Localized Surface Plasmon Resonance Characteristics Research Articles

Plasmonic nanozyme Cu3P with significantly enhanced peroxidase-like activity for Cr (VI) colorimetric detection

Plasmonic nanozymes with both plasmonic and biocatalytic properties stand out due to their distinctive localized surface plasmon resonance (LSPR) feature and adjustable catalytic activity, while the enhancement effect of present reported plasmon excitation remains relatively low. Here, a plasmonic nanozyme of Cu3P nanoparticles (Cu3P NPs) with LSPR characteristics and intrinsic peroxidase (POD)-like activity was prepared via simple gas-solid reaction strategy, which presents significantly enhanced POD-like activity under plasmon stimulation than that without LSPR excitation, with catalytic constants for TMB and H2O2 83 and 127 times higher than those without LSPR excitation respectively. On the one hand, the Cu3P plasmonic nanozyme generated abundant high-energy hot carriers under near-infrared (NIR) stimulation to promote cracking of H2O2 to produce plentiful reactive oxide species (ROS); on the other hand, the LSPR-induced photothermal effect on Cu3P plasmonic nanozyme greatly improves the reaction kinetics, thus making a significantly boosts POD-like activity. According to the excellent POD-like activity of Cu3P plasmonic nanozyme and 8-hydroxyquinoline (8-HQ)-mediated chromaticity switch, a highly sensitive Cr (VI) chrominance sensing platform was developed with a detection limit of 9.6 nM within a range from 0.01 to 20 μM. This study spotlights the high utilization efficiency of plasmon stimulation for enzyme-like activity tuning.

Multi-interfacial bridging engineering of flexible MXene film for efficient electromagnetic shielding and energy conversion

Accompanied by the progressive development of electronic equipment, excellent electromagnetic interference (EMI) shielding materials display a satisfying prospect in protecting electronic devices against electromagnetic pollution/radiation, while integrating energy conversion. Heretofore, it remains a conundrum to availably construct thin films with multi-interfacial bridging engineering as multifunctional shielding devices. To effectively achieve electromagnetic wave attenuation and integrate energy conversion, a co-mixed vacuum-assisted filtration strategy is designed to synthesize Au@MXene/cellulose nanocrystal/dodecylbenzenesulfonic acid-doped polyaniline (AMCP) films. Profited from the interfacial engineering, the total EMI shielding effectiveness (SE) can be increased by 27 % with the highest value of 67.9 dB. MXene with localized surface plasmon resonance characteristics gives the composite films good energy conversion performance, that is, the composite film can be rapidly heated up to 100 °C under the irradiation of an infrared lamp, and its surface temperature remains stable after continuous irradiation. Additionally, the infrared emissivity is as low as 0.173 within the 8–14 μm, which is necessary to adapt various application scenarios. Therefore, it is reliable that the AMCP films constructed by multicomponent offer a facile strategy for MXene-based EMI shielding devices with integration characteristics.

Development of silver nanocubes created by pulsed laser ablation in liquid

This paper describes a simple approach for creating silver (Ag) nanocubes using pulsed laser ablation in a liquid medium. The development of nanocubical formations of Ag obtained by laser ablation using Nd: YAG laser was conducted for 5, 10, 15, and 20[Formula: see text]min. The surface morphological analysis was performed using field-emission scanning electron microscopy (FESEM) to show the formation of silver nanocubes with edge lengths ranging from 150[Formula: see text]nm to 250[Formula: see text]nm. The UV-visible spectroscopy demonstrates that the concentration of Ag nanostructures, evidenced by the characteristic localized surface plasmon resonance band near 400[Formula: see text]nm in the colloidal solution containing Ag nanoparticles, increased with the increasing laser ablation duration from 5[Formula: see text]min to 20[Formula: see text]min. The growth mechanism for Ag nanocubes can be easily understood with the change in laser ablation time from 5 to 10, 15, and then 20[Formula: see text]min. The Ag sheets with no specific shape start to develop after 5 min of laser ablation, and after 10[Formula: see text]min, larger particles form. Then, after 15[Formula: see text]min, a small number of cube-like nanostructures with rough and uneven edges was obtained. At the end of 20[Formula: see text]min, a complete cubic formed with fine and distinct edges and a very large amount of nanocubes. The elemental silver signal was present in Ag nanocubes, as revealed by the energy-dispersive X-ray spectroscopy (EDS) spectra. The produced Ag nanocubes may be used to construct two-dimensional nanocomposites with practical applications in the electrical, optoelectronic, electrochemical, and biological areas.

