Functionalized halloysite nanoprobes for divalent lead ion detection and separation and preparation method thereof

Abstract

The application discloses a bifunctional nano probe for detecting and separating divalent lead ions and a preparation method thereof. The nano probe is composed of an allophane nano carrier and a salicylaldehyde Schiff base functional group. The nano probe has the advantages of good dispersibility in water and low cost, can specifically, rapidly and reliably detect divalent lead ions in an aqueous solution, and can effectively adsorb and remove the divalent lead ions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of analytical testing, and relates to a bifunctional halloysite nanoprobe capable of conveniently detecting and adsorbing and separating divalent lead ions and a preparation method thereof. BACKGROUND

[0002] Divalent lead ions (Pb 2+ ) are one of the most common toxic heavy metal ions. However, lead is not necessary in physiology, and its non-biodegradability and bioaccumulation can cause lead concentration to accumulate in the environment, causing environmental pollution. Exposure to lead can cause health complications in animals and humans, leading to various adverse effects such as elevated blood pressure, emotional disorders, nerve damage, osteoporosis, tissue damage, metabolic disorders, and developmental abnormalities. Lead pollution can inhibit photosynthesis in plants, damage the absorption and transformation of water and nutrients in plants, and cause oxidative damage to plants. Therefore, detecting and removing Pb 2+ from the environment is of great significance to environmental safety and biological health.

[0003] Small organic molecule fluorescent probes have the advantages of simple operation and significant detection signal, and provide an effective analytical tool for rapid detection of Pb 2+ in the environment. Although several Pb 2+ fluorescent probes (CN104877679A, CN102432492A, CN105349135A, CN115724862A, CN106854215A) have been developed, they still have some deficiencies, such as poor water solubility and the need to add a large amount of organic solvent during the detection process. More importantly, these probes only have a single function and cannot effectively remove Pb 2+ during the analysis process. Therefore, it is necessary to design an integrated nanoprobe with detection and separation functions to quickly analyze and effectively remove Pb 2+ . SUMMARY

[0004] To solve the above problems, the present application develops a bifunctional nanoprobe by grafting a salicylaldehyde Schiff base organic functional group to halloysite nanotubes . This nanoprobe has the advantages of high sensitivity, strong specificity, good dispersibility in water, and low preparation cost, and has both selective detection ability for Pb 2+ and high removal ability, thereby realizing bifunctionality. The nanoprobe provided by the present application has the following chemical structure:

[0005]

[0006] The present application has the following beneficial effects:

[0007] (1) The nano-probe structure is simple, raw materials are easy to obtain, and easy to prepare.

[0008] (2) The nano-probe has good stability and is easy to recover.

[0009] (3) The nano-probe has good selectivity and strong anti-interference ability.

[0010] (4) The nano-probe has high selectivity and strong anti-interference ability for Pb 2+ It has the functions of fluorescence detection and adsorption separation. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Preparation route of the nano-probe.

[0012] Figure 2 Morphology of the nano-probe under scanning electron microscope.

[0013] Figure 3 Comparison of element content of the nano-probe and natural halloysite.

[0014] Figure 4 Particle size distribution of the nano-probe in water.

[0015] Figure 5 Thermogravimetric (Tg) analysis curve of the nano-probe.

[0016] Figure 6 Change of ultraviolet absorption spectrum of the nano-probe with Pb 2+ concentration.

[0017] Figure 7 Change of fluorescence spectrum of the nano-probe with Pb 2+ concentration.

[0018] Figure 8 Linear relationship between fluorescence intensity of the nano-probe and Pb 2+ concentration.

[0019] Figure 9 Selectivity and anti-interference performance of the nano-probe for Pb 2+ detection.

[0020] Figure 10 Change of fluorescence intensity of the nano-probe after interaction with Pb 2+ and pH value.

[0021] Figure 11 Response time of the nano-probe for Pb 2+ detection.

[0022] Figure 12 Relationship between nano-probe dosage, Pb 2+ concentration and removal rate. DETAILED DESCRIPTION

[0023] The application will be described in detail below with specific examples.

[0024] Example 1 Preparation process of nanoprobes

[0025] The specific preparation route is as shown in Figure 1 0.32 g of HNTs-COCl was dispersed in 3 mL of DMSO, 0.068 g (0.5 mmol) of 5-methyl salicylaldehyde and 1 mL of triethylamine were added, and stirring was continued at room temperature for 2 hours and at 45°C for 12 hours. After cooling, centrifugation was performed at 8000 rpm for 3 min, the precipitate was washed with ethyl acetate, methanol and dichloromethane in sequence, and freeze-drying was performed to obtain 0.33 g of the light yellow target product HNTs-CHO. 0.33 g of HNTs-CHO and 0.21 g (2 mmol) of 4-methylthiosemicarbazide were stirred in anhydrous ethanol at room temperature for 72 hours. The precipitate was separated by centrifugation (8000 rpm, 3 min), washed with ethanol and dichloromethane, and freeze-dried to obtain 0.34 g of the yellow target product HNTs-probe. The morphology characteristics, thermal stability and grafting rate of the nanoprobes were confirmed by scanning electron microscopy, particle size analyzer and thermogravimetric analyzer.

