Surface Plasmon-coupled Emission Research Articles

Surface Plasmon Coupled Directional Emission for Integrated Fluorescence‐Raman Biodetection: A Proof‐of‐Concept Study

AbstractThe development of multi‐functional nanoplatforms has attracted much attention. The realization of fluorescence and Raman dual‐mode bio‐detection typically needs complicated switching procedures or algorithm processes. In this work, we propose that a surface plasmon coupled emission (SPCE) technique could be used to break the bottleneck. Our approach enabled Raman spectra which would normally suffer interfered by strong fluorescence signal to be distinguished, simply by respective measurements at different angles. As a proof of concept, we prepared dual‐mode nano‐composites for measurement. Herein, in SPCE, fluorescence was sharply distributed at 46° and Raman at 50°. Attributed to the unique directional radiation feature, collection efficiency increased dramatically, with nearly 5‐fold and 14‐fold absolute intensity enhancement compared to conventional fluorescence and Raman method. Meanwhile, Raman detectability could be improved dramatically in SPCE detection in contrast to free space measurement in one single wavelength excitation device, for serious fluorescence interference to Raman tags could be eliminated.

Gelucire®-mediated heterometallic AgAu nanohybrid engineering for femtomolar cysteine detection using smartphone-based plasmonics technology

Conventionally nanoparticles (NPs) are synthesized using reducing and capping agents that are often hazardous for the environment and are not economically viable. Consequently, there is a growing requirement of bio-friendly methodologies for nanosynthesis via the green chemistry approach. The present study discusses the frugal and cost effective one-pot synthesis of AgAu nanohybrid exploiting the UV-treatment without the use of environmentally hazardous chemicals. Biocompatible pharmaceutical carrier Gelucire® has been utilized for this purpose as both the reducing agent and stabilizer. The obtained nanohybrids displayed unique nano-geometries and generated regions of augmented electromagnetic (EM) intensity ‘hotspots’ while studied on metallic thin films in reverse Kretschmann (RK) configuration. In addition to being highly beneficial from the sustainable development standpoint, the synthesized nanohybrids showcased unprecedented surface plasmon-coupled emission (SPCE) enhancement of >1000-fold and a sharply directional, p-polarized dequenched emission, on account of high EM field intensity. Furthermore, the obtained augmented SPCE enhancement was utilized for attaining femtomolar sensitivity of biologically significant amino acid cysteine using a mobile phone based plasmonics platform. Excellent correlation has been observed between the results obtained using an expensive spectrophotometer and the user-friendly mobile phone-based detector.

Power dependent surface plasmon coupled emission studies of metal-dielectric-metal planar structure

Surface plasmon coupled emission (SPCE) was demonstrated in Metal-Dielectric-Metal Planar (MDMP) structure by coupling MDMP structure to a hemicylindrical prism by Reverse Kretchmann configuration. Here silver and Fluorescein dye dispersed in polyvinyl Alcohol (PVA) were used as metal and dielectric layers respectively. Due to the combined effect of (1) confinement of photon mode within MDMP structure and (2) excitation of plasmon modes by RK configuration, highly directional and enhanced emission was observed. Dependence of SPCE emissions on input excitation power were studied. Higher dielectric thickness (∼600 nm) shows a better emission efficiency as compared to lower dielectric thickness (∼140 nm). Our simulation results show that a higher field distribution within MDMP structure for dielectric thickness of 600 nm resulting in better surface plasmon emission coupling and hence in better emission efficiency.

