Plasmonic Nanoparticles Research Articles

Ultra-Sensitive Abscisic Acid Detection Using Gold and 4-Mercaptopyridine Perovskite-Engineered Robust Nanofibers (GLAMPER-NFs) under Surface-Enhanced Raman Spectroscopy.

This study explores the development and application of gold and 4-mercaptopyridine (MPY) perovskite-engineered robust nanofibers (GLAMPER-NFs) for the ultrasensitive detection of Abscisic acid (ABA) under Raman spectroscopy, a crucial plant hormone. The GLAMPER-NFs composite material, consisting of MAPbCl3 nanofibers integrated with MPY-coated gold nanostructures, demonstrates exceptional performance in surface-enhanced Raman scattering (SERS)-based sensing. The study elucidates the material structure and properties through comprehensive characterization using scanning electron microscopy (SEM), UV-vis spectroscopy, fluorescence spectroscopy, Fourier transform infrared, and Raman spectroscopy. The SEM analysis reveals uniform nanofibers with diameter of 107.8 ± 3.06 nm, while spectroscopic studies confirm the successful synthesis and integration of the composite components. The SERS-based detection of ABA showcases remarkable sensitivity, with a linear detection range (R2 = 0.9957) spanning 7 orders of magnitude (10-14-10-7 M) and presented a limit of detection of 10-11 and enhancement factor of 1.08 × 107. This surpasses the performance of existing sensing platforms, demonstrating clear spectral responses even at femtomolar concentrations. The synergistic effects of the perovskite structure, plasmonic gold nanoparticles, and MPY linking molecules contributed exceptional sensing capabilities to the GLAMPER-NFs material. Fluorescence studies further corroborate the sensitivity and provide insights into the photophysical interactions between ABA and the composite material. This research advances the understanding of perovskite-based hybrid materials and presents a promising GLAMPER-NFs as SERS substrate for ultrasensitive plant hormone detection, with potential applications in agricultural monitoring and plant science research.

Manipulating Near-Infrared Absorption via Engineering Anisotropic Plasmonic Spiky Au Nanocubes for the Highly Efficient Dual-Response Immune Detection of T-2 Toxin.

Integrating specific immune recognition, a desirable extinction coefficient, and conspicuous photothermal conversion ability into a single-immune probe to enhance the analysis performance represents an appealing yet significantly challenging task. Herein, by delicately manipulating the geometry of plasmonic nanoparticles from spherical to spiky, precise engineering approach-based spiky Au nanocubes (S-AuNCs) are employed to address this challenge, which fully exploits the plasmon resonance absorption-induced photothermal effect. The finite difference time domain (FDTD) method was employed to computationally simulate the electromagnetic and thermal fields while assessing the feasibility of regulating plasmon resonance for enhanced photothermal absorption. The optimized noble photothermal agent simultaneously exhibits acceptable near-infrared absorption (NIR), a significantly increased 808 nm extinction coefficient (145 times higher than that of AuNPs), favorable antibody coupling ability, and desirable photothermal conversion behavior. Consequently, the satisfactory performance of the S-AuNCs-guided colorimetric and photothermal lateral flow immunoassay (CPLFIA) is demonstrated for the sensitive detection of T-2 toxin. In comparison to spherical AuNPs (35.2 pg/mL), the dual-mode detection sensitivity was enhanced by 1.862-fold and 5.18-fold, respectively, achieving limits of detection at 18.9 pg/mL (colorimetric mode) and 6.8 pg/mL (photothermal mode). Therefore, S-AuNCs-guided CPLFIA holds great potential in advancing food mycotoxin safety control.

Metal-Enhanced Luminescence of Core-Shell Au@ Resorcinol-Formaldehyde Resin Nanospheres for Oxygen Sensing.

Luminescence-based detection has attracted widespread interests in oxygen measurement applications due to its great versatility, simplicity, sensitivity and non-invasive measurement. However, the relatively low quantum efficiency prompts a need for developing methods for luminescent enhancement. Plasmonic nanoparticles are known to efficiently enhance emission of the surrounding dyes with a precise inter-distance of nanoparticles and dyes. Here, we reported a novel plasmon-enhanced luminescence system in which the distance between luminescence dyes (PtTFPP) and metal nanoparticles (Au nanospheres, AuNSs) can be tuned by an organic spacer of Resorcinol-Formaldehyde (RF) to investigate the separation dependence on the emission enhancement in the optical oxygen sensors. A maximum enhancement of up to 6.24-fold has been achieved with a 5nm thick spacer in the PtTFPP-based oxygen sensors. These findings provide a unique platform for exploring the application of metal-enhanced luminescence (MEL) in luminescence-based measurement for oxygen concentration.

