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Cheng Chen Disseration Final.pdf (21.25 MB)

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NUCLEAR QUADRUPLE RESONANCE AND LOW-FIELD NUCLEAR MAGNETIC RESONANCE FOR MATERIALS AUTHENTICATION

Chen, Cheng
http://orcid.org/0000-0002-3525-7792
http://rave.ohiolink.edu/etdc/view?acc_num=case1567518073598426

Abstract Details

2020, Doctor of Philosophy, Case Western Reserve University, EECS - Electrical Engineering.
The authentication of materials is an issue of extreme importance for modern civilization. In particular, maintaining the security and integrity of food items and pharmaceutical products through the global supply chain has emerged as a critical need. This is because mislabeling, contamination, adulteration, and false advertising are increasingly common and pose unacceptable health risks. In fact, consumer demand for safe products is so significant that accurate and reliable analytical authentication techniques are urgently needed. This thesis investigates the application of nuclear quadrupole resonance (NQR) and low-field nuclear magnetic resonance (NMR) for authentication of medicines, dietary supplements, food products, and other materials. The overall goal is to use NQR and low-field NMR to measure and verify ``unique chemical fingerprints'' of such materials in order to fight the threat of low quality and counterfeit products. NQR spectroscopy is commonly used to characterize solid materials containing quadrupolar nuclei. It is a promising technique for detecting plastic explosives and other forbidden substances as well as for authenticating food and pharmaceutical products. However, it is only applicable to solids. The related technique of low-field NMR is ideally suited for inspection of liquids. In particular, low-field NMR is popular for authenticating food items due to its portability and low maintenance costs. However, several issues including expensive instrumentation, weak signal strength, and prolonged measurement times can influence the accuracy of the fingerprints and limit the range of applications. For example, NQR and low-field NMR spectrometers are known to be expensive and bulky. They are also narrowband in most cases, which is not ideal for materials detection. To address these problems, we developed an analog front-end that can excite and detect 14N NQR spectra over a wide frequency range; its operating frequency can be rapidly set by software, while sensitivity is comparable to conventional narrowband front-ends over the entire range. This front-end improves the accuracy of authentication by enabling multiple-frequency experiments. Moreover, weak signal strength is a big concern for NQR and low-field NMR applications. Matched filtering and model-based signal optimization methods were developed to maximize signal-to-noise ratio (SNR). Calibration algorithms for converting measured NQR signal amplitudes into nuclear spin densities were also found, thus enabling the use of NQR as a quantitative technique. Lastly, a rapid ``single-shot'' method for spatially-resolved NQR is proposed. This method takes advantage of the fact that NQR relaxation rates are field-dependent: the observed field dependence is used to convert relaxation time distributions measured in a static field gradient (estimated via Laplace inversion of time-domain data) into spatial distributions. The method was validated using 35Cl and 37Cl NQR of sodium chlorate and other compounds. Effective spatial resolution was further improved by using machine learning to classify the measured spatial distributions.
Soumyajit Mandal (Committee Chair)
Francis Merat (Committee Member)
Robert Brown (Committee Member)
Ming-Chun Huang (Committee Member)
Electrical Engineering; Physics

Recommended Citations

Citations

  • Chen, C. (2020). NUCLEAR QUADRUPLE RESONANCE AND LOW-FIELD NUCLEAR MAGNETIC RESONANCE FOR MATERIALS AUTHENTICATION [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1567518073598426

    APA Style (7th edition)

  • Chen, Cheng. NUCLEAR QUADRUPLE RESONANCE AND LOW-FIELD NUCLEAR MAGNETIC RESONANCE FOR MATERIALS AUTHENTICATION. 2020. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1567518073598426.

    MLA Style (8th edition)

  • Chen, Cheng. "NUCLEAR QUADRUPLE RESONANCE AND LOW-FIELD NUCLEAR MAGNETIC RESONANCE FOR MATERIALS AUTHENTICATION." Doctoral dissertation, Case Western Reserve University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1567518073598426

    Chicago Manual of Style (17th edition)

case1567518073598426
271
© 2019, some rights reserved.Creative Commons License NUCLEAR QUADRUPLE RESONANCE AND LOW-FIELD NUCLEAR MAGNETIC RESONANCE FOR MATERIALS AUTHENTICATION by Cheng Chen is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.