title: Reversible chemical tuning of charge carriers for enhanced photoelectrochemical conversion and probing of living cells.
abstract: A facile, solution method for reversible tuning of oxygen vacancies inside TiO2 nanowires, in which the reducing treatment of TiO2 by NaBH4 leads to 2.4-fold increase of photocurrent density, compared to pristine TiO2 nanowires, is reported. Subsequent oxidizing treatment using KMnO4 or annealing in air can reset the photocurrent density to the original values. The incident photo-to-current conversion efficiency measurement exhibits that the reduced TiO2 nanowires present both enhanced photoactivity in both UV and visible regions. Density functional theory calculations reveal that the oxygen vacancies in the reduced TiO2 cause defect states in the band structure and result in enhanced carrier density and conductivity. In addition, the enhanced solar energy-driven photoelectrochemical conversion allows real-time, sensitive chemical probing of living cells that are directly grown on the TiO2 nanowire photoanodes. As proofs-of-concept, after functionalized with horseradish peroxidase (HRP) on the surface, the reduced TiO2 NWs demonstrate sensitive, real-time monitoring of the H2O2 levels in several distinctive living cell lines, with the lowest detectable H2O2 concentration of 7.7 nM. This reversible tuning of oxygen vacancies suggests a facile means for transition metal oxides, with enhanced photoconversion activity and electrochemical sensitivity.
authors.affiliation: Laboratory of Advanced Materials, Department of Chemistry, Fudan University, Shanghai, 200433, China.
authors.forename: Yongcheng
authors.initials: Y
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Tang
authors.forename: Tong
authors.initials: T
authors.lastname: Zhou
authors.forename: Peimei
authors.initials: P
authors.lastname: Da
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Biao
authors.initials: B
authors.lastname: Kong
authors.forename: Zhongqin
authors.initials: Z
authors.lastname: Yang
authors.forename: Gengfeng
authors.initials: G
authors.lastname: Zheng
mesh_terms: D000818:Animals; D015374:Biosensing Techniques; D002467:Cell Nucleus / Q000378:metabolism; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D005456:Fluorescent Dyes / Q000737:chemistry; D057809:HEK293 Cells; D006735:Horseradish Peroxidase / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D008027:Light; D061986:MCF-7 Cells; D008264:Macrophages; D053768:Metal Nanoparticles / Q000737:chemistry; D051379:Mice; D053770:Nanowires / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D010316:Particle Size; D010777:Photochemistry / Q000379:methods*; D011196:Potassium Permanganate / Q000737:chemistry*; D012666:Semiconductors; D012993:Solar Energy; D014025:Titanium / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D005456:Fluorescent Dyes; D011196:Potassium Permanganate; C009495:titanium dioxide; D006861:Hydrogen Peroxide; D014025:Titanium; D006735:Horseradish Peroxidase; D010100:Oxygen
keywords: H2O2 sensing; carrier density; chemical tuning; living cells; metal oxides