Engineering the Optical Properties of Gold Nanorods: Independent Tuning of Surface Plasmon Energy, Extinction Coefficient, and Scattering Cross Section

Park, Kyoungweon; Biswas, Shyamal; Kanel, Sushil R.; Nepal, Dhriti; Vaia, Richard A.

doi:10.1021/jp5013279

Cited by 81 publications

(79 citation statements)

References 46 publications

(131 reference statements)

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“…The distribution of the population was estimated using TEM imagery analysis, Figure 2h, showing a distinct welded dimer (N = 2) population (≈75% yield) in agreement with the spectroscopic measurements. [7,8,10] For single gold nanorods synthesized using seed-mediated processes, the long wavelength limit of the LSP absorption peak is ≈1.2 µm, [11] similar to the CTP nanoantenna absorption peak in Figure 2c. The high quality factor (λ CTP /fwhm) CTP absorption peaks observed in Figure 2 are attributed to the CTP mode being insensitive to the relative orientation of the individual nanorods.…”

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confidence: 74%

Widely Tunable Infrared Plasmonic Nanoantennas Using Directed Assembly

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Nita

Charipar

et al. 2017

Advanced Optical Materials

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tunable, monodisperse, high aspect ratio plasmonic nanoantennas.Very recently, molecules were used to link gold nanospheres into linear chains and the nanospheres were welded together following exposure to femtosecond laser pulses. The experimental wavelength tunability of this approach was ≈0.4 µm at near infrared wavelengths. [7] Similarly, experiments were carried out using gold nanorods, experimentally producing very polydisperse yields at near infrared wavelengths, indicating uncontrolled assembly and welding. [8] Further work refined this approach experimentally demonstrating discrete nanorod dimer nanoantennas with large and sharp absorption peaks, but used a slowly reacting aqueous based method. [9] Although this approach enabled high quality yields it is not practical for producing infrared nanoantennas due to the long assembly times and the large water absorption peaks which inhibit the ability to process and measure the suspensions at infrared wavelengths. The inability to experimentally direct and weld nanorod assemblies into higher order structures, while simultaneously producing high quality yields, has impeded progress into infrared wavelengths. If infrared plasmonic nanoantennas are to be efficiently realized, ushering in a fundamental nanotechnology building block, then these approaches must be generalized.The generalized experiment is illustrated in Figure 1a. Gold nanorods were concatenated end to end with dithiol molecules forming linear nanorod chains of controllable length (Figure 1a, background). The chains are welded together as they enter the femtosecond laser beam (red) producing tunable infrared plasmonic nanoantennas (Figure 1a, foreground). The experiment was monitored in situ with a spectrometer and white light source (white beam) orthogonal to the laser light (Experimental Section).Initially, aqueous suspensions of gold nanorods were stabilized with a bilayer of hexadecyltrimethylammonium bromide (CTAB) coating the cylindrical portion of the nanorods, Figure 1b. To enable the end to end assembly, the nanorods were then suspended in an acetonitrile:water (8:1) solution (Experimental Section). This allows the nanorods and nonpolar molecular linkers (1,6-hexanedithiol) to be costabilized in the same suspension by removing the outer most CTAB layer from the nanorods exposing the nonpolar tails of the CTAB Infrared plasmonic nanoantennas are key building blocks in nanotechnology. By coupling and confining light into spatial volumes below the diffraction limit, infrared plasmonic nanoantennas provide unique opportunities to sense and signal at nanometer length scales for energy harvesting, as light sources, and in nanomedicine applications. However, in contrast to their radio-and microwave counterparts, widespread use of plasmonic nanoantennas has been limited, due in part to the inability to synthesize these structures maintaining nanoscale precision in large batches with uniform yields. This communication describes a directed assembly approach to generate large quantities of infrared pl...

