Sensors - Hierarchical Nanostructures for Energy Devices - page 244

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CHAPTER 11
Sensors

DONGJIN LEE

School of Mechanical Engineering, Konkuk University, Korea
Email: [e-mail]

11.1 Introduction
Sensors are analytical devices that quantify physical or chemical infor-
mation. Recently, there has been an increasing demand for high perform-
ance sensors with high sensitivity, high resolution, short response/recovery
time, long lifetime, multiplexity, disposability, etc. Nanomaterial-based
sensors have been of great interest due to their high performance over the
past two decades. This high performance is attributed to a high surface-to-
volume ratio, size similarity to target macromolecules 1 and novel detection
mechanisms. 2-4
Among these, the high surface-to-volume ratio enhances the interaction
between a sample analyte and the sensor's surface. However, it is not a good
strategy to keep decreasing the size of nanomaterials since van der Waals
forces become dominant at the nanoscale leading to aggregation of nano-
materials. Then, the free surface is screened by neighboring individual
elements and the diffusion of target molecules into the inner part of ag-
gregates is suppressed. 5 Therefore, the target molecule can interact only with
the outer surface of aggregates and the change in material properties is
limited on the outer surface, which makes it dicult to observe. The effect of
such behavior in aggregates is to decrease the sensitivity and/or resolution of
nanomaterial-based sensors. Moreover, the restrained diffusion of the target
molecule yields a sluggish response/recovery.

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