 2,4,6-trinitrotoluene is characterized in that, firstly, a poly(bisphenol A) carbonate film doped with silver nanoparticles is arranged on the surface of the substrate as a surface-enhanced Raman scattering substrate. The loaded nano-silver particles are the reaction sites, and the L-cysteine molecule is grafted; the L-cysteine molecule and the 2,4,6-trinitrotoluene molecule to be tested are then used to form a Messenheimer complex The 2,4,6-trinitrotoluene was captured; finally, the positively charged silver nanoparticles with the labeled molecule 4-mercaptoaniline were adsorbed to the electron-deficient 2,4,6-trinitrotoluene molecule by electrostatic adsorption. On the aromatic ring, using the characteristic that the number of 2,4,6-trinitrotoluene molecules is in a fixed ratio to the number of positively charged silver particles with labeled molecules adsorbed, the Raman signal intensity of the labeled molecules is used to estimate the concentration of the sample to be tested. The concentration of 2,4,6-trinitrotoluene. 2 . The detection method according to claim 1 , wherein the detection is used for quantitative detection of trace 2,4,6-trinitrotoluene in water. 3 . 3. The detection method according to claim 1, wherein the substrate is a glass substrate, a silicon substrate or an aluminum foil substrate. 4 . The detection method according to claim 1 , wherein, in the surface-enhanced Raman substrate, the mass ratio of silver nanoparticles to poly(bisphenol A) carbonate is 1:1000-1:39.4. 5 . 5. The detection method according to claim 1, wherein the detection range of the 2,4,6-trinitrotoluene to be tested is 1× ^10-8 M～1× ^10-12 M, and the signal-to-noise is tripled The detection limit under the ratio was 2.05×10 ⁻¹³ M. 6. The detection method according to claim 1, wherein the grafting of L-cysteine on the surface-enhanced Raman scattering substrate is performed by soaking the substrate in a 1 mM L-cysteine aqueous solution for 10~ 12h achieved. 7. detection method as claimed in claim 1, is characterized in that, to be tested 2,4,6-trinitrotoluene is captured by the substrate after grafting L-cysteine to be tested 2, 4,6-trinitrotoluene samples were soaked for 20~24h. 8. The detection method according to claim 1, wherein the positively charged silver nanoparticles with the labeling molecule 4-mercaptoaniline are adsorbed to the deficiency of the 2,4,6-trinitrotoluene molecule by electrostatic adsorption. Electron aromatic ring was achieved by soaking the substrate capturing 2,4,6-trinitrotoluene molecules in a solution of positively charged silver nanoparticles with labeled molecule 4-mercaptoaniline for more than 12h. 9. detection method as claimed in claim 7, is characterized in that, described positively charged silver nanoparticle with label molecule 4-mercaptoaniline is by mixing positively charged silver nanoparticle solution and 4-mercaptoaniline solution lucifuge Stir for more than 10 hours, and ensure that the concentration of 4-mercaptoaniline after mixing is 1.0 × 10 ^-4 M, and the obtained precipitate is obtained after centrifugal washing and redispersion, wherein the positively charged silver nanoparticle solution is a solution with a concentration of 2.0 × 10 ^-3 M It is obtained by reduction reaction of silver nitrate and excess reducing agent. 10 . The detection method of claim 1 , wherein the poly(bisphenol A) carbonate film SERS substrate doped with silver nanoparticles is realized by the following steps: 11 . (1) Dissolve poly(bisphenol A) carbonate in an organic solvent according to a certain content, add a certain content of silver nitrate, and electrospin on the substrate under the conditions of positive high pressure 13.0 ~ 15.0kv and negative high pressure -1.5kv ; (2) Using a reducing agent to reduce the electrospun substrate in step (1) to obtain the substrate.