Phimwipha Piyakulawat

Novel low-band-gap conjugated polymers using an alternating donor/acceptor repeat unit

Abstract A series of new π-conjugated donor-acceptor copolymers, based on a naphthalene-bisimide moiety as the electron-acceptor and connected to either thiophene or dialkylfluorene as the electron-donor, were synthesized. The polymers are soluble in common organic solvents. The UV-Vis spectra of the copolymers in chloroform showed two absorption maxima at higher energies (ca. 301 - 364 nm), assigned to the π-π * transition, and at a lower energy (ca. 512 - 595 nm), ascribed to the intramolecular charge transfer between donor and acceptor units. Cyclic voltammetry revealed that the polymers were susceptible to both electrochemical oxidation and reduction, and they had a LUMO and HOMO levels ranging from -4.07 to -3.80 eV and -6.13 to -5.64 eV, respectively. The energy band gaps were estimated to be 1.48 - 2.06 eV. These results represent a positive step towards making novel compounds suitable for electronic applications.

TiOx Concentration Dependence of OPV Efficiency Optimization

Titanium oxide TiOx material is used as electron transporter in organic photovoltaic cells (OPV). The layer was prepared between P3HT:PCBM as the active layer and the and aluminum electrode by spin coating technique. The synthesis and characterization of TiOx is described. Using Raman spectroscopy technique TiOx crystals show anatase structure. Varied concentrations of TiOx and isopropanol solvent were performed. The most optimized device efficiencies up to 2,0% was achieved at a 1:20 ratio, which indicated more than 50% efficiency enhancement comparing with the device without TiOx layer. The major improvement of the cell was originated from photocurrent enhancement.

Heavy metal detection by electrochemical electronic tongue with poly(thiophene)-metal oxide nanoparticle composite electrodes

Rapid monitoring methods of heavy metals in water are in great demand for industrial environmental managements. This work aims to develop a heavy metal sensing device based on an electrochemical electronic tongue using a hybrid composite of metal oxide nanoparticles and conductive polymer as the working electrodes. The electrodes were prepared by drop-casting colloidal mixtures of Regioregular poly(3-hexylthiophene) (P3HT) and metal oxide nanoparticles (ZnO or TiO2) in chloroform onto a fluorine-doped tin oxide (FTO) glass. Optical microscopy measurements reveal some microstructural organization of the metal oxide-P3HT composite films on the electrodes, in comparison to a smooth P3HT film. Cyclic voltammetry (CV) measurements using bare FTO, P3HT, P3HT/ZnO and P3HT/TiO2 electrodes were performed on aqueous solutions of various metal acetates at the concentration of 0.01M. The Principal Component Analysis (PCA) was applied to the CV results to obtain the classification of the data from the various metal salt solutions. The PCA score plot exhibits a clear separation of the data groups of different heavy metals, with the highest distinction between zinc and lead. The PCA loading plot confirms that the different electrochemical nature of the various electrodes is responsible for such distinctive classification. Further work is to examine the capability of the electrochemical electronic tongues for semi-quantitative analyses of the metal salt concentration.

Preparation of Highly Monodisperse Polymeric Particles Incorporating Polymerizable Perylene-Bisimide Fluorophore

In this work, the yellow emitted perylene-bisimide dye with polymerizable functional groups was synthesized by condensation reaction of perylene tetracarboxylic acid dianhydride and allyl amine. The resulting polymerizable fluorophore was characterized in terms of structure with NMR and FT-IR, the absorption and emission properties by using UV-Vis and fluorescence spectroscopy, respectively. Afterwards, the reactive polymerizable fluorophore was incorporated into the polymer nanoparticle by copolymerization with styrene and acrylic acid monomers via miniemulsion polymerization. The obtained fluorescent nanoparticles was stable and showed a highly monodisperse size distribution with hydrodynamic diameter of 91.8±0.4 nm.