Raman Sinyalinin Güçlendirilmesine Yönelik Nanoyapılı Sensör Yüzeyinin Hazırlanması

Abstract

Raman spectroscopy is a fast and highly sensitive analysis method which provides information about molecular structure. However, Raman scattering is an extremely weak process. Therefore, the Raman signal intensity should be increased. Within the thesis, metallic nanostructured substrates have been prepared to enhance Raman signal intensity. Simple and low cost solutions were taken into account in the material selection and development method. Anodic alumina with porous structure and large surface area has been developed as the base material by the anodization method. The anodic alumina layer with nanometer size pores was formed by applying voltage to the aluminum surface in oxalic acid solution. The change in parameters such as the anodizing time, the number of anodizing treatments have been effected pore diameter, pore density and thickness of layer. These results were determined by SEM analysis. Gold particles was deposited by different chemical methods on the porous structures. Alloy structures with flower-shaped, composed of tin, silver and gold, were developed on the surface by the electroless plating method and these structures were characterized by SEM and EDX analyzes. The anodic alumina surface was examined for its interaction with chloroauric acid (HAuCl4). Here, it can be said that the pitting corrosion mechanism is effective. The gold particles were deposited on the anodic alumina layer while aluminum acts as a reducing agent. Gold structures were observed as repeated clusters on the surface. Surface roughness was determined by AFM. Hydrophobicity of the surface was investigated by making contact angle measurements. It was observed with the SEM analysis that the change in the anodizing time affects the size and the area of the gold clusters deposited on the surface. In this context, surface optimization was performed by determining the most suitable experimental parameters for surface enhanced Raman spectroscopy (SERS) analysis. As another method, a colloidal gold solution was synthesized by chemical reduction method, the size and shape of the gold particles were determined by TEM images. The synthesized colloidal gold solution was dropped onto the surfaces and dried. In the SERS analysis on these surfaces, it was determined that gold nanoparticles show a higher Raman signal intensity in the presence of citrate ions. Whereas, Raman signal intensity have decreased when gold particles are washed away and citrate ions are removed. SERS analyzes performed for aqueous solutions of ammonium nitrate on anodic alumina surfaces coated with gold particles. Among the developed surfaces, the highest Raman signal intensity was observed in the anodic alumina surface prepared by immersing it in 1,25 mM HAuCl4 solution for one hour time. On this surface, SERS study was carried out to determine nitrate in drinking water and calibration graph was created. The R2 value was calculated as 0,992, the lowest detection limit being 1,06 ppm. The Raman signal enhancement factor was found to be 1,25 x104. It has been shown that the anodic alumina surface, which was deposited gold particles by the electroless plating method, can be a versatile substrate for SERS analysis.