Daniela Rodica Radu

Organosulfonic acid-functionalized mesoporous silicas for the esterification of fatty acid

Abstract Organosulfonic acid-functionalized mesoporous silicas were synthesized in a one-step approach of co-condensing inorganic–organic reagents in the presence of different surfactant templates with in situ oxidation of the thiol groups to the sulfonic acid groups. The resulting materials were tested for their catalytic performance in the esterification of fatty acid with methanol to produce methyl esters. The performance of the functionalized mesoporous materials demonstrated a strong dependence on the median pore diameter of the catalyst as well as the acidic strength of the organosulfonic acid group. The activity of the organosulfonic acid-functionalized silicas in the esterification was compared to that of standard acidic resins. The results indicate the potential of rational catalysis design using organic–inorganic mesoporous materials.

Real-time imaging of tunable adenosine 5-triphosphate release from an MCM-41-type mesoporous silica nanosphere-based delivery system.

We studied a mesoporous silica nanosphere (MSN) material with tunable release capability for drug delivery applications. We employed luciferase chemiluminescence imaging to investigate the kinetics and mechanism of the adenosine 5-triphosphate (ATP) release with various disulfide-reducing agents as uncapping triggers. ATP molecules were encapsulated within the MSNs by immersing dry nanospheres in aqueous solutions of ATP followed by capping of the mesopores with chemically removable caps, such as cadmium sulfide (CdS) nanoparticles and poly(amido amine) dendrimers (PAMAM), via a disulfide linkage. By varying the chemical nature of the “cap” and “trigger” molecules in our MSN system, we discovered that the release profiles could indeed be regulated in a controllable fashion.

Fine-tuning the degree of organic functionalization of mesoporous silica nanosphere materials via an interfacially designed co-condensation method

A synthetic method that can fine tune the amount of chemically accessible organic functional groups on the pore surface of MCM-41 type mesoporous silica nanosphere (MSN) materials has been developed by electrostatically matching various anionic organoalkoxysilanes with the cationic cetyltrimethylammonium bromide micelles in a base-catalyzed condensation reaction of tetraethoxysilane.

Reversible binding and fluorescence energy transfer between surface-derivatized CdS nanoparticles and multi-functionalized fluorescent mesoporous silica nanospheres

Abstract A MCM-41 types of Mesoporous Silica Nanosphere material ( MSN ) covalently anchored with a fluorescent dye (Texas Red™) is synthesized. The Texas-Red-doped MSNs is also functionalized with a second organic group, i.e., mercaptopropyl or aminopropyl functionalities. These organic groups of the resulting bifunctional MSN s are utilized as reversible linkers to entrap two corresponding surface-derivatized cadmium sulfide ( CdS ) nanoparticles. The kinetics of encapsulation and release as well as the photophysical properties of the photoluminescent quantum dots and the MSN composites are investigated by examining the fluorescence resonance energy transfer between the two species. We demonstrated that the fluorescence energy transfer between CdS and Texas Red molecules can be “ switched off” by chemically cleaving the covalent linkage between the mesopore-entrapped CdS and the fluorescent MSN . Our results indicated that these MSN materials provided with proper pore-surface functional groups could serve as reversible hosts to entrap and release surface-derivatized cadmium sulfide nanoparticles.