The Effect of Surface Modification of Gold Nanotriangles for Surface-Enhanced Raman Scattering Performance

Abstract

A surface modification of ultraflat gold nanotriangles (AuNTs) with different shaped nanoparticles is of special relevance for surface-enhanced Raman scattering (SERS) and the photo-catalytic activity of plasmonic substrates. Therefore, different approaches are used to verify the flat platelet morphology of the AuNTs by oriented overgrowth with metal nanoparticles. The most important part for the morphological transformation of the AuNTs is the coating layer, containing surfactants or polymers. By using well established AuNTs stabilized by a dioctyl sodium sulfosuccinate (AOT) bilayer, different strategies of surface modification with noble metal nanoparticles are possible. On the one hand undulated superstructures were synthesized by in situ growth of hemispherical gold nanoparticles in the polyethyleneimine (PEI)-coated AOT bilayer of the AuNTs. On the other hand spiked AuNTs were obtained by a direct reduction of Au3+ ions in the AOT double layer in presence of silver ions and ascorbic acid as reducing agent. Additionally, crumble topping of the smooth AuNTs can be realized after an exchange of the AOT bilayer by hyaluronic acid, followed by a silver-ion mediated reduction with ascorbic acid. Furthermore, a decoration with silver nanoparticles after coating the AOT bilayer with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC) can be realized. In that case the ultraviolet (UV)-absorption of the undulated Au@Ag nanoplatelets can be tuned depending on the degree of decoration with silver nanoparticles. Comparing the Raman scattering data for the plasmon driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4′-dimercaptoazobenzene (DMAB) one can conclude that the most important effect of surface modification with a 75 times higher enhancement factor in SERS experiments becomes available by decoration with gold spikes.

Construction of Plasmonic Metal@Semiconductor Core–Shell Photocatalysts: From Epitaxial to Nonepitaxial Strategies

“…NPs of Au, Ag, and Cu can display different optical properties by adjusting their composition, [34] size, [47,48] morphology, [49][50][51] structure and surface features, [52][53][54] and have been developed into the most versatile and flexibly tailored nanomaterials. Especially, these metal NPs present readily tunable colors originating from their unique LSPR effect.…”

Advances in Plasmonic Sensing at the NIR—A Review

“…So, to place the plasmonic band at 1550 nm, the nanotriangle must present a side length of 347 nm. This could be somewhat achieved by an overgrowth methodology, as presented by Koetz et al [ 135 ], more easily by NSL, as presented by Rahaman et al [ 136 ], or another lithographic methodology. Regarding their refractometric properties, works such as the one presented by Soares et al [ 137 ], with Au nanotriangles, have shown RI sensitivities of 468 nm/RIU at wavelengths of 750 nm.…”

“…Later, Kuttner et al [ 134 ] synthesized Au nanotriangles through the seed-growth methodology where an overgrowth of Au could create these nanostructures with a 175 nm side-length, therefore presenting a significant redshift of the plasmonic band towards the NIR. The overgrowth methodology was further developed by Koetz et al [ 135 ] by modifying the Au nanotriangles surface with smaller Ag NPs, creating the ability to tune the LSPR band from 800 to 1300 nm.…”

Progress, Opportunities, and Challenges of Troponin Analysis in the Early Diagnosis of Cardiovascular Diseases

“…SERS have received much attention in various analytical and imaging applications due to their high sensitivity, capabilities of unlabeled identification, and rapid detection . Usually, precious metals (e.g., gold or silver nanoparticles) are used as plasmonic signal enhancers or Raman-active signals themselves . The detection efficiency depends on the Raman cross-section of reporter molecules and on the enhancing properties of plasmonic nanoparticles.…”