Superior Resonant Nanocavities Engineering on the Photonic Crystal-Coupled Emission Platform for the Detection of Femtomolar Iodide and Zeptomolar Cortisol

Abstract

Although luminescence spectroscopy has been a promising sensing technology with widespread applications in point-of-care diagnostics and chem-bio detection, it fundamentally suffers from low signal collection efficiency, considerable background noise, poor photostability, and intrinsic omnidirectional emission properties. In this regard, surface plasmon-coupled emission, a versatile plasmon-enhanced detection platform with >50% signal collection efficiency, high directionality, and polarization has previously been explored to amplify the limit of detection of desired analytes. However, high Ohmic loss in metal-dependent plasmonic platforms has remained an inevitable challenge. Here, we develop a hybrid nanocavity interface on a template-free and loss-less photonic crystal-coupled emission (PCCE) platform by the quintessential integration of high refractive index dielectric Nd2O3 “Huygens sources” and sharp-edged silver nanoprisms (NPrs). While efficient forward light scattering characteristics of Nd2O3 nanorods (NRs) present 460-fold emission enhancements in PCCE, the tunable localized plasmon resonances of NPrs display high electromagnetic field confinement at sharp nanotips and protrusions, boosting the enhancements 947-fold. The judicious use of silver NPr (AgNPr) metal-Nd2O3 dielectric hybrid resonances in conjugation with surface-trapped Bloch surface waves of the one-dimensional photonic crystal (1DPhC) displayed unprecedented >1300-fold enhancements. The experimental results are validated by excellent correlations with numerical calculations. The multifold hotspots generated by zero and nonzero nanogaps between the coassembly of NPrs, NRs, and 1DPhCs are used for (i) determination of hyper and hypothyroidism levels through monitoring the concentration of iodide (I–) ions and (ii) single-molecule detection (zeptomolar) of the stress hormone, cortisol, through the synthesized cortisol-rhodamine B conjugate obtained using a simple esterification reaction.

Plasmon-Coupled Directional Emission from Soluplus-Mediated AgAu Nanoparticles for Attomolar Sensing Using a Smartphone

“…All the optical experiments were performed in line with our earlier works. 7,9,11 The SPCE substrate attached to the BK7 prism (using index matching fluid; refractive index, 1.47) is mounted on a 360°r otating stage before the experimentation. The reverse Kretschmann (RK) configuration was utilized for all the experiments, where the 532 nm continuous wave laser source (35 mW) excites the radiating dipoles (coated on Ag thin nanofilm) directly.…”

“…13 Recently, research efforts have been devoted to synergize PEF and SPCE into a single hybrid platform. [7][8][9][10][11]14 Generally, the enhancement factor of SPCE substrate is 5−10-fold as compared to traditional luminescence. [7][8][9][10][11]15 Lakowicz and coworkers have demonstrated the significance of silver (Ag) NPs spacer layer engineering on SPCE platform to further augment the enhancement to 60-fold.…”

“…[7][8][9][10][11]14 Generally, the enhancement factor of SPCE substrate is 5−10-fold as compared to traditional luminescence. [7][8][9][10][11]15 Lakowicz and coworkers have demonstrated the significance of silver (Ag) NPs spacer layer engineering on SPCE platform to further augment the enhancement to 60-fold. 15 With this as a preliminary step for combining PEF and SPCE, diverse nanoarchitectures have been explored to further augment the SPCE enhancements.…”

“…The conventional luminescence based sensing methodologies are omnidirectional with less than 1% signal collection. − In this context, the SPCE technique aids in channelizing the emission into a spectrally tapered angular distribution with a high percentage of p-polarization. Consequently, the collection efficiency is greatly enhanced (>50%) assisting with multiplexed detection of the analytes, with suppressed background noise. − Dissimilar metallic or plasmonic nanofilms have been explored to study this phenomenon, along with different thicknesses of the dielectric layer to comprehend the waveguide and plasmon modes. , SPCE has endowed researchers with opportunities for exploring different optical phenomena, chemical processes, and biophysical sensing applications. − …”

Particle swarm optimization of GaAs-AlGaAS nanowire photonic crystals as two-dimensional diffraction gratings for light trapping

“…In particular, thanks to their high symmetry, are excellent platforms to design diffraction gratings able to guarantee the fine control of light coupling along certain directions for specific frequencies, depending on the design parameters The employment of optimised photonic structures to enhance specific optical functionalities is a vibrant research topic. Such a feature is largely exploited for light trapping based applications [4] such as solar cells [5,6] and sensing [7][8][9][10][11], or to control the emission of optical emitters [12][13][14]. In this context, ordered semiconductor nanowire (NW) ensembles grown onto a substrate are a suitable starting platform [15][16][17].…”