Preferred orientation of n -hexane crystallized in silicon nanochannels: A combined x-ray diffraction and sorption isotherm study.

We present an x-ray diffraction study on n -hexane in tubular silicon channels of approximately 10 nm diameter both as a function of the filling fraction f of the channels and as a function of temperature. Upon cooling, confined n -hexane crystallizes in a triclinic phase typical of the bulk crystalline state. However, the anisotropic spatial confinement leads to a preferred orientation of the confined crystallites, where the 001 crystallographic direction coincides with the long axis of the channels.

Crystallization of medium-length 1-alcohols in mesoporous silicon: an x-ray diffraction study.

The linear 1-alcohols n-C(16)H(33)OH, n-C(17)H(35)OH, n-C(19)H(39)OH have been imbibed and solidified in lined up, tubular mesopores of silicon with 10 and 15 nm mean diameters, respectively. X-ray diffraction measurements reveal a set of six discrete orientation states ("domains") characterized by a perpendicular alignment of the molecules with respect to the long axis of the pores and by a fourfold symmetry about this direction, which coincides with the crystalline symmetry of the Si host. A Bragg peak series characteristic of the formation of bilayers indicates a lamellar structure of the spatially confined alcohol crystals in 15 nm pores.