Influence of Surfactant Bilayers and Substrate Immobilization on the Refractive Index Sensitivity of Anisotropic Gold Nanoparticles
(English)Manuscript (preprint) (Other academic)
Shape-controlled synthesis of gold nanoparticles generally involves the use of surfactants to regulate the nucleation growth process and to obtain colloidally stable nanoparticles. The surfactants adsorb on the nanoparticle surface making further functionalization difficult and therefore limit their practical use in many applications. Herein, we report on how cetyltrimethylammonium (CTAX, X=Cl-, Br-), a commonly used surfactant in the synthesis of anisotropic gold nanoparticles, influences the nanoparticle sensitivity to respond to local dielectric environment changes which is the basis for refractometric sensing. We show, both experimentally and theoretically, that the CTAX bilayer significantly reduces the refractive index (RI) sensitivity of anisotropic gold nanoparticles such as flat and concave nanocubes, nanorods, and nanoprisms. Additionally, we show that the RI sensitivity can be increased by up to 40% by removing the surfactant layer from nanoparticles immobilized on a solid substrate using oxygen plasma treatment. The substrate effect on the RI sensitivity caused by nanoparticle immobilization is also investigated. The strategy presented herein is a simple yet effective method to increase the RI sensitivity of CTAX-stabilized gold nanoparticles, thus increasing their potential as transducers in nanoplasmonic sensors and in biomedical applications.
IdentifiersURN: urn:nbn:se:liu:diva-111839OAI: oai:DiVA.org:liu-111839DiVA: diva2:760914