Abstract
This paper presents a simple, high resolution imaging approach utilizing ratiometric planar optode for simultaneous measurement of dissolved oxygen (DO) and pH. The planar optode comprises a plastic optical film coated with oxygen indicator Platinum(II) octaethylporphyrin (PtOEP) and reference quantum dots (QDs) embedded in polystyrene (PS), pH indicator 5-Hexadecanoylamino-fluorescein (5-Fluorescein) embedded in Hydromed D4 matrix. The indicator and reference dyes are excited by utilizing an LED (Light Emitting Diode) source with a central wavelength of 405 nm, the emission respectively matches the different channels (red, green, and blue) of a 3CCD camera after eliminating the excitation source by utilizing the color filter. The result shows that there is low cross-sensitivity between the two analytes dissolved oxygen and pH, and it shows good performance in the dynamic response ranges of 0–12 mg/L and a dynamic range of pH 6−8. The optode has been tested with regard to the response times, accuracy, photostability and stability. The applied experiment for detecting pH/Oxygen of sea-water under the influence of the rain drops is demonstrated. It is shown that the planar optode measuring system provides a simple method with low cross-talk for pH/Oxygen imaging in aqueous applications.
Highlights
Microelectrodes have been widely used in underwater observation, enabling the further understanding of chemical gradients of seawater [1]
The majority of planar optode studies have been focused on pH and oxygen dynamics in rhizospheres [4,5,6]; measurements in sea-ice for resolving physical and biologically induced oxygen dynamics [7]; marine sediments including the investigation of microbial mats and biofilms [8,9]; effects of bioturbating/irrigating fauna [10,11,12]; and studies of pH two-dimensional in benthic substrates [13,14]
By doping the quantum dots (QDs) as the reference dye, a new ratiometric pH/Oxygen planar optode combination with a 3CCD camera was designed for simultaneous imaging of pH and oxygen
Summary
Microelectrodes have been widely used in underwater observation, enabling the further understanding of chemical gradients of seawater [1]. The imaging system of 3CCD camera uses three separate charge-coupled devices (CCDs), each one taking a separate measurement of the primary colors, red, green, or blue light. By doping the QDs as the reference dye, a new ratiometric pH/Oxygen planar optode combination with a 3CCD camera was designed for simultaneous imaging of pH and oxygen. The planar optode used PtOEP as the oxygen indicator with red emission, 5-Fluorescein as the pH indicator with green emission, and QDs as the reference dye with blue emission. These three dyes were respectively embedded in polystyrene (PS) and Hydromed D4 matrix. The performance of the planar optode was validated for detecting pH/ Oxygen of sea-water under the influence of the rain drops [35,36]
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