The focus of these research efforts is on the development and use of water-soluble semiconductor quantum dots (QDs) conjugated to biological functionalities to produce new and interesting capabilities. Disparate knowledge from materials synthesis, surface chemistry, and biology are integrated in working on these composite nanoassemblies. As an example, one application uses a biocompatible QD-dopamine nanoassembly to monitor the chemical state of dopamine changes from a protonated hydroquinone in acidic media to an oxidized quinone in basic environments (Figure 1). A series of carefully designed experiments allowed the researchers to establish that only the quinone form is capable of acting as an electron acceptor resulting in quenching of the QD emission.The rate of quinone formation and hence QD quenching is directly proportional to pH and can therefore be used to detect changes in the pH of solutions. Using this nanoscale sensor, the researchers were able to demonstrate pH sensing in solution and even visualize changes inside cells as cell cultures underwent drug-induced alkalosis (Figure 2).