How to implement a selective colorimetric gas sensor with off the shelf components?

Abstract

We report on how an inexpensive and very selective gas sensor can be implemented, simply combining colorimetric indicators casted on top of Scotch  tape, with a commercial microchip adapted here to measure optical reflectance.The system can be easily reproduced (leading to quantitatively consistent results), refreshed and reconfigured to sense different target gases, just replacing the colorimetric.Colorimetric methods put at our disposal a wide arsenal of compounds and reaction mechanisms to address specific gaseous molecules. A colorimetric indicator is a substance that develops light absorption at specific wavelengths in the presence of the target substances. These techniques are widely spread in analytical chemistry and offer unbeatable levels of selectivity and specificity towards the target species [1][2][3][4][5][6], if compared to other popular transduction methods like solid state conductometric sensors or electrochemical devices [7][8][9][10][11][12][13]. However, colorimetry often raises concerns about the long-term stability

Programmable and Modularized Gas Sensor Integrated by 3D Printing

“…Precision-engineered auxiliary components can also play a pivotal role in optimizing sensor performance. For example, colorimetric gas sensors, a special kind of optical gas sensor, operate by detecting the color change in active materials upon exposure to target gases. , These sensors are fundamentally composed of a light source, a layer of gas-reactive materials, and a photodetector, but a waveguide is necessary to guide the light path and reduce the light loss. This kind of precision component is also promising to be well-designed in its digital form and fabricated by 3D printing accurately.…”

Metal–Organic Framework Flowers as a Naked-Eye Colorimetric Indicator of Trace Water

“…16−18 In addition, the independence of the availability without power sources could bring unprecedented portability and usability. 19,20 Therefore, it is much desirable for developing colorimetric indicators with rapid response and high sensitivity in trace water detection applications.…”

“…Water detection and sensing in the atmosphere/liquid are of great importance throughout various human production and living activities. − Especially in many applications such as industrial gas, precise instrument, semiconductor manufacturing, research labs, and medicinal storage, in which trace water in a gas/solvent is always regarded as a destructive contaminant, humidity sensing needs to be strictly controlled. − To this end, water detection and sensing techniques such as Karl Fischer titration, chromatography, fluorescent, and electrochemical methods have been developed by researchers to achieve effective monitoring of trace water. − However, these traditional methods still rely on the need of special instruments and well-trained operators, resulting in poor portability and energy/time consumption. , Moreover, it is also expensive to set up these traditional methods for continuous monitoring at each process of industrial applications, that is, production, transfer, and storage steps, which would cause serious burden for practical applications. − Notably, the colorimetric indicators, which means the sensing signal is via a naked-eye visible color change, provide a favorable choice without requiring analytical instruments. − In addition, the independence of the availability without power sources could bring unprecedented portability and usability. , Therefore, it is much desirable for developing colorimetric indicators with rapid response and high sensitivity in trace water detection applications.…”

Hierarchical Dense Array of ZnO Nanowires Spatially Grown on ZnO/TiO2 Nanofibers and Their Ultraviolet Activated Gas Sensing Properties

“…Applications of small and reliable gas sensors with low response time and high selectivity and sensitivity to detect and monitor harmful, flammable, and toxic gases have drawn more attention during recent decades due to the existence of a wide range of fossil fuels in domestic and industrial environment and man-made environmental pollution and climate change. Lots of semiconducting oxides such as TiO 2 , ZnO, WO 3 , and In 2 O 3 have been used as gas sensors via changing the electrical properties of these materials when exposed to target gases. − …”