Electrochemical detection of nitrite using urchin-like palladium nanostructures on carbon nanotube thin film electrodes

In this article, urchin-like palladium (Pd) nanostructures were electrochemically deposited onto pre-patterned single-walled carbon nanotube (SWCNT) thin films. X-ray photoelectron spectroscopy and X-ray diffraction techniques were used to characterize the properties of Pd nanostructures on SWCNT thin films. The spherical Pd particles and urchin-like Pd particles were synthesized at −0.5 V and +0.1 V, respectively. Scanning electron microscope images indicated that the diameters of spherical Pd particles and urchin-like Pd particles were in the range of 50–100 nm and 300–400 nm, respectively. Cyclic voltammetry was applied to investigate the urchin-like Pd/SWCNT electrode with nitrite oxidation. Results showed that the current response of urchin-like Pd/SWCNT was 1.5 times greater than that of spherical Pd/SWCNT electrodes. The effects of precursor concentration, accumulated charges, pattern size on the morphology of urchin-like Pd structures were also investigated. The urchin-like Pd NPs/SWCNT electrode displayed a suitable detection limit of 0.25 μM (S/N = 3) under the controlled condition (de-oxygenated buffer solution at pH 4.0) and two linear ranges with respect to nitrite concentration: one from 2 μM to 238 μM (R2 = 0.995) and the other from 283 μM to 1230 μM (R2 = 0.998). The corresponding sensitivities were 417 μA mM−1 cm−2 and 192 μA mM−1 cm−2, respectively. The presence of K+, Na+, Cl−, PO43−, NH4+, CH3COO−, Zn2+, Mg2+, Ca2+, Cd2+, CO32−, NO3−, and SO42− showed a negligible effect on the current response of nitrite determination, suggesting that developed sensors have a suitable degree of tolerance to common ions that can cause interference.