Citrazinic acid functionalized silver nanoparticles and their preparation method and application

Abstract

The present invention relates to the field of nanotechnology detection, and specifically to a citrazinic acid functionalized silver nanoparticle, its preparation method and application. The structural formula of citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) is as follows: The Cit-AgNPs provided by the present invention are a type of nanoparticle that can sensitively detect trace amounts of Cr 3+ The colorimetric detection probe can identify trace amounts of Cr 3+ And produce a significant color change, that is, from light yellow to bright pink. The probe has the advantages of low detection limit (6.24nM), obvious new peak (580nm), high selectivity, chemical stability and wide pH range. It is fast and convenient to operate and can be widely used in environmental monitoring and public health testing. On the other hand, the Cit‑AgNPs provided by the present invention have good catalytic activity and can efficiently catalyze the reduction of 4-nitrophenol and the degradation of methylene blue. And the catalytic activity of Cit‑AgNPs remains almost similar after 5 cycles, indicating that Cit‑AgNPs has good reusability. These findings also show the great potential of Cit‑AgNPs in degrading organic pollutants.

Description

Technical Field

[0001] The present invention relates to the field of nanotechnology detection, and in particular to citrazinic acid functionalized silver nanoparticles and a preparation method and application thereof. Background Art

[0002] In recent years, the rapid development of industry and human daily activities have led to the continuous release of various heavy metals into the environment, posing a major threat to human health and the ecosystem. Heavy metal chromium is considered one of the most serious public hazards. Due to its large demand in industries such as electroplating, leather tanning and stainless steel production, high-concentration chromium wastewater has seriously threatened the ecological environment such as water bodies and soil, and is constantly accumulating in the human body through the biomagnification effect of the food chain. Although chromium is an essential trace element in the human body, excessive intake causes great harm to the human body. The toxicity of chromium is mainly related to its valence state. The toxicity of divalent chromium is very mild, while the toxicity of trivalent chromium and hexavalent chromium is more obvious. High concentrations of trivalent chromium and hexavalent chromium will cause vomiting, diarrhea, nasal mucosal damage, and even gastric cancer. Therefore, it is of great significance to develop a technical method for directly, highly selectively and sensitively detecting trace concentrations of chromium ions. At present, UV-visible and fluorescence spectrophotometry, electrochemical analysis, atomic absorption / emission spectroscopy, inductively coupled plasma atomic emission spectroscopy, etc. are commonly used to detect Cr 3+ For detection and analysis. However, these techniques are often time-consuming, expensive, and require a high level of maintenance, making them unsuitable for field applications. Compared to these traditional analytical techniques, colorimetric analysis has become a promising alternative due to its simplicity, rapidity, and low cost.

[0003] On the other hand, the pollution caused by untreated industrial toxic dyes, nitrophenol compounds and other wastewater is becoming increasingly serious. The discharge of large amounts of untreated dyes not only causes serious ecological damage, but also poses a serious threat to organisms due to their carcinogenicity, teratogenicity and non-biodegradability. For the survival of humans and other organisms, there is an urgent need for environmentally friendly and efficient ways to degrade these environmental pollutants. Adsorption is the most commonly used technology for treating organic wastewater, but it often requires complex desorption and regeneration processes. In addition, the adsorbed pollutant molecules still exist in the adsorption liquid and also cause potential secondary pollution risks. Catalytic reduction is considered to be the most promising alternative method. Through the electron transfer between the catalyst and the pollutant, it is converted into degradable molecules to achieve the purpose of protecting the environment.

