Study On Micro-Nano Functional Materials For Flexible PH/H₂S Sensors

Miniaturized,low cost and portative chem-sensors are demanded for intelligent packages and wearable electronics.Among different analytic sources,pH and H₂S are commonly required analytes in biomedical and food safety environments.In this study,we are focused on flexible-enabled nanoscale porous inorganic semiconductor materials and their composites for low cost ionic sensors for pH and H₂S gas detections.The main results obtained during the research are as follows:In terms of pH sensitive films:porous titanium dioxide（Ti O₂）was prepared by template calcination.In the temperature range of 250℃-350℃,with the full removal of template agent polyvinylpyrrolidone（PVP）,its pH sensitivity gradually strengthened,while at 400℃,its pH sensitivity decreased due to higher temperature;And properly increasing the PVP content within the experimental range can improve the porosity of titanium dioxide,increase the number of hydrogen ion active sites and enhance the pH sensitivity.Through silane coupling agent KH550 and chemical post-treatment,the pH sensitivity of amino group and carboxyl group on porous titanium dioxide film was improved by 34.21%and 51.41%respectively,indicating that the sensitivity of carboxyl group to hydrogen ion is better than amino group and amino group is better than hydroxyl group;The surface of titanium dioxide is modified with amino and carboxyl groups.The improvement of pH sensitivity is better than that of porous titanium dioxide with many active sites.Nano"Hydrangea"zinc oxide（ZnO）was synthesized by one-step hydrothermal method.By adjusting the reaction temperature,reaction time and the molar ratio of Zn²⁺:OH^-,zinc"hydrangea"films with different micro morphologies were obtained on the surface of silver electrode layer.A flexible extended gate FET pH sensor based on zinc oxide"Hydrangea"was designed and prepared.The zinc oxide film composed of slender was obtained,which showed excellent sensitivity to pH,up to 16.349μA/pH,while the film composed of coarse and short zinc oxide showed poor pH sensitivity as low as 5.607μA/pH.The source leakage current shows a high linearity to pH,which can be used as a pH sensitive thin film electrode to prepare a flexible pH sensor.For flexible hydrogen sulfide gas sensor,copper oxide（CuO）nanoparticles with a diameter of about 100nm,polyaniline（PANI）nanofibers and polyaniline/copper oxide composites were prepared by solution methods.The length of polyaniline fibers was 200 nm to 7μm.The PANI/CuO was compounded in the form of CuO nanoparticles attached to PANI fibers.The flexible carbon interdigital electrodes were prepared by screen printing.The PANI/CuO slurry was coated on the electrodes by drop coating.Four types flexible hydrogen sulfide gas sensors were prepared.The sensing performance test system with good sealing was built.The device was tested for responsiveness,selectivity and flexibility.The prepared P-1 device showed 55%response and 2.16 sensitivity at room temperature with H₂S concentration of 25 ppm;The prepared P-2 device showed 188%response with 7.25 sensitivity at room temperature for 25ppm concentration of H₂S;The device based on CuO material shows linearity and poor performance in the low concentration range（6ppm）;The device based on PANI material shows20%response and 0.98 sensitivity at 22 ppm concentration of H₂S.Explore the gain and loss of semiconductor sensitive devices according to the theory of semiconductor response.