A gadolinium oxide composite material containing zinc ions for a SERS substrate and a method for preparing the same

Abstract

This invention proposes a zinc-containing gadolinium oxide composite material for SERS substrates and its preparation method. Addressing the problems of high substrate cost, poor biocompatibility, non-uniform surface nanostructures, and limited research on semiconductors in the SERS field associated with traditional noble metal SERS substrates, this invention uses Gd₂O₃ as the material and prepares a low-cost semiconductor SERS material with a uniform surface nanostructure via a solvothermal method and calcination. Furthermore, it utilizes Zn₂O₃ as the substrate material. 2+ Modify it using Zn 2+ The introduction of [a specific ingredient] increases the oxygen defect content, thereby enhancing the charge transfer effect between the SERS material and the molecular probe, and achieving a better detection concentration.

Description

Technical Field

[0001] This invention belongs to the field of nanotechnology and detection. Background Technology

[0002] In recent decades, quinolone antibiotics have gained a significant position in the medical and livestock industries through continuous structural optimization. They possess excellent pharmacological properties, with potent bactericidal activity, good bioavailability, excellent tissue penetration, and high cost-effectiveness making them the first choice for treating bacterial infections, particularly in the genitourinary and respiratory systems. However, the widespread use of quinolone drugs in medicine, aquaculture, and livestock production has accelerated the development of drug resistance in pathogens. Non-compliant use and overuse of quinolone drugs have led to frequent and persistent detection of quinolone residues in animal-derived foods, soil, and aquatic environments. Decreased clinical efficacy due to antimicrobial resistance and severe pollution of food and the ecological environment pose a serious threat to public health and ecological safety. SERS technology, as a non-destructive analytical tool, has been applied in biosensing, electroanalysis, interface research, environmental analysis, fiber optic sensing, food contamination, and other related fields. Its discoveries have greatly advanced the development of Raman spectroscopy and demonstrated broad application potential in chemistry, biology, and materials science. Among the many development directions, the research and development of new SERS materials has become one of the hot topics in this field.

[0003] Early SERS substrates were primarily based on noble metal nanostructures (such as Au, Ag, and Cu). However, their high substrate cost, poor biocompatibility, and inhomogeneous surface nanostructures have led to a shift in SERS research, prompting the exploration of high-performance non-noble metal SERS active substrates. With the rapid development of nanoscience, alternative materials such as metal oxides, transition metals, graphene, and semiconductors have become candidate materials for high-performance SERS. Among these, semiconductor nanomaterials are particularly attractive, as the presence of internal vacancies / defects in semiconductors plays a crucial role in enhancing SERS activity. Among various functional materials, gadolinium oxide (Gd₂O₃) shows promise as a candidate material for SERS substrates due to its unique physicochemical properties. These properties include excellent crystal stability, superior thermal conductivity, and a wide optical bandgap. Furthermore, Gd₂O₃ also possesses significant advantages such as being non-toxic, non-hygroscopic, and having low phonon energy (approximately 600 cm⁻¹). -1 High dielectric constant and high refractive index. However, to date, single materials can no longer meet people's needs for SERS materials. Therefore, how to develop new Gd2O3-based SERS materials has become one of the research focuses of many researchers in this field. Summary of the Invention

[0004] This invention proposes a zinc-containing gadolinium oxide composite material for SERS substrates and its preparation method. Addressing the problems of high substrate cost, poor biocompatibility, non-uniform surface nanostructures, and limited research on semiconductors in the SERS field associated with traditional noble metal SERS substrates, this invention uses Gd₂O₃ as the material and prepares a low-cost semiconductor SERS material with a uniform surface nanostructure via a solvothermal method and calcination. Furthermore, it utilizes Zn₂O₃ as the substrate material. 2+ Modify it using Zn 2+ The introduction of [a specific technology] increases the oxygen defect content, enhances the charge transfer effect between the SERS material and the molecular probe, and achieves better layer-by-layer concentration.

[0005] A zinc-containing gadolinium oxide composite material for SERS substrates, characterized in that the composite material is based on gadolinium oxide and doped with zinc in an ionic state, and its chemical formula is Zn-Gd2O3.

