Jeffrey D. Jordan

Portable, Low-Cost, Solid-State Luminescence-Based O2 Sensor

A novel sensor for quantifying molecular O2 based entirely on solid-state electronics is presented. The sensor is based on the luminescence quenching of tris(4,7-diphenyl-1, 10-phenanthroline)ruthenium(II) ([Ru(dpp)3]2+) by molecular O2. The sensor involves immobilizing the ruthenium complex within a porous sol-gel-processed glass film and casting this film directly onto the surface of a blue quantum-well light-emitting diode (LED). The ruthenium complex is excited by the LED, the [Ru(dpp)3]2+ emission is filtered from the excitation with a low-cost acrylic color filter, and the emission is detected with an inexpensive silicon photodiode. The sensor response to gaseous O2 and dissolved O2 in water is presented. The sensor exhibits fast response times and good reversibility, and detection limits are 0.5%, 0.02%, and 110 ppb, respectively, for O2 in the gaseous (linear Stern–Vobner and multi-site Stern–Volmer analysis) and aqueous phase. This sensor provides a cost-effective alternative to traditional electrochemical-based O2 sensing and also provides a platform for other optically based sensors.

Effects of Poly(ethylene glycol) Doping on the Behavior of Pyrene, Rhodamine 6G, and Acrylodan-Labeled Bovine Serum Albumin Sequestered within Tetramethylorthosilane-Derived Sol-Gel-Processed Composites

We investigate the effects of controlled poly(ethylene glycol) (PEG) doping on the behavior of pyrene, rhodamine 6G (R6G), and acrylodan-labeled bovine serum albumin (BSA-Ac) sequestered within tetramethylorthosilicate (TMOS)-derived sol-gel-processed materials. To probe the dipolarity of the local environment within the composite we performed static fluorescence measurements on pyrene as the composites aged. We found that small levels of PEG loading effected significant enhancements in the local dipolarity surrounding the average pyrene molecule. Time-resolved fluorescence anisotropy measurements were used to follow the rotational reorientation dynamics of R6G as the composites aged. As the PEG loading increased, the R6G reorientational mobility increased. Nitrogen adsorption techniques were used to quantify the effects of PEG doping level on the surface area and final xerogel pore features. A large reduction in surface area was observed with PEG doping, but no detectable change in pore size was noted. The effects of PEG doping on a biomolecule were probed by following the time-resolved fluorescence anisotropy decay of BSA-Ac. These results showed that PEG doping resulted in increased biomolecule dynamics relative to that found for a neat, undoped TMOS-derived composites. Together these results show that PEG doping can be used to tune the sol-gel-processed composite dipolarity, alter the mobility of dopants sequestered within the composite, control analyte acessibility to the sensing chemistry, and modulate the internal dynamics within a biodopant.

Aerosol-generated sol-gel-derived thin films as biosensing platforms

We have incorporated an antibody into a sol-gel-derived thin film composite and demonstrated that it retains affinity for its hapten. An inexpensive apparatus to produce and deposit, aerosol-generated sol-gel-derived thin films was also developed. The antibody antifluorescein (AF) was entrapped between two sol-gel thin films (0.62 ± 0.05 μm) in a sandwich architecture. The fluorescent hapten 5-(-and 6-)-carboxy-4′,5′-dimethylfluorescein (Me2F) was used to determine the accessibility and viability of the entrapped AF. Results demonstrate that a population of the entrapped antibodies recognizes and binds Me2F for up to 13 weeks when stored in pH 8 phosphate buffer at 4 °C. An intriguing result is that the response times of these AF-doped thin films actually improve as a function of storage time. We explain this observation in terms of decreased viability of AF molecules sequestered between the upper and lower films of the sandwich. Partial regeneration (40–50%) of the biosensor was obtained using a mild chaotropic reagent (NaCl) and the AF-doped films could be reset/regenerated up to six times.