title: pH-responsive, TiO2-attached porphyrin for singlet oxygen production in an aqueous solution.
abstract: A pH-responsive, TiO2-attached sensitizer was prepared based on the adsorption of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) onto TiO2 nanoparticles. This colloidally dispersed TiO2-attached TCPP behaves as a single-phase colloidal sensitizer at pH 1.0-3.3 with quantum yields of singlet oxygen production (Phi(Delta)) between 0.20 and 0.25, as a heterogeneous particle sensitizer at pH 3.5-6.0 with Phi(Delta) between 0.25 and 0.50, and as homogeneous free TCPP molecules in alkaline solutions with Phi(Delta) = 0.53. The changes in Phi(Delta) are fully consistent with pH-dependent adsorption of TCPP onto the TiO2 surface. Recovery yields of 99.8% for TCPP and 98.8% for TiO2 were obtained from 1.4 mM TiO2-attached TCPP. We attribute its photosensitization ability to retaining TCPP solubility on the TiO2 surface and, hence, activity. This novel system shows a potential to bridge the gap between easily recoverable and highly efficient sensitizers.
authors.affiliation: Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, USA.
authors.forename: Wenbing
authors.initials: W
authors.lastname: Li
authors.forename: Naveen
authors.initials: N
authors.lastname: Gandra
authors.forename: Erick D
authors.initials: ED
authors.lastname: Ellis
authors.forename: Shavelle
authors.initials: S
authors.lastname: Courtney
authors.forename: Shufang
authors.initials: S
authors.lastname: Li
authors.forename: Ebonie
authors.initials: E
authors.lastname: Butler
authors.forename: Ruomei
authors.initials: R
authors.lastname: Gao
mesh_terms: D000327:Adsorption; D002138:Calibration; D003102:Colloids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D010777:Photochemistry / Q000379:methods; D017319:Photosensitizing Agents / Q000494:pharmacology; D011166:Porphyrins / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D003102:Colloids; D017319:Photosensitizing Agents; D011166:Porphyrins; D014867:Water; C018395:tetracarboxyphenylporphine; C009495:titanium dioxide; D014025:Titanium; D010100:Oxygen