Single-slit laser diffractography was used to image the growth of carbon nanotubes. A silicon dioxide slit with a minimum width of 150 μm was prepared and positioned inside a chemical vapor deposition (CVD) reactor in alignment with a laser source. Carbon nanotubes were grown inside the slit width, producing corresponding changes in the diffraction pattern due to the optical opacity of these structures and to their high density and alignment. Changes in the diffraction pattern were recorded and used for the direct measurement of nanotube growth. The results show an exponential increase of length vs time for 45 min experiments, best fit with a double exponential function, which is interpreted in terms of the concurrence of base-growth and tip-growth modes for successive catalyst particles. Scanning electron microscopy confirms the diffractographic data at a high level of precision. The innovation brought by this in situ method to the kinetic study of nanotube synthesis is discussed and compared to a posteriori studies based solely on microscopy for a range of different nanotube lengths.

The field of research focused on the synthesis of micro- and nanoparticles has not yet conclusively addressed the challenges presented by the hierarchical control of surface topography. An established approach to hierarchical multicomposite nanostructured particles is based on template-directed synthesis, while spectacular advances have been reached in nanoparticle fabrication based on a variety of physicochemical processes. These results exemplify an additive route to hierarchical control, where multiple layers are stacked onto each other or where discretely identifiable particles are assembled into a larger spherical conglomerate. We present here a new strategy for the synthesis of micro- and nanoparticles, which we refer to as "textured isomorphic synthesis", that uses only the toolbox of inorganic chemistry coupled to the physics of cavitation, viscous fingering, and bubble nucleation. The results illustrate a topological route to hierarchical control of particle topography where dimples or holes are deterministically introduced on a planar substrate later transformed into isomorphic hollow spherical micro- and nanostructures.

Arrays of catalytically-grown multi-wall carbon nanotubes were grown using identical conditions in a chemical vapor deposition environment, but cooled at different cooling rates, to identify the influence of cooling rate on the structural properties of the nanotube at the catalyst-wall interface. Ex-situ transmission electron microscopy led to the identification of twist, twin, and tilt domain boundaries in all samples irrespective of cooling rate. In addition, the relative position of twist, twin, and tilt domain boundaries in nanotubes cooled at different rates was maintained uniformly across all samples cooled at different rates. The results are interpreted in light of the concurrence of base- and tip-growth for the catalytic synthesis of nanotubes, suggesting a rather steady position occupied by the domain boundaries coupled to the catalytic particles.

Ex situ transmission electron microscopy (TEM) performed on catalytically grown multiwall carbon nanotubes identified two types of catalyst−nanotube wall interfaces. The interfaces consisted of crystalline domains with different orientations:  twist and twin boundaries in correspondence with quasi-spherical particles closer to the nanotube base and tilt boundaries in correspondence with high aspect ratio, tapered particles further from the base. TEM suggests that the domain boundaries maintain a rather steady position coupled to the catalytic particles, whereas the carbon atoms precipitate along the nanotube axis away from the particles. It is concluded that the relative movement of the carbon atoms with respect to the dislocations comprising the nanotube domain boundary located at the catalyst−wall interface is a significant elementary process in nanotube crystal growth driven by surface diffusion. The results appear consistent with the concurrence of base and tip growth for the catalytic synthesis of carbon nanotubes.

The present study was motivated by the need for accurately-controlled and wellcharacterized novel bionaterial formulations for the study of cell-protein-material interactions. For this purpose, the current research has focused on the design, fabrication and characterization of model native oxide-coated silicon surfaces decorated with silica nanoparticles of select sizes, and has examined the adhesion of osteoblasts and fibroblasts on these nanoparticle-decorated surfaces. The results demonstrate the capability to deposit nanoparticles of select diameters and substrate surface coverage onto native silicon oxide-coated silicon, the firm attachment of these nanoparticles to the underlying native silicon oxide, and that nanoparticle size and coverage modulate adhesion of osteoblasts and fibroblasts to these substrates. The material formulations tested provide a well-controlled and well-characterized set of model substrates needed to study the effects of nanoscale features on the functions of cells that are critical to the clinical fate of implantable biomaterials.