[0004] Silver nanoparticles (AgNPs) possess excellent optical and electrical properties, as well as antibacterial capabilities, and are widely used in biological and chemical sensing, catalysis, electronics, materials, and other fields. In particular, in the field of colorimetric sensing, the inherent localized surface plasmon resonance (LSPR) phenomenon of silver nanoparticles causes the color of the solution to vary with factors such as particle size, shape, and interparticle spacing. This color difference can also intuitively reflect changes in the nanosilver solution. Therefore, silver nanoparticles have been effectively used to design various colorimetric probes for detecting a wide range of analytes. Furthermore, silver nanoparticles possess highly efficient catalytic reduction properties. However, individual silver nanoparticles are prone to agglomeration, resulting in a sharp decrease in their catalytic activity. Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the harm of excessive discharge of heavy metal chromium and organic dyes to the ecological environment and organisms, as well as the excellent performance of silver nanoparticles (AgNPs), the present invention provides an efficient and stable citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) and its colorimetric detection of trace Cr 3+ and applications in catalytic degradation of environmental pollutants (4-nitrophenol and methylene blue).

[0006] The technical solutions of the present invention are as follows:

[0007] In a first aspect of the present invention, there is provided a citrazinic acid functionalized silver nanoparticle, wherein the structural formula of the citrazinic acid functionalized silver nanoparticle is as follows:

[0008]

[0009] Optionally, the citrazinic acid functionalized silver nanoparticles are spherical.

[0010] A second aspect of the present invention provides a method for preparing the citrazinic acid functionalized silver nanoparticles of the present invention, comprising the steps of:

[0011] Silver nitrate and citrazinic acid are mixed in a solvent, alkali is added, and the mixture is stirred at a constant temperature for 2-6 hours to obtain citrazinic acid functionalized silver nanoparticles.

[0012] Optionally, the step of mixing silver nitrate and citrazinic acid in a solvent and adding a base specifically comprises:

[0013] Silver nitrate and citrazinic acid are mixed in a solvent to obtain a silver nitrate solution and a citrazinic acid solution respectively;

[0014] The silver nitrate solution and the citrazinic acid solution were mixed, and NaOH solution was added.

[0015] Optionally, the concentration of the silver nitrate solution is 0.1-0.5 mM, and the concentration of the citrazinic acid solution is 0.1-0.5 mM;

[0016] The silver nitrate solution and the citrazinic acid solution are mixed in a volume ratio of 1:1, wherein the volume of the silver nitrate solution is 0.5-1 mL.

[0017] Optionally, the concentration of the NaOH solution is 0.1-0.5 mM and the volume is 0.1-0.5 mL.

[0018] Optionally, the solvent is double distilled water.

[0019] Optionally, the constant temperature is 20-40°C.

[0020] The third aspect of the present invention provides a method for using the citrazinic acid functionalized silver nanoparticles as a detection probe in Cr 3+ Applications in ion detection.

[0021] A fourth aspect of the present invention provides a use of the citrazinic acid functionalized silver nanoparticles of the present invention in the degradation of organic pollutants.

[0022] Beneficial effect: The citrazinic acid functionalized silver nanoparticles Cit-AgNPs provided by the present invention can be used as trace Cr 3+ Colorimetric detection probe that can detect trace amounts of Cr 3+ And produce a significant color change, that is, from light yellow to bright pink. The probe has the advantages of low detection limit (6.24nM), obvious new peak (580nm), high selectivity, chemical stability and wide pH range. It is fast and convenient to operate and can be widely used in environmental monitoring and public health testing. At the same time, the Cit-AgNPs provided by the present invention have good catalytic activity, can efficiently catalyze the reduction of 4-nitrophenol and degrade methylene blue. And the catalytic function of Cit-AgNPs can be reused more than 5 times. These findings indicate that Cit-AgNPs also have practical application prospects in the catalysis and degradation of organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Synthesis of Cit-AgNPs and their use as a probe for the detection of trace Cr 3+ Diagram of the mechanism of action.

[0024] Figure 2 Diagram of the catalytic mechanism of Cit-AgNPs catalyzing the reduction of 4-nitrophenol and degradation of methylene blue.

