Preparation of a super-sensitive fluorescence probe for detecting cadmium ions and application thereof

Abstract

The application discloses a kind of super-sensitive detection Cd 2+ The preparation and application of fluorescent probe aim to solve the problems of complicated synthesis steps, selectivity, long response time and high detection limit of existing fluorescent probes for recognizing Cd 2+ Ions. The two fluorescent probes are prepared by mild Schiff base reaction. The preparation method of fluorescent probe 1 (HMH) is as follows: 2,6-diformyl-4-methyl phenol is reacted with salicylic hydrazide to obtain the fluorescent probe 1 (HMH). The preparation method of fluorescent probe 2 (H3-MB) is as follows: the fluorescent probe 2 (H3-MB) is obtained by further reacting 6-amino-1-hexanol with the fluorescent probe 1 (HMH). The two probes of the application have the advantages of simple synthesis, low cost, and can realize sensing detection of Cd 2+ Ions, and have the advantages of low detection limit, fast response time, good selectivity, and the fluorescent probe 2 (H3-MB) can also realize visual discrimination of Cd 2+ And Zn 2+ Ions.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent probes and heavy metal detection technology, and relates to an ultrasensitive method for detecting cadmium ions (Cd). 2 + Preparation method of fluorescent probe. Background Technology

[0002] Due to its strong chemical reactivity, mobility, and irreversible toxicity, cadmium is listed as a heavy metal pollutant by the World Health Organization. With industrial development, environmental problems caused by water, soil, and crop pollution from industries such as metallurgy, electroplating, lead-zinc mining, and ceramics have attracted global attention. Cadmium is not an essential element for the human body; once absorbed, it accumulates in bones and kidneys through the food chain, ultimately leading to various diseases and endangering human health. Therefore, there is an urgent need for rapid, sensitive, and selective cadmium detection technologies, which are crucial for accurately remediating polluted water environments and reducing the health risks associated with heavy metal pollution.

[0003] Currently, traditional methods for detecting heavy metals include atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma atomic absorption spectrometry (ICP), high-performance liquid chromatography (HPLC), mass spectrometry (MS), electrochemical methods, and colorimetric methods. While these techniques can provide relatively accurate quantitative analysis, their high cost, complex operation, and high detection limits hinder their widespread application. Fluorescence detection technology, however, demonstrates significant advantages due to its high selectivity, high sensitivity, and ease of operation. (The last sentence appears to be incomplete and possibly refers to a specific method for detecting heavy metals, "Cd," which seems unrelated and possibly a separate point.) 2+ and Zn 2+ The similar electronic configurations, coordination numbers, and chemical properties make them difficult to distinguish. Prior to this, several methods for detecting Cd had been developed. 2+ Fluorescent probes have been reported, but currently developed fluorescent probes still suffer from high preparation costs, high detection limits, and poor selectivity. Therefore, developing fluorescent probes that are simple to prepare, have low detection limits, and good selectivity is of great significance. Summary of the Invention

[0004] The purpose of this invention is to solve the existing problems in identifying Cd. 2+ To address the problems of cumbersome probe synthesis steps, low selectivity, long response time, and high detection limits, this paper proposes an ultrasensitive method for detecting Cd. 2+ Fluorescent probes and their preparation methods.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A highly sensitive fluorescent probe for detecting cadmium ions has the following structural formula:

[0007] ,

[0008] When R = -CHO, the fluorescent probe is named HMH;

[0009] When R = -C = N-(CH2)OH, the fluorescent probe is named H3-MB.

[0010] The preparation methods for the two fluorescent probes mentioned above are as follows:

[0011] 1. Fluorescent probe 1 (HMH)

[0012] Preparation reaction formula:

[0013]

[0014] Preparation method: 2,6-Dicarboxy-4-methylphenol and salicylhydrazide were dissolved in ethanol and heated under reflux at 60-100 °C for 6-24 h. The reaction was monitored using a TCL plate. After complete reaction, the mixture was cooled to room temperature and the precipitate was filtered. The collected supernatant was dried using a rotary evaporator to obtain the crude product, which was then purified by column chromatography with PE:EA = 5:1-100:1 as the eluent. Drying yielded the target compound HMH.

