What is it about?
Herein we demonstrate the synthesis of Ag–Cu alloy NPs through a consecutive two-step process; laser ablation followed by laser irradiation. Initially, pure Ag and Cu NPs were produced individually using the laser ablation in liquid technique (with 50 femtosecond pulses at 800 nm) which was followed by laser irradiation of the mixed Ag and Cu NPs in equal volume. These Ag, Cu, and Ag– Cu NPs were characterised by UV-visible absorption, HRTEM and XRD techniques. The alloy formation was confirmed by the presence of a single surface plasmon resonance peak in absorption spectra and elemental mapping using FESEM techniques. Furthermore, the results from surface enhanced Raman scattering (SERS) studies performed for the methylene blue (MB) molecule suggested that Ag–Cu alloy NPs demonstrate a higher enhancement factor (EF) compared to pure Ag/Cu NPs. Additionally, SERS studies of Ag–Cu alloy NPs were implemented for the detection of explosive molecules such as picric acid (PA – 5 mM), ammonium nitrate (AN – 5 mM) and the dye molecule methylene blue (MB – 5 nM). These alloy NPs exhibited superiority in the detection of various analyte molecules with good reproducibility and high sensitivity with EFs in the range of 10^4 to 10^7.
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Why is it important?
Explosives sensing is vital for various security applications and simple/sensitive methods are the need of the hour.
Perspectives
The following are the conclusions from the present detailed study: Ag–Cu alloy NPs were fabricated using two consecutive steps of laser ablation and irradiation. The observed the single SPR peak from the UV-visible absorption spectra of Ag–Cu alloy NPs lies in between pure NPs, indicates the formation of alloy NPs. XRD, TEM and FESEM-EDX mapping analysis revealed that the alloy NPs are composed of both Ag and Cu atoms with composition of 54% and 46%, respectively, obtained from the EDX data. The SERS performance of these NPs was investigated for a dye molecule of MB and we conclude that the composite NPs exhibit superior SERS signals compared to pure NPs (Ag or Cu). Ag–Cu alloy NPs also served as active SERS substrates towards quantitative detection of common explosives such as picric acid and ammonium nitrate at low concentrations. These NPs as SERS substrates demonstrated greater reproducibility with reasonable RSD values.
Professor Venugopal Rao Soma
University of Hyderabad
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This page is a summary of: Explosives sensing using Ag–Cu alloy nanoparticles synthesized by femtosecond laser ablation and irradiation, RSC Advances, January 2019, Royal Society of Chemistry,
DOI: 10.1039/c8ra08462a.
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