Hollow Periodic Mesoporous Organosilica Research Articles

A controllable asymmetrical/symmetrical coating strategy for architectural mesoporous organosilica nanostructures

We describe a facile and controllable asymmetrical/symmetrical coating strategy for the preparation of various novel periodic mesoporous organosilica (PMO) nanostructures, including Au&PMO Janus, Au@PMO yolk-shell and Au@PMO/mSiO2 yolk-double shell nanoparticles, by using Au@SiO2 nanoparticles as seeds. During this process, ammonia first functions as a basic catalyst facilitating the hydrolyzation and condensation of the organosilica precursor, and additionally as an etching agent selectively in situ dissolving the SiO2 shells of Au@SiO2 nanoparticles to form these unique nanostructures. All these three types of nanoparticles have high surface areas, large pore volumes and tailorable cavity structures. Both the Au&PMO and Au@PMO nanoparticles exhibit excellent catalytic activity for the decomposition of H2O2 and the reduction of 4-nitrophenol. Based on these unique structural merits and organic-inorganic hybrid components, the fabricated Janus and hollow PMO nanoparticles show much improved hemocompatibility, which could be further applied in nano-biomedicines without the need for surface modification.

Colloidal HPMO Nanoparticles: Silica‐Etching Chemistry Tailoring, Topological Transformation, and Nano‐Biomedical Applications

Hybridization produces the better: Colloidal hollow periodic mesoporous organosilica nanoparticles (HPMO NPs) with tunable compositions and highly hybridized nanostructures are successfully synthesized by a simple, easily scale-up but versatile silica-etching chemistry (alkaline or HF etching) for their applications in nano-fabrication and nano-medicine.

Heterogeneous Organocatalysis at Work: Functionalization of Hollow Periodic Mesoporous Organosilica Spheres with MacMillan Catalyst

We report a new method for the synthesis of hollow-structured phenylene-bridged periodic mesoporous organosilica (PMO) spheres with a uniform particle size of 100-200 nm using α-Fe(2)O(3) as a hard template. Based on this method, the hollow-structured phenylene PMO could be easily functionalized with MacMillan catalyst (H-PhPMO-Mac) by a co-condensation process and a "click chemistry" post-modification. The synthesized H-PhPMO-Mac catalyst has been found to exhibit high catalytic activity (98% yield, 81% enantiomeric excess (ee) for endo and 81% ee for exo) in asymmetric Diels-Alder reactions with water as solvent. The catalyst could be reused for at least seven runs without a significant loss of catalytic activity. Our results have also indicated that hollow-structured PMO spheres exhibit higher catalytic efficiency than solid (non-hollow) PMO spheres, and that catalysts prepared by the co-condensation process and "click chemistry" post-modification exhibit higher catalytic efficiency than those prepared by a grafting method.

Synthesis of magnetic hollow periodic mesoporous organosilica with enhanced cellulose tissue penetration behaviour

Commercially available barium ferrite BaFe12O19 (BaFeO) nanoparticles with a size of ∼100 nm have been successfully encapsulated inside the hollow periodic mesoporous organosilica (HPMO) host material, through a 2-step (coating and encapsulation) approach. The resultant magnetic HPMO (MHPMO) nanoparticles possess a relatively high saturated magnetization (25 emu g−1) and a high enzyme loading capacity (1.32 mg/mg). It is further demonstrated that MHPMO materials exhibited enhanced cellulose tissue penetration behaviour under applied external magnetic field, promising for delivery applications to plant cells.

Periodic mesoporous silica and organosilica with controlled morphologies as carriers for drug release

In this paper, we report the effects of morphology, wall composition of mesoporous materials and different buffer solutions on drug delivery profiles. Hollow spheres of periodic mesoporous organosilica (PMO) were prepared and used as drug carriers which exhibited higher loading capacity and slower release rate compared to the conventional periodic mesoporous silica (PMS) spheres and solid spheres of PMO. This hollow PMO showed promising properties as a reservoir to encapsulate and store larger quantities of guest molecules within its “empty” core. Moreover, its organic reactive sites allowed stronger interactions to the hydrophobic guest molecules, in contrast to inorganic wall possessed by PMS materials. Antibiotic tetracycline was used as a model drug to study the effect of framework difference between PMO and PMS materials on the loading and release processes. Two kinds of release medium, simulated body fluid (SBF) solution (pH 7.4) and phosphate buffer (PB) solution (pH 1.5) were used in this study, which revealed very different release profiles. A slower delivery rate was observed in SBF solution, attributed to the different ionic interactions between the guest molecule and the host material in the two different pH solutions. Overall, hollow PMO shows the lowest release rate and the highest loading amount compared to the other two materials studied herein. The kinetic study reveals that drug release from host material follows the second order kinetic model better than the first order mass transfer model.

Mesoporous Silica Templated Biolabels with Releasable Fluorophores for Immunoassays

A novel class of fluorescent immuno-biolabeling systems with extremely high F/P ratio (approximately 1000-6000) were prepared by combining the template method and layer-by-layer (LbL) technique. Labels were constructed by loading organic dye fluorescein diacetate (FDA) molecules onto hollow periodic mesoporous organosilica (H-PMO) particles followed by ployelectrolyte encapsulation and antibody attachment. The labeling systems were stimuli-responsive to the addition of concentrated NaOH with the loaded dye molecules being released and detected in a well-controlled manner. When applied in sandwich immunoassays, results indicated that the biolabels were immuno-active and generated an optimal signal that was approximately 50 times higher than the conventional dye labelled antibody system.