Department of Chemistry, University of North Texas, 1155 Union Circle, #305070, Denton, TX 76203-5017, USA.
Phys Chem Chem Phys. 2012 Feb 28;14(8):2940-50. doi: 10.1039/c2cp23643e. Epub 2012 Jan 19.
Photoinduced charge separation processes of three-layer supramolecular hybrids, fullerene-porphyrin-SWCNT, which are constructed from semiconducting (7,6)- and (6,5)-enriched SWCNTs and self-assembled via π-π interacting long alkyl chain substituted porphyrins (tetrakis(4-dodecyloxyphenyl)porphyrins; abbreviated as MP(alkyl)(4)) (M = Zn and H(2)), to which imidazole functionalized fullerene[60] (C(60)Im) is coordinated, have been investigated in organic solvents. The intermolecular alkyl-π and π-π interactions between the MP(alkyl)(4) and SWCNTs, in addition, coordination between C(60)Im and Zn ion in the porphyrin cavity are visualized using DFT calculations at the B3LYP/3-21G() level, predicting donor-acceptor interactions between them in the ground and excited states. The donor-acceptor nanohybrids thus formed are characterized by TEM imaging, steady-state absorption and fluorescence spectra. The time-resolved fluorescence studies of MP(alkyl)(4) in two-layered nanohybrids (MP(alkyl)(4)/SWCNT) revealed efficient quenching of the singlet excited states of MP(alkyl)(4) ((1)MP(alkyl)(4)) with the rate constants of charge separation (k(CS)) in the range of (1-9) × 10(9) s(-1). A nanosecond transient absorption technique confirmed the electron transfer products, MP˙(+)(alkyl)(4)/SWCNT˙(-) and/or MP˙(-)(alkyl)(4)/SWCNT˙(+) for the two-layer nanohybrids. Upon further coordination of C(60)Im to ZnP, acceleration of charge separation via(1)ZnP* in C(60)Im→ZnP(alkyl)(4)/SWCNT is observed to form C(60)˙(-)Im→ZnP˙(+)(alkyl)(4)/SWCNT and C(60)˙(-)Im→ZnP(alkyl)(4)/SWCNT˙(+) charge separated states as supported by the transient absorption spectra. These characteristic absorptions decay with rate constants due to charge recombination (k(CR)) in the range of (6-10) × 10(6) s(-1), corresponding to the lifetimes of the radical ion-pairs of 100-170 ns. The electron transfer in the nanohybrids has further been utilized for light-to-electricity conversion by the construction of proof-of-concept photoelectrochemical solar cells.
三层超分子杂化物（富勒烯-卟啉-SWCNT）的光诱导电荷分离过程已在有机溶剂中进行了研究，该杂化物由半导体（7,6）和（6,5）富集的 SWCNT 构建，并通过π-π相互作用的长烷基链取代卟啉（四（4-十二氧基苯基）卟啉；缩写为 MP(alkyl)(4)）（M = Zn 和 H(2)）自组装而成，其中咪唑官能化富勒烯[60]（C(60)Im）与之配位。使用 DFT 计算（B3LYP/3-21G() 水平）可视化了 MP(alkyl)(4)和 SWCNT 之间的分子间烷基-π 和 π-π相互作用，以及卟啉腔中 C(60)Im 和 Zn 离子之间的配位，预测了它们在基态和激发态之间的供体-受体相互作用。形成的供体-受体纳米杂化物通过 TEM 成像、稳态吸收和荧光光谱进行表征。在双层纳米杂化物（MP(alkyl)(4)/SWCNT）中研究了 MP(alkyl)(4)的时间分辨荧光，发现 MP(alkyl)(4)的单重激发态（(1)MP(alkyl)(4)）的猝灭效率很高，电荷分离速率常数（k(CS)）在（1-9）×10(9) s(-1)范围内。纳秒瞬态吸收技术证实了电子转移产物 MP˙(+)(alkyl)(4)/SWCNT˙(-)和/或 MP˙(-)(alkyl)(4)/SWCNT˙(+)对于双层纳米杂化物。当 C(60)Im 进一步配位到 ZnP 时，观察到通过(1)ZnP*在 C(60)Im→ZnP(alkyl)(4)/SWCNT 中的电荷分离加速，形成 C(60)˙(-)Im→ZnP˙(+)(alkyl)(4)/SWCNT 和 C(60)˙(-)Im→ZnP(alkyl)(4)/SWCNT˙(+)电荷分离态，瞬态吸收光谱支持这一点。这些特征吸收随由于电荷复合（k(CR)）在（6-10）×10(6) s(-1)范围内而衰减，对应于自由基离子对的寿命为 100-170 ns。通过构建概念验证光电化学太阳能电池，纳米杂化物中的电子转移进一步用于光到电的转换。
