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K D Legg

Publications and source records attributed to K D Legg.

5 recordsLinked to original sources
PubMed1994

Single fiber-optic pH sensor based on changes in reflection accompanying polymer swelling.

We have prepared fiber-optic pH sensors consisting of a small drop of aminated polystyrene on the tip of a single optical fiber with a core diameter of 100 microns. The sensor is prepared by dipcoating a partially polymerized solution and then completing the polymerization on the fiber. This is followed by amination with diethanolamine. The polymer formulation includes xylene/dodecane to introduce porosity and Kraton G1652, a styrene-ethylene, butylene-styrene, triblock copolymer as a toughening agent. The polymer swells as the amine groups are protonated. This is accompanied by an increase in clarity of the polymer and a decrease in the intensity of light reflected back into the optical fiber. Intensity decreases by over a factor of 2 as the pH is decreased from 8.0 to 6.5. The resulting sensor is small and mechanically stable with a response time of several minutes.

Biosensing Techniques↗
PubMed1982

Establishing the direct-potentiometric "normal" range for Na/K: residual liquid junction potential and activity coefficient effects.

The observed reference ranges for sodium and potassium as determined by direct potentiometry vary from instrument to instrument, depending on the composition of the calibration standards. To resolve the existing confusion as to which reference intervals are most appropriately considered "normal," we propose a straightforward convention (based on plasma-water concentration units) in which the difference between direct (undiluted sample) and indirect (diluted sample) methodologies is accounted for by the volume displacement effect of proteins, lipids, and other dissolved substances in a typical plasma sample. Thus, the proposed reference intervals for sodium and potassium are approximately 7% greater by direct potentiometry than by procedures involving dilution. Data consistent with this convention can be obtained with a variety of aqueous-based calibrants, provided care is taken to minimize the errors resulting from activity coefficient and liquid junction potential effects. Additional experimental results are presented to show that these effects also account for the apparent suppression of the sodium ion concentration observed in the presence of bicarbonate ion.

Bicarbonates↗
PubMed1977

n-Type Si-based photoelectrochemical cell: New liquid junction photocell using a nonaqueous ferricenium/ferrocene electrolyte.

n-Type Si has been shown to serve as a stable photoanode in a cell for the conversion of light to electricity. The other components of the cell are a Pt cathode and an electrolyte consisting of an ethanol solution of [n-Bu(4)N]ClO(4) with a redox couple of ferricenium/ferrocene. Data from a two-compartment cell show that ferrocene is oxidized to ferricenium with 100 +/- 2% current efficiency at the Si photoanode. Furthermore, prolonged irradiation of the Si in a one-compartment cell yields constant photocurrent and output characteristics. The maximum open-circuit photopotential is approximately 700 mV, and the short-circuit quantum yield for electron flow at low light intensity exceeds 0.5. Conversion of monochromatic 632.8-nm light to electricity with approximately 2% power efficiency at an output voltage of approximately 200 mV has been sustained. These results represent a stable n-type Si-based photoelectrochemical cell.

Journal Article↗