[0006] The zinc-containing gadolinium oxide composite material for SERS substrates is characterized by being prepared according to the following method:

[0007] Step 1: Place Gd₂O₃ and different masses of ZnCl₂ into separate beakers. Then add 5 ml of nitric acid and sonicate until completely dissolved. Next, heat to evaporate the solution until a white powder precipitates.

[0008] Step 2: Add ethylene glycol and polyethylene glycol to the solution, stir well, then add sodium hydroxide ethylene glycol solution dropwise to adjust the temperature. Then transfer the solution to the reaction vessel and react under heating conditions for a period of time. After the reaction is cooled naturally at a constant temperature, centrifuge the solution, wash it several times with deionized water and ethanol, and then dry it under vacuum drying conditions at 50°C.

[0009] Step 3: After grinding, calcine at 550℃ for 4 h to obtain Zn-Gd2O3.

[0010] The beneficial effects of this invention are:

[0011] 1. Zn-Gd2O3 prepared by solvothermal and calcination has a high surface roughness due to its small particle size, which enhances the interaction between incident light and surface adsorbed molecules.

[0012] 2. Introducing Zn through ion doping 2+ Without damaging Gd2O3NPs, the oxygen defect content on the surface of Gd2O3NPs is increased, giving them a larger CT value.

[0013] 3. The synthesis reaction is simple to operate, and the obtained materials are evenly distributed.

[0014] 4. Zn-Gd2O3 has a small band gap energy and strong charge transfer efficiency, which enhances the SERS effect and thus improves the SERS signal strength. Attached Figure Description

[0015] Figure 1 XRD patterns of Gd2O3 and Zn-Gd2O3NPs are shown, where (1), (2), (3), (4) and (5) represent Zn doping, respectively. 2 + Gd2O3 NPs at proportions of 0%, 0.5%, 1%, 3% and 5%.

[0016] Figure 2 The image shows the Raman plots of Gd2O3 and Zn-Gd2O3 NPs, where (1), (2), (3), (4) and (5) represent Zn doping, respectively. 2+ Gd2O3 NPs at proportions of 0%, 0.5%, 1%, 3% and 5%.

[0017] Figure 3 The images show TEM images of Gd₂O₃ and Zn-Gd₂O₃ NPs. (1), (2), (3), (4), and (5) represent Zn doping, respectively. 2 + Gd2O3 NPs with doping ratios of 0%, 0.5%, 1%, 3% and 5%, (6) is the energy spectrum of Zn-Gd2O3 NPs with a doping ratio of 1%.

[0018] Figure 4 The images show XPS spectra of Gd₂O₃ and Zn-Gd₂O₃ NPs. Figures (A), (B), (C), and (D) represent the spectra of Gd 4d, O 1s, Zn 2p, and the overall spectrum, respectively. Figures (1), (2), (3), (4), and (5) represent the spectra of doped Zn. 2+ Gd2O3 NPs at proportions of 0%, 0.5%, 1%, 3% and 5%.

[0019] Figure 5 (ɑh𝜈) represents Gd₂O₃ NPs and Zn-Gd₂O₃ NPs. 2 The graph shows the relationship between the photon energy (hi) and the doped Zn, where (1), (2), (3), (4), and (5) represent the doped Zn, respectively. 2+ Gd2O3 NPs at proportions of 0%, 0.5%, 1%, 3% and 5%.

[0020] Figure 6 The SERS detection limit diagram for drug molecules of 1% Zn-Gd2O3 NPs is shown, where (1), (2), (3) and (4) are ENR, NOR, LEV and CIP, respectively. Detailed Implementation

[0021] Example 1

[0022] Zn prepared by solvothermal method 2+ Zn-Gd2O3 NPs with different doping ratios. First, weigh 0.5494 g of Gd2O3 and weigh 0.001 g of ZnCl2 according to the doping ratio of 0.5%, and place them in a beaker. Then add 5 ml of nitric acid and sonicate to dissolve it completely. Then heat and evaporate the solution until a white powder precipitates. Add ethylene glycol and polyethylene glycol (Mw=600) to the solution and stir evenly. Then add 0.3 mol / L sodium hydroxide ethylene glycol solution dropwise to adjust the pH to 9. Then transfer the solution to a 50 ml reaction vessel and react at 100℃ for 4 h. After the reaction is cooled naturally at a constant temperature, centrifuge and wash repeatedly with deionized water and ethanol. Then dry under vacuum drying at 50℃, grind and calcine at 550℃ for 4 h to obtain Zn-Gd2O3NPS, labeled as (2).

