Effects of metal nanoparticle morphology on carbon nanotube biosensors

Mayra S Artiles Fonseca, Purdue University

Abstract

Carbon nanomaterials in combination with metal nanoparticles have been proven to be a highly functioning platform for electrochemical sensing due to their unique mechanical, electrical, and chemical properties. This combination has resulted in the most competitive sensitivities and low detection limit up to date. However, fabrication of such arrays in repeatable techniques that can be translated into mass production while retaining the sensing properties of the prototypes can be a tricky task. Additionally, the true role of the nanoparticle morphology is something seldom addressed in multiple publications in the field since often simply performing repeatable geometries at such small dimensions in a difficult task. This thesis discusses studies the role of the geometry of the nanoparticles in biosensing platforms by describing a bottom-up approach to nanoelectrode array fabrication suitable for a variety of biological biomarkers. We first develop a template of porous anodic alumina from a silicon wafer where we grow single-walled carbon nanotubes (SWCNTs) via microwave plasma enhanced chemical vapor desposition. Pt nanospheres, Pd nanocubes, and Pt multifaceted nanobands are electrochemically deposited at the SWCNT defect sites to enhance the electroreactivity. These electrodes are then converted into glucose biosensors by immobilizing the enzyme glucose oxidase (GOx) via noncovalent drop coat and polymer enzyme entrapment methods. These combinations provide excellent sensitivities and some of the lowest detection limits available in the literature. However, these still need to be compared among themselves to study the role of the nanoparticle morphology. We tested the Pt nanospheres in a glucose biosensing scenario, we used this as our baseline biosensor. Then we compared Pd nanocubes and Pt nanospheres in a glutamate biosensor and found that Pt spheres had a higher sensing capability (wider linear range and lower detection limit) than the Pd nanocubes. We finally compare these with a Pt multifaceted nanoband in a glucose biosensor and were able to determine that the higher the number of facets, regardless of the materials, the more electroactive sites would react with the enzyme-target reaction therefore allowing a direct electron transfer from the redox center in the enzyme to the electrode surface.

Degree

M.S.M.E.

Advisors

Fisher, Purdue University.

Subject Area

Agricultural engineering|Biomedical engineering|Nanoscience|Nanotechnology

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