Surface-enhanced Raman detection substrate for water pollutant detection and preparation method of surface-enhanced Raman detection substrate

Abstract

The invention discloses a surface-enhanced Raman detection substrate for water pollutant detection and a preparation method thereof, a dendritic cluster structure formed by naturally drying nanogold sol on a hydrophobic carbon film is constructed, the dendritic cluster structure is transferred and fixed on a tin foil-glass slide substrate, and the dendritic nanogold structure forms dense hot spots through droplet self-assembly, so that the surface-enhanced Raman detection substrate for water pollutant detection is obtained. The local electromagnetic field enhancement effect is obviously improved, so that high sensitivity is obtained; meanwhile, the structure is spontaneously formed on the hydrophobic substrate, the process does not need complex equipment or accurate control, only natural drying is needed, the preparation process is greatly simplified, and the reproducibility between batches is improved; and finally, the structure is stably fixed on the glass slide through the ultraviolet curing adhesive, so that the structure does not fall off in the detection process, and the signal is stable. Therefore, on the premise of ensuring high detection sensitivity, simplicity and convenience of substrate preparation, structural stability and high reproducibility of a detection result are realized, and the method is particularly suitable for on-site rapid SERS detection of trace pollutants in a complex water body.

Description

Technical Field

[0001] This invention belongs to the field of pollutant detection technology, specifically relating to surface-enhanced Raman spectroscopy substrates for detecting pollutants in water and their preparation methods. Background Technology

[0002] Optical sensing technology is a crucial component of the modern information industry, playing a vital role in sensory processing. However, it requires close collaboration among environmental science, electromagnetics, and biochemistry, and relies on the integrated application of knowledge in signal acquisition, transmission, and processing, making it a multidisciplinary application technology. Against this backdrop, Raman spectroscopy based on surface-enhanced Raman scattering (SERS) technology is increasingly important for detecting detailed structural information of chemical and biomolecules. SERS significantly enhances weak Raman scattered light by exciting surface plasmon resonances or localized surface plasmon resonances in metallic nanostructures. Compared to traditional analytical methods, SERS possesses ultra-high sensitivity at the single-molecule level and the ability to reveal intrinsic molecular fingerprint information. However, traditional confocal Raman spectrometers based on spatial optical paths suffer from large size and poor stability, severely limiting their practical applications outside the laboratory. In contrast, optical fibers offer robust and flexible probes, stable optical paths, and remote sensing capabilities, making them suitable for detection applications under various conditions. On the other hand, the fabrication of SERS substrates also faces bottlenecks, necessitating the development of an easy-to-fabricate, low-cost, and mass-producible high-efficiency SERS substrate.

[0003] Currently, the detection of trace organic pollutants (such as antibiotics and pesticides) in water bodies mainly relies on methods such as liquid chromatography-mass spectrometry (LC-MS). Although these methods are highly accurate, they suffer from drawbacks such as expensive and bulky equipment, complex operation, long processing times, and the need for professional personnel, making rapid on-site detection difficult. Existing SERS technologies mainly include:

[0004] 1. Commercially available precious metal sols: such as gold nanoparticles and silver nanoparticle colloids. The principle is to mix the test solution with the colloid, and the pollutant molecules are adsorbed on the surface of the nanoparticles or at the "hot spots" (interparticle gaps), thereby obtaining an enhanced Raman signal.

[0005] 2. Rough metal electrodes: Rough silver and gold electrodes are prepared by electrochemical redox cycle (ORC) method.

[0006] 3. Nanofilms prepared by vacuum deposition: Gold or silver nanofilms are prepared on substrates such as silicon wafers and glass by means of magnetron sputtering, electron beam evaporation, etc.

[0007] The above-mentioned technologies mainly have the following drawbacks:

[0008] 1. Insufficient sensitivity and stability: The "hot spots" of commercially available colloids form randomly, resulting in poor uniformity and repeatability, leading to large signal fluctuations and insufficient detection limits (typically only at the mg / L to μg / mL level), making it difficult to meet the needs of ultra-trace detection (μg / L or ng / L level). This is because the nanoparticle formation process is uncontrollable.

[0009] 2. The preparation process is complex and costly: electrochemical methods require specialized electrochemical workstations, while vacuum deposition methods rely on expensive equipment and energy-intensive environments. This is because the preparation methods depend on large-scale instruments.

[0010] 3. The substrate is difficult to preserve and integrate: The sol solution is difficult to transport and preserve, and rough electrodes and thin film substrates are prone to oxidation, sulfidation, and contamination during long-term storage, leading to performance degradation. This is because the active surface is exposed to air.

