SERS-Active Ag Nanoparticles on Porous Silicon and PDMS Substrates: A Comparative Study of Uniformity and Raman Efficiency

Abstract

Silver-coated porous silicon and polydimethylsiloxane (PDMS) are systematically analyzed as substrates for surface-enhanced Raman scattering (SERS). They were selected as representative metal−dielectric nanostructures characterized by different morphology and substrate dielectric constant which is reflected in the electromagnetic near-field intensity spectra. The study is conducted using 4mercaptobenzoic acid as probe molecule with the aim to compare the scattering efficiency and the homogeneity of the Raman signal on the selected substrates. A larger SERS enhancement is evidenced for the silicon-based plasmonic nanostructures (>10 6 , despite the electronic off-resonant excitation of the analyte). On the other hand, the silvered elastomeric substrates, characterized by a good Raman efficiency, show good repeatability featured by a low inter-and intrasubstrate standard deviation of the SERS signal intensity, which make them suitable for quantitative analysis. The influence of the excitation wavelength on such properties is deeply discussed taking into account experimental results and 3D modeling.

Au Nanoparticles–Mesoporous TiO2 Thin Films Composites as SERS Sensors: A Systematic Performance Analysis

“…The pNTP concentration for these experiments was 4x10 -4 M, so as to ensure that the probe molecule reached the whole metal NP surface, including nanometric gaps between NPs, thereby enabling the study of all the available surface. 51 The obtained results are summarized in Figure 5. SERS signal intensity was found to depend linearly on acquisition time ( Figure S9, SI), and, although this is not an absolute parameter, a low minimum acquisition time is correlated with a greater SERS sensitivity.…”

Gold nanoparticle assembly on porous silicon by pulsed laser induced dewetting

“…PS coated with noble metal NPs, such as Au and Ag, has also been extensively studied for surface enhanced Raman scattering (SERS) substrates. [8][9][10] The most commonly used methods for the deposition of metal NPs on PS are the wet chemical techniques, including drop casting of metal colloidal solutions, 3,5,6 metal-assisted chemical etching of silicon, 4,11 immersion plating, 9,10,12 electroplating, 7,13 and thermal decomposition of metal salts. 14 These wet chemical methods are oen simple, inexpensive, and applicable for high throughput production, however they possess certain drawbacks including long synthesis time, inhomogeneous NP loading, and NP aggregation.…”

Composite‐Scattering Plasmonic Nanoprobes for Label‐Free, Quantitative Biomolecular Sensing

“…Figure A shows the spectra recorded from various kinds of substrates after baseline removal. The Raman spectra were normalized with the silicon background peak at 520 cm −1 . Several vibrational peaks in the range of 900–1800 cm −1 are identified in the spectrum, 1001 cm −1 (phenylalanine), 1321 cm −1 (amide III), 1335 cm −1 (CH 3 CH 2 wagging), 1446 cm −1 (CH 2 deformation), 1583 cm −1 (CC bending mode of phenylalanine), and 1652 cm −1 (amide I) .…”

“…The Raman spectra were normalized with the silicon background peak at 520 cm −1 . Several vibrational peaks in the range of 900–1800 cm −1 are identified in the spectrum, 1001 cm −1 (phenylalanine), 1321 cm −1 (amide III), 1335 cm −1 (CH 3 CH 2 wagging), 1446 cm −1 (CH 2 deformation), 1583 cm −1 (CC bending mode of phenylalanine), and 1652 cm −1 (amide I) . The experimental enhancement factor, as defined elsewhere in the literature, at 1335 cm −1 (CH 3 CH 2 wagging) for the SNPG‐annealed sample is about 22 whereas for STG it is about 14.…”

“…[63] Several vibrational peaks in the range of 900-1800 cm −1 are identified in the spectrum, 1001 cm −1 (phenylalanine), 1321 cm −1 (amide III), 1335 cm −1 (CH 3 CH 2 wagging), 1446 cm −1 (CH 2 deformation), 1583 cm −1 (CC bending mode of phenylalanine), and 1652 cm −1 (amide I). [63] The experimental enhancement factor, as defined elsewhere in the literature, [64] at 1335 cm −1 (CH 3 CH 2 wagging) for the SNPG-annealed sample is about 22 whereas for STG it is about 14. Thus, both the CSPs provide enhancement to the weak Raman signal of BSA, with the SNPG sample expectedly giving better enhancement.…”