Multifunctional nano probe gas sensing devices using MWCNT/Graphene doped PDVF polymer nanocomposites

In recent years, due to rapid development of industrialization, toxic air pollution has been increased enormously and become a serious global issue. It has been emerged as a big and uncontrollable effect on the eco system. Most of the gases evolved from the industries are toxic, quite unknown and untraced. Thus, it has stimulated the activities in developing gas sensing devices to trace the gaseous element and take the preventive measurement to control the generation of toxic gases and save the environment as well. It is worth noting that solid polymer electrolytes (SPE) has been widely used in sensor manufacturing to detect various industrial gases in the open environment and the marine areas. However, solid polymers activated by various doping agents are particularly new in this area. In aiming to build highly flexible, and low cost gas sensing devices, this project will focus to develop novel polymer (vinylidene fluoride) (PVDF) based nanocomposites. Multiwall carbon nanotube (MWCNT) and/or graphene (GP) will be used as electro-conductive fillers within PVDF polymer matrix. MWCNT and GP will also be functionalized before adding to PVDF polymer to fabricate functionalized nanocomposites. Measuring the change of resistivity of these polymer nanocomposites when in contact with gas molecules, the gas molecules will be easily detected. PVDF has very interesting physical, chemical and high temperature resistance properties. It has also unique ferroelectric semi crystalline properties. Moreover, its high piezo, pyroelectric and physical properties make it more attractive to its use in sensing applications. Different techniques and methodology will be implemented to disperse the MWCNT/GP into the PVDF polymeric. Layered filmed nanostructured with multiple layers of nanocomposites will be sandwiched to make different PVDF nanocomposites. Due to the inherent electrical and mechanical properties of PVDF, minute amount of functionalized MWCNT/GP (known as f-MWCNT/GF) doping will change extremely low percolation threshold and thus the high electrical responses. The activated functional groups on MWCNT/GP will absorb or react with the different gaseous molecules and immediately show responses by the electrical responses measurement. Moreover, PVDF is characterized as multiple phase behaviour which exhibit at least five crystalline phases (). Thus, there are advantages of using PVDF in fabricating electro responsive polymeric nanocomposites. Due to this fantastic property, positive temperature effect can be used in measuring the sensing properties of temperature and the gas as well. In presence of MWCNT/GF, PVDF polymer will also dramatically affect the phase behaviour and thus effect on electrical and gas sensing responses. Functionalizing the MWCNT and or graphene will provide more significant responses on electrical and gas sensation. Some researcher used PMMA, ABS and PANI polymers to fabricate the gas sensors, however they have ended with very low sensitivity, low recovery rate and polymer degradation. As PVDF polymer has very high mechanical, chemical, electrical and low degration responses, selecting PVDF polymer will make the project unique. So far using of PVDF in sensor is not reported. MWCNT has been used with conductive polymer to prepare gas sensors. However they are used only for selective gas sensing. Graphene is a new nano material which has been focused recently. It has zero band gap and semi metal characteristics with single layer unique structure. Thus the detection by absorption of gases on graphene surface will be significant. We will use number of nanocomposite films in one device as shown in Fig 1 to detect various gases and ion. Considering the above facts, we proposed to use PVDF polymer with functionalized MWCNT and GP molecules to fabricate gas sensing device for next generation applications. In this project, PVDF nanocomposites physical and thermos-mechanical properties will be characterized by XRD, TGA, TMA, DMTA, DSC, FTIR, tensile and flexural testing machines. Morphology will be tested using FE-SEM and TEM. Electrical properties will be characterized by broadband dialectical spectrometer and resistance measurement devices. Gas sensing properties of the PVDF nanocomposites will be measured by measuring the DC conductivity electrometer and analysed by DC conductivity vs 1/T(k-1) and frequency. Gas response curve with time and temperature will also be present. Finally, gas sensitivity with response real time and temperature will also be calculated and investigated.