Environmental Engineering Reference
In-Depth Information
level. The basis of the field is that bulk properties of materials made from nano
sized structures differ significantly from that of the original material. By alter-
ing the sizes of those building blocks, controlling their internal and surface
chemistries and controlling their assembly, new materials with new set of
properties can be designed. The different nanostructures currently being exten-
sively reviewed include nano particles (biodegradable, ceramic, magnetic, etc.),
nano wires and nano tubes, nano porous structures and self-assembled mono-
layer (SAMs).
Development and fabrication of nano devices for tailored end application
necessitates the surface modification of these nano structured functional
devices. These modification are carried out using traditional organic methodol-
ogies which are inherently non-environmentally friendly due to the use of toxic
catalysts, excessive solvents, multiple protection deprotection steps, harsh reac-
tion conditions and limited catalyst recyclability [1]. As the applications of
nanotechnology increases, there would be a growing need to develop environ-
mentally friendlier or green chemistry methodologies for functionalization and
modification of these nanostructures to create value added products. This
review aims to look into some of the surface modification reactions on SAMs,
the current technology available for such reactions and the limitation of the
available methodologies. This review also looks at emerging biocatalytic meth-
odologies and its potential as an alternative for carrying out these surface
modification reactions.
3.2 Review of Existing Literature and Technology
3.2.1 Introduction
Interfacial reactions are becoming an increasingly important subject for studies
with wide spread applications such as catalysis [2], electronics [3], chemical
sensing [4, 5], and many other applications [6, 7]. Interfacial phenomena dom-
inate the performance of micro and nano devices which are currently being
extensively studied. Furthermore, because of the extremely high area to volume
ratio, interfacial interactions become the dominant factor for determining
device performance. The interface layer can be as simple as a plain polymer or
complex as a multiple layer of chemicals and biological components. Under-
standing the rules that govern these surface reactions provides important
information for fundamental studies in chemistry and biochemistry [8, 9].
Also the availability of numerous analytical techniques capable of detecting
chemical changes in films that are few nanometers thick [10], have made studies
of interfacial and surface reactions a viable and important area of modern
science.
Self-assembly provides a simple route to organize suitable organic molecules
on noble metal and selected nano cluster surfaces by using monolayers of long
