Optical detection of aromatic water-contaminants from petroleum or industrial spills is challenging due to background signals from natural and/or man-made components. Further, while target contaminants are regulated at microgram per liter (μg/L) levels, conventional Raman, FTIR and UV-VIS spectroscopy are generally limited to milligram per liter (mg/L) detection ranges. This study reports on patented A-TEEM spectroscopy which primarily uses fluorescence excitation emission matrix data that are corrected for inner-filter effects (IFE) to eliminate spectral distortion. IFE correction improves resolution of low concentration contaminants from higher concentration backgrounds. The multidimensional ATEEM dataset contains spectral information in the UV-VIS range for all chromophoric and fluorescent compounds in the sample matrix. Nevertheless, because the spectra of many compounds overlap or vary in intensity extracting qualitative and quantitative information generally requires multivariate analyses. Importantly, the UV-VIS and EEM data can be analyzed in a ‘multi-block’ format to leverage the resolution capacity of these simultaneously acquired independent data sets. We evaluated Benzene, Toluene, Ethylbenzene and Xylene (BTEX) as well as naphthalene in filtered (0.45 μm) raw surface water before drinking water treatment. We show that typical methods including Partial Least Squares (PLS) and Parallel Factor Analysis (PARAFAC) exhibit a variety of pitfalls that can confound accurate contaminant detection and quantification. We report that classification and regression using methods including Support Vector Machine (SVM) and especially XGradient Boost (XGB) algorithms can be more effectively validated to rapidly yield lower μg/L detection limits with potential to automate early-warning reporting.
Global drinking water sources remain prone to carcinogenic petroleum product contaminations due to lack of detection capacity at or before treatment plant intake. A major challenge to detect water-soluble petroleum products using optical techniques is discrimination of low contaminant quantities from the highly absorbing and fluorescent backgrounds of natural Dissolved Organic Matter (DOM) components. One key example is Benzene subject to a USEPA regulation maximum contaminant level in the distribution system of 5 μg/L. In contrast, typical surface water DOM concentrations range from 1 to 20 mg/L and many DOM components have much higher extinction and fluorescent quantum yields than Benzene, Toluene, Ethylbenzene and Xylene (collectively known as BTEX). We present a new optical method for rapid (3-5 min) reagent- and extraction-free detection of all BTEX compounds in typical raw surface water with respective Limits of Detection (LOD) and Quantification (LOQ) of 1 and 3 μg/L. The method uses patented simultaneous Absorbance, Transmission and fluorescence Excitation-Emission Mapping (A-TEEM) instrument technology with deep UV sensitivity. The rapid acquisition is supported by automated, targeted Partial Least Squares (PLS) library analysis. The instrument can be equipped with an automated surface water flow-sampling device at the plant intake or upstream and internet based communication to facilitate early warning reports.
This presentation describes several important applications of steady-state and time-resolved photoluminescence (PL)
instrumentation in the field of nanophotonics. The paper presents a cohesive overview of PL instrument configurations
and data analysis methods pertaining to each of the described nanophotonics applications. Key nanomaterials in the
nanophotonics field include carbon nanotubes, organic light-emitting diodes and quantum dots. Highlighted carbon
nanotube applications focus on the steady state excitation-emission matrix analyses of the semiconducting properties of
single-walled nanotubes (SWNTs); these properties are relevant to the implementation of SWNTs in nanophotonics
circuitry and high-definition display technology. Quantum dots (QDOTS) are also becoming increasingly important for
nanophotonics applications including steady state and time-resolved measurements pertaining to biosensing, tunable
bandgap circuitry and cancer imaging-diagnostics. Organic light emitting diodes (OLEDS) are now also recognized for
their potential uses in novel display technology and time-resolved PL applications are described as key tools in the
OLED research and development arena. The presentation will conclude with a summary of the perceived future of the
industrial applications and scientific progress in developing areas of nanophotonics PL.
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