Portable optical air sensor: Difference between revisions
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==Sol-gel== |
==Sol-gel== |
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One of the primary methods of optical air sensing involves taking a [[sol-gel]], which is |
One of the primary methods of optical air sensing involves taking a [[sol-gel]], which is made by taking a [[Sol (colloid)|sol]], a liquid with stable colloidal particles, and mixing it with a [[gel]], which is a three dimensional continuous network encompassing a liquid.<ref name=4a>{{cite web|url=http://www.uio.no/studier/emner/matnat/kjemi/KJM5100/h06/undervisningsmateriale/10KJM5100_2006_sol_gel_d.pdf|title=Sol-Gel Methods}}</ref> The sol-gel is then exposed to a certain indicator which becomes part of the sol-gel. Typically the production of a sol-gel follows a [[hydrolysis]] and then [[condensation]] pathway. |
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Hydrolysis involves adding a hydrogen atom onto the gel. Condensation is a method involving bonding two different gel molecules together to create a sol-gel as a whole.<ref name=5a>{{cite journal|last1=Carrington|first1=N.|title=Inorganic Sensing using Organofunctional Sol-Gel Materials|journal=Acc. Chem. Res.|date=2006|volume=40|pages=343–350|doi=10.1021/ar600017w}}</ref> This method consists of dissolving some solid into a [[solvent]] and then maintaining a basic pH as the mixture is [[ |
Hydrolysis involves adding a hydrogen atom onto the gel. Condensation is a method involving bonding two different gel molecules together to create a sol-gel as a whole.<ref name=5a>{{cite journal|last1=Carrington|first1=N.|title=Inorganic Sensing using Organofunctional Sol-Gel Materials|journal=Acc. Chem. Res.|date=2006|volume=40|issue=5 |pages=343–350|doi=10.1021/ar600017w|pmc=2041924|pmid=17465520}}</ref> This method consists of dissolving some solid into a [[solvent]] and then maintaining a basic pH as the mixture is [[reflux]]ed to condense and produce a gel.<ref name=6a>{{cite journal|last1=Lopez|first1=T.|title=Synthesis and Characterization of Sol-Gel Hydrotalcites Structure and Texture|journal=Langmuir|date=1996|volume=12|pages=189–192|doi=10.1021/la940703s}}</ref><ref name=7a>{{cite journal|last1=Prince|first1=J.|title=Proposed General Sol-Gel Method to Prepare Multimetallic Layered Double Hydroxides: Synthesis, Characterization, and Envisaged Application|journal=Chem. Mater.|date=2009|volume=21|pages=5826–5835|doi=10.1021/cm902741c}}</ref> |
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One example of the sol-gel method in use today is the |
One example of the sol-gel method in use today is the feeling of air acidity. The sol-gel is made with an organic dye, (2-[4-([[Dimethylamine|dimethylamino]])- [[phenylazo]]][[benzoic acid]]). The dye has a pH color range of 6.7-8.7. This means that below a pH of 6.7 you see one color, in this case a red-pink, and at a pH higher than 8.7 you see a different color, in this case yellow, and you see a changing orange in between.<ref name=8a>{{cite journal|last1=Garcia-Heras|first1=M.|title=Evaluation of Air Acidity through Optical Sensors|journal=Environ. Sci. Technol.|date=2005|volume=39|issue=10 |pages=3743–3747|doi=10.1021/es049558n|pmid=15952380 |bibcode=2005EnST...39.3743G }}</ref> The testing procedure is incredibly simple since all you have to do is expose the sol-gel to the air and monitor the color change.<ref name="8a"/> |
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Sol-gels can also be formed into monoliths, or columns, which are larger structures of sol-gel, unlike the typical thin layer. These monoliths are shown to be better for sensing molecules with smaller molar absorptivity, which are molecules that don’t absorb into something very well. An example of a molecule that would be measured here is a metal-ligand complex. These monoliths operate in a similar method to the thin layer sol-gels in that they trap some [[analyte]] and show a color change.<ref name="5a"/> |
Sol-gels can also be formed into monoliths, or columns, which are larger structures of sol-gel, unlike the typical thin layer. These monoliths are shown to be better for sensing molecules with smaller molar absorptivity, which are molecules that don’t absorb into something very well. An example of a molecule that would be measured here is a metal-ligand complex. These monoliths operate in a similar method to the thin layer sol-gels in that they trap some [[analyte]] and show a color change.<ref name="5a"/> |
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==Fluorescence== |
==Fluorescence== |
