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A Novel Metal Nanoparticles-Graphene Nanodisks-Quantum Dots Hybrid-System-Based Spaser
摘要： Active nanoplasmonics have recently led to the emergence of many promising applications. One of them is the spaser (surface plasmons ampli?cation by stimulated emission of radiation) that has been shown to generate coherent and intense ?elds of selected surface plasmon modes that are strongly localized in the nanoscale. We propose a novel nanospaser composed of a metal nanoparticles-graphene nanodisks hybrid plasmonic system as its resonator and a quantum dots cascade stack as its gain medium. We derive the plasmonic ?elds induced by pulsed excitation through the use of the effective medium theory. Based on the density matrix approach and by solving the Lindblad quantum master equation, we analyze the ultrafast dynamics of the spaser associated with coherent ampli?ed plasmonic ?elds. The intensity of the plasmonic ?eld is signi?cantly affected by the width of the metallic contact and the time duration of the laser pulse used to launch the surface plasmons. The proposed nanospaser shows an extremely low spasing threshold and operates in the mid-infrared region that has received much attention due to its wide biomedical, chemical and telecommunication applications.
关键词： spaser,graphene nanodisks,plasmonic ampli?ers,quantum dots cascade emitters,metal nanoparticles
更新于2025-09-16 10:30:52
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Fano resonance induced fast to slow light in a hybrid semiconductor quantum dot and metal nanoparticle system
摘要： We theoretically demonstrate the Fano resonance and the conversion from fast to slow light in a hybrid semiconductor quantum dot (SQDs)-metal nanoparticle (MNPs) with cavity quantum electrodynamics treatment. The absorption spectra of the weak probe field exhibit a series of asymmetric Fano line shapes and their related optical propagation properties, such as fast and slow light effects, are investigated based on the hybrid system for suitable parametric regimes. Further, the transparency windows (i.e. the absorption dip approaches zero) in the probe absorption spectra are accompanied by the rapid steep dispersion of the Fano resonance profile, which promises the slow or fast light effect, and even tunable fast-to-slow light propagation (or vice versa) can be achieved by controlling different parameter regimes. Therefore the investigation may indicate promising applications in quantum information processing based on the hybrid SQD-MNP system.
关键词： semiconductor quantum dots,cavity quantum electrodynamics (C-QED),metal nanoparticles,fast to slow light,Fano resonance
更新于2025-09-16 10:30:52
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Copper nanoparticles obtained by laser ablation in liquids as bactericidal agent for dental applications
摘要： The dramatic increase of antibiotic-resistant bacteria is considered one of the greatest threats to human health at global scale. The antibacterial activity of noble metal nanoparticles, could be the solution against bacterial infectious diseases which currently do not respond to conventional treatments. In this work, copper nanoparticles were produced by laser ablation using two different lasers. A nanosecond laser operating at 532nm and a picosecond laser at 1064nm were used to ablate a copper target submerged in water and methyl alcohol. The obtained colloidal solutions consisted of copper oxide nanoparticles in suspension with diameters ranging from few nanometers to 45 nm. The nanoparticles formation process is highly influenced by laser parameters, but the solvent plays a crucial role on their characteristics. Cu oxide nanoparticles obtained in water present chain-like nanostructure, while those obtained in methyl alcohol are spherical with lower presence of oxide. All the obtained nanoparticles are crystalline and noticeably stable. Microbiology confirm their strong activity against Aggregatibacter actinomycetemcomitans. Cytocompatibility with human periodontal ligament stem cells is also confirmed. The biological assays evidence that ions release is not the main parameter responsible for the bactericidal activity of copper nanoparticles. Other factors such as oxidation state, size and crystallographic structure, have a greater influence on the process.