Single-Molecule Blinking Fluorescence Enhancement by Surface Plasmon-Coupled Emission-Based Substrates for Single-Molecule Localization Imaging

Surface plasmon-coupled emission (SPCE) substrates to enhance the blinking fluorescence of spontaneously blinking fluorophores in single-molecule localization microscopy (SMLM) were fabricated to reduce the excitation power density requirement and reveal the distribution of fluorophore-labeled proteins on a plasma membrane with nanoscale-level resolution. The systemic investigation of the contribution of local field enhancement, modified quantum yield, and emission coupling yield through glass coverslip substrates coated with metal layers of different thicknesses revealed that the silver-layer substrate with a thickness of 44 nm produces the highest SPCE fluorescence in spontaneously blinking fluorophores, and it has a highly directional SPCE fluorescence, which helps improve the detection efficiency. Moreover, the uniform and surface-enhanced field created on the substrate surface is beneficial for fluorescence background reduction in single fluorophore detection and localization, as well as for revealing the real position of fluorophores. Consequently, compared with a glass coverslip substrate, the presented SPCE substrate demonstrated a fluorescence enhancement of 480% and an increase in blinking events from a single spontaneously blinking fluorophore; moreover, the required excitation power density for SMLM imaging was significantly reduced to 23 W cm-2 for visualizing the distribution of epidermal growth factor receptors (EGFRs) on the basal plasma membrane of A549 lung cancer cells with a localization precision of 19 ± 7 nm. Finally, the fluorophore-labeled EGFRs on the basal plasma membrane in the presence of PIKfyve-specific inhibitor treatment were explored using SPCE-SMLM imaging; the results revealed a distinct reduction in the density of localization events because of a decrease in EGFR abundance at the plasma membranes of the cells.

Surface Plasmon-Coupled Dual Emission Platform for Ultrafast Oxygen Monitoring after SARS-CoV-2 Infection

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.

Multiarchitecture-Based Plasmonic-Coupled Emission Employing Gold Nanoparticles: An Efficient Fluorescence Modulation and Biosensing Platform.

Surface plasmon-coupled emission (SPCE) is an efficient surface-enhanced fluorescence method based on the near-field coupling process of surface plasmons and fluorophores. Based on this, we developed multiple coupling structures for an SPCE system by introducing gold nanoparticles (AuNPs) with different architectures by adjusting different modification methods and configurations. By assembling AuNPs on a gold substrate through electrostatic adsorption and spin-coating, 40- and 55-fold enhancements were obtained compared to free space (FS) emission, respectively. After theoretical simulations and the optimization of experimental conditions, a novel "hot-spot" plasmonic structure, an intense electromagnetic field within the system, plasmonic properties, and the coupled process were found to be mainly responsible for the diverse enhancement effects observed. For the spin-coating deposition method, new enhancing systems with high efficiency can be easily built without complex modification. Additionally, the subsequent detection system based on the uniform modification of AuNPs through electrostatic adsorption is convenient to establish with high sensitivity and stability, which can broaden the application of SPCE in both fluorescence-based sensing and imaging. This AuNP-enhanced SPCE using an electrostatic adsorption method was designed as an immunosensor to prove feasibility.

30 seconds procedure for decoration of titania nanotube with noble metals as metal-dielectric spacer materials towards tunable Purcell Factor and plasmon-coupled emission enhancement

In this manuscript, we demonstrate rapid decoration of titania nanotube (TiNT) with noble metals using electrochemical synthesis and its application as a hybrid metal-dielectric spacer and cavity material in surface plasmon-coupled emission (SPCE) platform. Using the metal-dielectric spacer architecture consisting of Pt decorated titania nanotubes, [email protected], we have achieved remarkable 104-fold fluorescence signal enhancement in the SPCE platform, owing to the combined effect of low plasmon loss of TiNT, increased local field excitation by Pt nanoparticles and increased activity of TiNT by Pt decoration. We have further carried out finite-difference time-domain (FDTD) simulation to compute the Purcell factor (PF) and correlated it with the enhancement obtained from SPCE experiments. Besides, we have also evaluated the effect of Au and Au–Pt decorated TiNT as a plasmonic substrate.

