The critical issues that hinder the practical applications of lithium-sulfur batteries, such as dissolution and migration of lithium polysulfides, poor electronic conductivity of sulfur and its discharge products, and low loading of sulfur, have been addressed by designing a functional separator modified using hydroxyl-functionalized carbon nanotubes (CNTOH). Density functional theory calculations and experimental results demonstrate that the hydroxyl groups in the CNTOH provoked strong interaction with lithium polysulfides and resulted in effective trapping of lithium polysulfides within the sulfur cathode side. The reduction in migration of lithium polysulfides to the lithium anode resulted in enhanced stability of the lithium electrode. The conductive nature of CNTOH also aided to efficiently reutilize the adsorbed reaction intermediates for subsequent cycling. As a result, the lithium-sulfur cell assembled with a functional separator exhibited a high initial discharge capacity of 1056 mAh g (corresponding to an areal capacity of 3.2 mAh cm) with a capacity fading rate of 0.11% per cycle over 400 cycles at 0.5 C rate.
Self-assembly
of thermally responsive polypeptides into unique
nanostructures offers intriguing attributes including dynamic physical
dimensions, biocompatibility, and biodegradability for the smart bio-nanomaterials.
As elastin-based polypeptide (EBP) fusion proteins with lower critical
solution temperature (LCST) are studied as drug delivery systems,
EBP block copolypeptides with the resilin-based polypeptide (RBP)
displaying an upper critical solution temperature (UCST) have been
of great interest. In this study, we report thermally triggered, dynamic
self-assembly of EBP- and RBP-based diblock copolypeptides into switched
nanostructures with reversibility under physiological conditions.
Molecular DNA clones encoding for the EBP–RBP diblocks at different
block length ratios were biosynthesized via recursive directional
ligation and overexpressed, followed by nonchromatographic purification
by inverse transition cycling. Genetically engineered diblock copolypeptides
composed of the EBP with an LCST and the RBP with a UCST showed converse
phase transition behaviors with both a distinct LCST and a distinct
UCST (LCST < UCST). As temperature increased, three phases of these
EBP–RBP diblocks were observed: (1) self-assembled micelles
or vesicles below both LCST and UCST, (2) whole aggregates above LCST
and below UCST, and (3) reversed micelles above both LCST and UCST.
In conclusion, these stimuli-triggered, dynamic protein-based nanostructures
are promising for advanced drug delivery systems, regenerative medicine,
and biomedical nanotechnology.
A variety
of block copolypeptides with stimuli responsiveness have
been of growing interest for dynamic self-assembly. Here, multistimuli-responsive
triblock copolypeptides composed of thermosensitive elastin-based
polypeptides (EBP) and ligand-responsive calmodulin (CalM) were genetically
engineered, over-expressed, and nonchromatographically purified by
inverse transition cycling. Diluted EBP-CalM-EBP (ECE) triblock copolypeptides
under physiological conditions self-assembled into vesicles at the
nanoscale by temperature-triggered aggregation of the EBP block with
lower critical solution temperature behaviors. Furthermore, concentrated
ECE triblock copolypeptides under identical conditions exhibited thermally
induced gelation, resulting in physically crosslinked hydrogels. They showed controlled
rheological and mechanical properties depending on the conformational
change of the CalM middle block induced by binding either Ca2+ or Ca2+ and trifluoperazines (TFPs) as ligands. In addition,
both Ca2+-free and Ca2+-bound ECE triblock copolypeptide
hydrogels exhibited biocompatibility, while those bound to both Ca2+ and TFPs showed severe cytotoxicity because of controlled
TFP release of the CalM blocks. The ECE triblock hydrogels with stimuli
responsiveness would be useful as injectable drug delivery depots
for biomedical applications.
Herein, Janus bimetallic nanorod clusters-poly(aniline) nanocomposites (JRCPCs) with gold nanorod clusters (GNRCs) in side-by-side (SBS) or end-to-end (ETE) configuration are synthesized, and applied to surface enhanced Raman scattering (SERS)-based biosensing...
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