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

Bibikova, Olga; Попов, А. П.; Bykov, Alexander; Prilepskii, Artur Y.; Kordás, Krisztián; Богатырев, В. А.; Khlebtsov, Nikolai G.; Vainio, Seppo; Tuchin, Valery V.

doi:10.1117/1.jbo.20.7.076017

Cited by 21 publications

(14 citation statements)

References 59 publications

(58 reference statements)

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“…[35][36][37] The seeded growth process using 50 nm citrate spheres is among the most commonly applied strategies. 38,39 The morphology of the AuNSts was investigated with SEM and TEM. As shown in Figure 2, synthesized AuNSts with an outer diameter of approximately 90 nm have approximately 15 tips with an average length of 15 nm.…”

Section: Characterization Of Gold Nanostarsmentioning

confidence: 99%

Towards enhanced optical sensor performance: SEIRA and SERS with plasmonic nanostars

Bibikova

Haas

López‐Lorente

et al. 2017

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We report the preparation and characterization of plasmonic chip-based systems comprising self-assembled gold nanostars at silicon substrates that enable concomitantly enhanced Raman (surface enhanced Raman spectroscopy; SERS) and mid-infrared (surface enhanced infrared reflection or absorption spectroscopy; SEIRA) spectral signatures. The high-aspect-ratio structure of gold nanostars provides an increased number of hot spots at their surface, which results in an electric field enhancement around the nanomaterial. Gold nanostars were immobilized at a silicon substrate via a thin gold layer, and α-ω-dimercapto polyethylene glycol (SH-PEG-SH) linkers. The Raman and IR spectra of crystal violet (CV) revealed a noticeable enhancement of the analyte vibrational signal intensity in SERS and SEIRA studies resulting from the presence of the nanostars. Enhancement factors of 2.5 × 10 and 2.3 × 10 were calculated in SERS considering the CV bands at 1374.9 cm and 1181 cm, respectively; for SEIRA, an enhancement factor of 5.36 was achieved considering the CV band at 1585 cm.

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Section: Characterization Of Gold Nanostarsmentioning

confidence: 99%

Towards enhanced optical sensor performance: SEIRA and SERS with plasmonic nanostars

Bibikova

Haas

López‐Lorente

et al. 2017

Analyst

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“…[7][8][9][10]11 The identification of the species of bacteria through Raman spectroscopy is achieved through the detection of organic molecules on the surface of the bacterial membrane and wall. [13][14][15][16] Typically the best enhancement effect is achieved with silver induced SERS 17 . 7 The detection of a small concentration of bacteria with conventional Raman spectroscopy can demand a level of sensitivity greater than what it is capable of.…”

Section: Introductionmentioning

confidence: 99%

Detection of Listeria innocua on roll-to-roll produced SERS substrates with gold nanoparticles

et al. 2016

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The rapid and accurate detection of food pathogens plays a critical role in the early prevention of foodborne epidemics.Current bacteria identification practises, including colony counting, polymerase chain reaction (PCR) and immunological methods, are time consuming and labour intensive; they are not ideal for achieving the required immediate diagnosis. Different SERS substrates have been studied for the detection of foodborne microbes. The majority of the approaches are either based on costly patterning techniques on silicon or glass wafers or on methods which have not been tested in large scale fabrication. We demonstrate the feasibility of analyte specific sensing using mass-produced, polymer-based low-cost SERS substrate in analysing the chosen model microbe with biological recognition. The use of this novel roll-to-roll fabricated SERS substrate was combined with optimised gold nanoparticles to increase the detection sensitivity.Distinctive SERS spectral bands were recorded for Listeria innocua ATCC 33090 using an in-house build (785 nm) near infra red (NIR) Raman system. Results were compared to both those found in the literature and the results obtained from a commercial time-gated Raman system with a 532 nm wavelength laser excitation. The effect of the SERS enhancer metal and the excitation wavelength on the detected spectra was found to be negligible. The hypothesis that disagreements within the literature regarding bacterial spectral results from conditions present during the detection process has not been supported. The sensitivity of our SERS detection was improved through optimization of the concentration of the sample inside the hydrophobic polydimethylsiloxane (PDMS) wells. Immuno-magnetic separation (IMS) beads were used to assist the accumulation of bacteria into the path of the beam of the excitation laser. With this combination we have detected L i s t e r i a w i t h g o l d e n h a n c e d S E R S i n a l a b e l f r e e m a n n e r f r o m s u c h l o w s a m p l e c o n c e n t r a t i o n s a s 1 0 4 CFU/ml.Figure 10. a) A normalised concentration series for LOD estimation. b) An exponential fit for the normalised concentration series in logarithmic scale for the entire series and a linear fit for the small concentrations. c) Comparison of the 737 cm -1 peak intensity for different concentration series with 5 -10 µl dried IMS bound L. innocua ATCC 33090 samples placed with AuNPs into a 1 -1.5 mm PDMS well on top of SERS substrate. d) Comparison of baseline corrected Raman intensities for three of the concentration series. All figures are a mean of 9 measurement points with mean absolute deviations.

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“…Furthermore, in view of the potential use of nanostars as hot electron‐based photocatalysts, 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 wide range applicability, unfortunately, no established protocols exist to selectively coat the nanostar core while leaving the tips exposed. In addition, known protocols for silica etching would be too aggressive for the delicate nanostar morphology and would lead to tip reshaping …”

Section: Figurementioning

confidence: 99%

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

Cited by 21 publications

References 59 publications

Towards enhanced optical sensor performance: SEIRA and SERS with plasmonic nanostars

Towards enhanced optical sensor performance: SEIRA and SERS with plasmonic nanostars

Detection of Listeria innocua on roll-to-roll produced SERS substrates with gold nanoparticles

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

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