Silica Cross-linked Micelles Loading with Silicon Nanoparticles: Preparation and Characterization

A new family of luminescent and stable silicon-based nanoparticles (NPs), silica cross-linked pluronic F127 (PF127) micelles loaded with decyl capped silicon nanoparticles (decyl-SiNPs), were synthesized in aqueous media. The decyl-SiNPs were prepared by first liberating hydride terminated SiNPs (H-SiNPs) from a porous silicon matrix followed by their functionalization via hydrosilylation with 1-decene under photochemical activation. The silicon-based NPs exhibit bright photoluminescence (PL) with a quantum yield of ∼3.8% and peaking at ∼2.0 eV, which lies within the transmission window that is useful for biological imaging. They display a hydrodynamic size of ∼25 nm with exterior polyethylene oxide (PEO) blocks stretching out in aqueous media. Chloroform was found to quench the excitation at energy above 4.9 eV by shielding the incident light or relaxing the charge carriers, which highlights that caution against solvent interference should be taken when performing the studies on PL origin and luminescence efficiency of SiNPs. For PF127, the blocks of hydrophilic PEO participate in the PL quenching, while poly(propylene oxide) (PPO) does not. The colloidal solution displays excellent PL stability against salt (NaCl) and temperature but is susceptible to basic solution at pH above 9.