Nanometal Skin of Plasmonic Heterostructures for Highly Efficient Near-Field Scattering Probes

Year: 2016

Authors: Zito G., Rusciano G., Vecchione A., Pesce G., Di Girolamo R., Malafronte A., Sasso A.

Autors Affiliation: University of Naples Federico II, Dept. of Physics E. Pancini, via Cintia 80126-I, Naples, Italy; Istituto Nazionale di
Ottica (INO) Consiglio Nazionale delle Ricerche, via Campi Flegrei 34 – 80078 Pozzuoli, Italy; Istituto SPIN U.O.S.
Consiglio Nazionale delle Ricerche, via Giovanni Paolo II 132, 84084, Fisciano, Italy; University of Salerno, Dept. of
Physics, via Giovanni Paolo II 132, 84084, Fisciano, Italy; University of Naples Federico II, Dept. of Chemical Sciences, via Cintia 80126-I, Napoli, Italy.

Abstract: In this work, atomic force microscopy probes are functionalized by virtue of self-assembling monolayers of block copolymer (BCP) micelles loaded either with clusters of silver nanoparticles or bimetallic heterostructures consisting of mixed species of silver and gold nanoparticles. The resulting self-organized patterns allow coating the tips with a sort of nanometal skin made of geometrically confined nanoislands. This approach favors the reproducible engineering and tuning of the plasmonic properties of the resulting structured tip by varying the nanometal loading of the micelles. The newly conceived tips are applied for experiments of tip-enhanced Raman scattering (TERS) spectroscopy and scatteringtype scanning near-field optical microscopy (s-SNOM). TERS and s-SNOM probe characterizations on several standard Raman analytes and patterned nanostructures demonstrate excellent enhancement factor with the possibility of fast scanning and spatial resolution <12 nm. In fact, each metal nanoisland consists of a multiscale heterostructure that favors large scattering and near-field amplification. Then, we verify the tips to allow challenging nongap-TER spectroscopy on thick biosamples. Our approach introduces a synergistic chemical functionalization of the tips for versatile inclusion and delivery of plasmonic nanoparticles at the tip apex, which may promote the tuning of the plasmonic properties, a large enhancement, and the possibility of adding new degrees of freedom for tip functionalization. Journal/Review: SCIENTIFIC REPORTS

Volume: 6      Pages from: 31113-1  to: 31113-16

More Information: The financial support leading to these results was from Italian Ministry of Education, University and Research (MIUR), Grant No. FIRB 2012-RBFR12WAPY; in part from MIUR, Grant No. PON01 01525, Project: MONICA; and from University of Naples Federico II, Compagnia di San Paolo e Istituto Banco di Napoli – Fondazione, STAR Project: LARA. We are grateful to Dr. L. Petti (ISASI, CNR, Italy) for the electron-beam lithographic samples provided.
KeyWords: enhanced Raman spectroscopy; nanoscale chemical-analysis; optical microscopy; single-molecule; infrared nanospectroscopy; TIP; nanoparticles; resolution; quantum; sers
DOI: 10.1038/srep31113

Citations: 16
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