In a recent article published in the journal ACS Omega, researchers presented the functionalization of carbon nanofibers with an aromatic diamine to develop a selective electrochemical sensor for glucose detection.
Study: Carbon Nanofiber Sensor Revolutionizes Glucose Detection. Image Credit: Andrey_Popov/Shutterstock.com
Background
Carbon nanofibers are prized for their high surface area and excellent electrical conductivity, qualities that make them ideal for sensor applications. By functionalizing these nanofibers with specific groups, their ability to detect and measure substances can be significantly enhanced. The study outlined in this article highlights the critical role of surface processing in boosting both the sensitivity and selectivity of sensors, including those used for detecting glucose.
The Current Study
In this study, the researchers outline the synthesis of flexible, amine-functionalized carbon nanofibers (CNFs-NH2) through a series of chemical reactions with aromatic diamines. Initially, 500 mg of carbon nanofibers, each approximately 100 nm thick, were dispersed in 50 mL of 1,2-dichlorobenzene. The mixture was sonicated for 15 minutes to ensure uniform dissolution.
During functionalization, the carbon nanofibers were chemically bonded with an aryl diazonium salt that featured an amine group protected by a tert-butyloxycarbonyl (Boc) group. This step followed a documented procedure where aniline was reacted with isopentyl nitrite to generate the aryl diazonium salt under in situ conditions.
Various characterization techniques were employed to explore the morphological and microstructural changes in the synthesized CNFs-NH2. Scanning electron microscopy (SEM) provided visual confirmation of the nanofibers’ morphology before and after processing. X-Ray diffraction (XRD) analysis was utilized to identify the crystalline structures of the samples, focusing particularly on the C(002) and C(100) peaks indicative of the hexagonal graphite structure.
The content of amine groups in the CNFs-NH2 was quantified using the Kaiser assay, offering critical insights into the surface chemistry essential for further electrochemical sensing experiments.
Further chemical analysis was conducted using infrared spectroscopy (FTIR) to identify the specific bonds and functional groups present in the CNFs-NH2. Thermogravimetric analysis (TGA) was also performed to assess the thermal stability and degradation patterns of the functionalized nanofibers under controlled temperature conditions.
Results and Discussion
The comparison of SEM images of pristine carbon nanofibers (CNFs) and their NH2 derivatives (CNFs-NH2) revealed that the processing procedure preserved the morphology of the fiber length in the raw carbon material. This observation confirmed successful surface functionalization with aromatic diamine without altering the overall size structure of the nanofibers. XRD analysis corroborated this finding, showing main peaks corresponding to the same crystal planes in both samples. This supported the hypothesis that the functionalization process did not disrupt the underlying crystal structure of the carbon nanofibers.
The Kaiser test results indicated a significant presence of free amines in the CNFs-NH2, with a measured value of 471 μmol/g. This abundance of amino functional groups on the surface of the modified carbon nanofibers was crucial for enhancing interactions with glucose molecules in the electrochemical sensing system. The increased amine content improved the sensitivity and selectivity of the sensor towards glucose, thereby enhancing the efficacy and accuracy of the assay.
Electrochemical measurements on the CNFs-NH2 incorporated in a screen-printed carbon electrode (CNFs-NH2/SPCE) demonstrated promising results for glucose sensing. Impedance spectroscopy analysis highlighted the sensor's specific response to varying glucose concentrations and confirmed its potential as an effective electrochemical glucose sensor. The distinctive enhancements in the spectra, such as N-H broadening vibrations and C-H alkyl functionalities, further underscored the efficient synthesis of carbon nanofibers with aromatic diamines.
The proposed mechanism for selective glucose sensing in CNFs-NH2/SPCE involved the formation of a reversible azomethine bond between the surface-exposed amino group of the glucose molecule and the carbonyl group of the aromatic diamine. This functionalization rendered the interaction more sensitive to glucose compared to other sugars, such as fructose and sucrose, contributing to the sensor's high selectivity. These results indicated a specific and effective sensing mechanism driven by the unique surface chemistry of the modified carbon nanofibers.
Conclusion
The study presented a straightforward and effective method for functionalizing carbon nanofibers with an aromatic diamine to develop a sensitive and selective material for glucose detection.
The enzyme-free electrochemical sensor based on these modified carbon nanofibers exhibited considerable potential for selective glucose sensing. These findings underscored the importance of surface functionalization in enhancing sensor performance for specific analytes and set the stage for future advancements in electrochemical sensing technologies.
Journal Reference
Angelo F., Consuelo C., et al. (2024). Functionalization of Carbon Nanofibers with an Aromatic Diamine: Toward a Simple Electrochemical-Based Sensing Platform for the Selective Sensing of Glucose. ACS Omega, 00525. https://doi.org/10.1021/acsomega.4c00525, https://pubs.acs.org/doi/full/10.1021/acsomega.4c00525