Plasmonic-Silver Sorets and Dielectric-Nd2O3 nanorods for Ultrasensitive Photonic Crystal-Coupled Emission

Nanocavities forms the basis for plasmon-enhanced luminescence-based sensing technologies. Although surface plasmon-coupled emission platform has progressed with interdisciplinary applications, detrimental Ohmic losses in them hamper luminescence enhancement. An analogous micro-photonic platform, photonic crystal-coupled emission platform overcomes these limitations with Purcell–enhanced luminescence augmentation. Ag soret colloids presenting interfacial nanovoids offered amplified emission enhancements while coupling with Bloch surface waves in one-dimensional photonic crystal. A highly desirable synergistic approach with the use of plasmonic-silver nanoassembly (soret) and dielectric, high refractive index, Nd2O3 ‘Huygen’ sources (efficient forward light scatterers) have been comprehensively studied with added understanding from numerical calculations. A judicious synergy of metal and dielectric plasmonics with photonic crystal interface is demonstrated with new biophysicochemical insights. Fluorescence enhancements, directional and polarized emission obtained in excess of 1200-fold was utilized for attomolar sensing of xenobiotic Rhodamine B dye in integrated cavity ‘hotspots’ due to amplified electromagnetic field intensity.

Photoplasmonic assembly of dielectric-metal, Nd2O3-Gold soret nanointerfaces for dequenching the luminophore emission

Abstract A variety of materials such as low dimensional carbon substrates (1D, 2D, and 3D), nanoprisms, nanocubes, proteins, ceramics, and DNA to name a few, have been explored in surface plasmon-coupled emission (SPCE) platform. While these offer new physicochemical insights, investigations have been limited to silver as primary plasmonic material. Although, gold nanoparticles (AuNPs) exhibit robust performance, its intrinsic property to quench the emission from radiating dipoles (at distances < 5 nm) has impeded its utility. Despite the use of metal-dielectric resonances (with Au decorated SiO2 NPs) and sharp nanotips (from Au nanostars) for dequenching the emission, the enhancements obtained has been less than 200-fold in SPCE platform. To address these long-standing challenges, we demonstrate the utility of gold soret colloids (AuSCs) and photonic crystal-coupled emission (PCCE) platform. The soret nano-assemblies synthesized using adiabatic cooling technique presented integrated hotspots when taken with high refractive index Nd2O3 ‘Huygens sources’. The collective and coherent coupling between localized Mie and delocalized Bragg plasmons (of sorets), dielectric plasmons (of Nd2O3), highly confined and intense Bloch surface waves (of PCCE platform) aided in realization of dequenched, as well as amplified > 1500-fold enhancements at the photoplasmonic nanocavity interface, presenting new opportunities for multidisciplinary applications.

Engineering of coherent plasmon resonances from silver soret colloids, graphene oxide and Nd2O3 nanohybrid architectures studied in mobile phone-based surface plasmon-coupled emission platform

Nanoparticle assemblies obtained using adiabatic cooling methodology is termed soret colloids (SCs). They are utilized in different sensing applications on account of their unique material properties. Here, silver (Ag) SCs were synthesized incorporating low-dimensional graphene oxide (GO) in the nanoassembly to engineer hybrid architectures. The plasmonic performance of synthesized AgGOSC hybrid sorets were studied on Ag nanofilm in spacer nanoassembly with and without additional GO monolayer and Nd2O3 nanorods. The highly p-polarized and directional >900-fold surface plasmon-coupled emission (SPCE) enhancement was obtained with excellent correlation with mobile phone-based luminosity analysis, amenable for resource-limited settings.

Fluorescence Enhancement via Dual Coupling of Dye Molecules with Silver Nanostructures

We demonstrate the enhancement of fluorescence emitted from dye molecules coupled with two surface plasmons, i.e., silver nanoparticles (AgNPs)-induced localized surface plasmons (LSP) and thin silver (Ag) film supported surface plasmons. Excitation light is illuminated to a SiO2 layer that contains both rhodamine 110 molecules and AgNPs. AgNPs enhances excitation rates of dye molecules in their close proximity due to LSP-induced enhancement of local electromagnetic fields at dye excitation wavelengths. Moreover, the SiO2 layer on one surface of which a 50 nm-thick Ag film is coated for metal cladding (air on the other surface), acts as a waveguide core at the dye emission wavelengths. The Ag film induces the surface plasmons which couple with the waveguide modes, resulting in a waveguide-modulated version of surface plasmon coupled emission (SPCE) for different SiO2 thicknesses in a reverse Kretschmann configuration. We find that varying the SiO2 thickness modulates the fluorescent signal of SPCE, its modulation behavior being in agreement with the theoretical simulation of thickness dependent properties of the coupled plasmon waveguide resonance. This enables optimization engineering of the waveguide structure for enhancement of fluorescent signals. The combination of LSP enhanced dye excitation and the waveguide-modulated version of SPCE may offer chances of enhancing fluorescent signals for a highly sensitive fluorescent assay of biomedical and chemical substances.

