title: Online detection of reactive oxygen species in ultraviolet (UV)-Irradiated nano-TiO2 suspensions by continuous flow chemiluminescence.
abstract: Reactive oxygen species (ROS) play very important roles in the photocatalytic reactions of semiconductors. Using a continuous flow chemiluminescence (CFCL) system, we developed three methods for the selective, sensitive, and online detection of O2(• -), •OH, and H2O2 generated during ultraviolet (UV) irradiation of nano-TiO2 suspensions. TiO2 nanoparticles were irradiated in a photoreactor and pumped continuously into a detection cell. To detect O2(• -), luminol was mixed with TiO2 before it entered the detection cell. For the detection of short-lived •OH, phthalhydrazide was added into the photoreactor to capture •OH, and then mixed with H2O2/K5Cu(HIO6)2 to produce chemiluminescence (CL). To detect H2O2, an irradiated TiO2 suspension was kept in darkness for 30 min, and then mixed with luminol/K3Fe(CN)6 to produce CL. The selectivity of each method for a particular ROS was verified by using specific ROS scavengers. For a given ROS, a comparison between CL and conventional method showed good agreement for a series of TiO2 concentrations. The sensitivity of CL method was approximately 3-, 1200-, and 5-fold higher than the conventional method for O2(• -), •OH, and H2O2, respectively. To demonstrate the utility of the methods, ROS in three different types of TiO2 suspensions was detected by CFCL. It was found that photodegradation efficiency of Rhodamine B correlated the best (R(2) > 0.95) with the amount of photogenerated •OH, implying that •OH was the major oxidant in Rhodamine B photodegradation reaction. CFCL may provide a convenient tool for the studies on the reaction kinetics of ROS-participated decomposition of environmental contaminants.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, 18 Shuangqing Road, Beijing 100085, China.
authors.forename: Dabin
authors.initials: D
authors.lastname: Wang
authors.forename: Lixia
authors.initials: L
authors.lastname: Zhao
authors.forename: Liang-Hong
authors.initials: LH
authors.lastname: Guo
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
mesh_terms: D002384:Catalysis; D004867:Equipment Design; D006861:Hydrogen Peroxide / Q000032:analysis*; D017665:Hydroxyl Radical / Q000032:analysis*; D008163:Luminescent Measurements / Q000295:instrumentation*; D010782:Photolysis; D017382:Reactive Oxygen Species / Q000032:analysis; D012235:Rhodamines / Q000737:chemistry; D026082:Singlet Oxygen / Q000032:analysis*; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D017382:Reactive Oxygen Species; D012235:Rhodamines; C009495:titanium dioxide; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D014025:Titanium