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An experiment was conducted on Catharanthus roseus to study the effect of seed treatments with native diazotrophs on its seedling growth and antioxidant enzyme activities. The treatments had significant influence on various seedling parameters. There is no significant influence on dry matter production with the diazotrophs, Azospirillum and Azotobacter. However, the vital seedling parameters such as germination percentage and vigour index were improved. Azotobacter treatment influenced maximum of 50% germination, whereas Azospirillum and Azotobacter were on par with C. roseus with respect to their vigour index. There was significant difference in the population of total diazotrophs. Azospirillum and Azotobacter between rhizosphere and non-rhizosphere soils of C. roseus had the same trend and were observed at various locations of the study. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased to a significant extent due to the treatment with diazotrophs.

In this paper we report the linear and nonlinear optical properties of Bi-doped ZnO nanoparticles. Bi-doped ZnO nanoparticles were prepared through the wet chemical method at room temperature. Optical absorption measurements show that the exciton peaks are situated at 272 and 368 nm, which are attributed to the n=2 and n=1 exciton states, respectively. Transmission electron microscopy measurements reveal the size and shape of the particles and energy dispersive X-ray measurements confirm the doping of Bi in ZnO. Steady state photoluminescence measurements show that the emission is composed of five peaks. Open aperture z-scan measurements done at 532 nm using 5 ns, 300 μJ laser pulses reveal nonlinear absorption which arises from an effective three-photon absorption process.

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International audienceWe investigate the dielectric response of single-walled carbon nanotubes dispersed in poly(vinyl alcohol) matrix by using terahertz time domain spectroscopy. Frequency-dependent real and imaginary parts of the complex dielectric function are measured experimentally in the terahertz regime. The low-frequency phonons of carbon nanotubes, though predicted theoretically, are directly observed for the first time at frequencies 0.26, 0.60, and 0.85 THz. Further, a broad resonance is observed at 1.15 THz associated with the longitudinal acoustic mode of vibration of straight-chain segments of the long polymeric molecules in the film. The latter is observed at 1.24 THz for a pristine polymer film and has been used to derive the size of crystalline lamellae in the film