[0011] 4. Difficulty in equipment integration: Existing methods are mostly limited to manual operation in the laboratory and are difficult to integrate with microfluidics and portable Raman spectrometers to form a complete on-site testing device. This is because there is a lack of a substrate structure designed for device integration. Summary of the Invention

[0012] The purpose of this invention is to provide a surface-enhanced Raman spectroscopy (SERS) substrate and its preparation method for detecting pollutants in water. By utilizing the strong electric field coupling effect of the dendritic gold nanoparticle SERS substrate, the Raman signal is significantly enhanced, thereby enabling the detection of pollutants in water and solving the problems mentioned in the background art.

[0013] To achieve the above objectives, the present invention provides a surface-enhanced Raman detection substrate for detecting pollutants in water. The substrate is composed of dendritic clusters formed by natural drying of nano-gold sol on a hydrophobic carbon film. The dendritic clusters are transferred as a whole onto tin foil and fixed onto a glass slide by UV-curing adhesive.

[0014] Another aspect of the present invention provides a method for preparing a surface-enhanced Raman detection substrate for detecting pollutants in water, comprising the following steps:

[0015] Step 1: Prepare the solution, including:

[0016] Take 85 mL of 40.5% chloroauric acid in a test tube, add 60 mL of 18.2 MΩ purified water, and dilute to a 1% solution; then take 1 mL of the 1% chloroauric acid solution in an Erlenmeyer flask, add water and dilute to 100 mL to obtain a 0.01% chloroauric acid solution; prepare a 1% sodium citrate solution.

[0017] Step 2: Preparation of colloidal gold, including:

[0018] Heat and stir a 0.01% chloroauric acid solution until it just begins to boil. Then add 2 ml of 1% sodium citrate solution to the conical flask and continue stirring. Observe the solution gradually change from pale yellow to turbid and then to clear. Stop heating when the solution turns a bright red color to obtain a colloidal gold solution with a particle size of about 8 nm. Aliquot the obtained colloidal gold solution and store it in the dark and refrigerated.

[0019] Step 3: Fabrication of a dendritic SERS substrate, including:

[0020] The prepared gold nanoparticle sol was dropped onto a hydrophobic carbon film and allowed to dry naturally, forming dendritic clusters after drying; the formed dendritic clusters were then transferred onto tin foil to form a SERS substrate.

[0021] Step 4: Complete the substrate preparation.

[0022] Preferably, in step two, the 0.01% chloroauric acid solution is stirred using a magnetic stirrer.

[0023] Preferably, the dendritic clusters are formed by self-assembly on a hydrophobic carbon film by adding nano-gold sol and allowing it to dry naturally, utilizing the surface tension of the droplets and the small size effect of the nanoparticles.

[0024] Preferably, the substrate is finally fixed on the glass slide using UV-curable adhesive.

[0025] Preferably, in step two, the sodium citrate solution is added all at once to the boiling chloroauric acid solution.

[0026] Preferably, in step three, the natural drying process is carried out in a sealed space.

[0027] Preferably, the prepared SERS substrate is sealed and stored.

[0028] Technical effects and advantages of the present invention: The surface-enhanced Raman detection substrate and its preparation method for detecting pollutants in water proposed in this invention have the following advantages compared with the prior art:

[0029] This invention constructs a dendritic cluster structure formed by the natural drying of gold nanoparticles on a hydrophobic carbon film, and then transfers and fixes it onto a tin foil-glass slide substrate. The dendritic gold nanoparticle structure forms dense "hot spots" through droplet self-assembly, significantly enhancing the local electromagnetic field enhancement effect and thus achieving high sensitivity. Simultaneously, this structure forms spontaneously on the hydrophobic substrate, requiring no complex equipment or precise control, only natural drying, greatly simplifying the preparation process and improving batch-to-batch reproducibility. Finally, a UV-curable adhesive is used to stably fix the structure to the glass slide, ensuring that the structure does not detach and the signal remains stable during detection. Therefore, this invention achieves simplicity in substrate preparation, structural stability, and high reproducibility of detection results while maintaining high detection sensitivity, making it particularly suitable for rapid on-site SERS detection of trace pollutants in complex water bodies. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the fabrication process of the surface-enhanced Raman spectroscopy substrate for detecting pollutants in water, as described in this invention.

[0031] Figure 2 This is an electron microscope image of the dendritic colloidal gold of the present invention;

[0032] Figure 3 This is a schematic diagram of the water pollutant Raman detection sensing device of the present invention;

[0033] Figure 4 The Raman spectrum of the ciprofloxacin solution detected according to the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment provides a surface-enhanced Raman detection substrate for detecting pollutants in water. The substrate is composed of dendritic clusters formed by natural drying of nano-gold sol on a hydrophobic carbon film. The dendritic clusters are transferred as a whole onto tin foil and fixed onto a glass slide by UV-curing adhesive.