[0023] Example 2

[0024] Zn prepared by solvothermal method 2+ Zn-Gd2O3 NPs with different doping ratios. First, weigh 0.5494 g of Gd2O3 and weigh 0.002 g of ZnCl2 according to the doping ratio of 1%, and place them in a beaker. Then add 5 ml of nitric acid and sonicate to dissolve it completely. Then heat and evaporate the solution until a white powder precipitates. Add ethylene glycol and polyethylene glycol (Mw=600) to the solution and stir evenly. Then add 0.3 mol / L sodium hydroxide ethylene glycol solution dropwise to adjust the pH to 9. Then transfer the solution to a 50 ml reaction vessel and react at 100℃ for 4 h. After the reaction is cooled naturally at a constant temperature, centrifuge and wash repeatedly with deionized water and ethanol. Then dry under vacuum drying at 50℃, grind and calcine at 550℃ for 4 h to obtain Zn-Gd2O3NPS, labeled as (3).

[0025] Example 3

[0026] Zn prepared by solvothermal method 2+Zn-Gd2O3 NPs with different doping ratios. First, weigh 0.5494 g of Gd2O3 and weigh 0.006 g of ZnCl2 according to the doping ratio of 3%, and place them in a beaker. Then add 5 ml of nitric acid and sonicate to dissolve it completely. Then heat and evaporate the solution until a white powder precipitates. Add ethylene glycol and polyethylene glycol (Mw=600) to the solution and stir evenly. Then add 0.3 mol / L sodium hydroxide ethylene glycol solution dropwise to adjust the pH to 9. Then transfer the solution to a 50 ml reaction vessel and react at 100℃ for 4 h. After the reaction is cooled naturally at a constant temperature, centrifuge and wash repeatedly with deionized water and ethanol. Then dry under vacuum drying at 50℃, grind and calcine at 550℃ for 4 h to obtain Zn-Gd2O3NPS, labeled as (4).

[0027] Example 4

[0028] Zn prepared by solvothermal method 2+ Zn-Gd2O3 NPs with different doping ratios. First, weigh 0.5494 g of Gd2O3 and weigh 0.010 g of ZnCl2 according to the doping ratio of 5%, and place them in a beaker. Then add 5 ml of nitric acid and sonicate to dissolve it completely. Then heat and evaporate the solution until a white powder precipitates. Add ethylene glycol and polyethylene glycol (Mw=600) to the solution and stir evenly. Then add 0.3 mol / L sodium hydroxide ethylene glycol solution dropwise to adjust the pH to 9. Then transfer the solution to a 50 ml reaction vessel and react at 100℃ for 4 h. After the reaction is cooled naturally at a constant temperature, centrifuge and wash repeatedly with deionized water and ethanol. Then dry under vacuum drying at 50℃, grind and calcine at 550℃ for 4 h to obtain Zn-Gd2O3NPS, labeled as (5).

[0029] Comparative Example 1

[0030] Gd₂O₃ NPs were prepared by a solvothermal method. First, 0.5494 g of Gd₂O₃ was weighed, and then 5 ml of nitric acid was added and sonicated to completely dissolve it. The solution was then heated to evaporate until a white powder precipitated. Ethylene glycol and polyethylene glycol (Mw=600) were added to the solution and stirred until homogeneous. Then, 0.3 mol / L sodium hydroxide ethylene glycol solution was added dropwise to adjust the pH to 9. The solution was then transferred to a 50 ml reactor and reacted at 100 °C for 4 h. After the reaction was carried out at a constant temperature and allowed to cool naturally, the solution was centrifuged and washed repeatedly with deionized water and ethanol. The solution was then dried under vacuum at 50 °C, ground, and calcined at 550 °C for 4 h to obtain Gd₂O₃ NPs without Zn²⁺ doping, labeled as (1).

