Versatile gold based SERS substrates fabricated by ultrafast laser ablation for sensing picric acid and ammonium nitrate

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

“…Figure 6C shows the SERS spectra of MB (5 nM) with observed modes at 449, 776, 947, 1,175, 1,396, and 1,621 cm −1 are in good agreement with the earlier works [43]. The major MB peaks were located at 449, 1,621 cm −1 were assigned to skeletal deformation of C-N-C, Ring stretching of C-C, respectively [44] and the other peaks and their assignments were reported in earlier literature [13,45]. A strong peak at 520 cm −1 observed is from the silicon substrate with NPs (a break in spectra shown in Figure 6C) and also a broad flat edged peak between 900 and 1,000 cm −1 corresponds to the 2nd order Si Raman band.…”

“…Chen et al detected ammonium nitrate (AN) and RDX with EF of ∼7.0 × 10 4 using a monolayer of ordered Au NPs on Si substrates [23]. Our group has recently demonstrated the detection of several explosives such as picric acid (5 µM), AN (50 µM) using gold nanoparticles and nanostructures [13], ammonium perchlorate (10 µM) using Ag decorated Silicon nanowires [24], FOX-7 (5 µM) and 1NPZ (20 nM) [25], ANTA (1 µM) and TNT with E.F.'s >10 5 [26] using femtosecond laser fabricated NPs/NSs. Furthermore, we have also reported the detection of 2, 4-Dinitrotoluene using Ag-Au nanostructures achieved using femtosecond laser ablation [13].…”

“…In case of short pulses (typically ≤ few tens of ps) the pulse duration is much shorter than the electron-phonon interaction time which offers faster cooling of ablated species and reduce the irregularity in the particle size with improved stability of the NPs when compared to that obtained with longer pulses (ns) [12]. Typically, with ns ablation one can achieve NPs only while with fs ablation one can achieve both NPs and nanostructures (NSs) in a single experiment [13]. Kabashin et al reported the formation of gold NPs (3-10 nm) at a lower fluence which could be due to the thermal-free mechanism offered by fs pulses [14].…”

“…Hamad et al reported the ablation of Cu target in different organic liquids resulted in various products of Cu NPs in acetone, CuCl NPs in DCM, CuO NPs in ACN and CuCl 2 NPs in chloroform using ultrashort pulses [16]. Gold NPs with different sizes of ∼13.6, ∼7.6, ∼6.5, and ∼6.2 nm were achieved for input energies of ∼200, ∼300, ∼400, and ∼500 µJ using fs laser ablation [13]. Semaltianos et al synthesized nanomaterials of II-VI semiconductors (CdSe, CdTe, ZnTe) by ablating the targets in different solvents and the nanoparticles obtained were in the range of ∼5-6 nm [17].…”

“…Our group has recently demonstrated the detection of several explosives such as picric acid (5 µM), AN (50 µM) using gold nanoparticles and nanostructures [13], ammonium perchlorate (10 µM) using Ag decorated Silicon nanowires [24], FOX-7 (5 µM) and 1NPZ (20 nM) [25], ANTA (1 µM) and TNT with E.F.'s >10 5 [26] using femtosecond laser fabricated NPs/NSs. Furthermore, we have also reported the detection of 2, 4-Dinitrotoluene using Ag-Au nanostructures achieved using femtosecond laser ablation [13]. Recently, composite nanoparticles have attracted much attention by physicists, chemists and material scientists due to their higher catalytic, electronic, optical, physicochemical properties and multiple functionalities [2,[27][28][29][30][31][32][33][34].…”