Gold-Nanorod-Based Plasmonic Nose for Analysis of Chemical Mixtures

We introduce the "plasmonic nose" as a novel approach for detection, recognition, and quantification of mixtures of chemical species. Using a paper substrate and a calligraphy-based fabrication approach, we generated an array of surface-enhanced Raman scattering (SERS)-active sensors with distinct chemical functionalities. Each sensor is composed of gold nanorods (AuNRs) functionalized with a macromolecule that determined its sensitivity and specificity. We show that the SERS-active sensor array is capable of detecting and discriminating a wide variety of chemical species. To validate this approach, we exposed the sensor array to individual analytes and their binary/ternary mixtures. We found that each mixture generated a multivariate fingerprint that varied with identity (vibrational frequency) and intensity. Statistical analysis of SERS spectra from multiple sensors allowed us to not only recognize components of mixtures but also estimate their mixing ratios. In sum, our study presents a highly practical, low-cost sensing approach for quantitative chemical analyte detection for a wide variety of applications including life sciences, environmental monitoring, and homeland security.