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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Effective Coupling of a Plasmonic Nanorod to a Microsphere Resonator
摘要： Coupled photonic-plasmonic systems have already proven successful as ultra-sensitive sensors with the potential of single virus detection. Such systems are e.g. composed of a plasmonic nanoparticle in vicinity of an optical resonator usually in the form of a microsphere, a mirroring or a microdisk. These systems are proven highly sensitive due to their large quality factor and are thus utilized as bio, pressure, gas or temperature sensors. When a plasmonic nanoparticle is positioned near such resonator, coupling of the plasmonic and photonic modes can result in an ultra-sensitive biosensor, since nanoparticle presence enhance ambient refractive index (RI) variation sensitivity. In this paper, photonic-plasmonic coupling of a gold nanorod in close vicinity of a silica microsphere is simulated in order to investigate various types of coupling settings in such systems. The presence of the nanorod results in a frequency shift as well as in a reduction of the quality factor, which are both highly dependent on nanorod properties such as size, distance between the particle and the sphere as well as the nanorod orientation relative to the sphere surface. A single gold nanorod is positioned in 50nm distance to a 15.5μm silica microsphere which supports a whispering gallery mode at 1550nm and both resonance frequency and quality factor are computed using the simulation platform COMSOL Multiphysics. The nanorod orientation is altered starting from the tangential direction with respect to the sphere surface (0o) to the perpendicular direction (90o). In the Fig 1a) the quality factor together with the damping constant is shown as a function of the nanorod orientation for at an operating wavelength of 1550nm. The 90o direction results in higher quality factor as well as a better mode stability although the frequency shift associated to a 90o turn is only about 10GHz. In Fig 1b) the frequency shift and quality factor for the perpendicular nanorod versus ambient medium RI is plotted, which confirms the ultra-sensitivity of the designed optical resonator up to a 10-3 RI shift. The electric field distribution outside and inside of the nanorod is illustrated in Fig. 1c) for the three directions 90o, 45o and 0o where the perpendicular nanorod shows the weakest interaction with the excited whispering gallery mode and thus yields the largest quality factor.
关键词： silica microsphere,photonic-plasmonic coupling,gold nanorod,COMSOL Multiphysics,whispering gallery mode
更新于2025-09-12 10:27:22
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Growth mechanism of gold nanorods: the effect of tip-surface curvature as revealed by molecular dynamics simulations
摘要： To understand the anisotropic growth mechanism of gold nanorods (AuNRs) during colloidal synthesis is critical for controlling the nanocrystal size and shape and thus has implications in tuning the properties for applications in a wide range of research and technology fields. In order to investigate the role of the cetyltrimethylammonium bromide (CTAB) coating in the anisotropic growth mechanism of AuNRs, we used molecular dynamics (MD) simulations and built a computational model that considered explicitly the effect of the curvature of the gold surface on CTAB adsorption and therefore differentiated the CTAB arrangements on flat and curved surfaces, representing the lateral and tip facets of growing AuNRs, respectively. We verified that on a curved surface, a lower CTAB coverage density and larger intermicellar channels are generated compared to those on a flat surface. Using umbrella sampling simulations, we measured the free energy profile and verified that the environment around a curved surface corresponds to an easier migration from the solution to the gold surface for the [AuBr2]? species than does a flat surface. Long unbiased molecular dynamics simulations also corroborated the umbrella sampling results. Therefore, the [AuBr2]? diffusion through the environment of the tips is much more favorable than in the case of lateral facets. This shows that the surface curvature is an essential component of the anisotropic growth mechanism.
