Nanoparticle–Film PlasmonRuler Interrogatedwith Transmission Visible Spectroscopy

摘要

The widespread use of plasmonic nanorulers (PNRs) in sensing platforms has been plagued by technical challenges associated with the development of methods to fabricate precisely controlled nanostructures with high yield and characterize them with high throughput. We have previously shown that creating PNRs in a nanoparticle–film (NP–film) format enables the fabrication of an extremely large population of uniform PNRs with 100% yield using a self-assembly approach, which facilitates high-throughput PNR characterization using ensemble spectroscopic measurements and eliminates the need for expensive microscopy systems required by many other PNR platforms. We expand upon this prior work herein, showing that the NP–film PNR can be made compatible with aqueous sensing studies by adapting it for use in a transmission localized surface plasmon resonance spectroscopy format, where the coupled NP–film resonance responsible for the PNR signal is directly probed using an extinction measurement from a standard spectrophotometer. We designed slide holders that fit inside standard spectrophotometercuvettes and position NP–film samples so that the coupled NP–filmresonance can be detected in a collinear optical configuration. Oncethe NP–film PNR samples are cuvette-compatible, it is straightforwardto calibrate the PNR in aqueous solution and use it to characterizedynamic, angstrom-scale distance changes resulting from pH-inducedswelling of polyelectrolyte (PE) spacer layers as thin as 1 PE layerand also of a self-assembled monolayer of an amine-terminated alkanethiol.This development is an important step toward making PNR sensors moreuser-friendly and encouraging their widespread use in various sensingschemes.