Functionalization of diameter-sorted semiconductive SWCNTs with photosensitizing porphyrins: syntheses and photoinduced electron transfer.
Covalent functionalization of diameter sorted SWCNTs with porphyrins (MP), and photochemistry to establish nanotube diameter-dependent charge separation efficiencies are reported. The MP-SWCNT(n,m) [M=2H or Zn, and (n,m)=(7,6) or (6,5)] nanohybrids are characterized by a variety of spectroscopic, thermogravimetric, TEM imaging techniques, and also by DFT MO calculations. The thermogravimetric, Raman and fluorescence studies reveal the presence of a moderate number of porphyrins on the SWCNT surface. The MO results suggest charge separation (CS) via the excited state of MP. Time-resolved fluorescence studies reveal quenching of the singlet excited state of the MP with SWCNT(n,m), giving the rate constants of charge separation (k(CS)) in the range of (4-5)×10(9) s(-1). Nanosecond transient absorption measurements confirm the charge-separated radical cation and the radical anion as [MP(.+)-SWCNT(.-)] with their characteristic absorption bands in the visible and near-IR regions. The charge separated states persist for about 70-100 ns thus giving an opportunity to utilize them to build photoelectrochemical cells, which allowed us to derive the structure-reactivity relationship between the nature of porphyrin and diameter of the employed nanotubes.
Department of Chemistry, University of North Texas, 1155 Union Circle, 305070, Denton, TX 76203-5017, USA.
Sushanta K
SK
Das
Atula S D
AS
Sandanayaka
Navaneetha K
NK
Subbaiyan
Melvin E
ME
Zandler
Osamu
O
Ito
Francis
F
D'Souza
D004579:Electron Transport; D006859:Hydrogen / Q000737:chemistry; D008665:Metalloporphyrins / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D037742:Nanotubes, Carbon / Q000737:chemistry*; D055668:Photochemical Processes; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D012666:Semiconductors; D015032:Zinc / Q000737:chemistry
D008665:Metalloporphyrins; D037742:Nanotubes, Carbon; D011166:Porphyrins; D006859:Hydrogen; D015032:Zinc