Huijun Xu

Synthesis, spectroscopic and thermal properties of a series of azo metal chelate dyes

A series of azo metal chelate dyes have been synthesized. The UV-Vis absorption spectra of the azo dye and its metal complexes were measured. The stoichiometry of the complex was determined by the spectroscopic titration method to be 1:2 (ML2), and the formation constants of the complexes were evaluated. Thermal decomposition with a sharp exothermic peak was observed by TG-DT Analysis.

Optical recording performance of thin films of phthalocyanine compounds

Abstract As organic dyes with excellent thermal and light stability, phthalocyanine compounds have been investigated as write-once read-many optical recording materials. By selecting different substituents and metallic ions, the absorption bands of thin film of phthalocyanine compounds were matched with the wavelengths of semiconductor lasers. It was found that the absorption regions of vacuum sublimated thin films of vanadyl phthalocyanine (VOPc), tetra-pentyloxy phthalocyanine vanadyl (TPPcVO) and tetra-nonyloxy phthalocyanine vanadyl (TNPcVO) were between 580 and 850 nm. In the near-IR region, the absorbance and reflectivity of thin films of VOPc were greater than 50% and 20% respectively. The static optical recording test of the VOPc thin film showed that the write power was less than 10 mW with the write pulse width of 200 ns using an He-Ne laser as light source. The dynamic optical recording test of VOPc as a write-once read-many recording material on a 5.25 in optical disk indicated that the carrier-to-noise ratio (CNR) was greater than 45 dB.

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

Improvement in photoelectric conversion of a phthalocyanine-sensitized TiO2 electrode by doping with porphyrin

Abstract The effect of doping with tetrasulfonated zinc porphyrin (ZnTsPP) on photoelectric conversion of a nano-structured titanium dioxide (TiO2) electrode sensitized with tetrasulfonated gallium phthalocyanine (GaTsPc) is reported. Doping with ZnTsPP greatly enhances the photocurrent response at long wavelength (the GaTsPc Q band of 640∼760 nm), with 20- and 60-fold improvement of the quantum efficiency at 680 and 700 nm, and results in an improvement of photoelectric conversion for the liquid junction solar cell based on the co-sensitized TiO2 electrode, although the photocurrent response in the Soret band of ZnTsPP is markedly decreased with 8-fold drop of the quantum efficiency at 430 nm. This may be attributed to the formation of the Pc/PP heteroaggregates on the nano-structured TiO2 electrode, resulting in the decreases of the concentration of GaTsPc dimers and the possible presence of a low-lying charge-transfer state.

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.

Photophysical properties and optical limiting property of a soluble chloroaluminum-phthalocyanine

A chloroaluminum-phthalocyanine (AlCl-Pc) with tetra-alpha-butoxy chains (AlCl-Pc-OC4) has been synthesized and the photophysical parameters have been determined using steady-state and time-resolved absorption as well as emission spectroscopy. A luminescence from S2 excited state with long lifetime (5.71ns) is observed. A multi level model has been proposed to explain the photophysical processes after Soret-band excitation (lambdaex=355nm). The optical limiting performance for 532nm-7ns laser pulses of AlCl-Pc-OC4 has been investigated in THF solution. The sigmaex and ratio of sigmaex/sigma0 has been calculated. The good optical limiting performance is attributed to a reverse saturable absorption mechanism. It indicates that AlCl-Pc-OC4 could be promising candidates for optical limiting material.

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.

Investigation of third-order nonlinearity of an azo dye and its metal-substituted compounds

Abstract The real part of third-order optical nonlinearity of an azo dye (2-(2-thiazolylazo)-5-diethylaminophenol, TAEP) and those of its copper- and cobalt-substituted compounds are measured by using femtosecond optical heterodyne optical Kerr gate technique at the wavelength of 647 nm. All the values are found to be negative. Those of Cu- and Co-substituted compounds are found to be larger than that of the metal-free dye by two and three orders of magnitude, respectively. A negative γ eff as large as 10 −29 esu is found in Co complex. We use a three-level model to characterize the nonlinear process, and suggest that π-electron delocalization in metal complex leads to an enhancement.

Photosensitization of TiO2 semiconductor with porphyrin

Zn-tetrasulfophenylporphyin (ZnTSPP), stable colloidal TiO2 and a transparent microporous TiO2 electrode have been prepared. The interaction of ZnTSPP with colloidal TiO2 was studied by absorption and fluorescence spectroscopy, the apparent association constant for the association between ZnTSPP and TiO2 nanoparticles is about 1.6 × 104 M−1. ZnTSPP adsorbed on colloidal TiO2 can participate in the sensitization process by injecting electrons from its excited states into the conduction band of TiO2. Upon excitation of its absorption band, 90% of the fluorescence emission of ZnTSPP could be quenched by colloidal TiO2 and the maximum of incident photon to current efficiency is 51.3% at 427 nm with a 10 μm thick TiO2 film sensitised by ZnTSPP.

Ultrafast optical Kerr effect of phthalocyanine

Abstract The resonant optical Kerr effect in the Langmuir-Blodgett film, spin-coating film and solution of 2,9,16,23-tetra-heptadecyl-amido-substituted vanadyl phthalocyanine was measured with femtosecond laser pulses to determine the relaxation time and ultrafast nonlinear optical susceptibility, and two slow decay components were also observed.