Pico-Molar Sensing of Reactive Oxygen Species Using Organic Field-Effect Transistors with Conjugated Polymer Layers Containing Quercetin Clusters

Abstract

Facile detection of reactive oxygen species (ROS) is crucial for early-stage diagnosis and disease prediction, including cancer. Here, it is demonstrated that quercetin (QCT), a naturally derived polyphenol, forms nanoscale aggregates (clusters) within the matrix of the conjugated polymer, poly(3-hexylthiophene) (P3HT), and acts as a key material for sensing ROS in organic field-effect transistors (OFETs). To investigate the influence of QCT loading, the QCT content was varied from 0 to 70 wt % in the 50 nm-thick P3HT:QCT sensing channel layers for OFETs. Morphological analysis revealed that submicron-size QCT aggregates (up to ∼600 nm) were formed in the P3HT:QCT films. The basic transistor test showed that the best performance could be achieved at QCT = 30 wt % (abbreviated as QCT30-OFET). In the perfusion test that enables steady-state flow of ROS solutions, QCT30-OFETs could detect a wide range of ROS concentrations from 20 pM to 1 mM. The QCT30-OFETs were able to detect ROS systematically even under consecutive repeated injections of ROS solutions. A simple drop test demonstrated that droplets of ROS solutions could be easily detected by the present QCT30-OFET sensors, supporting the effectiveness and practicability of the QCT-based ROS sensing concept.