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

Although there are numerous techniques for the synthesis of plasmonic (metallic Ag and Au) nanomaterials, eco-friendly and biocompatible methodologies that present diverse applications in nanophotonics and biomedical domains are seldom reported. Soluplus is a graft copolymer of polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol and is extensively used for improving the solubility and bioavailability of poorly water-soluble drugs. However, the utility of their amphiphilic chemical structure, strong UV-light absorbing, and bifunctional properties of the polymer matrix as well as its role as a solubilizer have not been explored for rapid synthesis of plasmonic bimetallic nanohybrids. Although a variety of nanoparticles (NPs) have been studied for surface plasmon-coupled emission (SPCE) spectroscopic applications, AgAu nanohybrids have not been examined in the subject platform hitherto. In this article, we demonstrate a synthesis route for obtaining AgNPs, AuNPs, and AgAu nanohybrids using soluplus as both the reducing and capping agent in a simple UV-light induced one-pot rapid technique. These hybrid nanomaterials were interfaced with propagating surface plasmon polaritons from a 50 nm Ag thin film to understand the plasmonic coupling phenomenon in spacer, cavity, and extended cavity nanoconfigurations. The obtained AgAu nanohybrids aided in addressing the three major long-standing challenges in SPCE technology development, namely, (i) unavoidable quenching in the presence of AuNPs, (ii) chemical instability in AgNPs, and (iii) intrinsic ohmic losses in plasmonic NPs. In addition to overcoming the above-mentioned caveats, unaccustomed >1200-fold sharply directional and polarized SPCE enhancements were achieved using AgAu nanohybrids. The multifold nanogaps generated in AgAu nanohybrid sustained multiple hotspots catering to attomolar sensitivity of the SPCE reporter molecule, rhodamine B (RhB). The proposed methodology to obtain dequenched as well as augmented SPCE enhancements is of utmost utility in biophysicochemical sensor development.

Surface Plasmon-Assisted Fluorescence Enhancing and Quenching: From Theory to Application.

The integration of surface plasmon resonance and fluorescence yields a multiaspect improvement in surface fluorescence sensing and imaging, leading to a paradigm shift of surface plasmon-assisted fluorescence techniques, for example, surface plasmon enhanced field fluorescence spectroscopy, surface plasmon coupled emission (SPCE), and SPCE imaging. This Review aims to characterize the unique optical property with a common physical interpretation and diverse surface architecture-based measurements. The fundamental electromagnetic theory is employed to comprehensively unveil the fluorophore-surface plasmon interaction, and the associated surface-modification design is liberally highlighted to balance the surface plasmon-induced fluorescence-enhancement efforts and the surface plasmon-caused fluorescence-quenching effects. In particular, all types of surface structures, for example, silicon, carbon, protein, DNA, polymer, and multilayer, are systematically interrogated in terms of component, thickness, stiffness, and functionality. As a highly interdisciplinary and expanding field in physics, optics, chemistry, and surface chemistry, this Review could be of great interest to a broad readership, in particular, among physical chemists, analytical chemists, and in surface-based sensing and imaging studies.

