Surface Plasmon-coupled Emission Research Articles

Surface Plasmon-Coupled Directional Emission Enhanced Raman Scattering Based on Waveguide Coupling Surface Plasmon Resonance Configuration

Surface Plasmon-Coupled Directional Emission Enhanced Raman Scattering Based on Waveguide Coupling Surface Plasmon Resonance Configuration

Regulation of laser-induced nanogratings by tuning the Marangoni-plasmon-coupled effect.

Laser-induced subwavelength nanogratings on films find widespread applications in enhancing a spectrum through surface plasmon excitation. It is challenging to achieve high uniformity, diversity, and controllability due to the intricate interplay between two basic mechanisms in laser nanostructuring: the Marangoni effect and surface plasmon polaritons (SPPs). We tune the coupled effect on Ge2Sb2Te5 films by adjusting the laser polarization, whose component controls the two effects' strength ratio. The Marangoni effect dominates when the SPPs' direction mismatches with the growing direction of nanogratings. Tuning this competition relationship helps to create nanogratings with tunable duty cycle and distribution, which are significant for light modulation applications. A highly efficient direct writing method with a line-shaped laser beam is employed to create large-area regular nanogratings by enhancing the effect tuning. We demonstrate diverse Au nanogratings with the aid of a lift-off operation and apply them in surface plasmon-coupled emission (SPCE), showcasing exceptional enhancement and narrowing performance.

Tecoma stans Floral Extract-Based Biosynthesis for Enhanced Surface Plasmon-Coupled Emission and a Preliminary Study on Fluoroimmunoassay.

We demonstrate the synthesis of biogenic supported silver spiked star architectures and their application to increase the electromagnetic field intensity at its tips that enhance plasmon-coupled emission. Tecoma stans floral extract has been used to synthesize silver nanocubes and spiked stars. We observe ∼445-fold and ∼680-fold enhancements in spacer and cavity configurations, respectively, in the SPCE platform. The hotspot intensity and Purcell factor are evaluated by carrying out finite-difference time-domain (FDTD) simulations. Time-based studies are presented to modulate the sharpness of the edges wherein an increase in the tip sharpness with the increase in reaction time up to 5 h is observed. The unique morphology of the silver architectures allowed us to utilize them in biosensing application. A SPCE-based fluoroimmunoassay was performed, achieving a 1.9 pg/mL limit of detection of TNF-α cytokine. This combination of anisotropic architectures, SPCE and immunoassay prove to be a powerful platform for the ultrasensitive detection of biomarkers in surface-bound assays.

Review of Gold Nanoparticles in Surface Plasmon-Coupled Emission Technology: Effect of Shape, Hollow Nanostructures, Nano-Assembly, Metal-Dielectric and Heterometallic Nanohybrids.

Point-of-care (POC) diagnostic platforms are globally employed in modern smart technologies to detect events or changes in the analyte concentration and provide qualitative and quantitative information in biosensing. Surface plasmon-coupled emission (SPCE) technology has emerged as an effective POC diagnostic tool for developing robust biosensing frameworks. The simplicity, robustness and relevance of the technology has attracted researchers in physical, chemical and biological milieu on account of its unique attributes such as high specificity, sensitivity, low background noise, highly polarized, sharply directional, excellent spectral resolution capabilities. In the past decade, numerous nano-fabrication methods have been developed for augmenting the performance of the conventional SPCE technology. Among them the utility of plasmonic gold nanoparticles (AuNPs) has enabled the demonstration of plethora of reliable biosensing platforms. Here, we review the nano-engineering and biosensing applications of AuNPs based on the shape, hollow morphology, metal-dielectric, nano-assembly and heterometallic nanohybrids under optical as well as biosensing competencies. The current review emphasizes the recent past and evaluates the latest advancements in the field to comprehend the futuristic scope and perspectives of exploiting Au nano-antennas for plasmonic hotspot generation in SPCE technology.

Visualizing lateral optical force through surface plasmon-coupled emission.