Chromogenic Mechanisms of Colorimetric Sensors Based on Gold Nanoparticles.

The colorimetric signal readout method is widely used in visualized analyses for its advantages, including visualization of test results, simple and fast operations, low detection cost and fast response time. Gold nanoparticles (Au NPs), which not only exhibit enzyme-like activity but also have the advantages of tunable localized surface plasmon resonance (LSPR), high stability, good biocompatibility and easily modified properties, provide excellent platforms for the construction of colorimetric sensors. They are widely used in environmental monitoring, biomedicine, the food industry and other fields. This review focuses on the chromogenic mechanisms of colorimetric sensors based on Au NPs adopting two different sensing strategies and summarizes significant advances in Au NP-based colorimetric sensing with enzyme-like activity and tunable LSPR characteristics. In addition, the sensing strategies based on the LSPR properties of Au NPs are classified into four modulation methods: aggregation, surface modification, deposition and etching, and the current status of visual detection of various analytes is discussed. Finally, the review further discusses the limitations of current Au NP-based detection strategies and the promising prospects of Au NPs as colorimetric sensors, guiding the design of novel colorimetric sensors.

Colorimetric sensing of Cu(II) ions in water on the basis of selective chemical etching of EDA-capped Ag nanoplates

Cu(II) ions are one of the essential mineral elements in the human body, but can pose a substantial health risk to people exposed to high concentrations of Cu(II) ions over a long period. Therefore, the ability to detect Cu(II) ions in drinking water is important. In this study, a novel colorimetric sensing probe for the easy and onsite detection of Cu(II) ions in drinking water was developed. The probe was constructed through selective chemical etching of triangular Ag nanoplates with tunable localized surface plasmon resonance (LSPR) properties. Ethylenediamine (EDA) was used as an organic capping agent to improve the chemical stability of triangular Ag nanoplates. Selective chemical etching of the EDA-capped Ag nanoplates in the presence of Cu(II) ions as a result of the formation of a coordination complex between the EDA and Cu(II) ions caused remarkable changes in the nanoplates’ LSPR characteristics. On the basis of this phenomenon, a novel colorimetric sensing probe capable of detecting Cu(II) ions in drinking water at concentrations above the safety limit was developed. Our findings were also extended to develop a portable and paper-based sensing probe with good long-term stability to overcome the shortcomings of liquid-phase colorimetric sensors without requiring a spectrometer. The proposed colorimetric sensing probes provide accurate results even with a real sample and offer numerous advantages over conventional sensing platforms, including clearly distinguishable color changes that can be observed by the naked eye; thus, the proposed probes can be used for the selective, reliable, and low-cost point-of-care detection of Cu(II) ions in water.

Charge transfer effect: a new assignment of the abnormal optical absorption band of gold nanoparticles

As a significant accompanying phenomenon of surface-enhanced Raman scattering (SERS), the addition of foreign molecules to colloidal gold or silver nanoparticles results in a new abnormal optical absorption (AOA) band, which usually appears in the long-wavelength region. The assignment of this AOA band has long been debated as an important issue that is desired to be addressed in the SERS field, which is crucial for a clear understanding of the SERS enhancement mechanism and beneficial to surface plasmonics. In this study, both the calculated and measured optical absorptions of gold nanoparticle monomers and dimers as well as their interactions with adsorbed molecules, showed that the AOA band in the long-wavelength region which was assigned to the characteristic longitudinal localized surface plasmon resonance (LSPR) effect of gold nanoparticle chain aggregates in conventional SERS electromagnetic theory, should be attributed to the charge-transfer resonance absorption from gold nanoparticles to adsorbed molecules. This was further confirmed by the corresponding SERS effects. As the excitation wavelength at 785 nm was resonant with the broad AOA band centered at 750 nm, the SERS peaks of the adsorbed pyridine molecules could be dramatically enhanced due to the charge-transfer resonance effect. In contrast, under an excitation wavelength of 532 nm, the SERS peaks appeared very weak, although the excitation wavelength was resonant with the LSPR absorption band of the individual gold nanoparticles.

