An Iron Impurity in Multiwalled Carbon Nanotube Complexes with Chitosan that Biomimics the Heme‐Peroxidase Function

Abstract

A new biomimetic functional system having an impure multiwalled carbon nanotube (MWCNT-Fe)-chitosan biopolymer (H2N-CHIT) chemically modified glassy carbon electrode (GCE/[MWCNT-Fe:H2N-CHIT]) has been developed and demonstrated efficient hydrogen peroxide electrocatalytic and electrochemical sensing applications in pH 7 phosphate buffer solution (PBS). The hybrid system showed a stable and well-defined surface confined redox peak at an apparent electrode potential, E°'=-0.22 V versus Ag/AgCl with surface excess value 13.63 nmol cm(-2). Physicochemical characterizations of the hybrid by using FESEM, TEM, Raman spectroscopy, FTIR, and various control electrochemical experiments revealed that the iron impurity in the MWCNT interacted with the amino functional group of the chitosan polymer and thereby formed an unique complex-like structure ([MWCNT-Fe(III/II):NH2-CHIT]), similar to heme peroxidase with a central Fe(III/II)-redox-active site. The biomimetic system followed Michaelis-Menten-type reaction kinetics for the H2O2 reduction reaction with a K(M) value of 0.23 mM. At pH 7, amperometric i-t sensing and flow-injection analysis of H2O2 on the biomimetic system showed calibration plots in windows 5-500 and 50-2500 μM, with detection-limit values of 2.3 and 9.7 μM, respectively. Unlike most of the previously reported systems that undergo serious interferences in physiological pH, the biomimetic system displayed a remarkable tolerance to other co-existing interferants (such as cysteine, ascorbic acid, uric acid, nitrate, and nitrite), at a H2O2 detection potential similar to the peroxidase enzyme. The ability of the biosensor system to perform routine analyses was demonstrated by the detection of H2O2 present in simulated milk and clinical and cosmetic samples with appreciable recovery values.

Intrinsic Iron‐Containing Multiwalled Carbon Nanotubes as Electro‐Fenton Catalyst for the Conversion of Benzene to Redox‐Active Surface‐Confined Quinones

“…The total amount of metal impurities (Fe, Co, and Ni) in the pristine MWCNTs was estimated as 5.2 wt % by using thermal gravimetric analysis (TGA) . Continuum source electro‐thermal atomic absorption spectrometry (CS‐ETAAS) studies using ZEEnit 65, Analytika Jena AG (Germany) showed a 2.1 wt % iron impurity within the pristine MWCNTs .…”

“…Similarly, Fe 2 O 3 immobilized on MWCNTs was used as a Fenton reagent for the dye decomposition reaction. [5 g] Meanwhile, the intrinsic iron impurity in MWCNTs has been derived as iron‐based molecular units such as MWCNT‐Fe*(bpy) 3 2+ , MWCNT‐Fe*:NH 2 ‐chitosan, and MWCNT‐Fe*:iron hexacyanoferrate hybrids. To the best of our knowledge, the iron in MWCNTs has never been utilized as a Fenton reagent or catalyst for the chemical or electrochemical reaction.…”

Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy

“…Even trace concentrations of metal ions can cause data misinterpretation in the former and electrical breakdown in the latter. This significant catalyst involvement in redox activity has been detected through hydrogen peroxide electrocatalysis examination and electrochemical activity demonstrations using Fe‐rich CNTs …”

Residual Metal Impurity Aids Facile In Situ Electrochemical Surface Derivatization of Single‐Walled Carbon Nanotubes

“…[10] Nossol et al also reported on intentionally introduction of excess Fe species into MWCNTs by synthesis from ferrocene as precursor (carbon source and catalyst for CNT growth by chemical vapor deposition) and their transformation into Prussian blue for amperometric detection of hydrogen peroxide. Keywords: carbon · electrochemistry · nanoparticles · nanotubes · nickel improved molecular wiring of hemoglobin through the metal impurities of multiwalled CNTs (MWCNTs).…”