Reusable plasmonic substrates fabricated by interference lithography: a platform for systematic sensing studies

Siegfried, Thomas; Kind, Martin; Terfort, Andreas; Martin, Olivier J. F.; Zharnikov, Michael; Ballav, Nirmalya; Sigg, H.

doi:10.1002/jrs.4163

Cited by 25 publications

(25 citation statements)

References 36 publications

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“…37 The SERS spectra looked similar to each other; six major peaks were visible in all the systems and a negligible shift observed in the peak positions reflects similar bonding (covalent attachment to Au or Ag via S atom) and upright orientation of TPDT on the surface of all NPs. 39 However, few peaks of TPDT appeared characteristically on the Ag NPs and were apparently absent in the Au NPs which could be attributed to a chemical enhancement effect. 40 Specifically, the relative intensity ratio between the peaks at ∼1185 and ∼1210 cm −1 gradually decreased reaching almost zero upon increasing concentration of Au up to 100% which is remarkable and strongly supports formation of "homogeneously alloyed" NPs by ruling out the possibility of surface enrichment by Ag atoms.…”

Section: Resultsmentioning

confidence: 98%

Homogeneously-Alloyed Gold–Silver Nanoparticles as per Feeding Moles

et al. 2015

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Wet-chemical methods involving the coreduction of HAuCl 4 and AgNO 3 have been proven particularly suitable for producing stable Au−Ag alloy NPs with controllable structure−property relationship. However, very poor-solubility of AgCl in aqueous medium and intrinsically different surface energies of Au and Ag remained detrimental-factors in synthesizing so-called "alloy" NPs above the solubility-product of AgCl. Here, we report a robust coreduction procedure for producing citrate-stabilized "homogeneously alloyed" Au−Ag NPs of average size sub-10 nm at room-temperature upon simultaneously overcoming the detrimental factors by a simple reagent NH 4 OH. The alloy NPs revealed a high-degree of crystallinity, composition-tunable surface plasmon resonance (SPR) behavior, controlled-catalysis, biocompatibility, surface enhance Raman scattering (SERS) activity and high-chemical stability. The alloy NPs could withstand corrosive chemical environment and be easily transferred from aqueous medium to various organic media. Fusion of NPs under high-energy electron-beam suggested an inertial coalescence. Our method may lead to the developments of metallic and bimetallic alloy NPs in the fulfillment of various applications in the future.

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Section: Resultsmentioning

confidence: 98%

Homogeneously-Alloyed Gold–Silver Nanoparticles as per Feeding Moles

et al. 2015

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“…The same pattern could also withstand several successive cleaning runs without loosing the SERS enhancement. 12 For those experiments, the analyte was removed by 20 min exposure to an Ultraviolet source followed by redeposition of the analyte monolayer. These additional experiments are shown in Figure S2 of the Supporting Information.…”

