School of Science, RMIT University, GPO 2476, Melbourne, VIC 3000, Australia.
Australian Centre for Research on Separation Science, School of Science, RMIT University, Bundoora West Campus, PO Box 71, Bundoora, VIC 3083, Australia.
Sci Total Environ. 2020 Jun 10;720:137601. doi: 10.1016/j.scitotenv.2020.137601. Epub 2020 Feb 27.
Environmental pollution is usually monitored via mass spectrometry-based approaches. Such techniques are extremely sensitive but have several disadvantages. The instruments themselves are expensive, require specialized training to use and usually cannot be taken into the field. Samples also usually require extensive pre-treatment prior to analysis which can affect the final result. The development of analytical methods that matched the sensitively of mass spectrometry but that could be deployed in the field and require minimal sample processing would be highly advantageous for environmental monitoring. One method that may meet these criteria is Surface Enhanced Raman Spectroscopy (SERS). This is a surface-sensitive technique that enhances Raman scattering by molecules adsorbed on rough nanostructure surfaces such as gold or silver nanoparticles. SERS gives selective spectral enhancement such that increases in sensitivity of 10 to 10 have been reported. While this means SERS is, theoretically at least, capable of single molecule detection such a signal enhancement is hard to achieve in practice. In this review the background of SERS is introduced for the environmental scientist and the recent literature on the detection of several classes of environmental pollutants using this technique is discussed. For heavy metals the lowest limit of detection reported was 0.45 μg/L for Mercury; for pharmaceuticals, 2.4 μg/L for propranolol; for endocrine disruptors, 0.35 μg/L for 17β-estradiol; for perfluorinated compounds, 500 μg/L for perfluorooctanoic acid and for inorganic pollutants, 37g/L for general pesticide markers. The signal enhancements achieved in each case show great promise for the detection of pollutants at environmentally relevant concentrations and, although it does not yet routinely match the sensitivity of mass spectrometry. Further work to develop SERS methods and apply them for the detection of contaminants could be of wide benefit for environmental science.
环境污染通常通过基于质谱的方法进行监测。这些技术非常灵敏，但也有几个缺点。仪器本身价格昂贵，使用需要专门的培训，通常不能带到现场。样品在分析前通常需要广泛的预处理，这可能会影响最终结果。开发灵敏度与质谱相当但可以在现场部署且需要最小样品处理的分析方法，将对环境监测非常有利。一种可能符合这些标准的方法是表面增强拉曼光谱（SERS）。这是一种表面敏感的技术，通过吸附在粗糙纳米结构表面（如金或银纳米粒子）上的分子增强拉曼散射。SERS 提供选择性光谱增强，据报道灵敏度提高了 10 到 10。虽然这意味着 SERS 理论上至少能够进行单分子检测，但实际上很难实现这种信号增强。在这篇综述中，为环境科学家介绍了 SERS 的背景，并讨论了最近使用该技术检测几类环境污染物的文献。对于重金属，报道的最低检测限为汞 0.45μg/L；对于药物，普萘洛尔 2.4μg/L；对于内分泌干扰物，17β-雌二醇 0.35μg/L；对于全氟化合物，全氟辛酸 500μg/L；对于无机污染物，一般农药标志物 37g/L。在每种情况下实现的信号增强都为在环境相关浓度下检测污染物提供了很大的希望，尽管它还没有达到质谱的灵敏度。进一步开发 SERS 方法并将其应用于污染物检测的工作可能会给环境科学带来广泛的益处。