Study of plasmonic silver nanoparticles synthesized by conventional and eco-friendly methods with ultraviolet irradiation

The synthesis of some silver nanoparticles was carried out by twostep reduction, with chemical or biological antioxidants, and subsequent exposure to ultraviolet radiation. Synthesis efficiency was progressively increased after 30 min during second step: about 40% increase of LSPR band intensity for chemical reducing and more than 100% enhancing for biological reducing.

NUMERICAL METHOD FOR SOLVING OF THE DIFFRACTION PROBLEM DESCRIBED BY MAXWELL’S EQUATIONS WITH MESOSCOPIC BOUNDARY CONDITIONS

A numerical method for solving the diffraction boundary problem for the system of Maxwell’s equations with mesoscopic boundary conditions has been developed and implemented. It is based on the discrete source method. A numerical analysis of the influence of surface quantum effects on the optical characteristics of plasmonic nanoparticles is carried out. It has been established that surface effects have a significant impact on the field characteristics, and the results differ significantly from the case of volumetric effects.

Fabrication and Characterization of Supported Porous Au Nanoparticles

Porous plasmonic nanoparticles offer unique advantages for sensing and catalysis due to their high surface-to-volume ratio and localized electromagnetic field enhancements at nanoscale pores, or “hotspots.” However, current fabrication techniques, which are based on colloidal synthesis, face challenges in achieving precise control over particle size, shape, and porosity. Here, we present a robust nanofabrication method to produce supported arrays of porous Au nanoparticles with excellent dimensional and compositional control. By combining lithographically patterned AuAg alloy nanoparticles and selective dealloying via nitric acid, we achieve particle porosity without compromising particle morphology. Specifically, the method allows fabrication of supported porous nanoparticles with tunable dimension and porosity. Our approach demonstrates precise control of nanoparticle porosity by varying the initial Ag content in the alloy. Optical characterization reveals a blueshift in the extinction peak with increasing porosity, attributed to the reduced effective refractive index from intraparticle voids. Notably, a tunable shift of up to 100 nm in the plasmonic peak is observed, demonstrating the potential for fine-tuning optical properties. This study highlights the versatility of the proposed method in fabricating well-defined porous plasmonic nanoparticles and their ability to modulate optical properties through porosity control. These findings not only expand the toolkit for designing advanced plasmonic materials but also open pathways for applications in plasmon-mediated sensing, catalysis, and photonic devices.

Sustainable Fabrication and Transfer of High-Precision Nanoparticle Arrays Using Recyclable Chemical Pattern Templates.

Nanoparticle (NP) arrays, particularly those with plasmonic properties, have diverse applications in electronics, photonics, catalysis, and biosensing, but their precise and scalable fabrication remains challenging. In this work, a facile chemical-based strategy is presented for the fabrication of precise NP patterns using a combination of soft thermal nanoimprinting and template-directed assembly. The approach enables the creation of well-defined NP arrays with single-particle resolution and yields over 99%, covering a diverse range of NP sizes from 30 to 150nm. These patterns can be transferred onto various substrates including semiconductors, insulators, 2D materials, and flexible polymers, maintaining high uniformity and repeatability for over 60 cycles with minimal degradation. Moreover, the method enables the fabrication of extensive NP arrays up to 1 cm2 with a positional accuracy of ±11 nm for 30nm NPs. As a result, the obtained silver NP arrays exhibit ultranarrow surface lattice resonances with a linewidth of 4nm and a quality factor (Q) of 216. The method offers new avenues for the creation of plasmonic NP arrays for flexible and wearable devices.

Crystalline Assemblies of DNA Nanostructures and Their Functional Properties

AbstractSelf‐assembly presents a remarkable approach for creating intricate structures by positioning nanomaterials in precise locations, with control over molecular interactions. For example, material arrays with interplanar distances similar to the wavelength of light can generate structural color through complex interactions like scattering, diffraction, and interference. Moreover, enzymes, plasmonic nanoparticles, and luminescent materials organized in periodic lattices are envisioned to create functional materials with various applications. Focusing on structural DNA nanotechnology, here, we summarized the recent developments of two‐ and three‐dimensional lattices made purely from DNA nanostructures. We review DNA‐based monomer design for different lattices, guest molecule assembly, and inorganic material coating techniques and discuss their functional properties and potential applications in photonic crystals, nanoelectronics, and bioengineering as well as future challenges and perspectives.

Label-Free Surface-Enhanced Raman Spectroscopy Detection of Amyloid Beta on Silver Nanostructured Substrates for Alzheimer's Diagnosis.

