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Exosome-templated nanoplasmonics for multiparametric molecular profiling
摘要： Exosomes are nanoscale vesicles distinguished by characteristic biophysical and biomolecular features; current analytical approaches, however, remain univariate. Here, we develop a dedicated platform for multiparametric exosome analysis—through simultaneous biophysical and biomolecular evaluation of the same vesicles—directly in clinical biofluids. Termed templated plasmonics for exosomes, the technology leverages in situ growth of gold nanoshells on vesicles to achieve multiselectivity. For biophysical selectivity, the nanoshell formation is templated by and tuned to distinguish exosome dimensions. For biomolecular selectivity, the nanoshell plasmonics locally quenches fluorescent probes only if they are target-bound on the same vesicle. The technology thus achieves multiplexed analysis of diverse exosomal biomarkers (e.g., proteins and microRNAs) but remains unresponsive to nonvesicle biomarkers. When implemented on a microfluidic, smartphone-based sensor, the platform is rapid, sensitive, and wash-free. It not only distinguished biomarker organizational states in native clinical samples but also showed that the exosomal subpopulation could more accurately differentiate patient prognosis.
关键词： molecular profiling,Exosomes,smartphone-based sensor,nanoplasmonics,biomarkers,microfluidic
更新于2025-09-23 15:21:01
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Selective Uropathogenic E. coli Detection Using Crossed Surface-Relief Gratings
摘要： Urinary tract infections (UTIs) are one of the major burdens on public healthcare worldwide. One of the primary causes of UTIs is the invasion of the urinary tract by uropathogenic Escherichia coli (UPEC). Improper treatment of bacterial infections like UTIs with broad-spectrum antibiotics has contributed to the rise of antimicrobial resistance, necessitating the development of an inexpensive, rapid and accurate detection of UPEC. Here, we present real-time, selective and label-free detection of UPEC using crossed surface-relief gratings (CSRGs) as nanometallic sensors incorporated into an optical sensing platform. CSRGs enable real-time sensing due to their unique surface plasmon resonance (SPR)-based light energy exchange, resulting in detection of a very-narrow-bandwidth SPR signal after the elimination of residual incident light. The platform’s sensing ability is experimentally demonstrated by the detection of bulk refractive index (RI) changes, with a bulk sensitivity of 382.2 nm/RIU and a resolution in the order of 10?6 RIU. We also demonstrate, for the ?rst time, CSRG-based real-time selective capture and detection of UPEC in phosphate-buffered saline (PBS) solution, in clinically relevant concentrations, as opposed to other UTI-causing Gram-negative bacteria. The platform’s detection limit is calculated to be 105 CFU/mL (concentration on par with the clinical threshold for UTI diagnosis), with a dynamic range spanning four orders of magnitude. This work paves the way for the development of inexpensive point-of-care diagnosis devices focusing on effective treatment of UTIs, which are a burden on public healthcare due to the rise in the number of cases and their recurrences in the recent past.
关键词： crossed surface-relief gratings,nanoplasmonics,surface plasmon resonance,urinary tract infection,biosensing,uropathogenic E. coli,surface-relief gratings
更新于2025-09-23 15:21:01
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Phenomena of Optical Metamaterials || Active Optical Metamaterials
摘要： At the turn of the century, a new field of research emerged at the crossing between physics, electrical engineering, and materials science. The study of metamaterials addresses the rational design and arrangement of a material’s building blocks to attain physical properties that may go significantly beyond those of its original constituent materials. Most often, the concept of metamaterials is associated with electromagnetic wave propagation, where the engineering of resonant subwavelength structures allows for the precise control of effective wave properties. It is this advanced functionality that enables the realization of unique wave phenomena, such as the focusing of light below the diffraction limit or electromagnetic cloaking of objects—concepts that have captured the imagination of researchers and the general public alike. Importantly, the element of functionality is an integral part of the metamaterial concept.
关键词： nanoplasmonics,plasmonics,negative refractive index,optical gain,metamaterials
更新于2025-09-23 15:21:01
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Plasmonic colored nanopaper: a potential preventive healthcare tool against threats emerging from uncontrolled UV exposure
摘要： Preventive healthcare is crucial to hinder or delay the onset of disease, furthermore it contributes to healthy and productive lifestyles and saves resources allocated to public health. Herein, we explore how the plasmonic coupling of silver and gold nanoparticles embedded within nanopaper allows for potential preventive healthcare tools based on a change in plasmonic color. Particularly, we selected UV radiation exposure as a potential threat to health to be monitored via plasmonic colored nanopaper (PCN). Uncontrolled UV radiation exposure is not only known to provoke epidermal damage, but also to trigger leaching of hazardous compounds from polycarbonate containers. In this context, we engineered UV-responsive PCN devices whose sensing mechanism is based on UV photodegradation of silver nanoparticles. Since absorbance and scattering of metal nanoparticles strongly depend on their size and inter-particle distance, the resulting PCN detectors are able to warn of the potential UV radiation-induced threat via a visually observable plasmonic color change with a yellowish/reddish transition. Epidermal experiments with tattoo-like PCN devices prove the resulting detectors can change in color upon safe dose of sun exposure. Moreover, PCN detectors stuck on polycarbonate containers also change in color after moderate sun exposure. This cost-effective and lightweight nanophotonic device leads to a versatile preventive healthcare tool.