关键词： noble metal nanoparticles,laser ablation,copper nanoparticles,antibacterial effect
更新于2025-09-12 10:27:22
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Development of plasmonic ELISA for the detection of anti-Leishmania sp. IgG antibodies
摘要： Recently, a novel Enzyme-Linked Immunosorbent Assay (ELISA) strategy has emerged, known as “plasmonic ELISA” (pELISA), which enables the detection of disease biomarkers at low concentrations with the naked eye. For the ?rst time, this research has developed a signal-generation mechanism for the detection of anti-Leishmania sp. IgG antibodies with the naked eye using pELISA. The immunoassay incorporates an indirect ELISA with successive growth of gold nanoparticles to obtain blue or red-colored solutions in the presence or absence of anti-Leishmania sp. IgG antibodies in canine serum, respectively. The technique we developed was successfully tested in canine serum positive and negative for canine leishmaniasis (CanL), and was shown to be an e?ective method that could be used as an additional tool for CanL diagnosis. It will be particularly useful in resource-constrained countries, because it does not require sophisticated instruments to read the results, increasing the practicality of CanL detection in these areas.
关键词： Canine Leishmaniasis,Metal nanoparticles,Enzyme-linked immunosorbent assay
更新于2025-09-12 10:27:22
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Crossover from positive to negative optical torque in mesoscale optical matter
摘要： The photons in circularly polarized light can transfer their quantized spin angular momentum to micro- and nanostructures via absorption and scattering. This normally exerts positive torque on the objects where the sign (i.e., handedness or angular direction) follows that of the spin angular momentum. Here we show that the sign of the optical torque can be negative in mesoscopic optical matter arrays of metal nanoparticles (NPs) assembled in circularly polarized optical traps. Crossover from positive to negative optical torque, which occurs for arrays with different number, separation and configuration of the constituent particles, is shown to result from many-body interactions as clarified by electrodynamics simulations. Our results establish that both positive and negative optical torque can be readily realized and controlled in optical matter arrays. This property and reconfigurability of the arrays makes possible programmable materials for optomechanical, microrheological and biological applications.
关键词： mesoscale optical matter,many-body interactions,metal nanoparticles,electrodynamics simulations,optical torque
更新于2025-09-11 14:15:04
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[Micro/Nano Technologies] Micro and Nano Fabrication Technology Volume 1 || Fabrication of Metallic Nanodot Arrays
摘要： Metal nanodot arrays exhibit unique optical characteristics, and they are expected to find widespread applications in biosensors and various optical devices. In this section, simple and efficient manufacturing processes are introduced for metal nanodot arrays. These processes are based on the combination of thin metal film coatings deposited on substrates and thermal dewetting. The first process discussed herein is a conventional thermal dewetting method. With this method, it is shown that the average dot diameter can be controlled based on the chosen process conditions. The second process is based on the use of grid patterning on coated metal films. This process can allow fabrication of nanodot arrays with uniform dot diameters and achieve highly ordered alignment of dots. The third process generates a metal nanodot array based on a self-organization manner on a nanogrid-patterned substrate. It constitutes a high-productivity process based on the transfer of the metal nanodot array to an adhesive film. The basic mechanisms underlying these processes are discussed herein.
关键词： Productivity,Metal coating,Dot transfer,Surface energy,Metal nanoparticles,Agglomeration,Nano plastic forming,Optical characteristics,Grid patterning,Self-organization,Biosensors,Thermal dewetting
更新于2025-09-10 09:29:36
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Comparison and convergence of optical absorption spectra of noble metal nanoparticles computed using linear-response and real-time time-dependent density functional theories
摘要： The real-time time-dependent density functional theory (RT-TDDFT) is rapidly gaining prominence as an alternative approach to capture optical properties of molecular systems, which warrants the necessity to benchmark the traditional linear response (LR) method and the RT approach. We calculate the absorption spectra of noble metal nanoparticles with a variety of sizes and shapes to demonstrate the consistency of the two methods over a broad range of energy. The RT spectrum obtained using a grid-based basis set with pseudopotentials achieves results in good agreement with the LR spectrum obtained with large QZ4P atom-centered basis sets. Factors that lead to convergence of the spectra are considered. In addition, the real-time variation of the electron density is visualized to show the collective oscillation of electron density for the plasmon modes of noble metal nanoparticles. The RT approach is most useful when calculating wide absorption spectra of larger gold or silver nanoparticles.