[0015] The molar ratio of 2,6-dicarboxy-4-methylphenol to salicylhydrazine is 1:1 to 1:3.

[0016] Structural characterization of HMH: 1 H NMR (400 MHz, DMSO- d 6) δ 12.35 (s, 1H), 11.95 (s,2H), 10.37 (s,1H), 8.68 (s, 1H), 7.88 (d, J = 7.8 Hz, 1H), 7.70 (s, 1H), 7.59(s, 1H), 7.47 (t, J = 7.8 Hz, 1H), 7.00 (d, J = 8.2 Hz, 1H), 6.97 (d, J = 7.5 Hz, 1H), 2.32 (s, 3H). 13C NMR (101 MHz, DMSO-d6) δ 190.37, 164.51, 158.83, 158.54,148.22, 136.77, 134.10, 130.49, 128.77, 128.52,122.93, 119.90, 119.09,117.28, 115.67, 19.69. ESI-MS (m / z): Calcd: 298.30. Found: 299.1680 [M + H] + 321.1533 [M+Na] + .

[0017] 2. Fluorescent probe 2 (H3-MB)

[0018] Preparation reaction formula:

[0019]

[0020] Preparation method: A mixture of compound HMH and 6-amino-1-hexanol was dissolved in ethanol and heated under reflux at 60-100 °C for 6-24 h. The reaction was monitored using a TCL plate. After the reaction was complete, the mixture was cooled to room temperature and the crude product was obtained by rotary evaporation. The crude product was then purified by silica gel chromatography with DCM:MeOH = 2:1-100:1 as the eluent. The product was dried to obtain the target compound H3-MB.

[0021] The molar ratio of compound HMH to 6-amino-1-hexanol is 1:1 to 1:5.

[0022] Structural characterization of H3-MB: 1 H NMR (400 MHz, DMSO-d6) δ 11.98 (s, 1H), 8.65 (s,1H), 8.56 (s, 1H), 7.93 (d, J = 8.0 Hz, 1H), 7.77 (d, J = 7.7 Hz, 1H), 7.58(d, J = 17.6 Hz, 1H), 7.23 (t, J = 7.4Hz, 1H), 6.81 (d, J = 8.1 Hz, 1H), 6.72(t, J = 7.5 Hz, 1H), 4.38 (s, 1H), 3.65 – 3.59 (m, 2H), 3.38 (s, 2H), 2.19(s,3H), 1.47 – 1.40 (m, 4H), 1.35 – 1.30 (m, 4H). 13 C NMR (101 MHz, DMSO-D 6) δ170.23, 168.19, 159.96, 150.43, 142.89,136.04, 132.75, 131.21, 128.74,123.80, 122.78, 118.52, 116.41, 114.80, 63.99, 60.39, 32.21, 32.09, 28.88,24.97, 19.29. ESI-MS (m / z): Calcd: 397.48. Found:398.1506 [M + H] + .

[0023] Another objective of this invention is to disclose the application of the two fluorescent probes mentioned above in the detection of cadmium ions. HMH is a fluorescence-on-sensor probe, and H3-MB is a fluorescence ratiometric probe. The detection limit of HMH is 2.78 ppb, and the response time is 1 min. The detection limit of H3-MB is 0.30 ppb, and the response time is 30 s. The sensing detection includes fluorescence spectroscopy detection, selective detection, and time-response detection. H3-MB can also visually distinguish Cd ions by changes in fluorescence spectral intensity and shift. 2+ and Zn 2 + .

[0024] The beneficial effects of this invention are as follows:

[0025] 1) The probes described in this invention are simple to synthesize, the raw materials are economical and readily available, and the post-processing is relatively simple. The HMH probe only requires one step, and the H3-MB probe only requires two steps.

[0026] 2) The fluorescent probes prepared in this invention can all achieve low concentrations of Cd. 2+ The detection methods are effective, exhibiting good selectivity, low detection limits, and fast response times. The detection limit for HMH is 2.78 ppb, with a response time of 1 min. The detection limit for H3-MB is 0.30 ppb, with a response time of 30 s.

