Crop Disease Spore Detection Method Based on Au@Ag NRS
Abstract
1. Introduction
2. Materials and Methods
2.1. Laboratory Reagents
2.2. Synthesis Method of Au@Ag NRS
2.2.1. Synthesis of Au NRS
- Synthesis of Gold Seeds. In a constant-temperature water bath with magnetic stirring, 8 mL of 0.1 mol/L CTAB (Hexadecyl Trimethyl Ammonium Bromide) aqueous solution was added to a glass vial containing a magnetic stir bar. Under stirring at 640 r/min, 200 μL of 0.01 mol/L Chloroauric Acid (HAuCl4) aqueous solution was slowly added, resulting in a golden-yellow color. The stirring speed was then increased to 1200 r/min, and 480 μL of ice-cold 0.1 mol/L Sodium Borohydride (NaBH4) solution (stored at 0–4 °C) was added, turning the solution brownish yellow. After thorough mixing, the reaction mixture was statically incubated at 30 °C for 2 h in an oven, yielding a tea-brown gold seed solution.
- Preparation of Growth Solution. To 20 mL of 0.1 mol/L CTAB aqueous solution, the following reagents were sequentially added: ① 1 mL of 0.01 mol/L HAuCl4 aqueous solution, ② 250 μL of 0.01 mol/L Silver Nitrate (AgNO3) aqueous solution, ③ 34 μL of 38% Hydrochloric Acid (HCl) aqueous solution (shifting the color to khaki), ④ 160 μL of 0.1 mol/L Ascorbic Acid (AA) aqueous solution, ⑤ The mixture was stirred at 1200 r/min for 30 s, resulting in a colorless transparent growth solution.
- Growth of Au NRS. 10 μL of the gold seed solution was added to the growth solution and stirred at 700 r/min for 1 min. The mixture was then statically reacted at 30 °C for 12 h in an oven.
- Centrifugal Washing. After reaction completion, centrifugal washing was performed to remove excess CTAB and AgNO3 impurities: ① Centrifugation at 10,000 r/min for 10 min (with centrifuge tubes symmetrically placed), ② The supernatant was discarded, and the pellet was resuspended in 15 mL of ultrapure water, ③ The colloid was ultrasonicated for 5 min to ensure homogeneous dispersion, ④ This washing cycle was repeated multiple times with minimal solvent volume, ⑤ the colloid was concentrated to 5 mL and stored at 4 °C.
2.2.2. Synthesis of Au@Ag NRS
- Add 600 μL of 0.08 mol/L CTAC (Cetyltrimethylammonium Chloride) solution to a 10 mL centrifuge tube, followed by 200 μL of 0.01 mol/L Silver Nitrate (AgNO3) aqueous solution. Oscillate the mixture for homogenization and incubate at 30 °C for 10 min.
- Remove the mixture from the oven, add 500 μL of concentrated Au NRS solution and 2 mL of ultrapure water. Oscillate for homogenization and incubate at 30 °C for 5 min.
- Add 100 μL of 0.1 mol/L Ascorbic Acid (AA) solution to the mixture. Oscillate vigorously at 1000 r/min for 1 min, then react in a constant-temperature oscillating water bath at 30 °C for 4 h.
2.3. SERS-Based Detection Method for Crop Disease Spores
2.4. SERS Spectral Analysis of Crop Disease Spores
2.5. MLP Classification of Pathogenic Spores
3. Results and Discussion
3.1. Analysis of Preparation Results for Au NRS and Au@Ag NRS
3.1.1. Effect of Different Concentrations on Au NRS Formation
3.1.2. Synthesis Analysis of Au@Ag NRS
3.1.3. EDS Analysis of Au@Ag Core-Shell Structures
3.1.4. R6G Detection Using Au@Ag NRS
3.2. SERS Spectral Analysis Results of Crop Disease Spores
3.2.1. Spectral Smoothing
3.2.2. Spectral Standardization
3.2.3. Baseline Correction of Spectral Data for Crop Disease Spores
3.3. Analysis of SERS Fingerprint Information for Crop Diseases
3.4. Classification of SERS Spectra