Alzheimer's disease (AD) is a public health concern, for which an early diagnosis is essential. Biomass-derived carbon fibres with surface-decorated silver nanoparticles (Ag@CFs) have been utilized as surface enhanced raman spectroscopy (SERS) sensor platformfor the detection of the amyloid beta Aβ (25-35) for the pre-diagnosis of Alzheimer's disease. Structural and morphological characterizations confirmed the distribution of plasmonic silver nanoparticles over the surface of carbon fibres. The SERS sensor performance of Ag@CFs was evaluated using rhodamine 6G, which showed an enhancement of the order of 106 which proved the effectiveness of the developed SERS sensor towards trace level detection of analyte. A range of amyloid beta concentrations, from 100uM to 10pM, have been analyzed as a proof-of concept for this study, showcasing the efficacy of the Ag@CFs based SERS sensor to detect trace level concentrations of amyloid beta, even as low as 10 pM. This investigation is a promising development in the field of AD diagnostics since it may turn out to be a non-invasive, economical and early diagnostic tool.

Gold-coated silver nanorods on side-polished singlemode optical fibers for remote sensing at optical telecommunication wavelengths

The lower refractive index sensitivity (RIS) of plasmonic nanoparticles (NP) in comparison to their plasmonic thin films counterparts hindered their wide adoption for wavelength-based sensor designs, wasting the NP characteristic field locality. In this context, high aspect-ratio colloidal core-shell Ag@Au nanorods (NRs) are demonstrated to operate effectively at telecommunication wavelengths, showing RIS of 1720 nm/RIU at 1350 nm (O-band) and 2325 nm/RIU at 1550 nm (L-band), representing a five-fold improvement compared to similar Au NRs operating at equivalent wavelengths. Also, these NRs combine the superior optical performance of Ag with the Au chemical stability and biocompatibility. Next, using a side-polished optical fiber, we detected glyphosate, achieving a detection limit improvement from 724 to 85 mg/L by shifting from the O to the C/L optical bands. This work combines the significant scalability and cost-effective advantages of colloidal NPs with enhanced RIS, showing a promising approach suitable for both point-of-care and long-range sensing applications at superior performance than comparable thin film-based sensors in either environmental monitoring and other fields.

Hierarchical structure design of MoS2/PDA/Ag-hybrid hydrogel system enhances all-environment solar water purification

As a promising and sustainable way for freshwater production, interfacial solar vapor generation technology often encounters harsh conditions such as fluctuating illumination, high salinity, bacterial growth, and acid/alkali corrosion, which can reduce its conversion efficiency and lifespan. Here, to address these challenges, an environmentally adaptive hierarchical structure incorporating plasmonic Ag nanoparticles, MoS2 nanoflowers, and polydopamine (PDA) (MoS2@PDA/Ag) within a hybrid hydrogel matrix was designed as the functional solar evaporator. By systematically adjusting the volume ratio of cellulose nanofibers (CNF) and polyvinyl alcohol (PVA) skeletons, high evaporation efficiencies can be achieved in hypersaline conditions. Further, the cooperation of multi-photothermal materials endows the evaporator with a broad light absorption spectrum, superior photothermal conversion efficiency, and strong antimicrobial capabilities. The evaporator demonstrates a high evaporation rate of 2.79 kg m-2 h−1 under 1 sun irradiation and maintains sustainable evaporation for 8 h without salt deposition in 20 % NaCl solution. After being immersed in an acidic and alkaline seawater environment for 30 days, the evaporator shows no change in appearance, with only a slight decrease in performance. This work presents a promising platform for the development of solar evaporators with practical applications in various environmental conditions.

Successively enhanced photoelectrochemical performance from plasmonic Au nanoparticles decorated Ta3N5-TiO2 heterostructure

Semiconductor-based photocatalysts innovation and heterojunction design incorporating novel materials have shed light on the enhancement of the photoelectrochemical performances concerning energy fields, among which the plasmonic metal/semiconductor nanostructure raised extensive research attentions due to further PEC performance enhancement. In this work, an innovatively sandwiched structure composed of Ta3N5 nanorods/ultrathin TiO2/Au nanoparticles was designed with successive PEC enhancement. The successful combination between the Ta3N5 nanorods and the dielectric TiO2 layer represented carriers’ migration, in addition with the heterojunction between TiO2 and Au NPs contributed to the synergistically suppression of the charge carriers’ recombination. Au NPs could further serve as the plasmonic absorber underlying their localized surface plasma resonance effect, expanding the light absorption over the whole visible range, and inducing hot electrons injection to the TiO2 layer effectively. The hierarchical performance improvement via surface plasmon enhanced photoelectrochemical activity in the well-designed heterostructure propose strong potential for the development of novel photocatalysts.