[0026] Example 2 Characterization experiment of nanoprobes

[0027] Under the observation of a scanning electron microscope (SEM), the nanoprobes were in a rod-like morphology, with a length ranging from 600 to 900 nm Figure 2 ). The EDS results showed that the nitrogen and sulfur contents of the modified nanoprobes increased, with mass fractions increasing from 0.38 to 2.12 and from 0 to 5.45 Figure 3 ), respectively. These two elements were widely distributed on the surface of the sample, indicating that the preparation of the probes was successful. The particle size analyzer showed that the particle size distribution of the nanoprobes was mainly concentrated in the range of 600-900 nm, and the existence of the anisotropic nanotubes led to the secondary particle size distribution between 150 and 300 nm Figure 4 ). The thermogravimetric (TG) results showed that the nanoprobes had obvious mass loss at a temperature of 200 ~ 500°C, which was probably due to the decomposition of the grafted organic fluorophore Figure 5 ). According to the final thermogravimetric calculation, the grafting rate of the nanoprobes was 1.54%.

[0028] Example 3 Characterization of nanoprobes for Pb 2+ concentration gradient experiment

[0029] In an aqueous solution, when the concentration of Pb 2+When the concentration increased from 0 to 4 μM, the UV absorption spectrum of the nanoprobe (0.8 mg / mL) changed significantly, with the absorption peak at 210 nm strengthening and slightly red-shifted, and the absorption peak near 280 nm slightly weakening. Figure 6 Meanwhile, the fluorescence spectrum of the probe changes with Pb. 2+ Increased concentration enhances ( Figure 7 ).like Figure 8 As shown, within the range of 0 ~ 4 μM, the increase in fluorescence intensity of the probe at 365 nm is related to Pb. 2+ The concentrations show a positive correlation, satisfying the quantitative analysis equation: y = 98.0 + 184.2 X (R 2 = 0.9933). Further calculations using 3σ / S yielded the probe's response to Pb. 2+ The detection limit is 1.2 nM, indicating that this nanoprobe is effective against Pb. 2+ It has very high sensitivity.

[0030] Example 4: Nanoprobes for Pb 2+ Selective experiments

[0031] like Figure 9 As shown, only Pb exists in aqueous solution. 2+ (4 μM) significantly enhanced the fluorescence intensity of the nanoprobe (0.8 mg / mL), while other common metal ions (4 μM) had very little effect on the fluorescence intensity of the probe. Furthermore, when various metal ions reacted with Pb... 2+ The coexistence did not cause the probe to target Pb 2+ A significant decrease in the detected fluorescence signal indicates that this nanoprobe is effective against Pb. 2+ The detection exhibits good selectivity and anti-interference capabilities.

[0032] Example 5: Experiment on the effect of solution pH on probe detection signal

[0033] The pH conditions of the detection solution also significantly affect the detection signal of the probe. For example... Figure 10 As shown, in aqueous solution, the fluorescence intensity of the probe (0.8 mg / mL) remained relatively stable within a pH range of 3 to 12, indicating its excellent stability. However, the addition of Pb... 2+ After (4 μM), the fluorescence intensity was significantly enhanced, especially in the pH range of 7-11, which can effectively detect Pb. 2+ Therefore, within a suitable pH range of 7-11, this probe exhibits optimal detection performance.

[0034] Example 6: Probe detection of Pb 2+ Response time experiment

[0035] As Figure 11 shown, the fluorescence intensity of the probe (0.8 mg / mL) at 365 nm increased rapidly after the addition of different concentrations of Pb 2+ (1 μM and 2.5 μM), and reached a maximum within 30 s, and then tended to be stable. Therefore, the probe can rapidly detect Pb 2+ .

[0036] Example 7 Detection experiment of the probe for Pb 2+ in reagent water samples

[0037] In order to further verify the reliability of the detection results, the nano-probe was used to detect Pb 2+ in pond and tap water. The results showed that no trace of Pb 2+ was detected in these water samples. Subsequently, 0.5, 1 and 2 μM of Pb 2+ was added to the water samples by standard addition recovery method. The detection results of the probe had a recovery rate of 95.1% ~ 101.6%, and a relative standard deviation of 2.1% ~ 3.2%. These results were very consistent with the results of atomic absorption spectrometry (AAS), and therefore the probe had excellent reliability in detecting Pb 2+ in water samples.

[0038] Example 8 Adsorption and removal experiment of the probe for Pb 2+

[0039] As Figure 12 shown, the adsorption rate of Pb 2+ increased gradually as the amount of the probe increased from 0.1 mg / mL to 0.8 mg / mL. However, when the concentration of Pb 2+ increased from 0.5 μM to 2 μM, the adsorption rate decreased. When the amount of the probe reached 0.8 mg / mL, the adsorption rate of different concentrations of Pb 2+ all exceeded 95%. These results showed that the probe can effectively remove Pb 2+ in water samples, purify water quality, and has important significance for environmental protection and human health.

[0040] In summary, the nano-probe can be used for fluorescence detection and effective removal of Pb 2+ in water samples, and has the characteristics of good selectivity, strong anti-interference ability, wide pH adaptation range, and simplicity and rapidity.​

Claims

1. A bifunctional nanoprobe for detecting and removing divalent lead ions, characterized in that The bifunctional nanoprobe for detecting and removing divalent lead ions is a salicylaldehyde Schiff base functionalized halloysite nanotube, and the chemical structure of the bifunctional nanoprobe is as follows: .

2. A method of preparing the bifunctional nanoprobe of claim 1, characterized by: In 3 mL of dimethylsulfoxide solution, 0.068 g of 5-methylsalicylaldehyde, 0.32 g of halloysite oxalyl chloride, the chemical structure of which is , and 1 mL of triethylamine were stirred at room temperature for 2 hours, at 45°C for 12 hours, and centrifuged. After the obtained solid was stirred with 0.21 g of 4-methylthiosemicarbazide in anhydrous ethanol at room temperature for 72 hours, it was centrifuged, washed, and freeze-dried.

3. The use of the nanoprobe of claim 1 for the fluorescence detection and adsorptive separation of divalent lead ions.

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