Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed

Carbon Nanotubes in Tissue Engineering

For their peculiar features carbon nanotubes (CNTs) are emerging in many areas of nanotechnology applications. CNT-based technology has been increasingly proposed for biomedical applications, to develop biomolecule nanocarriers, bionanosensors and smart material for tissue engineering purposes. In the following chapter this latter application will be explored, describing why CNTs can be considered an ideal material able to support and boost the growth and the proliferation of many kind of tissues

Phylogeography of the Microcoleus vaginatus (Cyanobacteria) from Three Continents – A Spatial and Temporal Characterization

It has long been assumed that cyanobacteria have, as with other free-living microorganisms, a ubiquitous occurrence. Neither the geographical dispersal barriers nor allopatric speciation has been taken into account. We endeavoured to examine the spatial and temporal patterns of global distribution within populations of the cyanobacterium Microcoleus vaginatus, originated from three continents, and to evaluate the role of dispersal barriers in the evolution of free-living cyanobacteria. Complex phylogeographical approach was applied to assess the dispersal and evolutionary patterns in the cyanobacterium Microcoleus vaginatus (Oscillatoriales). We compared the 16S rRNA and 16S-23S ITS sequences of strains which had originated from three continents (North America, Europe, and Asia). The spatial distribution was investigated using a phylogenetic tree, network, as well as principal coordinate analysis (PCoA). A temporal characterization was inferred using molecular clocks, calibrated from fossil DNA. Data analysis revealed broad genetic diversity within M. vaginatus. Based on the phylogenetic tree, network, and PCoA analysis, the strains isolated in Europe were spatially separated from those which originated from Asia and North America. A chronogram showed a temporal limitation of dispersal barriers on the continental scale. Dispersal barriers and allopatric speciation had an important role in the evolution of M. vaginatus. However, these dispersal barriers did not have a permanent character; therefore, the genetic flow among populations on a continental scale was only temporarily present. Furthermore, M. vaginatus is a recently evolved species, which has been going through substantial evolutionary changes

Directed Self-Assembly: Expectations and Achievements

Nanotechnology has been a revolutionary thrust in recent years of development of science and technology for its broad appeal for employing a novel idea for relevant technological applications in particular and for mass-scale production and marketing as common man commodity in general. An interesting aspect of this emergent technology is that it involves scientific research community and relevant industries alike. Top–down and bottom–up approaches are two broad division of production of nanoscale materials in general. However, both the approaches have their own limits as far as large-scale production and cost involved are concerned. Therefore, novel new techniques are desired to be developed to optimize production and cost. Directed self-assembly seems to be a promising technique in this regard; which can work as a bridge between the top–down and bottom–up approaches. This article reviews how directed self-assembly as a technique has grown up and outlines its future prospects

Magnetomicelles: Composite nanostructures from magnetic nanoparticles and cross-linked amphiphilic block copolymers

We report the synthesis, characterization, and covalent surface chemistry of "magnetomicelles", cross-linked, amphiphilic block-copolymer micelles that encapsulate superparamagnetic iron oxide nanoparticles. Because these composite nanostructures assemble spontaneously from solution by simultaneous desolvation of nanoparticle and amphiphilic poly(styrene 250-block/acrylic acid 13) components, explicit surface functionalization of the particles is not required, and the encapsulation method was applied to different magnetic nanoparticle sizes and compositions. TEM images of the magnetomicelles illustrated that the number of encapsulated particles could be dictated rationally by synthetic conditions. The magnetic properties of the particles were characterized by SQUID magnetometry and followed the general Langevin magnetic model for superparamagnetic materials. The micellar shells of these particles were functionalized using covalent chemistry that would not ordinarily be possible on the magnetic particle surface. As a result, this noncovalent approach provides a new route to technological applications of hydrophobic magnetic nanomaterials that lack appropriate conjugate surface chemistry.close22318

Homogeneous, coaxial liquid crystal domain growth from carbon nanotube seeds

We have developed a general method for aligning anisotropic materials by using carbon nanotubes to influence order in the surrounding material. Specifically, we have shown that carbon nanotubes seed the formation of oriented domains in a liquid crystalline polymer (LCP). Using polarized light microscopy, we have observed that the molecular alignment in these large (10-100 ??m long) domains is homogeneous and controlled by the direction of the nanotube nucleus. The kinetic nature of this nucleation process was verified by differential scanning calorimetry. The coupling of preferential nucleation and controlled seed orientation may allow bulk LCP materials to be aligned by simply preorganizing a small number of dispersed nanotube seeds. We expect that this work will aid in the development and application of macroscopically ordered nanostructured composite materials.close394