Plasmonic properties of composition graded spherical nanoparticles in quasi-static approximation

During the operation of a localized surface plasmon resonance (LSPR) sensor made in the form of a core–shell nanoparticle with the shell acting as a sensing layer, the target molecules penetrate into the shell due to intrinsic diffusion or reaction mechanisms. As a result, these molecules or various reactants are nonuniformly distributed in the shell layer. Such sensing particles are termed composition graded plasmonic particles, and their LSPR characteristics may be quite different from those of the uniform core–shell particles. Here, under the quasi-static assumption, a perturbation theory is developed to predict the LSPR properties of composition graded plasmonic particles. The effects of the composition gradient on the LSPR properties due to a metal hydride, a dielectric, and an effective medium are either numerically calculated or analytically derived. Our results show that various configurations of the composition gradient can tune the location and the amplitude of the LSPR peak. The results are important for understanding the sensing performance of composition graded plasmonic particles, and the perturbative treatment presented here can also be used for other composition graded structures.

Depletion force optimization for high-purity gold nanotriangles prepared using different growth methods.

A homogeneous structural distribution in metal nanoparticle is commonly required for their application, and despite high-yield growth techniques, unavoidable structural heterogeneity remains a concern in metal nanoparticle synthesis. Gold nanotriangles (AuNTs) were synthesized using seed-mediated and seedless growth methods. Recent advancements in high-yield synthesis processes have enabled easy handling of AuNTs, which exhibit unique localized surface plasmon resonance characteristics due to their anisotropic triangular form. The flocculation and subsequent precipitation technique was used to purify AuNTs of different sizes synthesized using seed-mediated and seedless growth methods. The optimal conditions for obtaining high-purity AuNTs were explored by introducing a high concentration of cetyltrimethylammonium chloride. Additionally, the depletion force necessary for achieving high-purity AuNTs was calculated to reveal variations in the required depletion forces for AuNTs synthesized using different growth techniques. The alternations in the size distribution of AuNTs during the flocculation step were tracked using dynamic light scattering, and the surface charge of AuNTs synthesized through different growth methods was evaluated by ζ-potential. The high purity of the AuNTs produced using the seedless growth method required a larger depletion force than the seed-mediated grown AuNTs. The difference in the required depletion forces results from the difference in the electrostatic forces caused by the different growth methods.

Cascade integration of nonlinear phenomena exhibited by monometallic nanoparticles

In this work were numerically analyzed the third-order nonlinear optical effects exhibited by combinations of uncoupled monometallic silver, gold and platinum nanoparticles. The nanosystems were considered to be homogeneous and surrounded by a dielectric matrix. The design of the nanostructures was evaluated as a collective behavior resulting from the specific order of the set in trilayer tandem form. The characteristic Localized Surface Plasmon Resonance phenomena in the yellow, green and ultraviolet absorption bands for the Ag, Au and Pt; respectively, were considered. Different permutations of the three kind of monometallic elements selected in sequence were studied by using the wave equation and the finite difference method. Immediate indications useful for exploring nonlinear nanodevices and for building up nanostructured platforms based on nanoscale functions can be anticipated from this work.

Green synthesis of nanosilver using Fomes fomentarius mushroom extract over aramid fabrics with improved coloration effects

Silver nanoparticles (AgNPs) were greenly synthesized over aramid fabrics from wild mushroom ( Fomes fomentarius) to develop colorful products. The localized surface plasmon resonance characteristics of AgNPs provided versatile coloration effects on fabrics, with improved color strength ( K/ S) and other colorimetric values ( L*, a*, and b*). The stability of the colored materials was also investigated in terms of color fastness to wash and rubbing (both wet and dry states). The characteristics of deposited AgNPs over aramid materials were characterized by X-ray fluorescence spectroscopy testing of solid fabric samples. Morphological properties of the aramid substrates were investigated using SEM (scanning electron microscopy) testing to check the surfaces both for nanosilver-treated and untreated materials. Moreover, the developed nanoparticles were also confirmed further using SEM-deployed energy-dispersive X-ray spectroscopy and elemental mapping analysis. The chemical bonding between the aramid fiber and deposited AgNPs was tested using Fourier infrared spectroscopy analysis. The thermal stability of the aramid fabrics was examined in order to investigate their behavior when exposed to heat in terms of thermogravimetric analysis and derivative thermogravimetry analysis. The K/ S values and darkness values were increasing with the increased loading of the nanosilver precursor. Moreover, statistical analysis was also conducted in terms of the coefficient of variation ( R2) to understand the significance of the connection between the nanosilver loading and coloration characteristics, and found a significant relationship. Overall, a novel, sustainable, and facile biosynthesis route of AgNPs is reported in this current research.

