ABSTRACT
We report the fabrication of nanostructured microcantilevers employed as sensors for the detection of organophosphorus (OPs) vapors. These micromechanical sensors are prepared using a two-step procedure first optimized on a silicon wafer. TiO2 one-dimensional nanostructures are synthesized at a silicon surface by a solvothermal method and then grafted with bifunctional molecules having an oxime group known for its strong affinity with organophosphorus compounds. The loading of oxime molecules grafted on the different nanostructured surfaces was quantified by UV spectroscopy. It has been found that a wafer covered by vertically aligned rutile TiO2 nanorods (NRs), with an average length and width of 9.5 µm and 14.7 nm, respectively, provides an oxime function density of 360 nmol cm-2. The optimized TiO2 nanorod synthesis was successfully reproduced on the cantilevers, leading to a homogeneous and reproducible TiO2 NR film with the desired morphology. Thereafter, oxime molecules have been successfully grafted on the nanostructured cantilevers. Detection tests were performed in a dynamic mode by exposing the microcantilevers to dimethyl methylphosphonate (a model compound of toxic OPs agents) and following the shift of the resonant frequency. The nanostructure and the presence of the molecules on a TiO2 NR surface both improve the response of the sensors. A detection limit of 2.25 ppm can be reached with this type of sensor.
ABSTRACT
The present works report the first structure-property relationship study of a key class of organic semiconductors, that is, the four spirobifluorene positional isomers possessing a para-, meta- or ortho-linkage. The remarkable and surprising impact of the ring bridging and of the linkages on the electronic properties of the regioisomers has been particularly highlighted and rationalised. The impact of the ring bridging on the photophysical properties has been stressed with notably the different influence of the linkages and the bridge on the singlet and triplet excited states. The first member of a new family of spirobifluorenes substituted in the 1-position, which presents better performance in blue phosphorescent OLEDs than those of its regioisomers, is reported. These features highlight not only the great potential of 1-substituted spirobifluorenes, but also the remarkable impact of regioisomerism on electronic properties.
ABSTRACT
A new electron-rich fragment, namely the quinolinophenothiazine (QPTZ) is reported. The QPTZ fragment incorporated in spiroconfigured materials leads to higher performance in blue Phosphorescent OLEDs than structurally related phenylacridine and indoloacridine based materials (increasing the HOMO energy level, modulating the spin-orbit coupling, etc.) and leads to highly efficient blue phosphorescent organic light emitting diodes, indicating the strong potential of this new molecular fragment in organic electronics.