关键词： smart packaging,nanoplasmonics,wearable devices,nanocellulose,nanophotonics
更新于2025-09-23 15:19:57
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Tents, Chairs, Tacos, Kites, and Rods: Shapes and Plasmonic Properties of Singly Twinned Magnesium Nanoparticles
摘要： Nanostructures of some metals can sustain light-driven electron oscillations called localized surface plasmon resonances, or LSPRs, that give rise to absorption, scattering, and local electric field enhancement. Their resonant frequency is dictated by the nanoparticle (NP) shape and size, fueling much research geared towards discovery and control of new structures. LSPR properties also depend on composition; traditional, rare and expensive noble metals (Ag, Au) are increasingly eclipsed by earth-abundant alternatives, with Mg being an exciting candidate capable of sustaining resonances across the ultraviolet, visible, and near-infrared spectral ranges. Here, we report numerical predictions and experimental verifications of a set of shapes based on Mg NPs displaying various twinning patterns including (10 1), (10 2), (10 3) and (11 1), that create tent, chair, taco and kite-shaped NPs, respectively. These are strikingly different from what is obtained for typical plasmonic metals because Mg crystallizes in a hexagonal close packed structure, as opposed to the cubic Al, Cu, Ag, and Au. A numerical survey of the optical response of the various structures, as well as the effect of size and aspect ratio, reveals their rich array of resonances, which are supported by single particle optical scattering experiments. Further, corresponding numerical and experimental studies of the near-field plasmon distribution via scanning transmission electron microscopy electron-energy loss spectroscopy unravels a mode nature and distribution that are unlike those of either hexagonal plates or cylindrical rods. These NPs, made from earth-abundant Mg, provide interesting ways to control light at the nanoscale across the ultraviolet, visible, and near-infrared spectral ranges.
关键词： nanoplasmonics,nanoparticle shape,magnesium nanoparticles,localized surface plasmon resonance,electron-energy loss spectroscopy,Wulff construction
更新于2025-09-23 15:19:57
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Discrete Source Method for the Study of Influence Nonlocality on Characteristics of the Plasmonic Nanolaser Resonators
摘要： The discrete source method is generalized so as to investigate the nonlocal effects in multilayered particles on a substrate. The scheme for constructing an approximate solution and the corresponding numerical algorithm are described in detail. The developed approach is used to study the optical characteristics of 3D cavities of plasmonic nanolasers. It is shown that the amplitude of surface plasmon resonance and the amplification factor of the near-field intensity are reduced significantly when the nonlocal effects are taken into account. It is also shown that the amplification factor can be increased by more than twice by varying the material and thickness of the cavity shell and the direction of the incident wave.
关键词： nanoplasmonics,quantum effect of nonlocality,discrete source method,plasmonic nanolaser (spaser)
更新于2025-09-23 15:19:57
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Plasmonic Metasurfaces Situated on Ultra-thin Carbon Nanomembranes
摘要： During the last decade, optical metasurfaces consisting of designed nanoresonators arranged in a planar fashion were successfully demonstrated to allow for the realization of a large variety of flat optical components. However, in common implementations of metasurfaces and metasurface-based devices, their flat nature is thwarted by the presence of a substrate of macroscopic thickness, which is needed to mechanically support the individual nanoresonators. Here, we demonstrate that Carbon Nanomembranes (CNMs) having nanoscale thickness can be used as a basis for arranging array of plasmonic nano-resonators into a metamembrane, allowing for the realization of genuinely flat optical devices. CNMs belong to the family of two-dimensional materials, and their thickness, mechanical, chemical, and electrical properties can be tailored by the choice of the molecular precursors used for their fabrication. We experimentally fabricate gold split-ring-resonator (SRR) metasurfaces on top of a free-standing CNM, which has a thickness of only about 1 nm and shows negligible interaction with the incident light field. For optical characterization of the fabricated SRR CNM metasurfaces, we perform linear-optical transmittance spectroscopy, revealing the typical resonance structure of an SRR metasurface. Furthermore, numerical calculations assuming free-standing SRR arrays are in excellent agreement with corresponding experimental transmittance spectra. We believe that our scheme offers a versatile solution for the realization of ultrathin, ultra lightweight metadevices, and may initiate various future research directions and applications including complex sensor technologies, conformal coating of complex topographies with functional metasurfaces, fast prototyping of multilayer metasurfaces, and studying the optical properties of effectively free-standing nanoparticles without the need for levitation schemes.