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Another example of portable optical air sensors can involve [[fluorescence]]. One example of a fluorescence based sensor is an [[electronic nose]], which can measure analytes in vapor or air. It operates so that an analyte is detected by different sensors in different ways to ensure what is being measured can be differentiated.<ref name=9a>{{cite journal|last1=Aernecke|first1=M.|title=Design, Implementation, and Field Testing of a Portable Fluorescence-Based Vapor Sensor|journal=Anal. Chem.|date=2009|volume=81|pages=5281–5290|doi=10.1021/ac900505p}}</ref> As the vapor flows into the system it is hit with a high intensity light so that different organic dyes located in different small holes, or [[Microporous material|micropores]], emit a certain wavelength and varied intensity of light based on what vapor compound they are in contact with. The light from the different sensors can then be compiled and used to determine what analytes were present. One large application of the fluorescent method is the detection of [[ |
Another example of portable optical air sensors can involve [[fluorescence]]. One example of a fluorescence based sensor is an [[electronic nose]], which can measure analytes in vapor or air. It operates so that an analyte is detected by different sensors in different ways to ensure what is being measured can be differentiated.<ref name=9a>{{cite journal|last1=Aernecke|first1=M.|title=Design, Implementation, and Field Testing of a Portable Fluorescence-Based Vapor Sensor|journal=Anal. Chem.|date=2009|volume=81|issue=13 |pages=5281–5290|doi=10.1021/ac900505p|pmid=19563211}}</ref> As the vapor flows into the system it is hit with a high intensity light so that different organic dyes located in different small holes, or [[Microporous material|micropores]], emit a certain wavelength and varied intensity of light based on what vapor compound they are in contact with. The light from the different sensors can then be compiled and used to determine what analytes were present. One large application of the fluorescent method is the detection of [[volatile organic compound]]s (VOC’s).<ref name="9a"/> Another type of fluorescent sensor focuses on [[metal complexes]], rather than organic complexes. One example is the use of dirhodium tetracarboxylate structure to detect [[Nitric oxide|nitrogen monoxide]], a common pollutant. This involves a nitrogen monoxide molecule coming in and bonding to the dirhodium tetracarboxylate to cause a shift in the intensity of the fluorescence of the molecule.<ref name=10a>{{cite journal|last1=Hilderbrand|first1=S.|title=Dirhodium Tetracarboxylate Scaffolds as Reversible Fluorescence-Based Nitric Oxide Sensors|journal=J. Am. Chem. Soc.|date=2004|volume=126|issue=15 |pages=4972–4978|doi=10.1021/ja038471j|pmid=15080703}}</ref> |
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==Future== |
==Future== |
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The future of the portable air sensors is to design them better able to detect small amounts and better able to quantify the amounts that are detected. Most portable sensors are now used in conjunction with some larger, more accurate system within a lab. The advent of [[microfabrication]] techniques, [[Microelectromechanical systems|microelectro-mechanical systems]], energy efficient sensor circuits, and advanced computer power has allowed portable sensors to thrive, but continued advancement of those components would further advance the benefits of using portable systems.<ref name="1a">{{cite journal|date=2013|title=The Changing Paradigm of Air Pollution Monitoring.|journal=Environ. Sci. Technol.|volume=47|pages=11369–11377|doi=10.1021/es4022602|last1=Snyder|first1=E.}}</ref> |
The future of the portable air sensors is to design them better able to detect small amounts of sulfur and ammonia and better able to quantify the amounts that are detected. Most portable sensors are now used in conjunction with some larger, more accurate system within a lab. The advent of [[microfabrication]] techniques, [[Microelectromechanical systems|microelectro-mechanical systems]], energy efficient sensor circuits, and advanced computer power has allowed portable sensors to thrive, but continued advancement of those components would further advance the benefits of using portable systems.<ref name="1a">{{cite journal|date=2013|title=The Changing Paradigm of Air Pollution Monitoring.|journal=Environ. Sci. Technol.|volume=47|pages=11369–11377|doi=10.1021/es4022602|last1=Snyder|first1=E.|issue=20 |pmid=23980922|bibcode=2013EnST...4711369S }}</ref> |
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==References== |
==References== |
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[[Category:Air pollution]] |
[[Category:Air pollution]] |
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Latest revision as of 14:11, 9 January 2023
Optical air sensors center around the detection of some form of light created by a chemical process, in order to identify or measure amounts of individual molecules. Portable sensors are specifically sensors that are easy to transport and use in the field.
Sol-gel
[edit]One of the primary methods of optical air sensing involves taking a sol-gel, which is made by taking a sol, a liquid with stable colloidal particles, and mixing it with a gel, which is a three dimensional continuous network encompassing a liquid.[1] The sol-gel is then exposed to a certain indicator which becomes part of the sol-gel. Typically the production of a sol-gel follows a hydrolysis and then condensation pathway.
