What is it about?
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.
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Why is it important?
Explosives detection at low concentrations is very important for security applications. here we demonstrate a simple procedure for preparing paper-based SERS targets (using Ag and Au nanoparticles) . We also demonstrate detection of multiple explosives using these targets.
Perspectives
We have successfully fabricated ecofriendly SERS substrate by using low-cost FP as a base and is embedded with NPs that were also fabricated by a green technique LAL. The common FP with aggregated Ag/Au NPs provided a simple and robust approach for SERS substrate preparation. Specifically, spherical Ag and Au NPs were loaded for an optimally aggregated configuration to yield maximum signal enhancements in the SERS measurements. Our results from detailed experiments presented here indicate that the Ag/Au NPs with 50 mM NaCl concentration is helpful for optimal SERS performance. From the result obtained, we conclude the paper-based Ag substrate performance better than paper-based Au substrate. The optimized active SERS paper substrate is helpful for the detection of four adsorbed molecules (MB-5 nM, PA-5 μM, DNT-1 μM, and NTO-10 μM) with high specificity, sensitivity, and reproducibility. These concentrations in terms of mass represent 31.98 pg, 11.45 ng, 1.82 ng, and 13.06 ng, respectively. Overall, we report here a simple, inexpensive technique for creating plasmonic substrates that are readily integrated with a portable spectrometer for rapid SERS analysis. It offers to decrease the cost of analysis using paper-based SERS targets and utilizing a portable Raman instrument, which is portable to the point of diagnostics of interest. Furthermore, the NPs produced by laser ablation are proven to be stable for long periods of time.44 However, the stability of these NPs when loaded in the FP is being investigated thoroughly. We strongly believe that following further optimization studies, the combination of low-cost and high-performance paper SERS devices will be an ideal platform to enter on-site analysis, beyond the research laboratories, for practical applications related to explosives detection.
Professor Venugopal Rao Soma
University of Hyderabad
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This page is a summary of: Ag/Au Nanoparticle-Loaded Paper-Based Versatile Surface-Enhanced Raman Spectroscopy Substrates for Multiple Explosives Detection, ACS Omega, July 2018, American Chemical Society (ACS),
DOI: 10.1021/acsomega.8b01318.
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