Explore the vast range of titles available.

We report the enhanced photoluminescence of carbon dots formed in situ on silver gratings via plasmonic reduction of a carbonaceous seed layer. This layer transforms into photoluminescent carbon dots in a non‐oxygenated environment, catalyzed by surface plasmon polaritons (SPPs) excited on the grating by a pump laser, as monitored in real‐time via Raman scattering. Pump SPPs subsequently excite the carbon dots, which emit at longer wavelengths into the local electromagnetic environment, which is dominated by SPPs propagating on and diffracting from the grating. We experimentally observe SPP‐enhanced photoluminescence as a significant reduction in the lifetime of the emitters, and as induced coherence in far‐field emission. Purcell factors of ∼70 are deduced from lifetimes of ∼30 ps for carbon dots measured using time‐correlated single‐photon counting. SPPs accelerate radiative decay and produce polarized directional free‐space emission via grating diffraction, conferring characteristics of coherence to a random arrangement of luminescent carbon dots. A method for modeling an ensemble of random, incoherent emitters using finite‐difference time‐domain (FDTD) simulations is proposed, and the results agree with observed far‐field images and measured Purcell factors. Our results provide insight into carbon dot ‐ SPP interactions and have implications for cavity‐enhanced biosensors, quantum emitters, and carbon‐based light sources. Carbon emitters formed in situ on a silver grating via plasmonic catalysis yield enhanced spontaneous emission by preferential radiative decay into surface plasmons. Enhancement manifests as emission exhibiting characteristics of coherence (polarization, directionality), and accelerated lifetimes of ∼30 ps, yielding Purcell factors of ∼70. Findings have implications for cavity‐enhanced biosensors, quantum light sources, and carbon‐based light emitters.

The photophysical properties of single-molecule emitters are altered by nanophotonic structures such as single plasmonic nanoparticles. The intensity and spectral properties of plasmon-coupled emitters have been studied extensively, but little is known about the effect of plasmon coupling on emission polarization. Here, we examine how particle-emitter coupling modifies the polarization of single fluorophores in both experiment and simulation. We quantify degree of linear polarization using Stokes polarimetry with a polarization-sensitive camera and quantify the Stokes parameters with a single-shot acquisition without requiring additional optics in the detection path. We then perform polarization-resolved measurements of plasmon-coupled fluorescence from single-molecule emitters using an approach based on DNA-PAINT. We quantify the effect of the setup and associated noise sources on the measured Stokes parameters. We then quantify the angle of linear polarization (AoLP) and the degree of linear polarization (DoLP) for thousands of single molecules. We compare our results to a numerical model that propagates the plasmon-coupled single-molecule emission through the optical setup to yield the polarized point spread function in the camera plane. Simulations and experiments are in good agreement and shed new light on the polarization of antenna-coupled fluorophores, while it establishes single-shot polarimetry as a promising and straightforward method to quantify polarization properties at the single-molecule level.

Analysing dynamics of a single biomolecule using high-resolution imaging techniques has been had significant attentions to understand complex biological system. Among the many approaches, vertical nanopillar arrays in contact with the inside of cells have been reported as a one of useful imaging applications since an observation volume can be confined down to few-tens nanometre theoretically. However, the nanopillars experimentally are not able to obtain super-resolution imaging because their evanescent waves generate a high optical loss and a low signal-to-noise ratio. Also, conventional nanopillars have a limitation to yield 3D information because they do not concern field localization in -axis. Here, we developed novel hybrid nanopillar arrays (HNPs) that consist of SiO nanopillars terminated with gold nanodisks, allowing extreme light localization. The electromagnetic field profiles of HNPs are obtained through simulations and imaging resolution of cell membrane and biomolecules in living cells are tested using one-photon and 3D multiphoton fluorescence microscopy, respectively. Consequently, HNPs present approximately 25 times enhanced intensity compared to controls and obtained an axial and lateral resolution of 110 and 210 nm of the intensities of fluorophores conjugated with biomolecules transported in living cells. These structures can be a great platform to analyse complex intracellular environment.

The pervasive environmental contamination by micro- and nanoplastics (MNPs) presents a formidable analytical challenge, necessitating the development of rapid and sensitive detection methods. While conventional techniques often suffer from limitations in sensitivity and throughput, fluorescent probe-based technology has emerged as a powerful alternative. This review charts the evolution of these probes, from initial stains relying on hydrophobic adsorption to advanced molecular designs engineered for specific chemical recognition. We critically examine key operational mechanisms, including the solvatochromic response of Nile Red, polarity-discriminatory probes enabling a “microplastic rainbow,” and targeted systems achieving turn-on fluorescence via restriction of intramolecular rotation. Furthermore, we highlight cutting-edge signal enhancement strategies, such as plasmon- and metal-enhanced fluorescence, which amplify detection to the femtogram level. Special emphasis is placed on the distinct challenges posed by nanoplastics, including their propensity for aggregation in aqueous matrices that exacerbates false positives and their superior ability to breach biological barriers, and how AIE luminogens and PEF/MEF strategies mitigate these issues through enhanced signal-to-noise ratios and subcellular resolution, differing from their application to microplastics. Critically, we address the imperative for low-toxicity probe designs, emphasizing biocompatibility and biodegradability criteria to facilitate safe, long-term in vivo tracking and widespread ecological surveillance. The integration of these sophisticated probes with smart, “activate-on-target” systems is paving the way for next-generation MNP analysis, offering critical insights for environmental monitoring and toxicological assessment.

