Integrating Plasmonic Supercrystals in Microfluidics for Ultrasensitive, Label-Free, and Selective Surface-Enhanced Raman Spectroscopy Detection

• Published in: ACS applied materials & interfaces Vol. 12; no. 41; pp. 46557 - 46564
• Main Authors: García-Lojo, Daniel, Gómez-Graña, Sergio, Martín, Víctor F, Solís, Diego M, Taboada, José M, Pérez-Juste, Jorge, Pastoriza-Santos, Isabel
• Format: Journal Article
• Language: English
• Published: American Chemical Society 14.10.2020
• Subjects: Functional Nanostructured Materials (including low-D carbon); Au nanoparticles; SERS sensing; plasmonic supercrystals; microchromatography; microfluidics
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.0c13940

Surface-enhanced Raman spectroscopy (SERS) microfluidic chips for label-free and ultrasensitive 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 is due to the hierarchical nanoparticle organization, the interparticle separation (IPS), and the presence of supercrystal defects. Proof-of-concept experiments confirm the outstanding performance of the microfluidic chips for the ultradetection of (bio)­molecules with no metal affinity. In fact, a limit of detection (LOD) as low as 10–19 M was reached for crystal violet. The SERS microfluidic chips show excellent sensitivity in the direct analysis of pyocyanin secreted by Pseudomonas aeruginosa grown in a liquid culture medium. Finally, the further integration of a silica-based column in the plasmonic microchip provides charge-selective SERS capabilities as demonstrated for a mixture of positively and negatively charged molecules.