Plasmonic gratings with nano-protrusions made by glancing angle deposition for single-molecule super-resolution imaging

Abstract

Super-resolution imaging has been advantageous in studying biological and chemical systems, but the required equipment and platforms are expensive and unable to observe single-molecules at the high (μM) fluorophore concentrations required to study protein interaction and enzymatic activity. Here, a plasmonic platform was designed that utilized an inexpensively fabricated plasmonic grating in combination with a scalable glancing angle deposition (GLAD) technique using physical vapor deposition. The GLAD creates an abundance of plasmonic nano-protrusion probes that combine the surface plasmon resonance (SPR) from the periodic gratings with the localized SPR of these nano-protrusions. The resulting platform enables simultaneous imaging of a large area without point-by-point scanning or bulk averaging for the detection of single Cyanine-5 molecules in dye concentrations ranging from 50 pM to 10 μM using epifluorescence microscopy. Combining the near-field plasmonic nano-protrusion probes and super-resolution technique using localization microscopy, we demonstrate the ability to resolve grain sizes down to 65 nm. This plasmonic GLAD grating is a cost-effective super-resolution imaging substrate with potential applications in high-speed biomedical imaging over a wide range of fluorescent concentrations.

Substrate Oxide Layer Thickness Optimization for a Dual-Width Plasmonic Grating for Surface-Enhanced Raman Spectroscopy (SERS) Biosensor Applications

“…Plasmonic gratings provide the added benefit of covering a large area of the substrate, so as to improve the signal in many places, simultaneously, and also increase the enhancement with plasmonic grating effects [ 63 , 64 , 65 ]. For a biosensor substrate, the presence of many plasmonic hot spots increases the likelihood of locating an analyte molecule within one of these field-enhancing regions, thus improving the probability of detecting the presence of the desired species [ 66 ].…”

Super-Resolution Light Microscopy Using Plasmonic Gratings

“…Typically, single-molecule imaging in the low fluorophore concentration range requires amplified fluorescence emission intensity and/or increased camera sensitivity such that the signal of a single fluorophore is distinguishable over background noise. On the other hand, this type of imaging in high fluorophore concentrations [19] with permission, copyright 2016 RSC. 2017 January • www.microscopy-today.com Plasmonic Gratings large number of molecules and overlapped signals observed on highly concentrated fluorescent samples, we recorded the single/ double/multiple step photobleaching behavior on hotspots.…”

“…In this article we describe a novel fluorescence enhancement platform, recently published in Nanoscale [19], that further enhances the SNR without the need for complex optical setups. This platform uses a plasmonic grating with unique nanostructures grown on the surface.…”

A Localized Surface Plasmon Resonance Sensor Using Double-Metal-Complex Nanostructures and a Review of Recent Approaches

“…The resonance conditions in LSPR based on nanostructures or nanoparticles are more responsive than those of SPR. Therefore, LSPR has been actively applied to develop high-resolution imaging [ 74 , 75 , 76 , 77 , 78 ] and high-sensitivity sensing systems [ 79 , 80 , 81 , 82 ] based on the proportional relationship between concentrated fields and the sensitivity [ 83 ]. In fact, to find optimum condition of field localization, there have been reported lots of tries with varied nanostructures such as nanoslits or nanoholes.…”