title: Electrochemiluminescent pH sensor measured by the emission potential of TiO2 nanocrystals and its biosensing application.
abstract: This work reports for the first time a potential-based nano-electrochemiluminescent (ECL) pH sensor, using anatase TiO2 nanocrystals (NCs) as the ECL probe. The first ECL peak potential of the TiO2 NCs shifted negatively with increasing pH, showing a linear range from -0.47 V (vs Ag/AgCl) at pH 3 to -1.06 V at pH 10. This phenomenon was attributed to the absorption of 'potential-determining ions' of OH(-) on the surface of TiO2 NCs, leading to larger impedance of the electron injection. Other common 'potential-determining ions', such as phosphate, induced a slight potential shift of 0.03 V at a concentration of 0.1 M. Using urease as an enzyme model, a urea biosensor was developed by the simultaneous modification of urease and TiO2 NCs on indium-tin oxide (ITO) electrodes. The biosensor, measured on the basis of the pH increase caused by the enzyme catalysis reaction, had a linear range of 0.01-2.0 mM, with a potential shift of 0.175 V. The as-prepared pH sensor, which has simple construction procedures and acceptable sensitivity and selectivity, may provide new avenues for the construction of ECL bioanalytical methodologies.
authors.affiliation: Department of Clinical Laboratory, Second Affiliated Hospital of Southeast University, Nanjing, People's Republic of China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Liu
authors.forename: Nianyue
authors.initials: N
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Hui
authors.initials: H
authors.lastname: Jiang
mesh_terms: D015374:Biosensing Techniques; D055664:Electrochemical Techniques; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism; D014025:Titanium / Q000737:chemistry* / Q000378:metabolism; D014510:Urease / Q000032:analysis* / Q000378:metabolism
chemical_list: C009495:titanium dioxide; D014025:Titanium; D014510:Urease
keywords: TiO2 nanocrystals; bioanalysis; electrochemiluminescence (ECL); pH sensor; potential