Fabrication and optical stability from silanized gold nanorods as transducers of near infrared light

We give new insight into multifunctional nanoparticles with light extinction in the therapeutic window, optical stability even on aggregation, as well as possibility of bio-conjugation. The optical response of these particles rests on gold nanorods, which interact with near infrared (NIR) light via plasmonic oscillations, which is an interface effect. Therefore the optical behavior of these particles is challenged by factors which typically occur in the biological sample and under excitation, such as aggregation (e.g. inside endocytic vesicles) and shape transformations. Here silanization of the gold nanorods is proposed as one effective solution to overcome these issues. A shell of porous silica confers isolation from the local environment and additional stability, and also proves suitable for PEGylation and bio-conjugation with e.g. biological macromolecules. We engineer models of aggregation of these particles, in order to investigate its principal effect on their optical response. While in the absence of silica gold nanorods undergo substantial degradation of their plasmonic bands, silanization proves excellent to maintain pristine optical properties even after critical flocculation.