Waterborne conductive carbon paste with an eco-friendly binder

Conductive carbon pastes are widely used in flexible and printed electronic devices such as wearable electronics and optoelectronics. The use of conductive pastes comes with some challenges, such as replacing toxic synthetic materials with environmentally-friendly and sustainable ones, achieving an appropriate level of electrical conductivity, and controlling the thickness of the coated film. Waterborne conductive carbon pastes have been used to tackle the mentioned problems. In this study, carboxymethyl cellulose (CMC) was introduced as an eco-friendly binder combined with Graphene Nanoplatelets (GNPs) and Carbon Nanotubes (CNTs) to synthesize a conductive carbon paste without any metallic elements. The double-coated GNP/CNT/CMC paste films were coated on a paper surface using the doctor blade method. Morphological and thermal characteristics, sheet resistance, and optoelectrical properties of the paste films were comprehensively investigated. It was found that the conductive carbon paste containing 35 wt% CNTs exhibits higher conductivity (80.4 S/m) than the other combinations. Moreover, Field Emission Scanning Electron Microscopy (FE-SEM) showed that GNPs and CNTs are distributed within cellulosic matrix very homogeneously. Great flexibility and high electrical conductivity are achieved in the paste film. EIS results implied that the double-coated paste could act as a highly conductive surface in fabricating electrochemical sensors with high performance. In conclusion, this study represents a novel and environmentally-friendly method to produce low-cost, highly-efficient, and large-scale conductive carbon paste.