Nanoscience and Microsystems ETDs

Rachel Hjelm

Publication Date

6-9-2016

Abstract

In the face of todays rapidly growing energy demands accompanied by limited, non-renewable supplies, development of novel energy alternatives that are both renewable and inexpensive has become more important than ever. Development of 3D structures exploring the properties of nano-materials and biological molecules has been shown through the years as an effective path forward for the design of advanced bio-nano architectures for enzymatic fuel cells (EFCs). Despite advantages over conventional fuel cells, EFCs still suffer from several problems including low efficiency and stability. Overcoming these limitations in order to make them more viable for real world application is an ongoing challenge for researchers. Functionalized carbon nanotubes (CNTs) were covalently bonded to diazonium salt modified gold surfaces through carbodiimide chemistry creating a brush-type nanotube alignment. Having CNTs ordered in this nature developed a highly ordered structure with markedly high surface area that allowed for the attachment of protein/DNA assembly. The specificity of the enzyme immobilization was controlled by small protein structural motifs, called zinc fingers (ZnF) that bind to specific dsDNA sequences and may be genetically bound to small laccase (SLAC-3ZnF) or other redox enzymes. Utilizing scaffolds with gold nanoclusters (AuNC) for mediated electron transfer (MET), we test the capabilities for oxygen reduction reactions (ORR) by SLAC-3ZnF. Direct absorption on SWNT results in poor ORR while using DNA results in slowed reaction kinetics. With the addition of AuNC, ORR and electron transfer are improved. Analytical techniques such as x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and enzymatic activity analysis, allowed characterization at each stage of development. Additionally, two methods for co-immobilization on consecutive tricarboxylic acid cycle (TCA) enzymes were investigated. Encapsulation using deacylated chitosan (chit) and tethering through amide bond linkage with 1-pyrenebutanoic acid, succinimidyl ester (PBSE) were used to immobilize porcine heart malate dehydrogenase (MDH) and citrate synthase (CS) on multi-walled carbon nanotubes (MWNTs). The effects of each method on the oxidation of L-malate (M) by MDH in the presence of CS are reported. Poly-(methylene green)-modified MWNT 'buckypaper' (PMG-BP) was used to reduce cell overpotential through regeneration of oxidized nicotinamide adenine dinucleotide (NAD+) from reduced form (NADH).'

Keywords

Nanotubes, Biofuel Cells, Enzyme Immobilization, Zinc Fingers, Tricarboxylic Acid Cycle, Small Laccase, Biomimetics, Bioelectrochemistry, Encapsulation, Tethering, Deoxyribose Nucleic Acid

Sponsors

United States Air Force Office of Scientific Research

Document Type

Dissertation

Language

English

Degree Name

Nanoscience and Microsystems

Level of Degree

Doctoral

Department Name

Nanoscience and Microsystems

First Committee Member (Chair)

Atanassov, Plamen

Second Committee Member

Shreve, Andrew

Third Committee Member

Ista, Linnea

Fourth Committee Member

Babanova, Sofia

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