RESUMO
Different surface densities of gold nanoparticles (AuNPs) were deposited on (3-aminopropyl)-trimethoxysilane (APTMS)-modified indium tin oxide (ITO) electrode. The electrodes were then used in poly(3-hexylthiophene): phenyl-C61-butyric-acid-methylester (P3HT:PCBM) solar cells. Enhanced photo-conversion efficiency was observed from solar cells containing adsorbed AuNPs with surface density equals to 10 +/- 3 NPs/microm2. For higher surface densities (215 +/- 10 NPs/microm2), the presence of the plasmonic material significantly reduced the efficiency of the solar cell. Impedance spectroscopy (IS) indicates changes of the electrical characteristics, evident by a drastic reduction of the impedance relative to the reference cells, from electrodes modified with high densities of AuNPs.
RESUMO
2-Phenyl-benzoxazole and five derivatives bearing an alkyl or alkoxy substituent on the phenyl ring were used to prepare aqueous suspensions of particles via a solvent-exchange method. In these conditions, the methyl and methoxy derivatives spontaneously gave nanofibers, while the other compounds led to microcrystals. This shows that minor chemical changes are enough to direct the formation of a given type of particle. From a spectroscopic viewpoint, all compounds strongly emit blue light in the solid state, with spectra much broader than those registered in n-heptane and ethanol solutions. The photoluminescence quantum yields reached 38% and were slightly affected in aqueous suspension by the polarity of the environment. The molecular arrangement, deduced from X-ray analysis for the methyl and methoxy derivatives, was used to explain the fluorescence properties in the solid state. This work shows that 2-phenyl-benzoxazole derivatives are interesting candidates for applications as fluorescent nanomaterials, including in aqueous and biological media.