[0031] XRD was used to investigate the crystal structures of Zn-Gd₂O₃ NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%), such as... Figure 1 As shown, the figure displays the XRD patterns of Zn-Gd₂O₃ NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%). Comparison of the diffraction peak positions with the standard card (PDF#86-2477) reveals no shift, and no ZnO diffraction peaks are observed, indicating that ZnO does not exhibit diffraction peaks. 2+ The doping of Zn-Gd₂O₃ NPs did not change the crystal structure, which remained cubic. The cell sizes of Zn-Gd₂O₃ NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%) were calculated to be 9.92 nm, 11.67 nm, 12.07 nm, 11.8 nm, and 11.44 nm, respectively. This shows that the doping of Zn-Gd₂O₃ NPs with different ratios did not change the crystal structure of Gd₂O₃ NPs, which remained cubic. 2+ With doping, the particle size of the NPs is larger than that of the undoped Gd₂O₃, and the grain size gradually increases, especially at 1% Zn. 2+ The particle size is at its maximum when doped; however, it decreases when the doping ratio exceeds 1%. As can be seen from the figure, Zn... 2+ It exists in the interstitial spaces of Gd2O3 NPs in the form of ions.

[0032] Raman spectroscopy can reveal the crystal phases of Zn-Gd₂O₃ NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%), such as... Figure 2 As shown in the figure. It can be seen from the image that it is located at 360 cm. -1 The peak position corresponds to the symmetric stretching vibration of the Gd-O bond, which is an essential characteristic peak of the cubic phase Gd₂O₃, indicating that Gd₂O₃ NPs are still in the cubic phase, and Zn 2+ The doping did not cause a change in the crystal phase. No characteristic peaks of ZnO were observed in the figure, indicating that no ZnO was formed, which is consistent with the XRD results.

[0033] TEM can be used to observe crystal morphology and crystal structure. TEM was used to characterize Zn-Gd2O3 NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%). Figure 3 TEM images of Zn-Gd₂O₃ NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%) are shown. It can be observed that their shapes are all relatively regular ellipsoids, compared to undoped Zn. 2+ Comparing sample (1) with samples (2), (3), (4) and (5), it was found that Zn 2+The doping did not cause a significant change in particle morphology. High-magnification TEM images of Zn-Gd₂O₃ NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%) are visible in the upper right corner of the figure. Obvious lattice fringes are visible. The lattice fringes corresponding to the (222) crystal plane in the figure are marked as d(222) = 0.312 nm, belonging to the cubic phase Gd₂O₃. This indicates that Zn… 2+ The doping did not cause any change in the crystal phase of Gd2O3NPs, which is consistent with the XRD analysis results. Figure 3 Image (6) shows the energy spectrum of Zn-Gd₂O₃ with a doping ratio of 1%. The green part represents Gd, the yellow part represents Zn, and the red part represents O. It can be seen from the spectrum that Zn is present. 2+ They are uniformly distributed on Gd2O3 NPs.

[0034] XPS is an excellent tool for detecting the elemental composition of powders. XPS was used to test Zn-Gd2O3 NPs with different doping ratios (0%, 0.5%, 1%, 3% and 5%) to observe their elemental composition. Figure 4 XPS plots of Zn-Gd₂O₃ NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%) are shown. As seen in Figure (A), the Gd-XPS plot shows two peaks at 141.8 eV and 145.6 eV, which belong to Gd₄d₃ of Gd₂O₃, respectively. 3 / 2 and 4D 5 / 2 In Zn 2+ After doping, the binding energy tends to decrease. As shown in Figure (B), the O-XPS plot reveals two binding energy peaks at 529 eV and 531.6 eV, which are attributed to lattice oxygen and defect oxygen in Gd₂O₃, respectively. (Zn doping...) 2+ Subsequently, both O1s peaks of Gd₂O₃ NPs shifted towards lower binding energies, consistent with the conclusion drawn in Figure (A). Figure (C) shows that the peaks at 1021.8 eV and 1045.1 eV correspond to Zn 2p⁻¹, respectively. 3 / 2 and Zn 2p 1 / 2 As the doping ratio increases, Zn 2p 3 / 2 and Zn 2p 1 / 2 The peak intensity of Zn steadily increases, indicating that... 2+ The successful incorporation of Zn into Gd₂O₃NPs also indicates that Zn 2+ They exist as +2 valent ions, and the different doping ratios also cause slight peak shifts. Figure (D) shows the total spectrum of Zn-Gd2O3 NPs. As can be seen from the XPS total spectrum, the peak positions are consistent with those in Figures (A), (B), and (C), further proving that the prepared samples are Zn-Gd2O3 NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%).

