Ce doped ZnO/f-MWCNT moss ball like nanocomposite: a strategy for high responsive current detection of L-tryptophan.

An electrochemical sensor is described for the determination of L-tryptophan (TRP). The method is based on the use of a glassy carbon electrode (GCE) modified with a nanocomposite consisting of moss ball-like cerium-doped ZnO and functionalized multiwalled carbon nanotubes (Ce-ZnO/f-MWCNT). Ce-doped ZnO was synthesized by a low temperature hydrothermal method. The Ce-ZnO/f-MWCNT nanocomposite was characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, FTIR and field emission scanning electron microscopy. The nanocomposite was drop cast on a GCE for use in electrochemical detection of TRP via cyclic voltammetry and differential pulse voltammetry. The oxidation peak current (0.76 V vs. Ag/AgCl) is strongly improved compared to a bare GCE. The experimental parameters such as solution pH value, scan rate, stability, concentration, reproducibility and repeatability were optimized. Response is linear in the 10 to 100 nM TRP concentration range, the limit of detection is 1.2 nM, and the sensitivity is 2.59 μA·nM-1·cm-2. The electrode was applied to the determination of TRP in spiked real samples and gave satisfactory results. Graphical abstract Schematic presentation of the preparation of a moss ball like nanocomposite consisting of cerium-doped ZnO and functionalized MWCNTs. cerium-Deposited on a on glassy carbon electrode, it enables nanomolar detection of L-tryptophan by differential pulse voltammetry.