G1 dendrimers-mediated evolution of silver nanostructures from nanoparticles to solid spheres.
With the control of G1 poly(amidoamine) (PAMAM), an evolutionary course of stable colloidal silver from discrete nanoparticles to solid spheres through ultraviolet irradiation reduction of silver nitrate solutions was observed by transmission electron microscopy (TEM). The morphologies of the products depend on the Ag+ concentration. A mechanism of globular assembly was put forward to interpret the evolution of the nanostructures. Powder X-ray diffraction (XRD), electron diffraction (ED) patterns, and X-ray photoelectron spectroscopy (XPS) indicate the presence of cubic symmetry silver. XPS and Fourier transform infrared (FT-IR) spectroscopy confirm that dendrimers have participated in the stabilization and control of Ag nanostructures. In the UV-vis spectra, the intense surface plasmons are centered at 425 and 430 nm corresponding to the shapes of dots and solid spheres, respectively. The solid spheres exhibit excellent catalytic efficiency on the reduction of 2,7-dicholoroflurescein (DCF).
Dendrimer templated construction of silver nanoparticles.
Silver nanoparticles continue to evoke great current interest due to their tremendous potential in designing smart materials for a wide variety of applications. Much emphasis has been placed lately in developing methodologies that could modulate the size and shape of these metal particles. Dendrimers that are monodisperse in nature with a regular and highly branched three-dimensional architecture, provide a useful platform to accomplish this goal. These hyperbranched macromolecules have been widely explored as templates in the construction of silver metal nanoparticles, and this review aims to provide a detailed overview of dendrimer-assisted synthesis of silver nanoparticles.
Transmission of Oropouche virus from man to hamster by the midge Culicoides paraensis.
Oropouche virus (arbovirus family Bunyaviridae, Simbu serological group) was experimentally transmitted from man to hamster by the bite of the midge Culicoides paraensis. Infection rates and transmission rates were determined after the midge had engorged on patients with viremia. The threshold titer necessary to enable infection or transmission by the midges was approximately 5.3 log10 of the median lethal dose of the virus in suckling mice per milliliter of blood. Transmission was achieved 6 to 12 days after C. paraensis had taken the infective blood meal. This represents conclusive evidence of transmission of an arbovirus of public health importance to man by a member of the Ceratopogonidae family.