Abstract
Sensor design has used electron transfer (ET) increasingly over the past decade. Both chemically and biochemically based sensors (termed chemo-and biosensors) that employ ET as the sensing mode have drawn on decades of electron transfer research in chemistry [1], biology [2], and materials science [3]. This chapter focuses
on electron transfer reactions specifically with semiconductor nanoparticles, or quantum dots, that have been employed in biosensing. The primary material is CdSe coated with 2-4 monolayers of ZnS (so-called core-shell nanoparticles) [4, 5]. Due to the wide
excitation profile of quantum dots, electron transfer-based sensing methods are not constrained to the emission wavelengths provided
by CdSe [6]. As a result, fluorescence emission from 450 nm to
700 nm can be achieved depending on the diameter and material of
the water-soluble quantum dot employed. This provides a significant modularity to these systems in addition to their high photostability.