SEMICONDUCTOR MATERIALS FOR THE DEVELOPMENT OF CHEMICAL SENSORS 283 Fluorescence emission Wavelength (nm) QDs ions ligand Figure 5.11. Schematic diagram of QDs for ion-sensing applications. and Patel 2001). This type of sensing system for ions in physiological buffer samples for metal ions was first demonstrated by Chen and Rosenzweig (2002). Similar systems have been introduced for the detection of Zn 2+ , Cu 2+ , and Hg 2+ (Bo and Ping 2005; Chen et al. 2006; Li et al. 2008; Koneswaran