Oxide materials are integral to many applications, such as supports for heterogeneous catalysis or as gate dielectrics in microelectronic devices.  Although the surface chemistry of many oxides has been studied extensively, there is evidence for the existence of low density defect sites that have not yet been characterized.  We have developed a method utilizing fluorescent probe molecules to chemically titrate various surface sites, enabling detection of low density defects on oxide materials.  We are studying the role these defect sites play in mediating  particle nucleation, with the goal of controlling nucleation by deliberately generating or passivating specific sites.