Department of Chemistry and Biochemistry
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Browsing Department of Chemistry and Biochemistry by Author "Booksh, Karl"
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Item Authentication of edible oils using an infrared spectral library and digital sample sets: A feasibility study(Journal of Chemometrics, 2023-03-19) Sota-Uba, Isio; White, Collin G.; Booksh, Karl; Lavine, Barry K.A potential method to determine whether two varieties of edible oils can be differentiated by Fourier transform infrared (FTIR) spectroscopy is proposed using digitally generated data of adulterated edible oils from an infrared (IR) spectral library. The first step is the evaluation of digitally blended data sets. Specifically, IR spectra of adulterated edible oils are computed from digitally blending experimental data of the IR spectra of an edible oil and the corresponding adulterant using the appropriate mixing coefficients to achieve the desired level of adulteration. To determine whether two edible oils can be differentiated by FTIR spectroscopy, pure IR spectra of the two edible oils are compared with IR spectra of two edible oils digitally mixed using a genetic algorithm for pattern recognition to solve a ternary classification problem. If the IR spectra of the two edible oils and their binary mixtures are differentiable from principal component plots of the spectral data, then differences between the IR spectra of these two edible oils are of sufficient magnitude to ensure that a reliable classification by FTIR spectroscopy can be obtained. Using this approach, the feasibility of authenticating edible oils such as extra virgin olive oil (EVOO) directly from library spectra is demonstrated. For this study, both digital and experimental data are combined to generate training and validation data sets to assess detection limits in FTIR spectroscopy for the adulterants.Item Graphene Absorption Enhanced by Quasi-Bound-State-in-Continuum in Long-Wavelength Plasmonic–Photonic System(Advanced Optical Materials, 2022-09-07) Kananen, Thomas; Wiggins, Marcie; Wang, Zi; Wang, Feifan; Soman, Anishkumar; Booksh, Karl; Alù, Andrea; Gu, TingyiGraphene plasmonic structures can support enhanced and localized light–mater interactions within extremely small mode volumes. However, the external quantum efficiency of the resulting devices is fundamentally limited by material scattering and radiation loss. Here, such radiation loss channels are suppressed by tailoring the structure to support a symmetry-protected bound-state-in-the-continuum (BIC) system. With practical loss rates and doping level in graphene, over 90% absorption near critical coupling is expected from numerical simulation. Experimentally measured peak absorption of 68% is achieved in such a tailored graphene photonic–plasmonic system, with maximum 50% contrast to the control sample without graphene. Significant reduction of the plasmon absorption for a different spacer thickness verifies the sensitivity of the system to the quasi-BIC condition.