Ag/Au Nanoparticle-Loaded Paper-Based Versatile Surface-Enhanced Raman Spectroscopy Substrates for Multiple Explosives Detection

Abstract

We present a systematic study on the fabrication, characterization of versatile, and low-cost filter paper-based surface-enhanced Raman spectroscopy (SERS) substrates loaded with salt-induced aggregated Ag/Au nanoparticles (NPs). These were demonstrated as efficient SERS substrates for the detection of multiple explosive molecules such as picric acid (5 μM), 2,4-dinitrotoluene (1 μM), and 3-nitro-1,2,4-triazol-5-one (10 μM) along with a common dye molecule (methylene blue, 5 nM). The concentrations of the dye and explosive molecules in terms of mass represent 31.98 pg, 11.45 ng, 1.82 ng, and 13.06 ng, respectively. Silver (Ag) and gold (Au) colloidal NPs were prepared by femtosecond laser (∼50 fs, 800 nm, 1 kHz) ablation of Ag/Au-target immersed in distilled water. Subsequently, the aggregated nanoparticles were achieved by mixing the pure Ag and Au NPs with different concentrations of NaCl. These aggregated NPs were characterized by UV–visible absorption and high-resolution transmission electron microscopy techniques. The SERS substrates were prepared by soaking the filter paper in aggregated NPs. The morphologies of the paper substrates were investigated using field-emission scanning electron microscopy technique. We have achieved superior enhancements with high reproducibility and sensitivity for filter paper substrates loaded with Ag/Au NPs mixed for an optimum concentration of 50 mM NaCl.

Femtosecond Laser-Induced, Nanoparticle-Embedded Periodic Surface Structures on Crystalline Silicon for Reproducible and Multi-utility SERS Platforms

“…67 To study the influence of LIPSS periodicity on the Raman signal enhancement, SERS spectra of Ag (∼15 nm) deposited onto Si LINEPSS with different periodicity were recorded and are shown in Figure 6a. As seen in Figure 6a, there are three prominent Raman bands observed at 447, 1393, and 1620 cm –1 in all SERS spectra, which are well-matched with reported MB characteristic Raman peaks, 84,85 and these modes correspond to C–N–C skeletal deformation, C–N symmetrical stretch, and C–C ring stretching, respectively. In addition, other vibrational modes were also observed at 770, 1037, 1161, and 1500 cm –1 , which is an observation that is consistent with other Raman bands of MB.…”

Surface‐enhanced Raman scattering studies of gold‐coated ripple‐like nanostructures on iron substrate achieved by femtosecond laser irradiation in water

“…PA characteristic modes are located at 820, 962, and 1,332 cm −1 , which are associated with the C‐H bending, ring breathing, and NO 2 symmetric stretching, respectively. The observed modes are in good agreement with the published literature . The detected PA concentration levels are lower owing to its smaller Raman scattering cross‐section compared with the dye molecules.…”

Explosives sensing using Ag–Cu alloy nanoparticles synthesized by femtosecond laser ablation and irradiation

“…All the observed Raman peaks at 709, 827, 937, 947, 1163, 1315, 1348 and 1373 cm À1 matched well with some of the earlier reports. 51,64 The three major characteristic modes at 827, 1315 and 1348 cm À1 were identied even at a concentration of 5 mM. The enhancement factor (EF) was estimated using the 827 cm À1 peak of PA (5 mM) and it was found to be $2.8 Â 10 4 .…”

“…5 and the observed modes well matched to the earlier reports. 14,30,51,52 The ring stretching mode of MB (1621 cm À1 ) was elected to calculate the SERS efficiency. The obtained EFs for Ag, Cu and Ag-Cu NPs were 5.5 Â 10 3 , 7.5 Â 10 2 and 7.2 Â 10 3 , respectively, and the comparison histogram is shown in Fig.…”