Intrinsic and well-defined second generation hot spots in gold nanobipyramids <i>versus</i> gold nanorods

Pardehkhorram, Raheleh; Bonaccorsi, Simone; Zhu, Huihui; Gonçales, Vinícius R.; Wu, Yanfang; Liu, Jingquan; Lee, Nanju Alice; Tilley, Richard D.; Gooding, J. Justin

doi:10.1039/c9cc02730k

Cited by 32 publications

(28 citation statements)

References 33 publications

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“…The ensuing composite materials exhibit polarization‐dependent surface plasmon resonance (SPR) spectra that can be controlled by facile electric switching. As compared to colloidal dispersions of plasmonic nanorods, consistent with the studies for isotropic fluid host media, [ 20 , 21 , 22 , 23 , 24 ] GNPBs exhibit high monodispersity of geometric dimensions and provide more narrow surface resonance spectra. In the form of nematic colloidal dispersions, GNPBs exhibit electrically reconfigurable SPR spectra with electrically controlled spectral shifting of SPR peaks.…”

Section: Introductionsupporting

confidence: 77%

“…Surface functionalization of GNPBs with PEG‐SH preserves geometry of these particles while also providing a uniform surface grafting of these polymer molecules on all their facets (Figure 1a–f ). While SPR properties of GNPBs have been studied both experimentally and theoretically, [ 20 , 21 , 22 , 23 , 24 ] these previous works revealed and explained how GNPBs exhibit polarization dependence of SPR at the level of individual nanoparticles but do not retain such polarization dependence properties within colloidal dispersions in isotropic solvents. Figure 1g shows how alignment and polarization dependence of SPR can be imposed by unidirectional shearing.…”

Section: Resultsmentioning

confidence: 99%

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Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

et al. 2021

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Dispersing inorganic colloidal nanoparticles within nematic liquid crystals provides a versatile platform both for forming new soft matter phases and for predefining physical behavior through mesoscale molecular-colloidal self-organization. However, owing to formation of particle-induced singular defects and complex elasticity-mediated interactions, this approach has been implemented mainly just for colloidal nanorods and nanoplatelets, limiting its potential technological utility. Here, orientationally ordered nematic colloidal dispersions are reported of pentagonal gold bipyramids that exhibit narrow but controlled polarization-dependent surface plasmon resonance spectra and facile electric switching. Bipyramids tend to orient with their C 5 rotation symmetry axes along the nematic director, exhibiting spatially homogeneous density within aligned samples. Topological solitons, like heliknotons, allow for spatial reorganization of these nanoparticles according to elastic free energy density within their micrometer-scale structures. With the nanoparticle orientations slaved to the nematic director and being switched by low voltages ≈1 V within a fraction of a second, these plasmonic composite materials are of interest for technological uses like color filters and plasmonic polarizers, as well as may lead to the development of unusual nematic phases, like pentatic liquid crystals.

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Section: Introductionsupporting

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

et al. 2021

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“…11 The majority of the enhancement effect is associated with the highly curved areas located at the nanorod tips. 16,21,22 In contrast, the longitudinal surface area possesses a modest share of the SERS amplification, while occupying more than ∼80% of the total surface area for rods with our dimensions (Figure S2).…”

Section: ■ Results and Discussionmentioning

confidence: 98%

“…Finally, the as-synthesized gold nanorods were purified by two Tip Modification of Gold Nanorods with 4-MBA. Following our previously reported procedure, 16 selective tipmodification of the rods with the Raman reporter molecules was performed by adding 4-MBA (2.5 μL, 2 mM in water) into a dispersion of gold nanorods (100 μL, OD ∼9). The mixture was then stirred at 25 °C for 2 h followed by three centrifugation cycles (13 000 rpm, 30 min) to remove the excess reagents.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Functionalized Gold Nanorod Probes: A Sophisticated Design of SERS Immunoassay for Biodetection in Complex Media

