Photoconductive logic gate based on platinum decorated carbon nanotubes.

Electrical and nonlinear optical experiments were performed on multiwall carbon nanotubes (CNTs) prepared by a chemical vapor deposition method. We report that the incorporation of platinum particles on the CNTs surface originates an enhancement in the photoconductive properties with noticeable capabilities to modulate optical and electrical signals. The photoconductive logic gate function OR was experimentally demonstrated using a simple photoconductive platform based on our samples. A two-photon absorption effect was identified as the main mechanism of third-order optical nonlinearity under a nonresonant nanosecond excitation. Multiphotonic interactions were described in order to explain the observed behavior.

Spin-orbital effects in metal-dichalcogenide semiconducting monolayers.

Metal-dioxide &metal-dichalcogenide monolayers are studied by means of Density Functional Theory. For an accurate reproduction of the electronic structure of transition metal systems, the spin orbit interaction is considered by using fully relativistic pseudopotentials (FRUP). The electronic and spin properties of MX2 (M = Sc, Cr, Mn, Ni, Mo &W and X = O, S, Se &Te) were obtained with FRUP, compared with the scalar relativistic pseudopotentials (SRUP) and with the available experimental results. Among the differences between FRUP and SRUP calculations are giant splittings of the valence band, substantial band gap reductions and semiconductor to metal or non-magnetic to magnetic "transitions". MoO2, MoS2, MoSe2, MoTe2, WO2, WS2 and WSe2 are proposed as candidates for spintronics, while CrTe2, with µ ~ 1.59 µB, is a magnetic metal to be experimentally explored.

Comparison of Photomorphogenic Responses to UV Light in Red and White Cabbage (Brassica oleracea L.).

Photoinhibition of hypocotyl growth in white cabbage (Brassica oleracea L., cv "Bianco Brunswick") is controlled by UV absorbing receptor(s) and the phytochrome system, while in red cabbage (cv "Rosso Olandese tardivo invernale") phytochrome can act without any requirement for the action of a specific UV receptor. Similar results have been obtained for the photoregulation of anthocyanin production. Twenty-four hour preirradiations with UV light or 692 nanometers light lead to the same increase in responsiveness of the system toward Pfr in a following dark period, suggesting a phytochrome promotion of subsequent light induction for both.

Phytochrome-mediated induction of phenylalanine ammonia-lyase in the cotyledons of tomato (Lycopersicon esculentum Mill.) plants.

Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5.) induction in cotyledons from 96-h dark-grown Lycopersicon esculentum Mill. was studied in response to continuous light and hourly light pulses (blue, red, far red). The increases of PAL promoted by blue and red pulses are reversed completely by immediately following 758 nm irradiations. The response to continuous red light could be substituted for by hourly 6-min red light pulses. The effect of continuous red treatments is mainly due to a multiple induction effect of phytochrome. In contrast to red light, hourly light pulses with far red and blue, light can only partially substitute for continuous irradiation. The continuous blue response could be due to a combination of a multiple induction response and of a high irradiance response of phytochrome. The continuous far red response, could represent a high irradiance response of phytochrome. Dichromatic irradiations indicate that phytochrome is the photoreceptor controlling the light response (PAL) in tomato seedlings.

Photomorphogenic responses to UV radiation: Involvement of phytochrome and UV photoreceptors in the control of hypocotyl elongation in Lycopersicon esculentum.

The photo-inhibition of Lycopersicon esculentum Mill, hypocotyl growth induced by UV radiation may be mediated by both phytochrome and UV-absorbing receptors. The inhibition of growth induced by continuous irradiation with high fluence rate UV radiation is similar in the au mutant, which is severely deficient in spectrophoto metrically and immunochemically detectable phytochrome, and in the isogenic wild type. Parallel irradiation with 692 nm light, which is equivalent to UV radiation for the phytochrome system in our experimental conditions, induced at high photon fluence rates a significant increase in hypocotyl growth in the au mutant. The same light treatments inhibited the hypocotyl growth of the wild type. The responses of water-grown seedlings and chlorophyll-free seedlings (streptomycin and norflurazon treated seedlings) were compared. Water-grown and chlorophyll-free seedlings responded similarly to UV radiation. The presence of chlorophyll correlates with a significant increase in hypocotyl growth of au mutants irradiated with 692 nm light. These results support the conclusion that UV-induced inhibition of growth in the au mutant is independent of phytochrome.