2.4. Synthesis of HSSNs. Monodispersed HSSNs were prepared
using EtOH as the solvent. A total of 0.50 g of PVP was added to
10.00 mL of absolute EtOH, and the mixture was sonicated until all of
the PVP was dissolved. A 0.40 mL aliquot of H2O and 0.10 mL of 0.17
M Na3Ct were added into the PVP−EtOH mixture, followed by the
addition of 0.40 mL of NH4OH and 0.15 mL of TEOS. The mixture
was shaken by hand gently and then left to rest for overnight reaction
at room temperature. HSSNs were collected by centrifuging at 3000
rpm for 30 min. The supernatant was removed, and the precipitates
were washed three times with EtOH for 20 min. The calcination
process at 500−600 °C for 4 h can remove PVP to obtain HSSNs.25
For the synthesis of dye-doped HSSNs, 0.40 mL of a 10.00 mM Rubpy
solution was added instead of 0.40 mL of H2O, and the reaction
proceeded in the dark. Rubpy-doped HSSNs were collected by
centrifuging at 3000 rpm for 30 min, and the precipitates were washed
three times by EtOH. After carefully removal of the supernatant, the
Rubpy-doped HSSNs were redispersed in 10 mL of H2O for
fluorescence intensity measurement. The fluorescence intensities of a
pure Rubpy aqueous solution (0.03 mM) and pure HSSNs (0.05 mg/
mL) were measured as controls. For the synthesis of polymyxin Bdoped
HSSNs, 0.40 mL of a 5.00 mg/mL polymyxin B solution was
added instead of 0.40 mL of H2O.