Recent development of nanotechnology has reshaped the landscape of modern science and technology, while in the meantime raised concerns about the adverse effects of nanomaterials on biological systems and the environment. [1,2] Owing to their mutual interaction, carbon-based nanomaterials readily aggregate and are not considered potential contaminants in the liquid phase. [3] However, when discharged into the environment, the hydrophobicity of nanomaterials can be averted through their interaction with natural organic matter (NOM), [4] a heterogeneous mixture of decomposed animals and plants and a major pollutant carrier [5] in nature. Consequently, mobile NOM-modified nanomaterials may pose a threat to ecological terrestrial species through further physical, chemical, and biological processes.The impact of nanomaterials on high plants has scantly been examined in the current literature. Among the studies available, [6][7][8][9][10][11][12] none have used major food crops or carbon nanoparticles (a major class of nanomaterials) for their evaluations. Although both enhanced and inhibited growth have been reported for vegetations exposed to nanomaterials at various developmental stages, [6][7][8][9][10][11][12] including seed germina-tion, root growth, and photosynthesis, fundamental questions remain regarding the uptake, accumulation, translocation, and transmission of nanomaterials in plant cells and tissues, and the impact of these processes on plant reproduction. [13] Here, we provide the first evidence on the uptake, accumulation, and generational transmission of NOM-suspended carbon nanoparticles in rice plants, the staple food crops of over half the world's population. The data presented in this Communication suggest the potential impact of nanomaterial exposure on plant development and the food chain, and prompt further investigation into the genetic consequences through plantnanomaterial interactions.NOM in freshwater ecosystems ususally has a concentration between 1-100 mg L À1 . [14] To mimic the natural ecosystems we formed a NOM solution of 100 mg L À1 in Milli-Q water and suspended fullerene C 70 and multiwalled carbon nanotubes (MWNTs) in the NOM. Using a Zetasizer (S90, Malvern Instruments) we identified three hydrodynamic diameters of 1.19 (major), 17.99, and 722.10 nm for C 70 -NOM and one major hydrodynamic diameter of 239.70 nm for MWNT-NOM (see Supporting Information, Sections 1C and 1D). The nonspecific assembly of NOM with C 70 or MWNTs is believed to be a dynamic equilibrium process [4] with the hydrophobic moieties of the NOM interacting and p-stacking with the hydrophobic carbon nanoparticle surfaces.Newly harvested rice seeds were incubated in Petri dishes that contained 15 mL of different concentrations of C 70 -NOM and MWNT-NOM in rice germination buffer. After germination at 25 AE 1 8C for 2 weeks the seedlings were transplanted to soil in big pots and grown in a green house to maturity without addition of nanoparticles. For each sample concentration, 5 pots of plants were maintained f...

Described herein are initial experimental details and properties of a silicon core, silica glass-clad optical fiber fabricated using conventional optical fiber draw methods. Such semiconductor core fibers have potential to greatly influence the fields of nonlinear fiber optics, infrared and THz power delivery. More specifically, x-ray diffraction and Raman spectroscopy showed the core to be highly crystalline silicon. The measured propagation losses were 4.3 dB/m at 2.936 microm, which likely are caused by either microcracks in the core arising from the large thermal expansion mismatch with the cladding or to SiO(2) precipitates formed from oxygen dissolved in the silicon melt. Suggestions for enhancing the performance of these semiconductor core fibers are provided. Here we show that lengths of an optical fiber containing a highly crystalline semiconducting core can be produced using scalable fiber fabrication techniques.

Engineered carbon nanostructures, such as multiwalled carbon nanotubes (MWNTs), are inherently hydrophobic and are not readily stable in aqueous media. However, the aqueous stability and bioavailability of these nanotubes may be influenced by the water quality parameters such as ionic strength, pH, and natural organic matter (NOM). Natural organic matter adsorbs onto the surface of MWNTs, effectively covering the hydrophobic surface and resulting in increased aqueous stability. This enhanced stability is likely to lead to an increased residence time in the water column and increased exposure times for pelagic organisms. In the current study, NOM from three different river systems in the southeast United States increased the stability of MWNT suspensions. The effects of these suspensions were evaluated using acute and chronic bioassays with Daphnia magna and Ceriodaphnia dubia. The 96-h LC50 for D. magna exposed to MWNTs suspended in Suwannee River (USA) NOM was approximately 2.0 mg/L and was not significantly influenced by NOM concentrations ranging from 1.79 to 18.5 mg/L DOC. However, there were differences in 96-h LC50 values among different sources of NOM (Suwannee, Black, and Edisto Rivers, USA). Daphnid growth was reduced in both D. magna and C. dubia, whereas reproduction was reduced in C. dubia. Characterization of the different NOM sources and MWNT suspensions was conducted. Visual inspection using transmission electron microscopy (TEM) and gut elimination observations suggested that the toxicity was attributable to ingested MWNTs clogging the gut tract of D. magna. The TEM micrographs indicated that MWNTs can disaggregate within the gut tract, but single MWNTs are unable to absorb across the gut lumen.

For the first time to the best of our knowledge a glass-clad optical fiber comprising a crystalline binary III-V semiconductor core has been fabricated. More specifically, a phosphate glass-clad fiber containing an indium antimonide (InSb) core was drawn using a molten core approach. The core was found to be highly crystalline with some oxygen and phosphorus diffusing in from the cladding glass. While optical transmission measurements were unable to be made, most likely due to free carrier absorption associated with the conductivity of the core, this work constitutes a proof-of-concept that optical fibers comprising semiconductor cores of higher crystallographic complexity than previously realized can be drawn using conventional fiber fabrication techniques. Such binary semiconductors may open the door to future fiber-based nonlinear devices.

Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. However, its correlation with carrier doping has not been reported. We report on the Meissner effect found in thin films consisting of assembled boron (B)-doped single-walled CNTs (B-SWNTs). We find that only B-SWNT films consisting of low boron concentration leads to evident Meissner effect with Tc=12 K and also that a highly homogeneous ensemble of the B-SWNTs is crucial. The first-principles electronic-structure study of the B-SWNTs strongly supports these results.

Precise determination of acceptors in the laser ablation grown B doped single-walled carbon nanotubes (SWCNTs) has been elusive. Photoemission spectroscopy finds evidence for subpercent substitutional B in this material, which leads to superconductivity in thin film SWNT samples.

The authors present the results of optical limiting measurements of ∼10nm wide bismuth nanorods suspended in chloroform. Their Z-scan measurements reveal that optical limiting under 532nm excitation stems from a strong nonlinear scattering (NLS) subsequent to nonlinear absorption (NLA) by suspension. On the other hand, the optical limiting is entirely due to NLA when excited with 1064nm excitation in the nanosecond regime. The occurrence of NLS at one wavelength and absence at another is unusual, especially when compared to the behavior of carbon nanotubes under similar conditions, in which NLS is dominant at both wavelengths.

Single-walled carbon nanotubes (SWNTs) with varying degrees of disorder were investigated using multiple-excitation Raman spectroscopy. The lattice disorder was imparted into the nanotubes by the addition of varying amounts of sulfur to the iron catalyst in a thermal chemical vapor deposition process. Changes in the intensities of peaks occurring due to a double resonance Raman process were studied. The intensity of the disorder-induced D band increased with a decrease in the sulfur content. Upon post-synthesis heat treatment, the double resonance process got quenched due to defect healing. The second order G' band and iTOLA bands exhibited a two-peak structure, of which one of the peaks is relatively more sensitive to defects and decreased in intensity with heat treatment.