Amine Modification of Thermally Carbonized Porous Silicon with Silane Coupling Chemistry

Thermally carbonized porous silicon (TCPSi) microparticles were chemically modified with organofunctional alkoxysilane molecules using a silanization process. Before the silane coupling, the TCPSi surface was activated by immersion in hydrofluoric acid (HF). Instead of regeneration of the silicon hydride species, the HF immersion of silicon carbide structure forms a silanol termination (Si–OH) on the surface required for silanization. Subsequent functionalization with 3-aminopropyltriethoxysilane provides the surface with an amine (−NH₂) termination, while the SiC-type layer significantly stabilizes the functionalized structure both mechanically and chemically. The presence of terminal amine groups was verified with FTIR, XPS, CHN analysis, and electrophoretic mobility measurements. The overall effects of the silanization to the morphological properties of the initial TCPSi were analyzed and they were found to be very limited, making the treatment effects highly predictable. The maximum obtained number of amine groups on the surface was calculated to be 1.6 groups/nm², corresponding to 79% surface coverage. The availability of the amine groups for further biofunctionalization was confirmed by successful biotinylation. The isoelectric point (IEP) of amine-terminated TCPSi was measured to be at pH 7.7, as opposed to pH 2.6 for untreated TCPSi. The effects of the surface amine termination on the cell viability of Caco-2 and HT-29 cells and on the in vitro fenofibrate release profiles were also assessed. The results indicated that the surface modification did not alter the loading of the drug inside the pores and also retained the beneficial enhanced dissolution characteristics similar to TCPSi. Cellular viability studies also showed that the surface modification had only a limited effect on the biocompatibility of the PSi

Charge and Nuclear Dynamics Induced by Deep Inner-Shell Multiphoton Ionization of CH₃I Molecules by Intense X‑ray Free-Electron Laser Pulses

In recent years, free-electron lasers operating in the true X-ray regime have opened up access to the femtosecond-scale dynamics induced by deep inner-shell ionization. We have investigated charge creation and transfer dynamics in the context of molecular Coulomb explosion of a single molecule, exposed to sequential deep inner-shell ionization within an ultrashort (10 fs) X-ray pulse. The target molecule was CH₃I, methane sensitized to X-rays by halogenization with a heavy element, iodine. Time-of-flight ion spectroscopy and coincident ion analysis was employed to investigate, via the properties of the atomic fragments, single-molecule charge states of up to +22. Experimental findings have been compared with a parametric model of simultaneous Coulomb explosion and charge transfer in the molecule. The study demonstrates that including realistic charge dynamics is imperative when molecular Coulomb explosion experiments using short-pulse facilities are performed