[0025] Figure 3These are characterization diagrams of Cit-AgNPs in Example 1, where a is an ultraviolet absorption spectrum diagram, b is a scanning electron microscopy diagram, c is a transmission electron microscopy diagram, and d is an X-ray diffraction diagram.

[0026] Figure 4 This is the infrared spectrum analysis diagram of Cit-AgNPs in Example 1.

[0027] Figure 5 The solution color and ultraviolet absorption spectra of Cit-AgNPs when interacting with different metal cations in Example 2.

[0028] Figure 6 a in Example 2 is Cit-AgNPs and different concentrations of Cr 3+ UV absorption spectrum of Cit-AgNPs, b is the recognition of Cr 3+ Linear fitting graph of .

[0029] Figure 7 The selective recognition of Cr by Cit-AgNPs in the presence of other metals in Example 2 3+ UV absorption spectrum of .

[0030] Figure 8 The Cit-AgNPs in Example 2 recognize Cr at different pH (2-12) 3+ UV absorption spectrum of .

[0031] Figure 9 In Example 3, a is the changes in color and ultraviolet absorption spectrum of Cit-AgNPs reducing 4-nitrophenol in the presence of NaBH4, b is the reusability of Cit-AgNPs reducing 4-nitrophenol in the presence of NaBH4, c is the changes in color and ultraviolet absorption spectrum of Cit-AgNPs degrading methylene blue in the presence of NaBH4, and d is the reusability of Cit-AgNPs degrading methylene blue in the presence of NaBH4.

[0032] Figure 10 This is a graph showing the changes in color and UV absorption spectrum over time of 4-nitrophenol reduced by 1 mg / mL Cit-AgNPs in the presence of NaBH4 in Example 3.

[0033] Figure 11 This is a graph showing the changes in color and UV absorption spectrum of methylene blue degraded by 1 mg / mL Cit-AgNPs in the presence of NaBH4 over time in Example 3.

[0034] Figure 12 This is a graph showing the effect of different concentrations of Cit-AgNPs on the degradation of methylene blue in the presence of NaBH4 in Example 3. DETAILED DESCRIPTION

[0035] The present invention provides a method for colorimetrically detecting Cr in trace amounts. 3+ The present invention relates to a method for preparing citrazinic acid-functionalized silver nanoparticles (Cit-AgNPs) for catalytically degrading environmental pollutants and its application. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention.

[0036] The embodiment of the present invention provides a method for colorimetric detection of Cr in trace amounts. 3+ Citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) that catalyze the degradation of environmental pollutants. Ultraviolet spectroscopy (UV) shows that the nanoparticles exhibit a prominent absorption band at around 420 nm due to the excitation of surface plasmon resonance (SPR). Scanning electron microscope images (SEM) and transmission electron microscope images (TEM) show that the nanoparticles are spherical with an average diameter of 30 nm. X-ray diffraction (XRD) shows the presence of a face-centered cubic structure of the nanoparticles. Infrared spectrum analysis (FTIR) shows that the hydroxyl and carbonyl peaks have a certain degree of red shift, indicating that a stable metal coordination bond is formed between the carboxyl group of citrazinic acid and the silver of the nanoparticles. The structural formula of the citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) is as follows:

[0037]

[0038] Combine Figure 1 As shown, an embodiment of the present invention provides a method for preparing the citrazinic acid functionalized silver nanoparticles as described above, which comprises the steps of:

[0039] Mix silver nitrate and citrazinic acid in a solvent, add a base (for neutralizing excess or free citrazinic acid, such as NaOH), and stir at a constant temperature for 2-6 hours;

[0040] Finally, the solution turned yellow, and citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) were obtained.

[0041] In this embodiment, the nanoparticles are prepared by chemical reduction using silver nitrate and citrazinic acid.

[0042] In some embodiments, the step of mixing silver nitrate and citrazinic acid in a solvent and adding a base specifically comprises:

[0043] Silver nitrate and citrazinic acid are mixed in a solvent to obtain a silver nitrate solution and a citrazinic acid solution respectively;

[0044] The silver nitrate solution and the citrazinic acid solution were mixed, and NaOH solution was added.

