The purpose of functionalizing DFNS with PDA is to enable adsorption of FAM-ssDNA to achieve effective quenching. The thickness of the PDA coating can be controlled by adjusting the polymerization time and reaction conditions . In this study, the PDA functionalization on the surface of DFNS was achieved through self-polymerization of dopamine at alkaline pH (∼8.5). We measured the quenching efficiency of DFNS-4@DA obtained by using different polymerization times. Fig. shows that after 2 hours of polymerization, the obtained DFNS-4@DA achieved a quenching efficiency (QE) of more than 95%. Increasing the polymerization time after 2 hours did not significantly affect the QE.