In this Letter, we report the intrinsic relationship among surface plasmon polaritons, lateral optical force, and surface plasmon-coupled emission. The spin-orbit coupling in the near field through circularly polarized beams would lead to the unidirectional excitation of surface plasmon polaritons, where the symmetry state of the electromagnetic field on the surface is broken. This asymmetric scattering would generate the counter-intuitive lateral optical force due to momentum conservation. As the inverse process of surface plasmon polaritons, surface plasmon-coupled emission enables the guide of the near-field surface plasmon polariton signal to the far field. We found that the lateral optical force produced by the unidirectional excitation of surface plasmon polaritons can be observed in the surface plasmon-coupled emission patterns. The elliptical dipole model was used to demonstrate these coupling processes. The magnitude and direction of lateral optical force can be a dipole, respectively. Moreover, the intensity convergence degree and direction of the surface plasmon-coupled emission distribution can reflect the magnitude and direction of lateral optical force, respectively. This work has great potential in the applications of weak force measurement, dynamic optical sorting, and light-matter interaction research.

Optical coupling of bio-inspired mustard protein-based bimetallic nanohybrids with propagating surface plasmon polaritons for femtomolar nitrite ion sensing: Cellphone-based portable detection device

Different classes of biologically and environmentally relevant molecules and ions are quantitatively and qualitatively analyzed using the synergistic approach wherein the properties of both the plasmonic nanomaterials and the fluorescent moieties are explored. In this study, such hybrid systems, called plasmophores (or plasmon coupled fluorophores), are investigated using the surface plasmon-coupled emission (SPCE) platform with silver, gold and silver-gold hybrid nano-structures synthesized via sustainable bio-inspired routes. A simple, rapid, user-friendly and green chemistry approach has been adopted using biocompatible mustard protein as both the reducing and capping agent during nanosynthesis. The morphologically and functionally tunable plasmonic nanomaterials were synthesized by simply exposing a mixture of the respective metal ions and protein to UV-light irradiation. Comprehensive analysis of the out-coupled spontaneous emission in the SPCE framework using spacer, cavity and extended cavity nanointerfaces yielded intriguing results, presenting optimum prerequisites for realizing high SPCE enhancements. More than a 950-fold improvement in the fluorescence signal intensity of rhodamine B was demonstrated utilizing the plasmonic cavity hotspots rendered by the hybrid coupling of the propagating surface plasmon polaritons of Ag with localized plasmon resonances of the bimetallic AgAu nanohybrids. The sharply directional and highly polarized SPCE enhancements, realized without increasing the illumination intensity, were utilized for quantitative detection of biologically relevant nitrite ions in drinking water samples at trace concentrations (limit of detection: 0.1 femtomolar). The applicability and relevance of the demonstrated method for sustainable use of plasmonic nanomaterials in photo-plasmonic research is presented by accomplishing the sensing using a cost-effective smartphone camera with a good correlation with the data obtained from a conventional detector system. Hence, the bio-nano-inspired strategy described here reveals several potential opportunities for the development of environmentally benign portable chemosensing devices for utility in academia and industry, especially for low-and-middle income countries.

Plasmon- and Waveguide-Coupled Fluorescence at the Ultraviolet Region.

Surface plasmon-coupled emission (SPCE) has been well studied for its coupled, directional, and enhanced P-polarized radiation due to the interactions of fluorophores with surface plasmon polaritons (SPPs) on thin metal films. Such surface plasmon polariton-assisted directional fluorescence has various applications in biosensing. Herein, we demonstrate 2-aminopurine (2AP, a UV-absorbing and -emitting fluorophore) emission coupling to modes in aluminum-based plasmon-coupled waveguides (Al-PCWs). Directional emission from 2-aminopurine on plasmon-coupled waveguides was observed at specific angles as P-polarized SPCE and/or as P- or S-polarized waveguide-coupled emission (WGCE). All S-polarized waveguide modes showed clear angularly resolved emission as compared to that of P-polarized surface plasmon-coupled emission or P-polarized waveguide-coupled emission. The coupling angles, efficiencies, and polarizations of the modes were sensitive to the optical properties and overall dimensions of the top dielectric layer in PCWs. The effective plasmon-coupled waveguide can consist of either a thin probe-containing layer on top of the undoped silica film, or a single dielectric PVA layer with probes distributed throughout the film on the Al layer. The former structures with probes confined to the top of the undoped silica layer showed much higher angular resolutions and coupling efficiencies, as well as mode-dependent changes in lifetimes. These results demonstrate that the plasmon and waveguide modes can be used for selective detection of surface-bound and bulk fluorophores, simultaneously.

