Graduate Studies

 

First Advisor

Jeffrey E. Shield

Degree Name

Doctor of Philosophy (Ph.D.)

Committee Members

Rebecca Lai, Yongfeng Lu, Bai Cui, Abdelghani Laraoui

Department

Engineering

Date of this Version

7-2024

Document Type

Dissertation

Citation

A dissertation presented to the faculty of the Graduate College of the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy

Major: Materials Engneering

Under the supervision of Professor Jeffrey E. Shield

Lincoln, Nebraska, July 2024

Comments

Copyright 2024, Rifat Mahbub. Used by permission

Abstract

Spin crossover (SCO) complexes have unique properties of switching their spin state upon perturbations like temperature, pressure, light, etc. Along with the spin state, different properties vary like structural, electrical, magnetic, optical properties. This enables these materials to be potentially used in various applications like molecular electronics, memory devices, switching devices, sensors and many more. To incorporate spin crossover materials into devices with efficient performance, the electrical behavior needs to be understood. This dissertation aims to investigate the effect of crystal structure on the electrical properties of iron(II) triazole spin crossover complex and how it can be modified for better performance.

In chapter two, materials for the experiments and various experimental methods are discussed. The third chapter of this dissertation reports two polymorphs of iron(II) triazole- nanoparticles and nanorods, and their crystallographic investigation. It also contains electrical conductivity studies on polymorphs. It was observed that conductivity changes with morphology and crystal properties.

The fourth chapter emphasizes how the conductivity changes with localized strain application on one of the polymorphs and it establishes a relationship between applied strain and conductivity. It was found that conductivity increases up to a certain strain and then it decreases with increasing strain. To manipulate this strain-dependent conductivity, the polymorph was incorporated with piezoelectric PVDF film to make a layer-by-layer composite film, which is reported in chapter five. It was found that the spin crossover couples with the piezoelectricity of the PVDF film, and the conductivity of the system increases. This will make the layer-by-layer film potential for future applications in different sensors and switches.

Advisor: Jeffrey E. Shield

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