3 research outputs found
Self-Assembly of Large Gold Nanoparticles for Surface-Enhanced Raman Spectroscopy
Performance
of portable technologies from mobile phones to electric
vehicles is currently limited by the energy density and lifetime of
lithium batteries. Expanding the limits of battery technology requires <i>in situ</i> detection of trace components at electrode–electrolyte
interphases. Surface-enhance Raman spectroscopy could satisfy this
need if a robust and reproducible substrate were available. Gold nanoparticles
(Au NPs) larger than 20 nm diameter are expected to greatly enhance
Raman intensity if they can be assembled into ordered monolayers.
A three-phase self-assembly method is presented that successfully
results in ordered Au NP monolayers for particle diameters ranging
from 13 to 90 nm. The monolayer structure and Raman enhancement factors
(EFs) are reported for a model analyte, rhodamine, as well as the
best performing polymer electrolyte salt, lithium bisÂ(trifluoroÂmethane)Âsulfonimide.
Experimental EFs for the most part correlate with predictions based
on monolayer geometry and with numerical simulations that identify
local electromagnetic field enhancements. The EFs for the best performing
Au NP monolayer are between 10<sup>6</sup> and 10<sup>8</sup> and
give quantitative signal response when analyte concentration is changed
Gold Nanoparticle Monolayers with Tunable Optical and Electrical Properties
Centimeter-scale gold nanoparticle
(Au NP) monolayer films have
been fabricated using a water/organic solvent self-assembly strategy.
A recently developed approach, drain to deposit, is demonstrated to
be most effective in transferring the Au NP films from the water/organic
solvent interface to various solid substrates while maintaining their
integrity. The interparticle spacing was tuned from 1.4 to 3.1 nm
using alkylamine ligands of different lengths. The ordering of the
films increased with increasing ligand length. The surface plasmon
resonance and the in-plane electrical conductivity of the Au NP films
both exhibit an exponential dependence on the interparticle spacing.
These findings show great potential in scaling up the manufacturing
of high-performance optical and electronic devices based on two-dimensional
metallic nanoparticle superlattices
Phase Behavior and Electrochemical Characterization of Blends of Perfluoropolyether, Poly(ethylene glycol), and a Lithium Salt
Electrolytes
consisting of low molecular weight perfluoropolyether
(PFPE), polyÂ(ethylene glycol) (PEG), and lithium bisÂ(trifluoromethanesulfonyl)Âimide
(LiTFSI) blends were prepared and systematically studied for salt
concentration and stoichiometry effects on the materials’ thermal
and electrochemical properties. Herein we report that the tunable
ratios of PFPE and PEG allow for precise control of crystalline melting
and glass transition temperature properties. These blended liquid
polymer electrolytes are inherently nonflammable and remain stable
in the amorphous phase from approximately 150 °C down to −85
°C. The ionic conductivity of the electrolytes are on the order
of 10<sup>–4</sup> S/cm at 30 °C, which makes them suitable
for rechargeable lithium batteries