Fluorescence enhancement of surface plasmon coupled emission by Au nanobipyramids and its modulation effect on multi-wavelength radiation

Surface plasmon coupled emission (SPCE), a novel surface-enhanced fluorescence technique, can generate directional and amplified radiation by the intense interaction between fluorophores and surface plasmons (SPs) of metallic nanofilms. For plasmon-based optical systems, the strong interaction between localized and propagating SPs and “hot spot” structures show great potential to significantly improve the electromagnetic (EM) field and modulate optical properties. Au nanobipyramids (NBPs) with two sharp apexes to enhance and restrict the EM field were introduced through electrostatic adsorption to achieve a mediated fluorescence system, and the emission signal enhancement was realized by factors over 60 compared with the normal SPCE. It has been demonstrated that the intense EM field produced by the NBPs assembly is what triggered the unique enhancement of SPCE by Au NBPs, which effectively overcomes the inherent signal quenching of SPCE for ultrathin sample detection. This remarkable enhanced strategy offers the chance to improve the detection sensitivity for plasmon-based biosensing and detection systems, and expand the range of applications for SPCE in bioimaging with more comprehensive and detailed information acquisition. The enhancement efficiency for various emission wavelengths was investigated in light of the wavelength resolution of SPCE, and it was discovered that enhanced emission for multi-wavelength could be successfully detected through the different emission angles due to the angular displacement caused by wavelength change. Benefit from this, the Au NBP modulated SPCE system was employed for multi-wavelength simultaneous enhancement detection under a single collection angle, which could broaden the application of SPCE in simultaneous sensing and imaging for multi-analytes, and expected to be used for high throughput detection of multi-component analysis.

Smartphone-Based Attomolar Cyanide Ion Sensing Using Au-Graphene Oxide Cryosoret Nanoassembly and Benzoxazolium-Based Fluorophore in a Surface Plasmon-Coupled Enhanced Fluorescence Interface

Photoplasmonic platforms are being demonstrated as excellent means for bridging nanochemistry and biosensing approaches at advanced interfaces, thereby augmenting the sensitivity and quantification of the desired analytes. Although resonantly coupled electromagnetic waves at the surface plasmon-coupled emission (SPCE) interface are investigated with myriad nanomaterials in order to boost the detection limits, rhodamine moieties are ubiquitously used as SPCE reporter molecules in spite of their well-known limitations. In order to overcome this constraint, in this work, a benzoxazolium-based fluorescent molecule, (E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]oxazol-3-ium iodide (DSBO), was synthesized to selectively detect the cyanide (CN-) ions in water samples. To this end, the sensitivity of the fabricated SPCE substrates is tested in spacer, cavity, and extended cavity nanointerfaces to rationalize the configurational robustness. The performance of the sensor is further improved with the careful engineering of gold (Au)-graphene oxide (GO) cryosoret nanoassemblies fabricated via an adiabatic cooling technology. The unique dequenching (turn-on) of the quenched (turn-off) fluorescent signal is demonstrated with the hybridized metal-π plasmon synergistic coupling in the nanovoids and nanocavities assisting delocalized Bragg and localized Mie plasmons. The spectro-plasmonic analysis yielded highly directional, polarized (>95%), and enhanced emission attributes with an attomolar limit of detection of 10 aM of CN- ions with high linearity (R2 = 0.996) and excellent reliability, in addition to an exceptional correlation with the theoretically obtained TFclac simulations. The CN- ion sensing is experimentally validated with the smartphone-based cost-effective SPCE detection technology to render the device amenable to resource-limited settings. We believe that the unique fluorophore-cryosoret nanoassemblage presented here encourages development of frugal, unconventional, and highly desirable strategies for the selective quantitation of environmentally and physiologically relevant analytes at trace concentrations for use in point-of-care diagnostics.

