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

Three MnO2 nanoparticles with different tunnel structures, alpha-, beta-, and gamma-MnO2, were synthesized and characterized. We demonstrated and compared their capabilities on the electrochemical oxidation of nitrite, providing a new perspective for MnO2 or MnO2 based materials on sensing application. alpha-MnO2 exhibited higher electrochemical reactivity than beta- or gamma-MnO2, which was ascribed to its higher conductivity, more exposure to MnO6 edges, longer average Mn-O bond length, and lower Mn average oxidation state(AOS). We hereby reported the first alpha-MnO2 nanoparticle-based electrochemical sensor for nitrite sensing. A highly controlled micro-plotter was used to deposit the MnO2 nanoparticles for the sensor fabrication, providing a micro-pattern of the sensing surface area of MnO2 and ensuring the reproducibility and sensitivity of this MnO2 based sensor. Using differential pulse voltammetry, a detection range of 10-800 mu M of nitrite was accomplished along with a sensitivity of 17.1 mu A mu M-1 and a detection limit of 0.5 mu M.