Synergistic coupling of titanium carbonitride nanocubes and graphene oxide for 800-fold fluorescence enhancements on smartphone based surface plasmon-coupled emission platform

High refractive index, dielectric TiCN nanocubes presenting sharp nano-edges and nano-corners interfaced with plasmonic Ag nanofilms were evaluated with and without graphene oxide nanolayer in surface plasmon-coupled emission (SPCE) substrates. The sharply directional and polarized SPCE displayed >800-fold enhancements on account of integrated hotspots presenting augmented electromagnetic fields. The obtained fluorescence enhancements were in excellent correlation with the luminosity values obtained via smartphone based SPCE platform. The in-house developed technology presents unique advancement for sensing applications with futuristic scope for exploration of novel nanomaterials with 2-dimensional plasmonic materials.

Fluorescence Based on Surface Plasmon Coupled Emission for Ultrahigh Sensitivity Immunoassay of Cardiac Troponin I.

This work demonstrates the quantitative assay of cardiac Troponin I (cTnI), one of the key biomarkers for acute cardiovascular diseases (the leading cause of death worldwide) using the fluorescence-based sandwich immune reaction. Surface plasmon coupled emission (SPCE) produced by non-radiative coupling of dye molecules with surface plasmons being excitable via the reverse Kretschmann format is exploited for fluorescence-based sandwich immunoassay for quantitative detection of cTnI. The SPCE fluorescence chip utilizes the gold (2 nm)-silver (50 nm) bimetallic thin film, with which molecules of the dye Alexa 488 (conjugated with detection antibodies) make a near field coupling with the plasmonic film for SPCE. The experimental results find that the SPCE greatly improves the sensitivity via enhancing the fluorescence signal (up to 50-fold) while suppressing the photo-bleaching, permitting markedly enhanced signal-to-noise ratio. The limit of detection of 21.2 ag mL−1 (atto-gram mL−1) is obtained, the lowest ever reported to date amid those achieved by optical technologies such as luminescence and label-free optical sensing techniques. The features discovered such as ultrahigh sensitivity may prompt the presented technologies to be applied for early diagnosis of cTnI in blood, particularly for emergency medical centers overloaded with patients with acute myocardial infarction who would suffer from time-delayed diagnosis due to insufficient assay device sensitivity.

Metal-Free, Graphene Oxide-Based Tunable Soliton and Plasmon Engineering for Biosensing Applications.

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.

Multifunctional hybrid soret nanoarchitectures for mobile phone-based picomolar Cu2+ ion sensing and dye degradation applications

The ability of nanoscale materials to trap electromagnetic field beyond the diffraction limit is seldom studied using multifunctional nanohybrids. To this end, we demonstrate a thermo-migratively assembled Soret nanoassembly that enable unique metal-metal, metal-graphene and metal-dielectric resonances. In contrast to the well-explored standalone plasmonic and dielectric platforms, the Soret colloids possess salient nanogaps that exhibit delocalized Bragg and localized Mie plasmon resonances with effective EM field confinement. Accordingly, the Soret colloids of silver metal with plasmonic NPs: platinum (AgPtSC), 2D material: graphene oxide (AgGOSC) and dielectric NPs: TiC (AgTiCSC), TiN (AgTiNSC) and TiCN (AgTiCNSC) comprehensively have been utilized to achieve >600-fold fluorescence enhancements. The ability to tailor the highly directional and p-polarized emission enhancements using these well-characterized multifunctional sorets has been experimentally demonstrated on surface plasmon-coupled emission (SPCE) platform. The mobile phone-based detection of environmentally relevant Cu 2+ ions in drinking water using AgPtSC presents low-cost, rapid, simple, sensitive and reliable sensing strategy for Cu 2+ ion monitoring in resource-limited settings. Further, dye-degradation of xenobiotic pollutants for environmental remediation presents multifarious applications with these nano-architectures. This study opens a new window to explore synergy of nanomaterials constituting elements from different parts of periodic table to accomplish essential properties for desired applications. The hybrid multifunctional soret colloids assisting metal-metal, metal-dielectric and metal-π-plasmon resonances are most suitable candidates for plasmonic as well as xenobiotic dye degradation applications. Mobile phone-based surface plasmon-coupled emission platform was utilized for sensing Cu 2+ ions at picomolar concentration. • An adiabatic cooling based synthesis of hybrid multifunctional soret nanoassembly. • Utility of synergistic metal-metal, metal-dielectric and metal-π-plasmon resonances. • Multifold hot-spots from localized and delocalized plasmons of nanohybrids in SPCE. • Enhanced 600-fold polarized SPCE for mobile phone-based picomolar Cu 2+ ion sensing. • Xenobiotic degradation using π-plasmon and electron relay in hybrid silver sorets.

