Acrylamide molecule detection by surface-enhanced infrared absorption spectroscopy using resonant nanoantennas

Acrylamide is a cancer-causing substance that forms in food by Maillard reaction when free asparagine (an amino acid) and sugars, both naturally present, undergo high-temperature processing (>120 °C) and low humidity conditions. The European Food Safety Authority (EFSA) has identified acrylamide as a significant contaminant that needs to be monitored and minimized in certain food products. This work reports the first step to detect the presence of acrylamide in aqueous solution by Surface-Enhanced Infrared Absorption (SEIRA) spectroscopy. This work applies Density Functional Theory (DFT) to calculate the vibrational frequencies and infrared (IR) absorption cross-sections of molecular acrylamide in close proximity to gold nanoantenna arrays in water-based solutions. These IR nanoantennas are designed through electromagnetic calculations of their electromagnetic response by tunning their plasmon resonance to match the characteristic vibrational frequencies of acrylamide, enhancing the molecular spectroscopic signal. Comprehensive characterization of the SEIRA signal for various gold nanorod antennas (AuNRA) coupled with a covering shell containing molecular acrylamide enables direct identification of its vibrational modes. This work shows how concentrations of up to 500 ng/ml of acrylamide in water can be detected by SEIRA. It also provides guidelines to apply SEIRA for the detection of acrylamide in challenging samples, such as those typically found in the food industry.