*
Corresponding authors
a
Departamento de Química Física, Universidade de Vigo, Vigo, Spain
E-mail:
ramon.alvarez@ctqc.org, ramon.alvarez@urv.cat
b
Departamento de Ingenieria Electronica, Universitat Rovira i Virgili, Avda. Països Catalans 26, 43007 Tarragona, Spain
c
Centro de Tecnologia Quimica de Cataluña, Carrer de Marcel lí Domingo s/n, 43007 Tarragona, Spain
d
Department of Physics, Imperial College London, London SW7 2AZ, UK
e
Bionanoplasmonics Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia –San Sebastián, Spain
f
Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
g
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA
E-mail:
alexwei@purdue.edu
h
ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain