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.²) with uniform gap distance by utilizing half onion-shaped microdomains prepared by symmetric polystyrene-<i>block</i>-poly­(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 × 10⁷ 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 poly­(<i>N</i>-isopropylacrylamide) and pH-responsive poly­(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>-poly­(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