Comprehensive Characterization of Solution-Cast Pristine and Reduced Graphene Oxide Composite Polyvinylidene Fluoride Films for Sensory Applications

Abstract

Pristine and doped polyvinylidene fluoride (PVDF) are actively investigated for a broadrange of applications in pressure sensing, energy harvesting, transducers, porous membranes, etc.There have been numerous reports on the improved piezoelectric and electric performance of PVDFdopedreduced graphene oxide (rGO) structures. However, the common in situ doping methodshave proven to be expensive and less desirable. Furthermore, there is a lack of explicit extractionof the compression mode piezoelectric coefficient (d33) in ex situ rGO doped PVDF composite filmsprepared using low-cost, solution-cast processes. In this work, we describe an optimal procedure forpreparing high-quality pristine and nano-composite PVDF films using solution-casting and thermalpoling. We then verify their electromechanical properties by rigorously characterizing b-phaseconcentration, crystallinity, piezoelectric coefficient, dielectric permittivity, and loss tangent. Wealso demonstrate a novel stationary atomic force microscope (AFM) technique designed to reducenon-piezoelectric influences on the extraction of d33 in PVDF films. We then discuss the benefits of ourd33 measurements technique over commercially sourced piezometers and conventional piezoforcemicroscopy (PFM). Characterization outcomes from our in-house synthesized films demonstrate thatthe introduction of 0.3%w.t. rGO nanoparticles in a solution-cast only marginally changes the b-phaseconcentration from 83.7% to 81.7% and decreases the crystallinity from 42.4% to 37.3%, whereasdoping increases the piezoelectric coefficient by 28% from d33 = 45 pm/V to d33 = 58 pm/V, while alsoimproving the dielectric by 28%. The piezoelectric coefficients of our films were generally higher butcomparable to other in situ prepared PVDF/rGO composite films, while the dielectric permittivityand b-phase concentrations were found to be lower.