[0037] The surface-enhanced Raman detection substrate for detecting pollutants in water provided by this invention has a dendritic gold nanocluster structure that forms a dense "hot spot" region during natural drying through droplet capillary action and nanoparticle self-assembly, which significantly enhances the local surface plasmon resonance effect, thereby greatly improving the Raman signal intensity and achieving highly sensitive detection of trace pollutants in water.

[0038] Meanwhile, the structure is formed spontaneously by a hydrophobic carbon film, which is simple to process and does not require complex equipment or precise control, thus improving the repeatability and batch consistency of substrate preparation. The formed dendritic clusters are transferred as a whole and fixed to the glass slide with UV-curable adhesive, which effectively prevents the nanostructure from falling off or deforming during the detection process, ensuring the long-term stability and reliability of the detection signal.

[0039] In summary, this invention, while ensuring high sensitivity, also has the advantages of simple preparation, stable structure, and good reproducibility, making it particularly suitable for on-site, rapid, and accurate SERS detection of pollutants in complex aquatic environments.

[0040] Example 2

[0041] This embodiment provides a method for preparing a surface-enhanced Raman detection substrate for detecting pollutants in water, such as... Figure 1 and Figure 2 As shown, it includes the following steps:

[0042] Step 1: Prepare the solution, including:

[0043] Take 85 mL of 40.5% chloroauric acid in a test tube, add 60 mL of 18.2 MΩ purified water, and dilute to a 1% solution; then take 1 mL of the 1% chloroauric acid solution in an Erlenmeyer flask, add water and dilute to 100 mL to obtain a 0.01% chloroauric acid solution; prepare a 1% sodium citrate solution.

[0044] Step 2: Preparation of colloidal gold, including:

[0045] The 0.01% chloroauric acid solution was heated and stirred with a magnetic stirrer. When it was about to boil, 2 ml of 1% sodium citrate solution was added to the conical flask at once. Stirring was continued, and the solution was observed to gradually become turbid from pale yellow and then clear. Heating was stopped when the solution turned a clear red color, and a colloidal gold solution with a particle size of about 8 nm was obtained. The obtained colloidal gold solution was dispensed and stored in the dark and refrigerated.

[0046] Step 3: Fabrication of a dendritic SERS substrate, including:

[0047] The prepared gold nanoparticle sol was dropped onto a hydrophobic carbon film and allowed to dry naturally in a sealed space, forming dendritic clusters. These dendritic clusters were then transferred onto tin foil to form a SERS substrate. The dendritic clusters were formed through self-assembly on the hydrophobic carbon film by the droplet surface tension and the small size effect of the nanoparticles during the droplet-on and natural drying process. The substrate was finally fixed onto a glass slide using UV-curable adhesive.

[0048] By controlling the concentrations of chloroauric acid and sodium citrate and the reaction conditions, a uniform gold nanoparticle sol with a particle size of approximately 8 nm was prepared. During the natural drying process on a hydrophobic carbon film, the surface tension of the droplets and the self-assembly effect of the nanoparticles formed a dendritic gold nanocluster structure with dense "hot spots," which greatly enhanced the local electromagnetic field and significantly improved the Raman signal intensity, enabling ultrasensitive detection of trace pollutants (such as pesticides, dyes, antibiotics, etc.) in water.

[0049] Step 4: Complete the substrate preparation and seal and store the prepared SERS substrate.

[0050] The entire preparation process does not require expensive equipment or complex processes, relying only on routine operations such as solution preparation, heating reduction, natural drying and transfer fixation; natural drying is carried out in a sealed environment to avoid external contamination and ensure structural consistency; the morphology and distribution of nanostructures are highly repetitive between batches, the substrate performance is stable, and it is suitable for large-scale preparation.

[0051] The formed dendritic clusters are transferred as a whole to tin foil and firmly fixed to a glass slide with UV-curable adhesive, effectively preventing the structure from falling off, shifting, or being damaged by water flow during the detection process. After curing, the substrate has high mechanical strength and good water resistance, making it suitable for direct drop-on detection of liquid samples. After preparation, it is sealed and stored to maintain SERS activity for a long time, which is convenient for transportation, storage and field use.

[0052] The substrate prepared by this method has strong tolerance to complex aquatic matrices and can achieve in-situ enrichment of pollutants and signal amplification without complicated pretreatment. It is particularly suitable for application scenarios with low equipment dependence and high requirements for ease of operation, such as field, on-site or emergency monitoring.