Plasmon-enhanced fluorescence from synergistic engineering of graphene oxide and sharp-edged silver nanorods mediated with castor protein for cellphone-based attomolar sensing

Environmentally benign plasmonic nanomaterials are increasingly used for sensing applications in nanophotonics and biomedical diagnostics. This study reports the utility of castor proteins as a unique biomaterial for plasmonic sensing application. We demonstrate an intriguing strategy to obtain rod-shaped silver nanoparticles (AgNPs) using biocompatible castor protein as both the reducing and capping agent in a frugal UV-light induced one-pot rapid synthesis. These AgNPs thus synthesized were juxtaposed with propagating surface plasmon polaritons of surface plasmon-coupled emission (SPCE) platform to generate the photo-plasmonic coupling phenomenon in the three nano-configurations of spacer, cavity, and extended cavity. Dramatically enhanced, sharply directional and distinctly polarized fluorescence enhancement was achieved using AgNPs on account of the sharp edges and pointed ends. The observed 1000-fold fluorescence enhancement is attributed to the hybrid coupling of the π-plasmons of graphene oxide (GO) with the AgNPs supporting lightning rod effect on account of the rod-shaped nano-morphology. Such realization of abundant plasmonic hotspots over the SPCE substrate assisted in attaining attomolar sensitivity. The performance of the subject platform was further validated using MATLAB simulations and user-friendly smartphone-based detector system for decentralizing the lab-confined biosensing architectures. We firmly believe that the eco-friendly method developed for nanosynthesis and the user-friendly technique demonstrated using smartphone technology would immensely benefit the biosensing approaches in resource-limited settings.

Biosensing Technologies: A Focus Review on Recent Advancements in Surface Plasmon Coupled Emission.

In the past decade, novel nano-engineering protocols have been actively synergized with fluorescence spectroscopic techniques to yield higher intensity from radiating dipoles, through the process termed plasmon-enhanced fluorescence (PEF). Consequently, the limit of detection of analytes of interest has been dramatically improvised on account of higher sensitivity rendered by augmented fluorescence signals. Recently, metallic thin films sustaining surface plasmon polaritons (SPPs) have been creatively hybridized with such PEF platforms to realize a substantial upsurge in the global collection efficiency in a judicious technology termed surface plasmon-coupled emission (SPCE). While the process parameters and conditions to realize optimum coupling efficiency between the radiating dipoles and the plasmon polaritons in SPCE framework have been extensively discussed, the utility of disruptive nano-engineering over the SPCE platform and analogous interfaces such as 'ferroplasmon-on-mirror (FPoM)' as well as an alternative technology termed 'photonic crystal-coupled emission (PCCE)' have been seldom reviewed. In light of these observations, in this focus review, the myriad nano-engineering protocols developed over the SPCE, FPoM and PCCE platform are succinctly captured, presenting an emphasis on the recently developed cryosoret nano-assembly technology for photo-plasmonic hotspot generation (first to fourth). These technologies and associated sensing platforms are expected to ameliorate the current biosensing modalities with better understanding of the biophysicochemical processes and related outcomes at advanced micro-nano-interfaces. This review is hence envisaged to present a broad overview of the latest developments in SPCE substrate design and development for interdisciplinary applications that are of relevance in environmental as well as biological heath monitoring.