Simulation and design of dual-band quantum dot infrared photodetector based on metal grating structure

Quantum dot infrared photodetectors (QDIP) have a weak ability to capture light, which limits the further improvement of absorptivity to a certain extent. Since the localized surface plasmon resonance (LSPR) can effectively couple the optical radiation energy and result in a significant field enhancement effect in the near-field range, it is introduced to improve the absorptivity of the QDIP. Concretely, the strip metal grating structure is coupled to the active region of the traditional QDIP, and a metal reflective layer is added at the bottom of the QDIP to improve the absorptivity by using the metal–semiconductor–metal structure. The simulation results show that the addition of the optimized strip metal grating structure can make the photon absorptivity of QDIP reach more than 90% in both frequency bands of 37.5 and 48.5 THz, and the coupling characteristics of LSPR are studied by the analysis of the electric field distribution of QDIP, which can provide the theoretical guidance for the combination of metal grating and traditional QDIP.

Plasmonic Nanozymes: Localized Surface Plasmonic Resonance Regulates Reaction Kinetics and Antibacterial Performance.

Among the members of the rapidly growing nanozyme family, plasmonic nanozymes stand out because of their unique localized surface plasmon resonance (LSPR) characteristics and tunable catalytic activity. We prepared a plasmonic nanozyme of Au gold nanoparticles (AuNPs) and Cu metal-organic framework nanosheets (Cu-MOFNs). The Cu-MOFNs have peroxidase-like activity, while AuNPs present unique LSPR characteristics. We found that the as-prepared AuNPs/Cu-MOFNs composite presents 1.6-fold faster reaction kinetics under LSPR excitation compared to that in the dark. Investigations of energy levels, radical capture, and dark-field scattering spectroscopy revealed that LSPR of AuNPs as well as matched energy levels can facilitate efficient hot electron transfer, which could readily cleave the chemical bond of the substrate and accelerate the reaction kinetics. On the basis of these results, we achieved enhanced antibacterial therapy and wound healing using plasmonic AuNPs/Cu-MOFNs. This study spotlights the superiority of plasmonic nanozymes in improving the enzyme-like performance of nanozymes.

Ultrasmall gold nanorod-polydopamine hybrids for enhanced photoacoustic imaging and photothermal therapy in second near-infrared window.

Gold nanorods (GNRs) have attracted great interest for photo-mediated biomedicines due to their tunable and high optical absorption, high photothermal conversion efficiency and facile surface modifiability. GNRs that have efficient absorption in second near-infrared (NIR-II) window hold further promise in bio-applications due to low background signal from tissue and deep tissue penetration. However, bare GNRs readily undergo shape deformation (termed as 'melting effect') during the laser illumination losing their unique localized surface plasmon resonance (LSPR) properties, which subsequently leads to PA signal attenuation and decreased photothermal efficiency. Polydopamine (PDA) is a robust synthetic melanin that has broad absorption and high photothermal conversion. Herein, we coated GNRs with PDA to prepare photothermally robust GNR@PDA hybrids for enhanced photo-mediated theranostic agents. Ultrasmall GNRs (SGNRs) and conventional large GNRs (LGNRs) that possess similar LSPR characteristics as well as GNR@PDA hybrids were compared side-by-side in terms of the size-dependent photoacoustic (PA) imaging, photothermal therapy (PTT), and structural stability. In vitro experiments further demonstrated that SGNR@PDA showed 95% ablation of SKOV3 ovarian cancer cells, which is significantly higher than that of LGNRs (66%) and SGNRs (74%). Collectively, our PDA coating strategy represents a rational design for enhanced PA imaging and efficient PTT via a nanoparticle, i.e., nanotheranostics.

