Recent Progress on the Detection of Dioxins Based on Surface-enhanced Raman Spectroscopy

Abstract

Persistent Organic Pollutants (POPs), represented by dioxins and dioxin-like polychlorinated biphenyls have the property of teratogenic, carcinogenic and mutagenic, which have been classified as Group A human carcinogen by the international agency for research on cancer (IARC) and put into the initial list of Stockholm Convention managed by the United Nations Environment Program. POPs have posed a threat and impact on food security through the food chain from environment. The conventional detection methods, such as liquid chromatography-tandem mass spectrometry, high resolution gas chromatography-mass spectrometry and two-dimensional gas chromatography with time-of-flight mass spectrometry are sufficiently accurate, but fail to meet the requirements of on-site detection. Meanwhile, the rapid testing technologies for PCBs mainly included fluorescence detection, electrochemical sensors, and so on. As a new type of rapid detection technology, Surface-enhanced Raman Spectroscopy (SERS) has attracted significant attention as a promising analytical technique. With its ultra-sensitivity, high speed detection, ease of operation, SERS is particularly well-suited for the rapid detection of POPs. However, the multiple molecules in matrices may generate interfering Raman signals via competitive adsorption with the target compound on the substrate surface in the SERS detection of real samples. In addition, reproducibility represents a major bottleneck for the widespread application of SERS. Metal nanoparticle colloids are widely used as SERS substrates due to the hot spots formed between the nanoparticles. However, metal nanoparticle aggregation in colloidal solutions is difficult to control, leading to the random formation of hot spots. When the target POPs exist near the hot spots, the intensities of the enhanced Raman signals were unstable. Other factors influenced by the chemical adsorption such as vibration, charge transfer, and the deformation or distortion of molecules also affect the Raman signals. In the review, we provide an overview of the recent advances in SERS for POPs determination, especially the different types of enhanced substrates. And several key technical points of SERS detection including sensitivity, selectivity, and reproducibility have been summarized. Finally, the development of SERS for POPs detection in the future are proposed.