Chiral plasmonic nanostructures on achiral nanopillars.

Chirality of plasmonic films can be strongly enhanced by three-dimensional (3D) out-of-plane geometries. The complexity of lithographic methods currently used to produce such structures and other methods utilizing chiral templates impose limitations on spectral windows of chiroptical effects, the size of substrates, and hence, further research on chiral plasmonics. Here we demonstrate 3D chiral plasmonic nanostructures (CPNs) with high optical activity in the visible spectral range based on initially achiral nanopillars from ZnO. We made asymmetric gold nanoshells on the nanopillars by vacuum evaporation at different inclination and rotation angles to achieve controlled symmetry breaking and obtained both left- and right-rotating isomers. The attribution of chiral optical effects to monolithic enantiomers made in this process was confirmed by theoretical calculations based on their geometry established from scanning electron microscope (SEM) images. The chirality of the nanoshells is retained upon the release from the substrate into a stable dispersion. Deviation of the incident angle of light from normal results in increase of polarization rotation and chiral g-factor as high as -0.3. This general approach for preparation of abiological nanoscale chiral materials can be extended to other out-of plane 3D nanostructures. The large area films made on achiral nanopillars are convenient for sensors, optical devices, and catalysis.

Selective removal of radioactive iodine from water using reusable Fe@Pt adsorbents.

Environmental damage from serious nuclear accidents should be urgently restored, which needs the removal of radioactive species. Radioactive iodine isotopes are particularly problematic for human health because they are released in large amounts and retain radioactivity for a substantial time. Herein, we prepare platinum-coated iron nanoparticles (Fe@Pt) as a highly selective and reusable adsorbent for iodine species, i.e., iodide (I-), iodine (I2), and methyl iodide (CH3I). Fe@Pt selectively separates iodine species from seawater and groundwater with a removal efficiency ≥ 99.8%. The maximum adsorption capacity for the iodine atom of all three iodine species was determined to be 25 mg/g. The magnetic properties of Fe@Pt allow for the facile recovery and reuse of Fe@Pt, which remains stable with high efficiency (97.5%) over 100 uses without structural and functional degradation in liquid media. Practical application to the removal of radioactive 129I and feasibility for scale-up using a 20 L system demonstrate that Fe@Pt can function as a reusable adsorbent for the selective removal of iodine species. This systematic procedure is a standard protocol for designing highly active adsorbents for the clean separation and removal of various chemical species dissolved in wastewater.

Small, stable, and monodispersed bubbles encapsulated with biopolymers.

A microfluidic route to producing small (<10 µm) bubbles with a narrow size distribution and long-time (at least, up to one month) stability is reported. The bubbles are encapsulated with a protein-polysaccharide shell. The strategy includes the following events, occurring in sequence: (i) a microfluidic generation of bubbles from a mixture of CO(2) and a minute amount of gases with low solubility in water, in an aqueous solution of lysozyme and sodium alginate; (ii) the dissolution of CO(2) leading to the shrinkage of bubbles and a local increase in acidity of the medium; (iii) the deposition of lysozyme at the gas-water interface triggered by the local decrease in pH; (iv) the deposition of alginate onto the lysozyme shell, due to the electrostatically driven complexation of alginate with lysozyme.

A microfluidic approach to chemically driven assembly of colloidal particles at gas-liquid interfaces.

Bubbling up: Dissolution of CO(2) bubbles in a suspension of colloidal particles chemically induces the assembly of particles on the surface of shrunken bubbles, and thus yields rapid continuous formation of a colloidal armor. This approach maintains the high colloidal stability of particles in bulk, has increased productivity, and allows the formation of bubbles with precisely controlled dimensions.

Manipulation of Chain Conformation for Optimum Charge-Transport Pathways in Conjugated Polymers.

