Breaking the diffusion limit with super-hydrophobic delivery of molecules to plasmonic nanofocusing SERS structures

• Published in: Nature photonics Vol. 5; no. 11; pp. 682 - 687
• Main Authors: De Angelis, F., Gentile, F., Mecarini, F., Das, G., Moretti, M., Candeloro, P., Coluccio, M. L., Cojoc, G., Accardo, A., Liberale, C., Zaccaria, R. P., Perozziello, G., Tirinato, L., Toma, A., Cuda, G., Cingolani, R., Di Fabrizio, E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2011; Nature Publishing Group
• Subjects: 639/624/1107/527/1821; 639/624/400/1021; 639/766/400; Applied and Technical Physics; Contact angle; Dangerous; Detection times; Diffusion; Hydrophobic surfaces; Investigations; Miniaturization; Nanocomposites; Nanomaterials; Nanostructure; Photonics; Physics; Physics and Astronomy; Plasmonics; Quantum Physics; Sensors; Signatures; Spectrum analysis; Italy
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2011.222

The detection of a few molecules in a highly diluted solution is of paramount interest in fields including biomedicine, safety and eco-pollution in relation to rare and dangerous chemicals. Nanosensors based on plasmonics are promising devices in this regard, in that they combine the features of high sensitivity, label-free detection and miniaturization. However, plasmonic-based nanosensors, in common with general sensors with sensitive areas on the scale of nanometres, cannot be used directly to detect molecules dissolved in femto- or attomolar solutions. In other words, they are diffusion-limited and their detection times become impractical at such concentrations. In this Article, we demonstrate, by combining super-hydrophobic artificial surfaces and nanoplasmonic structures, that few molecules can be localized and detected even at attomolar (10 −18  mol l −1 ) concentration. Moreover, the detection can be combined with fluorescence and Raman spectroscopy, such that the chemical signature of the molecules can be clearly determined. Surface-enhanced Raman sensors often rely on random chance for molecules to come near optical hotspots. Here, researchers use super-hydrophobic artificial surfaces and evaporation to direct molecules to plasmonic light-focusing structures. Molecules can be localized and detected even at attomolar concentrations.