Versatile Thiol- and Amino-Functionalized Silatranes for in-situ polymerization and Immobilization of Gold Nanoparticles

Background: Organosilanes have been massively implemented as building blocks in the fields of sol–gel material synthesis, surface functionalization, and nanotechnology. However, organosilane has been humbled by limitations, such as poor reproducibility, fast hydrolysis and heterogeneous molecular orientation. An emerging silatrane is gaining tremendous interest due to the unique tricyclic caged structure and transannular N→Si dative bond to provide chemical stability in aqueous solution and controllable deposition on surfaces. Methods: Aminopropyl silatrane (APS), Mercaptopropyl silatrane (MPS) and 3-Mercaptopropyl trimethoxysilane (MPTMS) were applied to modification of silicon oxide substrates to in-situ graft hydrophilic polymers and immobilize gold nanoparticles (AuNPs). Thin and uniform silatrane coatings have been proved by atomic force spectroscopy, ellipsometry and X-ray photoelectron spectroscopy. Significant Findings: Antifouling poly(ethylene glycol) methacrylate (PEGMA) was grafted separately on MPS and MPTMS via surface-initiated thiol-ene photopolymerization. We found that MPS-PEGMA films were 30% superior to MPTMS-PEGMA films in protein repellency. Moreover, APS and MPS were co-deposited to attract and conjugate gold nanoparticles. AuNPs cluster size on APS films was found to increase 3.43 times along with broader AuNPs absorbance peaks after acid treatment, whereas cluster size increased only 4% on mixed silatrane-modified films. These discoveries are pertinent to robust and versatile properties that silatrane offers.