Real-Time Detection of Sub-ppm Aromatic Compounds in Alcohol by Surface Plasmon Resonance Using Label-Free Graphene

The increasing importance of high-purity isopropyl alcohol (IPA) in semiconductor processing technology has led to a higher demand for technologies capable of detecting impurities in IPA. Although accurate and various impurity detection technologies have been developed, most of them have limitations in real-time and repeatable detection of impurities. Herein, for the first time, surface plasmon resonance (SPR) sensor was developed utilizing graphene transferred Au film (Au/graphene) to detect sub-ppm levels of 2,4-dinitrophenol (2,4-DNP) dissolved in IPA and this sensor demonstrates the ability to detect 2,4-DNP in real-time with great reversibility. The adsorption of 2,4-DNP to graphene is found to be stronger than that for Au film because of noncovalent graphene pi-pi stacking interaction, and the effect of graphene is demonstrated through density function theory (DFT) calculations and enhancement in sensing performance of Au/graphene sensor. Additionally, the presence of noncovalent pi-pi stacking interaction between 2,4-DNP and graphene has been demonstrated by confirming the p-doping effect of graphene-based solution field-effect transistor measurements and consecutive Raman spectra analysis. This study offers experimental and theoretical insights into the adsorption kinetics of 2,4-DNP dissolved in IPA and provides promising perspectives for real-time sensing technology utilizing label-free graphene to detect impurities in high-purity cleaning agents.