Temperature-Responsive One-Dimensional Nanogels Formed by the Cross-Linker-Aided Single Particle Nanofabrication Technique

A single particle nanofabrication technique was successfully applied to the fabrication of homogeneous poly­(<i>N</i>-isopropylacrylamide) (PNIPAAm) 1D nanogels over a large area, using <i>N</i>,<i>N</i>′-methylene-bis-acrylamide (MBAAm) as a cross-linker. The PNIPAAm 1D nanogels with high aspect ratio over 130 were formed uniformly on the substrate, and the mechanical strength and the length of the 1D nanogels can be easily controlled by adjusting the MBAAm content. The 1D nanogels were transformed from the non-aggregated to aggregated forms over a lower critical solution temperature (LCST) of approximately 32 °C in water. Precise trace of the temperature induced change in the size of the 1D nanogel was well interpreted by the coil-to-globule transition of PNIPAAm, which was clearly visualized in the present study. This is the first report of uniform shape change for a 1D nanogel by external stimulus over a large area

Fabrication of Thermoresponsive Nanoactinia Tentacles by a Single Particle Nanofabrication Technique

Nanowires that are retractable by external stimulus are the key to fabrication of nanomachines that mimick actinia tentacles in nature. A single particle nanofabrication technique (SPNT) was applied over a large area to the fabrication of retractable nanowires (nanoactinia tentacles) composed of poly­(<i>N</i>-isopropylacrylamide) (PNIPAM) and poly­(vinylpyrrolidone) (PVP), which are thermoresponsive and hydrophilic polymers. The nanowires were transformed with increasing temperature from rod-like- to globule-forms with gyration radii of ∼1.5 and ∼0.7 μm, respectively. The transformation of the nanowires was reversible and reproducible under repeated cycles of heating and cooling. The reversible transformation was driven by hydration and dehydration of PNIPAM, the thermoresponsive segments, resulting in coil-to-globule transformation of the segments. The nanoactinia tentacle systems trapped the nanoparticles as a model of living cells under thermal stimulation, and the trapping was controlled by temperature. We present herein a unique nanomachine system which can be applicable to nanoparticle filtering/sensing systems and expandable to large-area functionalization and demonstrate polymer-based nanoactuators via scaling of molecular level coil-to-globule transformation into micron-sizes

Formation of Amorphous H₃Zr₂Si₂PO₁₂ by Electrochemical Substitution of Sodium Ions in Na₃Zr₂Si₂PO₁₂ with Protons

The sodium ions in Na₃Zr₂Si₂PO₁₂ (NASICON) were substituted with protons using an electrochemical alkali–proton substitution (APS) technique at 400 °C under a 5% H₂/95% N₂ atmosphere. The sodium ions in NASICON were successfully substituted with protons to a depth of <400 μm from the anode. Completely protonated NASICON, i.e., H₃Zr₂Si₂PO₁₂, was obtained to a depth <40 μm from the anode, although complete protonation of NASICON cannot be achieved by ion exchange in aqueous acid. H₃Zr₂Si₂PO₁₂ was amorphous, whereas the partially protonated NASICON was crystalline, and its unit cell volume decreased with an increase in the extent of substitution. Amorphous H₃Zr₂Si₂PO₁₂ was prepared by pressure-induced amorphization of the NASICON framework, in which an internal pressure of ∼3.5 GPa was induced by the substitution of large sodium ions with small protons during APS at 400 °C

Semiconducting Cross-Linked Polymer Nanowires Prepared by High-Energy Single-Particle Track Reactions

High-energy charged particle irradiation of cross-linking polymers gives nanowires formed by cross-linking reactions along the ion track trajectories. Here, the direct formation of nanowires consisting of a conjugated polymer by single-particle nanofabrication technique (SPNT) is investigated. Poly­(9,9′-di-<i>n</i>-octylfluorene) (PFO), regioregular poly­(3-hexylthiophene) (rrP3HT), and poly­[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) underwent an efficient cross-linking reaction upon irradiation, resulting in the formation of 1-dimensional nanostructures with high and desired aspect ratio reaching up to ∼200. The size of nanowires was perfectly interpreted by well-sophisticated theoretical aspects based on the statistical theory of polymer backbone configurations, suggesting that simple cross-linking reactions of the polymers determine the size and structure of nanowires. PFO based nanostructures exhibited sharp and intense emission with high fluorescence quantum yield indicating the absence of any significant inter/intra polymer chromophore interactions in the nanowires assemblies