The quest for auxiliary plasmonic
materials with lossless properties
began in the past decade. In the current study, a unique plasmonic
response is demonstrated from a stratified high refractive index (HRI)–graphene
oxide (GO) and low refractive index (LRI)–polymethyl methacrylate
(PMMA) multistack. Graphene oxide plasmon-coupled emission (GraPE)
reveals the existence of strong surface states on the terminating
layer of the photonic crystal (PC) framework. The chemical defects
in GO thin film are conducive for unraveling plasmon hybridization
within and across the multistack. We have achieved a unique assortment
of metal-dielectric-metal (MDM) ensuing a zero-normal steering emission
on account of solitons as well as directional GraPE. This has been
theoretically established and experimentally demonstrated with a metal-free
design. The angle-dependent reflectivity plots, electric field energy
(EFI) profiles, and finite-difference time-domain (FDTD) analysis
from the simulations strongly support plasmonic modes with giant Purcell
factors (PFs). The architecture presented prospects for the replacement
of metal-dependent MDM and surface plasmon-coupled emission (SPCE)
technology with low cost, easy to fabricate, tunable soliton [graphene
oxide plasmon-coupled soliton emission (GraSE)], and plasmon [GraPE]
engineering for diverse biosensing applications. The superiority of
the GraPE platform for achieving 1.95 pg mL–1 limit
of detection of human IFN-γ is validated experimentally. A variety
of nanoparticles encompassing metals, intermetallics, rare-earth,
and low-dimensional carbon–plasmonic hybrids were used to comprehend
PF and cavity hot-spot contribution resulting in 900-fold fluorescence
emission enhancements on a lossless substrate, thereby opening the
door to unique light–matter interactions for next-gen plasmonic
and biomedical technologies.
The
ability of plasmonic nanoparticles (NPs) to focus the impinging
electromagnetic (EM) radiation to subwavelength regimes assists in
the detection of molecules at extremely low concentrations. Numerous
nanomaterials have been exploited in the surface plasmon-coupled emission
(SPCE) technology, presenting quintessential physicochemical insights.
However, seldom attention has been paid toward utilizing the biocompatible
nanotechnology for substrate nanoengineering in SPCE. In this context,
we present LYCOAT-based silver (Ag) NPs synthesized via a frugal disruptive
approach by exposing a simple physical mixture of Ag+ ions
and LYCOAT to UV irradiation. Variations in the time of UV exposure
resulted in nanofractals and nanocubes of Ag presenting unique architectures
for nanophotonic applications, where the biocompatible LYCOAT functions
as both reducing and capping agents under ambient conditions. Nanomaterials
synthesized in this approach were studied in spacer, cavity, and extended
cavity nanointerfaces in the SPCE platform for obtaining tunable plasmonic
coupling. The augmented >900-fold SPCE enhancements were utilized
for mobile phone-based attomolar sensing of environmentally hazardous
Hg2+ ions. The simple, realistic, and eco-friendly methodology
adopted here for developing nanomaterials for photonic applications
opens the door for exploring such next-generation bio-inspired nanomaterials
for point-of-care diagnostic applications.
The
outbreak of the COVID-19 pandemic has had a major impact on
the health and well-being of people with its long-term effect on lung
function and oxygen uptake. In this work, we present a unique approach
to augment the phosphorescence signal from phosphorescent gold(III)
complexes based on a surface plasmon-coupled emission platform and
use it for designing a ratiometric sensor with high sensitivity and
ultrafast response time for monitoring oxygen uptake in SARS-CoV-2-recovered
patients. Two monocyclometalated Au(III) complexes, one having exclusively
phosphorescence emission (λPL = 578 nm) and the other
having dual emission, fluorescence (λPL = 417 nm)
and phosphorescence (λPL = 579 nm), were studied
using the surface plasmon-coupled dual emission (SPCDE) platform for
the first time, which showed 27-fold and 17-fold enhancements, respectively.
The latter complex having the dual emission was then used for the
fabrication of a ratiometric sensor for studying the oxygen quenching
of phosphorescence emission with the fluorescence emission acting
as an internal standard. Low-cost poly (methyl methacrylate) (PMMA)
and biodegradable wood were used to fabricate the microfluidic chips
for oxygen monitoring. The sensor showed a high sensitivity with a
limit of detection ∼ 0.1%. Furthermore, real-time oxygen sensing
was carried out and the response time of the sensor was calculated
to be ∼0.2 s. The sensor chip was used for monitoring the oxygen
uptake in SARS-CoV-2-recovered study participants, to assess their
lung function post the viral infection.
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