Considerations for electromagnetic simulations for a quantitative correlation of optical spectroscopy and electron tomography of plasmonic nanoparticles

Abstract The optical cross sections of plasmonic nanoparticles are intricately linked to their morphologies. Accurately capturing this link could allow determination of particles’ shapes from their optical cross sections alone. Electromagnetic simulations bridge morphology and optical properties, provided they are sufficiently accurate. This study examines key factors affecting simulation precision, comparing common methods and detailing the impacts of meshing accuracy, dielectric function selection, and substrate inclusion within the boundary element method. To support the method’s complex parameterization, we develop a workflow incorporating reconstruction, meshing, and mesh simplification, to enable the use of electron tomography data. We analyze how choices of reconstruction algorithm and image segmentation affect simulated optical cross sections, relating these to shape errors minimized during data processing. Optimal results are obtained using the total variation minimization (TVM) reconstruction method with Otsu thresholding and light smoothing, ensuring reliable, watertight surface meshes through the marching cubes algorithm, even for complex shapes.

A simple colorimetric detection of telomerase exploiting specific cleavage of exonuclease III coupled with telomeric DNA controlled aggregation of nanogold.

Telomerase activity has piqued scientists' interest for the reason that it has the potential to be employed for early-stage cancer detection, anticancer therapy and studies related to cancer progression and metastasis. Several approaches have been developed to detect telomerase activity. However, these approaches were lengthy, challenging to quantify, of limited sensitivity and prone to polymerase chain reaction (PCR)-related artefacts. We herein developed a novel nanoplasmonic sensing platform for colorimetric detection of telomerase activity relying on the telomere elongation of telomerase at the 3' end, structure-specific cleavage activity of exonuclease III that removes mononucleotides from the 3'-hydroxyl termini of double-stranded DNA, and electrostatic interaction of elongated telomeres with plasmonic nanoparticles. Using HeLa cells as a model for colorimetric detection of telomerase activity, this biosensor could detect telomerase activity with a detection limit of ∼100 cells per reaction by visible inspection and ∼5 cells per reaction by spectroscopic measurement and analysis time within about three hours. The proposed sensing method provided a novel tool for simple, rapid, and low-cost detection of telomerase activity, eliminating the necessity for thermal cycling, primers in PCR-based assays, and amplification of telomerase extension products. It exhibits significant potential as a label-free, simple, ultrasensitive strategy for on-site detection of telomerase activity in proteomics and clinical diagnostics.

Synthesis of chiral gold helicoid nanoparticles using glutathione.

Chiral plasmonic nanostructures are in high demand because of their unique optical properties, which are applicable to polarization control, chiral sensing and biomedical applications. An easy and scalable synthesis method for these nanostructures may facilitate their development further. We have reported the synthesis for 432-symmetric chiral plasmonic nanoparticles by using a seed-mediated colloidal method facilitated by a chiral amino acid and peptides. Among those, 432 helicoid III nanoparticles particularly exhibited well-defined chiral morphologies and exceptional chiroptic properties, evidenced by a Kuhn's dissymmetry factor (g-factor) of 0.2, making them valuable for various applications. Here, we detail the synthesis stages, including the synthesis of seed nanoparticles, the verification of each stage outcome and the calibration of synthesis conditions. We further illustrate the troubleshooting section and video-document the stages to facilitate the reliable reproduction of 432 helicoid III nanoparticles. The procedure requires 8 h to complete and can be carried out by users with expertise in chemistry or materials science.

Crystalline Assemblies of DNA Nanostructures and their Functional Properties.

Self-assembly presents a remarkable approach for creating intricate structures by positioning nanomaterials in precise locations, with control over molecular interactions. For example, material arrays with interplanar distances similar to the wavelength of light can generate structural color through complex interactions like scattering, diffraction, and interference. Moreover, enzymes, plasmonic nanoparticles, and luminescent materials organized in periodic lattices are envisioned to create functional materials with various applications. Focusing on structural DNA nanotechnology, here, we summarized the recent developments of two- and three-dimensional lattices made purely from DNA nanostructures. We review DNA-based monomer design for different lattices, guest molecule assembly, and inorganic material coating techniques and discuss their functional properties and potential applications in photonic crystals, nanoelectronics, and bioengineering as well as future challenges and perspectives.

