Rapid and sensitive colorimetric determination of dopamine and serotonin in solution and polymer matrix with photochemically prepared and N-acetyl-L-cysteine functionalized gold nanoparticles

Here we report that the use of thioxanthone disulfide [TX-S-]2 photoinitiator as photo reducing agent for in-situ preparation of gold nanoparticles (AuNps) both in the presence and absence of N-acetyl cysteine (NAC) and these solutions were employed for colorimetric determination of dopamine (DA) and serotonin (SER) as very important two neurotransmitters for the human body at a micromolar level using solutions consist of AuNps. The UV-Vis spectroscopy technique was used for the determination of in-situ formed AuNps and the change of Surface Plasmon Resonance (SPR) band after each addition of DA and SER as a result of color changes. Dynamic Light Scattering (DLS) and Scanning Electron Microscope (SEM) analysis was used for the detailed characterization of AuNps. The method was linear in a concentration range between 7.45 and 24.4 µM. The limit of detection (LOD) and limit of quantification (LOQ) were found 8.4 and 28 µM, for DA and 5.41 and 18.04 µM for SER, respectively. Additionally, as a preliminary experiment, in-situ synthesis of AuNps was carried out in a polymer matrix with DA and SER and it was found that the sizes were in good agreement with previously prepared solutions. The color of the polymer matrix was turned from colorless to purple and then to dark purple even in 15 min irradiation times for both formulations.