Hydrolysis involves adding a hydrogen atom onto the gel. Condensation is a method involving bonding two different gel molecules together to create a sol-gel as a whole.[2] This method consists of dissolving some solid into a solvent and then maintaining a basic pH as the mixture is refluxed to condense and produce a gel.[3][4]
One example of the sol-gel method in use today is the feeling of air acidity. The sol-gel is made with an organic dye, (2-[4-(dimethylamino)- phenylazo]benzoic acid). The dye has a pH color range of 6.7-8.7. This means that below a pH of 6.7 you see one color, in this case a red-pink, and at a pH higher than 8.7 you see a different color, in this case yellow, and you see a changing orange in between.[5] The testing procedure is incredibly simple since all you have to do is expose the sol-gel to the air and monitor the color change.[5]
Sol-gels can also be formed into monoliths, or columns, which are larger structures of sol-gel, unlike the typical thin layer. These monoliths are shown to be better for sensing molecules with smaller molar absorptivity, which are molecules that don’t absorb into something very well. An example of a molecule that would be measured here is a metal-ligand complex. These monoliths operate in a similar method to the thin layer sol-gels in that they trap some analyte and show a color change.[2]
Fluorescence
[edit]Another example of portable optical air sensors can involve fluorescence. One example of a fluorescence based sensor is an electronic nose, which can measure analytes in vapor or air. It operates so that an analyte is detected by different sensors in different ways to ensure what is being measured can be differentiated.[6] As the vapor flows into the system it is hit with a high intensity light so that different organic dyes located in different small holes, or micropores, emit a certain wavelength and varied intensity of light based on what vapor compound they are in contact with. The light from the different sensors can then be compiled and used to determine what analytes were present. One large application of the fluorescent method is the detection of volatile organic compounds (VOC’s).[6] Another type of fluorescent sensor focuses on metal complexes, rather than organic complexes. One example is the use of dirhodium tetracarboxylate structure to detect nitrogen monoxide, a common pollutant. This involves a nitrogen monoxide molecule coming in and bonding to the dirhodium tetracarboxylate to cause a shift in the intensity of the fluorescence of the molecule.[7]
Future
[edit]The future of the portable air sensors is to design them better able to detect small amounts of sulfur and ammonia and better able to quantify the amounts that are detected. Most portable sensors are now used in conjunction with some larger, more accurate system within a lab. The advent of microfabrication techniques, microelectro-mechanical systems, energy efficient sensor circuits, and advanced computer power has allowed portable sensors to thrive, but continued advancement of those components would further advance the benefits of using portable systems.[8]
References
[edit]- ^ "Sol-Gel Methods" (PDF).
- ^ a b Carrington, N. (2006). "Inorganic Sensing using Organofunctional Sol-Gel Materials". Acc. Chem. Res. 40 (5): 343–350. doi:10.1021/ar600017w. PMC 2041924. PMID 17465520.
- ^ Lopez, T. (1996). "Synthesis and Characterization of Sol-Gel Hydrotalcites Structure and Texture". Langmuir. 12: 189–192. doi:10.1021/la940703s.
- ^ Prince, J. (2009). "Proposed General Sol-Gel Method to Prepare Multimetallic Layered Double Hydroxides: Synthesis, Characterization, and Envisaged Application". Chem. Mater. 21: 5826–5835. doi:10.1021/cm902741c.
- ^ a b Garcia-Heras, M. (2005). "Evaluation of Air Acidity through Optical Sensors". Environ. Sci. Technol. 39 (10): 3743–3747. Bibcode:2005EnST...39.3743G. doi:10.1021/es049558n. PMID 15952380.
- ^ a b Aernecke, M. (2009). "Design, Implementation, and Field Testing of a Portable Fluorescence-Based Vapor Sensor". Anal. Chem. 81 (13): 5281–5290. doi:10.1021/ac900505p. PMID 19563211.
- ^ Hilderbrand, S. (2004). "Dirhodium Tetracarboxylate Scaffolds as Reversible Fluorescence-Based Nitric Oxide Sensors". J. Am. Chem. Soc. 126 (15): 4972–4978. doi:10.1021/ja038471j. PMID 15080703.
- ^ Snyder, E. (2013). "The Changing Paradigm of Air Pollution Monitoring". Environ. Sci. Technol. 47 (20): 11369–11377. Bibcode:2013EnST...4711369S. doi:10.1021/es4022602. PMID 23980922.