关键词： molecular dynamics,growth mechanism,CTAB,umbrella sampling,surface curvature,gold nanorod synthesis
更新于2025-09-12 10:27:22
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Plasmon-Enhanced Fluorescence in Gold Nanorod-Quantum Dot Coupled Systems
摘要： Plasmon-exciton coupling is of great importance to many optical devices and applications. One of the coupling manifestations is plasmon-enhanced fluorescence. Although this effect is demonstrated in numerous experimental and theoretical works, there are different particle shapes for which this effect is not fully investigated. In this work electrostatic complexes of gold nanorods and CdSe/CdZnS quantum dots were studied. Double-resonant gold nanorods have an advantage of the simultaneous enhancement of the absorption and emission when the plasmon bands match the excitation and fluorescence wavelengths of an emitter. A relationship between the concentration of quantum dots in the complexes and the enhancement factor was established. It was demonstrated that the enhancement factor is inversely proportional to the concentration of quantum dots. The maximal fluorescence enhancement by 10.8 times was observed in the complex with the smallest relative concentration of 2.5 quantum dots per rod and approximately 5 nm distance between them. Moreover, the influence of quantum dot location on the gold nanorod surface plays an important role. Theoretical study and experimental data indicate that only the position near the nanorod ends provides the enhancement. At the same time, the localization of quantum dots on the sides of the nanorods leads to the fluorescence quenching.
关键词： quantum dot fluorescence,gold nanorod-quantum dot complexes,plasmon-enhanced fluorescence,plasmon-exciton coupling,gold nanorods
更新于2025-09-11 14:15:04
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A rotary plasmonic nanoclock
摘要： One of the fundamental challenges in nanophotonics is to gain full control over nanoscale optical elements. The precise spatiotemporal arrangement determines their interactions and collective behavior. To this end, DNA nanotechnology is employed as an unprecedented tool to create nanophotonic devices with excellent spatial addressability and temporal programmability. However, most of the current DNA-assembled nanophotonic devices can only reconfigure among random or very few defined states. Here, we demonstrate a DNA-assembled rotary plasmonic nanoclock. In this system, a rotor gold nanorod can carry out directional and reversible 360° rotation with respect to a stator gold nanorod, transitioning among 16 well-defined configurations powered by DNA fuels. The full-turn rotation process is monitored by optical spectroscopy in real time. We further demonstrate autonomous rotation of the plasmonic nanoclock powered by DNAzyme-RNA interactions. Such assembly approaches pave a viable route towards advanced nanophotonic systems entirely from the bottom-up.
关键词： DNA nanotechnology,nanophotonics,DNAzyme-RNA interactions,plasmonic nanoclock,gold nanorod
更新于2025-09-11 14:15:04
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Biocompatible Gold Nanorod Conjugates for Preclinical Biomedical Research
摘要： Gold nanorods with a peak absorption wavelength of 760 nm were prepared using a seed-mediated method. A novel protocol has been developed to replace hexadecyltrimethylammonium bromide on the surface of the nanorods with 16-mercaptohexadecanoic acid and metoxy-poly(ethylene glycol)-thiol, and the monoclonal antibody HER2. The physical chemistry properties of the conjugates were monitored through optical and zeta-potential measurements to confirm surface chemistry changes. The efficiency of the modifications was quantified through measurement of the average number of antibodies per gold nanorod. The conjugates were investigated for different cells lines: BT-474, MCF7, MCF10, MDCK, and fibroblast. The results show successful cell accumulation of the gold nanorod HER2 conjugates in cells with HER2 overexpression. Incubation of the complexes in heparinized mouse blood demonstrated the low aggregation of the metallic particles through stability of the spectral properties, as verified by UV/VIS spectrometry. Cytotoxicity analysis with LDH release and MTT assay confirms strong targeting and retention of functional activity of the antibody after their conjugation with gold nanorods. Silver staining confirms efficient specific binding to BT-474 cells even in cases where the nanorod complexes were incubated in heparinized mouse blood. This is confirmed through in vivo studies where, following intravenous injection of gold nanorod complexes, silver staining reveals noticeably higher rates of specific binding in mouse tumors than in healthy liver. The conjugates are reproducible, have strong molecular targeting capabilities, have long term stability in vivo and can be used in pre-clinical applications. The conjugates can also be used for molecular and optoacoustic imaging, quantitative sensing of biological substrates, and photothermal therapy.