[0053] In summary, the method of this invention, while ensuring high detection sensitivity, achieves simple preparation, structural stability, high reproducibility, and practical applicability of SERS substrates, effectively promoting the practical application of surface-enhanced Raman spectroscopy in the rapid detection of pollutants in aquatic environments.

[0054] Example 3

[0055] This embodiment provides an application of a surface-enhanced Raman detection substrate for detecting pollutants in water, such as... Figure 3As shown, in this application, the laser and Raman spectrometer are connected to the Raman probe via fiber optic cables; the Raman probe is aligned with the dendritic gold nanoparticle SERS substrate. A 785nm laser is used as the excitation source. A Raman spectrometer is used as the spectral detection device.

[0056] To ensure structural stability, the substrate is fixed on the stage. In actual field testing, the water sample to be tested is drawn up with a dropper and directly added to the SERS substrate. The gold nanoparticles on the surface are excited by a laser to enhance the Raman signal, which is then transmitted back to the Raman spectrometer for detection and analysis of various pollutants. All data are recorded and compared in real-time with standard samples in the database.

[0057] Specific implementation example: The process for testing river water samples (spiking method) or liquid samples such as biological tissue fluid is as follows:

[0058] River water samples were taken, and ciprofloxacin was added to prepare samples of different concentrations (1ug / L, 10ug / L, 100ug / L, 1mg / L), and the samples were tested respectively.

[0059] The water sample to be tested was drawn up with a dropper and directly added to the SERS substrate. The position of the Raman probe was adjusted for testing, and the data was analyzed to determine the detected substance.

[0060] Test results as follows Figure 4 As shown, this substrate exhibits excellent enrichment and signal amplification capabilities for trace antibiotic pollutants in actual water bodies, meeting the sensitivity requirements for monitoring trace organic pollutants in environmental water quality standards. The entire detection process requires only three steps: "sample drop—positioning—collection," eliminating the need for complex pretreatment processes such as centrifugation, filtration, and extraction. Single-sample testing can be completed within 5 minutes. The substrate structure is stable, remaining undissolved and unshed after water sample addition, making it compatible with portable Raman spectroscopy equipment and truly achieving "sampling and testing," meeting the rapid response needs of field, emergency, or grassroots monitoring.

[0061] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A surface-enhanced Raman detection substrate for detecting pollutants in water, characterized in that, The substrate is composed of dendritic clusters formed by the natural drying of nano-gold sol on a hydrophobic carbon film. The dendritic clusters are transferred as a whole onto tin foil and fixed onto a glass slide by UV-curing adhesive.

2. A method for preparing the surface-enhanced Raman detection substrate for detecting pollutants in water as described in claim 1, characterized in that, Includes the following steps: Step 1: Prepare the solution, including: Take 85 mL of 40.5% chloroauric acid in a test tube, add 60 mL of 18.2 MΩ purified water, and dilute to a 1% solution; then take 1 mL of the 1% chloroauric acid solution in an Erlenmeyer flask, add water and dilute to 100 mL to obtain a 0.01% chloroauric acid solution; prepare a 1% sodium citrate solution. Step 2: Preparation of colloidal gold, including: Heat and stir a 0.01% chloroauric acid solution until it just begins to boil. Then add 2 ml of 1% sodium citrate solution to the conical flask and continue stirring. Observe the solution gradually change from pale yellow to turbid and then to clear. Stop heating when the solution turns a bright red color to obtain a colloidal gold solution with a particle size of about 8 nm. Aliquot the obtained colloidal gold solution and store it in the dark and refrigerated. Step 3: Fabrication of a dendritic SERS substrate, including: The prepared gold nanoparticle sol was dropped onto a hydrophobic carbon film and allowed to dry naturally, forming dendritic clusters after drying; the formed dendritic clusters were then transferred onto tin foil to form a SERS substrate. Step 4: Complete the substrate preparation.

3. The method according to claim 2, characterized in that, In step two, the 0.01% chloroauric acid solution is stirred using a magnetic stirrer.

4. The method according to claim 2, characterized in that, The dendritic clusters are formed by self-assembly on a hydrophobic carbon film by adding nano-gold sol and allowing it to dry naturally, utilizing the surface tension of the droplets and the small size effect of the nanoparticles.

5. The method according to claim 2, characterized in that, The substrate is finally fixed onto the glass slide using UV-curable adhesive.

6. The method according to claim 2, characterized in that, In step two, the sodium citrate solution is added all at once to the boiling chloroauric acid solution.

7. The method according to claim 2, characterized in that, In step three, the natural drying process takes place in a sealed space.

8. The method according to claim 2, characterized in that, The prepared SERS substrate was sealed and stored.

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