SERS substrates fabricated with star-like gold nanoparticles for zeptomole detection of analytes

Abstract

This work presents the design of substrates for Surface Enhanced Raman Scattering (SERS) using star-like gold nanoparticles which were synthesized using a wet chemical method and functionalized with 1-dodecanethiol. This molecule allowed us to obtain a spacing of ∼2.6 nm among gold stars, which promoted the generation of SERS hotspots for single molecule detection. The gold nanoparticles were deposited on silicon substrates or on gold coated silicon substrates by using the Langmuir-Blodgett method which permitted the zeptomole detection of Rhodamine B (total moles per laser spot area). The Raman enhancement factor (EF) achieved for this level of detection was 10(12), and was obtained on the SERS substrate fabricated with the configuration: Si/Au film/Au nanoparticles. Raman spectra of the molecules TWEEN 20 and p-terphenyl were also measured in order to elucidate the effect of the molecule's length on the enhancement factor. According to these results, our SERS substrates without the gold film are useful for a minimum detection level of ∼10(-14) moles of analytes with sizes equal to or less than 1.3 nm and ∼10(-18) moles of analytes with the gold film (total moles per sample).

Nanomolar detection of glucose using SERS substrates fabricated with albumin coated gold nanoparticles

“…Also, we can have in our system two effects which can improve the Raman scattering: the first one is the enhancement due to dipolar fields of the particle plasmon resonance, while the second one is a purely geometric factor identified in literature as the lightning rod factor 37,38 . Thus, higher EFs are possible with gold nanostars in comparison to spherical nanoparticles 30,31 .…”

“…Those substrates have been fabricated with cheap methods, low cost materials and their reproducibility have been good 21,22 . In this approach, A. Ceja-Fdez et al used silica coated multibranched gold nanoparticles (MBGNs) to detect α-Glucose in solution and the minimum level of detection reached was 5mM 30 , which is the range of Glucose in human blood (4.4mM-6.6mM) 23,24 , but a poor resolution in the main peaks of Glucose is presented.…”

Optimizing silver‐capped silicon nanopillars to simultaneously realize macroscopic, practical‐level SERS signal reproducibility and high enhancement at low costs

“…A number of SERS-active metallic nanoparticles in colloidal solutions have been synthesized, including shellisolated nanoparticles, [10] core-shell nanoparticles, [11] and nanoparticles with sharp features. [12,13] The main advantage of them is their high EFs caused by (a) intraparticle or interparticle plasmonic couplings and (b) lightning-rod effect that is specifically pronounced in metallic nanoparticles with sharp features. Since EF is extremely sensitive to the interparticle spacing, it is necessary to control the size of the gap junctions between nanoparticles to achieve a spatially uniform EF.…”

SERS-active Au/SiO_2 clouds in powder for rapid ex vivo breast adenocarcinoma diagnosis

“…However, for biological samples, it is necessary to decrease the power of the laser source, which results in a reduction of the signal used to extract information from the samples [10]. To overcome this issue, surface-enhanced Raman spectroscopy (SERS) has been used as an ultrasensitive and non-destructive spectroscopic technique that can provide specific molecular information of analytes present in concentrations relevant to medical applications [11,12]. SERS increases the Raman signals of molecules near metal nanostructures, which are typically composed of noble metals such as gold and silver [13].…”

“…This adsorption promotes the specific interaction and localization of the metallic nanoparticles at suitable distances from target biomolecules, generating the optimal conditions for SERS [11,12,15,16].…”