A new method of particle lithography is described for preparing rings or nanoporous films of organosilanes. Millions of exquisitely uniform and precisely spaced nanostructures with designed surface chemistry can be rapidly produced using vapor deposition through mesoparticle masks. Nanoscopic amounts of water are essential for initiating surface hydrosilation. Thus, the key step for preparing covalently bonded nanostructures of organosilanes is to control drying parameters to spatially direct the placement of water on surfaces.

Particle lithography is a practical approach to generate millions of organosilane nanostructures on various surfaces, without the need for vacuum environments or expensive instrumentation. This report describes a stepwise chemistry route to prepare organosilane nanostructures and then apply the patterns as a spatially selective foundation to attach gold nanoparticles. Sites with thiol terminal groups were sufficiently small to localize the attachment of clusters of 2-5 nanoparticles. Basic steps such as centrifuging, drying, heating, and rinsing were used to generate arrays of regular nanopatterns. Close-packed films of monodisperse latex spheres can be used as an evaporative mask to spatially direct the placement of nanoscopic amounts of water on surfaces. Vapor phase organosilanes deposit selectively at areas of the surface containing water residues to generate nanostructures with regular thickness, geometry, and periodicity as revealed in atomic force microscopy images. The area of contact underneath the mesospheres is effectively masked for later synthetic steps, providing exquisite control of surface coverage and local chemistry. By judicious selection in designing the terminal groups of organosilanes, surface sites can be engineered at the nanoscale for building more complex structures. The density of the nanopatterns and surface coverage scale predictably with the diameter of the mesoparticle masks. The examples presented definitively illustrate the capabilities of using the chemistry of molecularly thin films of organosilanes to spatially define the selectivity of surfaces at very small size scales.

Arrays of protein nanostructures can be formed on surfaces such as mica(0001) and Au(111) using lithography with polystyrene latex particles. To create arrays of protein nanostructures, monodisperse latex spheres are mixed with the desired protein (e.g. BSA, protein A or IgG) and deposited onto substrates. Protein-coated nanospheres self-assemble into organized crystalline layers when dried on flat surfaces. After rinsing with water, dried latex spheres are displaced to expose periodic arrays of uncovered circular cavities. The immobilized proteins remain attached to the surface and form nanopatterns over broad areas (microns) corresponding to the thickness of a single layer of proteins. The nanostructures of immobilized proteins maintain the order and periodicity of the latex scaffold. The morphology and diameter of the protein nanostructures are tuneable by selecting the ratios of protein-to-latex and the diameters of latex spheres. Well-defined nanostructured surfaces of proteins supply a tool for fundamental investigations of protein binding interactions in biological systems at the nanoscale and have potential applications in biochip and biosensing systems.

A recent finding reports that co-stimulation of the high-affinity immunoglobulin E (IgE) receptor (FcεRI) and the chemokine receptor 1 (CCR1) triggered formation of membrane nanotubes among bone-marrow-derived mast cells. The co-stimulation was attained using corresponding ligands: IgE binding antigen and macrophage inflammatory protein 1α (MIP1 α), respectively. However, this approach failed to trigger formation of nanotubes among rat basophilic leukemia (RBL) cells due to the lack of CCR1 on the cell surface (Int. Immunol. 2010, 22 (2), 113–128). RBL cells are frequently used as a model for mast cells and are best known for antibody-mediated activation via FcεRI. This work reports the successful formation of membrane nanotubes among RBLs using only one stimulus, a hapten of 2,4-dinitrophenyl (DNP) molecules, which are presented as nanostructures with our designed spatial arrangements. This observation underlines the significance of the local presentation of ligands in the context of impacting the cellular signaling cascades. In the case of RBL, certain DNP nanostructures suppress antigen-induced degranulation and facilitate the rearrangement of the cytoskeleton to form nanotubes. These results demonstrate an important scientific concept; engineered nanostructures enable cellular signaling cascades, where current technologies encounter great difficulties. More importantly, nanotechnology offers a new platform to selectively activate and/or inhibit desired cellular signaling cascades.

There is an emerging need for practical methods that can produce organized arrays of nanomaterials with high throughput. Particle lithography provides such an approach for rapidly preparing millions of exquisitely uniform nanometer-sized structures on flat surfaces, using basic steps of bench chemistry. Structural templates of monodisperse latex or silica mesospheres can guide the deposition of nanoparticles to generate 2D arrays of nanopatterns with control of the surface coverage, size, and periodicity of nanoparticle structures.