Layer-by-layer Assembly of Nanocomposites for Energy Applications.

In the dissertation we utilized the versatility of layer-by-layer assembly to explore the possibilities of improving membrane characteristics in energy-related applications using such technique. Nanocomposite membranes comprising common polymers and state-of-art nanomaterials were fabricated by LBL technique. Physical and electrochemical properties, as well as performance in actual energy devices were intensively investigated. In fuel cell applications, Pt nanoparticle decorated carbon nanotubes and carbon nanofibers were manufactured into freestanding membranes for the use in fuel cell MEAs. SWNT and CF in LBL membranes formed extensive percolation networks and contributed to enhanced electronic and proton conductivities. Platinum nanoparticles deposited on the sidewalls of SWNT and CF incorporated with Nafion significantly increased the number of catalysis sites and improved the accessibility to TPBs. Substantially improvement in performance and catalyst utilization was recorded. Thick and uniform zeolite membranes were also created by LBL means. Zeolite-L modified electrodes showed signal enhancement in ferrocyanide redox reaction. By investigating the physiosorption and transport behavior at the electrodes, we proposed that although redox species couldn't diffuse freely in and out the channel due to size restriction, the adsorption of redox species inside the PDDA/zeolite-L membranes changed the concentration profile dramatically in the vicinity of the electrode surface. The active electron/hole conducting nature inside unidirectional channels in zeolite-L nanocrystals also contributed to the increase of active redox surface area. Lastly, a new generation of ionic conducting nanocomposite membranes for lithium batteries was presented. Through layer-by-layer assembly of ionic conducting PEO and robust fibrous polymer Kevlar, the resulting membranes exhibited superior mechanical strength, high flexibility, and good conductivity. Mechanical strength and modulus of PEO-Kevlar ICMs are the key factors for lithium dendrite suppression, and were estimated to be orders higher than conventional polymer electrolytes. Special inhibition of re-crystallization in PEO phase by LBL technique indicates wider and higher working temperature window. Although the mechanical properties of the PEO-Kevlar membranes manufactured in this study did not reach the theoretical value for complete dendrite suppression, the results represent a step closer to next generation high capacity high power lithium batteries.Ph.D.Chemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/84629/1/peterho_1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/84629/2/peterho_3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/84629/3/peterho_2.pd

Loading of Exponentially Grown LBL Films with Silver Nanoparticles and Their Application to Generalized SERS Detection

Filmvorstellung : DÜnne Filme, die durch exponentielles Schichtenwachstum erzeugt wurden, zeigen hohe DiffusivitÄten und lassen sich leicht mit anorganischen Nanopartikeln infiltrieren. Die Filme kÖnnen molekulare Systeme abhÄngig von der Schichtzusammensetzung aus LÖsungen sequestrieren und liefern oberflÄchenverstÄrkte Raman-Signale (SERS) mit hoher IntensitÄt (siehe Bild).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63572/1/5430_ftp.pd