Development of Optical Sensors for Chemical Detection

Detection of biodiesel at low and high concentrations in diesel is highly desired in the aviation and fuel industries. Cross contamination of jet fuel with biodiesel may impact the thermal stability and freezing point which can cause deposits in the fuel system or cause the fuel to gel, leading to jet engine operability problems and possible engine flameout. A dye doped optical sensor utilizing the dye Nile Blue Chloride has been developed for quick and direct detection of biodiesel which mainly contains fatty acid methyl esters (FAME). The sensing mechanism relies on the solvatochromatic properties of the dye which undergoes a color change from blue to pink. A detection limit of 0.250 ppm (parts per million) and quantification limit of 0.750 ppm is obtained with a dynamic range from 0.5–200,000 ppm (20% v/v) FAME. This sensor is a viable alternative to compliment more sophisticated and expensive bench top techniques in current use.

The detection of chloroform in aqueous and non-aqueous has direct environmental and pharmaceutical applications, due to its well documented toxicity. A sensor has been developed based on a modified Fujiwara reaction for detecting chloroform, a halogenated hydrocarbon, in the visible spectrum. 2,2’-dipyridyl and tetra-n-butyl ammonium hydroxide are the modified Fujiwara reagents encapsulated within a sensing film. Upon exposure to chloroform in non-aqueous solution, a colored product is produced within the film which can be analyzed spectroscopically yielding a detection limit of 0.830 ppm (v/v) and quantification limit of 2.77 ppm.

Monitoring and detection of gas plume constituents is a useful diagnostic tool in evaluating combustion efficiency, ensuring safe testing conditions, and in quantifying greenhouse gas emissions. Rocket engine ground tests are vital to ensure the performance of the rocket engines during critical space missions. Optical sensors were developed for remote sensing applications to detect isopropyl alcohol utilizing the dye Chromoionophore IX. This sensor gave a detection limit of 9, 13, 21 ppm and quantification limits of 32, 43, and 70 ppm for methanol, ethanol, and isopropyl alcohol respectively. Also a fingerprinting method was developed utilizing several indicator dyes in order to detect kerosene vapor.