Understanding the role of AgNO<sub>3</sub> concentration and seed morphology in the achievement of tunable shape control in gold nanostars

Atta, Supriya; Beetz, Michael; Fabris, Laura

doi:10.1039/c8nr07615d

Cited by 118 publications

(167 citation statements)

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“…1,2 One special feature of noble metals on the nanometer scale is the localized surface plasmon resonance (LSPR). 3,4 The LSPR strongly depends on the shape and size of the gold nanoparticles, e.g., nanospheres, 5 nanorods, 6 nanotriangles, 7,8 nanostars, [9][10][11][12] or multibranched nanoparticles, 13 and opens new elds of application. 14,15 Asymmetric particles allow for creating very large absorption and scattering cross sections in the near-infrared (NIR) region, which is of special interest for surface enhanced Raman scattering (SERS) applications in biological systems.…”

Section: Introductionmentioning

confidence: 99%

Spiked gold nanotriangles: formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Spiked gold nanotriangles: formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis

et al. 2020

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“…To gain further insight into the effect of silica on the LSPR of the gold nanostars, we have investigated the silica coating and etching of 6‐branched gold nanostars (Figure ) that we have recently reported . These particles are characterized by LSPR bands substantially narrower than those of the more traditional surfactant free gold nanostars, which are also highly sensitive towards the dielectric properties of the surrounding medium . Interestingly, we have observed a similar behavior in these particles compared to their surfactant‐free counterparts, characterized by a 35 nm red shift of the LSPR after silica coating followed by a blue‐shift to 31 nm when the silica shell was etched with NABH 4 (Figure d).…”

Section: Figurementioning

confidence: 61%

“…Gold nanostars are a subtype of colloidal nanomaterial that consists of a central core from which multiple sharp branches protrude . They exhibit intense and tunable localized surface plasmon resonances (LSPRs) in the near‐infrared (NIR), that have been leveraged in biological applications, especially for multimodal imaging and photothermal therapy .…”

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

“…Synthesis of Silica Coated and Silica Etched 6‐branched Gold Nanostars. 6‐branched gold nanostars, and silica coated and etched 6‐branched gold nanostars was synthesized by following our previously reported method . Briefly, 50 ml of 6‐branched gold nanostars were first capped with CTAB by addition of 10 mL of 0.2 M CTAB.…”

Section: Figurementioning

confidence: 99%

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Highly Tunable Growth and Etching of Silica Shells on Surfactant‐Free Gold Nanostars

2019

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Herein, we report an efficient method to coat gold nanostars with a silica shell of variable thickness and then tunably etch it by using a mild silica etching reagent, NaBH 4 . This method generates a novel type of nanostar coating in which silica only covers the core, leaving the tips variably exposed.Gold nanostars are a subtype of colloidal nanomaterial that consists of a central core from which multiple sharp branches protrude. [1][2][3][4] They exhibit intense and tunable localized surface plasmon resonances (LSPRs) in the near-infrared (NIR), that have been leveraged in biological applications, especially for multimodal imaging and photothermal therapy. [5][6][7][8] Owing to their resonances in the NIR and intense near-field enhancements, nanostars can afford intense imaging response and photothermal heating without substantial tissue damage, which is important in view of clinical implementations. To better understand how to best leverage these particles, it is first necessary to characterize their physical and optical properties, and to do so quantitatively, while also trying to design predictive tools that could aid us in tuning their synthesis to achieve the desired behavior. As a first step toward this goal, we have recently implemented an experimental-computational approach to calculate the extinction coefficient of gold nanostars employing finite element (FEM) calculations, obtaining very similar results to what achieved by Hamad-Schifferli and co-workers, who employed discrete dipole approximation (DDA) calculations. [9][10] The evaluation of extinction coefficients for plasmonic nanoparticles is the gateway to quantification and real life applicability; nonetheless, it is extremely complex for nanoparticles of complex morphology such as nanostars, and often not practical. Therefore, we hypothesized that by going back to the drawing board, and cleverly designing SiO 2 coating protocols, which would leave only the nanostar spikes exposed from the silica shell, we could still leverage the intense near-field enhancements at the tips while having to deal with a much more simplified morphology. Moreover, the partial silica coating would increase colloidal stability and biocompatibility, leading to improved applicability in vitro. As we previously observed, [11] the optical properties of tunable silica shells can be reflected in the overall dielectric function of the core-shell colloid, leading to surface-enhanced Raman scattering (SERS) enhancement factors that depend both on the extent of tip exposure and the thickness of the silica shell, providing SERS tags of variable brightness. Furthermore, in view of the potential use of nanostars as hot electron-based photocatalysts, [12][13] the possibility to isolate the tips from the remainder of the nanostar, thus enabling us to prove their role as source of hot electrons, could lead to interesting fundamental studies on the generation and fate of these hot carriers. While protocols exist to coat nanostars with silica, and silica coated nanostars have found wi...

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Plasmonic Nanostars: Unique Properties That Distinguish Them from Spherical Nanoparticles from a Biosensing Perspective

Tukova,

Nguyen,

Garcia‐Bennett

et al. 2024

Advanced Optical Materials

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Over the past three decades, plasmonic nanostructures, particularly spherical ones, have seen remarkable advancements. Recently, attention has shifted toward anisotropic nanoparticles, especially star‐shaped/branched structures such as plasmonic nanostars (PNS), due to their distinct properties. PNS offers superior electromagnetic enhancement effects, larger surface areas, and as well as non‐linear and unusual photothermal properties, setting them apart from spherical counterparts. Despite significant progress in synthetic methods and characterization of the particles, challenges remain in transitioning PNS technology into practical use. In this perspective article, the distinctive attributes of PNS in biosensing applications are discussed, beginning with an exploration of synthesis methodologies. Their optoelectronic properties are examined and discussed how these properties influence their interaction with different molecules from a biosensing perspective. With a focus on PNS, detailed insights are offered into their unique properties, current applications, and future potential. By fostering discussion and understanding of PNS development, this article aims to facilitate the translation of PNS technology into practical applications, encouraging targeted improvements and advancements.

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Understanding the role of AgNO₃ concentration and seed morphology in the achievement of tunable shape control in gold nanostars

Abstract: Gold nanostars are one of the most fascinating anisotropic nanoparticles.

Cited by 118 publications

References 48 publications

Spiked gold nanotriangles: formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis

Spiked gold nanotriangles: formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis

Highly Tunable Growth and Etching of Silica Shells on Surfactant‐Free Gold Nanostars

Plasmonic Nanostars: Unique Properties That Distinguish Them from Spherical Nanoparticles from a Biosensing Perspective

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Understanding the role of AgNO3 concentration and seed morphology in the achievement of tunable shape control in gold nanostars

Abstract: Gold nanostars are one of the most fascinating anisotropic nanoparticles.

Cited by 118 publications

References 48 publications

Spiked gold nanotriangles: formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis

Spiked gold nanotriangles: formation, characterization and applications in surface-enhanced Raman spectroscopy and plasmon-enhanced catalysis

Highly Tunable Growth and Etching of Silica Shells on Surfactant‐Free Gold Nanostars

Plasmonic Nanostars: Unique Properties That Distinguish Them from Spherical Nanoparticles from a Biosensing Perspective

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Understanding the role of AgNO₃ concentration and seed morphology in the achievement of tunable shape control in gold nanostars