Hongjian Tian

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

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.

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.

Preparation of some II-VI semiconductor films by thermal or electron beam evaporation and by hot wall epitaxy and their optical characterization

Abstract Thin films of CdS and related materials were grown by thermal evaporation, by electron beam evaporation and by hot wall epitaxy onto various substrates. In the case of evaporation it was necessary to anneal the films after growth, in contrast to the epitaxy. Simultaneous evaporation of two semiconductor materials leads to ternary films with an absorption edge depending on the composition. Alternating evaporation of two materials leads to multilayer heterostructures demonstrating new effects. Absorption and luminescence measurements have been used for optical characterization. Some non-linear optical measurements are also presented concerning mainly photothermally induced optical bistability.

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.

STRUCTURE DEPENDENCE OF INTRAMOLECULAR PHOTOINDUCED ELECTRON TRANSFER IN 9-AMINOACRIDINE BENZOYL ESTERS DYADS LINKED BY A POLYETHER CHAIN

ConclusionsBoth experimental observations and theoretical calculations indicated that: (I) The flexible dyads reported in this paper exist preferentially in folded conformations in which the donor and the acceptor are held in close proximity. This allows overlap of the orbitals of each moiety leading to very efficient intramolecular fluorescence quenching. (ii) Quenching of the fluorescence of the donor in the dyads via electron transfer depends on the electron affinity of the acceptor. (iii) The electron-attracting ability of the acceptors in the dyads is strongly influenced by the type and relative spatial disposition of the substituents.