Qingfu Zhou

A new type of organic-inorganic multilayer: fabrication and photoelectric properties

Abstract Fabrication and photoelectric characteristics of a new type of organic-inorganic alternating multilayer are reported. The multilayers exhibit a strong photovoltaic response in spite of their weak absorbance. Electric field induced surface photovoltage spectroscopy (EFISPS) indicates obvious unilateral selectivity for the application of an external voltage on multilayers

Fabrication, characterization and photovoltaic study of a TiO2 microporous electrode

Abstract A transparent titanium dioxide (TiO 2 ) film of thickness 1 μm has been prepared by speading colloidal particles on a conducting glass support. Atomic force microscope analysis reveals that the film is composed of interconnected particles and pores. The roughness factor of the TiO 2 microporous electrode is determined to be 50 by an absorption spectroscopy study. Sensitization of electrode with phthalocyanine molecules extends the absorbance of the electrode into the visible region. At 690 nm, the incident-photon-to-current-conversion efficiency is about 4%, one of the highest ever reported for phthalocyanine photovoltaic cells.

Singlet—singlet intramolecular energy and electron transfer in covalently-linked porphyrin—phthalocyanine heterodimers

Abstract Intramolecular transfer processes in porphyrin—phthalocyanine heterodimers covalently linked by an oxygen atom (restricted conformation) and/or by a flexible chain of variable length were investigated. Fluorescence spectroscopy shows that singlet—singlet energy transfer from the porphyrin to the phthalocyanine moiety occurs. From fluorescence decay studies, it is concluded that the heterodimers exist in solution in different non-equilibrating conformations. The effects of the chain length and mutual orientation of the chromophore subunits in the heterodimers on the intramolecular energy and electron transfer efficiencies are discussed.

The gas response behavior of spin-coated phthalocyanine films to NO2

Abstract The spin-coated films of 2,9,16,23-tetra(heptyloxy)phthalocyanine showed very good gas sensing properties to NO 2 at room temperature. The response and recovery are rapid and complete with good reproducibility and high sensitivity. The magnitude of response of the film to NO 2 are enhanced by irradiation with light. This may be ascribed to the decrease in the activation energy for the charge transfer interaction between the phthalocyanine donor and the gas acceptor by light excitation.

Gas sensing properties of asymmetrically substituted phthalocyanines bearing one crown ether ring

The gas sensing-properties of phthalocyanine bearing one crown ether ring are investigated using different thin film deposition methods. Those well ordered and tightly packed LB films display slower response and reversal time while an incompact spin-coated film reveals that both response and reversal are much faster and complete with good reproducibility and high sensitivity. These results indicate that films prepared by different fabrication techniques show different response and reversal kinetics.

Optical and electrical properties of organic-inorganic composite system

Abstract Anionic phthalocyanine sodium hydrogallium 4,4′,4″,4‴-tetrasulfonated phthalocyanine(GaTsPc) was used to modify the surface of a size-quantized particulate TiO 2 photoelectrode fabricated by electrostatic attraction. The photovoltaic features and interfacial electron transfer of the electrodes were studied by a photoelectrochemical method and surface photovoltage spectroscopy. The results indicate that the light absorption of phthalocyanine monomer makes more contribution to the photovoltaic response in the TiO 2 /GaTsPc composite electrode in spite of obvious aggregation occurring in composite electrode.

Novel Langmuir—Blodgett films, consisting of amphiphilic zinc phthalocyanine and hydrophobic porphyrin

Abstract An amphiphilic zinc phthalocyanine (AmZnPc) containing long alkyl chains covalently attached to the positively charged macroring was synthesized. A monolayer of AmZnPc with equimolar meso-tetrakis-(4-tolyl)porphine (TTP) was spread on water from chloroform solution and transferred onto CaF 2 slides. Multilayers were also built up on these substrates. Surface pressure-area isotherms and UV—visible absorption spectra showed that the porphyrin molecules are arranged in the cavity between the long alkyl chains of AmZnPc in one layer of the Langmuir—Blodgett film. Polarized UV—visible spectroscopy indicated that there is no anisotropy in the layer plane and the AmZnPC macroring plane lies nearly parallel to the substrate surface.

Dynamic studies of charge-separated-state enhancement of the optical nonlinearity of a porphyrin heterodimer

Light‐induced enhancement of the third‐order nonlinear optical susceptibility of a heterodimer consisting of two different porphyrin monomers, a zinctetra(4‐sulfonatophenyl)porphyrin and a zinctetra(4‐N‐methyl‐pyridyl)porphyrin, was observed when the sample was optically pumped by a 30 ps, 532 nm pump pulse. The temporal behavior of the enhancement was studied. It was found that the enhancement was due predominantly to the population of the charge‐separated state with a large electronic third‐order nonlinear optical susceptibility

Interaction between tetrasulfophthalocyanines and colloidal titanium dioxide and photoelectric behavior on sensitized microporous TiO2 electrodes

ConclusionStrong interaction between sulfophthalocyanines and TiO2 occur when the former is adsorbed on the colloidal TiO2 surface. Upon excitation, electron transfer from excited singlet state of sulfophthalocyanine to the conduction band of TiO2 occurs, leading to the quenching of sulfophthalocyanine fluorescence. Sensitization of the TiO2 microporous electrode with sulfophthalocyanine extends the photoresponse of the electrode to visible and near IR region as shown by the photocurrent spectra. It is indicated that only monomeric sulfophthalocyanine plays a dominant role in the photoresponse of the electrode, while the sulfophthalocyanine aggregates give less or even no contribution to the conversion of visible light into electricity.

Photoinduced electron transfer and dynamic behavior of charge-separated state nonlinear optical process in a self-assembled porphyrin supramolecular system

Abstract The spectroscopic properties of a supramolecular system consisting of two oppositely charged porphyrin monomers, zinc tetra(4-sulfonoatophenyl)porphyrin and zinc tetra(N-methylpyridyl)porphyrin were studied by absorption and fluorescence spectroscopy. The stoichiometry of the self-assembled porphyrins were determined by a fluorimetric titration method showing the formation of the 1:1 heterodimer. Photoinduced electron transfer and charge separation in the supramolecular system have been studied by time resolved forward degenerate-four-wave-mixing (DFWM) geometry. The results indicated the formation of the charge-separated state within 30 ps and the recombination time is about 340 ps. Light-induced enhancement of third-order nonlinear optical (NLO) susceptibility was observed.