Highly sensitive electrochemical analysis of tunnel structured MnO2 nanoparticle-based sensors on the oxidation of nitrite.

Graphical abstract Highlights • Different tunnel structured MnO 2 nanoparticles were synthesized and characterized. • The first investigation on the effect of tunnel structured MnO 2 on electrochemical oxidation of nitrite. • α-MnO 2 found to be the most reactive structure for electrochemical sensing. Abstract Three MnO 2 nanoparticles with different tunnel structures, α-, β-, and γ-MnO 2 , were synthesized and characterized. We demonstrated and compared their capabilities on the electrochemical oxidation of nitrite, providing a new perspective for MnO 2 or MnO 2 based materials on sensing application. α-MnO 2 exhibited higher electrochemical reactivity than β- or γ-MnO 2 , which was ascribed to its higher conductivity, more exposure to MnO 6 edges, longer average Mn O bond length, and lower Mn average oxidation state(AOS). We hereby reported the first α-MnO 2 nanoparticle-based electrochemical sensor for nitrite sensing. A highly controlled micro-plotter was used to deposit the MnO 2 nanoparticles for the sensor fabrication, providing a micro-pattern of the sensing surface area of MnO 2 and ensuring the reproducibility and sensitivity of this MnO 2 based sensor. Using differential pulse voltammetry, a detection range of 10–800 μM of nitrite was accomplished along with a sensitivity of 17.1 μA μM−1 and a detection limit of 0.5 μM. [ABSTRACT FROM AUTHOR]