Enhancement of NIR-triggered photocatalytic activity of Ln3+-doped NaYF4@SiO2/Ag@TiO2 nanospheres through synergistic upconversion and plasmonic effect

The multishell-structured NaYF4:Yb,Tm,Nd@NaYF4:Yb,Nd@SiO2/Ag@TiO2 (UC@SiO2/Ag@TiO2) nanospheres were prepared for the first time, which possessed the enhanced NIR-triggered photocatalytic activity under the synergistic effect of upconversion and plasmons. The design of active-core@active-shell structure for NaYF4:Yb,Tm,Nd@NaYF4:Yb,Nd upconversion nanophosphors (Yb/Tm/Nd@Yb/Nd UCNPs) significantly improved their upconversion luminescence (UCL) efficiency, which was increased by 12 times after coating a Yb/Nd shell on Yb/Tm/Nd seed crystals via epitaxial growth. After introduction of Ag nanoparticles, the UCL intensity of the obtained UC@SiO2/Ag was further enhanced by 3.3 times compared with the bare UCNPs because the plasmon resonance frequency of Ag overlapped with the visible emission peaks of UCNPs, which permitted an effective surface plasmon-coupled emission, resulting in the increase of emission intensity for UCNPs. Therefore, the final UC@SiO2/Ag@TiO2 could absorb the plasmon-enhanced NIR-to-UV/Vis lights from UCNPs to obtain its photocatalytic activity. Significantly, the photodegradation of Rhodamine B under the action of UC@SiO2/Ag@TiO2 was 26.9 % higher than that under the action of UC@SiO2@TiO2. UC@SiO2/Ag@TiO2 also exhibited a better photocatalytic antibacterial activity against B. subtilis than UC@SiO2@TiO2. In the presence of UC@SiO2/Ag@TiO2, bacteria were completely killed after 15 min of 808 nm NIR illumination. Finally, the possible photocatalytic mechanism of UC@SiO2/Ag@TiO2 was discussed based on the results of scavenger test.

Au-Ag Alloy Nanoshuttle Mediated Surface Plasmon Coupling for Enhanced Fluorescence Imaging.

Surface plasmon-coupled emission (SPCE), a novel signal enhancement technology generated by the interactions between surface plasmons and excited fluorophores in close vicinity to metallic film, has shown excellent performance in bioimaging. Variable-angle nanoplasmonic fluorescence microscopy (VANFM), based on an SPCE imaging system, can selectively modulate the imaging depth by controlling the excitation angles. In order to further improve the imaging performance, Au-Ag alloy nanoshuttles were introduced into an Au substrate to mediate the plasmonic properties. Benefiting from the strong localized plasmon effect of the modified SPCE chip, better imaging brightness, signal-to-background ratio and axial resolution for imaging of the cell membrane region were obtained, which fully displays the imaging advantages of SPCE system. Meanwhile, the imaging signal obtained from the critical angle excitation mode was also amplified, which helps to acquire a more visible image of the cell both from near- and far-field in order to comprehensively investigate the cellular interactions.

Three-dimensional imaging of biological cells using surface plasmon coupled emission.

.SignificanceBiological cell imaging has become one of the most crucial research interests because of its applications in biomedical and microbiology studies. However, three-dimensional (3D) imaging of biological cells is critically challenging and often involves prohibitively expensive and complex equipment. Therefore, a low-cost imaging technique with a simpler optical arrangement is immensely needed.AimThe proposed approach will provide an accurate cell image at a low cost without needing any microscope or extensive processing of the collected data, often used in conventional imaging techniques.ApproachWe propose that patterns of surface plasmon coupled emission (SPCE) features from a fluorescently labeled biological cell can be used to image the cell. An imaging methodology has been developed and theoretically demonstrated to create 3D images of cells from the detected SPCE patterns. The 3D images created from the different SPCE properties at the far-field closely match the actual cell structures.ResultsThe developed technique has been applied to different regular and irregular cell shapes. In each case, the calculated root-mean-square error (RMSE) of the created images from the cell structures remains within a few percentages. Our work recreates the base of a circular-shaped cell with an RMSE of . In addition, the images of irregular-shaped cell bases have an RMSE of . Finally, we obtained a 3D image with an RMSE of for a random cellular structure.ConclusionsDespite being in its initial stage of development, the proposed technique shows promising results considering its simplicity and the nominal cost it would require.

