PubMed Health⌕ Search

Biomedical subjects

Douglas A Loy

Publications and source records attributed to Douglas A Loy.

5 recordsLinked to original sources
PubMed2006

Photodeformable spherical hybrid nanoparticles.

We report the first synthesis of spherical nanoparticles of a bridged polysilsesquioxane. The hard, brittle nanoparticles are prepared by a simple sol-gel polymerization without surfactants or templates. Particle size ranges from 50 to 100 nm. The organic component of these hybrid nanoparticles is composed of a photolabile coumarin dimer. Irradiation with UV light dissociates the photodimer resulting in rupture of the cross-links and subsequent deformation and eventual "melting" of the nanoparticles.

Journal Article↗
PubMed2005

Metathesis depolymerization for removable surfactant templates.

Current methodologies for the production of meso- and nanoporous materials include the use of a surfactant to produce a self-assembled template around which the material is formed. However, post-production surfactant removal often requires centrifugation, calcination, and/or solvent washing which can damage the initially formed material architecture(s). Surfactants that can be disassembled into easily removable fragments following material preparation would minimize processing damage to the material structure, facilitating formation of templated hybrid architectures. Herein, we describe the design and synthesis of novel cationic and anionic surfactants with regularly spaced unsaturation in their hydrophobic hydrocarbon tails and the first application of ring closing metathesis depolymerization to surfactant degradation resulting in the mild, facile decomposition of these new compounds to produce relatively volatile nonsurface active remnants.

Journal Article↗
PubMed2005

Thermally cleavable surfactants based on furan-maleimide Diels-Alder adducts.

Two new surfactant molecules are reported that contain thermally labile Diels-Alder adducts connecting the hydrophilic and hydrophobic sections of each molecule. The two surfactants possess identical hydrophobic dodecyl tail segments but have phenol and carboxylic acid hydrophilic headgroups, respectively. Deprotonation with potassium hydroxide affords the formation of water-soluble surfactants. Room temperature aqueous solutions of both surfactants exhibit classical surface-active agent behavior similar to common analagous alkylaryl surfactant molecules. Critical micelle concentrations have been determined for each surfactant through dynamic surface tension and dye solubilization techniques. Small-angle neutron scattering measurements of the aqueous surfactant solutions indicate the presence of spherical micelles with radii of 16.5 angstroms for the carboxylate and 18.8 angstroms for the phenolate. When these surfactants are exposed to elevated temperatures (>50 degrees C), the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments. Aqueous solutions of each surfactant subsequently exhibit a loss of all surface-active behavior and the micellar aggregates are no longer detectable.

Journal Article↗
PubMed2003

A parallel colorimetric method for the rapid discovery and optimization of heterogeneous hydrodesulfurization catalysts.

A spectrophotometric based, parallel approach to screen heterogeneous catalysts for hydrodesulfurization has been developed. The method utilizes optical changes resulting from the hydrodesulfurization of 1,1'-binaphthothiophene to 1,1'-binaphthyl to determine catalyst activity. Hydrodesulfurization of 1,1'-binaphthothiophene to 1,1'-binaphthyl results in a loss of conjugation in the binaphthyl ring system. This results in a blue shift of more than 60 nm in the UV-vis spectrum. Since only small amounts of the HDS catalyst and 1,1'-binaphthothiophene are required, a large number of catalysts may be screened simultaneously. The synthesis of the 1,1'-binaphthothiophene and conditions for HDS catalyst screening are described.

Journal Article↗