title: Femtosecond Laser-Controlled Tip-to-Tip Assembly and Welding of Gold Nanorods.
abstract: Directed assembly of gold nanorods through the use of dithiolated molecular linkers is one of the most efficient methodologies for the morphologically controlled tip-to-tip assembly of this type of anisotropic nanocrystals. However, in a direct analogy to molecular polymerization synthesis, this process is characterized by difficulties in chain-growth control over nanoparticle oligomers. In particular, it is nearly impossible to favor the formation of one type of oligomer, making the methodology hard to use for actual applications in nanoplasmonics. We propose here a light-controlled synthetic procedure that allows obtaining selected plasmonic oligomers in high yield and with reaction times in the scale of minutes by irradiation with low fluence near-infrared (NIR) femtosecond laser pulses. Selective inhibition of the formation of gold nanorod n-mers (trimers) with a longitudinal localized surface plasmon in resonance with a 800 nm Ti:sapphire laser, allowed efficient trapping of the (n - 1)-mers (dimers) by hot spot mediated photothermal decomposition of the interparticle molecular linkers. Laser irradiation at higher energies produced near-field enhancement at the interparticle gaps, which is large enough to melt gold nanorod tips, offering a new pathway toward tip-to-tip welding of gold nanorod oligomers with a plasmonic response at the NIR. Thorough optical and electron microscopy characterization indicates that plasmonic oligomers can be selectively trapped and welded, which has been analyzed in terms of a model that predicts with reasonable accuracy the relative concentrations of the main plasmonic species.
authors.affiliation: Departamento de Química Física I, Universidad Complutense de Madrid , Avda. Complutense s/n, 28040, Madrid, Spain.|BioNanoPlasmonics Laboratory, CIC biomaGUNE , Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain.
authors.forename: Guillermo
authors.initials: G
authors.lastname: González-Rubio
authors.affiliation: Departamento de Química Física I, Universidad Complutense de Madrid , Avda. Complutense s/n, 28040, Madrid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: González-Izquierdo
authors.affiliation: Departamento de Química Física I, Universidad Complutense de Madrid , Avda. Complutense s/n, 28040, Madrid, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Bañares
authors.affiliation: Departamento de Química Física I, Universidad Complutense de Madrid , Avda. Complutense s/n, 28040, Madrid, Spain.
authors.forename: Gloria
authors.initials: G
authors.lastname: Tardajos
authors.affiliation: Instituto de Fusión Nuclear, Universidad Politécnica de Madrid , José Gutiérrez Abascal 2, E-28006 Madrid, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Rivera
authors.affiliation: EMAT-University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Altantzis
authors.affiliation: EMAT-University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Sara
authors.initials: S
authors.lastname: Bals
authors.affiliation: Instituto de Fusión Nuclear, Universidad Politécnica de Madrid , José Gutiérrez Abascal 2, E-28006 Madrid, Spain.
authors.forename: Ovidio
authors.initials: O
authors.lastname: Peña-Rodríguez
authors.affiliation: Departamento de Química Física I, Universidad Complutense de Madrid , Avda. Complutense s/n, 28040, Madrid, Spain.
authors.forename: Andrés
authors.initials: A
authors.lastname: Guerrero-Martínez
authors.affiliation: BioNanoPlasmonics Laboratory, CIC biomaGUNE , Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain.|Ikerbasque, Basque Foundation for Science , 48013 Bilbao, Spain.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Liz-Marzán
keywords: Gold nanorod; dimer; femtosecond laser; nanoparticle assembly; welded nanoparticles