Fluorescent oxide nanoparticles adapted to active tips for near-field optics

We present a new kind of fluorescent oxide nanoparticles with properties well suited to active-tip based near-field optics. These particles with an average diameter in the range 5-10 nm are produced by Low Energy Cluster Beam Deposition (LECBD) from a YAG:Ce3+ target. They are studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), classical photoluminescence, cathodoluminescence and near-field scanning optical microscopy (NSOM). Particles of extreme photo-stability as small as 10 nm in size are observed. These emitters are validated as building blocks of active NSOM tips by coating a standard optical tip with a 10 nm thick layer of YAG:Ce3+ particles directly in the LECBD reactor and by subsequently performing NSOM imaging of test surfaces.Comment: Changes made following Referee's comments; added references; one added figure. See story on this article at: http://nanotechweb.org/cws/article/tech/3606

Optical investigation of broadband white-light emission in self-assembled organic-inorganic perovskite (C6H11NH3)2PbBr4

The performance of hybrid organic perovskite (HOP) for solar energy conversion is driving a renewed interest in their light emitting properties. The recent observation of broad visible emission in layered HOP highlights their potential as white-light emitters. Improvement of the efficiency of the material requires a better understanding of its photophysical properties. We present in-depth experimental investigations of white-light (WL) emission in thin films of the (C6H11NH3)2PbBr4. The broadband, strongly Stokes shifted emission presents a maximum at 90 K when excited at 3.815 eV, and below this temperature coexists with an excitonic edge emission. X-rays and calorimetry measurements exclude the existence of a phase transition as an origin of the thermal behavior of the WL luminescence. The free excitonic emission quenches at low temperature, despite a binding energy estimated to 280 meV. Time-resolved photoluminescence spectroscopy reveals the multicomponent nature of the broad emission. We analyzed the dependence of these components as a function of temperature and excitation energy. The results are consistent with the existence of self-trapped states. The quenching of the free exciton and the thermal evolution of the WL luminescence decay time are explained by the existence of an energy barrier against self-trapping, estimated to ∼10 meV.This work was supported by the PHC MAGHREB program no. 13MAG08&30255ZJ, the “Agence Nationale de la Recherche” (ANR project BISTA-MAT: ANR-12-BS07-0030-01), Spanish MINECO (through the grant MAT2013-44063-R), Université de Versailles Saint-Quentin-En-Yvelines, CNRS, and Université de Sfax, which we deeply acknowledge.Peer Reviewe

Irrigation Scheduling Based on the Crop Water Stress Index and Precision Water Application for High Cotton Yield

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.A modified, low- pressure linear move irrigation system was used to irrigate cotton at the Marana Agricultural Center, University of Arizona in 1985. Irrigations were scheduled using the Crop Water Stress Index (CWSI) for timing and a neutron probe to determine soil moisture deficits. Irrigations were applied when the CWSI reached 0.1 resulting in minimal seasonal water stress. Yields ranged from 3.14 bales /acre to 2.73 bales/acre from 2 acre plots. Total applied water ranged from 31.3 inches to 32.3. Total seasonal rainfall was 2.90 inches

Scheduling Pima Cotton Irrigations Using Infrared Thermometers

Plots of pima S-6 cotton were scheduled for irrigation using the Crop Water Stress Index (CWSI). Irrigations were applied when CWSI levels reached 0.08 (wet), 0.34 (medium), and 0.68 (dry) units. The medium treatment had significantly higher lint yield. Preliminary test results indicate the CWSI can be useful in irrigation-management decisions regarding pima cotton production

Evaluation of Two Levels of Irrigation in Relation to Calsweet Watermelon Yield

Calsweet watermelons were irrigated at two levels, utilizing a drip irrigation system for accurate rate measurements. Number and weight of harvested melons were recorded for four harvest dates. There were no significant differences in weight per melon, number of melons and total mean weight for the water treatments within the four harvest dates. For the entire season, number and total weight of melons were higher in the wet treatment; the weight per melon was higher in the dry treatment

The Response of Table Grape Growth, Production, and Ripening to Water Stress

Four year old 'Flame Seedless' grapevines, located in a commercial vineyard, were subjected to increased water stress levels based on infrared canopy temperatures and the Crop Water Stress Index (CWSI) for two years. CWSI levels were approximately .18, .30 and .33 for the wet, medium and dry treatments. In the first year there were no significant differences in yield however, there was a significant reduction in the amount of water applied in both the medium and dry treatments when compared to the wet treatment. In addition, the wet treatment had significantly greater growth during the first growing season when comparing pruning weights.Sponsored by the Arizona Citrus Research Counci