info:eu-repo/semantics/doctoralThesis
SURFACE ENHANCED RAMAN SUBSTRATE DESIGN: PROBE ON ORGANIC DYES AND PESTICIDES
Autor
Monica-Monserrat Martinez-Garcia
Institución
Resumen
"The aim of this work is the design, development and preparation of an efficient SERS substrate for the detection at low concentrations of dyes and pesticides. Concave gold nanocubes (CGNC) were synthesized by chemical reduction method, and were characterized by UV-Vis spectroscopy and by scanning electron microscopy (SEM), to ensure the proper morphology and size. An aluminum alloy (Al-6063 ) base was used for the nanoparticle deposit, since it does nor present Raman signal that could opaque the response signal of the analyte of probe. The surface of the slides was modified, first by mechanical treatment and then, were subjected to an electropolish process. Later were functionalized with silane molecules. The surface substrates was characterized by atomic force microscopy (AFM) and by Xray diffraction (XRD), to confirm the presence of pseudoboehmite in the surface. In order to select the size of nanocube that showed the best Raman signal improvement, solutions of nanoparticles of different sizes (36 − 85nm) were synthesized and deposited by drop casting over the Al-slides. The 4-Aminothiophenol molecule was used as analyte of probe at a concentration of 1.00 × 10−6M. The size that exhibited best performance was of 55nm, and was used in probes with Rhodamine 6G (Rh6G), Rose Bengal (RB) and Crystal Violet (CV) at low concentrations (2.22 × 10−13, 1.00 × 10−12, 1.00 × 10−10M respectively). The probes with Rh6G at a concentration of 2.22×10−13M were employed to calculate the enhancement factor, giving an estimate value of ∼ 107. Further, the SERS substrate with the same characteristics was used in detection of thiram pesticide at levels close to those dictated by the FDA (7ppm). The probes showed that the designed substrate is capable of detect the pesticide alone and in a mixture with tomato pulp, even at concentrations of 10µM."
Materias
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