Methylene blue-carbon nitride system as a reusable air-sensor
© 2019 Elsevier B.V. Methylene blue (MB)is a dye widely used as an optical redox indicator in analytical chemistry, whose color change is also affected by pH. It was irreversibly adsorbed on polymeric carbon nitride (g-C3N4)prepared either from urea or from melamine cyanurate. Electron spin resonanc...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://repository.li.mahidol.ac.th/handle/123456789/51175 |
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| Institution: | Mahidol University |
| Summary: | © 2019 Elsevier B.V. Methylene blue (MB)is a dye widely used as an optical redox indicator in analytical chemistry, whose color change is also affected by pH. It was irreversibly adsorbed on polymeric carbon nitride (g-C3N4)prepared either from urea or from melamine cyanurate. Electron spin resonance (ESR)showed an increase in radicals or unpaired electrons in the MB-g-C3N4 system in comparison to pure g-C3N4. Upon treatment with potassium hydroxide, an abrupt color change from blue to purple occurred, together with a decrease in the ESR signal. Exposure to air caused a shift to the initial blue color, and, as suggested by UV-Vis spectroscopy data, the system returned to its original state, before the treatment with alkali. This behavior suggests the suitability of the MB-g-C3N4 system as a promising reusable sensor for the detection of exposure to air (and/or to carbon dioxide)of products stored under vacuum or in a controlled atmosphere. Thus, visual indicators based on this material may find applications as cost-effective leakage indicators for the modified atmosphere package (MAPs)industry, in particular to assess food safety or for electronic packaging. |
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