Facile Fabrication of Wood-Derived Porous Fe3C/Nitrogen-Doped Carbon Membrane for Colorimetric Sensing of Ascorbic Acid

Abstract

Fe₃C nanoparticles hold promise as catalysts and nanozymes, but their low activity and complex preparation have hindered their use. Herein, this study presents a synthetic alternative toward efficient, durable, and recyclable, Fe₃C-nanoparticle-encapsulated nitrogen-doped hierarchically porous carbon membranes (Fe₃C/N-C). By employing a simple one-step synthetic method, we utilized wood as a renewable and environmentally friendly carbon precursor, coupled with poly(ionic liquids) as a nitrogen and iron source. This innovative strategy offers sustainable, high-performance catalysts with improved stability and reusability. The Fe₃C/N-C exhibits an outstanding peroxidase-like catalytic activity toward the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of hydrogen peroxide, which stems from well-dispersed, small Fe₃C nanoparticles jointly with the structurally unique micro-/macroporous N-C membrane. Owing to the remarkable catalytic activity for mimicking peroxidase, an efficient and sensitive colorimetric method for detecting ascorbic acid over a broad concentration range with a low limit of detection (~2.64 µM), as well as superior selectivity, and anti-interference capability has been developed. This study offers a widely adaptable and sustainable way to synthesize an Fe₃C/N-C membrane as an easy-to-handle, convenient, and recoverable biomimetic enzyme with excellent catalytic performance, providing a convenient and sensitive colorimetric technique for potential applications in medicine, biosensing, and environmental fields.

Keywords: ascorbic acid; colorimetric detection; iron carbide nanoparticles; nitrogen-doped carbon; wood-derived carbon.

Figure 1

(a,b) Cross-sectional SEM images of Fe₃C/N–C, respectively. The inset in (a) shows the photograph of the final membrane prepared at 900 °C. (c) Elemental mapping of different elements in Fe₃C/N–C, (d) TEM image of Fe₃C/N–C, and (e,f) HR-TEM images of Fe₃C/N–C.

Figure 2

(a) Raman spectrum, (b) XRD pattern, and (c) XPS full survey spectrum of the obtained Fe₃C/N–C; (d–f) XPS survey spectra of C 1s, N 1s, and Fe 2p, respectively.

Figure 3

(a) UV-Vis absorbance and the corresponding optical photographs of the ox-TMB recorded in three systems (TMB + H₂O₂, TMB + Cat, TMB + H₂O₂ + Cat) in acetate buffer solutions at a pH value of 4.0. (b) Time-dependent absorbance spectra of ox-TMB at 652 nm in the three systems (TMB + H₂O₂, TMB + Cat, TMB + H₂O₂ + Cat). (c,d) Dependence of the peroxidase-like activity of the obtained Fe₃C/N–C catalyst with varied temperature and pH values, respectively. (e) UV-Vis absorbance of the ox-TMB recorded with three catalysts (powder Fe₃C/N–C, membrane Fe₃C/N–C, pure carbon membrane) in acetate buffer solutions at a pH value of 4.0. (f) The stability test of the catalyst after 10 cycles of use.

Figure 4

Steady-state kinetic experiments of Fe₃C/N–C for catalytic tests. (a) The concentration of H₂O₂ was 50 mM and the TMB concentration varied. (b) Lineweaver–Burk plots for TMB substrate. (c) The concentration of TMB was 200 µM and the H₂O₂ concentration varied. (d) Lineweaver–Burk plots for H₂O₂ substrate. An amount of 20 μL of catalyst (3 mg·L⁻¹) was used in this experiment conducted at room temperature.

Figure 5

(a) Absorbance changes of the mixing solution consisting of TMB, the catalyst suspension, and H₂O₂ in the absence or presence of ascorbic acid and corresponding optical photographs. (b) Linear calibration plot to detect ascorbic acid. ΔA = A (652 nm, absence) − A (652 nm, ascorbic acid). (c) ΔA values of the Fe₃C/N–C–TMB–H₂O₂ system at 652 nm in the presence of ascorbic acid or other interferential substances.