Interpretation of Localized Surface Plasmonic Resonances of Gold Nanoparticles Covered by Polymeric Coatings

Abstract

Plasmonic materials currently have a plethora of applications. How would a dielectric matrix, such as diblock copolymers, tune plasmonic properties? In this work, self-assembled gold nanoparticles were fabricated in medium vacuum conditions on heated Corning glass substrates (kept at 440 °C) under the coexistence of argon and air by means of DC magnetron sputtering. These samples were compared structurally and optically to samples deposited at room temperature and post annealed. Subsequently, the better of the two preparations, those deposited on heated glass, were covered with three different polymers, namely: Polystyrene-block-polybutadiene-block-polystyrene (PS-b-PBD-b-PS); Polystyrene-co-methyl methacrylate (PS-co-PMMA); and Polystyrene-block-polyisoprene-block-polystyrene (PS-b-PI-b-PS), by means of spin coating. Localized surface plasmon resonances were recorded and analyzed, respectively, for polymer-covered gold nanoparticles, with the width, intensity, and position of the resonances changing according to multiple factors, such as the nanoparticles size and the refractive index of each polymer. Lastly, for purposes of justification and comparison with the experimental results, rigorous theoretical calculations have been carried out.

Fully Integrated Point-of-Care Platform for the Self-Monitoring of Phenylalanine in Finger-Prick Blood

“…Figure C illustrates the optical absorption spectra of the gold nanostructures with and without agarose-0.4%. A sharp LSPR band at around 532 nm was observed for the gold nanostructures formed in the absence of agarose, whereas a broad and red-shifted LSPR band at around 590 nm was evident in the presence of agarose, as expected for the aggregation of gold nanostructures in polymeric media . Moreover, our experiments indicate that the agarose-0.4% layer improves the efficiency of gold nanostructure formation due to the capping effect of agarose to stabilize the gold nanostructures …”

“…A sharp LSPR band at around 532 nm was observed for the gold nanostructures formed in the absence of agarose, whereas a broad and red-shifted LSPR band at around 590 nm was evident in the presence of agarose, as expected for the aggregation of gold nanostructures in polymeric media. 41 Moreover, our experiments indicate that the agarose-0.4% layer improves the efficiency of gold nanostructure formation due to the capping effect of agarose to stabilize the gold nanostructures. 42 Figure 4 D reports the kinetics for the enzymatic recognition of Phe in the absence (black squares) and presence (red circles) of agarose.…”

Silver Nanoparticles’ Localized Surface Plasmon Resonances Emerged in Polymeric Environments: Theory and Experiment

“…The surface morphology of the uncoated films was studied via atomic force microscopy (AFM). Film and polymer thickness determination was performed using atomic force microscopy (AFM) images showing the profile of a narrow scratch conducted intentionally on the film surface [40,41]. The thickness of polymer films deposited on a Corning glass substrate was measured at 54, 35, and 300 nm for PS-b-PBD-b-PS, PS-co-PMMA, and PS-b-PI-b-PS, respectively.…”

“…Keeping N and M harmonics in Equations ( 2)-( 4), and from the continuity of the tangential electric and magnetic fields at the boundaries z = 0 and z = d, a 4NM system of equations emerges, leading to the solution of Rnm and Tnm values [40].…”

“…Given their unique characteristics, we opted to use copolymers (including block copolymers) in our study. These polymeric materials are employed to coat silver nanoparticles, effectively modifying their dielectric environment and consequently altering their LSPR response [40].…”