Mesoporous Au@Cu2−xS Core–Shell Nanoparticles with Double Localized Surface Plasmon Resonance and Ligand Modulation for Hole‐Selective Passivation in Perovskite Solar Cells

Core–shell nanomaterials have led to their fascinating properties in optical applications due to the localized surface plasmon resonance (LSPR). Herein, a mesoporous core–shell Au@Cu2−x S nanomaterial with dual LSPR characteristics is introduced to stabilize and passivate the perovskite/spiro‐OMeTAD interface of perovskite solar cells (PSCs). Thanks to the LSPR, Au@Cu2−x S nanoparticles (NPs) have the potential to enhance the infrared absorption and intensify the local electric field at the perovskite/spiro‐OMeTAD interface. The embedding of the mesoporous Au@Cu2−x S in the spiro‐OMeTAD layer can improve the contact and form “bridges” between perovskite grains and spiro‐OMeTAD. With the help of cationic surfactant cetyltrimethylammonium bromide, these mesoporous Au@Cu2−x S NPs can passivate surface traps and smooth the valence‐band offset at the perovskite/spiro‐OMeTAD interface for hole transferring. Furthermore, the improved hole mobility can offer balanced charge transport and prevent the carrier accumulation at interfaces. As a result, the Au@Cu2−x S(20:10)‐based PSCs achieves a champion efficiency over 22%, higher than that of the Au@Cu2−x S‐based device.

Multifunctional Plasmonic Core-Satellites Nanoprobe for Cancer Diagnosis and Therapy Based on a Cascade Reaction Induced by MicroRNA.

Constructing multifunctional plasmonic core-satellites (CS) nanoassembly for clinical cancer diagnosis and therapy has gained vast attention. Herein, we reported a doxorubicin (Dox)-loaded CS nanoprobe for microRNA (miRNA) detection, targeting drug release, and therapy evaluation. The plasmonic CS nanoprobe was constructed with uniformly distributional 50 nm (core) and 13 nm (satellites) gold nanoparticles (AuNPs), which were functionally assembled with a specific sequence of DNA and peptides. Anticancer drug Dox was loaded by intercalating into the GC-rich double strands. In the presence of target miRNA (miRNA-21 used as model), the constructed CS nanostructure was disassembled, producing characteristic localized surface plasmon resonance (LSPR) signals and releasing Dox. With the increase of the miRNA-21 concentration ranging from 0.01 to 1000 fM, a distinct blue shift of scattering spectra peak occurred, along with obvious color change from orange to green under a dark-field microscope (DFM), which can be used to detect miRNA at single-particle level. Meanwhile, it released Dox-induced apoptosis. Caspase-3 involved in apoptosis was then activated to cleave the specific peptide substrate, releasing fluorophore FAM from AuNPs. As a result, caspase-3 was detected based on restored fluorescence intensity, which was used to evaluate the therapy effectiveness. In a word, the multifunctional plasmonic CS nanoprobe can be used not only to image cellular miRNA-21 to distinguish tumor cells from normal cells, but also to release drugs and monitor the apoptotic process in situ by confocal imaging.

Bringing the interaction of silver nanoparticles with bacteria to light.

In past decades, the exploitation of silver nanoparticles in novel antibacterial and detection devices has risen to prominence, owing to the well-known specific interaction of silver with bacteria. The vast majority of the investigations focus on the investigation over the mechanism of action underpinning bacterial eradication, while few efforts have been devoted to the study of the modification of silver optical properties upon interaction with bacteria. Specifically, given the characteristic localized surface plasmon resonance of silver nanostructures, which is sensitive to changes in the charge carrier density or in the dielectric environment, these systems can offer a handle in the detection of bacteria pathogens. In this review, we present the state of art of the research activity on the interaction of silver nanoparticles with bacteria, with strong emphasis on the modification of their optical properties. This may indeed lead to easy color reading of bacterial tests and pave the way to the development of nanotechnologic silver-based bacterial detection systems and drug-screening platforms.

