Plasmonic nanograting enhanced quantum dots excitation for cellular imaging on-chip

Abstract

We present the design and integration of a two-dimensional (2D) plasmonic nanogratings structure on the electrode of colloidal quantum dot-based light-emitting diodes (QDLEDs) as a compact light source towards arrayed on-chip imaging of tumor cells. Colloidal quantum dots (QDs) were used as the emission layer due to their unique capabilities, including multicolor emission, narrow bandwidth, tunable emission wavelengths, and compatibility with silicon fabrication. The nanograting, based on a metal-dielectric-metal plasmonic waveguide, aims to enhance the light intensity through the resonant reflection of surface plasmon (SP) waves. The key parameters of plasmonic nanogratings, including periodicity, slit width, and thicknesses of the metal and dielectric layers, were designed to tailor the frequency bandgap such that it matches the wavelength of operation. We fabricated QDLEDs with the integrated nanogratings and demonstrated an increase in electroluminescence intensity, measured along the direction perpendicular to the metal electrode. We found an increase of 34.72% in QDLED electroluminescence intensity from the area of the pattern and an increase of 32.63% from the photoluminescence of QDs deposited on a metal surface. We performed ex vivo transmission-mode microscopy to evaluate the nucleus-cytoplasm ratios of MDA-MB 231 cultured breast cancer cells using QDLEDs as the light source. We showed wavelength dependent imaging of different cell components and imaging of cells at higher magnification using enhanced emission from QDLEDs with integrated plasmonic nanogratings.

Patterned Plasmonic Surfaces—Theory, Fabrication, and Applications in Biosensing

“…The transmission properties of the plasmonic nanograting structures are usually coupled with sharp resonances over a narrow bandwidth [19]. This methodology has been used to enhance on-chip quantum dot cellular imaging resolution.…”

“…We have carried out a series of work in creation novel light source and nanoprobes for NSOM [19, 112, 113]. The large-scale applications of conventional NSOM are limited due to the manual assembly process of the probe with fiber and the requirement of an external light source.…”

“…With the capability from near UV to IR emission, plasmonic enhanced, mass-producible, and self-illuminating nano-LED on-chip will open up many exciting opportunities in biomedical and industrial applications, including near-field microscopy of subcellular structures, direct material patterning, and compact “light-on-chip” biosensors and biochips. Plasmonic structures including plasmonic microplates [115], thin metal films [116], gold colloids [117], plasmonic wells [114], and plasmonic nanogratings [19] have been applied to enhance luminescence of QDs.…”

“…The unique characteristics of QDs, including tunable emission wavelength, narrow bandwidth and the capability of photo- and electrical-excitation, makes them ideal material as on-chip light source for cellular imaging. Bhave et al integrated a 2D plasmonic nanogratings structure with QD LEDs as a compact light source for on-chip imaging of tumor cells [19]. …”

“…p is the period, l = ( p − w D )/2 is the stub length, t M is the metal thickness, and, w D and w S are the widths of dielectric layer and slit, respectively. The equivalent load impedance $Z_{\mathrm{L}}^{\pm }$ can be readily calculated by evaluating the ratio for forward and backward magnetic-field waves at the periodic boundary [19]. …”