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 π–π 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 π–π 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.