Surface-enhanced Raman detection of biomolecules with silver nanocubes and porous silver nanocubes

Surface enhanced Raman spectroscopy (SERS) has been proposed for detection and analysis of biomolecules at low concentration. A common approach of SERS detection of biomolecules is mainly based on inducing the formation of aggregates of plasmonic nanoparticles in solution, which can lead to the generation of effective hot-spots with a random distribution. However, an irregular arrangement as well as a high variability in the SERS response of these hot-spots are frequently responsible for scarce signal reproducibility. Moreover, uncontrolled clustering of plasmonic nanoparticles can produce high photoinstability, inducing photothermal and photodegradation processes and affecting the Raman signal. Here, we describe a novel strategy to detect intense, stable and reproducible SERS signals from biomolecules in physiological buffer by using isolated silver nanocubes [1] as well as porous Ag/Au nanocubes obtained by galvanic replacement. A theoretical simulation based on the Finite Element Method (FEM) was performed to estimate the E-field distribution on the surface of both substrates. SERS spectra of model biomolecules were achieved and the impact on their structure caused by the excitation of the nanoparticles was evaluated. Using this type of nanoparticles, we were able to measure SERS spectra in physiological buffer with a limit of detection in the nanomolar range.