Engineering metal-dielectric nanostructures involving silver decorated Halloysite for augmented surface plasmon-coupled directional emission

Metal-dielectric hybrid nanostructures have recently drawn interest because of their direct coupling between metal surface plasmon resonance and dielectric electric dipoles leading to hybridized modes resulting in low losses and high field enhancements. Surface plasmon-coupled emission is a similar phenomenon that exploits the surface plasmon polaritons generated at the junction of dielectric and metal planar boundary. In this regard, we propose and demonstrate the use of dielectric nanotubes – Halloysite (HS) as spacer materials on metallic silver thin film. In this work, we selectively modified HS by acid or base treatment. Further they were loaded with silver nanoparticles (AgNPs) by solution deposition (in-situ method), thereby creating a metal-dielectric hybrid material. Selective acid and base treatment of HS nanotubes affected the surface charge distribution and aggregation of the nanotubes. Better dispersion ability and higher electronegativity behaviour was observed in base-treated HS that aided in higher loading of AgNPs. Enhanced interparticle plasmon coupling and better transmission of plasmon mediating energy was observed in base-treated HS-Ag that augmented dipole emission. The enhanced plasmon-coupled emission of HS-Ag nanostructures were also explored using a low-cost mobile phone as a detector to simplify the process of fluorescence detection.

Amplified Fluorescence by Hollow-Porous Plasmonic Assembly: A New Observation and Its Application in Multiwavelength Simultaneous Detection.

Surface plasmon coupled emission (SPCE) is a new analytical technique that provides increased and directional radiation based on the near-field interaction between fluorophores and surface plasmons but suffers from the limitation of insufficient sensitivity. The assembly of hollow-porous plasmonic nanoparticles could be the qualified candidate. After the introduction of gold nanocages (AuNCs), fluorescence signal enhancement was realized by factors over 150 and 600 compared with the normal SPCE and free space emission, respectively, with a fluorophore layer thickness of approximately 10 nm; hence, the unique enhancement of SPCE by the AuNCs effectively overcomes the signal quenching induced by resonance energy transfer (in normal SPCE). This enhancement was proven to be triggered by the superior wavelength match, the enhanced electromagnetic field, and new radiation channel and process induced by the AuNC assembly, which provides an opportunity to increase the detection sensitivity and establish an optimal plasmonic enhancement system. The amplified SPCE system was employed for multiwavelength simultaneous enhancement detection through the assembly of mixed hollow nanoparticles (AuNCs and gold nanoshells), which could broaden the application of SPCE in simultaneous sensing and imaging for multianalytes.

Engineering of Exciton–Plasmon Coupling Using 2D-WS2 Nanosheets for 1000-Fold Fluorescence Enhancement in Surface Plasmon-Coupled Emission Platforms

Enhancement of fluorescence emission from single-photon quantum emitters on plasmonic nanomaterials using surface plasmon-coupled emission (SPCE) platforms has seen significant advancements. In parallel, there has also been an exponential rise in applications involving two-dimensional (2D) transition-metal dichalcogenides (TMDs) that exhibit unique exciton-plasmon interactions. Although both these Frontier research areas have impacted the development of sensor and sensing technologies, no study coalesces these two arenas for translational applications. In this work, we use thin WS2 nanosheets for realizing 1000-fold fluorescence enhancement on the SPCE platform. Structure-dependent fluorescence enhancement exhibited by WS2 provides new insight into the use of TMDs and exciton-plasmon coupling in SPCE substrates. Cellphone-based detection of the emitting dipole is another unique aspect of this work that presents a low-cost alternative in comparison with high-end detectors.