Integrating plasmonic supercrystals in microfluidics for ultrasensitive, label free and selective SERS detection.

SERS microfluidic chips for label-free and utrasensitive detection are fabricated by integrating a plasmonic supercrystal within microfluidic channels. This plasmonic platform allows the uniform infiltration of the analytes within the supercrystal reaching the so-called hot spots. Moreover, state of the art simulations performed using large-scale supercrystal models demonstrate that the excellent SERS response are due to the hierarchical nanoparticles organization, the interparticle sepa-ration and the presence of supercrystal defects. Proof of concept experiments confirms the outstanding performance of the microfluidic chips for the ultradetection of (bio)molecules with no metal affinity. In fact, LOD as low as 10-19 M was reached for crystal violet. The SERS microfluidic chips shows excellent sensitivity in the direct analysis of pyocyanin secret-ed by P. aeruginosa grown in a liquid culture medium. Finally, the further integration of a silica-based column in the plas-monic microchip provides charge-selective SERS capabilities as demonstrated for a mixture of positively and negatively charged molecules.