Multiwalled carbon nanotubes (MWCNTs) were grafted with poly(4-vinylpyridine) (PV4P) in aqueous solution by in situ free radical polymerization of 4-vinylpyridine. The as-prepared PV4P-g-MWCNTs hybrids can load phosphotungstic acid (PW) on a large scale by electrostatic interaction, which was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The as-prepared PWs/PV4P-g-MWCNTs hybrids were modified onto a carbon glassy electrode. Cyclic voltammograms (CVs) show that the electrochemical behavior of the modified electrode follows a four-one-electron surface-confined process of Keggin-type PWs. The modified electrode can be used as a nitrite sensor. The comparison of CVs shows that the response current of nitrite reduction at the electrode modified with PWs/PV4P-g-MWCNTs hybrids is 15 times higher than that of PWs/MWCNTs hybrids in a control experiment at 0.65V (vs. AgCl). The amperometric i-t curve for the electrode modified with PWs/PV4P-g-MWCNTs hybrids exhibits a linear concentration of NO2-ranged from 1.2 to 17.5 mu M with a detection limit of 0.2 mu M. (C) 2011 Elsevier Ltd. All rights reserved.