et al. 2021

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Surface-enhanced Raman scattering (SERS) probes offer considerable opportunities in label-based biosensing and analysis. However, achieving specific and reproducible performance, where low detection limits are needed in complex media, remains a challenge. Herein, we present a general strategy employing gold nanorod SERS probes and rationally designed surface chemistry involving protein resistant layers and antibodies to allow for the selective detection of species in complex media. By utilizing the ability of gold nanorods for selective surface modification, Raman reporters (4-mercaptobenzoic acid) were attached to the tips. Importantly, the sides of the nanorods were modified using a mixed layer of two different length stabilizing ligands (carboxyl-terminated oligo ethylene glycols) to ensure colloidal stability, while antibodies were attached to the stabilizing ligands. The nanoparticle interfacial design improves the colloidal stability, unlocks the capability of the probes for targeting biomolecules in complex matrices, and gives the probes the high SERS efficiency. The utility of this probe is demonstrated herein via the detection of Salmonella bacteria at the single bacterium level in complex food matrices using an anti-Salmonella IgG antibody-conjugated probe. The modular nature of the surface chemistry enables the SERS probes to be employed with a molecularly diverse range of biorecognition species (e.g., antibodies and peptides) for many different analytes, thus opening up new opportunities for efficient biosensing applications.

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“…Particularly, plasmonic nanoparticles of anisotropic shape, such as gold nanorods (AuNRs) and gold nanobipyramids (AuBPs) are known to exhibit two well-resolved bands, namely transversal and longitudinal resonance bands. Actually, AuNRs and, more recently, AuBPs are excellent SERS-active substrates, due to their strong locally enhanced electromagnetic field at their ends, generating intrinsic "hot-spots", which leads to the amplification of the Raman signal without inducing aggregation [14,15]. It is expected that such plasmonic nanoparticles can play also as efficient optical (nano)antennas able to enhance the emission rate of the fluorophore with an optimal overlapping between the absorption band and the transversal plasmon resonance band [16], but one of the difficulties in real-world chemical trace detection that must be overcome, is the intrinsic poor chemical selectivity of the plasmonic nanostructures to capture the target analytes from complex (bio)chemical samples [6,17].…”

Section: Introductionmentioning

confidence: 99%

Calligraphed Selective Plasmonic Arrays on Paper Platforms for Complementary Dual Optical “ON/OFF Switch” Sensing

et al. 2020

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Designing innovative (nano)detection platforms, respecting their low-cost and fabrication simplicity, capable to chemically detect multiple target analytes by employing the same engineered device, is still a great challenge in the multiplexed biosensor development. In this scientific context, in the current manuscript, we exploit the low-cost plasmonic calligraphy as a versatile approach to directly draw continuous plasmonic lines on Whatman paper using a regular ballpoint pen successively filled with two different anisotropic nanoparticles shapes (gold bipyramids—AuBPs and gold nanorods—AuNRs) as colloidal inks. After the efficient immobilization of the positively-charged AuBPs and AuNRs onto the paper fibres, proved by Scanning Electron Microscopy (SEM) investigations, the specificity of our as-calligraphed-paper platform is ensured by coating the selected lines with a thin layer of anionic poly(styrene sulfonate) polyelectrolyte, creating, consequently, a well-defined plasmonic array of charge-selective regions. Finally, the functionality of the well-isolated and as-miniaturized active plasmonic array is, subsequently, tested using the anionic Rose-Bengal and cationic Rhodamine 6G target analytes and proved by complementary dual optical “ON/OFF Switch” sensing (i.e. Surface-enhanced Raman Scattering sensing/metal-enhanced fluorescence sensing) onto the same plasmonic line, developing thus a simple multiplexed plasmonic array platform, which could further facilitate the well-desired biomarker detection in complex mixtures.

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Intrinsic and well-defined second generation hot spots in gold nanobipyramids versus gold nanorods

Abstract: Well-defined second-generation hot spots in end-to-end assembled gold nanobipyramids exhibit sufficient enhancement of the plasmonic field for single molecule detection.

Cited by 32 publications

References 33 publications

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

Functionalized Gold Nanorod Probes: A Sophisticated Design of SERS Immunoassay for Biodetection in Complex Media

Calligraphed Selective Plasmonic Arrays on Paper Platforms for Complementary Dual Optical “ON/OFF Switch” Sensing

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