Engineering the Spatial Selectivity of Surfaces at the Nanoscale Using Particle Lithography Combined with Vapor Deposition of Organosilanes

Abstract

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.

Influence of Solvent on Octadecyltrichlorosilane Nanostructures Fabricated Using Particle Lithography

“…5,45 In addition, the nanopores follow a hexagonal symmetry with a periodicity of 511 ± 17 nm that closely matches the dimensions of the 500 nm silica mesosphere template; the OTS surface coverage (97.9 ± 0.1%) and nanopore surface density (3.7 ± 0.2 features per μm 2 ) are also consistent with previous studies. 10,32,33,52 The long-range order of the nanopores is illustrated in Figure 2A by the minimal number of defects, such as missing or irregularly shaped nanopores and line defects. Although the nanopore depth (1.3 ± 0.2 nm) is less than expected for a densely packed OTS SAM (2.2−2.8 nm), 46,50 The Journal of Physical Chemistry C Article it is consistent with previous studies that employed silica mesospheres using similar deposition conditions.…”

“…Further, changes in periodicity, density, and feature size can be modulated by changes in the diameter of the mesospheres used for both solution-and vapor-phase deposition of organosilane nanopatterns. 31,32,51,52 In this report, we investigate the influence of anhydrous toluene and bicyclohexyl on the solution-phase formation of nanopores…”

Size and Shape Control of Gold Nanodeposits in an Array of Silica Nanowells on a Gold Electrode

“…Providing there are no defects (pin holes) in the insulating silica surrounding the nanowells, the electrochemistry only takes place in the nanowell, thus restricting growth to this area [8]. The advantages of growing arrays of nanoparticles within a porous inorganic network using this approach are the following: (a) the interparticle spacing between nanoparticles can be controlled by the size of the template used to form the nanowell, (b) the size and shape of the resultant nanoparticles/nanostructures can be controlled by the size and shape of the nanowell, and (c) the silica support helps prevent aggregation of the nanoparticles as they begin to grow larger [8,10,11]. From an electroanalytical point of view, enlarging the conductive domains located at the bottom of the nanowell also provides a means to potentially increase the sensitivity of the microelectrode array [12].…”

“…To form the gold nanoparticle array, the exposed surface (hydroxides) was immersed in a solution of tin ions, followed by silver ions, and then gold ions [11]. In another paper, shallow nanowells were formed on a silicon wafer via the vapor deposition of chlorosilanes around the latex sphere [10,16,17]. The hydroxylated surface located at the bottom of the nanowells was then functionalized with mercaptopropyltrimethoxysilane and subsequently used to bind gold nanoparticles [10].…”

“…In another paper, shallow nanowells were formed on a silicon wafer via the vapor deposition of chlorosilanes around the latex sphere [10,16,17]. The hydroxylated surface located at the bottom of the nanowells was then functionalized with mercaptopropyltrimethoxysilane and subsequently used to bind gold nanoparticles [10]. In contrast to these papers, the current method is a one-step method that does not require multiple reaction steps or chemical modification.…”