Wen-Ren Li

Heterocyclic 1,3,4-oxadiazole as columnar core

The synthesis, characterization and mesomorphic properties of a new type of liquid crystalline compound, the 2,5-bis(3,4,5-trialkoxyphenyl)-1,3,4-oxadiazoles, 3a-3h, are reported. These heterocyclic compounds are derived from unsaturated 1,3,4-oxadiazole as the core group, and obtained by the condensation reaction of 3,4,5-trialkoxybenzoic acid N-(3,4,5-trialkoxybenzoyl)-hydrazides and phosphorus oxychloride in toluene under reflux. All compounds were characterized by 1H and 13C NMR spectroscopy, and elemental analysis. The mesomorphic properties of these and the related compounds 1, 2 were characterized and studied by differential scanning calorimetry and polarizing optical microscopy. The formation of columnar mesophases was found to be dependent on the numbers of alkoxy sidechains. The compounds 3 exhibited hexagonal columnar (Colh) phases, however compounds 1, 2 formed crystalline phases. Compounds 3b-3e with shorter carbon chains were room temperature liquid crystals. Polar induction by nitrogen and/or oxygen atoms on the heterocyclic core ring might be responsible for the formation and better observed mesomorphic properties in this type of compound.

Protein Tyrosine Phosphatases and their Inhibitors

Protein tyrosine phosphatase (PTP) is the family of enzymes that are key players in cellular signal transduction system and perturbation in their functioning is implicated in many disease-states. Diverse chemical compounds are being synthesized and evaluated as PTP inhibitors. This review presents a brief account of various enzymes of the PTP family and their inhibitors. Peculiar features of these enzymes and their roles in various diseases are summarized along with important inhibitors developed in recent years.

Development and residue screening of the furazolidone metabolite, 3-amino-2-oxazolidinone (AOZ), in cultured fish by an enzyme-linked immunosorbent assay.

A sensitive and specific polyclonal enzyme-linked immunosorbent assay (ELISA) for the determination of tissue-bound metabolite 3-amino-2-oxazolidinone (AOZ) is described. The procedures allow for the detection of protein-bound AOZ in the form of a 2-nitrophenyl derivative (2-NP-AOZ) in the sample supernatant or extract after acid hydrolysis and derivatization with o-nitrobenzaldehyde. The polyclonal rabbit antibodies were produced with the immunogen hapten, 2-NP-HXA-AOZ, and the 50% inhibition values (IC(50)) of 0.14 microg kg(-1) of AOZ was achieved with the most sensitive antibody A0505. The mean lower detection limit of the ELISA method is about 0.025 microg kg(-1). According to the test preparation record, the detection limit is 0.1 microg kg(-1), which is well below the minimum required performance limits (MRPLs) for tissue-bound residues of AOZ at 1 microg kg(-1) in the European Communities. In the present study, we investigated the use of homemade ELISA, a new immunoassay, to monitor the presence of the furazolidone marker residue in 370 samples of cultured fish. Adopting 0.3 microg kg(-1) AOZ as a cutoff value, the ELISA has a sensitivity of 100% and a specificity of 98.5% versus high-performance liquid chromatography-mass spectrometry (HPLC-MS) at a cutoff of 0.3 microg kg(-1) and gives no false-negative rate results. From the practical point of view, the homemade kit could be advantageously used for the screening of large groups of animal-edible tissue samples and the kit employed has good reliability even in routine application for the control of the illegal use of the drug.

Carbene-based ruthenium photosensitizers

A new series of N-heterocyclic carbene (NHC)-pyridine ruthenium complexes incorporating a carbene unit as an ancillary ligand were designed and successfully synthesized by using simple synthetic methods. The photophysical, electrochemical and photovoltaic properties of these NHC-pyridine based ruthenium complexes were investigated. These complexes showed photoelectric conversion efficiencies in the range of 6.43 ∼ 7.24% under the illumination of AM 1.5 (100 mW cm(-2)). Interestingly, the modifications on the ancillary ligand of these sensitizers by removal of an alkoxyl group and replacement of the octyl chain with a 3,5-difluorobenzyl group showed a 13% increase in the conversion efficiency for the CifPR dye. These results demonstrated that structural modifications on the NHC-pyridine ancillary ligand of ruthenium complexes results in dye-sensitized solar cells exhibiting a comparable cell performance to that obtained using the standard N719 dye.

