ZnO nanorods as an intracellular sensor for pH measurements

ZnO nanorods with 80nm diameter and 700nm length and grown on the tip of a borosilicate glass capillary (0.7μm in diameter) were used to create a highly sensitive pH sensor for monitoring in vivo biological process within single cells. The ZnO nanorods, functionalized by proton H3O+ and hydroxyl OH− groups, exhibit a pH-dependent electrochemical potential difference versus a Ag∕AgCl microelectrode. The potential difference was linear over a large dynamic range (4–11), which could be understood in terms of the change in surface charge during protonation and deprotonation. These nanoelectrode devices have the ability to enable analytical measurements in single living cells and have the capability to sense individual chemical species in specific locations within a cell.