Haichuan Mu

High sensitive formaldehyde graphene gas sensor modified by atomic layer deposition zinc oxide films

Zinc oxide (ZnO) thin films with various thicknesses were fabricated by Atomic Layer Deposition on Chemical Vapor Deposition grown graphene films and their response to formaldehyde has been investigated. It was found that 0.5 nm ZnO films modified graphene sensors showed high response to formaldehyde with the resistance change up to 52% at the concentration of 9 parts-per-million (ppm) at room temperature. Meanwhile, the detection limit could reach 180 parts-per-billion (ppb) and fast response of 36 s was also obtained. The high sensitivity could be attributed to the combining effect from the highly reactive, top mounted ZnO thin films, and high conductive graphene base network. The dependence of ZnO films surface morphology and its sensitivity on the ZnO films thickness was also investigated.

Fabrication and Characterization of Amino Group Functionalized Multiwall Carbon Nanotubes (MWCNT) Formaldehyde Gas Sensors

Multiwall carbon nanotubes (MWCNTs) formaldehyde gas sensors functionalized with amino group were fabricated on interdigitated electrodes and the effects of the amount of amino group functionalized, sensing layer thickness, operating temperature, and humidity on the sensors sensitivity were investigated. The MWCNTs sensors with the optimal amount of 18.19 wt% amino group functionalized showed superior sensitivity at the formaldehyde concentration as low as 20 ppb. The optimal operation temperature for the sensor was found to be 22 °C, which is advantageous for real applications. The sensors sensitivity deteriorated with the increase of sensing layers thickness. The sensor with the sensing layer thickness of 8.1 μm was demonstrated to possess the optimal combination of sensitivity and reproducibility. The mechanisms by which the sensors sensitivity depended on the amount of amino group functionalized, sensitive layers thickness, operating temperature, and humidity were discussed.

Highly efficient triazine/carbazole-based host material for green phosphorescent organic light-emitting diodes with low efficiency roll-off

Two novel host materials, 3-(dibenzo[b,d]furan-4-yl)-9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazole (BFTC) and 3-(dibenzo[b,d]thiophen-4-yl)-9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazole (BTTC) were designed and synthesized. These two compounds exhibited excellent physical properties with high thermal stabilities and reasonable HOMO–LUMO energy levels. Both of them were applied to fabricate green phosphorescent organic light emitting devices (PhOLEDs) as host materials, and the BTTC based device demonstrated outstanding electroluminescence performance with a maximum current efficiency, maximum power efficiency and external quantum efficiency of 69.3 cd A−1, 54.2 lm W−1 and 21.9%, respectively, suggesting that BTTC is a promising host for green PhOLEDs.

Two novel phenanthrene-based host materials in red and green organic light-emitting devices with low efficiency roll-off

Two new organic small molecules composed of phenanthrene, carbazole and an electron deficient moiety were synthesized by a Suzuki coupling reaction. It is particularly intriguing to compare the electroluminescent (EL) properties of PBBM and PBTZ, which have the same molecular structure with the respective high Td at around 436 °C and 423 °C. By changing the electron deficient moiety of the C9-position of phenanthrene, the photophysical, electrochemical and electroluminescent properties of these two compounds showed significant differences. Furthermore, green and red phosphorescent organic light emitting diodes (OLEDs) employing PBBM and PBTZ as host materials exhibited low efficiency roll-off, and the red OLEDs based on both compounds revealed better EL performance than those of the green OLEDs. Especially, the PBBM-hosted green and red OLEDs achieved a maximum EQE of 14.3% and 18.2%, respectively.