3.4.1. Dimensionality Reduction of SERS Spectra
3.4.2. SERS Spectrum Classification Model
4. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Reagent Name | CAS |
---|---|
Hexadecyl trimethyl ammonium Bromide (CTAB) | 57-09-0 |
Hydrogen tetrachloroaurate (III) trihydrate | 16961-25-4 |
Sodium borohydride | 16940-66-2 |
Ascorbic acid | 50-81-7 |
Silver nitrate | 7761-88-8 |
Hydrochloric acid | 7647-01-0 |
Sulfuric acid | 7664-93-9 |
Cetyltrimethylammonium chloride (CTAC) | 112-02-7 |
Group | /μL | CTAB/mL |
---|---|---|
1 | 150 | 20 |
2 | 250 | 20 |
3 | 350 | 20 |
Element | Line Type | k Factor | k Factor Type | Absorption Correction | Wt% | Wt% Sigma |
---|---|---|---|---|---|---|
C | K series | 2.760 | Theoretical | 1.00 | 30.30 | 0.26 |
O | K series | 2.013 | Theoretical | 1.00 | 2.76 | 0.08 |
Si | K series | 1.000 | Theoretical | 1.00 | 3.03 | 0.07 |
Cr | K series | 1.117 | Theoretical | 1.00 | 0.24 | 0.03 |
Fe | K series | 1.150 | Theoretical | 1.00 | 0.15 | 0.03 |
Co | K series | 1.194 | Theoretical | 1.00 | 0.21 | 0.03 |
Cu | K series | 1.261 | Theoretical | 1.00 | 18.46 | 0.17 |
Ag | K series | 11.157 | Theoretical | 1.00 | 9.89 | 0.42 |
Os | L series | 2.261 | Theoretical | 1.00 | 1.12 | 0.17 |
Au | L series | 2.325 | Theoretical | 1.00 | 33.83 | 0.30 |
Raman Shift | Fusarium oxysporum | Rice False Smut | Aspergillus niger | Spectral Assignment | References |
---|---|---|---|---|---|
469–481 | 481 | 469 | 480 | Galactomannan, Chitin | [25] |
675–684 | 675 | 684 | 680 | Guanine, Thymine (Hydrogen-Bonded Ring) | [25,33] |
785 | - | - | 785 | L-Histidine | [34] |
835 | 853 | 835 | - | O-P-O Rotation in RNA | [33] |
1004–1008 | 1008 | 1004 | 1004 | Phenylalanine | [33] |
1104–1117 | 1104 | - | 1117 | Galactomannan | [25] |
1133–1148 | 1148 | 1133 | 1133 | C-O Ring Aromatic Amino Acids in Proteins | [12] |
1257–1260 | 1260 | 1260 | 1257 | Amide III (Random), Thymine | [33,35] |
1386–1391 | 1386 | 1391 | 1391 | D-Galactosamine | [34] |
1457–1472 | 1464 | 1457 | 1472 | L-Histidine | [34] |
1564–1580 | 1580 | 1574 | 1564 | Adenine, Guanine (Ring Stretching Vibration) | [12,35] |
1713–1718 | 1716 | 1718 | 1713 | L-Arginine in Proteins | [34] |
Number | Combination | TP | TN | FP | FN | Training Set Accuracy (%) | Test Set Accuracy (%) |
---|---|---|---|---|---|---|---|
1 | SVM | 45 | 17 | 5 | 5 | 86.65 | 86.32 |
2 | MPL | 46 | 17 | 5 | 4 | 88.46 | 87.61 |
3 | PCA-SVM | 49 | 20 | 2 | 1 | 97.25 | 95.24 |
4 | PCA-MPL | 49 | 21 | 1 | 1 | 97.34 | 96.55 |
5 | SCARS-SVM | 49 | 20 | 2 | 1 | 97.37 | 95.83 |
6 | SCARS-MLP | 50 | 21 | 1 | 0 | 98.9 | 97.92 |
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Zhang, Y.; Guo, J.; Bian, F.; Li, Z.; Guo, C.; Zheng, J.; Zhang, X. Crop Disease Spore Detection Method Based on Au@Ag NRS. Agriculture 2025, 15, 2076. https://doi.org/10.3390/agriculture15192076
Zhang Y, Guo J, Bian F, Li Z, Guo C, Zheng J, Zhang X. Crop Disease Spore Detection Method Based on Au@Ag NRS. Agriculture. 2025; 15(19):2076. https://doi.org/10.3390/agriculture15192076
Chicago/Turabian StyleZhang, Yixue, Jili Guo, Fei Bian, Zhaowei Li, Chuandong Guo, Jialiang Zheng, and Xiaodong Zhang. 2025. "Crop Disease Spore Detection Method Based on Au@Ag NRS" Agriculture 15, no. 19: 2076. https://doi.org/10.3390/agriculture15192076
APA StyleZhang, Y., Guo, J., Bian, F., Li, Z., Guo, C., Zheng, J., & Zhang, X. (2025). Crop Disease Spore Detection Method Based on Au@Ag NRS. Agriculture, 15(19), 2076. https://doi.org/10.3390/agriculture15192076