Aptms

To prepare plasmonic-fluor-800CW, AuNR (wavelength around 760) was employed as the nanoantenna. 1 μl MPTMS (Sigma Aldrich, 175617) was added to 1 ml AuNR (extinction ~2) and the mixture was shaken on rocking bed for 1 hour. Subsequently, MPTMS-modified AuNR was collected by centrifugation at 6000 rpm for 10 mins and was further mixed with 2 μl APTMS (Sigma Aldrich, 281778) and 2 μl TMPS (Sigma Aldrich, 662275) to form the polymer spacer layer. Finally, AuNR/polymer solution was collected by twice centrifugation at 6000 rpm for 10 minutes to remove the free monomer and concentrated into a final volume of 10 μl.
Next, BSA-biotin-800CW conjugate was coated around AuNR/polymer modified from a previously reported method.^{48 (link)} Specifically, pH of 100 μl 4 mg/ml BSA-biotin-800CW was first lower by adding 1 μl 20 mg/ml citric acid (Alfa Aesar, 36664). Subsequently, concentrated AuNR/polymer solution was added into BSA-biotin-800CW solution and sonicated for 20 minutes under dark condition. The coated nanostructures were then collected by centrifugation at 5000 rpm for 5 minutes and subsequently incubated with 0.5 ml 0.4 mg/ml BSA-biotin-800CW (pH=10) for 3 days in 4°C. Finally, the nanostructures were washed four times using alkaline nanopure water (pH=10) by centrifugation at 6000 rpm and re-dispersed in 1% BSA 1X PBS solution for further use.