Ellagic acid (EA), as a natural polyphenolic acid, is considered a naturally occurring inhibitor of carcinogenesis. Herein, we developed a plasmon-enhanced fluorescence (PEF) probe for EA detection based on silica-coated gold nanoparticles (Au NPs). A silica shell was designed to control the distance between silica quantum dots (Si QDs) and Au NPs. The experimental results indicated that an 8.8-fold fluorescence enhancement was obtained compared with the original Si QDs. Three-dimensional finite-difference time-domain (3D-FDTD) simulations further demonstrated that the local electric field enhancement around Au NPs led to the fluorescence enhancement. In addition, the fluorescent sensor was applied for the sensitive detection of EA with a detection limit of 0.14 μM. It can be used to detect EA in pomegranate rind with a recovery rate of 100.26–107.93%. It can also be applied to the analysis of other substances by changing the identification substances. These experimental results indicated that the probe provides a good option for clinical analysis and food safety. Graphical Abstract

In this manuscript, silver nanowire 3D random crossed-wire woodpile (3D-RCW) nanostructures were designed and prepared. The 3D-RCW provides rich “antenna” and “hot spot” effects that are responsive for surface-enhanced Raman scattering (SERS) effects and plasmon-enhanced fluorescence (PEF). The optimal construction mode for the 3D-RCW, based on the ratio of silver nanowire and control compound R6G, was explored and established for use in PEF and SERS analyses. We found that the RCW nanochip capable of emission and Raman-enhanced detections uses micro levels of analysis volumes. Consequently, and SERS and PEF of pesticides (thiram, carbaryl, paraquat, fipronil) were successfully measured and characterized, and their detection limits were within 5 μM~0.05 µM in 20 µL. We found that the designed 3D plasmon-enhanced platform cannot only collect the SERS of pesticides, but also enhance the fluorescence of a weak emitter (pesticides) by more than 1000-fold via excitation of the surface plasmon resonance, which can be used to extend the range of a fluorescence biosensor. More importantly, solid-state measurement using a 3D-RCW nanoplatform shows promising potential based on its dual applications in creating large SERS and PEF enhancements.

A plasmon-enhanced fluorescence-based antibody-aptamer biosensor — consisting of gold nanoparticles randomly immobilized onto a glass substrate via electrostatic self-assembly — is described for specific detection of proteins in whole blood. Analyte recognition is realized through a sandwich scheme with a capture bioreceptor layer of antibodies — covalently immobilized onto the gold nanoparticle surface in upright orientation and close-packed configuration by photochemical immobilization technique (PIT) — and a top bioreceptor layer of fluorescently labelled aptamers. Such a sandwich configuration warrants not only extremely high specificity, but also an ideal fluorophore-nanostructure distance (approximately 10–15 nm) for achieving strong fluorescence amplification. For a specific application, we tested the biosensor performance in a case study for the detection of malaria-related marker Plasmodium falciparum lactate dehydrogenase ( Pf LDH). The proposed biosensor can specifically detect Pf LDH in spiked whole blood down to 10 pM (0.3 ng/mL) without any sample pretreatment. The combination of simple and scalable fabrication, potentially high-throughput analysis, and excellent sensing performance provides a new approach to biosensing with significant advantages compared to conventional fluorescence immunoassays. Graphical abstract

A phenomenon of plasmon-enhanced fluorescence (PEF) arises from interactions between fluorophores and metal nanostructures, leading to a substantial amplification of the fluorescence signal. Herein, we report a magnetic field (MF) induced on-demand PEF from the magnetoplasmonic nanoplatform and demonstrate its application in near infrared (NIR) bioimaging. The developed magnetoplasmonic nanoparticles (~ 50 nm diameter) feature a core-shell-satellite architecture comprising a Fe 3 O 4 magnetic core, a mesoporous silica (mSiO 2 ) shell housing IR775-silane NIR dye, and surface-anchored gold (Au) seeds (satellites). Application of an external MF causes the magnetophoretic movement and aggregation of the nanoparticles (NPs), resulting in a formation of localized plasmonic hotspots and, consequently, in a plasmonic enhancement of NIR fluorescence from IR775 dye molecules. Correspondingly, a substantial reduction of the fluorescence lifetime in the MF-treated area was observed, in addition to the enhanced fluorescence intensity. In vivo studies with NPs subcutaneously injected into mice revealed MF-activated amplification of NiR fluorescence. At 6 h post-injection, the injected region treated by MF exhibited 2.1-fold stronger NIR fluorescence signal than the MF-untreated one; the fluorescence enhancement correlated with the reduction of the emission lifetime (from 0.68 ns to 0.47 ns). At 96 h post-injection, the MF-treated region exhibited 6.8-fold more intense NIR fluorescence. Histological analysis showed absence of toxicity from the injected NPs, revealing their biocompatibility. Hence, a considerable potential of MF-induced PEF with the magnetoplasmonic nanoplatform for targeted NIR fluorescence bioimaging was demonstrated. This work also introduces MF-induced PEF as a powerful strategy for spatiotemporal control of optical signals, offering new opportunities for targeted imaging and sensing. Graphical abstract

We investigate the fluorescence from submonolayer rhodamine 6G molecules near gold nanoparticles (NPs) at a well-controlled poly (methyl methacrylate) (PMMA) interval thickness from 1.5 to 21 nm. The plasmonic resonance peaks of gold NPs are tuned from 530 to 580 nm by the PMMA spacer of different thicknesses. Then, due to the plasmonic resonant excitation enhancement, the emission intensity of rhodamine 6G molecules at 562 nm is found to be enhanced and shows a decline as the PMMA spacer thickness increases. The variation of spectral intensity simulated by finite-difference time-domain method is consistent with the experimental results. Moreover, the lifetime results show the combined effects to rhodamine 6G fluorescence, which include the quenching effect, the barrier effect of PMMA as spacer layer and the attenuation effect of PMMA films.