RATIONAL DESIGN AND SYNTHESIS OF UNSATURATED 2,5-DIOXOPIPERAZINE DERIVATIVES AS POTENTIAL PROTEIN TYROSINE KINASE INHIBITORS

Abstract The first general method for the synthesis of a library of trifunctionalized (Z)-3-alkylidene-2,5-piperazinediones as potential protein tyrosine kinase inhibitors from commercially available amino compounds, α-keto acids and aldehydes using a novel cyclization/cleavage strategy on solid support is described.

New Pyridinium Ylide Dyes for Dye Sensitized Solar Cell Applications

Novel organic pyridinium ylide sensitizers (NO109-111) consisting of various anchoring groups were synthesized and characterized for applications in dye sensitized solar cells. Compared with the pyridine-N-oxide dye (NO108), the ylide sensitizers with strong electron-withdrawing acceptors exhibited dominant ultraviolet absorption properties and efficient binding abilities to the TiO2 surface. Among these dyes, the pyridinium ylide NO111 sensitized solar cell showed the highest efficiency (5.15%), which was improved to 7.41% by employing coadsorbent chenodeoxycholic acid.

Novel oxindole based sensitizers: synthesis and application in dye-sensitized solar cells.

Two novel oxindole sensitizers have been synthesized for dye-sensitized solar cell applications. These new dyes can provide an additional pathway to inject electrons into the photoanode through the partial chelation of their amide carbonyl groups to the TiO2 surface. Incorporation of an electron deficient pyridine in the acceptor of the TI125 dye was found to enhance the photovoltage and conversion efficiency of the cell.

Preparation and characterization of pure rutile TiO 2 nanoparticles for photocatalytic study and thin films for dye-sensitized solar cells

Pure rutile-phase TiO2 (r-TiO2) was synthesized by a simple one pot experiment under hydrothermal condition using titanium (IV) n-butoxide as a Ti-precursor and HCl as a peptizer. The TiO2 products were characterized by XRD, TEM, ESCA, and BET surface area measurement. The r-TiO2 were rodlike in shape with average size of ∼61 × 32nm at hydrothermal temperature of 220°C for 10 h. Hydrothermal treatment at longer reaction time increased the tendency of crystal growth and also decreased the BET surface area. The degradation of methylene blue was selected as a test reaction to confer the photocatalytic activity of as-obtained r-TiO2. The results showed a strong correlation between the structure evolution, particle size, and photocatalytic performance of r-TiO2. Furthermore, the r-TiO2-based solar cell was prepared for the photovoltaic characteristics study, and the best efficiency of ∼3.16% was obtained.

Preparation of smooth surface TiO 2 photoanode for high energy conversion efficiency in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) based on a TiO2 photoanode have been considered as an alternative source in the field of renewable energy resources. In DSSCs, photoanode plays a key role to achieve excellent photo-to-electric conversion efficiency. The surface morphology, surface area, TiO2 crystal phase, and the dispersion of TiO2 nanoparticles are the most important factors influencing the properties of a photoanode. The smooth TiO2 surface morphology of the photoanode indicates closely packed arrangement of TiO2 particles which enhance the light harvesting efficiency of the cell. In this paper, a smooth TiO2 photoanode has been successfully prepared using a well-dispersed anatase TiO2 nanosol via a simple hydrothermal process. The above TiO2 photoanode was then compared with the photoanode made from commercial TiO2 nanoparticle pastes. The morphological and structural analyses of both the aforementioned photoanodes were comprehensively characterized by scanning electron microscopy and X-ray diffraction analysis. The DSSC fabricated by using a-TiO2 nanosol-based photoelectrode exhibited an overall light conversion efficiency of 7.20% and a short-circuit current density of 13.34mA cm-2, which was significantly higher than those of the DSSCs with the TiO2 nanoparticles-based electrodes.

Preparation of Nanoporous TiO2 Electrodes for Dye-Sensitized Solar Cells

Nano-porous thin films have been widely used as the working electrodes in dye-sensitized solar cells (DSSCs). In this work, the phase-pure anatase (a-) and rutile (r-) have been prepared using hydrothermal processes. The investigation of photo-to-electron conversion efficiency of DSSCs fabricated from mixed- with a- and r- ratio of 80 : 20 (A8R2) was performed and compared to that from commercial (DP-25). The results showed higher efficiency of DSSC for A8R2 cells with same dependence of cell efficiency on the film thickness for both A8R2 and DP-25 cells. The best efficiency obtained in this work is 5.2% from A8R2 cell with film thickness of 12.0 . The correlation between the films thickness and photoelectron chemical properties of DSSCs fabricated from A8R2 and DP-25 was compared and discussed.