Immobilization of Cubic Silver Plasmonic Nanoparticles on TiO₂ Nanotubes, Reducing the Coffee Ring Effect in Surface-Enhanced Raman Spectroscopy Applications

Abstract

Surface-enhanced Raman spectroscopy (SERS) substrates prepared by immobilizing silver cubic nanoparticles (Ag CNPs) on titanium dioxide nanotubes (TiO2 NTs) were used for investigations of the “coffee ring” (CR) effect and its impact on spatial reproducibility of measured Raman signals in comparison with flat surfaces (Ti and Si) where the CR effect is usually significant. The immobilization of nanoparticles from drops, which is a very simple technique, usually does not permit a homogeneous distribution of deposited NPs because there is significant accumulation of the material at the boundary of the drying area. Our proposed SERS substrates effectively reduced the CR effect through the use of well-ordered nanostructures where a smaller number of Ag CNPs were transferred to the boundary region. It was not only the surface morphology that was important but also the physicochemical properties of TiO2 NTs, such as wettability. The wettability of the prepared samples was determined by measuring the static water contact angle (WCA), and the chemical composition near the boundary of the drying area was studied using Auger electron spectroscopy. The morphology of the substrates obtained was characterized using scanning electron microscopy. Our studies showed that reducing the coffee ring effect increased the spatial reproducibility of the measured SERS signal in the area of the deposited CNPs. Therefore, the platforms obtained may be very useful in commercial SERS applications.

Filter paper based SERS substrate for the direct detection of analytes in complex matrices

“…drop-casting, which dries into a very non-uniform nanoparticle coffee-ring. 21,26,[33][34][35] The corresponding AFM images of the film on glass (Fig. 2B-D) indeed show that the film is not featureless but rather is composed of fused flatted disks <100 μm in diameter and <1 μm thick, which are the result of partly dried droplets sticking to the surface and then evaporating to dryness.…”

“…Moreover, the presence of the HEC polymer allows the nanoparticle aggregates to be deposited uniformly on the paper substrate, which has been extremely challenging for simple colloids dried onto solid supports. 25,26 Experimental Chemicals Gold(III) chloride hydrate (>99%), sodium chloride (>99.5%, sodium citrate tribasic dihydrate (>99%), thiram (97%), crystal violet dye (anhydrous, ≥90.0%), albumin (98%), melamine (>99%), and Whatman filter paper were purchased from Sigma-Aldrich. Hydrochloric acid, nitric acid and hydroxyethyl cellulose were purchased from Honeywell Fluka.…”

Substrates for Surface-Enhanced Raman Scattering Formed on Nanostructured Non-Metallic Materials: Preparation and Characterization

“…It is also possible to attach previously synthesized plasmonic nanoparticles to TiO 2 nanotubes [ 24 , 25 ]. In such a case, one can attach a large number of very similar (having practically the same shape and size) plasmonic nanoparticles to the TiO 2 nanotubes.…”

“…In such a case, one can attach a large number of very similar (having practically the same shape and size) plasmonic nanoparticles to the TiO 2 nanotubes. For example, Ambroziak et al immobilized previously synthesized cubic silver nanoparticles on TiO 2 nanotubes [ 25 ]. Cubic silver nanoparticles have been synthesized using the polyol method developed by Skrabalak et al [ 26 ].…”

Plasmonic Spherical Nanoparticles Coupled with Titania Nanotube Arrays Prepared by Anodization as Substrates for Surface-Enhanced Raman Spectroscopy Applications: A Review

“…In terms of spherical nanoparticles, hot spots will be found in the interparticle spaces. Thus, in order to control hot spot distribution, it is desirable to anchor metal nanoparticles onto a solid substrate so they can be placed together in close proximity assuring stability and large enhancements [10][11][12].…”