Refractive index sensing based on surface plasmon-coupled emission excited by reverse Kretschmann or Tamm structure.

Surface plasmon coupled emission (SPCE) is the directional emission of surface plasmon polaritons (SPPs) through the reverse channels of focused surface plasmon excitation to the far field, which has shown significant possibilities in bioanalysis, medical diagnosis, and so on. We carried out a theoretical study of SPCE to analyze its mechanisms and proposed a new structure to improve the emission intensity of SPCE. We proposed a method for refractive index sensing based on SPCE, consisting of a reverse Kretschmann (RK) or a Tamm structure for the first time, to the best of our knowledge. The corresponding sensing sensitivity reaches 87.61 deg/RIU and 67.44 deg/RIU, respectively. Compared with that in the RK, the far-field radiation intensity of SPCE in the Tamm structure is enhanced by two orders of magnitude. Furthermore, compared with surface plasmon resonance (SPR) sensing, SPCE sensing can improve the signal-to-noise ratio (SNR) and excitation efficiency. Our structures enable refractive index sensing with a high SNR, high spatial resolution, and without the requirement of angular alignment using complex mechanics, which are suitable for practical applications such as quantitative biomolecular detection and medical diagnosis.

Sericin-Based Bio-Inspired Nano-Engineering of Heterometallic AgAu Nanocubes for Attomolar Mefenamic Acid Sensing in the Mobile Phone-Based Surface Plasmon-Coupled Interface

Engineering photo-plasmonic platforms with heterometallic nanohybrids are of paramount significance for realizing augmented sensitivity in fluorescence-based analytical detection. Although myriad nanomaterials with versatile functionalities have been explored in this regard in the surface plasmon-coupled emission (SPCE) interface, light harvesting using nano-antennas synthesized via sustainable bio-inspired routes still remains a high priority in current research. Our study provides a rational design for in situ fabrication of nanoparticles of silver, gold, and their plasmonic hybrids using biocompatible, non-hazardous sericin protein (obtained Bombyx mori) as the reducing and capping agent. The one-pot, user-eco-friendly technology demonstrated here utilizes UV irradiation to promote the photo-induced electron transfer mechanism, thereby yielding nanomaterials of tunable optoelectronic functionalities. The resulting homometallic and heterometallic nanohybrids with robust localized surface plasmon resonances (LSPR) showed strong light-confining attributes when interfaced with the propagating surface plasmon polaritons (SPPs) of the SPCE platform, thereby yielding tunable, highly directional, polarized, and amplified fluorescence emission. The experimentally obtained emission profiles displayed an excellent correlation with the theoretically obtained dispersion diagrams validating the spectro-plasmonic results. The abundant hotspots from AgAu nanocubes presented in excess of 1300-fold dequenched fluorescence enhancement and were utilized for cost-effective and real-time mobile phone-based sensing of biologically relevant mefenamic acid at an attomolar limit of detection. We believe that this superior biosensing performance accomplished using the frugal bioinspired nano-engineering at hybrid interfaces would open new doors for developing nanofabrication protocols with the quintessential awareness of the principles of green nanotechnology, consequently eliminating hazardous chemicals and solvents in the development of point-of-care diagnostic tools.

Biocompatible Gellucire® Inspired Bimetallic Nanohybrids for Augmented Fluorescence Emission Based on Graphene Oxide Interfacial Plasmonic Architectures

Increased demand for high sensitivity techniques has resulted in a sustained search for sensing platforms that could provide reliable and highly sensitive detection of bio analytes and chemical species. Surface plasmon-coupled directional emission (SPCDE) has been explored as an alternative to conventionally used fluorescence detection methodologies to counter the inherent isotropic nature of this detection technique and increase its collection efficiency, thereby augmenting its sensitivity. This technology aids in realization of highly p-polarized emission with background suppression and excellent spectral resolution of emission profiles. The presented work explores the use of bimetallic nanohybrids synthesized through the one-pot synthesis in tandem with graphene oxide (GO) monolayer in spacer interface in the SPCDE platform to attain unprecedented emission enhancement of >1400-fold, opening the door to interfacial plasmonic architectures. Moreover, the use of biocompatible polymer Gellucire® for the synthesis of nanohybrids highlights the sustainable approach in this research work.

