Femtosecond Laser Fabricated Ag@Au and Cu@Au Alloy Nanoparticles for Surface Enhanced Raman Spectroscopy Based Trace Explosives Detection

Abstract

Herein we present results from our detailed studies on the fabrication of Ag@Au and Cu@Au alloy nanoparticles (NPs) using the femtosecond laser ablation in liquid technique. The NPs were obtained by ablating the pure Ag, Cu targets (bulk) in HAuCl 4 (5 mM) solution. The absorption properties of the obtained NPs colloids were characterized using UV-Visible absorption spectrometer and their size, shape, and crystallinity were investigated using the XRD, FESEM and TEM techniques. The fabricated NPs were utilized for sensing of explosive molecules such as 2,4,6-trinitrophenol (PA), 2,4-dinitrotoluene (DNT) and a common dye methylene blue (MB) using the surface enhanced Raman spectroscopy (SERS) technique. The detection limit in terms of weight was as low as few nano-grams in the case of nitroaromatic explosive compounds (PA, DNT) and few picograms in the case of a common dye molecule (MB). Typical enhancement factors achieved were estimated to be ∼10 4 , ∼10 5 , and ∼10 7 , respectively, for PA, DNT, and MB. The significance of the present work lies in exploring the performance of the prepared NPs being used as SERS substrates for explosives detection using a portable Raman instrument. Such capability enables one to carry the spectrometer to the point of interest in the field and evaluate any hazardous samples within a short period of time.

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

“…The high‐intensity Raman modes observed at 446 and 1620 cm −1 can be ascribed to the skeletal deformation of C‐N‐C and C‐C ring stretching. The lower intensity modes noticed at 499, 769, and 1,393 cm −1 are assigned to the C‐N‐C skeletal deformation, C‐H in‐plane bending, and C‐N symmetric stretching, which are in accordance with the earlier published results . Figure b presents the recorded SERS spectra of MB (5nM) from the FeDNS1, FeDNS2, and FeDNS3 substrates, and the noticed spectral modes are slightly shifted, which can possibly be due to the orientation of probe molecule on the NSs.…”

“…The RSD values for the most intense peaks of R6G (771 and 1,506 cm −1 ) and MB (446 and 1,620 cm −1 ) are found to be <22% revealing the good reproducibility nature of the as‐fabricated SERS substrates even after usage for three times. The observed SERS peak intensities for R6G modes are found to be lower than the MB peak intensities in mixed spectra, which could be due the (a) interaction of analyte (mixture) with NSs (b) the excitation wavelength (785 nm in present case) used being nearer to the absorption maxima of MB (~650 nm) than for R6G (~530 nm) (c) Raman cross‐section of analyte molecules at used excitation source (785 nm in the present study). To comprehend the complete picture of SERS intensity variations for the mixed analyte, one has to perform the SERS measurements with different Raman excitation sources.…”

Tunable Silver Nanoparticle Arrays by Hot Embossing and Sputter Deposition for Surface-Enhanced Raman Scattering

“…relative standard deviation (RSD) of intensities of the 1503 cm −1 Raman characteristic peak was calculated to be 7.28%, which is relatively low compared to other studies [25][26][27], indicating good uniformity and reproducibility of the fabricated SERS substrates. Internsity (a.u.…”

“…The SERS intensities of the Raman characteristic peak of the 1503 cm −1 band from these locations are further displayed in Figure 10b. The relative standard deviation (RSD) of intensities of the 1503 cm −1 Raman characteristic peak was calculated to be 7.28%, which is relatively low compared to other studies [25][26][27], indicating good uniformity and reproducibility of the fabricated SERS substrates. characteristic peak of the 1503 cm band from these locations are further displayed in Figure 10b.…”