[0035] Zn 2+ Doping can modulate the E of Gd2O3 NPs g .like Figure 5 As shown, in Zn 2+ After doping, E g Both are lower than those of Gd2O3 NPs, and the smaller E g This can further facilitate electronic transitions, thus satisfying the CT effect. The Et values ​​of Zn-Gd2O3 NPs with different doping ratios (0%, 0.5%, 1%, 3%, and 5%) were calculated. g The E values ​​were 4.5 eV, 4.31 eV, 3.97 eV, 4.25 eV, and 4.36 eV, respectively. The E values ​​for Zn-Gd₂O₃ NPs with a doping ratio of 1% were... g The minimum energy required for electrons in Zn-Gd2O3 NPs with a doping ratio of 1% to transition from CB to VB is the minimum, making it easier to trigger the CT effect.

[0036] According to the SERS detection results above, Zn-Gd2O3NPs with a doping ratio of 1% showed the best enhancement effect on the SERS signal. Therefore, it was selected as the substrate to detect four drug molecules (enrofloxacin (ENR), norfloxacin (NOR), ciprofloxacin (LEV), and levofloxacin (CIP)). Figure 6 The results show that using Zn-Gd2O3 NPs with a doping ratio of 1% as a substrate, the adsorption of drug molecules at a concentration of 10... -3 -10 -7 mol / LSERS spectra and Raman spectra of Zn-Gd₂O₃ NPs with a doping ratio of 1%. The figures show that the peak positions of the four drug molecules did not shift significantly compared to previous analyses, remaining at 1387, 1393, 1397, and 1383 cm⁻¹. -1 The characteristic peaks at these locations were attributed to ENR, NOR, LEV, and CIP, respectively. This is in contrast to previously reported Gd₂O₃ NPs (Comparative Example 1, lowest detectable concentration of 10). -5 The lowest Zn-Gd₂O₃ NPs can be as low as 10 mol / L. -6 The detection of NOR at a concentration of mol / L proves that Zn-Gd2O3 NPs can more accurately detect low concentrations of NOR, providing a more powerful SERS detection substrate for food safety, environmental pollution and other aspects.

Claims

1. A zinc ion-containing gadolinium oxide composite material for use on a SERS substrate, characterized in that... The composite material uses gadolinium oxide as the matrix and zinc as the ionic dopant, and its chemical formula is Zn-Gd2O3 NPs.

2. The zinc-ion-containing gadolinium oxide composite material for SERS substrates according to claim 1, characterized in that... Prepared according to the following method: Step 1: Place Gd₂O₃ and different masses of ZnCl₂ into separate beakers. Then add 5 ml of nitric acid and sonicate until completely dissolved. Next, heat to evaporate the solution until a white powder precipitates. Step 2: Add ethylene glycol and polyethylene glycol to the solution, stir well, then add sodium hydroxide ethylene glycol solution dropwise to adjust the temperature. Then transfer the solution to the reaction vessel and react under heating conditions for a period of time. After the reaction is cooled naturally at a constant temperature, centrifuge the solution, wash it several times with deionized water and ethanol, and then dry it under vacuum drying conditions at 50°C. Step 3: After grinding, calcine at high temperature for 4 h to obtain Zn-Gd2O3NPS.

3. The method for preparing a zinc ion-containing gadolinium oxide composite material for a SERS substrate according to claim 2, characterized in that... In step one, the mass range of ZnCl2 is 0.001 g to 0.0102 g.

4. The method for preparing a zinc ion-containing gadolinium oxide composite material for a SERS substrate according to claim 2, characterized in that... In step two, the volume of the reaction vessel is 50 mL.

5. The method for preparing a zinc ion-containing gadolinium oxide composite material for a SERS substrate according to claim 2, characterized in that... In step two, the molecular weight of polyethylene glycol is 200-600.

6. The method for preparing a zinc ion-containing gadolinium oxide composite material for a SERS substrate according to claim 2, characterized in that... In step two, the heating temperature of the reactor is 100°C to 120°C, and the reaction time is 4 to 8 hours.

7. The method for preparing a zinc ion-containing gadolinium oxide composite material for a SERS substrate according to claim 2, characterized in that... The pH range of the milky white mixture in step two is 8 to 10.

8. The method for preparing a zinc ion-containing gadolinium oxide composite material for a SERS substrate according to claim 2, characterized in that... In step three, the heating temperature of the reactor is 550~600°C.

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