Optical Biosensing Based on Metal Semiconductor Colloidal Nanocrystals

Nanomaterial-based optical sensors are among the most advanced class of sensing devices produced in the recent past for the continuous, real-time monitoring of diverse analytes. Following the tremendous impact of the unusual properties of nanoscale matter on present technology, scientific publications dealing with sensing applications have concomitantly proliferated. Research on these topics embraces wide and interdisciplinary fields under intense evolution, making it difficult to provide a comprehensive scenario of the current status of their development. This chapter is specifically intended to offer a critical view on the specific potential of colloidal nanocrystals as a distinguishable class of nanosized materials for biosensing. Especially, it will emphasize how the size-dependent optical properties of nanocrystals can be flexibly tailored by the synthetic tools accessible by modern material chemistry, specifically addressing optical techniques and methods for well-defined sensing purposes. The review of this subject will therefore be organized as follows: (a) the introduction will focus on the chemical-physical properties that justify the choice of nanocrystals as advantageous in various diagnostic approaches; (b) several optical techniques that can be used as transduction methods for biosensing will then be described in detail; (c) selected examples of specific applications and biochemical studies will be presented; and (d) in the conclusions, a few key issues regarding the commercial development of the presented techniques will be discussed.