Abstract
Abstract We report on the irradiation of gold rod–sphere assemblies with ultrashort laser pulses, producing structures that are very difficult to obtain by other methods. The optical response of these assemblies displays several peaks arising from the interaction of the plasmon modes of the individual particles, offering thus great flexibility to control the energy deposited on the individual particles. Judicious selection of the wavelength and fluence of the laser pulses allow fine control over the changes produced: the particles can be melted, welded and/or the organic links cleaved. In this way, it is possible to generate structures “à la carte” with a degree of control unmatched by other synthetic protocols. The method is exemplified with gold nanoparticles, but it can be easily implemented on particles composed of different metals, widening considerably the range of possibilities. The final structures are excellent candidates for surface-enhanced spectroscopies or plasmonic photothermal therapy as they have a very intense electric field located outside the structure, not in the gaps.
Highlights
Germany. https://orcid.org/0000-0002-7329-0550 Munish Chanana, Department of Chemistry II, University of Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany; and Swiss Wood Solutions AG, Überlandstr. 129, CH-8600, Dübendorf, Switzerland David Garoz, IMDEA Materials – Madrid Institute for Advanced Studies of Materials, c/Eric Kandel, 2, Parque Cientíco y Tecnológico| Tecnogetafe, 28906, Getafe, Madrid, Spain Luis Bañares, Departamento de Química Física, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040, Madrid, Spain; and Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanoscience), Cantoblanco, 28049, Madrid, Spain that are very difficult to obtain by other methods
Electromagnetic waves can excite the free electrons of metal nanoparticles, inducing a phenomenon known as localized surface plasmon resonance (LSPR) [1,2,3,4]
The aggregation of satellite particles produces a redshift of the LSPR band, accompanied by widening and a significant intensity drop
Summary
Electromagnetic waves can excite the free electrons of metal nanoparticles, inducing a phenomenon known as localized surface plasmon resonance (LSPR) [1,2,3,4]. Judicious selection of the wavelength and fluence of the laser pulses allow fine control over the changes produced: the particles can be melted, welded and/or the organic links cleaved. The observed plasmon widening and weakening is the result of a large number of possible combinations to form assemblies, each with an LSPR maximum located at a slightly different wavelength.
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