Solid state nanofluidic channels are promising tools for the selective detection of analytes. However, the delayed interaction of recognition fractions with analytes makes it difficult to apply them to rapid detection devices. In a recent article in the journal Analytical Chemistry, researchers fabricated two-dimensional covalent organic frames (2D COFs) to integrate them into solid-state nanofluidic channels and achieve selective, sensitive, and rapid detection units that can detect contaminants in Sample. analytes.
Study: Integration of ordered two-dimensional covalent organic frames into solid-state nanofluidic channels for ultrafast and sensitive detection of mercury. Image credit: BeataGFX / Shutterstock.com
Rapid sensors to detect sample analytes
Contaminants that threaten human health, including heavy ions, biotoxins, veterinary drugs, foodborne pathogens, and pesticides present in food and the environment require sound analytical platforms for the rapid detection of these contaminants.
Although mass spectrometry, electrochemical detection and fluorescence detection with high performance liquid or gas chromatography are used for real sample analysis, a more sensitive, fast, selective and portable analysis equipment it is highly desirable.
Solid state nanofluidic channels functionalized with a specific recognition fragment are sensitive and selective for detecting specific analytes. To this end, nanofluidic sensors are sensitive to even a single molecule that causes steady-state current changes attributed to chemical change, wettability, surface charge, and nanofluidic channel diameter.
The introduction of specific recognition fragments, including phenylboronic acid, aptamer, antibodies, and organic metal frames (MOFs) into nanofluidic channels can enhance target-specific selectivity. However, the delayed interaction between the recognition parts and the targets limits the use of nanofluidic channel-based sensors as rapid detectors.
Therefore, it is essential to improve the interaction kinetics between the recognition fragments and the analytes of the nanofluidic channels. Crystalline COFs have an orderly structure, permanent pores, and a large surface area and are known to have improved kinetics for interaction with analytes, suggesting that 2D COFs may be promising nanofluidic channels.
2D COFs for mercury recognition (Hg (II)).
In the present study, the researchers designed a nanofluidic sensor based on anodic aluminum oxide (AAO) functionalized with 2D COF for accurate and rapid detection of contaminants. COF linked to 2D thiourea (JNU-3) functionalized AAO ([email protected]) was made by decorating the outer surface of the AAO with JNU-3 by a covalent interaction.
In addition, the sensitivity of the prepared nanofluidic sensor was selected by selecting Hg (II) as analyte. The affinity of JNU-3 for Hg (II) promoted selectivity and kinetics [email protected] sensors for Hg (II) recognition. These sensors were ideal for practical applications to detect Hg contamination in water and rice samples.
Research results
Scanning electron microscopy (SEM) images showed that the AAO reaction with (3-aminopropyl) -triethoxysilane (APTES) resulted in a smoother surface than the original AAO confirming the formation of AAO-amine ( NH2). Subsequent reaction of AAO-NH2 with COF monomer resulted in a change in color from white to dark orange indicating the growth of JNU-3.
Control of COF monomer concentration adjusted the amount of JNU-3 bound. Increasing the concentration of 1,3,5-triformylfloroglucinol (Tp) from 0.05 to 0.1 mol per liter resulted in a darker color of the nanochannels. SEM images revealed that with the increase in Tp concentration to 0.075 moles per liter, the JNU-3 obtained covered all channels, and an extended increase to 0.1 moles per liter resulted in a tube of full COF reaction which decreased the reproducibility of [email protected]
AAO-NH2 spectra obtained from X-ray photoelectron (XPS) spectroscopy showed peaks of nitrogen (N) 1s and silicon (Si) 2p, which represented the introduction of the -NH2 group of APTES. Similarly, the XPS spectra of [email protected] showed a peak of sulfur (S) 2p, which indicates the growth of JNU-3 to AAO-NH2.
The change in contact angle and zeta potential (ζ-) also demonstrated the formation of [email protected] When introducing -NH2 with a positive charge, the potential ζ changes from -43.3 ± 1.8 to -11.8 ± 1.3 electron volts. The in situ reaction of [email protected] with Tp and 1,4-phenylenebis- (thiourea) (Pa-S) resulted in a further drop in the potential ζ to -42.1 ± 3.1 electron volts, and this drop is attributed to the negative charge of JNU-3.
The contact angle of [email protected] increased from 17.2 ± 1.4 to 35.1 ± 0.6 degrees due to the APTES alkyl chain. A further increase in the contact angle was observed up to 49.5 ± 1.9 degrees after the reaction of [email protected] with Tp and Pa-S, due to the lower hydrophilicity of JNU-3.
AAO-NH2 powder X-ray diffraction (PXRD) patterns did not show PXRD peaks. Despite this, [email protected] revealed the presence of two characteristic peaks of JNU-3 at 3.50 and 5.99 degrees, indicating the crystallinity of JNU-3 at AAO-NH2.
Conclusion
In summary, the researchers designed and fabricated thiourea-bound COF-functionalized AAO as a nanofluidic sensor to detect Hg (II). A [email protected] The sensor was developed in situ to recognize Hg (II). JNU-3 consists of ordered channels that greatly promote the kinetics of interaction between them [email protected] and Hg (II): this allows the ultrafast detection of Hg (II) in real samples.
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Ran, XQ, Qian, HL and Yan, XP (2022). Integration of ordered two-dimensional covalent organic frames into solid-state nanofluidic channels for ultrafast and sensitive detection of mercury. Analytical Chemistry. https://pubs.acs.org/doi/abs/10.1021/acs.analchem.2c01595
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