Fabrication of a Macroporous Microwell Array for Surface‐Enhanced Raman Scattering

Abstract

Here, a colloidal templating procedure for generating high‐density arrays of gold macroporous microwells, which act as discrete sites for surface‐enhanced Raman scattering (SERS), is reported. Development of such a novel array with discrete macroporous sites requires multiple fabrication steps. First, selective wet‐chemical etching of the distal face of a coherent optical fiber bundle produces a microwell array. The microwells are then selectively filled with a macroporous structure by electroless template synthesis using self‐assembled nanospheres. The fabricated arrays are structured at both the micrometer and nanometer scale on etched imaging bundles. Confocal Raman microscopy is used to detect a benzenethiol monolayer adsorbed on the macroporous gold and to map the spatial distribution of the SERS signal. The Raman enhancement factor of the modified wells is investigated and an average enhancement factor of 4 × 104 is measured. This demonstrates that such nanostructured wells can enhance the local electromagnetic field and lead to a platform of ordered SERS‐active micrometer‐sized spots defined by the initial shape of the etched optical fibers. Since the fabrication steps keep the initial architecture of the optical fiber bundle, such ordered SERS‐active platforms fabricated onto an imaging waveguide open new applications in remote SERS imaging, plasmonic devices, and integrated electro‐optical sensor arrays.

Maximizing surface-enhanced Raman scattering sensitivity of surfactant-free Ag-Fe3O4 nanocomposites through optimization of silver nanoparticle density and magnetic self-assembly

“…From the measured SERS enhancements, we can evaluate the role played by the gap size and density of Ag-NPs in different nanostructures. The Enhancement Factor (EF) 43,44 can be calculated quantitatively according to the following formula: [45][46][47] EF ¼ ðI SERS =N SERS Þ=ðI 0 =N 0 Þ; where I SERS and N SERS are the Raman peak intensity values and the total number of molecules adsorbed on the prepared substrate, and I 0 and N 0 are the corresponding parameters for the control sample (5 ll, 5 mM R6G solution deposited on a Si substrate in our experiment). This calculation is based on the fact that the intensity of the collected SERS signal is proportional to the total number of molecules if the molecules are at a low concentration level.…”

SERS Effects in Silver‐Decorated Cylindrical Nanopores

“…These simulations coupled with experimental results suggested that nanopore diameters of around 400 nm, the incorporation of the nanoparticle dimers within the first 10 μm beneath the surface, and keeping the light transmittance above 50% are all critical to achieve SERS substrates that show enhancement factors exceeding 10 10 for the selected benchmark Raman marker, benzenethiol (BT). The observed record enhancement factor is four orders of magnitude better than that commonly reported for this marker on 2D substrates of gold and silver nanostructures 48–50…”

Fabricating Silver Nanoparticles on Thin Silicon Nanowalls for Highly Sensitive Surface-Enhanced Raman Scattering

“…We used the CO stretching signal of R6G at 611 cm ¹1 as the characteristic peak (the strongest one in the range 5501800 cm ¹1 in this study) to calculate the EFs of the SERS sensitivity. We evaluated the EFs using the equation 19) EF…”