Nanomaterial and molecular adsorption onto complex surfaces

Gole, Matthew T.

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https://hdl.handle.net/2142/116095 Copy

Description

Title

Nanomaterial and molecular adsorption onto complex surfaces

Author(s)

Gole, Matthew T.

Issue Date

2022-07-14

Director of Research (if dissertation) or Advisor (if thesis)

Murphy, Catherine J.

Doctoral Committee Chair(s)

Murphy, Catherine J.

Committee Member(s)

• Girolami, Gregory S.
• Nam, SungWoo
• Rodríguez-López, Joaquín

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Gold nanoparticles
• graphene
• protein adsorption
• nanotechnology

Abstract

Adsorption and assembly at surfaces is fundamental to materials and surface science. Introducing surface inhomogeneities in the form of nanoscale topographical features or chemical gradients allows for greater control over material behavior at the solid-liquid interface. Soft polymeric and two-dimensional (2D) materials are versatile for tuning surface properties via strain-induced introduction of topographical features such as wrinkles and crumples. Their chemical properties are similarly customizable through post-process surface treatments. This dissertation focuses on the effects of surface topography in mechanically deformed soft and 2D materials on the adsorption and assembly of gold nanoparticles and immunoglobulins, as well as how chemical modification of graphene affects pyrene adsorption. Chapter 1 will introduce soft and 2D materials and methods for controlling their surface structures. Special attention is given to the tunable deformation of elastomers with rigid thin film overlayers. The mechanical properties of graphene and its deformations through buckle delamination will also be described. This is followed by a review of specific applications of deformed soft materials, including plasmonic gold nanoparticle assembly, cell culturing, and tissue engineering. Finally, the chemical properties of graphene and its ability adsorb polyaromatic molecules will be discussed. In Chapter 2, a method for bottom-up integration of plasmonic nanoparticle assemblies onto graphene substrates is introduced. Poly(dimethylsiloxane) (PDMS) wrinkles with a conformal graphene overlayer are fabricated and used as geometric templates for assembly of colloidal gold nanoparticles. The aligned particles acquire anisotropic optical responses through plasmonic coupling along the nanoparticle chains. The maximum wavelength of absorbance is tuned in the near-IR from 730 to 968 nm with increasing nanoparticle size. It is additionally shown that nanoparticles can be controllably spaced apart within the channels by increasing the bulkiness of the capping ligand. The effect of this is the elimination of plasmonic coupling and a resulting isotropic optical response. This study introduces a potentially versatile substrate for plasmonically enhanced 2D material devices. The biological interface with wrinkled and crumpled surfaces is the subject of Chapter 3. Immunoglobulin adsorption on wrinkled PDMS with and without a conformal graphene overlayer, as well as buckle delaminated graphene crumples, is analyzed with atomic force microscopy. Plasma-treated PDMS wrinkles with a negative surface charge are found to disfavor adsorption at the concave wrinkle valleys based on reduced maximum surface packing. Conformal graphene wrinkles, in contrast, form patchy immunoglobulin films, with wrinkle valleys experiencing lower protein coverage due to thin film drying effects on the hydrophobic surface. Buckle delaminated crumples of high roughness adsorb proteins evenly along the crumple spines, suppressing thin film formation at the last stage of drying and preventing drying effects. These findings inform future applications where deformed surfaces contact biological fluids. Finally, increasing the control over noncovalent functionalization on graphene substrates is explored in Chapter 4. Graphene substrates are modified by varying levels of hydrogenation and fluorination to tune the degree of sp2 conjugation. 1-Ethynylpyrene is then used as a Raman tag to quantify relative maximum adsorption of pyrene-based reagents through confocal Raman microscopy. Hydrogenation reduces maximum pyrene adsorption to 12% compared to that on pristine graphene, while fluorination is used to achieve adsorption values below 5%. It is additionally found that pyrene reagents can intercalate heterointerfaces of hydrogenated graphene and fluorinated graphene with pristine graphene.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Matthew Gole

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