[0027] 3) The fluorescent probe H3-MB prepared in this invention can distinguish Cd by the intensity and shift of the fluorescence spectrum. 2+ and Zn 2+ This is to enable the probe to detect Cd. 2+ and Zn 2+ It is an important means of distinguishing between the two in the process.

[0028] Therefore, this invention provides a simple, rapid, ultrasensitive, and selective method for the determination of Cd. 2+ Fluorescent probes, through further functionalization, hold promise for practical applications. Attached Figure Description

[0029] Figure 1 The probe HMH is used to detect Cd in different solvents. 2+ Fluorescence change graph (concentration of 500 ppb).

[0030] Figure 2 It is the selectivity of the probe HMH for different ions in ethanol.

[0031] Figure 3 The probe HMH in ethanol is for Cd 2+ Time response plots for concentrations of 100 ppb and 50 ppb.

[0032] Figure 4 The probe HMH is used to detect different concentrations of Cd in ethanol. 2+ The fluorescence spectrum response diagram.

[0033] Figure 5 The probe HMH is used to detect different concentrations of Cd in ethanol. 2+ The linear fit plot.

[0034] Figure 6 The probe H3-MB is used to detect Cd in different solvents. 2+ Fluorescence change graph (concentration of 200 ppb).

[0035] Figure 7 It is the selectivity of the probe H3-MB for different ions in acetonitrile.

[0036] Figure 8 The probe H3-MB in acetonitrile for Cd 2+ Time response plot (concentration of 200 ppb).

[0037] Figure 9 The probe H3-MB in acetonitrile for different concentrations of Cd 2+ The fluorescence spectrum response diagram.

[0038] Figure 10 The probe H3-MB in acetonitrile for different concentrations of Cd 2+ The linear fit plot.

[0039] Figure 11 The probe H3-MB in acetonitrile for Cd 2+ (Concentration of 200 ppb) and Zn 2+ Fluorescence response spectrum (at a concentration of 1 ppm).

[0040] Figure 12 The probe H3-MB was added to acetonitrile with Cd. 2+ and Zn 2+ Fluorescence emission pattern under ultraviolet light. Detailed Implementation

[0041] The present invention will be further explained and described below with reference to specific embodiments.

[0042] Example 1

[0043] 2,6-Dicarboxy-4-methylphenol (0.1640 g, 1.0 mmol) and salicylhydrazine (0.1560 g, 1.0 mmol) were dissolved in ethanol and heated to reflux at 80 °C for 6 h. The reaction was monitored using a TCL plate. After complete reaction, the mixture was cooled to room temperature and the precipitate was filtered. The collected supernatant was dried using a rotary evaporator to obtain the crude product, which was then purified by column chromatography with PE:EA = 10:1 as the eluent. Drying yielded the target compound HMH in 94% of the product.

[0044] Example 2

[0045] A mixture of compound HMH (0.0298 g, 0.1 mmol) and 6-amino-1-hexanol (0.0117 g, 0.1 mmol) was dissolved in ethanol and heated under reflux at 85 °C for 8 h. The reaction was monitored using a TCL plate. After the reaction was complete, the mixture was cooled to room temperature and the crude product was obtained by rotary evaporation. The crude product was then purified by silica gel chromatography with DCM:MeOH = 5:1 as the eluent. After drying, the target compound H3-MB was obtained in 65% yield.

[0046] Investigation of fluorescent probe performance

[0047] The fluorescent probes HMH and H3-MB synthesized in Examples 1 and 2 were dissolved in DMSO to prepare stock solutions with a concentration of 5 mM. 0.0102 g of CdCl2·2.5H2O solid powder was dissolved in 5 mL of deionized water to prepare a 1000 ppm CdCl2 solution. 2+ The stock solution was prepared by dissolving other metal ions separately in deionized water to prepare stock solutions of 1000 ppm, which were then stored at 4°C.

[0048] 1. Fluorescent probe HMH

[0049] 1) The probe HMH synthesized in Example 1 was dissolved in methanol (MeOH), acetonitrile (ACN), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), ethyl acetate (EA), tetrahydrofuran (THF), acetone (AC), dichloromethane (DCM), 1,4-dioxane, water (H2O), and ethanol (EtOH) to prepare a solution with a concentration of 5 × 10⁻⁶. -6 mol / L. When 500 ppb Cd is added 2+Subsequently, the fluorescence intensity changes of the probe HMH in different solvents are as follows: Figure 1 At an excitation wavelength of 430 nm, the fluorescence intensity change at the maximum emission wavelength of 540 nm was most pronounced in ethanol solvent. Therefore, ethanol was used as the solvent in subsequent tests.