[0045] In some embodiments, the concentration of the silver nitrate solution is 0.1-0.5 mM (e.g., 0.1 mM, 0.3 mM, 0.5 mM, etc.), and the concentration of the citrazinic acid solution is 0.1-0.5 mM (e.g., 0.1 mM, 0.3 mM, 0.5 mM, etc.);

[0046] The silver nitrate solution and the citrazinic acid solution are mixed in a volume ratio of 1:1. The volume of the silver nitrate solution is 0.5-1 mL, such as 0.5 mL, 0.8 mL, 1 mL, etc.

[0047] In some embodiments, the concentration of the NaOH solution (solvent is double distilled water) is 0.1-0.5 mM, such as 0.1 mM, 0.3 mM, 0.5 mM, etc., and the volume is 0.1-0.5 mL, such as 0.1 mL, 0.3 mL, 0.5 mL, etc.

[0048] In some embodiments, the solvent is double distilled water.

[0049] In some embodiments, the constant temperature is 20-40°C, such as 25°C.

[0050] In some embodiments, the constant temperature stirring is for 2-4 hours, such as 4 hours.

[0051] The embodiment of the present invention provides a method for detecting trace amounts of Cr using citrazinic acid functionalized silver nanoparticles as a detection probe. 3+ Applications in colorimetric detection.

[0052] Combine Figure 1 As shown in the aqueous solution system, the free hydroxyl groups of the nanoparticles showed a strong affinity for Cr 3+ Very strong affinity. 3+ This caused the adjacent nanoparticles to approach and form aggregates, which in turn caused the solution color to change from light yellow to bright pink, and a new absorption band at approximately 580 nm to appear. 3+ Compared with the detection methods, the detection limit (LOD) of the nanoparticles was as low as 6.24nM, showing higher sensitivity. 3+ This function is also applicable in a wide pH range.

[0053] An embodiment of the present invention provides a use of the citrazinic acid-functionalized silver nanoparticles described above in the degradation of organic pollutants.

[0054] As an excellent conductor, silver can promote the transfer of electrons between donors and acceptors. Figure 2As shown, in the presence of the reducing agent sodium borohydride (NaBH4), Cit-AgNPs can transfer electrons from NaBH4 as a donor to nitrophenol or other dye molecules as electron acceptors, thereby achieving efficient catalytic reduction of 4-nitrophenol and degradation of methylene blue. At the same time, the catalyst has high stability and can be effectively reused in multiple cycles (more than 5 times).

[0055] The present invention will be further described below by means of specific examples.

[0056] Example 1

[0057] The preparation steps of the citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) of this embodiment are as follows:

[0058] A 1 mM solution of citrazinic acid and a 1 mM solution of silver nitrate were prepared in double-distilled water and further diluted to 0.1 mM. 0.5 mL of the prepared silver nitrate solution and citrazinic acid solution were mixed in a 1:1 volume ratio and stirred at room temperature for 10 minutes. Subsequently, 0.1 mL of a 0.1 mM NaOH solution (sodium hydroxide, double-distilled water) was gradually added, and the mixture was stirred at 25°C for 4 hours. The formation of nanoparticles was visually confirmed by observing the color change of the mixed solution from colorless to yellow. The nanoparticles were characterized by ultraviolet (UV) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and infrared spectroscopy (FTIR). Figure 3 Characterization diagrams of Cit-AgNPs, where a is the UV absorption spectrum, b is the scanning electron microscopy image, c is the transmission electron microscopy image, and d is the X-ray diffraction image. Figure 4 This is the infrared spectrum analysis of citrazinic acid functionalized silver nanoparticles (Cit-AgNPs).

