High-Performance SERS Detection of Dye Contaminants Using Novel Functionalized Carbon Dots

Academic Background

Dye molecules play a vital role in daily life, but the environmental pollution caused by their use cannot be ignored. Among them, Malachite Green (MG) is a triphenylmethane dye with potential carcinogenic, teratogenic, and mutagenic effects. Although MG is widely used in aquaculture to treat fungal and parasitic infections in fish, due to its high toxicity and residue issues, many countries have explicitly banned its use. However, there is a lack of cheap and effective alternatives on the market, so the use of MG has not been completely stopped. To monitor its trace presence in complex biological environments, there is an urgent need for a highly sensitive and selective detection technique.

Traditional detection methods, such as High-Performance Liquid Chromatography (HPLC) and Capillary Electrophoresis Raman Spectroscopy (CE-RS), while highly accurate, suffer from cumbersome sample pretreatment, time-consuming processes, and high costs. Surface-Enhanced Raman Scattering (SERS), as an ultra-sensitive analytical technique, can amplify Raman signals by a factor of 10^10 to 10^11 at the single-molecule level, offering significant application potential. This study aims to develop a novel SERS substrate for the efficient and sensitive detection of MG, providing technical support for applications in environmental and food safety fields.

Source of the Paper

This paper was co-authored by Yanqiu Yang, Lingru Kong, Yong Ding, Lixin Xia, Shuo Cao, and Peng Song. The authors are affiliated with the Department of Physics and Chemistry at Liaoning University and Yingkou Institute of Technology. The research was published in Journal of Advanced Research (Volume 68, 2025, pp. 89-98) and officially released on February 9, 2024. The study was supported by multiple National Natural Science Foundation of China projects and Liaoning Provincial Department of Education projects.

Research Process

1. Construction of the Novel Ag-CDs-PBA Nanocomposite

The research first prepared Carbon Dots (CDs) using a hydrothermal method and purified them through dialysis. Subsequently, CDs powder was immersed in a Phenyl Boric Acid (PBA) solution to form a CDs-PBA complex. Next, silver nanoparticles (Ag NPs) were modified on the surface of the CDs-PBA complex by reducing silver nitrate (AgNO3), ultimately yielding the Ag-CDs-PBA composite material. To verify its performance, Ag-CDs were also prepared as a control sample.

2. Experimental Design for SERS Detection of MG

The experimental subjects included freshwater fish and actual water samples. First, live fish were exposed to MG solutions of different concentrations and soaked for two days before extracting fish tissue samples. Actual water samples were collected from the Hunhe River basin and industrial wastewater, filtered, and spiked with different concentrations of MG. All samples were subjected to SERS detection using the Ag-CDs-PBA substrate, and Raman spectra were recorded.

3. Material Characterization and Performance Testing

The morphology and crystal structure of Ag-CDs-PBA were characterized using Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) were used to analyze the surface chemical composition of the material. Raman spectroscopy was employed to evaluate the enhancement effect of the SERS substrate, and Density Functional Theory (DFT) calculations revealed the charge transfer mechanism between CDs and PBA.

Key Results

1. Material Characterization Results

TEM images showed that Ag NPs were uniformly distributed on the surface of the CDs, with a particle size of about 40 nm, while the diameter of the CDs ranged from 2 to 6 nm. XRD analysis indicated that the Ag-CDs-PBA composite had high crystallinity, and the presence of silver nanoparticles significantly enhanced the material’s stability. FTIR and XPS results showed that the introduction of PBA significantly altered the surface functional groups of the CDs, enhancing the interaction between the material and target molecules.

2. SERS Performance Evaluation

The experiments demonstrated that the Ag-CDs-PBA substrate had extremely high sensitivity and selectivity for MG detection. At a concentration of 10^-10 M MG, the characteristic Raman peaks were still clearly observed, indicating excellent detection performance. Furthermore, DFT calculations confirmed the strong charge transfer effect between CDs and PBA, further explaining the mechanism of SERS signal enhancement.

3. Practical Application Testing

The Ag-CDs-PBA substrate successfully detected trace amounts of MG in actual water samples, with recovery rates ranging from 94.10% to 108.45%, demonstrating its potential in complex environments. Additionally, the substrate maintained good SERS activity after multiple cycles of use, exhibiting excellent stability and repeatability.

Conclusion and Significance

This study successfully constructed a novel Ag-CDs-PBA SERS substrate, achieving highly sensitive and selective detection of Malachite Green. By regulating the charge transfer effect between CDs and PBA, the study significantly improved the SERS performance of the substrate and provided a new technical means for detecting trace pollutants in complex environments. This research not only has significant scientific value but also demonstrates broad application prospects in the fields of environmental and food safety.

Research Highlights

1. High Sensitivity: The Ag-CDs-PBA substrate can detect MG at an extremely low concentration of 10^-10 M, showcasing exceptional detection performance.
2. Strong Selectivity: The introduction of PBA effectively suppresses the influence of other interfering substances, enabling specific recognition of target molecules.
3. Practical Application: The study successfully applied the substrate to the detection of actual water and fish samples, verifying its applicability in complex environments.
4. Innovation: DFT calculations revealed the charge transfer mechanism between CDs and PBA, providing theoretical support for SERS signal enhancement.

Other Valuable Information

The research also explored the application of the Ag-CDs-PBA substrate in the detection of other dye molecules (e.g., Rhodamine 6G, Crystal Violet), further expanding its application scope. Additionally, the long-term stability and self-cleaning properties of the substrate provide strong support for its application in practical production.