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confidence: 74%

Widely Tunable Infrared Plasmonic Nanoantennas Using Directed Assembly

Fontana

Nita

Charipar

et al. 2017

Advanced Optical Materials

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“…The lower detection limits (LDLs) for ICP-OES and AAS were 7 and 0.05 lg L -1 , respectively, and the LDL for chloride was 5 lg L -1 . The methods for total Ag analysis have previously been applied and reported by our group and our collaborators (Flory et al 2013;Impellitteri et al 2013;Park et al 2014). All column experiments were performed in duplicate and only average values based on results with less than 10 % deviation are reported.…”

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confidence: 99%

Influence of natural organic matter on fate and transport of silver nanoparticles in saturated porous media: laboratory experiments and modeling

et al. 2015

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Understanding the fate and transport of silver nanoparticles (AgNPs) is of importance due to their widespread use and potential harmful effects on humans and the environment. The present study investigates the fate and transport of widely used Creighton AgNPs in saturated porous media. Previous investigations of AgNP transport in the presence of natural organic matter (NOM) report contradictory results regarding how the presence of NOM affected the stability and mobility of AgNPs. In this work, a nonreactive tracer, AgNPs and a mixture of AgNPs and NOM were injected into a background solution (0.01 mM of NaNO 3 ) flowing through laboratory columns packed with water-saturated glass beads to obtain concentration versus time breakthrough curves. Transport of AgNPs in the presence of NOM was simulated with a model that accounted for both reversible and irreversible attachment. Based upon an analysis of the AgNP breakthrough curves, it was found that addition of NOM at concentrations ranging from 1 to 40 mg L -1 resulted in significant decreases in both the zeroth and first moments of the breakthrough curves. These observations may be attributed to NOM promoting AgNP aggregation and irreversible attachment. Raman and surface-enhanced Raman scattering analysis of NOM-AgNP mixtures revealed that a possible interaction of NOM with AgNP occurred through the carboxylic moieties (-COO -) located in the immediate vicinity of the metallic surface. At higher concentrations of NOM, both the zeroth and first moments of the breakthrough curves increased. Based on modeling and the literature, we hypothesize that as the NOM concentration increases, it begins to coat both the AgNPs and the glass beads, leading to a situation where AgNP transport may be described in the same way that transport of a sorbing hydrophobic compound partitioning to an immobile organic phase is typically described, assuming reversible, rate-limited sorption.

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“…4,5 Branched and star-shaped gold NPs become perspective candidates for use as a plasmon-resonant core of nanocomposites (NCs) due to their strong absorption in the near-infrared (NIR) wavelength range, optimal for the "diagnostic/therapeutic window" with enhanced light penetration into biotissue. Although some experimental data on the relationship between the absorption and scattering properties of nanospheres and nanoshells, 13,14 nanorods, 15,16 and nanocages 17 are available, the majority of studies are devoted to the absorption properties of plasmonic NPs. 12 Integration of plasmon-resonant nanoparticles (PRNPs) into biomedical applications requires the ability to change their absorption and scattering properties and tune the position of the resonance peak and associated scattering and absorption for optimal use.…”

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Optical properties of plasmon-resonant bare and silica-coated nanostars used for cell imaging

et al. 2015

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We synthesized and characterized gold nanostars and their silica-coated derivatives with 7- to 50-nm shell thicknesses as contrast agents for optical imaging. The scattering and absorption coefficients of the nanoparticles (NPs) were estimated by means of collimated transmittance and diffuse reflectance/transmittance analyses. The contrasting properties of the nanostructures were studied in optical coherence tomography glass capillary imaging. The silica-coated nanostars with the thickest shell have higher scattering ability in comparison with bare nanostars. Viability assays confirmed weak in vitro toxicity of nanostructures at up to ∼200-μg/mL concentrations. We showed real-time visualization of nanostars in both agarose and cultured cells by analyzing the backscattering signal using a conventional laser confocal microscope. The signal intensity detected from the silica-coated NPs was almost 1.5 times higher in comparison with bare nanostars. To the best of our knowledge, this is the first time that conventional laser confocal microscopy was applied in combined scattering and transmitted light modes to detect the backscattered signal of gold nanostars, which is useful for direct monitoring of the uptake, translocation, and accumulation of NPs in living cells.

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Engineering the Optical Properties of Gold Nanorods: Independent Tuning of Surface Plasmon Energy, Extinction Coefficient, and Scattering Cross Section

Cited by 81 publications

References 46 publications

Widely Tunable Infrared Plasmonic Nanoantennas Using Directed Assembly

Widely Tunable Infrared Plasmonic Nanoantennas Using Directed Assembly

Influence of natural organic matter on fate and transport of silver nanoparticles in saturated porous media: laboratory experiments and modeling

Optical properties of plasmon-resonant bare and silica-coated nanostars used for cell imaging

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