Environmental Engineering Reference
In-Depth Information
CHAPTER 13
Nanosensors
Farhan Ahmad and Syed A. Hashsham
13.1 Introduction
Advances in nanotechnology are opening new horizons for the development of
sensors with micron or sub-micron size features suitable for detection of biological
molecules. Based on their dimensions, often micro or nano is added to the term sensor to
illustrate the scale. The focus of this chapter is on micro- and nano-scale sensors suitable
for detecting waterborne pathogens. Development of sensors (both micro and nanoscale)
for the water industry have experienced considerable growth during the last two decades
(Lim et al., 2005). However, studies focusing on the use of common nanoscale materials
e.g., carbon nanotubes and quantum dots for the purpose of detecting waterborne
pathogens are still limited. Progress in the area of nanosensors is heavily dependent on
the development of novel nanoscale materials (Vaseashta and Dimova-Malinovska,
2005). Nano-scale materials exhibit extraordinary electrical, optical, and mechanical
properties compared to their bulk counterpart. Sensors employing these materials can
specifically interact with microorganisms (bacteria, viruses, and protozoa), proteins,
nucleic acids, antibodies, and of course many chemical species to produce a signal. The
signals are then converted to a measurable response (e.g., current, potential, or light
intensity), which can be further amplified, processed, or stored for analysis. A number of
signal transduction techniques ranging from electrical/electrochemical, optical, and
mechanical are available. Nano-scale sensors have many advantages including: i) high
sensitivity due to comparable size of sensor element (nm to μm) and analyte/target
species (0.2 to 2 μm) and high surface area to volume ratio, ii) low cost of materials and
the reagents, iii) shorter assay time, iv) portability and use as point-of-use or point-of-
care devices (Erickson et al., 2008).
Diseases from waterborne pathogens pose a major challenge in both developed
and developing countries. Economical and robust sensors could play a major role in
providing safe water by directly measuring the waterborne pathogens. Nearly 4,000
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