Synthesis of dopamine functionalized silver nanoparticles together with possible interactions between silver and dopamine having different oxidation forms

Kanbertay, Elif
Dopamine is a neurotransmitter found in central nerve system which has a vital role for human health. Dopamine oxidation in body is an important issue since it may form reactive metabolites which can be toxic to the cell. Surface-enhanced Raman scattering (SERS) is currently recognized as one of the most sensitive spectroscopic tools, which can be exploited for ultrasensitive chemical and biological detection, addition to providing structural information on the systems of interest. SERS of dopamine displays three strong bands at 1269, 1331 and 1479 cm-1. These bands are the signature of dopamine molecule. The most intense band at 1479 cm-1 is contributed mainly from stretching of the carbon-carbon bond to which the oxygens are attached. A bidentate silver-dopamine complex or in general bidentate metal-dopamine complex formation is required for the SERS detection of dopamine and other catecholamines. In other words, for acquiring the characteristic dopamine SERS signature, both of the catechol oxygens should take a part in the adsorption of dopamine to the silver metal surface which is used as a SERS substrate. Therefore, the reactivity of different oxidation forms of dopamine for the formation of bidentate silver-dopamine complex was investigated by obtaining their SERS spectra and following the characteristic C-C ring vibration at 1479 cm-1. Dopamine oxidation was carried out electrochemically, utilizing platinum and silver electrodes as working electrode. Oxidation products formed were identified with UV-vis Spectrometer. Also, silver metal ions were used to oxidize dopamine, leading to formation silver nanoparticles. Dopamine functionalized silver nanoparticles were characterized by Scanning Electron Microscope, Transmission Electron Microscope, UV-vis Spectrometer. Surface- enhanced Raman spectra of polydopamine on the surface of synthesized silver nanoparticles and the electrodeposited dopamine on the porous surface of silver electrode were also obtained.