5 research outputs found
Ultrahigh Density Array of Free-Standing Poly(3-hexylthiophene) Nanotubes on Conducting Substrates via Solution Wetting
An ultrahigh density array of vertically and laterally aligned poly(3-hexylthiophene) (P3HT) nanotubes on conducting substrates was successfully fabricated by solution wetting in the anodized aluminum oxide (AAO) template. After solvent annealing, the conductivity of P3HT nanotubes was significantly increased due to highly aligned P3HT chains along the nanotube direction (or perpendicular to the substrate). This approach also provides a facile route for the preparation of ultrahigh density array of various conjugated polymer nanotubes. The conducting polymer nanotube array could be used for high performance organic devices, such as sensors, organic photovoltaic cells, and electrochromic devices
Hierarchically Well-Ordered Array of Concentric Silver Nanorings for Highly Sensitive Surface-Enhanced Raman Scattering Substrate
We fabricated a high density array of concentric silver
nanorings
in a large area (over in.<sup>2</sup>) with uniform gap distance by
utilizing half onion-shaped microdomains prepared by symmetric polystyrene-<i>block</i>-polyÂ(methyl methacrylate) copolymers (PS-<i>b</i>-PMMA) confined within hemispherical cavities in anodized aluminum
oxide (AAO) template. Silver nanoparticles with 6 nm height were selectively
deposited only on the PS microdomains by thermal evaporation. The
gap distance of two neighboring silver nanorings was controlled from
12 to 24 nm by changing the total molecular weight of PS-<i>b</i>-PMMAs. The substrate showed high surface-enhanced Raman scattering
(SERS) enhancement factor as high as 4.3 × 10<sup>7</sup> with
good reproducibility (±7%). It could be used for biosensing,
detection of trace-level explosive and hazardous chemicals, and reaction
monitoring
Hierarchically Self-Organized Monolithic Nanoporous Membrane for Excellent Virus Enrichment
Enrichment of viruses is essential
for making high dose viral stocks for vaccines and virus-related research.
Since the widely used ultracentrifugation for concentrating viral
stock requires ultra-high speed rotation, it easily destroys the activity
of some viruses, for instance, hepatitis c virus (HCV), which has
a fragile structure and low virus titer. We introduce a novel method
to concentrate HCV virus in stock by using a hierarchically self-organized
monolithic nanoporous membrane made by stepwise anodization. The pores
at the top part of the membrane have very regular sizes that are suitable
for the perfect filtration of the virus particles in the stock. On
the other hand, the remaining part has large pores that maintain high
flux and mechanical strength of the membrane under the high pressure
(up to 10 bar). The enrichment efficiency of HCV in crude stocks by
using the membrane became over 91%, which is four times higher than
that (∼22%) obtained by conventionally used centrifugation.
A very high efficiency results from the perfect filtration and no
damage to the virion particles during the enrichment process, whereas
significant damage to the HCV occurs during centrifugation. The hierarchically
self-organized monolithic nanoporous membrane could be effectively
employed for concentrating various fragile viruses in stocks, for
instance, rabies virus and human immunodeficiency virus in addition
to HCV virus
Bioinspired Dual Stimuli-Responsive Membranous System with Multiple On–Off Gates
Stimuli-responsive polymers have
been widely used for controlled
release of several biomolecules. In general, a single stimulus among
various stimuli, for instance, temperature, pH, or light, has been
used for these polymers. Although some stimuli are applied together,
one cannot control each stimulus independently at a given stimulus-responsive
polymer. However, to mimic biological system like cell membrane, multiple
on–off gates utilizing independent control of dual (or multiple)
stimuli should be used. Here, we introduce a stimuli-responsive membrane
controlled by two orthogonal stimuli. For this purpose, the top and
the bottom parts of anodized aluminum oxide membrane walls are independently
grafted by thermoresponsive polyÂ(<i>N</i>-isopropylacrylamide)
and pH-responsive polyÂ(acrylic acid), respectively, by using surface-initiated
atom transfer radical polymerization. The membrane clearly showed
two independent on–off gates depending on temperature and pH.
Furthermore, through light irradiation of two different wavelengths
(near-infrared and ultraviolet), temperature and pH were also controlled
independently and promptly. Thus, this membrane shows two independent
on–off gating of the transport of a model biomolecule of fluorescein
isothiocyanate-labeled bovine serum albumin. This strategy suggests
the potential of independently modified membrane in layers as stimuli-responsive
on–off gates for the application of artificial cell membrane
Arrangement of Lamellar Microdomains of Block Copolymer Confined in Hemispherical Cavities Having Two Controlled Interfaces
We
studied the arrangement of lamellar microdomains of polystyrene-<i>block</i>-polyÂ(methyl methacrylate) copolymer (PS-<i>b</i>-PMMA) confined in hemispherical cavities prepared by anodic aluminum
oxide template. The cavities have two controlled interfaces. One is
the cavity wall grafted with three different brushes (two selective
brushes made of PMMA-OH and PS-OH and one neutral brush made of PS-<i>ran</i>-PMMA-OH). The other is the top surface of the cavity
covered with films of PMMA and PS homopolymers and PS-<i>ran</i>-PMMA copolymer. When the cover film was selective to one of block
components, parallel lamellae were formed at the top of the cavity.
On the other hand, the lamellar microdomain arrangement at the middle
and bottom parts of the cavity highly depended on the nature of brushes
on the cavity wall: concentric (onion-like) lamellae for a selective
brush and unspecific complex structure for a neutral brush. Once parallel
lamellae and concentric lamellae meet together, isolated spheres consisting
of one block are formed. When the cavity wall is modified by the neutral
brush and the cover layer is selective to one of the blocks, stacked
lamellae are observed. However, when the cover film is neutral to
both block chains, concentric lamellae or bicontinuous lamellae are
formed, depending on the nature of the brushes on the cavity wall.
We also performed numerical mean field calculations based on the well-established
self-consistent field theory, from which we were able to reproduce
the experimental results