Composite Material for Simultaneous and Contactless Luminescent Sensing and Imaging of Oxygen and Carbon Dioxide

Abstract

Oxidative respiration and photosynthesis are the most important biological processes of higher life on earth. The production of oxygen occurs exclusively as a result of photosynthesis, while CO 2 is produced (and O 2 is consumed) in oxidative respiration as well as in important processes such as fermentation and photorespiration of green plants.[1] Thus, itis not possible to distinguish between these processes when the concentration of only one analyte (CO 2 or O 2 ) is monitored. Measurement of both gases at the same time and in the same spot would therefore allow an improved quantitative interpretation of the underlying physiological processes. The online control of CO 2 and O 2 is also of major importance in biotechnology, [2,3] particularly during the phase of exponential cell growth, when enhanced respiration can lead to death due to anoxia. Simultaneous sensing of CO 2 and O 2 is also important in environmental monitoring (especially in seawater analysis), [4] and in clinical medicine with respect to measurement of blood-gas levels.[5] Unfortunately, there are currently no sensors that allow simultaneous sensing of O 2 and CO 2 without mutual interference. Infrared spectroscopy is widely used [6,7] for monitoring CO 2 in the gaseous phase. However, it is costly and suffers from interferences by humidity. Electrochemical determination of CO 2 by means of Severinghaus electrodes [8] can be affected by electromagnetic disturbances and suffers from drift and slow response. Optical chemical sensing is mostly based on the interrogation of a polymer-immobilized probe that displays analyte-dependent optical properties such as absorbance or luminescence.[9] Optical solid-state CO 2 sensors [10,11] contain a pH indicator and a lipophilic organic base dissolved in a hydrophobic polymer such as ethyl cellulose, [11][12][13][14] solgels, [15,16] silicone, [17] poly(trimethylsilylpropyne), [18] etc. Carbon dioxide dissolves in the polymer and neutralizes the base, which also acts as a phase-transfer agent. Luminescent optical sensors employ pH indicators (e.g., 8-hydroxypyrene-1,3,6-trisulfonate, HPTS) [16,17,19] displaying pH-dependent (and consequently CO 2 -dependent) fluorescence, and are usually more precise and sensitive than those based on absorption. [11,20] Fluorescence intensity is the classical parameter, but it suffers from photobleaching, indicator leaching, drifts of the optoelectronic system, and variation in the optical properties of the sample, including turbidity, coloration, and changes in the refractive index. The measurement of decay time is free of such drawbacks but requires bulky and expensive instrumentation for short-lived (nanoseconds) pH probes. Therefore, probes with long lifetimes are preferred. [21][22][23] Alternatively, the intensity of a short-lived indicator may easily be converted into a phase shift by a method referred to as dual-lifetime referencing (DLR). [24,25] Here, the short-lived fluorescence of a pH indicator is referenced against the long-lived phosphorescence of a reference ...

Extruded colour-based plastic film for the measurement of dissolved CO2

“…4-5 days under the same conditions, before losing its blue/green colour and changing to its yellow protonated form. As noted earlier, the lack of stability exhibited by many PT-based CO2 ink film sensors is usually attributed to a loss of water (if kept in a dry atmosphere) and possible permanent reaction with common, albeit low level, acidic pollutants, such as SO2 and NO2 [31]. Others have noted that the stability of the latter films can be improved markedly by storing them either in water [30], in a very humid (usually RH ≥ ca.…”

“…sensors is an inherent short shelf-life, probably due to the presence of other acidic gases, such as SO2 or NO2 in the atmosphere, that irreversibly protonate the sensor film [31]. Other, more recent, work shows that ambient humidity and sensor film water content are also important factors in determining PT CO2 sensor shelf-life, and that usually the higher the relative humidity the greater the shelf-life [30].…”

“…Interestingly, an exception appears to be the fluorescent-based, PT dissolved CO2 sensor sold currently by PreSens GmbH [31,32], which appears to be sold in a naked, i.e. GPM free, form.…”

Functional and structural imaging of phototrophic microbial communities and symbioses

“…Other combined sensor materials and measuring systems have been developed (Nagl & Wolfbeis 2007), e.g. for simultaneous imaging of O 2 and temperature (Borisov et al 2006b), or O 2 and CO 2 (Borisov et al 2006a). Such materials should be ideal for investigations of photosynthetic microbial communities and other applications in environmental microbiology.…”

A Dual Luminescent Sensor Material for Simultaneous Imaging of Pressure and Temperature on Surfaces

“…These beads are incorporated into a matrix polymer and can be applied in different systems like fiber optics [6] or sensor foils. [7,8] Finally, they can also be sprayed or painted on surfaces to cover areas of any shape. By means of pressure-sensitive or temperature-sensitive paints (PSPs/TSPs) these basic factors in fluid mechanics can be imaged and quantified noninvasively with an unsurpassed spatial resolution.…”