Nonressonant nonlinear optical switching behavior of Ag monometallic and Ag@Au bimetallic investigated by femtosecond Z-Scan measurements

Metallic nanoparticles are of great interest in technological applications, especially in photonics. Here, we describe the nonlinear optical properties of colloidal solutions of monometallic silver (AgNPs) and bimetallic nanoparticles, with Ag (core) - Au (shell) (Ag@AuNPs) structure, in the infrared region with ultrashort pulses. UV–Vis spectroscopy showed LSPR (localized surface plasmon resonance) characteristics bands. MEV measurements confirm that the nanoparticles have a spherical shape with good size distribution around 56 nm for AgNPs and 73 nm for Ag@AuNPs. The nonlinear optical properties of the nanostructures were determined by the Z-scan technique, with a laser at 1040 nm (~357 fs), for different intensities. We observed the effects of saturated absorption and reverse saturated absorption as a function of intensity for both nanoparticles with the increase of laser intensity was observed in the open-aperture (OA) measurements in nonresonant mode. Ag@AuNPs present a complete transition from saturation absorption to reverse saturation absorption. The close-aperture (CA) measurements in nonresonant mode indicate an effective negative nonlinearity for nanoparticles, corresponding to self-defocusing. Our results show that these bimetallic nanoparticles have great potential for application in photonics, especially in applications where the tuning of nonlinear optical properties is a determining factor.

Synthesis of Silver Nanoparticles by Plasma-Assisted Hot-Filament Evaporation for Enhancing in Luminescence Properties of Organic Light Emitting Diode

In this work, silver (Ag) nanoparticles were synthesized using plasma-assisted hot-filament evaporation, both with and without plasma deposition environments. This technique was used for the deposition of the nanoparticles in high-density, with controlling the size and interparticle separation. The size and interparticle separation acted as the primary factors of the variation of the localized surface plasmon resonance characteristics of the nanoparticles. The Ag nanoparticles reflected an additional layer in a typical organic light-emitting diode (OLED). The OLED with the Ag nanoparticles layer resulted in a low operating voltage, with a high luminance that reached 62.9 % under the hydrogen plasma environment, as compared to the reference device (OLED without the Ag nanoparticles layer). The effects of the Ag nanoparticles synthesis layer, both with and without plasma deposition on the OLED luminance, were also discussed.

The influence of a dielectric spacer layer on the morphological, optical and electrical properties of self-dewetted silver nanoparticles

ABSTRACT Metal nanoparticles attract the worldwide interest due to their interesting optical and electrical properties, which allow their implementation as promising light scatters in solar cell devices. These nanoparticles exhibit localized surface plasmon resonance (LSPR) characteristics, which are strongly dependent on both intrinsic and extrinsic factors. Tuning the LSPR characteristics yields to interesting properties in terms of enhancement, localization and guiding of the electromagnetic field on sub-wavelength scales. For that purpose, we investigate in this work the effect of dielectric spacer layer (tin oxide) with different thickness on light reflection due to random self-assembled Ag-NPs. A correlation between morphological properties, optical reflectance and electrical characteristics is established by combining scanning electron microscopy, UV-Vis-NIR spectroscopy and current–voltage analyses. Our results show that a dielectric layer with an appropriate thickness and refractive index is useful for reducing the amount of reflected light and consequently the shifted photocurrent response for all wavelengths.

Remediation of Wastewater from Chlorpyrifos Pesticide by Nano-Gold Photocatalyst

AbstractSuccessful disintegration of Chlorpyrifos pesticide by nearly monodisperse nano-gold photcatalyst (∼10 nm) for remediation of wastewater has been reported in current studies. Nano-Gold dispersion reaction with Chlorpyrifos solutions completes in 45 minutes at ambient temperature under the normal daylight and exhibit systematic variations in the solution color from wine red to pink to light sky blue and finally transforming into a transparent solution with fine precipitates. UV-Vis absorption studies correlates well with the systematic color changes as observed in the nano-gold treated Chlorpyrifos solutions with time. The characteristic localized surface plasmon resonance peak of nanogold dispersion observed at 529 nm red shifts to weak, medium and strong intensity peaks at ∼ 640 nm, 740 nm and 890 nm on increasing chlorpyrifos concentration owing to the aggregation of gold nanoparticles in small to bigger sized clusters. The fine turbidity in final transparent solution further confirms the aggregation of nanogold particles into stable bigger ensembles. IR transmission spectra of final transparent solutions showed disappearance of Chlorpyrifos νC-Cl and phosphorothioate functional group peaks indicating degradation of chlorpyrifos.