Sensing Biomolecular Interactions by the Luminescence of a Planar Gold Film

Abstract

We describe the operating principle and performance of a recently developed surface plasmon-enhanced optical sensor that utilizes two-photon excited luminescence of a planar gold film as the reporter signal. The sensor enables direct visualization of nanoscopic binding events near a sensing surface. Light is coupled to the Au/sample interface in an objective-based Kretschmann configuration to excite surface plasmon polariton (SPP) modes at a metal−dielectric interface. The gold luminescence induced by the confined optical field between the particle and the film is detected in the epi-direction by a far-field camera where individual binding events show up as diffraction limited bright spots against a dark background. We study the sensor's emission spectrum and the distance dependence between the target and substrate, which both suggest that the optical signal of the sensor originates from electron−hole pair excitations in the planar Au film. In addition, we show that the well-behaved pointspread function of the sensor enables a straightforward implementation of superresolution techniques. Finally, we demonstrate the utility of the sensor for detecting DNA binding events, underlining the sensor's usefulness for label-free imaging of nanoscopic particles and biomolecular interactions.

Surface-Enhanced Coherent Anti-Stokes Raman Scattering of Molecules near Metal–Dielectric Nanojunctions

“…Equivalently, TPEL from the gold film can be monitored to find this angle. 51 This luminescent background is attributed to the interband transitions in the gold film and the subsequent radiative recombination of electron−hole pairs. 52 We first perform SE-CARS measurements on a Au particle− Au film nanoantenna system in the wide-field Kretschmann configuration.…”

Sensitive Detection of SARS-CoV-2 Using a Novel Plasmonic Fiber Optic Biosensor Design

“…Nevertheless, RT-qPCR needs at least 3 h and demands sophisticated testing setups [ 8 ] in addition to suffering from false positives. To this end, one potential area is the use of biosensors [ 9 , 10 ].…”

Sensitive Detection of SARS-CoV-2 Using a Novel Plasmonic Fiber Optic Biosensor Design

“…Nevertheless, RT-qPCR needs at least 3 h and demands sophisticated testing setups [8] in additional to suffering from false positives. To this end, one potential area is the use of biosensors [9,10].…”