SERS detection of environmental pollutants in humic acid-gold nanoparticle composite materials.

Humic acid (HA) solutions provide an unexpected medium for direct fabrication of gold nanoparticles (HA-AuNP) and a clear window for surface-enhanced Raman scattering (SERS) with many potential applications in the ultrasensitive chemical analysis of environmental pollutants. It is demonstrated that the HA-AuNP fabrication can be easily achieved in a wide range of pH (2 to 12). The background SERS spectra of HA is relatively weak in absolute intensity, allowing the detection of the enhanced Raman signal from trace amount of contaminants. An in-situ approach is illustrated where the HA-AuNP fabrication is carried out with a HA solution containing the target pollutant. The technique may allow for the direct detection of organic pollutants present in the humic fraction of soil.