Bacterially synthesized tellurium nanostructures for broadband ultrafast nonlinear optical applications.

Elementary tellurium is currently of great interest as an element with potential promise in nano-technology applications because of the recent discovery regarding its three two-dimensional phases and the existence of Weyl nodes around its Femi level. Here, we report on the unique nano-photonic properties of elemental tellurium particles [Te(0)], as harvest from a culture of a tellurium-oxyanion respiring bacteria. The bacterially-formed nano-crystals prove effective in the photonic applications tested compared to the chemically-formed nano-materials, suggesting a unique and environmentally friendly route of synthesis.

Percolating conductive networks in multiwall carbon nanotube-filled polymeric nanocomposites: towards scalable high-conductivity applications of disordered systems.

Disordered polymeric composite systems ordinarily exhibit poor bulk electronic transport properties, restricting their use to low-conductivity applications. In this work, highly electroconductive multi-walled carbon nanotube (MWCNT)/polyurethane (PU) nanocomposites were assembled via an aqueous solvent-blending method. Low percolation thresholds of 0.

Formation of tellurium nanocrystals during anaerobic growth of bacteria that use Te oxyanions as respiratory electron acceptors.

Certain toxic elements support the metabolism of diverse prokaryotes by serving as respiratory electron acceptors for growth. Here, we demonstrate that two anaerobes previously shown to be capable of respiring oxyanions of selenium also achieve growth by reduction of either tellurate [Te(VI)] or tellurite [Te(IV)] to elemental tellurium [Te(0)]. This reduction achieves a sizeable stable-Te-isotopic fractionation (isotopic enrichment factor [epsilon] = -0.

Single-walled carbon nanotube purification, pelletization, and surfactant-assisted dispersion: a combined TEM and resonant micro-raman spectroscopy study.

Resonant Raman spectroscopy and transmission electron microscopy were used to characterize the structural changes of three single-walled carbon nanotube samples processed with purification, pelletization, and surfactant-assisted dispersion. A two-stage purification process selectively removes metallic tubes as well as small-diameter ones, enriching large-diameter semiconducting tubes. Pelletizing reduces the intertube distance but greatly increases the intensity ratio of the D band to the G band.

Poly(L-lactide) (PLLA)/multiwalled carbon nanotube (MWCNT) composite: characterization and biocompatibility evaluation.

Much effort has been directed at the fabrication of carbon nanotubes (CNTs)/polymer composites and the characterization of their physical properties. Among them, composites comprising CNTs and the biocompatible polymers are of special interest due to their potential for specific biomedical applications. we report the preparation of the MWCNT/poly(L-lactide) composite and the corresponding spectroscopic (Raman) and the microscopic (SEM, TEM) characterization.

Aligned carbon nanotube-polymer hybrid architectures for diverse flexible electronic applications.

We present the fabrication and electrical characterization of a flexible hybrid composite structure using aligned multiwall carbon nanotube arrays in a poly(dimethylsiloxane) (PDMS) matrix. Using lithographically patterned nanotube arrays, one can make these structures at any length scale from submicrometer levels to bulk quantities. The PDMS matrix undergoes excellent conformal filling within the dense nanotube network, giving rise to extremely flexible conducting structures with unique electromechanical properties.

Doping properties of polydithienylmethine: a study on the correlation between polymer chain length, spectroscopy, and transport.

(1S)-(+)-10-Camphorsulfonic acid-doped polydithienylmethine was prepared through an acid-catalyzed condensation reaction of alpha,alpha'-di-2-thienyl-(2,2'-bithiophene)-5,5'-dimethanol and was characterized by 1H NMR spectroscopy and size exclusion chromatography (SEC). The electronic and vibrational properties of the resulting polymer thin films vary with the loadings of the (1S)-(+)-10-camphorsulfonic acid. The dark conductivity and drift mobility, which is significantly high, of the polymer thin films were enhanced with increasing doping levels and reached maximum values of 8.

Meso-structure formation for enhanced organic photovoltaic cells.

[reaction: see text] Formation of a controlled fullerene mesophase within an organic host system has enabled us to create high-power conversion efficiency photovoltaics. This mesophase is formed using thermal gradients that provide a fluidic mobility of the fullerenes allowing for greater dispersion of nanocrystalline 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61 (PCBM) within regioregular poly(3-hexylthiophene) (P3HT). From this reorganization of the component materials in the matrix the overall efficiency of the system jumps dramatically from the roughly 2.

Structural and spectral features of selenium nanospheres produced by Se-respiring bacteria.

Certain anaerobic bacteria respire toxic selenium oxyanions and in doing so produce extracellular accumulations of elemental selenium [Se(0)]. We examined three physiologically and phylogenetically diverse species of selenate- and selenite-respiring bacteria, Sulfurospirillum barnesii, Bacillus selenitireducens, and Selenihalanaerobacter shriftii, for the occurrence of this phenomenon. When grown with selenium oxyanions as the electron acceptor, all of these organisms formed extracellular granules consisting of stable, uniform nanospheres (diameter, approximately 300 nm) of Se(0) having monoclinic crystalline structures.