A Handheld Dissolved Oxygen Optosensor Based On Fluorescence Quenching

The determination of molecular oxygen levels in solution is of great importance in environmental, biomedical, and industrial analyses. A hand held optode oxygen sensor has been fabricated, based on the fluorescence quenching of tris(4,7-diphenyl-l,10-phenanthroline) ruthenium(II) ditetrakis(4-chlorophenyl)borate in the presence of dissolved oxygen.The developed hand-held dissolved oxygen optosensor based on All- Solid- State electronics and fluorescence quenching of a highly oxygen-sensitive luminescence complex. The oxygen-sensitive optode membrane was fabricated from Ruthenium(U) complex adsorbed on silica gel particles and embedded in a silicone-rubber film. The maximum EX/EM wavelength of the membrane is 472/610 nm, respectively. Oxygen in the surrounding medium quenches the fluorescence and is quantified by means of the Stem-Volmer expression at range of 0-2 or 2-8 mg/L. A responding time of T95=5s was obtained from high dissolved oxygen (DO) concentration to low DO concentration. High reversibility and photo stability of the oxygen sensitive membrane is demonstrated. The optode Excitation was achieved with an ultra-bright blue 472 nm light-emitting diode (LED), with emission monitored by a highly sensitive silicon photo diode(PD). The LED excitation and photodiode detection are employed in a trapeziform plastic configuration, with the oxygen-sensitive film coated on a 580nm long pass filter. The fluorescence intensity signal of the optode membrane was converted to the voltage signal, which was processed by a Single Chip Micyoco Controller microprocessor, PIC16F84. An assemble language program was developed for the unit control, data sampling, detection calculation and calibration. And the dissolved oxygen concentration was worked out and displayed on a liquid crystal display unit. The developed hand-held optosensor is pocketsize and low energy consuming, which provides on line dissolved oxygen measurement.A novel fluorescence oxygen sensor with Pt-T(p-Br)PPH2 as its sensing material andPVC polymer as support system is presented in the paper. When excited at the wavelength of 402nm and measured the emission at the wavelength of 664nm, the sensor shows a linear response to oxygen within the concentration range from 0 to 100% O2 with a ratio more than 40 of IN2 /IO2, where IN2 is the fluorescence intensity in 100% N2 and IO2, is the fluorescence intensity in 100% O2, respectively. The working curve is fit for the Stern-Volmer equation. The shell lifetime of the sensor was found to be longer than three months.