Mesoporous Structures Confined in Anodic Alumina Membranes

Abstract

The synthesis of nanoporous membranes based on different concepts and materials is a field of active research. This review focuses on the synthesis strategies, mesophase evolution mechanisms and potential applications of mesoporous materials confined within anodic alumina membranes (AAM). Following a rapid evolution of synthetic techniques, a significant number of different mesoporous materials (e.g., silica, titania, and carbon) with highly regular structures can now be prepared within these membranes. In recent years, efforts have also been made to understand the formation mechanisms of these hierarchical mesophases. The resulting organized nanoporous membranes open up a wide range of potential applications in fields such as templating oriented nanowires and controlled separation and release of molecules. For example, while various synthesis strategies can be used for the preparation of membrane-embedded nanowires, the latter can also be obtained as isolated objects after dissolution of the alumina host matrix. The review also discusses issues such as control of structural defects or integrity of interfaces that should be addressed in future research in order to fully exploit the potential of these hierarchical mesoporous channel structures.

Modification of Mesoporous Silicates for Immobilization of Enzymes

“…Direct functionalization involves the co-condensation of siloxane and organosilane precursors to produce a material containing a homogenous dispersion of functional groups which protrude into the pore while also enabling access to the surface silanol groups for adsorption [7][8][9]. An example of this method of functionalization is the preparation of cyano modified MPS (CNS) [17].…”

“…As the synthesis and characterisation of MPS materials has been extensively reviewed [7][8][9], the focus of this review will be on the use of functionalized MPS for immobilization of enzymes. Functionalised MPS can be prepared directly, post-synthesis and by the addition of bridged silesquioxanes as the source of silica.…”

“…Functionalised MPS can be prepared directly, post-synthesis and by the addition of bridged silesquioxanes as the source of silica. MPS modified with functional groups such as thiol, amine, chloro, carboxylic acid, N-(trimethoxysilylpropyl)ethylene diamine triacetic acid (EDTA), oxirane rings, cyano, alkane and aromatic functional groups together with a range of metal ions have been prepared [8][9][10][11][12][13][14][15][16][17].…”

“…Post-synthesis functionalization involves direct grafting of a suitable functional group onto the surface of MPS and has been used to graft chloro, alkoxy, and silyl and amine groups [8][9][10][11][12][13][14][15] onto the exposed surfaces of the mesoporous channels and external surface. The advantages of post-synthesis functionalization include the fact that no alteration of the structural ordering of the starting mesoporous material occurs and that functionalization occurs only on the surface.…”

Formation of hexagonal and cubic fluorescent periodic mesoporous organosilicas in the channels of anodic alumina membranes

“…Moreover, an alternative strategy uses connement in anisotropic hosts such as porous anodic alumina membranes (AAMs). 27 The resulting mesoporous composites were reported to be able to offer high mechanical and thermal stability due to the support of the alumina host. Furthermore, the connement effects can lead to enhanced control over the resulting mesophase morphologies, with the possibility to realize large single-phase domains and high aspect ratios of mesoporous systems.…”