RESUMO
Two ruthenium(II) polypyridyl complexes [Ru(tpy)(ptn)](2+) (1) and Ru(dmtpy)(ptn)](2+) (2) (ptn=3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f]naphthalene, tpy=2,2':6',2"-terpyridine, dmtpy=5,5'-dimethyl-2,2':6',2"-terpyridine) have been synthesized and characterized by elemental analysis, (1)H NMR, mass spectrometry and crystal structure analysis. Spectroscopic studies together with isothermal titration calorimetry (ITC) and viscosity measurements prove that two complexes bind to DNA in an intercalative mode. ITC experiments show that the binding mode for complex 2 is entropically driven, while an entropy-driven initial binding of complex 1 is followed by an entropically and enthalpically favorable process. This difference may be attributed to the ancillary ligand effects on the DNA binding of Ru(II) complexes. Circular dichroism titrations of calf thymus DNA (CT-DNA) with Ru(II) complexes show that complexes 1 and 2 induce B to Z conformational transition of calf thymus DNA at low ionic strength (0.05 M NaCl). The induced Z-DNA conformation can revert to B form when Ru(II) complexes are displaced by ethidium bromide or at high ionic strengths ([NaCl]=0.4 M), but keeps intact with temperature ranged from 25 to 90 °C. The unique structure and characteristics of Ru(II) complexes designed in this investigation will be useful for the study of Z-DNA.
Assuntos
Complexos de Coordenação/síntese química , DNA de Forma B/química , DNA Forma Z/química , DNA/química , Substâncias Intercalantes/síntese química , Rutênio/química , Animais , Sítios de Ligação , Calorimetria , Bovinos , Dicroísmo Circular , Cristalografia por Raios X , Etídio/química , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Concentração Osmolar , Cloreto de Sódio/química , Temperatura , Termodinâmica , ViscosidadeRESUMO
An in situ electrodeposition method is described to fabricate the CdS or/and CdSe quantum dot (QD) sensitized hierarchical TiO(2) sphere (HTS) electrodes for solar cell application. Intensity modulated photocurrent spectroscopy (IMPS), intensity modulated photovoltage spectroscopy (IMVS) and electrochemical impedance spectroscopy (EIS) measurements are performed to investigate the electron transport and recombination of quantum dot-sensitized solar cells (QDSSCs) based on HTS/CdS, HTS/CdSe, and HTS/CdS/CdSe photoelectrodes. This dynamic study reveals that the CdSe/CdS cosensitized solar cell performs ultrafast electron transport and high electron collection efficiency (98%). As a consequence, a power conversion efficiency as high as 4.81% (J(SC) = 18.23 mA cm(-2), V(OC) = 489 mV, FF = 0.54) for HTS/CdS/CdSe photoelectrode based QDSSC is observed under one sun AM 1.5 G illumination (100 mW cm(-2)).
