Novel core etching technique on synthesized gold nanoparticles for colorimetric detection of dopamine biosample

This study develops a novel and high performance colorimetric probe for dopamine (DA) detection. Aqueous-phase gold nanoparticles (AuNPs) extracted with 4-(dimethylamino) pyridine (DMAP) from toluene solvent is used as the reaction probes. The conjugated AuNPs of the diameter around 13 nm disperse into the size of 2-5 nm while adding dopamine (DA), resulting in the color change of the AuNPs solution from red to green. Therefore, the extracted AuNP solution can be a good indicator for detecting DA biosample. Transmission electron microscope (TEM) observations and dynamic light scattering (DLS) tests show that the AuNPs turn into smaller size right after adding DA. Results confirm that the DMAP capped AuNPs are etched by the DA molecules due to the stronger affinity between DA and AuNPs and thus cause a blue shift in the absorption spectrum. The concentration of dopamine is quantitatively monitoring using an UV-vis spectrometer with a limit of detection (LOD) of lower than 5 nM. The developed AuNPs etching protocol for dopamine detection provides a novel and versatile approach for rapid biosensing applications.