High performance of nitrite electrochemical sensing based on Au-poly(thionine)-tin oxide/graphene nanosheets nanocomposites

A novel non-enzymatic nitrite (NO₂⁻) electrochemical sensor was fabricated based on Au-poly(thionine) and tin oxide/graphene nanosheets (Au-PTH/SGN) nanocomposites. The morphology, composition and structure of the nanocomposites were characterized by Transmission electron microscopy, Energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. And the results indicated that homogeneous Au NPs with a size of approximate 80 nm and network nanostructure of PTH were attached on the surface of SGN nanomaterials. It had been also verified to satisfactory electrochemical results. The linear range of the proposed sensor was five orders of magnitude wide with the range of 0.2–127.7 (R² = 0.9991) and 127.7–2800 (R² = 0.9983) μmol L⁻¹, the detection limit was determined to be 0.06 μmol L⁻¹ (S/N＝3) and the sensitivity were 61.92 and 43.19 μA (mmol L⁻¹)⁻¹ cm⁻², respectively. Compared with the similar type of NO₂⁻ sensors previously reported, the linear range was expanded by at least an order of magnitude and the detection limit was kept at the same level as the lowest. Furthermore, the constructed Au-PTH/SGN/GCE displayed fast response, excellent stability, reproducibility, and high anti-interference ability for NO₂⁻ detection. Moreover, the as-proposed electrode was successfully applied for detecting NO₂⁻ in tap water and sewage samples with recoveries ranging from 97.3% to 103.0%97.3%-103.0% and 98.7–102.6%, respectively. The present work is expected to provide a useful route and reference for designing novel high performance electrochemical sensors and broaden the applications of sensors.