Graduation Year

2025

Document Type

Thesis

Degree

M.S.C.H.

Degree Name

MS in Chemical Engineering (M.S.C.H.)

Degree Granting Department

Chemical, Biological and Materials Engineering

Major Professor

Ryan Toomey, Ph.D.

Committee Member

Arash Takshi, Ph.D.

Committee Member

Weizhong Zou, Ph.D.

Keywords

microtension, PVA, Scherrer, Williamsion-Hall, XRD

Abstract

Plastic sorting remains a major driver of recycling costs, and existing infrared (IR) optical identification systems cannot determine material prominence or quality, nor reliably identify dark polymers [1]. This work explores a PVA-stabilized sol–gel and thermal synthesis route for magnesium-doped zinc oxide (Mg:ZnO) as a tunable photoluminescent tracer phosphor.

Lattice-defect control forms the foundation of phosphorescent emission tuning, enabling unique spectral fingerprints to be generated based on synthesis parameters—Mg molar ratio (Mg%), PVA mass (g), and calcination temperature (°C). Photoluminescence (PL) spectra (400–850 nm) were analyzed using Gaussian peak fitting and principal component analysis (PCA), reducing hundreds of spectral features to a few predictive variables. Machine learning (ML) models successfully classified samples by PVA mass and calcination temperature and predicted Mg doping ratio with above-random accuracy. Powder X-ray diffraction (PXRD), analyzed via analysis of variance (ANOVA), confirmed polycrystalline wurtzite Mg:ZnO with minor MgO phases that diminished at higher temperatures, statistically linking PXRD structural results to PCA-derived PL emission trends.

Collectively, the structural, optical, and statistical results demonstrate that synthesis parameters can effectively tune PL emission behavior, positioning Mg:ZnO as a promising tracer phosphor for intelligent plastic-recycling technologies.

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