Fabrication of WO2/W@C core-shell nanospheres for voltammetric simultaneous determination of thymine and cytosine.

Pomegranate-like multicore WO2/W nanocrystals wrapped with layers of multiporous carbon were fabricated via carbonization of a copper(II)-organic framework host and a tungsten-based polyoxometalates guest, and subsequent etching off the metallic copper. The WO2/W@C core-shell nanospheres were employed to modify an electrode for the analysis of the DNA bases thymine (T) and cytosine (C) by differential pulse voltammetry. The WO2/W@C exhibited strongly increased oxidation signal of T and C. Under optimized conditions, the enhanced peak current represented excellent analytical performance for determination of T and C. This is attributed to the synergic effects of the porous multicore-shell microstructure and the use of tungsten-based materials with their excellent electrocatalytic activity for T and C, with typical peaks voltages near 1.26 V and 1.44 V. The calibration plots for T and C extend from 1 to 4000 μM and from 1 to 3000 μM, respectively, and both detection limits are 0.2 μM. The method was successfully applied to the determination of T and C in spiked blood and urine samples, and the recoveries are form 97.3 to 105.0%. Graphic abstractCore-shell nanospheres of type WO2/W-carbon were prepared for highly sensitive simultaneous voltammetric determination of thymine and cytosine.