A SERS method with attomolar sensitivity: a case study with the flavonoid catechin.

Making good use of interactions between analyte molecules and the metal nanoparticles is key to impact the detection limit in a surface-enhanced Raman scattering (SERS) based detections. SERS was applied to the analysis of catechin and it was found that the relative abundance of catechin in the sample to citrate-capped AgNPs and the aggregation agent NaCl plays a critical role in the quality of detection. At a component volume ratio of 6:2:1 (catechin:AgNPs:NaCl), catechin can be detected at µM levels. When the ratio is 12:2:1, Raman signals are discernible even at the attomolar concentration level (10-18 M). Under these conditions, the SERS mechanisms and the force of laser tweezers function best. The extent of signal enhancement enabled an ultrasensitive and reproducible Raman spectroscopic determination of catechin. Graphical abstract At a component volume ratio of 6:2:1 (catechin:AgNPs:NaCl), catechin was detected at 10-3 M to 10-6 M. When the ratio was 12:2:1, the discernible concentration of catechin was found to reach the attomolar level (10-18 M).