[0050] 2) To determine the effect of HMH on Cd 2+ To improve selectivity, other common ions, including Na+, were added at a concentration of 1 ppm to a 5 μM HMH ethanol solution. + K + Ag + Al 3+ Mn 2+ Co 2+ Ni 2+ ,ClO - .like Figure 2 As shown, when 500 ppb Cd is added... 2+ Subsequently, the fluorescence at the maximum fluorescence emission peak was significantly enhanced, accompanied by a blue shift of the wavelength to 499 nm. While the addition of other ions caused changes in fluorescence, it did not affect the fluorescence of Cd. 2+ The changes are relatively small, so the addition of other ions can be ignored.

[0051] 3) Fluorescent probe HMH in the testing of Cd 2+ In the process, response time is not only a significant factor affecting detection conditions, but also an important parameter for evaluating the probe's performance. For example... Figure 3 As shown, when 100 ppb of Cd is added... 2+ When the fluorescence intensity of the probe HMH reaches equilibrium within 3 minutes, the fluorescence intensity is similar to that of HMH. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) 2+ Subsequently, the fluorescence intensity of HMH reaches equilibrium within 1 minute. To ensure the reliability of the detection conditions, the response time in subsequent tests is 3 minutes.

[0052] 4) To determine the sensitivity of the fluorescent probe HMH, 5-50 ppb of Cd was continuously added to a 5 μM HMH ethanol solution. 2+ ,like Figure 4 As shown, the fluorescence intensity continuously increases and is accompanied by a slight blue shift. Figure 5 The fluorescence intensity of the HMH probe and low concentrations of Cd were established. 2+ The standard working curve for the ion, obtained by linear fitting, is y = 819.27 + 6.49*x, with a correlation coefficient R. 2=0.99. According to the formula for the lowest detection limit LOD = 3σ / S (where S is the slope of the calibration curve and σ is the standard deviation of the intercept), the LOD is calculated to be 2.78 ppb, and the actual concentration can reach 5.00 ppb, thus realizing the quantitative detection of Cd2+.

[0053] 2. Fluorescent probe H3-MB

[0054] 1) The probe H3-MB synthesized in Example 2 was dissolved in MeOH, ACN, DMSO, DMF, EA, THF, AC, DCM, 1,4-Dioxane, H2O, and EtOH solvents to prepare a solution with a concentration of 5 × 10⁻⁶. -6 mol / L. When 200 ppb Cd is added 2+ Subsequently, the fluorescence intensity changes of the probe HMH in different solvents are as follows: Figure 6 The fluorescence intensity change at the maximum emission wavelength of 552 nm, when the probe is excited at 410 nm, is most pronounced in acetonitrile solvent. Therefore, acetonitrile was used as the solvent in subsequent tests.

[0055] 2) To determine the effect of H3-MB on Cd 2+ The selectivity was assessed by adding other common ions, including Na+, at a concentration of 1 ppm to a 5 μM H3-MB acetonitrile solution. + K + ,ClO - Cu 2+ Co 2+ Ni 2+ NO3 - SO4 2- HCO3 2- .like Figure 7 As shown, when 200 ppb Cd is added... 2+ Subsequently, the fluorescence intensity at the maximum fluorescence emission peak of 552 nm decreased, while the emission peak intensity at 498 nm significantly increased. Although the addition of other ions alters the fluorescence, it does not affect the fluorescence intensity of Cd. 2+ The changes are relatively small, so the addition of other ions can be ignored.

[0056] 3) To determine the effectiveness of the fluorescent probe H3-MB in testing Cd 2+ Response time during the process, such as Figure 8 As shown, when 200 ppb Cd is added 2+ The fluorescence intensity of probe H3-MB reached equilibrium within 30 seconds. Compared to probe HMH, this probe improved the response time by 6 times. Therefore, a response time of 30 seconds was used in subsequent tests.

