Abstract
Two Covalent Organic Frameworks (COF), named TFP-BZ and TFP-DMBZ, were synthesized using the imine condensation between 1,3,5-triformylphloroglucinol (TFP) with benzidine (BZ) or 3,3-dimethylbenzidine (DMBZ). These materials were deposited, such as films over interdigitated electrodes (IDE), by chemical bath deposition, giving rise to TFP-BZ-IDE and TFP-DMBZ-IDE systems. The synthesized COFs powders were characterized by Powder X-Ray Diffraction (PXRD), Fourier Transform Infrared spectroscopy (FT-IR), solid-state Nuclear Magnetic Resonance (ssNMR), nitrogen adsorption isotherms, Scanning Electron Microscopy (SEM), and Raman spectroscopy, while the films were characterized by SEM and Raman. Ammonia and low molecular weight amine sensing were developed with the COF film systems using the impedance electrochemical spectroscopy (EIS). Results showed that the systems TFP-BZ-IDE and TFP-DMBZ-IDE detect low molecular weight amines selectively by impedimetric analysis. Remarkably, with no significant interference by other atmospheric gas compounds such as nitrogen, carbon dioxide, and methane. Additionally, both COF films presented a range of sensitivity at low amine concentrations below two ppm at room temperature.
Highlights
Our ecosystem and human activities can release a great variety of gas compounds to the atmosphere, including greenhouse gases
Results showed that the systems TFP-BZ-interdigitated electrodes (IDE) and TFP-DMBZ-IDE detect low molecular weight amines selectively by impedimetric analysis
Characterization was a difficult procedure, and after several attempts of that, it was decided to make an extensive characterization of this residual powder and take it as a comparison pattern for the characterization of the Covalent Organic Frameworks (COF)-electrode systems
Summary
Our ecosystem and human activities can release a great variety of gas compounds to the atmosphere, including greenhouse gases (carbon dioxide, methane, ozone, among others). Several techniques have been used in commercial ammonia detectors, among them, metal–oxide gas sensors [7,8,9,10,11], conducting polymer analyzers, and detection optical methods [12,13,14,15,16,17] These strategies exhibit some disadvantages associated with high temperatures and irreversible reactions. In order to improve the gas sensing properties, some researchers have developed new approaches to increase the specific surface area and using composite films [18] In this way, chemosensors synthetized on interdigitated electrodes (IDE) have been used frequently. There have not been reports using COF and electric impedance for the detection of ammonia
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