| The persistent toxic substances (PTS), which have environmental persistence and toxic effects such as carcinogenicity and endocrine disruption, are widely distributed in the nature. They are severely harmful to human health and environment. The traditional analytical methods for the monitoring of PTS including fluorescence spectroscopy, gas chromatography (GC) coupled with mass spectrometry or electron capture detectors (GC-MS or GC-ECD) and high-performance liquid chromatography (HPLC) coupled with UV or MS, generally require complicated sample preparation process. It is quite important to develop a convenient and rapid analytical method.Surface-enhanced Raman spectroscopy (SERS), which could give fingerprint spectra for most molecules, is widely applied in the field of environment analysis. High enhancement substrate is of great importance for practical application of SERS technique. Generally, an ideal substrate needs high sensitivity, temporal stability, uniformity and reproducibility. A "clean" surface is also an essential parameter for ultrasensitive detection. SERS signals decay exponentially accordingly to the distance from SERS substrate. In order to obtain repeatable SERS signals, target molecules should be efficiently enriched on the surface of substrate. An ideal SERS sensor would also have good reproducibility via efficient desorption method. PTS are widely found in environment, such as air, earth and water. Methods based on SERS show its potential for practical detection of PTS in different environment media.In this paper, hydrophobic gold nanostructures have been fabricated via a facile potentiostatic electrodeposition method as SERS substrates for direct detection of PTS with a portable Raman spectrometer. Furthmore, a combination of headspace (HS) sampling and SERS has been developed for in situ detection of environmental contaminants.1. Hydrophobic gold nanostructures via electrochemical deposition for sensitive SERS detection of persistent toxic substancesElectrodeposition has been introduced to obtain noble metal nanostructures as effective SERS substrate. Herein, hydrophobic gold nanostructures fabricated by the electrochemical deposition process were used as effective SERS substrates to detect PTS, such as PAHs, PBDEs, PCBs. Reliable data could be acquired from the portable Raman spectrometer within just a few seconds. The contact angle changed from 77° to 123° with extension of the deposition time, indicating the wetting property of the surface changed from hydrophilicity to hydrophobicity. The substrate has greater temporal stability and good uniformity, indicating that the substrate could provide reliable signals. Quantitative SERS detection of PTS has been achieved, because the log-log plot of SERS intensity to PTS concentration exhibited a good linear relationship, with the detection limits of 6.7 nmol L-1,2.6 nmol L-1 and 5.3 nmol L-1, respectively. The prepared substrate could be used as a potential SERS sensor for trace level detection of hydrophobic contaminants in the environment.2. In situ detection via headspace surface-enhanced Raman spectroscopy with recyclable substratesPTS widely exists in environment, such as air, earth and water. We have developed a feasible method which combines HS sampling and SERS measurement to achieve rapid enrichment of analytes and in situ detection. The capability of the HS-SERS procedure for the qualitative and quantitative analysis of PAHs was exampled by fluoranthene. The log-log plot of SERS intensity of fluoranthene versus concentration exhibits a good linear relationship, with the range of 1-200 μmol L-1. Moreover, the SERS-active substrate was characterized by high reproducibility through sodium borohydride washing. It is suggested that the headspace-SERS technique may offer a great potential for environmental analysis. |
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