title: Effect of metal-liquid interface composition on the adsorption of a cyanine dye onto gold nanoparticles.
abstract: Synthesis of asymmetric nanoparticles, such as gold nanorods, with tunable optical properties providing metal structures with improved SERS performance is playing a critical role in expanding the use of SERS to imaging and sensing applications. However, the synthetic methods usually require surfactants or polymers as shape-directing agents. These chemicals normally remain firmly bound to the metal after the synthesis, preventing the direct adsorption of a large number of potential analytes and often hampering the chemical functionalization of the surface unless extended, and critical for the nanoparticle stability, postremoval steps were performed. For this reason, it is of great importance for the full exploitation of these nanostructures to gain a deeper insight into the dependence of the analyte-metal interaction to the metal-liquid interface composition. In this article, we investigated in detail the role played by each component of the gold nanorod (GNR) interface in the adsorption of indocyanine green (ICG) as a probe molecule. Citrate-reduced gold nanospheres were used as a model substrate since the negative citrate anions adsorbed onto the metal surface can be easily displaced by those chemicals usually involved in the GNR synthesis, allowing the GNR-like interface composition to be progressively rebuilt and modified at will on the citrate-capped nanoparticles. The obtained results provide a meticulous description of the role played by each individual component of the metal-liquid interface on the ICG interaction with the metal, illustrating how apparently minor experimental changes can dramatically modify the affinity and optical properties of the ICG probe adsorbed onto the nanoparticle.
authors.affiliation: Centro Tecnológico de la Química de Catalunya, 43007 Tarragona, Spain. luca.guerrini@ctqc.org
authors.forename: Luca
authors.initials: L
authors.lastname: Guerrini
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Jurasekova
authors.forename: Elena
authors.initials: E
authors.lastname: del Puerto
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Hartsuiker
authors.forename: Concepcion
authors.initials: C
authors.lastname: Domingo
authors.forename: Jose Vicente
authors.initials: JV
authors.lastname: Garcia-Ramos
authors.forename: Cees
authors.initials: C
authors.lastname: Otto
authors.forename: Santiago
authors.initials: S
authors.lastname: Sanchez-Cortes
mesh_terms: D000327:Adsorption; D019343:Citric Acid / Q000737:chemistry; D003952:Diagnostic Imaging; D006046:Gold / Q000737:chemistry*; D007208:Indocyanine Green / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D043942:Nanotubes / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D020349:Surface Plasmon Resonance; D013499:Surface Properties
chemical_list: D019343:Citric Acid; D006046:Gold; D007208:Indocyanine Green