A novel process for the formation of pairs of opposing metallic nanotips within linear trenches on a silicon wafer is investigated in detail. The process is based on a spreading knife technique typically used in nanosphere lithography to generate monolayers of colloidal polystyrene beads. Here it is applied to initiate self-assembly of spheres in long linear trenches acting as a template for the sphere arrangement. The optimum blade velocity to deposit the spheres selectively and densely packed in the trench depends on the trench surface fraction and can be described by a modified Dimitrov model. It is demonstrated that the spheres can be used as a shadow mask to deposit metallic nanotips in a channel, which are electrically interconnected on each side of the trench, possibly enabling the control and manipulation of nanoobjects in the channel.

Self–assembly of molecular building blocks provides an interesting route to produce well-defined chemical structures. Tailoring the functionalities on the building blocks and controlling the time of self-assembly could control the properties as well as the structure of the resultant patterns. Spontaneous self-assembly of biomolecules can generate bio-interfaces for myriad of potential applications. Here we report self-assembled patterning of human serum albumin (HSA) protein in to ring structures on a polyethylene glycol (PEG) modified gold surface. The structure of the self-assembled protein molecules and kinetics of structure formation entirely revolved around controlling the nucleation of the base layer. The formation of different sizes of ring patterns is attributed to growth conditions of the PEG islands for bio-conjugation. These assemblies might be beneficial in forming structurally ordered architectures of active proteins such as HSA or other globular proteins.

An experimental analysis of the morphology changes of hexagonally close packed polystyrene sphere monolayers induced by annealing in air is presented. The triangular interstices between each triple of spheres, which are frequently used as nanoscale mask openings in colloidal lithography, are observed to gradually shrink in size and change in shape upon annealing. Top view scanning electron microscopy images reveal that different stages are involved in the closure of monolayer interstices at annealing temperatures in the range between 110°C and 120°C. In the early stages shrinkage of the triangular interstices is dominated by material transport to and thus shortening of their corners, in the late stages interstice area reduction via displacement of the triangle edges becomes significant. At intermediate annealing times the rate of interstice area reduction displays a maximum before a stabilized state characterized by a rounded isosceles triangular shape forms.

The meso-scale hexagonally packed order structures were obtained by solvent casting from the immiscible polymer blend solutions. The order structures were the result of phase separation occurred at the evaporation front during the solvent casting, the so-called dissipative system. The order domains were flat spheres or ellipses on the matrix surface depending on the combination of polymer blends and solvent, the diameter of spheres were tunable from 0.5 to 3 μm by the casting condition, such as the solvent used for mixing and the evaporation rate. Three blend systems, NBR/SBR, NBR/BR and PMMA/BR, formed two dimensional order structures with the domain size in μm-scale by solvent casting from those homogeneous solutions. The conditions to obtain the two dimensional meso-scale order structure were evaluated.

Mesoporous Fe3O4 nanoparticles coated with ZnO nanocrystals were successfully synthesized by a simple solution method at low temperature. The transmission electron microscopy analysis indicates that the mesoporous Fe3O4 nanoparticles are monodispersed with a mean diameter of 160 nm and the thickness of ZnO layer is 15 nm approximately. The porosity of the products was further substantiated by the nitrogen (N2) sorption measurement. The N2 adsorption-desorption isotherm curve can be identified as type IV, which is a characteristic of mesopores. Electromagnetic (EM) wave absorption properties of the as-prepared Fe3O4@ZnO mesoporous spheres-wax composites were investigated at a room temperature in the frequency range of 0.5∼18 GHz. Interestingly, the Fe3O4@ZnO mesoporous spheres exhibit an enhanced EM wave absorption due to the mesoporous structure. The multiple absorbing mechanisms result from the interface polarization induced by the special core/shell and mesoporous structures as well as dipole polarization of both Fe3O4 and ZnO. The results demonstrate that the Fe3O4@ZnO mesoporous spheres are attractive candidates for a new kind of EM wave absorption materials with wide absorption frequency band.

In order to study the oriented aggregation of BaTiO3nanocrystals in the ultrasound-assisted synthesis in an aqueous solution [F.Dang et al., Jpn.J.Appl.Phys. 48, 09KC02 (2009)], the electric dipole-dipole interaction model has been studied by numerical simulations. The results of the numerical simulations are consistent with the experimental ones if the electric dipole moment of a primary particle (a nanocrystal) of 5 nm in diameter is about 10 D =3.3 x 10-29 (C m). It suggests that a 5-10 nm BaTiO3 nanocrystal synthesized in an aqueous solution with ultrasound has spontaneous polarization.

We report on a new class of materials for laser printer toner applications. These materials were prepared from methacrysilane-in-water emulsions stabilized with colloidal silica particles. In this elegant system, the colloidal silica particles reside at the water/oil interface helping to emulsify the oil droplet, self-organizing into a raspberry-like morphology. The emulsion formation is followed by free-radical polymerization, hydrophobic treatment, and drying steps. This one pot synthesis in water affords a hydrophobic material with a particle size in the range of 80 to 300 nm. The particle size could be fine-tuned by changing the oil-to-silica mass ratio or by using colloidal silica particles of different sizes. Results of material characterization by solid-state NMR, electron microscopy, and particle size measurements methods will be presented. Examples of possible extensions of the synthesis towards materials with methacrylsilane partially substituted with other methacrylates will be provided. Application of the new material in toners will be described as will the comparison of its performance with the incumbent material - hydrophobic colloidal silica.

A facile and novel method of fabricating large-area-patterned monolayer of polytetrafluoroethylene(PTFE) nanoparticles was achieved using surface charge induced colloidal deposition. Chemical processes of amination and hydroxylation were used to make the silicon substrates positively and negatively charged, respectively, while the PTFE colloidal nanoparticles were anisotropic and negatively charged. After colloidal deposition, an ordered monolayer with microholes was formed on the amination surface, while an island-like monolayer was achieved on the hydroxylation surface. Both of the two kinds of monolayers were as large as 1.5 square centimeters. It is worth pointing out that these large-area-patterned monolayers were fabricated without any templates and the whole process only took several hours. The formation mechanism of the different structures can be generally attributed to the cooperation and competition of three-body, two-body and particle-wall interactions. It is believed that the interesting patterned monolayer formation mechanism, high production efficiency, good adaptability and quality will make this novel method attractive.

The interest for surface patterning presents a fast increasing in the last few years due to several factors ranging from miniaturization trends and sensor design to worries about the absorption of carcinogenic molecules on inhalable particles. Although the existence of a vast literature regarding the self-assembly and patterning of nanoparticles on different types of surfaces, it remains unclear the dynamics and main mechanisms behind the formation and maintenance of two-dimensional symmetric patterns of small molecules on top of surfaces. In this contribution, we report initial results on an investigation on the similarities between the well-known Abrikosov hexagonal lattices in superconductors, and the spontaneous formation of hexagonal patterns of some small polycyclic aromatic hydrocarbons (PAHs) on top of a graphitic surface. In order to attest our results, some experimental results from literature are compared to the obtained results.