Rapid and Direct Analysis of Samples of Environmental Concerns

Despite extensive efforts to protect public health, disease outbreaks still occur when toxic chemicals and microbial threats evade detection. Though numerous techniques are available for contaminant detection in a variety of matrices, they are either laborious, costly or specifically adapted to a certain class of analysts. Thus, it is imperative to develop novel approaches for simple, fast, inexpensive and reliable methods to screen/characterize single and/or multiple contaminant classes sensitively. Surface enhanced Raman scattering (SERS) has proved its ability in rapid and sensitive chemical sensing in the last several decades. The development of novel, highly efficient and reliable SERS substrates is critical for its environmental applications. On the other hand, as one of the most important ambient ionization techniques, direct analysis in real time (DART) mass spectrometry (MS) enables rapid screening of a large variety of samples including less polar molecules without any sample pretreatment. However, rapid screening of steroid hormones in the aquatic environment using DART MS has not been studied yet. Meanwhile, nonlinear optical (NLO) imaging techniques have emerged as promising imaging methods due to their relatively large optical penetration, inherent three-dimensional (3D) spatial resolution and reduced photo-damage compared with linear optical microscopy. However, exogenous labels are usually needed for non-signal targets analysis, and they either undergo photobleaching or involve with a complicated labelling process. In this dissertation, 1) an efficient novel SERS substrate based on the direct photoredution of silver nanoparticles (NPs) onto Molybdenum disulfide (MoS2) surface was developed and trace Rhodamine 6G (R6G) was tested as a probe molecule. 2) Rapid screening of testosterone (TES) in the aquatic environment using DART MS was conducted. 3) A novel one-step in-situ labelling approach for real-time imaging of potato cells using silver NPs assisted multimodal NLO microscopy was developed. Results indicate that R6G, TES in the real wastewater samples and potato cells as reprehensive plant cells could be rapidly and directly analyzed/imaged by the developed simple approaches