This item is under embargo and not available online per the author's request. For access information, please visit http://libanswers.wustl.edu/faq/5640.

ORCID

http://orcid.org/0000-0001-5210-6884

Date of Award

Winter 12-15-2018

Author's School

School of Engineering & Applied Science

Author's Department

Mechanical Engineering & Materials Science

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Cellulose is biodegradable, renewable, and abundant in nature thus cellulose (or paper)-based products can be inexpensively produced and recycled. Among cellulosic materials, bacterial nanocellulose (BNC) draws a special research attention due to the inherent three-dimensional nanofibrous structure, excellent mechanical flexibility, high purity and well-defined surface chemistry, and cost-efficient, scalable and environment-friendly synthesis. BNC can be biosynthesized by Gluconacetobacter xylinus, which is the most characterized BNC producer among various microorganisms. BNC is composed of highly pure cellulose nanofibrils, produced from well-defined dextrose through biochemical steps and subsequent self-assembling of the secreted cellulose fibrils which has the dimension ranges from 25 to 100 nm in diameter from bacteria in the culture medium. During the biosynthesis of BNC, shape-controlled hydrogels with well-defined network structure pore diameters below 10 µm can be easily achieved. For all the above-mentioned reasons, BNC is a highly promising platform material for the fabrication of functional composites through in situ growth or adsorption of pre-synthesized nanostructures on the nanoscale cellulose fibers.

In this work, we have designed and demonstrated novel strategies to realize BNC-based functional nanocomposites with applications in sensing, water purification and energy storage. We have demonstrated a BNC film-based surface enhanced Raman scattering (SERS) substrate which has 3D porous structure and ultrafine fibers with uniform and dense adsorption of plasmonic nanostructures, resulting large SERS enhancement and excellent uniformity of SERS activity.

For the first time, we have demonstrated a novel, highly scalable, cost-effective and green strategy to realize functional BNC-based foams/membranes. Functional materials such as graphene oxide (GO), polydopamine (PDA) can be efficiently incorporated within BNC matrix during its growth. Owing to the intercalation of functional materials within the layered BNC matrix, the functional composites showed excellent mechanical robustness and flexibility, which is crucial for efficient, large-scale applications, either as a foam or as a membrane.

Specifically, we have designed and developed a bilayered hybrid biofoam comprised of BNC and RGO and a completely biodegradable bilayered foam based on BNC and PDA for highly efficient solar steam generation, which can be a sustainable solution to alleviate global water crisis. An innovative water filtration membrane based on BNC and RGO which harvests sunlight to kill microorganisms has been developed to provide a novel anti-biofouling approach. We have also demonstrated a robust filtration membrane based on BNC loaded with GO and PdNPs, which exhibited excellent dye degradation performance for highly efficient wastewater treatment. Furthermore, the in situ fabrication approach has been extended to polymeric materials such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to realize hybrid flexible supercapacitor electrodes based on RGO, BNC and PEDOT:PSS.

The fabrication strategies and materials design demonstrated in this work can be easily extended to realize various BNC-based nanocomposites with applications in water purification, energy harvesting, sensing, catalysis, and life sciences.

Language

English (en)

Chair

Srikanth Singamaneni

Committee Members

Young-Shin Jun, Guy Genin, Jeremiah Morrissey, Julio D'Arcy,

Comments

Permanent URL: https://doi.org/10.7936/3312-hn37

Available for download on Friday, January 24, 2020

Share

COinS