A pair of different diketopyrrolopyrrole-based conjugated polymers (CPs) were designed and synthesized to investigate the effect of chain conformation on their molecular assembly. Conformation management was achieved by the incorporation of different linkers during polymerization. Through the use of computational calculations and UV-vis absorption measurements, the resulting CPs (PDPP-T and PDPP-BT) were found to exhibit partly modulated chain geometry. Grazing incident X-ray diffraction experiments with a two-dimensional detector revealed that PDPP-T having a planar chain conformation exhibited an edge-on type molecular arrangement, which evolved to a face-on type chain assembly when the planar geometry was altered to a slightly twisted one as in PDPP-BT. In addition, it was verified that the directional electric carrier mobility of CPs was critically distinguished by the distinctive chain arrangement in spite of their similar chemical structure. Concentration-dependent absorption measurements could provide an improved understanding of the assembly mechanism of CP chains: the planar conformation of PDPP-T facilitates the formation of preassembled chains in a concentrated solution and further directs the edge-on stacking, while the twisted dihedral angle along the benzothiophene in PDPP-BT prevents chain assembly, resulting in the face-on stacking. Because CP chain conformation is inevitably connected with the generation of preassembled chains, manipulating CP geometry could be an efficient tool for extracting an optimum chain assembly that is connected with the principal charge-transport pathway in CPs.

Terminal supraparticle assemblies from similarly charged protein molecules and nanoparticles.

Self-assembly of proteins and inorganic nanoparticles into terminal assemblies makes possible a large family of uniformly sized hybrid colloids. These particles can be compared in terms of utility, versatility and multifunctionality to other known types of terminal assemblies. They are simple to make and offer theoretical tools for designing their structure and function. To demonstrate such assemblies, we combine cadmium telluride nanoparticles with cytochrome C protein and observe spontaneous formation of spherical supraparticles with a narrow size distribution. Such self-limiting behaviour originates from the competition between electrostatic repulsion and non-covalent attractive interactions. Experimental variation of supraparticle diameters for several assembly conditions matches predictions obtained in simulations. Similar to micelles, supraparticles can incorporate other biological components as exemplified by incorporation of nitrate reductase. Tight packing of nanoscale components enables effective charge and exciton transport in supraparticles and bionic combination of properties as demonstrated by enzymatic nitrate reduction initiated by light absorption in the nanoparticle.

Temperature mediated generation of armoured bubbles.

This communication describes a novel strategy for the continuous microfluidic generation of highly monodispersed particle-coated microbubbles using temperature-dependent dissolution of carbon dioxide.

Temperature-controlled 'breathing' of carbon dioxide bubbles.

We report a microfluidic (MF) approach to studies of temperature mediated carbon dioxide (CO(2)) transfer between the gas and the liquid phases. Micrometre-diameter CO(2) bubbles with a narrow size distribution were generated in an aqueous or organic liquid and subsequently were subjected to temperature changes in the downstream channel. In response to the cooling-heating-cooling cycle the bubbles underwent corresponding contraction-expansion-contraction transitions, which we term 'bubble breathing'. We examined temperature-controlled dissolution of CO(2) in four exemplary liquid systems: deionized water, a 0.7 M aqueous solution of NaCl, ocean water extracted from Bermuda coastal waters, and dimethyl ether of poly(ethylene glycol), a solvent used in industry for absorption of CO(2). The MF approach can be extended to studies of other gases with a distinct, temperature-dependent solubility in liquids.

Microbubbles loaded with nanoparticles: a route to multiple imaging modalities.

We report a single-step approach to producing small and stable bubbles functionalized with nanoparticles. The strategy includes the following events occurring in sequence: (i) a microfluidic generation of bubbles from a mixture of CO(2) and a minute amount of gases with low solubility in water, in an aqueous solution of a protein, a polysaccharide, and anionic nanoparticles; (ii) rapid dissolution of CO(2) leading to the shrinkage of bubbles and an increase in acidity of the medium in the vicinity of the bubbles; and (iii) co-deposition of the biopolymers and nanoparticles at the bubble-liquid interface. The proposed approach yielded microbubbles with a narrow size distribution, long-term stability, and multiple functions originating from the attachment of metal oxide, metal, or semiconductor nanoparticles onto the bubble surface. We show the potential applications of these bubbles in ultrasound and magnetic resonance imaging.