Towards attomolar detection using a surface-enhanced Raman spectroscopy platform fabricated by nanosphere lithography

The limit of detection of 4-nitrothiophenol adsorbed onto the surface of a platform fabricated by nanosphere lithography is investigated by surface-enhanced Raman spectroscopy. Critical factors such as the functionalization time and the change of sharpness of the gold nanostructures upon annealing are studied. Platforms for surface-enhanced Raman spectroscopy provide detection ranging from monolayers down to isolated molecules. For a functionalization time of 24 h, a limit of detection of 10 −16 mol/L (100 amol/L) is achieved. Furthermore, by shortening the functionalization time to 30 min, a significantly higher limit of detection is determined ranging from 10 −6 to 10 −9 mol/L. By altering the shape of the nanotriangles via annealing, a loss in signal intensity occurs. Optimizing the factors that enable a lower limit of detection is critical for many applications where surface-enhanced Raman spectroscopy can be considered as a promising analytical alternative.