title: Effect of photocurrent enhancement in porphyrin-graphene covalent hybrids.
abstract: Graphene oxide (GO) sheets were covalently functionalized with 5-p-aminophenyl-10,15,20-triphenylporphyrin (NH2TPP) by an amidation reaction between the amino group in NH2TPP and carboxyl groups in GO. The Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning and transmission electron microscopies reveal that NH2TPP covalent bonds form on the double surface of graphene oxide sheets, generating a unique nano-framework, i.e., NH2TPP-graphene-NH2TPP. Its UV-visible spectroscopy reveals that the absorption spectrum is not a linear superposition of the spectra of NH2TPP and graphene oxide, because a 59nm red shift of the strong graphene oxide absorption is observed from 238 to 297nm, with significant spectral broadening between 300 and 700nm. Fluorescence emission spectroscopy indicates efficient quenching of NH2TPP photoluminescence in this hybrid material, suggesting that photo-induced electron transfer occurs at the interface between NH2TPP and GO. A reversible on/off photo-current density of 47mA/cm(2) is observed when NH2TPP-graphene-NH2TPP hybrid sandwiches are subjected to pulsed white-light illumination. Covalently-bound porphyrins decrease the optical HOMO/LUMO band gap of graphene oxide by ≈1eV, according to UV-visible spectroscopy. Cyclic voltammetry predicts a small HOMO/LUMO band gap of 0.84eV for NH2TPP-graphene-NH2TPP hybrid sandwiches, which is consistent with efficient electron transfer and fluorescence quenching.
authors.affiliation: Institute of Hybrid Materials-the Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071, PR China. Electronic address: jianguotangde@hotmail.com.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Tang
authors.forename: Lin
authors.initials: L
authors.lastname: Niu
authors.forename: Jixian
authors.initials: J
authors.lastname: Liu
authors.forename: Yao
authors.initials: Y
authors.lastname: Wang
authors.forename: Zhen
authors.initials: Z
authors.lastname: Huang
authors.forename: Shiqiang
authors.initials: S
authors.lastname: Xie
authors.forename: Linjun
authors.initials: L
authors.lastname: Huang
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Xu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Belfiore
mesh_terms: D004560:Electricity; D055664:Electrochemical Techniques; D006108:Graphite / Q000737:chemistry*; D008027:Light; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction; D011166:Porphyrins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D011166:Porphyrins; D006108:Graphite
keywords: Graphene; Hybrid; Photocurrent; Porphyrin