[0059] Example 2

[0060] In this embodiment, a citrazinic acid functionalized silver nanoparticle (Cit-AgNPs) as described in Example 1 was prepared in Cr 3+ Applications in ion detection:

[0061] 1 mL of Cit-AgNPs solution (solvent: water) was mixed with 1 mL of 100 μM solutions of several metal ions (solvent: water), including Na + , K + , Ca 2+ Mg 2+ 、Mn 2+ 、Co 2+ 、Ni 2+ 、Cu 2+ 、Hg 2+ 、Cd2+ 、Al 3+ Cr 3+ and Fe 3+ , record the changes in solution color and UV absorption spectrum. 1 mL Cit-AgNPs solution (solvent is water) was mixed with 1 mL Cr 3+ The solution (solvent is water) was mixed, and the changes in solution color and UV absorption spectrum were recorded to obtain the Cit-AgNPs and Cr 3+ The linear relationship and detection limit of ion concentration were obtained. 3+ The solutions were mixed, and then other metal ions were used to treat the solutions, and the changes in the UV absorption spectrum were recorded to examine the interference of other metal ions. In addition, the effect of medium pH was also used to explore the recognition of Cr by Cit-AgNPs. 3+ Dilute solutions of hydrochloric acid and sodium hydroxide were used to adjust the pH value of the medium, and the detection of Cr by Cit-AgNPs at different pH values ​​(2-12) was recorded. 3+ Changes in UV absorption spectra.

[0062] Figure 5 The solution color and UV absorption spectra of Cit-AgNPs when interacting with different metal cations. Figure 6 a in the figure shows the Cit-AgNPs and different concentrations of Cr 3+ UV absorption spectrum of Cit-AgNPs, b is the recognition of Cr 3+ Linear fitting graph of . Figure 7 Cit-AgNPs selectively recognize Cr in the presence of other metals 3+ UV absorption spectrum of . Figure 8 Cit-AgNPs recognize Cr at different pH (2-12) 3+ The data show that trace amounts of Cr 3+ The color of Cit-AgNPs changes from pale yellow to bright pink, and a new strong absorption appears near 580nm in the UV-visible spectrum. This colorimetric recognition is highly selective and stable, indicating its potential for application in environmental and biological applications.

[0063] Example 3

[0064] This embodiment is an application of citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) as described in Example 1 in the catalytic reduction of 4-nitrophenol (abbreviated as NP) and the degradation of methylene blue (abbreviated as MB):

[0065] A 0.1 mM 4-nitrophenol solution was prepared and an excess of NaBH₄ was added. Subsequently, a 1 mg / mL solution of Cit-AgNPs (in water) was added to the solution, and changes in color and UV absorption spectra were recorded. The effect of reaction time on the reduction process was investigated by measuring UV absorption spectra at different time intervals. After the reaction, the catalyst was recovered by centrifugation, washed three times with ethanol to eliminate degradation byproducts, and then dried. The recovered Cit-AgNPs were used as catalysts in the presence of NaBH₄, and their reusability was evaluated under similar experimental conditions. Following the same method as above, the catalytic performance of Cit-AgNPs and NaBH₄ in the degradation of methylene blue was investigated and their reusability was evaluated. Furthermore, methylene blue was treated with different doses of Cit-AgNPs to investigate the effect of catalyst concentration on the degradation process, and changes in color and UV absorption spectra were recorded.

[0066] Figure 9 a shows the changes in color and UV absorption spectrum of 4-nitrophenol reduced by Cit-AgNPs in the presence of NaBH4, b shows the reusability of 4-nitrophenol reduced by Cit-AgNPs in the presence of NaBH4, c shows the changes in color and UV absorption spectrum of methylene blue degraded by Cit-AgNPs in the presence of NaBH4, and d shows the reusability of methylene blue degraded by Cit-AgNPs in the presence of NaBH4. Figure 10 The color and UV absorption spectrum of 4-nitrophenol reduced by 1 mg / mL Cit-AgNPs in the presence of NaBH4 changed with time. Figure 11 The color and UV absorption spectrum of methylene blue degraded by 1 mg / mL Cit-AgNPs in the presence of NaBH4 change with time. Figure 12 This is the effect of different concentrations of Cit-AgNPs on the degradation of methylene blue in the presence of NaBH4.

