Synthesis, Characterization, Redox Properties, and Photodynamics of Donor–Acceptor Nanohybrids Composed of Size-Controlled Cup-Shaped Nanocarbons and Porphyrins
✍ Scribed by Masataka Ohtani; Kenji Saito; Shunichi Fukuzumi
- Book ID
- 102796257
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 522 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
Cup‐shaped nanocarbons (CNC) generated by the electron‐transfer reduction of cup‐stacked carbon nanotubes have been functionalized with porphyrins (H~2~P) as light‐capturing chromophores. The resulting donor–acceptor nanohybrid has been characterized by thermogravimetric analysis (TGA), Raman and IR spectroscopy, transmission electron microscopy, elemental analysis, and UV/Vis spectroscopy. The weight of the porphyrins attached to the cup‐shaped nanocarbons was determined as 20 % by TGA and elemental analysis. The UV/Vis absorption spectrum of CNC(H~2~P)~n~ in DMF agrees well with that obtained by the superposition of reference porphyrin (ref‐H~2~P) and cup‐shaped nanocarbons. The photoexcitation of the CNC(H~2~P)~n~ nanohybrid results in formation of the charge‐separated (CS) state to attain the longest CS lifetime (0.64±0.01 ms) ever reported for donor–acceptor nanohybrids, which may arise from efficient electron migration following the charge separation. The formation of a radical ion pair was detected directly by electron spin resonance (ESR) measurements under photoirradiation of CNC(H~2~P)~n~ with a high‐pressure mercury lamp in frozen DMF at 153 K. The observed ESR signal at g=2.0044 agrees with that of ref‐H~2~P^.+^ produced by one‐electron oxidation with [Ru(bpy)~3~]^3+^ in deaerated CHCl~3~, indicating the formation of H~2~P^.+^. The electron‐acceptor ability of the reference CNC compound (ref‐CNC) was also examined by the electron‐transfer reduction of ref‐CNC by a series of semiquinone radical anions.