Abstract
Robust electrolyte-gated organic field-effect-transistors (OFETs) are particularly needed for the development of biosensing devices. However, when a FET biosensor operates in aqueous environments or even in real biological fluids, some critical issues may arise due to the possible lack of environmental long-term and/or operational stability. An important source of instability is associated with the degradation of the organic electronic channel materials such as for instance, poly-3-hexylthiophene (P3HT), a benchmark commercially available p-type organic semiconductor. In this work, the investigation of critical parameters, such as the control over spurious electrochemical phenomena as well as the operating conditions that can affect water-gated OFETs lifetime, is reported, together with a proposed modeling of the P3HT stability curve over 1 week in water. The investigation of possible morphological/chemical modifications occurring at the polymer surface after operating in water for 2 weeks was carried out. Moreover, it is proven how the addition of a gel layer can extend the P3HT based water-gated OFET shelf life up to 2 months.
Highlights
The use of organic field-effect-transistors (OFETs) as sensors (Torsi et al, 2013; Li et al, 2018; Surya et al, 2019) has received a tremendous boost in the last decades thanks to the advent of low-cost fabrication strategies as well as of flexible and/or stretchable substrates (Kim et al, 2013; Manoli et al, 2015)
The direct contact between the organic semiconductor (OS) layer and the aqueous environment rises concerns about the already investigated degradation induced in such polymers by electrochemical processes that occur in water, that are detrimental leading to unstable EGOFETs on prolonged use (Cramer et al, 2013; Bellani et al, 2014; Porrazzo et al, 2014)
P3HT organic semiconductor has been typically successfully used by our group as active channel in FET biosensors with different architectures (Angione et al, 2012; Magliulo et al, 2013; Macchia et al, 2016)
Summary
The use of organic field-effect-transistors (OFETs) as sensors (Torsi et al, 2013; Li et al, 2018; Surya et al, 2019) has received a tremendous boost in the last decades thanks to the advent of low-cost fabrication strategies as well as of flexible and/or stretchable substrates (Kim et al, 2013; Manoli et al, 2015). When water serves as electrolyte, the EDL capacitance is remarkably high, being in the order of few μF∗cm−2 (Cramer et al, 2013) In such an architecture, the direct contact between the organic semiconductor (OS) layer and the aqueous environment rises concerns about the already investigated degradation induced in such polymers by electrochemical processes that occur in water (de Leeuw et al, 1997; Sharma et al, 2010; Bobbert et al, 2012), that are detrimental leading to unstable EGOFETs on prolonged use (Cramer et al, 2013; Bellani et al, 2014; Porrazzo et al, 2014). Additional morphological and spectroscopic characterizations performed on as-prepared and used devices provided information about the response of P3HT film to water contact on a long time scale (2 weeks)
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