SERS Study of Alizarin Red Dye on Colloidal Silver Nanoparticles
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1241-XX06-08
SERS Study of Alizarin Red Dye on Colloidal Silver Nanoparticles Raj K. Swarnkar1, Subhash C. Singh1, and Ram Gopal1 Laser Spectroscopy & Nanomaterials Lab, Physics Department, University of Allahabad, Allahabad-211002, INDIA. [email protected], [email protected] 1
ABSTRACT:
The present paper deals with surface enhanced Raman scattering (SERS) study of an organic dye Alizarin Red on colloidal silver nanoparticles. The colloidal solution of nanoparticles is synthesized by pulsed laser ablation of silver rod in pure deionized water using focused out put of 1064nm wavelength of Nd:YAG laser having 35mJ/ pulse energy. Sodium chloride is used as aggregating agents. It is observed that SERS enhancement factor varies strongly depending on concentration of used aggregating agent (especially on the concentration of Cl- ions). These changes in SERS efficiency of colloid are reflected through changes on the absorption spectra. The possible mechanism of SERS is also discussed. INTRODUCTION: Surface enhanced Raman scattering (SERS) appears as a great revolution during the last three decades in the field of vibrational spectroscopy. SERS differs in a number of ways from ordinary Raman spectroscopy of the molecules and solids. SERS is based on the marked enhancement of Raman signals of certain molecules when they are placed in the proximity of certain nanostructured metallic surfaces. SERS has been observed for a very large number of molecules adsorbed on the surfaces of the relatively few metals in a variety of morphologies and physical environments. The successful application of metal nanoparticles in SERS strongly depends on the metal characteristics, in terms of morphologies (shape, size and aggregation state) and the metal nature of the nanostructured metals employed as substrates. Colloidal nanoscale particles are found as a good substrate for SERS [1]. Amongst the noble metals silver is found to be the most universal substrate due to its broad plasmon resonance in the visible – near infra red region and high stability. Additionally, a key factor in SERS experiments is the metal-solution interface. This factor depends indeed on the method of preparation. Laser ablation in liquid medium is an exciting technique to produce colloidal nanoparticles having chemical contamination free surfaces [2]. There are several advantages of this technique including inexpensive equipment for controlling the ablation atmosphere, simplicity of the procedure and the minimum amount of chemical species required for synthesis compared to the other conventional chemical process. The size of the nanoparticles can be controlled by varying laser parameters (e.g. laser wavelength, laser irradiance etc.) and liquid medium (e.g. nature of surfactant, concentration, dipole moment etc.). In the present work we have studied the SERS of an Anthraquinone dye, Alizarin Red, as a probe with colloidal silver nanoparticles as substrate. Alizarin Red is amongst most important and oldest organic dyestuffs used in painting and textile
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