High performance simultaneous detection of β-nicotinamide adenine dinucleotide and l-tryptophan in human serum based on a novel nanocomposite of ferroferric oxide-functionalized polyoxometalates

Developing a high-efficient and low-cost nanocomposite, featured by abundant active sites with excellent transfer ability for electrons and high conductivity, for the simultaneous detection of biomolecules belonging to different systems is critically important and challenged. Herein, a nanocomposite composed of ferroferric oxide nanoparticles (Fe 3 O 4 ) functionalized polyoxometalates (H 6 PMo 9 V 3 O 40 ·nH 2 O) was synthesized, using one-step hydrothermal doped method. It exhibited high electrocatalytic activity for oxidation of β-nicotinamide adenine dinucleotide (NADH) and l -tryptophan ( l -trp) with well separated signals (Δ =180 mV) between them coming from the combination of PMoV and Fe 3 O 4 . The PMoV@Fe 3 O 4 /GCE-based sensor exhibited outstanding sensing capability for NADH and l -trp simultaneously with low detection limit of 53 nM and 17 nM, respectively, and excellent selectivity over various possible interfering species, which originated from the synergistic effect of PMoV and Fe 3 O 4 . Moreover, the practical application potential of the PMoV@Fe 3 O 4 sensor was successfully demonstrated by determining NADH and l -trp in real samples.