Label-Free Fluorescent Nanofilm Sensor Based on Surface Plasmon Coupled Emission: In Situ Monitoring the Growth of Metal-Organic Frameworks.

We have proposed a universal label-free fluorescent nanofilm sensor based on surface plasmon coupled emission (SPCE). A metal-dye-dielectric (MDD) structure was fabricated to mediate the label-free monitoring based on SPCE. The nonfluorescent dielectric film smartly borrowed the fluorescence signal from the bottom dye layer and led to a new SPCE response through the adjacent metal film. The fluorescence emission angle and polarization strongly depended on the thickness of the nonfluorescent dielectric film on the MDD structure. As a demonstration, the growth of a two-dimensional zeolitic imidazolate framework film (ZIF-L) was in situ monitored in the liquid phase by MDD-SPCE for the first time. The label-free fluorescent sensors are facilely prepared by a spin coating technique, with the potential to be widely spread for in situ studies, especially toward nanomaterial growth processes.

Cellphone-based attomolar tyrosine sensing based on Kollidon-mediated bimetallic nanorod in plasmon-coupled directional and polarized emission architecture

In the past decade, various interfacial materials have been explored for better sensor performance in nanoplasmonics. Despite gold being an ideal candidate for many plasmonic applications, its use in the field of surface plasmon-coupled emission (SPCE) platform is limited due to its inherent quenching phenomenon. Different methodologies have been reported to circumvent this limitation, albeit compromised by complex requirements. Moreover, the SPCE enhancement obtained hitherto remains inadequate and the use of biocompatible and eco-friendly sustainable methods in this direction has been rare. In this perspective, here we demonstrate a frugal and bio-friendly technique using ubiquitously available co-polymer kollidon® to obtain silver (Ag)-gold (Au) nanohybrids. The methodology involved is a simple, user-friendly and economical UV-induced one-pot green synthesis of hybrid architectures. The nanoparticles and nanohybrids obtained through this method were studied in three different nanointerfaces, namely: spacer, cavity and extended (ext.) cavity. Dequenched as well as in excess of 1000-fold enhancement in fluorescence was obtained in the ext. cavity nanointerface on account of hybrid plasmonic resonances. In addition to this, attomolar sensitivity was achieved for biologically important amino acid, tyrosine using a mobile phone-based detection technique. The methodology reported in this work provides a straightforward technique to obtain nanohybrids that can be used to dequench the otherwise quenched emission with new physicochemical insights, in addition to providing ample opportunities for development of next-gen mobile phone based hazardous analyte detection platforms using sustainable methodologies.

Integrated Photo-Plasmonic coupling of bioinspired Sharp-Edged silver Nano-particles with Nano-films in extended cavity functional interface for Cellphone-aided femtomolar sensing

Plasmonic silver nanoparticles (AgNPs) of anisotropic geometries are being increasingly explored in advanced functional nanointerfaces. Here, Ag nanocubes were synthesized using bioinspired and frugal approach with the use of proteins extracted from sesame oil seed cakes and UV-exposure methodology. The protein functions as both the reducing and capping agent via photo-induced electron transfer mechanism. The obtained AgNPs were evaluated in surface plasmon-coupled emission (SPCE) platform in different functional nanointerfaces. The augmented emission was utilized for cellphone-based femtomolar sensing of SPCE reporter molecule, rhodamine B (RhB). The user-eco-friendly approach developed here would be of utility for biosensing in resource-scarce settings.