Chemistry, Department of

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Synthesis of Ag Nanostructures by Photochemical Reduction Using Citrate-Capped Pt Seeds

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2011
Abstract: 

A simple synthesis of Ag nanostructures such as nanorods and nanowires has been demonstrated with citrate-capped Pt seeds. UV-visible spectra and photographs of the synthesized solutions at different UV exposure times showed that the citrate-capped Pt seed played a crucial role in the growth of Ag nanostructures. After UV exposure of the colloidal solution for 60 min, the average diameter, length, and aspect ratio of the Ag nanostructures were about 95 nm, 2.1 nm, and 22, respectively. The photochemical reduction is hypothesized to result from photoelectron transfer from adsorbed citrate to Pt nanoparticle seed allowing Ag ions to form Ag nanostructures. Based on X-ray diffraction spectra and transmission electron microscope images, the synthesized Ag nanostructures were a face-centered cubic single crystal with good purity. These results suggest that the photochemical reduction method can provide Ag nanostructures in the presence of citrate-capped Pt seeds at room temperature for anisotropic Ag products.

Document type: 
Article

New Insights into Honey Bee (Apis mellifera) Pheromone Communication. Is the Queen Mandibular Pheromone Alone in Colony Regulation?

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2010
Abstract: 

Background: In social insects, the queen is essential to the functioning and homeostasis of the colony. This influencehas been demonstrated to be mediated through pheromone communication. However, the only social insect forwhich any queen pheromone has been identified is the honey bee (Apis mellifera) with its well-known queenmandibular pheromone (QMP). Although pleiotropic effects on colony regulation are accredited to the QMP, thispheromone does not trigger the full behavioral and physiological response observed in the presence of the queen,suggesting the presence of additional compounds. We tested the hypothesis of a pheromone redundancy in honeybee queens by comparing the influence of queens with and without mandibular glands on worker behavior andphysiology.Results: Demandibulated queens had no detectable (E)-9-oxodec-2-enoic acid (9-ODA), the major compound in QMP,yet they controlled worker behavior (cell construction and queen retinue) and physiology (ovary inhibition) asefficiently as intact queens.Conclusions: We demonstrated that the queen uses other pheromones as powerful as QMP to control the colony. Itfollows that queens appear to have multiple active compounds with similar functions in the colony (pheromoneredundancy). Our findings support two hypotheses in the biology of social insects: (1) that multiple semiochemicalswith synonymous meaning exist in the honey bee, (2) that this extensive semiochemical vocabulary exists because itconfers an evolutionary advantage to the colony.

Document type: 
Article