研究目的
Developing a cysteamine-modified SERS substrate for sensitive and reproducible detection of trace amounts of acidic pigments with weak surface affinity to gold nanoparticles.
研究成果
The cysteamine-modified SERS substrate enables sensitive, reproducible, and universal detection of acidic pigments with weak affinity to gold nanoparticles, achieving a low LOD of 1 ppm. It offers advantages of simple preparation, high stability, and applicability to real samples, providing a promising platform for food safety monitoring.
研究不足
The method may be limited by the specificity of the hydrogen bonding and electrostatic interactions, which could be affected by other molecules in complex samples. The substrate's performance might vary with different surfactants or nanoparticle shapes, and the pre-treatment step for real samples adds complexity.
1：Experimental Design and Method Selection:
The study involves synthesizing PVP-coated gold nanoparticles (PVP-Au NPs) via seed growth method, modifying them with cysteamine (CA) to create CA-Au NPs substrates for SERS detection. The rationale is to use CA to facilitate the adsorption of acidic pigments through hydrogen bonding and electrostatic interactions, enhancing Raman signals.
2：Sample Selection and Data Sources:
Five acidic pigments (amaranth, sunset yellow, allura red, lemon yellow, acid blue) were purchased from Sigma-Aldrich. Real beverage samples were bought from a local supermarket and pre-treated using polyamide powder for pigment extraction.
3：List of Experimental Equipment and Materials:
Materials include PVP (MW=55000), NH2OH·HCl, sodium citrate, HAuCl4·4H2O, cysteamine (CA), polyamide powder, ammonia aqueous solution, and ultrapure water. Equipment includes a peristaltic pump for injection, centrifuge for washing, and various instruments for characterization and measurement.
4：Experimental Procedures and Operational Workflow:
Synthesis of PVP-Au NPs involves reducing HAuCl4 with sodium citrate and growing with PVP and NH2OH·HCl. Modification with CA involves centrifuging PVP-Au NPs, washing, mixing with CA solution, vibrating, and centrifuging again. For SERS measurement, 1 μL of CA-modified Au NPs is dropped on a Si wafer, dried, and 1 μL of pigment sample is added. Raman spectra are collected using a LabRAM HR800 system with a 633 nm laser.
5：Data Analysis Methods:
SERS spectra are analyzed to identify characteristic peaks of pigments. Sensitivity is evaluated by limit of detection (LOD), reproducibility by relative standard deviation (RSD) of peak intensities, and universality by testing multiple pigments. Stability is assessed over time.
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UV-2600 spectrophotometer
UV-2600
Shimadzu
Used to obtain ultraviolet-visible (UV–vis) absorption spectra.
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LabRAM HR800 confocal microscope Raman system
HR800
Horiba JobinYvon
Used for SERS measurements to collect Raman spectra of samples.
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field-emission scanning electron microscope
SIGMA 500
Used to obtain scanning electron microscopy images of nanoparticles.
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X-ray Photoelectron Spectroscopy
PHI 5000 VersaProbe IIv
Used for XPS measurements to analyze surface composition.
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peristaltic pump
Used to inject HAuCl4 solution at a controlled speed during nanoparticle synthesis.
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centrifuge
Used to centrifuge nanoparticle solutions for washing and separation.
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filter membrane
Used in the pre-treatment of real samples for pigment extraction.
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