关键词： carbon nanomembranes,two-dimensional materials,nanoplasmonics,flat-optics,metasurfaces
更新于2025-09-19 17:13:59
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Electromagnetic simulation of MXene-based plasmonic metamaterials with enhanced optical absorption
摘要： In this contribution we propose, design and numerically analyze a plasmonic metamaterial for enhanced optical absorption, based on 100 nm thick titanium carbide (Ti3C2Tx) MXene sheets. The analyzed metamaterial is built as a sandwich with a solid MXene bottom (ground) layer, a lossless dielectric middle layer and an MXene mesh top layer. The unit cell of the periodic top mesh consists of two crossed ultrathin MXene strips, each of them spreading its width in step-like increments towards the middle of the unit cell. This ensures position-variable width of the top surface apertures, resulting in a widening of the bandwidth of spectral dispersion of the scattering parameters of the obtained metamaterial. We utilize the finite element method to simulate the scattering parameters of the MXene-based metamaterial. We apply Drude–Lorentz model to derive our analytical expression for complex permittivity of Ti3C2Tx MXene based on experimental measurements. The described approach is general, since various alternative plasmonic materials can be utilized, including different MXenes, but other materials as well, such as graphene, metals and metal alloys, semiconductors, etc. The approach is applicable to various other nanoplasmonic structures. In this manner the available toolbox for plasmonics is extended and a new degree of design freedom ensured.
关键词： MXenes,Superabsorbers,Nanoplasmonics,Electromagnetic simulation,Metamaterials
更新于2025-09-19 17:13:59
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Nonlinear absorption and scattering of a single plasmonic nanostructure characterized by <i>x</i> -scan technique
摘要： Nonlinear nanoplasmonics is a largely unexplored research area that paves the way for many exciting applications, such as nanolasers, nanoantennas, and nanomodulators. In the field of nonlinear nanoplasmonics, it is highly desirable to characterize the nonlinearity of the optical absorption and scattering of single nanostructures. Currently, the common method to quantify optical nonlinearity is the z-scan technique, which yields real and imaginary parts of the permittivity by moving a thin sample with a laser beam. However, z-scan typically works with thin films, and thus acquires nonlinear responses from ensembles of nanostructures, not from single ones. In this work, we present an x-scan technique that is based on a confocal laser scanning microscope equipped with forward and backward detectors. The two-channel detection offers the simultaneous quantification for the nonlinear behavior of scattering, absorption and total attenuation by a single nanostructure. At low excitation intensities, both scattering and absorption responses are linear, thus confirming the linearity of the detection system. At high excitation intensities, we found that the nonlinear response can be derived directly from the point spread function of the x-scan images. Exceptionally large nonlinearities of both scattering and absorption are unraveled simultaneously for the first time. The present study not only provides a novel method for characterizing nonlinearity of a single nanostructure, but also reports surprisingly large plasmonic nonlinearities.
关键词： nonlinear absorption,absorption cross section,nonlinear scattering,single gold nanostructures,laser scanning microscopy,nanoplasmonics
更新于2025-09-16 10:30:52
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Augmented COlorimetric NANoplasmonic (CONAN) Method for Grading Purity and Determine Concentration of EV Microliter Volume Solutions
摘要： This protocol paper describes how to assign a purity grade and to subsequently titrate extracellular vesicle (EV) solutions of a few microliters in volume by microplate COlorimetric NANoplasmonic (CONAN) assay. The CONAN assay consists of a solution of gold nanoparticles (AuNPs) into which the EV preparation is added. The solution turns blue if the EV preparation is pure, whereas it stays red if soluble exogenous single and aggregated proteins (SAPs; often referred to as protein contaminants) are present. The color change is visible by the naked eye or can be quantified by UV-Vis spectroscopy, providing an index of purity (a unique peculiarity to date). The assay specifically targets SAPs, and not the EV-related proteins, with a detection limit <50 ng/μl (an order of magnitude higher resolution than that of the Bradford protein assay). For pure solutions, the assay also allows for determining the EV number, as the color shift is linearly dependent on the AuNP/EV molar ratio. Instead, it automatically reports if the solution bears SAP contaminants, thus avoiding counting artifacts. The CONAN assay proves to be robust and reliable and displays very interesting performances in terms of cost (inexpensive reagents, run by standard microplate readers), working volumes (1–2 μl of sample required), and time (full procedure takes <1 h). The assay is applicable to all classes of natural and artificial lipid microvesicles and nanovesicles.
关键词： extracellular vesicles,particle number,nanoplasmonics,titration,liposomes,synthetic vesicles,nanoparticles,purity
更新于2025-09-16 10:30:52