The effects of growth interruptions in the GaAsBi/InAs/GaAs quantum dots: The emergence of three-phase nanoparticles

The study investigated the impact of introducing bismuth into the GaAs capping layer (CL) on InAs quantum dots (QDs) to enhance their QD properties. Three different time-temperature routes (TTRs) were examined, as growth interruption (GI) stages are necessary due to the temperature requirements for the growth processes of QDs (510 °C) and GaAsBi CL (370 °C). Two of the TTRs revealed defective regions with bismuth-free nanotracks in the GaAsBi CL, which are linked to the formation of bismuth-rich droplets on the surface. Interestingly, in one of the TTRs, novel icosahedral-type nanoparticles appeared embedded at the first interface, leaving trails behind them. Upon detailed characterization, it was found that these nanoparticles consist of three distinct phases containing rhombohedral Bi, pure Ga, and a new In4Bi phase that had not been experimentally described before. The long particle trajectories and low temperatures suggest that the NPs remained liquid throughout the growth process, solidifying upon final cooling to room temperature. This work presents a new technique for incorporating plasmonic nanoparticle arrays made of non-noble metals into buried semiconductor layered interfaces, which offers greater flexibility in device design.

Plasmon-enhanced Brillouin light scattering spectroscopy for magnetic systems: Theoretical model

Brillouin light scattering (BLS) spectroscopy is an effective method for detecting spin waves in magnetic thin films and nanostructures. While it provides extensive insight into the properties of spin waves, BLS spectroscopy is impeded in many practical cases by the limited range of detectable spin wave wave numbers and its low sensitivity. Here we present a generalized theoretical model describing plasmon-enhanced BLS spectroscopy. Three types of plasmonic nanoparticles in the shape of an ellipsoid of rotation are considered: a single plasmon resonator, a sandwiched plasmonic structure in which two nanoparticles are separated by a dielectric spacer, and an ensemble of metallic nanoparticles on the surface of a magnetic film. The effective susceptibilities for the plasmonic systems at the surface of the magnetic film are calculated using the electrodynamic Green's function method, and the enhancement coefficient is defined. It is analytically shown that the ratio of the plasmon resonator height to its radius plays a key role in the development of plasmon-enhanced BLS spectroscopy. The developed model serves as a basis for the numerical engineering of the optimized plasmon nanoparticle morphology for BLS enhancement. Published by the American Physical Society 2024

Influence of resonant plasmonic nanoparticles on optically accessing the valley degree of freedom in 2D semiconductors

The valley degree of freedom in atomically thin transition metal dichalcogenides, coupled with valley-contrasting optical selection rules, holds great potential for future electronic and optoelectronic devices. Resonant optical nanostructures emerge as promising tools for controlling this degree of freedom at the nanoscale. However, their impact on the circular polarization of valley-selective emission remains poorly understood. In our study, we explore a hybrid system where valley-specific emission from a molybdenum disulfide monolayer interacts with a resonant plasmonic nanosphere. Contrary to the simple intuition that a centrosymmetric nanoresonator mostly preserves the degree of circular polarization, our cryogenic experiments reveal significant depolarization of the photoluminescence scattered by the nanoparticle. This striking effect presents an ideal platform for studying the mechanisms governing light-matter interactions in such hybrid systems. Our full-wave numerical analysis provides insights into the key physical mechanisms affecting the polarization response, offering a pathway toward designing novel valleytronic devices.

Laser-Induced Thermophoretic SERS Enhancement on Paper for Facile Pesticide and Nanoplastic Sensing.

Surface-enhanced Raman scattering (SERS) has emerged as a powerful tool for contamination detection. Fabricating efficient nanostructures with hotspots for signal enhancement and concentrating diluted target analyte molecules to the hotspots are critical for ultrasensitive SERS detection, which generally requires advanced instruments and intricate manipulations. Herein, we report a simple, low-cost, and high-efficiency paper device that can simultaneously concentrate the analytes and generate SERS hotspots rapidly with the assistance of laser-induced thermophoresis. After dropping the target- and plasmonic nanoparticle-containing solution on a paper substrate, the evaporative gradient created by the laser-induced thermophoresis can promote the delivery of the analytes and plasmonic nanoparticles simultaneously to the tiny area of the laser spot, forming compact SERS hotspots to significantly amplify the analyte's Raman scattering signals. This convenient thermophoretic strategy can be accomplished rapidly within ∼4 min and exhibits more than 104-times higher sensitivity than that without the assistance of laser-based thermophoresis. This elegant paper device is successfully applied to the detection of contaminants such as pesticides and nanoplastics in fruit and water samples, holding the potential to provide a simple, fast, and cost-effective approach for on-site detection of environmental contaminants.