关键词： Metallic nanoparticles,Gold nanorod fabrication,Cell particle targeting,Gold surface modification,Biocompatible targeting agent,Antibody conjugation
更新于2025-09-10 09:29:36
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Colorimetric Determination of Hypochlorite Based on the Oxidative Leaching of Gold Nanorods
摘要： Hypochlorite plays a critical role in killing microorganisms in the water. However, it can also cause cardiovascular diseases, neuron degeneration, and cancer to humans. Although traditional methods feature excellent sensitivity and reliability in detecting hypochlorite, the expensive instruments and strict determination conditions have limited their application in environmental analysis to some extent. Thus, it is necessary and urgent to propose a cheap, facile, and quick analytical assay for hypochlorite. This paper proposes a colorimetric assay for hypochlorite utilizing gold nanorods (AuNRs) as the nanoreactor and color reader. The AuNRs were acquired via a reported seed-mediated method. NaClO with strong oxidation property can cause the etching of gold from the longitudinal tips of AuNRs, which could shorten the aspect ratio of AuNRs, decrease the absorption in the UV–Vis spectrum and also induce the solution color changing from red to pale yellow. Thus, according to the solution color change and the absorbance of longitudinal surface plasmon resonance of AuNRs, we established the calibration curve of NaClO within 0.08 μM to 125 μM (?Abs = 0.0547 + 0.004 CNaClO, R2 = 0.9631). Compared to traditional method, we obtained the conversion formula between the concentration of residual-chlorine in tap water and the concentration of hypochlorite detected by the proposed colorimetric assay, which is Cresidual-chlorine = 0.24 CNaClO. Finally, the real application of the colorimetric assay in tap water was successfully performed, and the accuracy of the colorimetric method can reach from ?6.78% to +8.53%.
关键词： colorimetric determination,hypochlorite,gold nanorod
更新于2025-09-10 09:29:36
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A dual-targeted hyaluronic acid-gold nanorod platform with triple-stimuli responsiveness for photodynamic/photothermal therapy of breast cancer
摘要： Multi-stimuli-responsive theranostic nanoplatform integrating functions of both imaging and multimodal therapeutics holds great promise for improving diagnosis and therapeutic efficacy. In this study, we reported a pH, glutathione (GSH) and hyaluronidase (HAase) triple-responsive nanoplatform for HER2 and CD44 dual-targeted and fluorescence imaging-guided PDT/PTT dual-therapy against HER2-overexpressed breast cancer. The nanoplatform was fabricated by functionalizing gold nanorods (GNRs) with hyaluronic acid (HA) bearing pendant hydrazide and thiol groups via Au-S bonds, and subsequently chemically conjugating 5-aminolevulinic acid (ALA), Cy7.5 and anti-HER2 antibody onto HA moiety for PDT, fluorescence imaging and active targeting, respectively. The resulting versatile nanoplatform GNR-HA-ALA/Cy7.5-HER2 had uniform sizes, favorable dispersibility, as well as pH, GSH and HAase triple-responsive drug release manner. In vitro studies demonstrated that HER2 and CD44 receptor-mediated dual-targeting strategy could significantly enhance the cellular uptake of GNR-HA-ALA/Cy7.5-HER2. Under near-infrared (NIR) irradiation, MCF-7 cells could efficiently generate reactive oxygen species (ROS) and heat, and be more efficiently killed by a combination of PDT and PTT as compared with individual therapy. Pharmacokinetic and biodistribution studies showed that the nanoplatform possessed a circulation half-life of 1.9 h and could be specifically delivered to tumor tissues with an accumulation ratio of 12.8%. Upon the fluorescence imaging-guided PDT/PTT treatments, the tumors were completely eliminated without obvious side effects. The results suggest that the GNR-HA-ALA/Cy7.5-HER2 hold great potential for breast cancer therapy.
关键词： Triple-responsive drug release,Hyaluronic acid,Gold nanorod,Photodynamic and photothermal dual-therapy,Targeted delivery
更新于2025-09-10 09:29:36