Chapter 4
Zinc Oxide Nanostructures: Advances and Applications
Edited by Magnus Willander
Copyright © 2014 Pan Stanford Publishing Pte. Ltd.
ISBN
978-981-4411-33-2 (Hardcover), 978-981-4411-34-9 (eBook)
www.panstanford.com
Nanobiology and Nanomedical Devices
Using Zinc Oxide Nanostructures
In general, nanostructures with relatively small sizes constitute
excellent signal transduction elements when dealing with biological
analytes or chemical species. The reason for this is the similarity of
the order of size between nanostructures and biological analytes
and chemical species. The consequence of this issue is the fact
that nanostructures will possess relatively very high sensitivity for
detection of the biological analytes and chemical species compared
to conventional large bulk sensors. In addition, sensors based on
nanostructures can operate eficiently when the detection is for
situations where the available sample volume is small and the
concentration of the element of analyte in question is low. This is
in fact a very important advantage of nanostructure-based sensors.
Among the various known nanostructures, nanowires (NWs) and
nanorods (NRs), with their relatively high-surface-area-to-volume
ratio, constitute excellent signal transduction elements and have
other advantages due to their geometrical features. On the other hand,
Magnus Willander and Omer Nur
Department of Science and Technology, Campus Norrköping,
Linköping University, SE-601 74 Norrköping, Sweden
magwi@itn.liu.se
128
Nanobiology and Nanomedical Devices Using Zinc Oxide Nanostructures
zinc oxide (ZnO), being biosafe and biocompatible, is an attractive
material for implementation as an active sensor element. Moreover,
among the different sensor procedures, the potentiometric-
based procedure is one of the most attractive procedures for bio-
environments due to the fact that it is based on measuring charge
accumulation with no current passing through the media.
4.1 Introduction
Zinc oxide (ZnO) is a direct-wide-bandgap semiconductor belonging
to group II–VI and has received attention in the past few years
for its potential for many applications in the area of photonics,
piezoelectricity, and sensing [1]. Zinc oxide possesses excellent
properties for optical application due to its relatively high exciton
binding energy (60 meV), its wide direct bandgap (3.34 eV), and
the many deep levels that emit covering the whole visible range.
These excellent optical properties imply a potential for laser and
light emitting diodes [2]. Zinc oxide has also been of interest for
ield emission devices [3]. In addition, ZnO is characterized by high
electromechanical coupling, which has been utilized to demonstrate
generation of electrical energy from mechanical movements [4].
Also, ZnO is a biosafe and biocompatible material [5]. In its
unintentional doping, zinc oxide grows as an n-type material with
many shallow donor levels [6]. Although ZnO is known to researchers
since the 1930s [7], the interest in ZnO has been luctuating despite
many excellent properties of this material. The main reason for this
was mainly the lack of stable reproducible p-type doping that can
be reproduced in different laboratories. Researchers have attempted
to utilize the excellent properties of ZnO by combing its thin ilms
in heterojunctions with other p-type. Nevertheless, due to lattice
mismatch, high-performance device quality heterojunctions were
not demonstrated. For the past few years, the interest in ZnO has
intensiied in many laboratories worldwide performing research
on ZnO growth and devices. This intensiied research concerns ZnO
nanostructures mainly for many reasons. Among these reasons are
the small footprint of nanostructures implying no need for lattice
mismatch and also due to the self-organized growth property of
ZnO, which implies that ZnO nanostructures can be grown on any
substrate that is amorphous or crystalline in nature [2]. In addition,
the possibility of low-temperature chemical growth of these

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