Generalized Coating Route to Silica and Titania Films with Orthogonally Tilted Cylindrical Nanopore Arrays

Abstract

We describe a simple, inexpensive coating method to produce thin silica and titania films with surfactant templated, orthogonally tilted cylindrical nanopore arrays. These films can be deposited onto any substrate because orientation of the 2D hexagonally close packed (HCP) mesophases out of the plane of the film is directed by a chemically neutral sacrificial copolymer layer. Orientation of the HCP mesophases through the entire thickness of films cured in open air is achieved by limiting the coating thickness. This generalizes the coating method by making it possible to deposit oriented films on substrates of any curvature and size. We find a critical thickness between 70 and 100 nm, below which the triblock copolymer surfactant-templated HCP phase aligns completely out of the plane of glass and silicon wafer substrates. Above this thickness, the effect of the chemically neutral bottom layer does not propagate across the entire film, and alignment of the HCP mesophases parallel to the (nonpolar) air interface produces a mixed orientation.

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

“…Other studies that showed the formation of vertically oriented cylindrical channels by transformation of a cubic phase and merging of the pores normal to the film also showed diffraction spots consistent with the cubic phase prior to thermal treatment [121][122][123]. However, the results obtained by Nagpure et al [82] are consistent with the hypothesis underlying the work of Koganti et al [110] that vertical channels simply form due to reorientation of the HCP phase in response to the modification of the surface of the substrate with a chemically neutral crosslinked P123 layer. A perfectly o-HCP structure follows a 2D growth mechanism with nucleation at the start of the process, whereas films with mixed pore orientation follow 2D growth with continuous nucleation.…”

“…By analogy with surface chemistry strategies used to orient block copolymer films [104][105][106][107][108][109], the Rankin group has reported the synthesis of mp-TiO 2 thin films with orthogonally tilted HCP (o-HCP) cylindrical nanopores using EISA with P123 as structure directing agent and titanium(IV) ethoxide as titania precursor [83,110]. The hypothesis underlying this approach is that orthogonal alignment of the HCP mesophase can be achieved in EISA-derived ceramic film by modifying the substrate surface so that it interacts equally with both blocks of the P123 template, making it chemically "neutral" towards the template surfactant.…”

Self-assembly of amphiphilic molecules: A review on the recent computer simulation results

“…Recent researches demonstrated that the vertically oriented pores can be induced by performing self-assembly of block copolymer and surfactant on chemically modified substrate. The strategy has been applied to the synthesis of surfactant-templated inorganic materials [65,66]. Rankin and his coworkers [65] in their experiments demonstrated that thin silica and titania films with orthogonally tilted cylindrical nanopore arrays can be produced on the substrates chemically modified by copolymer.…”

“…The strategy has been applied to the synthesis of surfactant-templated inorganic materials [65,66]. Rankin and his coworkers [65] in their experiments demonstrated that thin silica and titania films with orthogonally tilted cylindrical nanopore arrays can be produced on the substrates chemically modified by copolymer. To understand the orientational ordering on a molecular level induced by the chemically modified substrates, we study systemically the orientational ordering of the surfactant-templated inorganic nanomaterial on a ringpatterned surface [67].…”

Periodic Mesoporous Organosilica in Confined Environments

“…In thin films, the alignment of the pore system is usually parallel with respect to the substrate (see, however, recent reports on mesoporous silica films with other orientations). [11][12][13] Recently, the incorporation of mesostructured silica within the pores of anodic alumina membranes (AAM) has been reported. [14][15][16][17][18][19][20] These types of composite materials permit the synthesis of mesopores aligned perpendicular to the membrane surface.…”