Section: Resultsmentioning

confidence: 99%

Engineering Metal Adhesion Layers That Do Not Deteriorate Plasmon Resonances

et al. 2013

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G reat amounts of numerical and experimental investigations have been devoted to boosting the signal of plasmonic sensors fabricated from noble metal nanoantennas with sharp edges or with gaps separated by a few nanometers. 1À8 The field enhancement depends mainly on the ability to couple incident photons to localized surface plasmon modes. Such resonant modes are prone to damping by scattering and absorption in the metal and its surrounding materials, thus, limiting the achievable enhancement. 9 By interference with subradiant modes, as in Fano resonant systems, radiative losses can be reduced, but not suppressed completely. 10,11 In any case, the field enhancement is often severely reduced by the presence of adhesion layers. These layers are required to pin the noble metals to the substrate, particularly when the fabrication requires lift-off and sonication or when the applications demand high structural robustness. 12 Thanks to their broad availability and process compatibility with the evaporation of the noble metals, Cr and Ti are the most commonly used adhesion materials, with typical thicknesses ranging between 1 and 10 nm. 13À15 Although the existence of the adhesion layer is an important part of the plasmonic structure, its influence on the near and far field of the plasmonic modes is often neglected. 9,16 The perturbation of the plasmon resonance can be derived from the real and imaginary parts of the adhesion materials dielectric function which affects the refractive index locally and introduces absorption. Under such circumstances, surface and localized surface plasmon resonances (SPR and LSPR) are red-shifted and broadened, leading to reduced signal sensitivities, caused by the reduced quality factor Q of the resonant mode. 17À21 As a consequence, processes where high near-field amplitudes are needed, such as surface enhanced Raman scattering (SERS) and fluorescence, 16 ABSTRACT Adhesion layers, required to stabilize metallic nanostructures, dramatically deteriorate the performances of plasmonic sensors, by severely damping the plasmon modes. In this article, we show that these detrimental effects critically depend on the overlap of the electromagnetic near-field of the resonant plasmon mode with the adhesion layer and can be minimized by careful engineering of the latter. We study the dependence of the geometrical parameters such as layer thickness and shape on the near-field of localized plasmon resonances for traditional adhesion layers such as Cr, Ti, and TiO 2 . Our experiments and simulations reveal a strong dependence of the damping on the layer thickness, in agreement with the exponential decay of the plasmon near-field. We developed a method to minimize the damping by selective deposition of thin adhesion layers (<1 nm) in a manner that prevents the layer to overlap with the hotspots of the plasmonic structure. Such a designed structure enables the use of standard Cr and Ti adhesion materials to fabricate robust plasmonic sensors without deteriorating their sensitivity.

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“…[3,37] Different approaches to this problem have been used in the past, with promisingr esults, such as electrochemicals tripping, [74] dippingi ns olutions of concentrated acid, [75] ultraviolet-ozone (UVO) cleaning, [76] or metal nanostructures supported on photocatalytic oxides (e.g. The need for reusable substrates for SERS analysis appeared recently as ac ost-effective strategy for repeated analytical assays.…”

Section: Discussionmentioning

confidence: 99%

Magnetically Assembled SERS Substrates Composed of Iron–Silver Nanoparticles Obtained by Laser Ablation in Liquid

et al. 2016

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The widespread application of surface-enhanced Raman scattering (SERS) would benefit from simple and scalable self-assembly procedures for the realization of plasmonic arrays with a high density of electromagnetic hot-spots. To this aim, the exploitation of iron-doped silver nanoparticles (NPs) synthesized by laser ablation of a bulk bimetallic iron-silver target immersed in ethanol is described. The use of laser ablation in liquid is key to achieving bimetallic NPs in one step with a clean surface available for functionalization with the desired thiolated molecules. These iron-silver NPs show SERS performances, a ready response to external magnetic fields and complete flexibility in surface coating. All these characteristics were used for the magnetic assembly of plasmonic arrays which served as SERS substrates for the identification of molecules of analytical interest. The magnetic assembly of NPs allowed a 28-fold increase in the SERS signal of analytes compared to not-assembled NPs. The versatility of substrate preparation and the SERS performances were investigated as a function of NPs surface coating among different thiolated ligands. These results show a simple procedure to obtain magnetically assembled regenerable plasmonic arrays for repeated SERS investigation of different samples, and it can be of inspiration for the realization of other self-assembled and reconfigurable magnetic-plasmonic devices.

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Reusable plasmonic substrates fabricated by interference lithography: a platform for systematic sensing studies

Cited by 25 publications

References 36 publications

Homogeneously-Alloyed Gold–Silver Nanoparticles as per Feeding Moles

Homogeneously-Alloyed Gold–Silver Nanoparticles as per Feeding Moles

Engineering Metal Adhesion Layers That Do Not Deteriorate Plasmon Resonances

Magnetically Assembled SERS Substrates Composed of Iron–Silver Nanoparticles Obtained by Laser Ablation in Liquid

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