Investigation of Gasochromic Rhodium Complexes Towards Their Reactivity to CO and Integration into an Optical Gas Sensor for Fire Gas Detection

Abstract

The detection of the toxic gas carbon monoxide (CO) in the low ppm range is required in different applications. We present a study of the reactivity of different gasochromic rhodium complexes towards the toxic gas carbon monoxide (CO). Therefore, variations of binuclear rhodium complexes with different ligands were prepared. They were characterized by FTIR spectroscopy, 1H NMR spectroscopy, and differential scanning calorimetry. All complexes are spectroscopically distinguishable and temperature stable up to at least 187 °C. The gasochromic behavior of all different compounds was tested. Therefore, the compounds were dissolved in toluene and exposed to 100 ppm CO for 10 min to investigate their gas sensitivity and reaction velocity. The changes in the transmission spectra were recorded by UV/vis spectroscopy. Furthermore, a significant influence of the solvent to the color dyes’ gasochromic reaction and behavior was observed. After characterization, one complex was transferred as sensing element into an optical gas sensor. Two different measurement principles (reflection- and waveguide-based) were built up and tested towards their capability as gasochromic CO sensors. Finally, different gas-dependent measurements were carried out.

Adducts of Rhodium(II) Acetate and Rhodium(II) Pivalate with 1,8-Diazabicyclo[5.4.0]undec-7-ene

“…Rhodium(II) paddlewheel complexes [(Rh(II)] are an exceptionally diverse group of bimetallic scaffolds. These compounds have primarily been employed in catalysis to facilitate carbene mediated reactions [1,2], though they have also seen promising use in a variety of other applications such as potential anti-tumor drugs [3][4][5], sensors [6][7][8][9], and scaffolds for supramolecular assemblies [10][11][12]. Their ability to readily dissolve in most solvents while also maintaining air and moisture stability has certainly served to increase their utility over other transition metal scaffolds.…”

Indicator Supraparticles for Smart Gasochromic Sensor Surfaces Reacting Ultrafast and Highly Sensitive

“…This complex was presented in more details in refs. and . Integrated into the silica‐based supraparticles, the rhodium complex will show a color change from violet to yellow in presence of CO ( Figure a), which is caused by a reversible two‐step ligand exchange of the acetic acid by CO .…”

“… and . Integrated into the silica‐based supraparticles, the rhodium complex will show a color change from violet to yellow in presence of CO ( Figure a), which is caused by a reversible two‐step ligand exchange of the acetic acid by CO . Reflectance spectra are measured using a Harrick Praying Mantis diffuse reflectance accessory seated inside the sample compartment of a Perkin Elmer Lambda 900 UV–vis spectrometer (simplified in Figure b).…”

“…This reversible color change is not affected by other polar or nonpolar substances . For the use as CO sensing molecules, binuclear rhodium complexes have been recently proposed . These compounds show a reversible, fast, and selective reaction toward carbon monoxide …”

Catalytic Effects on the Nonisothermal Oxidation of Solid Fuels by Oxygen: An Experimental Study

“…The use of CO detectors/alarms [17] for warning against lethal combustion emissions has been embraced extensively. Some sensors are colorimetric [18], forming colored complexes as the concentrations of pollutants change [19]. Others are electrochemical which work by converting CO to CO2 that is detected using an electrolyte [20] between a working and a counter electrode.…”