Controlled Preparation And Gas Sensing Properties Of Porphyrin And Perylene Imide Materials

Porphyrin with special two-dimensional conjugated?electronic structure,which is conducive to the charge delocalization in the plane,exhibit excellent optical properties and good physical and chemical stability,so porphyrin is widely used in the field of solar cells,nonlinear optics,photocatalysts,gas sensors and biomedical etc.In addition,due to the highly ordered molecular arrangement,nano or micromaterials can greatly improve the migration rate of charge carriers,which caused great interest of researchers in terms of the photoconductor,molecular devices and electroluminescent.Therefore,the morphology of controllable self-assembly porphyrin has important application value.Perylene tetracarboxylic acid diimide?PDI?compounds,as planar,rigid and conjugated dense ring macromolecules,with excellent photochemical stability,strong fluorescence and unique photoelectric properties,are widely used in the field of dye,solar conversion.At the same time,depending on the intermolecular interaction?hydrogen bond and?-?interaction?,Perylene imide compounds can be self-assembled into highly ordered nano/micron aggregates to broaden its application fields?such as gas sensors,etc.?.In this paper,novel planar conjugated porphyrin/perylene imide compounds were designed and synthesized,and it was self-assembled into nano/micromaterials with different morphologies to explore the relationship between different molecular structures and electrical as well as gas sensing properties.Our work has mainly focused on the following three areas:1.Morphology-controlled self-assembled microstructures of nickel porphyrin with low-power gas sensor toward ethanolA novel symmetrical[5,15-diphenylporphyrinato]nickel????DPPNi??1?was designed and synthesized.For comparative studies,the symmetrical[5,15-bis?ferrocenylethynyl?-10,20-diphenylporphyrinato]nickel????FcDPPNi??2?was also synthesized.Solution-vapor annealing of drop-casting thin films of compounds 1and 2 deposited on SiO₂ substrate or interdigital electrode leads to the formation of well-defined self-assemblies.Intermolecular?-?interaction in cooperation with the solvent-solute interaction leads to the formation of micro-sheets and micro-flowers for compounds 1 and 2 in dichloromethane vapor.When applied as gas sensors,both the micro-sheets and micro-flowers exhibited excellent gas sensitivity,good stability and selectivity for ethanol.Under the same measurement conditions,the micro-flowers gas sensors revealed lower detection limit and faster recovery times than those for micro-sheets gas sensors,which indicated the effect of the molecular packing mode on tuning the gas sensing performance of organic semiconductors.The results represented the first example of single-component nickel oporphyrin micro-structures for ethanol sensitivity.Meanwhile,this paper provided a convenient,low cost method for the mass production of gas sensors.2.Highly ordered sandwich-type?phthalocyaninato??porphyrinato?europium double-deckernanotubes and room temperature NO₂ sensitive propertiesA sandwich-type?phthalocyaninato??porphyrinato?europium double-decker complexEu?TPyP?{Pc-(OC₈H₁₇)₈}[TPyP=meso-tetra?4-pyridyl?porphyrin;Pc-(OC₈H₁₇)₈=2,3,9,10,16,17,23,24-octakis?octyloxy?phthalocyanine]?2?was designed and prepared.For comparative studies,Eu?TPyP??Pc??1?was also prepared.Highly ordered nanotubes of complexes 1 and 2 were successfully fabricated by using an anodized alumina oxide?AAO?template method.Both nanotubes of complexes 1and 2 showed good conductivities and presented an efficient gas sensing platform for the ultrasensitive detection of NO₂ at room temperature.In particular,the detection limit and response/recovery times for the proposed sensors based on complex 2 were lower and faster than those of complex 1,indicating the significant effect of a molecular packing mode on tuning the gas sensing performance of organic semiconductors.3.Enhanced low-power?high-performance trimethylamine gas sensor based n-n heterojuction micro-materials of HH-PDI/CdSA self-assembled microstructures of an amphiphilic perylene tetracarboxylic diimidederivative[1,6,7,12-Tetra-ChlorinatedPerylene-N-?2-hydroxyethyl?-N?-hexylamine-3,4,9,10-tetracarboxylic bisimide,HH-PDI]has been used as the organic component to produce the first example of microbelts of HH-PDI/CdS hybrid materials.The HH-PDI/CdS microbelts exhibited higher conductivity than that of the HH-PDI microrods,which presented an efficient gas sensing platform for the ultrasensitive detection of trimethylamine?TMA?at room operating temperature.In particular,the HH-PDI/CdS microbelts sensor showed faster recovery characteristics and better stability at room operating temperature.Furthermore,the HH-PDI/CdS microbelts sensor revealed significantly improved sensing performance towards ppb-level TMA with ultra-low theoretical detection limit?up to 330 ppb?,which showed considerable potential in the identification of on-site fish freshness.The present result provides an efficient way to improve the gas sensing performance of organic-inorganic hybrid microstructures due to the presence of n-n heterojunctions.