Super-Resolution Light Microscopy Using Plasmonic Gratings

Abstract

A novel platform for super-resolution imaging has been devised that employs plasmonic gratings fabricated using glancing angle deposition (GLAD) of silver. GLAD was found to produce a large population of unique nanostructures over the entire plasmonic grating. These nanostructures excite nearby fluorescent molecules to improve spatial resolution to sub-diffraction limit distances while also increasing signal-to-noise ratio (SNR). For example, the improved localization precision produces 65 nm image resolution on a highly concentrated fluorescent sample. These inexpensive plasmonic GLAD gratings have potential to improve fluorescent intensity and resolution over a wide range of applications.

Surface Plasmon Enhanced Fluorescence Temperature Mapping of Aluminum Nanoparticle Heated by Laser

“…No noticeable changes in morphology were apparent in the Al NP after heating with 808 nm laser. Previously, we reported that heating of Al NP clusters with 808 nm laser generated a greater heating rate than other wavelengths used in that work [ 52 , 59 ], so the absence of morphology change suggests that no permanent effects (e.g., ignition) occurred during heating with the 808 nm laser at the current laser fluence. This was confirmed by the equivalent image in scattering mode using both polarizer and analyzer at 0° with respect to the grating axis, which revealed depolarization effects due to the metallic content of Al NP.…”

“…These peak locations were blueshifted by about 10 nm with respect to the expected peak locations for dye aggregates in either solution [ 61 , 62 , 63 ] or solid thin films [ 64 ]. We attribute the blueshifted fluorescence emission to the well-documented surface plasmon-coupled emission (SPCE) effect over plasmonic gratings [ 57 , 59 ], whereby the excited state energy of the fluorophore was transferred nonradiatively back to the grating prior to radiative emission by scattering from the grating itself. This process reduced the energy lost to internal conversion within the dye prior to radiative emission and produced a blueshift regardless of other effects.…”

“…We designed a custom optical setup to accommodate these requirements ( Figure 1 B and Figure S1 ), which includes (i) a laser mount with focusing lenses and micropositioner, (ii) an optical filter set for beam formation and fluorescence excitation and emission, and (iii) a laser synchronization driver. A 300 mW-rated near-infrared 808 nm diode laser was chosen for the heating source since the high absorption efficiency of Al NPs in the near-infrared regime is thought to support photothermal heating by plasmonic coupling and dielectric loss [ 59 ]. Meanwhile, the 808 nm laser light will couple weakly to the silver grating at a 0° angle of incidence (i.e., normal incidence), reducing the direct heating of the grating significantly with respect to visible range lasers [ 52 ].…”

Applications of machine learning tools for ultra-sensitive detection of lipoarabinomannan with plasmonic grating biosensors in clinical samples of tuberculosis

“…Silver plasmonic gratings were prepared by soft lithography process similar to [19][20][21][22][23]. A silicone stamp was prepared by curing 5:1 ratio Sylgard 1 184 polydimethylsiloxane (PDMS, Gelest) over a halved, cleaned HDDVD for 24 hours at 50 ˚C and 55% relative humidity.…”

“…One significant drawback of using fluorescence blinking as a detection modality is the associated signal-to-noise ratio. Recently, our group has developed a cost-effective plasmonic grating platform to detect and analyze chemical and biological molecules down to the SM level using only an upright epi-fluorescence microscope [19][20][21][22][23], replacing expensive total internal reflection (TIR) or confocal optics. Plasmonic gratings rely on a property of noble metals in which they convert incident photons into standing electromagnetic (EM) waves at the surface of the metal-dielectric interface in a process known as surface plasmon resonance (SPR) [24][25][26].…”