Composite mesostructures by nano-confinement

Abstract

In a physically confined environment, interfacial interactions, symmetry breaking, structural frustration and confinement-induced entropy loss can play dominant roles in determining molecular organization. Here we present a systematic study of the confined assembly of silica-surfactant composite mesostructures within cylindrical nanochannels of varying diameters. Using exactly the same precursors and reaction conditions that form the two-dimensional hexagonal SBA-15 mesostructured thin film, unprecedented silica mesostructures with chiral mesopores such as single- and double-helical geometries spontaneously form inside individual alumina nanochannels. On tightening the degree of confinement, a transition is observed in the mesopore morphology from a coiled cylindrical to a spherical cage-like geometry. Self-consistent field calculations carried out to account for the observed mesostructures accord well with experiment. The mesostructures produced by confined syntheses are useful as templates for fabricating highly ordered mesostructured nanowires and nanowire arrays.

Ordered Arrays of Mesoporous Microrods from Recyclable Macroporous Silicon Templates

“…Subsequently, the templates were heated at 85 °C for 2 h and at 130 °C for 3 h, respectively, in the presence of 0.05 mL of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (97%, ABCR GmbH). Mesoporous SBA-15 precursor solutions were prepared according to protocols reported in the literature [2,9,10]. A typical procedure involves mixing TEOS (99+ %, Alfa Aesar), EO 20 PO 70 EO 20 (BASF, weight-average molecular weight Mw = 5800 g mol-1, Pluronic P123), 1.0 M HCl(aq) and ethanol as described elsewhere [9,10].…”

“…Mesoporous SBA-15 precursor solutions were prepared according to protocols reported in the literature [2,9,10]. A typical procedure involves mixing TEOS (99+ %, Alfa Aesar), EO 20 PO 70 EO 20 (BASF, weight-average molecular weight Mw = 5800 g mol-1, Pluronic P123), 1.0 M HCl(aq) and ethanol as described elsewhere [9,10]. The macroporous Si templates were immersed in the precursor solution, and gelated at room temperature for 48 h and then at 60 °C for 24 h. Finally, the samples were calcinated at 550 °C for 6 h. SEM investigations were performed using a JEOL JSM 6300 operated at an accelerating voltage of 5 kV.…”

“…[1][2][3][4][5] However, their integration into device architectures still remains a challenge. Recent efforts have focused on the synthesis of MCM (Mobil Crystalline Material) [6,7] and SBA (Santa Barbara amorphous) type [6,[8][9][10][11][12][13]] materials inside porous supports characterized by straight, aligned pores oriented normal to the surface. For this purpose, porous alumina matrices, either ordered [14] or disordered, [15] have predominantly been employed.…”

“…Subsequently, 1H,1H,2H,2H-perfluorodecyltrichlorosilane is grafted onto the pore walls by adapting protocols reported elsewhere [22] to render them into low-energy surfaces. [23] Mesoporous SBA-15 precursors are prepared following the procedures described in the literature, [5,9,10] 20 by calcination at 550 °C for 6 h, mesoporous silica microrods connected to a silica film on the surface of the template are obtained inside the macroporous Si.…”

Template electrosynthesis of tailored-made helical nanoswimmers

“…Several groups have demonstrated recently the successful template fabrication and assembly of helical composite mesostructures. 31,32 In particular, Park's group described the synthesis of palladium (Pd) nanosprings using anodized aluminum oxide (AAO) templates and electrochemical deposition. 32 Taking advantage of these recent advances in the electrosynthesis of nanosprings, we demonstrate in the following sections that this templating route can lead to the large-scale low-cost preparation of remarkably small magnetically driven helical nanoswimmers (down to 100 nm in diameter and 600 nm in length) that display efficient propulsion behavior.…”