212 ice | science Emerging Materials Research Volume 1 Issue EMR1 <Article Title> <Authors Sur Names> Emerging Materials Research 00 [Month] 20## Issue 00 Pages #–# http://dx.doi.org/10.1680/emr.11.000## Paper 1100## Received ##/##/20## Accepted ##/##/20## Published online ##/##/20## Keywords: <maximum 3 keywords> ICE Publishing: All rights reserved 1. Introduction Nowadays, the bottom-up approach is one the most effective way to produce nanomaterials. In this context, clay has been extensively utilized to give support to catalysts for their eficient recovery and to obtain various nanocomposites. These nanomaterials are multiphase with one or more phases organized in the nanometer regime and they can exhibit electronic, catalytic, mechanical, magnetic, and optical properties that are not present in individual parts. Several inorganic materials such as layered metal phosphates, metal oxides, zeolites, and mesoporous silica have been utilized for making various nanocomposites, but clays are the most important host, because of their signiicant ability to accommodate guest species. There are varieties of clays used as inert support for the recovery of enzymes, polymerization reactions, delivery of molecules, and remediation purposes. The montmorillonite (MMT) clay has been extensively employed in polymerization studies of aniline or its derivates with the aim to form nanocomposites with controlled structure. 1–4 Naturally occurring clay minerals offer a great potential, because of their speciic structure (layered and three-dimensional), in various technological applications based on the adsorptive and ionic exchange properties (Figure 1). Often they are used as supports (electro catalysis) or adsorbents and ionic exchangers (wastewater treatment) (Figure 2). The application of clay for catalysts in organic chemicals started from last century. Immense research has been conducted regarding the use of clay in organic syntheses. Clays have signiicant potential as host compounds for fancy catalysts such as shape selective and asymmetric reactions because of the characteristic layer structure and the facile intercalation properties. Additional advantage of using clay as support for catalysts is the composition of the clay. Clay is mainly made up of tetrahedral silicon dioxide and octahedral alumina and the ratio of the Si/Al is relatively steady, which is similar to molecular sieves. Recently, attention has shifted towards halloysite nanotubes (HNTs). Halloysite is typically a clay mineral and has a chemical composition of Al 4 Si 4 O 10 (OH) 8 . 4H 2 O. The nanotubular structure contributes towards the nanoscale dimensions of halloysites (Figure 3). It occurs mainly in two different polymorphs, the hydrated form and the dehydrated form. The hydrated form converts irreversibly into the dehydrated form when dried at temperatures Halloysite as support matrices: a review Deepak Rawtani* ME Assistant Professor (Bionanotechnology), Institute of Research & Development, Gujarat Forensic Sciences University, Gandhinagar, Gujarat, India Yadvendra K. Agrawal PhD Director, Institute of Research & Development, Gujarat Forensic Sciences University, Gandhinagar, Gujarat, India Developing new applications of natural resources is an interesting area of science. Clay minerals are very versatile materials and have attracted more attention due to their wide applications in various fields for more than a decade. Naturally occurring clay minerals offer a great potential, due to their specific structure (layered and three-dimensional), in several technological applications based on the adsorptive and ionic exchange properties. Halloysite nanotubes (HNTs) are naturally occurring clays with nanotubular structures. Various features such as nanoscale lumens, high length-to-diameter ratio, and low-hydroxyl-group density on the surface of halloysite make them an attractive alternative to other materials; simultaneously, their abundance and cheap cost enhance their utility. Applications of halloysite include various fields such as controlled drug release, nanotemplating, sorption, and fabrication of polymer nanocomposites. Recently, because of features like higher reactivity, higher cationic exchange, and tubular geometry, halloysite has been recognized as an attractive candidate to perform as a catalytic support for polymerization as well as immobilization reactions. The unique structure of HNT provides not only support to catalyst but it also enhances the performance of HNT-supported catalyst for various applications. Numerous studies suggest that halloysite and catalyst complex exhibit tremendous performance for the recovery of catalyst complex as well as for easy and safe administration of catalyst. In continuum, HNTs should be material of interest as a support for various structural and functional applications. ice | science Emerging Materials Research Volume 1 Issue EMR4 Halloysite as support matrices: a review Rawtani and Agrawal Pages 212–220 http://dx.doi.org/10.1680/emr.12.00005 Review Article Received 19/02/2012 Accepted 14/06/2012 Published online 28/06/2012 Keywords: biomimetic/catalyst/drug delivery/nanocomposites/ nanostructure ICE Publishing: All rights reserved *Corresponding author email address: rawtanid@gmail.com