关键词： optical absorption spectra,noble metal nanoparticles,RT-TDDFT,LR-TDDFT,plasmon modes
更新于2025-09-10 09:29:36
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The third-order nonlinear optical properties of gold nanoparticles-methylene blue conjugation
摘要： Third-order nonlinear properties of a thiazine dye (methylene blue (MB)) and a plasmonic nanoparticle (gold nanoparticles (GNPs)) have been studied by Z-scan method with a 50 mW continues wave (CW) diode pumped solid state laser (DPSSL) operating at 532 nm. The nonlinear parameters (nonlinear refractive (NLR) index (n2) and nonlinear absorption (NLA) coefficient (β)) are determined. The mechanism of the observed NLA and nonlinear refraction is attributed respectively to reverse saturable absorption (RSA) and thermal nonlinear effects. The magnitude of the measured NLR index (n2) and NLA coefficient (β) are founded to be the order of 10?8 cm2/W and 10?4 cm/W respectively. The effect of MB and GNPs on each other has been studied. Z-scan experiments for GNPs-MB conjugation shows noticeable increase in nonlinear parameters.
关键词： Z-scan method,Metal nanoparticles,Nonlinear optics,Organic dye,Nonlinear refractive index,Nonlinear absorption coefficient
更新于2025-09-09 09:28:46
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Quenching of Luminol Fluorescence at Nano-Bio Interface: Towards the Development of an Efficient Energy Transfer System
摘要： Surface modified colloidal gold (Au) and silver (Ag) nanoparticles (NPs) were used as efficient quenchers of luminol (LH2) fluorescence either in homogeneous aqueous medium or its noncovalent assembly with bovine serum albumin (BSA). The mechanism as well as the extent of fluorescence quenching was found to be strongly dependent on the nature of the nanoparticles. While simple static type fluorescence quenching mechanism was perceived with AuNP, a more complex protocol involving quenching sphere model was envisaged for AgNP quenching. Nevertheless, the magnitude of Stern-Volmer (SV) quenching constant (KSV ~ 108–1010 M?1) was calculated to be ca. 104 times more for surface quoted NPs in comparison with BSA–NP bioconjugates system. On the other hand, a highly efficient (E ≈ 95%) energy transfer (ET) process was predicted for LH2 captured in the hydrophobic assembly with BSA in presence of AgNP as an acceptor. The ET efficiency is critically dependent on the concentration of BSA and nicely correlated with the extent of NP surface coverage. However, fluorescence quenching on AuNP surface is relatively less responsive towards protein concentration, primarily due to the difference in surface activity as well as the mode of interaction of the protein with NPs.
关键词： Bionanosensors,Bovine serum albumin,Luminol,Metal nanoparticles,Energy transfer,Fluorescence quenching
更新于2025-09-09 09:28:46
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Light-Induced Assembly of Metal Nanoparticles on ZnO Enhances the Generation of Charge Carriers, Reactive Oxygen Species and Antibacterial Activity
摘要： Increasing the photocatalytic activity of semiconductors by forming heterojunctions with metal improves their energy transfer efficiency and environmental remediation capabilities. However, our knowledge regarding the structure-activity relationship of semiconductor/metal hybrid nanostructures is lacking due to poor control over their physicochemical properties. Here, we report a facile way to make ZnO/metal heteronanoparticles by mixing/irradiation process of ZnO and metal nanoparticles. The resultant products provide an expedient model to explore the effects of various metal NPs on light-induced electron/hole separation, reactive oxygen species (ROS) production and antibacterial activities of ZnO NPs. Electron spin resonance spectroscopy was used to compare the effect of mixing Pt, Au, or Ag NPs at different size and concentration with ZnO NPs on light-induced electron-hole separation and ROS production. The enhancing effect of metal NPs depends on particle size, composition, and mass ratio of the metal NPs to the ZnO NPs. Smaller-sized Pt NPs are more efficient in promoting charge carrier generation and ROS production. At 5 nm, Ag NPs promoted charge carrier generation more efficiently than Pt and Au NPs, but Pt NPs promoted ROS generation more efficiently than Au and Ag NPs. These results provide valuable strategy to design the synthesis of semiconductor/metal hybrid nanostructures and easy tailoring of ROS and charge carrier production.
关键词： reactive oxygen species,photocatalytic activity,metal nanoparticles,antibacterial activity,ZnO
更新于2025-09-04 15:30:14