Abstracts Book - IMRC 2018

• SA6-O013
OPTICALLY MONODISPERSE GOLD NANOROD COLLOIDS
PRODUCED BY FEMTOSECOND LASER RESHAPING
Ovidio Y. Peña Rodríguez 1 , Guillermo González Rubio 2,3 , Pablo Díaz Núñez 1 , Antonio Rivera 1 ,
Alejandro Prada 1 , Gloria Tardajos 3 , Jesús González Izquierdo 4 , Luis Bañares 3,4 , Pablo Llombart 3 ,
Luis González Macdowell 3 , Mauricio Alcolea Palafox 3 , Luis M. Liz Marzán 2,5 , Andrés Guerrero
Martínez 3
1 Universidad Politécnica de Madrid, Instituto de Fusión Nuclear, Spain. 2 CIC BiomaGUNE,
Bionanoplasmonics Laboratory, Spain. 3 Universidad Complutense de Madrid, Departamento
de Química Física I, Spain. 4 Universidad Complutense de Madrid, Centro de Láseres
Ultrarápidos, Spain. 5 Basque Foundation for Science, Ikerbasque, Spain.
Size and shape polydispersity can be detrimental to the functional properties of
the nanoparticles relative to those of the ideal, single size ensemble but it is
accepted as a general fate in the synthesis of colloidal nanoparticles [1].
Deleterious effects include broadening of optical features, conductivity losses,
and reduction of catalytic or magnetic activity, among others [2]. In particular,
morphological variations have a critical influence on the broadening of the
localized surface plasmon resonance (LSPR) of colloidal metal nanoparticles.
Spectral broadening may the feasibility of technological applications, which in
general require optimal coupling between the LSPR frequency and that of the
light excitation source. Hence, reduction of the LSPR bandwidth has been a key
driving force toward the further progress in gold colloid synthesis. However, we
have shown that irradiation of gold nanorod colloids with a femtosecond laser
can be tuned to induce controlled nanorod reshaping, yielding colloids with
unprecedentedly narrow localized surface plasmon resonance bands [3]. The
process relies on a regime characterized by a gentle multi-shot reduction of the
aspect ratio, whereas the rod shape and volume are barely affected. Successful
reshaping can only occur within a narrow heat dissipation rate window, i.e. low
cooling rates lead to drastic morphological changes and fast cooling has nearly
no effect. Hence, a delicate balance must be achieved between irradiation
fluence and surface density of the surfactant. This perfection process is
appealing because it provides a simple, fast, reproducible and scalable route
toward gold nanorods with an optical response of exceptional quality, near the
theoretical limit.
References
M. P. Pileni, Nanosized particles made in colloidal assemblies, Langmuir 13,
3266–3276 (1997).