Preparation Of Three-dimensional Copper Phthalocyanine Films Based On Nanofibers And Its Sensing For No₂ At Room Temperature

For organic field effect transistor(OFETs)gas sensors,conduction channels are usually concentrated in several molecular layers at the bottom of the organic semiconductor(OSCs)layer,close to the interface between the OSCs and the dielectric.Therefore,the traditional gas sensors based on OFETs are affected by the dense and continuous OSCs layer structure,which makes it difficult for the gas analyte to contact and interact with the conduction channel quickly.As a result,the sensing performance usually presents the disadvantages of slow response and difficult recovery,which can not meet the actual demand of low concentration detection.In this paper,the micro/nano structure of OSCs layer was modulated by electrospinning,vacuum evaporation and solution spin coating.By constructing three-dimensional OSCs layer,the specific surface area of OSCs layer was increased,so that the gas analyte can contact with OSCs layer in multiple angles and directions.The modulation of the three-dimensional OSCs layer morphology and the sensor performance are mainly analyzed,which provides a theoretical basis for the preparation of high-performance gas sensors.(1)High performance gas sensors based on evaporated Cu Pc/PVA DNFs filmsCu Pc/PVA DNFs films with three-dimensional structure were prepared by vacuum evaporation of copper phthalocyanine(Cu Pc)molecules on electrospun polyvinyl alcohol(PVA)disordered nanofibers(DNFs)scaffolds.The relative response of the gas sensors to NO₂ gas with concentration of 20 ppm was 12391%.The response time and response time were 3.5 min and 2.5 min,respectively.The recovery rate was 98%,and the baseline drift was very slight.The sensitivity was 829%/ppm.The limit of detection(LOD)was 0.5ppm.Compared with the sensors based on evaporated Cu Pc films,the performance of the sensors was improved obviously.(2)High performance gas sensors based on evaporated Cu Pc/PVA ONFs filmsPVA ordered nanofibers(ONFs)were prepared by using an electrospun receiving plate with clined gap.The micro/nano structure of evaporated Cu Pc films was further modulated by PVA ONFs.The evaporated Cu Pc/PVA ONFs films owned regular three-dimensional structure.The relative response of the sensors to 20 ppm NO₂ gas was952%.The response time and response time were both 0.03 min.The response rate was99.9%.The sensitivity was 37%/ppm.LOD decreased to 0.3 ppm.The gas sensing performance is improved obviously.The response and recovery speed are accelerated,and the recovery rate and LOD are further improved.(3)High performance gas sensors based on electrospun Cu Pc:PMMA NFsIn order to realize the application of phthalocyanine materials in the field of flexible sensing,the electrospinning method of solution treatment was used to prepare the electrospun copper phthalocyanine:polymethylmethacrylate(Cu Pc:PMMA)nanofibers(NFs).The relative response of the sensors to 20 ppm NO₂ gas was 248%.The response time and response time were 5.64 min and 10 min,respectively.The response rate was60%.The sensitivity was 7%/ppm.LOD was 1 ppm.The performance of the sensors is slightly improved.It may be due to the incomplete exposure of the gas sensitive layer due to the inclusion of some Cu Pc materials by PMMA.(4)High performance gas sensors based on spin-coated Cu Pc filmsIn order to improve the performance of phthalocyanine materials in the field of flexible sensing,spin coated Cu Pc films were prepared by solution spin-coating method.The films were filamentous and had cracks.The films with concentration of 75 mg/ml of Cu Pc solution were the most consistent.The relative response of the sensors to 20 ppm NO₂ gas was 32797%.The response time and response time were 4.55 minand 2.97 min,respectively.The recovery rate was 80%.The sensitivity was the highest,1492%/ppm.LOD is 0.3 ppm.(5)High performance gas sensors based on spin-coated Cu Pc/PVA ONFs filmsThe micro/nano structure of spin-coated Cu Pc thin films was modulated by introducing the PVA ONFs.The relative response of the sensors to 20 ppm NO₂ gas was12942%.The response time and response time were 2.6 min and 3.84 min,respectively.The response rate was 90%.The sensitivity was 611%/ppm and LOD was further improved to 0.2 ppm.In a word,by using nanofibers to control the micro/nano structure of Cu Pc gas sensing layer,the performance of gas sensors based on Cu Pc material can be improved in varying degrees.The method is simple,feasible and effective.It provides a valuable reference for the further research and development of gas sensors based on organic semiconductor materials.