Self‐Assembled Polyamidoamine Dendrimer on Poly (methyl meth‐ acrylate) for Plasmonic Fiber Optic Sensors

We report a novel one‐step polyamidoamine (PAMAM) dendrimer based polymethyl methacrylate (PMMA) surface functionalization strategy for the development of polymeric optical fiber (POF) based plasmonic sensors utilizing gold nanoparticles (AuNP). Simple contact angle measurements over PMMA sheets reveal the ability of the dendrimers to strongly bind to PMMA surface without additional acid/alkali pretreatment, unlike the conventional hexamethylene diamine (HMDA) based surface modification. Subsequently, U‐bent POF probes with high evanescent wave absorbance sensitivity were exploited for relative quantification of the surface amine groups using fluorescein isothiocyanate (FITC) binding and efficient chemisorption of gold nanoparticles (AuNP) in order to identify the optimum conditions viz. dendrimer concentration, incubation time and dendrimer generation. While FITC binding showed a proportional increase in amine functional density with PAMAM concentration and time, interestingly the AuNP (40 nm) binding studies revealed the formation of loose PAMAM multilayers and their desorption. PAMAM (G4) concentration as low as 5 mM and incubation time of 24 h provide faster binding rate with densely packed AuNP and the RI sensitivity of ∼15 (A546 nm/RIU). This simpler and inexpensive strategy could also be exploited for the development of functional PMMA substrates for various applications including nanotechnology, bio‐imaging, drug delivery and analytical separations. Plasmonic PMMA surfaces: A novel one‐step PMMA surface modification strategy using G4 PAMAM dendrimer is established and optimized by efficiently exploiting the evanescent wave absorbance response of polymeric optical fiber sensor probes to binding of fluorescein molecules and gold nanoparticles. This is exploited to realize highly sensitive plasmonic fiber optic sensors.