Pu-Hui Xie

Highly efficient charge transfer from a trans-ruthenium bipyridine complex to nanocrystalline TiO2 particles

trans-Di(isothiocyanato)-[N-bis(2,2′-bipyridyl-4,4′-dicarboxylic acid) ruthenium(II) acts as a very efficient charge-transfer sensitizer for nanocrystalline TiO2 films. The incident photon-to-electron conversion efficiency (IPCE) for the dye-coated TiO2 film exceeded 80% in the wavelength domain between 400 and 600 nm. A sandwich-type regenerative solar cell fabricated from a 10 μm thick TiO2 film sensitized with this dye generated a short-circuit photocurrent of 19.6 mA cm−2 and an open-circuit photovoltage of 720 mV in simulated AM1.5 solar light (924 W m−2) with an overall power conversion efficiency of 8.6%.

Synthetic control of the photophysical and photoelectrochemical properties of ruthenium(II) polypyridyl complexes

Abstract Two classes of useful complexes of cis-Ru(bpy-X)2(NCS)2 and [Ru(bpy)2(bpy-X)]2+ have been prepared and their spectroscopic and photoelectrochemical properties investigated. All the complexes ([Ru(bpy)2(bpy-X)]2+) examined display luminescence at room temperature. The energy of the emission maximum is red shifted for both electron-withdrawing and electron-donating substituents compared to that of parent [Ru(bpy)3]2+ complex. Furthermore, the complexes bearing electron-acceptor substituents have higher luminescence quantum yield and longer excited-state lifetime than that of the compounds bearing electron-donating ones. Such behaviors demonstrate that the values of rate constants for radiationless decay from the luminescent excited state to the ground state are determined not only by the energy gap but also by the nature of the substituents, which presumably influenced the changes in the equilibrium displacement between the two levels. In addition, the photoelectrochemical results of the cis-Ru(bpy-X)2(NCS)2 clearly show that the nature of the substituents on the bpy ligands does not substantially affect the photon-to-electric energy conversion efficiency.

Synthesis and photoelectric studies of Ru(II) polypyridyl sensitizers

New cis-Ru(3,3′-dcbpy)2(NCS)2 photosensitizer (where 3,3′-dcbpy is 3,3′-dicarboxy-2,2′-bipyridine) was synthesized using Ru(DMSO)4Cl2 as a starting material and characterized. Its photophysical and redox properties were compared with those of cis-Ru(4,4′-dcbpy)2(NCS)2 and cis-Ru(5,5′-dcbpy)2(NCS)2.The photoelectrochemical properties of the three dyes adsorbed on the surface of the nanocrystalline TiO2 electrodes as well as on self-assembly monolayers (SAMs) were investigated. The photocurrents generated by sensitized TiO2 electrodes were much higher than those by SAMs. And cis-Ru(4,4′-dcbpy)2 showed a most efficient photosensitizer in both systems. The mechanism is discussed in the paper.

Study on emission quenching by 2,2,6,6-tetramethyl-1-piperidinyloxy free radical

The emission quenching mechanism of four emissive compounds by 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) was investigated using steady state and transient state spectroscopy. The quenching mechanism was considered to be the radical triplet pair mechanism (RTPM) from the experimental results of both the emission quenching study and the steady state and time resolved electron spin resonance (SSESR and TRESR) studies.

Effect of steric hindrance on photoinduced electron transfer of self-assembled monolayers of three isomeric Ru(II)-bipyridine complexes on ITO electrode

Three kinds of self-assembled monolayers (SAMs) of isomeric Ru(II)-bipyridine complexes: cis-di(thiocyanato)-bis(2,2′-bipyridyl-3,3′-dicarboxylate) ruthenium (dye A), cis-di(thiocyanato)-bis(2,2′-bipyridyl-4,4′- dicarboxylate) ruthenium (dye B) and cis-di(thiocyanato)-bis(2,2′-bipyridyl-5,5′- dicarboxylate) ruthenium (dye C), were fabricated on hydrophilic transparent indium tin oxide (ITO) electrode. The UV-visible spectra, contact angle, XPS and cyclic voltammetry of these SAMs were measured. The photoinduced electron transfer properties were determined both in propylenecarbonate (PC) electrolyte and KCl electrolyte. A possible mechanism of electron transfer of these systems was proposed.