Abstract
In this research, sensing performance of mono and bimetallic nanophotonics SERS sensors of gold-silver nano-columns for the detection of chlorpyrifos was investigated. For optimum substrates for Gold-silver/nano-column surface-enhanced, Raman scattering (SERS) was achieved with the silicon substrate. By combining the Ag SERS activity with the Au chemical stability and nano-columns Si large field enhancement, the Au-Ag/nano-columns Si substrate revealed perfect reproducibility, homogeneity, sensitivity in addition to chemical stability. The sensors were tested by Atomic force microscope (AFM), field emission scanning electron microscope (FESEM), energy-dispersive X-ray analysis (EDS), and X-ray diffraction (XRD). Findings presented in this research indicated modified distributions and sizes of formed alloy nanoparticles, and the hot spots junctions within the nanophotonics layer after changing the nanoparticles types. The SERS sensors performance displayed an excellent recognition of ultra-low concentrations of chlorpyrifos solutions with an exponential relationship with the Raman signal. The highest enhancement factor (Ef=1.56×106) and minimum limit of detection 0.069 mg/Kg were obtained with Au-Ag sensors.
Highlights
Surface Plasmons (SPs) is a physico-chemical phenomena where collective excitation of free conductive electrons at the metal-dielectric interfaces which induced by electromagnetic field [1]
The AuNPs, AgNPs and Au-Ag NPs profiles show a large accumulation of particles that increase the surface roughness and reduce the depth of surface about 29, 20nm, and 18 nm for gold, silver, and gold-silver respectively
The surface roughness was increased to (4nm), (6.7), and (8.8 nm) for gold, silver, and Au-Ag bimetallic nanoparticles correspondingly. These surface topographical properties variations are due to high-density nucleation sites and high-density metallic ions; resulted from the reduction process
Summary
Surface Plasmons (SPs) is a physico-chemical phenomena where collective excitation of free conductive electrons at the metal-dielectric interfaces which induced by electromagnetic field [1]. The change in metal composition retrofits another dimension in tailoring the BMNPs features alongside the shape and usual size manipulation [7] Because of their extremely very small size with respectively large surface-to-volume ratio, the nano-sized materials serve as an ideal candidate for different applications. Since silver metal was demonstrated for inducing strong enhancement effects, these metal-based nanomaterial’s have been used in SERS applications [11]; it was reported that silver nanostructures demonstrate a strong tendency to grow and/or reshape upon prolonged irradiation [12], in addition to its easy oxidation at room temperature [13] For these reasons, the attention was focused on hybrid nanomaterial in recent years, where the features of two elements or more have been combined in a single platform [12]. The process of ion reduction of Au and Ag ions was employed to create the mono and bimetallic nanoparticles
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