[0057] 4) To evaluate the sensitivity of the fluorescent probe H3-MB, 5-40 ppb of Cd was continuously added to a 5 μM HMH acetonitrile solution. 2+ ,like Figure 9 As shown, with Cd 2+ As the concentration increases, the intensity of the emission peak at 552 nm gradually decreases, while the intensity of the emission peak at 498 nm continuously increases. Figure 10 The emission peak ratio of the H3-MB probe at 498 nm and 552 nm was established in relation to low concentrations of Cd. 2+ The standard working curve. The equation obtained by linear fitting is y = 0.2314 + 0.3182*x, and the correlation coefficient R is... 2 =0.995. According to the formula for the lowest detection limit LOD = 3σ / S (where S is the slope of the calibration curve and σ is the standard deviation of the intercept), the LOD is calculated to be 0.30 ppb, which is 9 times higher than that of the probe HMH. Therefore, this probe has high sensitivity.

[0058] 5) Due to Cd 2+ and Zn 2+ Given their similar electronic configurations, coordination numbers, and chemical properties, it is necessary to investigate the selectivity of the fluorescent probe H3-MB. Figure 11 As shown, to detect changes in fluorescence signal, 200 ppb Cd was added respectively. 2+ and 1ppm Zn 2+ Experimental results show that Zn 2+ and Cd 2+ Both will enhance fluorescence, but Cd 2+ This makes the fluorescence enhancement more pronounced, and the emission peak positions of the two differ by 5 nm. Furthermore, Figure 12 To add 1 ppm Cd to a 25 μM probe solution 2+ and Zn 2+ The fluorescence color change under 365nm UV light was then observed. The graph shows that H3-MB initially fluoresces yellow; however, the fluorescence color changes when Cd is added. 2+ The fluorescence color then turned green, and with the addition of Zn... 2+ The fluorescence color then changes to blue-green, so this method can be used to visually distinguish Zn. 2+ and Cd 2 + .

[0059] Based on the excellent performance of the fluorescent probes HMH and H3-MB, it is expected to be used for quantitative detection and sieving of cadmium ions in complex solvent systems, and their practicality is good.

Claims

1. A fluorescent probe for ultrasensitive detection of cadmium ions, characterized in that, The structural formula of the fluorescent probe is as follows: ， When R=-C=N-(CH2)6OH, the fluorescent probe is named H3-MB.

2. A method for preparing the ultra-sensitive fluorescent probe for detecting cadmium ions according to claim 1, characterized in that, The method comprises the following steps: 1) 2,6-diformyl-4-methylphenol and salicylic hydrazide are co-dissolved in ethanol, heated to 60-100 DEG C, refluxed for 6-24 h, after complete reaction, cooled to room temperature, the precipitate is filtered, the collected supernatant is dried by a rotary evaporator to obtain a crude product, then column chromatography is used for purification, the eluent is PE:EA=5:1-100:1, and the target compound HMH is obtained by drying. 2) The compound HMH obtained in step 1) and 6-amino-1-hexanol are co-dissolved in ethanol, heated to 60-100 DEG C, refluxed for 6-24 h, after complete reaction, cooled to room temperature, the crude product is obtained by rotary evaporation, then column chromatography is used for purification, the eluent is DCM:MeOH=2:1-100:1, and the target compound H3-MB is obtained by drying.

3. The method for preparing an ultrasensitive fluorescent probe for detecting cadmium ions as described in claim 2, characterized in that, In step 1), the molar ratio of 2,6-diformyl-4-methylphenol to salicylic hydrazide is 1:1-1:

3.

4. The method according to claim 2, wherein the method is characterized by, In step 2), the molar ratio of HMH to 6-amino-1-hexanol is 1:1-1:

5.

5. Application of the ultra-sensitive fluorescent probe for detecting cadmium ions in the sensing and detection of cadmium ions according to claim 1. 6.The application of the super-sensitive fluorescent probe for detecting cadmium ions in the sensing and detecting of cadmium ions according to claim 5, wherein, The H3-MB is a fluorescent ratio type probe; the detection limit of H3-MB is 0.30 ppb, and the response time is 30 s.

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