Direct Synthesis and Accessibility of Amine-Functionalized Mesoporous Silica Templated Using Fluorinated Surfactants

Design of Nanostraws in Amine-Functionalized MCM-41 for Improved Adsorption Capacity in Carbon Capture

Polymeric amine encapsulation in high surface area MCM-41 particles for CO2 capture is well established but has the drawback of leaching out the water-soluble polymer upon exposure to aqueous environments. Alternatively, chemical (covalent) grafting amine functional groups from an alkoxysilane such as 3-aminopropyltriethoxysilane (APTES) on MCM-41 offer better stability against this drawback. However, the diffusional restriction exhibited by the narrow uniform MCM-41 pores (2-4 nm) may impede amine functionalization of the available silanol groups within the inner mesoporous core. This leads to incomplete amine functionalization and could reduce the CO2 adsorption capacity in such materials. Our concept to improve access to the MCM-41 interior is based on the incorporation of nanostraws with larger inner diameter (15-30 nm) to create a hierarchical porosity and enhance the molecular transport of APTES. Halloysite nanotubes (HNT) are used as tubular straws that are integrated into the MCM-41 matrix using an aerosol-assisted synthesis method. Characterization results show that the intrinsic structure of MCM-41 remains unaltered after the incorporation of the nanostraws and amine functionalization. At an optimal APTES loading of 0.5 g (X = 2.0), the amine-functionalized composite of MCM-41 with straws (APTES/M40H) has a 20% higher adsorption capacity than the amine-modified MCM-41 (APTES/MCM-41) adsorbent. Furthermore, the CO2 adsorption capacity APTES/M40H doubles that of APTES/MCM-41 when normalized based on the composition of MCM-41 in the composite particle with straws. The facile integration of nanostraws in MCM-41 leading to hierarchical porosities could be effective toward the mitigation of diffusional restriction in porous materials with potential for other catalytic and adsorption technologies.

A fluorous biphase drug delivery system triggered by low frequency ultrasound: controlled release from perfluorous discoidal porous silicon particles

Conventional drug delivery systems face unsatisfactory loading efficiency, poor biological bypass, and uncontrollable release, which are great barriers for improving the treatment of many diseases. Herein, a proof-of-concept of a fluorous biphase drug delivery system (FB-DDS) trigged by low frequency ultrasound (LFUS) is proposed for the first time, where promoted incorporation and stabilization of therapeutic agents in nanocarriers was achieved through fluorine-fluorine interactions, and the encapsulated drugs were controllably released by external sources, resulting in minimized nonspecific toxicity and enhanced therapeutic efficacy. The FB-DDS was constructed from monodisperse, discoidal porous silicon particles (PSP) and was functionalized with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS17) for loading perfluoropentane (PFP) and fluorinated drugs through fluorine-fluorine interactions. This delivery system was demonstrated by utilizing model compounds including a fluorous-tagged fluorescein and a fluorine containing antibiotic ciprofloxacin. Loading of the model molecules into fluorocarbon-coated carriers was facilitated by fluorous interactions, whereas ejection of the model molecules was promoted by applying LFUS to rapidly evaporate PFP. In the in vitro test, these carriers loaded with fluorine containing ciprofloxacin exhibited excellent antimicrobial activity against Pseudomonas aeruginosa biofilm formation. Overall, this innovative stimulus-responsive fluorous biphase drug delivery system will be a promising candidate for practical applications as well as encouraging further investigation of drug delivery and controlled release strategies.