We present a novel plasmonic sensor configuration that allows the discrimination of chiral molecules. The sensor consists of handed gold nanostructures of gammadion shape, distributed in a racemic (50/50 mixture) matrix with C4 symmetry. Its optical response enhances the interaction with molecules thus circular dichroism can be measured in the visible range. The bare sensors exhibit a flat CD signal, providing background-free CD measurements for molecular detection. We have used a chiral molecular model based on L-, D-, and the racemic mixture of phenylalanine, which allows us to evaluate the opposite chiral effects while having a reference system. Additionally, we have used molecular thermal evaporation technique to deposit a dense molecular layer on top of the sensors in a controllable and reproducible way. Our results show the discrimination of phenylalanine enantiomers through positive or negative peaks while the racemic mixture shows a flat signal. In addition, we present preliminary results that show that this approach is also suitable for microfluidics systems with a much lower density of chiral molecules.
The OTFTs with both p type and n type channel layers were fabricated using the inverted-staggered (top contact) structure by thermal vapour deposition on Si/SiO<sub>2</sub> substrate. Pentacene and N,N’-Dioctyl- 3,4,9,10-
perylenedicarboximide (PTCDI-C8) were used as channel layer for the fabrications of p type and n type OTFTs respectively. A comparative study on the degradation and density of states (DOS) of p type and n type organic semiconductors have been carried out. In order to compare the stability and degradation of pentacene and PTCDI-C8 OTFTs, the devices were exposed to air for 2 h before performing electrical measurements in air. The DOS
measurements revealed that a level with defect density of 10<sup>20</sup> cm<sup>-3</sup> was formed only in PTCDI C8 layer on exposure to air. The oxygen adsorption into the PTCDI-C8 active layer can be attributed to the formation of this level at 0.15 eV
above the LUMO level. The electrical charge transport is strongly affected by the oxygen traps and hence n type organic
materials are less stable than p type organic materials.
This work describes the infiltration of a polymeric solution into porous Si structures towards the fabrication of
tunable photonic crystals (PC) and microcavities for photonics applications. The tunability is achieved by infiltrating the
porous silicon based PCs by active organic materials, such as an emissive and nonlinear polymer called 2-methoxy-5-(2-
ethylhexyloxy)-p-phenylenevinylene (namely MEH-PPV). This preliminary work shows the infiltration of this polymeric
solution into PC based on macroporous Si structure as well as in microcavities based on multiple layers of microporous
Si. The solidification of the polymer was obtained by the evaporation of the solvent. Various techniques of infiltration
were studied to obtain an optimized filling of the pores. The infiltration was then characterized using photoluminescence
measurements. Finally, we will report on the study of third harmonic generation (THG) in samples of porous silicon
microcavity infiltrated with MEHPPV. The k-domain THG spectroscopy was applied and an increase of the THG
intensity up to an order of magnitude was achieved for the filled microcavity.
We report here on the results of the characterization of a novel -OPhCN substituted thiophenic monomer, and of the obtained copolymers between the latter and the plastifying comonomer 3-hexylthiophene. The polymer evidences an excellent filmability from various organic solvents as well as an enhanced photoluminescence. The characteristics of the polymer were characterized by FTIR and XRD as well as photoluminescence. A bandgap of 2.0eV was obtained which corresponds to orange emission. Furthermore, a single layer organic device was fabricated and resulted in bright stable electroluminescence at room temperature. All of the results indicate that this polymer is a promising emissive material for application in light-emitting devices (LEDs).