Project 4 Advanced Approaches to Quantifying Exposure to Heavy Metals

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Environmental/Engineering: Project #4. Advanced approaches to quantifying exposure to heavy metals Project Summary Historic and ongoing air, water, and soil pollution in North Birmingham results in area contamination with heavy metals and other toxic compounds and poses high health risk in the neighborhood. Analytical techniques for heavy metal (HM) detection are essential for understanding mechanisms of HM induced lung injury and efficiency of mechanical and chemical remediation of pollution. Majority of current analytical techniques for HM detection such as Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) and Atomic Absorption Spectrophotometry (AAS) are not portable, require large amount of sample (ICP-MS), not always sufficiently sensitive, slow, and require advanced procedures for sample preparation. Our hypothesis is that development of a novel femto-LIBS (laser induced breakdown spectroscopy)/ LEAFS (laser excited atomic fluorescence spectroscopy) and middle infrared frequency comb “Optical Nose” systems will enable ultrasensitive and rapid detection of Cd, Mn, As, and biomarkers associated with exposure to these metals. LIBS is a rapid, real-time analytical technique based on the analysis of the spectral emission from laser induced sparks. The method enables fast and sensitive chemical analysis of any kind of matter (solid, liquid or gas) without sample preparation. Detection limits for LIBS using nanosecond laser pulses are typically in ppms for HMs. Excitation using laser pulses with femtosecond (fs) duration (f-LIBS) may provide significant improvement in detection limit. Our group recently demonstrated breakthrough in development of fs lasers based on chromium doped ZnS/Se crystals and showed that these systems feature several essential advantages for fs laser spectroscopy applications. These lasers will be a foundation for two f-LIBS platforms (for bulk and microscopic samples). For the applications where ppb/ppt sensitivity is required we will combine f-LIBS platform with LEAFS enabling superior sensitivity (sub-ppt) similar to prototypes developed earlier by our group. Our objective will be also to extend current visible-near IR frequency-comb techniques to molecules “fingerprint” mid-IR spectral range. This optical nose platform to be developed will be based on a dual-comb Fourier-transform spectroscopy with fs oscillators emitting in the mid-IR based on our recent breakthrough in fs lasers and their frequency down-conversion. The plan includes the development of 2-20 μm frequency combs on the basis of Cr:ZnS/Se fs laser and its intra-pulse difference frequency generation using ZnGeP2, GaSe, and/or orientation patterned GaP nonlinear crystals. This planned instrument will provide a real time total profile of the trace gas contents in complex gas mixtures and will be offered to other projects of the proposal for sensing biomarkers associated with HM exposure.