[0067] The results showed that in the presence of Cit-AgNPs and NaBH4, 4-nitrophenol and methylene blue could be completely degraded within 5 minutes, demonstrating the strong catalytic activity of Cit-AgNPs. In addition, Cit-AgNPs have high stability and can be effectively reused in multiple cycles. With the increase of Cit-AgNPs concentration, the efficiency of methylene blue degradation will be further improved.

[0068] In summary, the present invention provides a trace Cr 3+ Preparation method of colorimetric detection probe citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) and its multifunctional application. On the one hand, the citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) provided by the present invention are a kind of colorimetric detection probe that can sensitively detect trace amounts of Cr 3+The colorimetric detection probe can identify trace amounts of Cr 3+ And produce obvious color change, that is, change from light yellow to bright pink. It has the advantages of low detection limit (6.24nM), high selectivity, chemical stability and wide pH application range. It is fast and convenient to operate and can be widely used in environmental monitoring and public health detection. On the other hand, the citrazinic acid functionalized silver nanoparticles (Cit-AgNPs) provided by the present invention have good catalytic activity, can efficiently catalyze the reduction of 4-nitrophenol and degrade methylene blue. And the catalytic activity of Cit-AgNPs remains almost similar after 5 cycles, indicating that Cit-AgNPs can be reused. These findings highlight the potential of Cit-AgNPs to degrade organic pollutants.

[0069] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A citrazinic acid functionalized silver nanoparticle, characterized in that: The structural formula of the citrazinic acid functionalized silver nanoparticles is shown below:

2. The citrazinic acid functionalized silver nanoparticles according to claim 1, characterized in that The citrazinic acid functionalized silver nanoparticles are spherical.

3. A method for preparing citrazinic acid functionalized silver nanoparticles according to any one of claims 1 to 2, characterized in that: Including steps: Silver nitrate and citrazinic acid are mixed in a solvent, alkali is added, and the mixture is stirred at a constant temperature for 2-6 hours to obtain citrazinic acid functionalized silver nanoparticles.

4. The method for preparing citrazinic acid functionalized silver nanoparticles according to claim 3, wherein: The step of mixing silver nitrate and citrazinic acid in a solvent and adding a base specifically comprises: Silver nitrate and citrazinic acid are mixed in a solvent to obtain a silver nitrate solution and a citrazinic acid solution respectively; The silver nitrate solution and the citrazinic acid solution were mixed, and NaOH solution was added.

5. The method for preparing citrazinic acid functionalized silver nanoparticles according to claim 4, characterized in that: The concentration of the silver nitrate solution is 0.1-0.5 mM, and the concentration of the citrazinic acid solution is 0.1-0.5 mM; The silver nitrate solution and the citrazinic acid solution are mixed in a volume ratio of 1:1, wherein the volume of the silver nitrate solution is 0.5-1 mL.

6. The method for preparing citrazinic acid functionalized silver nanoparticles according to claim 4, characterized in that: The concentration of the NaOH solution is 0.1-0.5 mM, and the volume is 0.1-0.5 mL.

7. The method for preparing citrazinic acid functionalized silver nanoparticles according to claim 3 or 4, characterized in that: The solvent is double distilled water.

8. The method for preparing citrazinic acid functionalized silver nanoparticles according to claim 3 or 4, characterized in that: The constant temperature is 20-40°C.

9. A method for detecting Cr using the citrazinic acid functionalized silver nanoparticles according to any one of claims 1 to 2 as a detection probe 3+ Applications in ion detection.

10. Use of the citrazinic acid functionalized silver nanoparticles according to any one of claims 1 to 2 in degrading organic pollutants.

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