Graphene quantum dot (GQD) layers were deposited as an energy-down-shift layer on crystalline-silicon solar cell surfaces by kinetic spraying of GQD suspensions. A supersonic air jet was used to accelerate the GQDs onto the surfaces. Here, we report the coating results on a silicon substrate and the GQDs' application as an energy-down-shift layer in crystalline-silicon solar cells, which enhanced the power conversion efficiency (PCE). GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density was enhanced by about 2.94% (0.9 mA/cm(2)) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).

Production of Bradyrhizobium japonicum inoculants is problematic because high inoculation rates are necessary but expensive, while production of rhizobial Nod factors (lipo-chitooligosaccharides (LCOs)), key signal molecules in the establishment of legume-rhizobia symbioses, may be inhibited at high culture cell densities. We conducted experiments to determine the effects of growth medium N source on B. japonicum growth, LCO production, and early nodulation of soybean. We found that 1.57 mmol ammonium nitrate x L(-1) resulted in less rhizobial growth and rhizobial capacity to produce LCOs (on a per cell basis) than did 0.4 g yeast extract x L(-1), which contained the same amount of N as the ammonium nitrate. Increasing yeast extract to 0.8 g x L(-1) increased rhizobial growth and LCO production on a volume basis (per litre of culture) and did not affect cell capacity to produce LCOs; however, at 1.4 g yeast extract x L(-1) per cell, production was reduced. A mixture of 0.8 g yeast extract x L(-1) and 1.6 g casein hydrolysate x L(-1) resulted in the greatest bacterial growth and LCO production on a volume basis but reduced LCO production per cell. Changes in organic N level and source increased production of some of the measured LCOs more than others. LCO production was positively correlated with cell density when expressed on a volume basis; however, it was negatively correlated on a per cell basis. We conclude that although quorum sensing affected Nod factor production, increased levels of organic N, and specific compositions of organic N, increased LCO production on a volume basis. Greenhouse inoculation experiments showed that the medium did not modify nodule number and N fixation in soybean, suggesting that it could have utility in inoculant production.

[951][952][953][954][955][956][957][958][959][960][961][962][963][964][965][966]. The combination of rising fossil fuel prices and a need to reduce greenhouse gas emissions will lead to expanded use of crop inoculants (bio-fertilizers) both for increased production of biomass (for bio-fuels and soil C storage) and to reduce production of nitrous oxide, through increased reliance on biological nitrogen fixation. Over the last century inoculants have been improved through strain selection, improved carriers (including sterile carriers), and increased cell densities. During the last few decades our understanding of signalling between symbiotic bacteria and plants has expanded enormously, with the signalling between rhizobia and their legume hosts being the model system. Recent work has shown that adverse environmental conditions can inhibit this signalling and that addition of plant-to-microbe signals into inoculants can help overcome this. This is also true of addition of the microbe-to-plant signals that act as the return signals of this system; however, they have also been shown to cause a general and direct stimulation of plant growth that is not yet well understood. Finally, very recent work has shown that some of the plant growth-promoting rhizobacteria produce novel signal compounds that stimulate plant growth. This is a time of rapid increase in understanding with regard to plant-microbe signalling; the use of these signals in commercial inoculants offers a new wave in innovations for this industry at a time when there is great need.Key words: Inoculants, rhizobacteria, rhizobia, signalling Mabood, F., Gray, E. J., Lee, K. D., Supanjani, et Smith D. L. 2006. Exploitation de la médiation chimique entre les organismes pour créer de meilleurs inoculants. Can. J. Plant Sci. 86: 951-966. La hausse du prix des combustibles fossiles et la néces-sité de réduire les émissions de gaz à effet de serre déboucheront sur une utilisation accrue des inoculants en agriculture (engrais biologiques) pour la production d'une plus grande quantité de biomasse (pour les biocarburants et le stockage du carbone dans le sol) mais aussi pour la réduction des dégagements d'oxydes nitreux par un plus grand recours à des mécanismes biologiques pour fixer l'azote dans le sol. Au cours du siècle dernier, on a raffiné les inoculants par la sélection, amélioré les excipients (y compris les substrats stériles) et accru la population de cellules. Durant les quelque dernières décennies, nos connaissances sur les signaux que s'échangent microorganismes et végétaux en symbiose se sont considérablement élargies et le système de signalisation entre les rhizobiums et les légumineuses qui sont leur hôte est devenu un modèle du genre. Des recherches récentes indiquent que des conditions environnementales difficiles peuvent nuire à l'échange de signaux et qu'on peut surmonter ce problème en ajoutant des médiateurs plante-microorganisme à l'inoculant. La même remarque s'applique à l'addition de médiateurs microorganisme-plante qui véhiculent la répons...

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